Article

Infrared Spectroscopy of Aqueous Carboxylic Acids: Comparison between Different Acids and Their Salts

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Abstract

The attenuated total reflection-infrared (ATR-IR) spectra in the 4800-700 cm -1 range of nine carboxylic acids and their sodium salts in aqueous solutions are obtained and analyzed. Overall, 22 species are studied. Six IR titrations are made with five different acids: acetic acid, malic acid, betaine, glycine, and N,N-((butyloxy)propyl) amino diacetic acid (BOPA). From the spectra of these titrations, the spectra of four types of water (acidic, basic, saline, and pure water) are subtracted, giving spectra with flat baselines without any artificial adjustment. Factor analysis (FA) made on the water-subtracted spectra yield the spectra of the principal species, and their abundances. Titration curves obtained from these precisely fit the theoretical curves and the pK a values in the literature. The remaining water bands that are not subtracted are assigned to water solute close-bound situations. The hydration number varied from 5 to 1, with an average of almost 2 per carboxyl carbonyl group. The IR CO band positions ((16 cm -1) are assigned to the different species: 1723 and 1257 cm -1 for the un-ionized acid double and single bonds; 1579 cm -1 for CO 2 -asymmetric stretch; 1406 cm -1 for CO 2 -symmetric stretch; and 1094 cm -1 for noncarboxylic ethoxy groups. The OH absorption covers the full region, from 3700 to 1700 cm -1 , in four bands that are ∼220 cm -1 wide. The near-3400 cm -1 band is assigned to solvated water, alcoholic OH, and NH groups, because these are hydrogen-bonded groups. The 3000 and 2600 cm -1 bands are assigned to the carboxyl OH groups that are hydrogen-bonded to other carboxyl groups in the pure acrylic species or to water in the aqueous solutions cases. The 2100 cm -1 band is assigned to a combination band that involves the far-IR absorption. The absorption from 3700 to 1700 cm -1 , which is sometimes called the "continuous absorption", cannot be attributed to the hydronium ion (H 3 O +), because the acids are not ionized; rather, it results from the strong hydrogen bonds between water and the carboxylic acids.

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... [207] 1689 C=O str. vib. of R-COOH [208] 1068 str. vib. of PA [209] IIa band [cm -1 ] vibration 3200 N-H asym. ...
... 1689/1530 C=O str. vib. of R-COOH [208] 1068 str. vib. of PA ...
... 3380 O-H str. vib. on R-COOH [208] 1689 C=O str. vib. of R-COOH 1068/1035 str. ...
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The universal and simple approach for region-selective deposition of variable metal oxide core-shell nanomaterials (NMs) as a layer-by-layer assembly is demonstrated within this research work. The aluminium oxide (AlOx) nanoparticles (NPs), iron(III) oxide (Fe2O3) NPs, titanium dioxide (TiO2) NPs and nanorods (NRs) are functionalized by 6-phosphonohexanoic acid (PHA) and aminomethylphosphonic acid (AMPA) molecules resulting into metal oxide inorganic-organic core-shell NMs. Additionally, the substrate is pre-patterned with self-assembled monolayer (SAM) based on AMPA and semi-fluorinated phosphonic acid (PA) molecules representing the primary amine (R-NH2) and non-polar semi-fluorinated terminated groups respectively. As a result, the deposition of functional core-shell NMs is alternatively performed with controlled multilayer thickness, precise region-selectivity and full order control of each layer on pre-patterned substrate surface. The stacking of NMs layer-by-layer between themselves on pre-patterned AMPA SAM substrate surface is performed with resulted secondary amide binding (SAB) from covalently reacted -NH2 and -COOH terminated groups available on substrate (R-NH2) and functionalized NMs (R-COOH and R-NH2) respectively. In order to form SAB, the chemical reaction is supported by amide coupling agents. Afterwards, the semi-fluorinated PA is used to prevent the undesired adsorption of NMs on substrate after deposition on AMPA SAM. As a result, the defined pattern of NMs is created in μm scale. The controlled deposition of functional AlOx NPs as a 1st core-shell layer is successfully expanded into three-dimensional nanostructure. This nanostructure is composed of multiple-assembling of functional TiO2 NRs and alternatively Fe2O3 NPs as a 2nd core-shell layer. The functional TiO2 NPs as a 3rd core-shell layer are applied. The termination of nanostructural fabrication is achieved by functionalization of latter deposited core-shell TiO2 NPs by 1-aminopyrene molecules resulting into inorganic-organic hybrid formation. The UV-light excitation of manufactured nanostructure under 365 nm demonstrates region-selective fluorescence emission. The deposition is characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and total internal reflection fluorescence microscope (TIRFM). The significant versatility of stacked metal oxide core-shell NMs via amide coupling method represents the excellent and efficient applicability in manufacture of hybrid inorganic-organic nanostructure with favorable photo-thermal-electrical-mechanical properties for organic electronic fields.
... This product showed a strong absorption peak at about 1720 cm − 1 . The region comprising 1700 -1780 cm − 1 corresponds to carbonyl stretch (ν(C = O)) in a carboxyl functional group and has been extensively linked to the presence of undissociated forms of organic acids [31]. When this region is present at lower wavenumbers (1700 -1720 cm − 1 ), carbonyl groups are considered to be involved in hydrogen bonds. ...
... Instead, a peak in the region 1550 -1620 cm − 1 appeared. In this case, the peak at about 1565 cm − 1 is assigned to the asymmetric stretch of the carboxylate group (ν as (COO − )) and hence attributed to the presence of dissociated acid molecules [31]. A common peak between the two solutions could be found at about 1650 cm − 1 and is related to the bending of water molecules in the sample (δ (H − O − H)). ...
Article
This work studies reactive liquid-liquid extraction of 3-hydroxypropionic acid (3-HP) from aqueous solutions using a biocompatible organic phase consisting in N,N-didodecylmethylamine (DDMA) (20% v/v) diluted in 1-dodecanol (40% v/v) and dodecane (40% v/v). The objective was to propose an equilibrium model based on the law of mass action accounting for the main phenomena occurring in the system. A set of equilibrium extraction experiments was performed in the initial acid concentration range 0.0028 – 1 mol L⁻¹ in order to determine the extraction yield, equilibrium pH and to collect infrared spectra of the loaded organic phases. FT-IR spectra allowed to identify and elucidate the main mechanisms of acid-amine interaction, which were taken into account in the model. The formation of 1:1 acid-amine stoichiometry complex through ion-pairing was determined as the dominant mechanism in all the concentration range. For initial acid concentrations above 0.11 mol L⁻¹, the formation of 2:1 acid-amine complexes through H-bonding of acid molecules with 1:1 complexes was also observed and determined to be almost as important as ion-pair formation at 1 mol L⁻¹. The presence of impurities in the organic phase was taken into account by introducing a side reaction essential to represent low extraction yields and high equilibrium pH values observed at low initial acid concentrations (< 0.02 mol L⁻¹). A global sensitivity analysis of the model’s parameters pointed out three concentration regions based on the relative contribution of each phenomenon: (i) for initial acid concentrations below 0.02 mol L⁻¹, the main phenomena are 1:1 ion-pair formation and the side reaction; (ii) between 0.02 mol L⁻¹ and 0.11 mol L⁻¹, mainly 1:1 ion-pair formation; and (iii), for concentrations above 0.11 mol L⁻¹ both considered complexation reactions i.e., 1:1 ion-pair formation and 2:1 H-bonding. The proposed model allowed thus to evaluate the relative importance of the phenomena occurring in the system in all the studied acid concentration range.
... Besides lipids, vibrations of functional groups bound in polysaccharides, proteins and triterpene compounds may be detected in the considered interval (Meenu and Xu, 2019;Saif et al., 2021). The majority of absorption at 1430 cm −1 was probably caused by C-O-H bending in polysaccharides (Song et al., 2015;Meenu and Xu, 2019), but some contributions from the COO − group in carboxylic acids cannot be ruled out (Max and Chapados, 2004;Stuart, 2004). ...
... Both peaks are within the amide II interval, where IR absorption is caused by the combination of N-H bending and C-N stretching vibrations. In addition, the band around 1558 cm −1 was also associated with asymmetric stretching of the COO − group of amino acids (Barth, 2000(Barth, , 2007, carboxylic acids and their salts (Max and Chapados, 2004). This suggests that carboxyl groups can effectively contribute to Ni adsorption. ...
... The FT-IR spectrum of the PPC/25ED sample demonstrated that the cleaning process was effective in removing free EDTAD (Fig. 2c). The peaks for the ring-opened EDTAD (free EDTAD) are located at 1580 and 1400 cm −1 and are assigned to the stretching (asymmetric and symmetric, respectively) of the C=O from the carboxylate (-COO − ), and the 1326 cm -1 band is assigned to the stretching (C-O) of the tetrasodium EDTA (-CH 2 (COO) − ), which is the main product in the free EDTAD 34,52,53 . The band at 1720 cm −1 in PPC/25ED before cleaning, assigned to the stretching of the C=O in the -COOH group [52][53][54][55] , was also present in PPC/25ED and absent in PPC/ Ref. ...
... The peaks for the ring-opened EDTAD (free EDTAD) are located at 1580 and 1400 cm −1 and are assigned to the stretching (asymmetric and symmetric, respectively) of the C=O from the carboxylate (-COO − ), and the 1326 cm -1 band is assigned to the stretching (C-O) of the tetrasodium EDTA (-CH 2 (COO) − ), which is the main product in the free EDTAD 34,52,53 . The band at 1720 cm −1 in PPC/25ED before cleaning, assigned to the stretching of the C=O in the -COOH group [52][53][54][55] , was also present in PPC/25ED and absent in PPC/ Ref. The peaks at 1580 and 1400 cm −1 were also more intense in PPC/25ED compared to PPC/Ref, suggesting that the EDTAD acylation of the PPC increased the carboxylic acid/carboxylate content of the protein. ...
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Superabsorbent polymers (SAP) are a central component of hygiene and medical products requiring high liquid swelling, but these SAP are commonly derived from petroleum resources. Here, we show that sustainable and biodegradable SAP can be produced by acylation of the agricultural potato protein side-stream (PPC) with a non-toxic dianhydride (EDTAD). Treatment of the PPC yields a material with a water swelling capacity of ca. 2400%, which is ten times greater than the untreated PPC. Acylation was also performed on waste potato fruit juice (PFJ), i.e. before the industrial treatment to precipitate the PPC. The use of PFJ for the acylation implies a saving of 320 000 tons as CO2 in greenhouse gas emissions per year by avoiding the industrial drying of the PFJ to obtain the PPC. The acylated PPC shows biodegradation and resistance to mould growth. The possibilities to produce a biodegradable SAP from the PPC allows for future fabrication of environment-friendly and disposable daily-care products, e.g. diapers and sanitary pads. Superabsorbent materials can absorb many times their weight in water, but are commonly derived from petroleum. Here, acylation of coagulated potato protein concentrate or soluble potato protein fruit juice yields an effective, mould-resistant, and biodegradable superabsorbent polymer.
... Besides lipids, vibrations of functional groups bound in polysaccharides, proteins and triterpene compounds may be detected in the considered interval (Meenu and Xu, 2019;Saif et al., 2021). The majority of absorption at 1430 cm −1 was probably caused by C-O-H bending in polysaccharides (Song et al., 2015;Meenu and Xu, 2019), but some contributions from the COO − group in carboxylic acids cannot be ruled out (Max and Chapados, 2004;Stuart, 2004). ...
... Both peaks are within the amide II interval, where IR absorption is caused by the combination of N-H bending and C-N stretching vibrations. In addition, the band around 1558 cm −1 was also associated with asymmetric stretching of the COO − group of amino acids (Barth, 2000(Barth, , 2007, carboxylic acids and their salts (Max and Chapados, 2004). This suggests that carboxyl groups can effectively contribute to Ni adsorption. ...
Article
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Despite the negative impact on the environment, incineration is one of the most commonly used methods for dealing with waste. Besides emissions, the production of ash, which usually shows several negative properties, such as a higher content of hazardous elements or strongly alkaline pH, is problematic from an environmental viewpoint as well. The subject of our paper was the assessment of biosorption of Ni from ash material by a microbial consortium of Chlorella sp. and Aspergillus niger. The solid substrate represented a fraction of particles of size <0.63 mm with a Ni content of 417 mg kg −1. We used a biomass consisting of two different organisms as the sorbent: a non-living algae culture of Chlorella sp. (an autotrophic organism) and the microscopic filamentous fungus A. niger (a heterotrophic organism) in the form of pellets. The experiments were conducted under static conditions as well as with the use of shaker (170 rpm) with different modifications: solid substrate, Chlorella sp. and pellets of A. niger; solid substrate and pellets of A. niger. The humidity-temperature conditions were also changed. Sorption took place under dry and also wet conditions (with distilled water in a volume of 30-50 ml), partially under laboratory conditions at a temperature of 25 • C as well as in the exterior. The determination of the Ni content was done using inductively coupled plasma optical emission spectrometry (ICP-OES). The removal of Ni ranged from 13.61% efficiency (Chlorella sp., A. niger with the addition of 30 ml of distilled water, outdoors under static conditions after 48 h of the experiment) to 46.28% (Chlorella sp., A. niger with the addition of 30 ml of distilled water, on a shaker under laboratory conditions after 48 h of the experiment). For the purpose of analyzing the representation of functional groups in the microbial biomass and studying their interaction with the ash material, we used Fourier-transform infrared Frontiers in Microbiology | www.frontiersin.org 1 December 2021 | Volume 12 | Article 792987 Šimonovičová et al. Treatment of Hazardous Ash Waste (FTIR) spectroscopy. We observed that the amount of Ni adsorbed positively correlates with absorbance in the spectral bands where we detect the vibrations of several organic functional groups. These groups include hydroxyl, aliphatic, carbonyl, carboxyl and amide structural units. The observed correlations indicate that, aside from polar and negatively charged groups, aliphatic or aromatic structures may also be involved in sorption processes due to electrostatic attraction. The correlation between absorbance and the Ni content reached a maximum in amide II band (r = 0.9; P < 0.001), where vibrations of the C=O, C-N, and N-H groups are detected. The presented results suggest that the simultaneous use of both microorganisms in biosorption represents an effective method for reducing Ni content in a solid substrate, which may be useful as a partial process for waste disposal.
... To elucidate the nature of interactions between the phases forming the eutectic, DPS and SEBA, a detailed infrared analysis was performed (Fig. 8a). Pronounced differences can be noticed associated with the SEBA vibrational groups (Max and Chapados, 2004;Sailakshmi et al., 2012). The broad band at 1687 cm − 1 of pure SEBA, indicative of some dimer presence, is slightly shifted to higher wavenumbers in the eutectic (1694 cm − 1 ), this band is also narrower in comparison to that of pure SEBA. ...
Article
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The physiochemical properties of acidic or basic active pharmaceutical ingredients (APIs) can be optimised by forming salts with different counterions. The aim of this work was to synthesise a novel salt of propranolol (PRO) using sebacic acid (SEBA) as the counterion and to gain mechanistic understanding of not only the salt formation, but also its eutectic phase formation with SEBA. Thermal analysis showed a solid-state reaction occurring between PRO and SEBA leading to the formation of dipropranolol sebacate (DPS) melting at app. 170 °C and the eutectic composed of DPS and SEBA melting at app. 103 °C, comprising 0.33 mole fraction of PRO as determined by the Tammann plot. X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR) confirmed the identity of the new multicomponent phases of PRO. DPS can be conveniently obtained by heat-induced crystallisation, grinding and conventional solvent crystallisation. Detailed analysis by FTIR revealed H-bond interactions between DPS and SEBA at the inter-phase in the eutectic. Bravais, Friedel, Donnay and Harker crystal morphology coupled with full interaction maps analysis allowed to understand further the nature of interactions which led to formation of the eutectic phase. This work contributes to furthering research on multicomponent pharmaceutical systems to harness their full potential.
... As observed in Fig. 5a3, it was observed within the peaks at 3401 cm -1 , 2961 cm -1 , and 1649 cm -1 associated with the stretching vibrations of the H bond, C-H and N-H of amide I, II, and III. The peaks at 1401 cm -1 and 1082 cm -1 are attributed to the stretching vibrations of the C-C and C-N groups that have revealed more of a gelatin concentration [81] and low concentrations of acetic acid [82]. Figure 5a4 displays the FTIR spectrum of the MENM. ...
Article
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In this study, a novel hybrid multilayered electrospun nanocomposite membrane (MENM) was developed for activated wound dressing applications. An established electrospinning process was employed to fabricate a tri-layer nanocomposite membrane where the lower layer was composed of chitosan (CS)/polyvinyl alcohol (PVA) and fibrin (having regeneration of tissues and bleeding resistance properties), both of which are directly in contact with the burn wound (BW) skin, and a middle layer of PVA/sodium alginate (SA) (having antibacterial properties). The top layer consisted of gelatin (super hydrophilic properties). The MENM morphology was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) which confirmed the presence of the elemental and chemical structures of MENM. The MENM was identified by Fourier transform infrared spectroscopy (FTIR) with a maximum drug release which was ascended within 10-h duration. X-ray diffraction (XRD) showed long-term absorbency due to the presence of more amorphous and less crystallinity percentages in the MENM. The nanocomposites' thermal stability was also observed via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The developed MENM has shown excellent antibacterial activity with a zone of inhibition of 18.7 ± 0.9 mm, 18.9 ± 0.9 mm, 20.0 ± 1 mm and 19.3 ± 0.9 mm, respectively, against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. The high water absorbant properties of MENM indicate that the produced membranes could absorb the maximum exudate from wounded skin within the shortest time and assist in healing the wound quickly. The produced MENMs could be potential wound dressing materials in the future. Graphical abstract
... Furthermore, the absorption bands around at 1700 cm − 1 in the bare hydrogel are indicative of the presence of carbonyl groups which are frequently observed around 1680-1820 cm − 1 . Meanwhile, absorption bands at 1648, 1612 cm − 1 for bare hydrogels indicate C--C stretch and an asymmetric stretch of COO − respectively [68]. Magnetic hydrogel in comparison with bare hydrogel, shows a specific absorption band at 564 cm − 1 , displays stretching vibrations of Fe 3+ -O 2− in the tetrahedral sites which proves that the cobalt ferrite nanoparticles are dispersed among this structure [69]. ...
Article
Magnetism is a physical stimulus that can induce and regulate several biological responses in cells and would be promising for application in various fields of biomedical, especially tissue engineering. Magnetic properties can be provided by the construction of magnetic scaffolding or the presence of an external magnetic field. The objectives of this study were to develop a new magnetic hydrogel composite for bone tissue engineering applications by applying the cobalt ferrite nanoparticles (CoFe2O4) as magnetic agents in the structure of polyacrylic acid hydrogel. The composite hydrogel containing 5% (w/w) of nanoparticles was selected as optimal structure after comparing the results of vibrating sample magnetometer (VSM), compressive modulus, swelling, and cytotoxicity tests for all magnetic composite groups. We then investigated the effect of selected magnetic hydrogel composite, accompanied by an external static magnetic field (SMF), on the cell cytotoxicity and proliferation, osteogenic differentiation, and mineral synthesis of human dental pulp stem cells (hDPSCs), which were seeded on the magnetic hydrogel. The results show that the synergistic effect between the magnetic scaffold and the external magnetic field on the cells, increased the alkaline phosphatase activity by about 3-fold on day 14 and the synthesis of minerals was also much higher compared to the control groups. Moreover, The results also show that the effect of magnetic scaffold along with external magnetic field on the cells osteogenic differentiation was similar to the effect of osteogenic inductive culture medium on control groups. Our findings verify that our synthesized magnetic hydrogel composite would be the potential to support osteogenic differentiation of dental pulp stem cells, and combinatory application of magnetic scaffold and external magnetic field can be a promising alternative instead of chemical stimulants for cells osteogenic differentiation.
... sequestration of N-NH + 4 by Bio-MPs polymers. According to our FTIR results (Fig. S4), the Bio-MPs used in current research showed a strong peak at wavelength 1711.44 cm − 1 , this is within the characteristic peak range of carboxylic acids (-COOH) (Max and Chapados, 2004;Zain et al., 2017), indicated that our Bio-MPs also contained negative charge functional groups of -COOH. An incubation experiment conducted by Chen et al. (2019) observed a significant decrease in N-NH + 4 when soils were amended with 2% PLA-MPs. ...
Article
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Agricultural microplastic pollution has become a growing concern. Unfortunately, the impacts of microplastics (MPs) on agricultural soil carbon and nitrogen dynamics have not been sufficiently reported. In an attempt to remedy this, we conducted a 105-day out-door mesocosm experiment in a soil-plant system using sandy soils amended with two types of MPs, low-density polyethylene (LDPE-MPs) and biodegradable (Bio-MPs), at concentrations of 0.0% (control), 0.5%, 1.0%, 1.5%, 2.0% and 2.5% (w/w, weight ratio of microplastics to air-dry soil). Soil organic matter (SOM), dissolved organic carbon (DOC), permanganate oxidizable carbon (POXC), available nitrogen (AN) of N-NH4+ and N-NO3−, and dissolved organic nitrogen (DON) were measured on day 46 (D46) and 105 (D105) of the experiment. SOM was also measured after microplastics were mixed into soils (D0). For LDPE-MPs treatments, SOM on D0, D46 and D105 showed no significant differences, while for Bio-MPs treatments, SOM significantly (p < 0.05) decreased from D0 to D46. Compared to the control, soil POXC was significantly (p = 0.001) lowered by 0.5%, 1.0% and 2.5% LDPE-MPs and ≥1.0% Bio-MPs on 105d. LDPE-MPs showed no significant effects on soil DOC and nitrogen cycling. 2.0% and 2.5% Bio-MPs showed significantly higher (p < 0.001) DOC and DON (D46 and D105) and ≥1.5% Bio-MPs showed significantly lower (p = 0.02) AN (D46). Overall, Bio-MPs exerted stronger effects on the dynamics of soil carbon and nitrogen cycling. In conclusion, microplastics might pose serious threats to agroecosystems and further research is needed.
... The horizontal axis represents the wavenumber, and the vertical axis represents the absorbance. The peak at 1,733 cm −1 corresponds to the peak of the carbonyl group, [39,40] which is similar to the peak at 1,738 cm −1 , as discussed in a previous study. [21] On magnification, this peak rises broadly in the range of 1,730-1,750 cm −1 . ...
Article
To improve the long-term reliability of adhesively bonded joints, it is important to evaluate the degradation of adhesives on exposure to high-temperature and high-humidity environments. Further, it is important to evaluate the change in material properties, such as mechanical residual strength. Although Fourier transform infrared (FTIR) spectroscopy is widely used to investigate the chemical structures in materials, it is difficult to identify the cause of degradation due to the complex composition of adhesives. This study aimed to develop a simple method for extracting the features related to degradation using FTIR spectroscopy, and to estimate the mechanical residual strength. The surface of the adhesives after immersion exposure to water at a high temperature was analysed using FTIR spectroscopy, and their mechanical strength was measured. The correspondence between them was demonstrated using machine learning. Several linear regression methods were used and compared; the model based on Lasso regression was determined to be the most suitable for extracting features and estimating residual strength. Furthermore, it was indicated that the developed model could be used to identify areas where there is a loss of strength.
... In the spectrum of the extract, the slightly shifted and more intense peak at 1727.91 cm −1 provides the indication that the components of the extract interact with the NaDES and cause shifting of the COOabsorption due to hydrogen bonding. The characteristic peaks at the 1573.63 cm −1 and 1407.28 cm −1 for the CO 2 asymmetric and symmetric stretch [65] of the betaine molecule are shifted at 1629.55 cm −1 and 1394.28 cm −1 respectively, indicating the interaction of NaDES with the extracted components. Similarly, a slighter shift is also observed from 1126.22 cm −1 (NaDES spectrum) to 1130.08 cm −1 (extract spectrum) probably indicates the interaction of the C-O group of lactic acid with extracted compounds. ...
Article
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The extraction of valuable phytochemicals from natural sources is an important and constantly evolving research area. Zingiber officinale Roscoe (ginger) contains high amounts of bioactive phytochemicals, which are desirable due to their significant properties. In this work, the ability of different natural deep eutectic solvents (NaDESs) to serve as green solvents for the preparation of high added value extracts from ginger is explored, in combination with ultrasound assisted extraction. The method was optimized by applying a response surface methodology using the NaDES Bet/La/W (1:2:2.5). Three independent variables, namely the extraction time, ultrasound power and NaDES-to-dry-ginger ratio, were investigated by employing a 17-run three-level Box–Behnken Design (BBD) in order to study the correlation between the extraction conditions and the quality of the obtained extracts. The optimum conditions (in order to achieve simultaneously maximum total phenolic content and antioxidant activity), were found to be 23.8 min extraction time, 60 Watt and NaDES/ginger 25:1 w/w. In the optimum conditions the DPPH radical scavenging ability of the extracts was found to reach IC50 = 18.16 mg/mL after 120 min, whereas the TPC was 20.10 ± 0.26 mg GAE/g of dry ginger. The green methodology was also compared with the extraction using conventional solvents. All the obtained extracts were evaluated for their antioxidant activity and their total phenolic content, while the extract derived by the optimum extraction conditions was further investigated for its ability to bind to calf thymus DNA (ctDNA).
... Overlapped UV-Vis spectra for the reference and for the presence of each interfering metallic salt: CuCl 2 , FeCl 3 , FeSO 4 , KCl, NaCl, ZnCl 2 , Pb(NO 3 ) 2 , MgSO 4 , CaCl 2 . References [37][38][39][40][41][42][43][44][45][46][47] Funding: This research was funded by UEFISCDI, project number PN-III-P2-2.1-PED-2019-0487, 528PED/2020, CeraPor-Corr -"Hybrid ceramics/porphyrins, deposited by pulsed laser deposition as single and sandwich layers for corrosion inhibition of steels in acid environment" and partially by Romanian Academy through Programme 3/2022 from the Institute of Chemistry "Coriolan Dragulescu". ...
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Significant tasks of the presented research are the development of multifunctional materials capable both to detect/capture carbon dioxide and to monitor toxic metal ions from waters, thus contributing to maintaining a sustainable and clean environment. The purpose of this work was to synthesize, characterize (NMR, FT-IR, UV-Vis, Fluorescence, AFM) and exploit the optical and emission properties of a carboxyl-substituted A3B porphyrin, 5-(4-carboxy-phenyl)-10,15,20-tris-(4-methyl-phenyl)–porphyrin, and based on it, to develop novel composite material able to adsorb carbon dioxide. This porphyrin-k-carrageenan composite material can capture CO2 in ambient conditions with a performance of 6.97 mmol/1 g adsorbent. Another aim of our research was to extend this porphyrin- k-carrageenan material’s functionality toward Mn2+ detection from polluted waters and from medical samples, relying on its synergistic partnership with gold nanoparticles (AuNPs). The plasmonic porphyrin-k-carrageenan-AuNPs material detected Mn2+ in the range of concentration of 4.56 × 10−5 M to 9.39 × 10−5 M (5–11 mg/L), which can be useful for monitoring health of humans exposed to polluted water sources or those who ingested high dietary manganese.
... The peak at 1642 cm − 1 is caused by the stretching vibration of -COOon the main chain of PCE molecules [18]. The peak at 1723 cm − 1 is assigned to the strong hydrogen bonds between water and the -COOgroups [19]. However, it does not appear in IA-PCE due to the indirectly bonded -COOwith its main chains. ...
Article
Polycarboxylate ether (PCE) superplasticizers with three different anchoring groups were synthesized by copolymerizing allyl polyoxyethylene ether with trans-butadiene (FA), cis-butenedioic anhydride (MAH), and itaconic acid (IA), respectively. The interactions between PCEs and cementitious materials were revealed by adsorption properties, Ca²⁺ binding capacity of PCE, and zeta-potential of paste. The effects of anchoring groups in PCEs on the flowability and rheological properties of cementitious pastes were studied. Results indicated that the density and local configuration of –COO– groups in PCEs significantly affect their adsorption behavior and dispersibility in cementitious pastes. Most of the –COO– groups are isolated on the backbone of FA-PCE, while for the MAH-PCE, only pairs of –COO– groups present the backbone. All the –COO– groups directly connect to the main chains in FA- and MAH- PCEs, whereas half of the –COO– groups in IA-PCE indirectly connect to the main chains through hydrophobic methylene, which has a potential to curl and reduce its “accessible” –COO– groups. FA-PCE with a large specific charge density exhibit excellent flowability and rheological properties in cementitious pastes.
... However, the O-H stretching band of the carboxylic acid was not observed. This is because the carboxyl OH groups are hydrogen-bonded to other carboxyl groups in the rejuvenator, causing the O-H stretching band to move to around 3000 cm − 1 and be covered by the bands of -CH 2 -groups (Max and Chapados, 2004). In the 1 H NMR spectrum in Fig. 14b, the signal at 11.50 ppm is assigned to -COOH group, which further proves the presence of fatty acids in the rejuvenator. ...
Article
Using a rejuvenator to increase the dose of reclaimed asphalt pavement (RAP) materials in asphalt mixtures is a sustainable practice in the pavement industry. However, the mechanism by which the rejuvenator restores the performance of aged asphalt in the RAP binder remains an open question: research approaches are inadequate, and the details of asphalt aging are not clear. Here, we first revealed the aging mechanism of asphalt and obtained realistic structures of aged asphalt molecules by means of first-principles molecular simulations that modeled the chemical reaction between asphalt and oxygen. Subsequently, through classical modeling approaches that examine the solubility behaviors of asphalt molecules in n-heptane with and without a rejuvenator, we demonstrated the serious agglomeration of aged molecules, the transformation of aged resins into asphaltenes, and the restorative effect of the rejuvenator. To explore the driving force behind these findings, we performed density functional theory calculations and wavefunction analyses to determine the strength and nature of intermolecular interactions between asphalt molecules. The results indicated that the electrostatic interaction between aged asphalt molecules increases significantly upon generation of polar groups, and the rejuvenator decreases the electrostatic interaction mainly by eliminating hydrogen bonds, thus reducing molecular agglomeration, but has little effect on the dispersion force. Besides, Hansen solubility parameters were calculated to illustrate the agglomeration in aged asphalt and the restorative effect of the rejuvenator in terms of the “like-dissolves-like” rule. This study bridges the gap between electronic-scale modeling and complex engineering practice related to the aging and rejuvenation of asphalt.
... In the resulting chelate, the hydrogen atoms have been replaced with heavier iron atoms. The absorption band at 1640 cm −1 can be related to the bending vibrations of surface hydroxyl groups and may indicate molecular adsorption without ionisation [14,15]. Content courtesy of Springer Nature, terms of use apply. ...
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The magnetic properties of magnetite nanoparticles (Fe 3 O 4 NPs) strongly depend on their chemical and physical parameters, which can be regulated by a controlled synthesis process. To improve the quality of the obtained nanoparticles, their surface is often modified with organic compounds (from the group of surfactants, sugars, proteins, or organic acid). In this study, we synthesized magnetite nanoparticles with a surface modified with the organic compound DMSA. Then, the nanocrystallites were characterized in terms of structure and morphology. To investigate the role of DMSA and to understand the adsorption mechanism, FTIR measurements were carried out. Using Mössbauer spectroscopy, we investigated temperature-induced changes in the magnetic properties of prepared samples. The spectra were recorded in a wide temperature range (from 4 K to 390 K) for two types of samples: powders and ferrofluids with various concentrations. In the case of powder samples, the superparamagnetic doublet appeared at room temperature. For magnetic suspensions, the spectra were more complicated. They consisted of superposition of asymmetrically broadened sextets and doublets, which was caused by the occurrence of long-range dipole-dipole interactions. These interactions affected the magnetic properties of the material and increased the blocking temperature. Additionally, the magnetic hysteresis and zero field cooling-field cooling (ZFC/FC) curves were measured with the use of a vibrating sample magnetometer.
... The bands between 2855 and 2974 cm − 1 are attributed to the asymmetrical vibration stretching of CH 2 aliphatic group [25,26] suggesting the presence of alkyl chains attributed to fatty acids [26] in the EPS. Finally, the peaks at 2026 and 2157 cm − 1 may be associated to adsorbed CO or more likely to the presence of acetic acid [27,28], which is a product of bacterial metabolism. ...
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316 L coupons were sanitized in hot water vapour inducing iron enrichment in passive films. Coupons were then immersed in a pilot fed-batch fermenter in presence of E. coli. Sanitization causes iron enrichment in passive films. Fermentation causes the growth of biofilm on the SS, constituted by bacteria embedded in an extracellular polymeric substance. During fermentation SS open circuit potential is very negative due to low oxygen concentration on its surface, while the chelating action of siderophores induces chromium enrichment in the passive film. Disinfection in NaClO for 30 min allows removal of biofilm and formation of a protective passive film.
... El paso de obtención de las curvas potenciométricas se decide realizar para esclarecer algunos aspectos importantes sobre la estructura del complejo que se obtiene de la mezcla de los iones citrato, ytrio(III) y circonio(IV). La literatura es ambigua y se presentan un sinfín de posibilidades referentes al tema [60][61][62]. Algunos de los aspectos principales que se desean esclarecer son la participación o no del alcohol terciario del ion citrato en la formación del complejo, cuántos grupos -COO-del ion citrato se enlazan a los diferentes metales y el valor de pH al cual deben ser neutralizadas las diferentes muestras. Con este propósito es que se lleva a cabo la obtención de las curvas potenciométricas de los citratos metálicos por separado y del ácido cítrico. ...
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The oxides of the YSZ family are solid oxygen-conducting electrolytes, strategic in energy saving, as sensors for hydrocarbon combustion processes and in the development of SOFC-type fuel cells. This work is based on the need to obtain nanometric particles of ZrO2(9.5)%Y2O3 at low temperatures in a reaction step, to later study them as solid electrolytes conducting oxygen. To achieve this, it is proposed to implement the citrate-nitrate self-combustion method in a crystallization step controlling the molar ratio between the fuel (ammonium bis(citrate−zirconate(IV)itriate(III)) and the oxidant (co-precipitated ammonium nitrate) that make up the solid-state precursor. Different types of sodium citratezirconate and citrateittriate complexes, mononuclear and binuclear, were prepared for which the metal / ligand ratio was varied from 1:1 to 1:3. The formation of the complexes was monitored by means of acid-base titration curves and the IR spectra of the precipitated metallic citrates; all with the aim of establishing the optimization of the oxide synthesis process. Optimal metallic citrate / nitrate precursors were identified for the application of the SelfCombustion Method in obtaining the nanometric ZrO2(9.5)%Y2O3. The analyses carried out through the FT-IR, DRX, DSC, TG, SEM-EDS and TEM methods revealed that the proposed method allows obtaining the desired phase of the nanoparticulate oxide,ZrO2(9.5)%Y2O3, at less than 400 oC without the need for subsequent treatments.
... After sorption, the carbonyl peaks in PSF decreased and shifted to 1685 cm − 1 but were absent in the PSF-biochar beads, similar to the peaks at 1404 cm − 1 , 1011 cm − 1 , and 833-630 cm − 1 . As shown in Figure 1d, the peaks appeared in all sorbents before sorption at 1404 cm − 1 can be ascribed to the -COO-symmetric stretching (from carboxyl moiety) (Deng et al., 2017;Jia et al., 2000;Max et al., 2004). After mercury sorption, this peak at 1404 cm − 1 was shifted to 1485 cm − 1 (Fig. 1e), which could be due to the involvement of the alpha-beta unsaturated carboxyl moiety that facilitated the complexation process of Hg (II) with the sorbents. ...
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Elevated mercury (Hg) concentrations in water bodies caused by illegal artisanal gold mining in Ghana is a serious health concern given the toxicity of Hg. As an ecofriendly cost-effective solution for removing Hg from these water bodies, we synthesized biochars using palm kernel (PB) and coconut shells (CB), which are dominant biomass wastes in Ghana. The biochars were sulfurized (SPB, SCB) and fabricated into polysulfone-based beads for Hg(II) sorption. The Hg(II) concentration, contact time, sorbent mass, and solution pH were investigated and were found to be influential on the sorption of Hg(II) from aqueous solution. The sulfurized biochars showed a faster Hg(II) removal (within 1h) compared to the pristine biochars. Sorption tests conducted using natural riverine water samples confirmed the potential use of the biochars, with SPB and SCB showing higher efficiencies than pristine PB and CB. The fabricated beads exhibited 70 -90% efficiency in Hg(II) removal from 1.0 mg L⁻¹ Hg solution and the sorption capacity was below 0.1 mg g⁻¹, which we attribute to the mass of biochar used for the beads. The Hg(II) sorption mechanisms of PB and CB from spectroscopic analyses suggest that the biochars synthesized in this study can be used to treat Hg polluted waters and suitable for large-scale applications in natural water bodies.
... Moreover, two vibrations associated with carboxylate (−COO − ) appeared at 1570 and 1400 cm −1 in the sporopollenin shells. 44 The formation of a carboxylate salt is likely due to the de-esterification of pollen pectin during alkali treatment. 35 The carbohydrate fingerprint region (1200−900 cm −1 ) in the sporopollenin shells also showed two new distinct vibrations at 1075 and 970 cm −1 . ...
... The change in chemical shifts of peaks in 1 H NMR spectrum under humidified condition (Fig. 4a) is similar to that under dry condition, suggesting that SO 2 can also interact with NDES-based gel in this case. As for FTIR spectra (Fig. 4b), a new peak located at 2678 cm − 1 , which is attributed to the stretching vibration of O-H on carboxylic group bonded to other carboxyl groups [82], is found after absorbing SO 2 , confirming the generation of the protonated betaine, and it will be discussed in the next section. Overall, these NDES-based gels can be regarded as functionalized materials with multiple sites for facilitated separation of SO 2 . ...
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The researches on capture of SO2 from flue gas using deep eutectic solvents (DESs) are rapidly emerging due to their unique natures, such as high efficiency and simple synthesis. However, to the best of our knowledge, DESs have not been applied to membrane separation of SO2 yet. Herein, we firstly reported novel natural deep eutectic solvent (NDES)-based gels consisting of betaine/glycerol DES (1:2) and 12-hydroxystearic acid (HSA) for selective membrane separation of SO2. Characterization of the prepared gels involving chemical structures, thermal stability and sol-gel transition temperatures were conducted. The corresponding gel membranes were facbricated and their morphology and pressure resisitance were characterized. Gas permeation test shows that the permeability of SO2 reaches 1809 barrers (0.025 bar, 40 °C) in DES+HSA 4% gel, with SO2/N2 and SO2/CO2 selectivities of 624 and 67.8, respectively. FTIR and NMR spectroscopy were used for characterize the facilitated transport of SO2, and the multisite-interaction mechanism was proposed. Surprisingly, the SO2 permeability is found to be significantly enhanced to 15200 barrers without compromise on selectivity under humidified condition. Moreover, the effects of HSA content, SO2 partial pressure and temperature on separation performance were also investigated. Overall, this work offers an illustration of SO2 separation using DES-based gels, offering an alternative strategy for designing novel DES-based membrane materials for flue gas desulfuration.
... Therefore, the new peaks at 1078 and 1031 cm −1 could be attributed to the stretching vibrations of the C-O-and Si-O bonds corresponding to polysaccharides or polysaccharide-like components 35 and silica colloids, respectively. Additionally, in CEM, a peak in the range 2965-3000 cm −1 , corresponding to the O-H of a carboxylic acid, hydrogen bonded to oxygen in water, or other carboxylic groups, was observed 36 . The weak peaks in the 905-830 cm −1 region for both AEMs and CEMs could be ascribed to the binding of iron oxides and their derivatives, which resulted in a mixture of red and yellow foulants 32 . ...
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Reverse electrodialysis (RED) generates electricity from a mixture of seawater and river water. Herein, patterned membranes consisting of ultra-thin pore-filling membranes (16-μm thick) were used to determine whether the RED system operates steadily when using natural underground seawater and sewage effluent and if the membranes become polluted by various foulants. The flat stack performances, comprising flat membranes and woven-type spacers, were compared with those of the pattern stack, comprising patterned membranes with mirror-imaged wavy lines. The pattern stack clearly reduced the pressure drop and maintained the power within 40% of the initial value, and the flat stack significantly increased to 3 bar inside the sewage effluent and decreased the power to 20% of the initial value. Both anion and cation exchange-surface membranes showed organic fouling and scaling, with more significant fouling in the flat stack. The patterned membranes used here provide a powerful solution to reduce fouling inside RED stacks.
... The aromatic t (C-H) appeared as a w, broad-band at 3071 cm À1 (Sharma et al. 1980). The m, band which appeared at 2843 cm À1 may be attributed to t (O-CH 3 ) of the methoxy group (Max and Chapados 2004). The band which assigned at 3202 cm À1 was of t (N-H) of the amide group, while that assigned at 1620 cm À1 was of t (C ¼ O) of the amide group (Al-Assadi 2016). ...
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Purpose: The limitations of the current chemotherapeutics are the main rational to develop and/ or explore new anticancer agents and radiolabeled analogues for cancer early diagnosis. Materials and methods: The newly synthesized p-methoxyphenyl maleanilic acid (MPMA) was prepared, characterized and investigated for its anticancer activity. MPMA screened in-vitro against human hepatocellular carcinoma (HepG-2), human colon carcinoma (HCT-116) and human breast carcinoma (MCF-7) cell lines. Furthermore, the in-vivo screening was performed by radiolabeling of MPMA with technetium-99m (99mTc) and investigating its biological distribution in normal mice and solid tumor models. Moreover, MPMA and its radiolabeled analogue were docked to Y220C and Y220S mutants of p53 (p53Y220C and p53Y220S) in an effort to confirm their affinity to cancer as well as to investigate, virtually, the mechanism of action of MPMA. Results: The results revealed significant potency of MPMA against HepG-2 cell line (IC50 ¼ 56.2 ± 1.5 mg/mL) if compared to HCT-116 (IC50 ¼ 89.9 ± 1.8 mg/mL) and MCF-7 (IC50 ¼ 104 ± 2.7 mg/ mL) cell lines. The radiolabeling yield was optimized to be 90.2 ± 2.1%. The radiolabeled MPMA showed a good localization in the site of solid tumor (15.1 ± 1.6%ID/g) at 2 h post intravenous administration to the tumor bearing mice. Conclusions: Collectively, the findings confirmed the potential anticancer activity of MPMA and the possible use of 99mTc-MPMA for cancer diagnosis and monitoring.
... The ionized form of necbergamotenoic acid B (2 0 ) was also isolated as a yellowish gum. Its HRESIMS spectrum showed the positive ion peak at m/z 289.1403 (calcd for C 15 H 22 O 4 Na, 289.1410, Figure S26), which was the same as that of 2. In the IR spectrum of 2 0 ( Figure S27), the carbonyl group had two bands situated at 1573 and 1426 cm À1 that are typical of ionized groups (RCOO À ) (Max and Chapados, 2004 Figures S30-S33) spectra, the structure of 2 0 was confirmed and all the 1 H and 13 C NMR chemical shifts were assigned as Table 1. The carbon signals of C-11 and C-12 for a,b-unsaturated carboxylic acid group in ionized form (2 0 ) shifted downfield about 5 ppm, which was consistent with the results reported in the literature (Cistola et al., 1982). ...
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Bergamotenes are bicyclo[3.1.1]heptane sesquiterpenes found abundantly in plants and fungi. Known bergamotene derivatives all possess (2S,6S)-bergamotene backbone. In this study, two (+)-α-trans-bergamotene derivatives (1 and 2) with unusual (2R,6R) configuration were isolated and elucidated from marine fungus Nectria sp. HLS206. The first (+)-α-trans-bergamotene synthase NsBERS was characterized using genome mining and heterologous expression-based strategies. Based on homology search, we characterized another (+)-α-trans-bergamotene synthase LsBERS from Lachnellula suecica and an (+)-α-bisabolol synthase BcBOS from Botrytis cinerea. We proposed that the cyclization mechanism of (+)-α-trans-bergamotene involved endo-anti cyclization of left-handed helix farnesyl pyrophosphate by (6R)-bisabolyl cation, which was supported by molecular docking. The biosynthesis-based volatiles (3–6) produced by heterologous fungal expression systems elicited significant electroantennographic responses of Helicoverpa armigera and Spodoptera frugiperda, respectively, suggesting their potential in biocontrol of these pests. This work enriches diversity of sesquiterpenoids and fungal sesquiterpene synthases, providing insight into enzymatic mechanism of formation of enantiomeric sesquiterpenes.
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Herein, we demonstrate the synthesis of Fe3O4 nanoparticles based metal organic framework MIL-53(Al) nanocomposite [Fe3O4 NPs/MIL-53(Al)] (MIL stands for Material of the Institut Lavoisier) via a facile chemical approach. The fabrication method of nanocomposite is based on the in-situ synthesis of MIL-53(Al) on the surface of pre-synthesized Fe3O4 nanoparticles. The structural features of as-synthesised nanocomposite were elucidated by powder X-ray diffraction (PXRD) analysis, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), optical properties, Fourier transform Infra-Red (FTIR) spectroscopy and thermo gravimetric analysis (TGA). The nanocomposite exhibited excellent catalytic performance towards intrinsic peroxide oxidation of o-phenylenediamine (OPD). Fe3O4 NPs/MIL-53(Al) nanocomposite was also used for the colorimetric detection of hydrogen peroxide and exhibited detection limit of 0.8499 μmolL⁻¹. Moreover, the nanocomposite was magnetically separable with commercially available magnet and showed significant catalytic stability after six consecutive cycles.
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Antifouling materials are indispensable in the biomedical field, but their high hydrophilicity and surface free energy provoke contamination on surfaces under atmospheric conditions, thus limiting their applicability in medical devices. This study proposes a new zwitterionic structure, 4-vinylpyridine carboxybetaine (4VPCB), that results in lower surface free energy and increases biological inertness. In the design of 4VPCB, one to three carbon atoms are inserted between the positive charge and negative charge (carbon space length, CSL) of the pyridyl-containing side chain to adjust hydration with water molecules. The pyridine in the 4VPCB structure provides the hydrophobicity of the zwitterionic functional group, and thus it can have a lower free energy in the gas phase but maintain higher hydrophilicity in the liquid phase environment. Surface plasmon resonance and confocal microscopy were used to analyze the antiprotein adsorption and anti-blood cell adhesion properties of the P4VPCB brush surface. The results showed that the CSL in the P4VPCB structure affected the biological inertness of the surface. The protein adsorption on the surface of P4VPCB2 (CSL= 2) is lower than that on the surfaces of P4VPCB1 (CSL = 1) and P4VPCB3 (CSL = 3), and the optimal resistance to protein adsorption can be reduced to 7.5 ng cm-2. The surface of P4VPCB2 can also exhibit excellent blood-inert function in the adhesion test with various human blood cells, offering a potential possibility for the future design of a new generation of blood-inert medical materials.
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The surface chemistry of octanoic acid was studied on a copper foil or a Cu(100) single crystal in ultrahigh vacuum using reflection-absorption infrared spectroscopy, temperature-programmed desorption, and supplemented by first-principles density functional theory (DFT) calculations. Octanoic acid adsorbs molecularly at 90 K, converting from a flat-lying species at low coverages to a more upright species at saturation. Adsorption at 300 K results in the formation of an η2-octanoate species, which binds with the alkyl group parallel to the surface with a tilted carboxylate group, as evidence by both infrared data and calculations. The flat-lying structure facilitates octanoate decomposition, which reacts by desorbing carbon dioxide at ~550 K. Increasing the octanoate coverage induces the alkyl chains to be more perpendicular to the surface to form a self-assembled monolayer with significant intermolecular van der Waals’ interactions. This stabilizes the adsorbate, which now decomposes by desorbing carbon dioxide at ~640 K, where infrared spectroscopy confirms that this also occurs by the carboxylate tilting towards the surface. The resulting heptyl species can either decompose by desorbing hydrogen or can also polymerize on the surface.
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The structural aspects of the complexation of Nd(III) in aqueous solutions with D-gluconate, D-galactonate and L-gulonate in the neutral to hyperalkaline pH range have been studied by using ¹H and ¹³C NMR, CD and Raman spectroscopies. Beside the identification of the binding sites, an attempt was made to reveal whether the structure of the complexes depends on the type of the ligand. It was concluded that the carboxylate group of each ligand has an essential role in the coordination to Nd(III). In solutions of pH > 5, other hydroxyl or alkoxide groups are also coordinated. Based on the NMR spectra, the coordination of several C-OH groups can be inferred, and CD measurements strongly suggest that beside the carboxylate, the C4-OH group takes part in the metal ion coordination in the Gluc– and Gal– complexes. On the basis of ourthe observations from all the three spectroscopic methods, Nd(OH)3 units covered by the sugar carboxylate is the most appropriate model for describing the systems at pH>12.
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Meteorites contain organic matter that may have contributed to the origin of life on Earth. Carbonyl compounds such as aldehydes and carboxylic acids, which occur in meteorites, may be precursors of biologically necessary organic materials in the solar system. Therefore, such organic matter is of astrobiological importance and their detection and characterization can contribute to the understanding of the early solar system as well as the origin of life. Most organic matter is typically sub-micrometer in size, and organic nanoglobules are even smaller (50–300 nm). Novel analytical techniques with nanoscale spatial resolution are required to detect and characterize organic matter within extraterrestrial materials. Most techniques require powdered samples, consume the material, and lose petrographic context of organics. Here, we report the detection of nanoglobular aldehyde and carboxylic acids in a highly primitive carbonaceous chondrite (DOM 08006) with ~ 20 nm spatial resolution using nano-FTIR spectroscopy. Such organic matter is found within the matrix of DOM 08006 and is typically 50–300 nm in size. We also show petrographic context and nanoscale morphologic/topographic features of the organic matter. Our results indicate that prebiotic carbonyl nanoglobules can form in a less aqueous and relatively elevated temperature-environment (220–230 °C) in a carbonaceous parent body.
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Understanding the acidic characteristics of graphene oxide (GO) and the relating deprotonation and proton transfer behaviors of oxygen-containing functional groups in the water environment is of great significance for the application of GO nanoscale materials. In this study, firstly, the density functional theory (DFT) method was applied to compute the explicit acidity constant (pKa) of the carboxyl and hydroxyl groups on GOs. The good consistency of our results with experiments approves the applicability of the designed thermodynamic cycles for computing the pKa of GOs. Secondly, the thermodynamics and kinetics of the deprotonation reactions of GOs in the presence of hydroxyl anions were investigated, quantitatively revealing that it is the carboxyl groups that mainly contribute to the surface charge acquisition of GO. Lastly, specific intramolecular proton transfer pathways were studied energetically, demonstrating that the proton is easily transferred between the adjacent hydroxyl group and the epoxy group on GO basal plane. This process could cause a change in the distribution of surface charge on GO surface, which will be very critical in understanding the surface properties of GOs.
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We present a computational study of vibrational circular dichroism (VCD) in solutions of (S)-lactic acid, relying on ab initio molecular dynamics (AIMD) and full solvation with bulk water. We discuss the effect of the hydrogen bond network on the aggregation behaviour of the acid: while aggregates of the solute represent conditions encountered in a weakly interacting solvent, the presence of water drastically interferes with the clusters - more strongly than originally anticipated. For both scenarios we computed the VCD spectra by means of nuclear velocity perturbation theory (NVPT). The comparison with experimental data allows us to establish a VCD-structure relationship that includes the solvent network around the chiral solute. We suggest that fundamental modes with strong polarisation such as the carbonyl stretching vibration can borrow VCD from the chirally restructured solvent cage, which extends the common explanatory models of VCD generation in aqueous solution.
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Copolymer of ethylene and tetrafluoroethylene (ETFE) was treated in superheated water with KMnO4. ETFE efficiently decomposed to F– and CO2. Specifically, when ETFE (30 mg) was treated for 6 h with aqueous KMnO4 (52.7 mM; the molar amount was 1.7-fold excess of that of the fluorine atoms in ETFE) at 320°C, the yields of F– and CO2 were 92 ± 1% and 73 ± 8%, respectively, and the total organic carbon content in the reaction solution was reduced to 4% of the carbon atom number in the initial ETFE. When the reactivity of ETFE was compared with that of poly(vinylidene fluoride) (PVDF), that is, an isomer of ETFE, ETFE required higher temperature to achieve mineralization. The present approach can reduce the reaction temperature allowing efficient mineralization of ETFE by 60°C, compared to the previous method using supercritical water with dioxygen.
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The structure of water, especially around the solute is thought to play an important role in many biological and chemical processes. Water−peptide and cosolvent−peptide interactions are crucial in determining the structure and function of protein molecules. In this work, we present the H−bonding analysis for model peptide likes glycyl-glycine (gly-gly), glycine-ւ-valine (gly-val), glycyl-ւ-leucine (gly-leu) and triglycine (trigly) and triethylammonium based carboxylate protic ionic liquids (PILs) in aqueous solutions as well as for peptides in ∼0.2 mol·L⁻¹ of aqueous PILs solutions in the spectral range of 7800−5500 cm⁻¹ using Fourier transform near-infrared (FT-NIR) spectroscopy at 298.15 K. The hydration numbers for peptides and PILs were obtained using NIR method of simultaneous estimation of hydration spectrum and hydration number of a solute dissolved in water. The H−bond of water molecules around peptides and PILs are found to be stronger and shorter than those in pure liquid water. We observe that the hydration shell around zwitterions is a clathrate-like cluster of water in which ions entrap. Watery network analysis confirms that singly H-bonded species or NHBs changes to partial or distorted ice-like structures of water in the hydration shell of PILs. The overall water H−bonding in the hydration sphere of PILs increases in the order TEAF < TEAA < TEAG < TEAPy ≈ TEAP < TEAB. The influence of PILs on hydration behavior of peptides is explored in terms of H-bonding, cooperativity, hydrophobicity, water structural changes, ionic interactions etc.
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All-inorganic perovskites have attracted substantial interest due to their outstanding thermal stability. However, the device performance is still inferior to the typical organic-inorganic counterparts because of the unsatisfying phase stability and defects of the inorganic perovskite films. Herein, we successfully demonstrated a multi-strategy to optimize CsPbI2Br perovskite solar cells (PSCs) based on dopant-free poly(3-hexylthiophene) (P3HT) by applying thienylmethylamine acetate (ThMAAc) additive to enhance the α phase stability and passivate the bulk defects of CsPbI2Br perovskite, followed by implementing BTCIC-4Cl interlayer at CsPbI2Br/P3HT interface, which could coordinate with both perovskite and P3HT to suppress the surface defects and promote the hole transport. Benefitting from these, we achieved a champion power conversion efficiency (PCE) of 16.3%, and the unencapsulated optimized device can retain 97% of the initial PCE after aging under N2 atmosphere at 85 °C for 530 h. This work opens up a new era of multi-strategy for improving performance and stability of CsPbI2Br PSCs based on dopant-free HTL. This article is protected by copyright. All rights reserved.
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A novel sublimable organic salt was synthesized, and its chemical structure was characterized by FTIR, 1D NMR, 2D NMR, and elemental analysis. In addition, the thermal phase transitions and thermal stability of new organic salt were investigated. The DSC and TGA results showed that the organic salt could convert into constituent molecules at < 145 °C before decomposition temperature (Tdec. ~ 200 °C) under atmospheric pressure without forming the liquid phase. Then, it was recondensed to regenerate the initial organic salt in the cool part of the vial. Therefore, it can be a promising organic salt towards the regeneration of spent catalyst from synthesis processes when the reaction mixture contains poorly volatile components and includes its use in gas-phase procedures. Also, the catalytic efficiency of new organic salt was investigated in the Knoevenagel condensation reaction. A variety of substituted arylidene and alkylidene malonates were isolated in 78–95% yield within six hours.‏ Under the optimized reaction conditions, the current catalytic procedure exhibited superiority compared to the mixed piperazine/acetic acid, piperidine/acetic acid, and piperidinium acetate. There were no significant changes in the new organic salt chemical structure and catalytic activity even after the 5th run. This work revealed the importance of the existence of simultaneous hydrogen bond acceptor/donor groups in our environmentally friendly catalyst to promote the Knoevenagel condensation reaction without the use of metal-containing catalysts.
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For controlling the surface properties by depositing molecules on the material surface, the selection of the functional groups of the stacked molecules is crucial. By introducing anthracenes in the molecular layer, which promote photodimerization and thermal/cleavage on photoirradiation or heating, it is possible to form a stimuli-responsive surface that enables changes in the molecular layer composition. In this study, we improve the fabrication process of the stimulus-responsive molecular layer with anthracene in order to facilitate the design of molecular layers according to the desired purpose. This is achieved by employing acid-base interactions for forming the molecular layers, with different functions for each layer. Thermal/photocleavage reactions of anthracene dimers are induced in the stacked molecular layer. Multilayers stacked with amine molecules exhibit different behavior on the cleavage reaction and the contact angle varies, depending on the type of molecules. The wettability on the surface covered with the molecular layer changes in response to the stimulation, proving the successful fabrication of a stimuli-responsive surface. The designed thermo- and photoresponsive molecular layer can potentially expand the scope of practical application as a control system for surface conditions.
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Organic solvent nanofiltration (OSN) membranes provide extraordinary opportunities for environment friendly and cost-competitive solvent recovery in petrochemical and pharmaceutical purifications. Currently, membranes that based on two-dimensional (2D) materials are extremely attractive in ultrafast molecular separations owing to the atomic thickness and remarkable physicochemical properties of the 2D nanosheets. Inspired by the structures and functions of vessel element that transport water in leaf veins, nickel phosphate nanotubes-reduced graphene oxide (NPTs-rGO) ultrathin laminar membrane is successfully prepared for ultrafast organic solvent nanofiltration. The in-situ synthetic NPTs can not only contribute to the size-dependent ultrafast molecular separation of the rGO membrane by providing additional molecular transport pathways as well as enlarging the interlayer space of the rGO layer, but also enhance the stability of the resultant membrane. The optimum membrane exhibits a methanol permeance of 670 L m⁻² h⁻¹ bar⁻¹ and a high rejection toward molecules greater than 2 nm (MWCO: 650 Da). More importantly, the NPTs-rGO membrane shows promising anti-swelling property under OSN operating conditions. Inspired by leaf veins, this strategy provides insight into designing high-performance lamellar membranes with tubular-channel network, which may promote the fabrication and application of lamellar membranes in OSN.
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Double lap joints were prepared using epoxy adhesive and aluminum plates, and their high-temperature strength properties were studied. Tensile, thermal aging, creep, and cyclic fatigue tests were performed to systematically investigate the effects of the aging temperature, testing temperature, stress waveform, and stress ratio on the strength and fracture morphology of the double lap joints. When the specimen was exposed to 135°C, the strength decreased significantly. Also, the relationship between the test temperature and shear strength could be expressed using an equation obtained from thermal activation theory. Additionally, in the fatigue test at room temperature, the strength of the specimen subjected to constant stress was higher than that of the specimen subjected to cyclic strain. The effect of creep deformation increased in the creep test at high temperatures, and therefore, the strength decreased significantly.
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The development of supported glycosylated lipid layers is an important trend in the field of glyconanomaterials for their interest in understanding sugar-sugar and protein-sugar interactions, these being at the core of cellular, bacterial or viral adhesion. The conventional self-assembled monolayer (SAM) approach generally requires a thiolated glycoconjugate and a gold substrate. In this work, we show how glycolipid amphiphiles of natural origin, commonly known as microbial biosurfactants, can be easily deposited onto a substrate. Spontaneously produced by microorganisms but lacking a thiol group, one can take advantage of their self-assembly properties to prepare homogeneous supported lipid monolayers (SLM). We then choose a saturated glucolipid, G-C18:0, which forms a colloidal lamellar phase under diluted conditions. The lamellae can then be deposited onto a substrate (silicon, gold) using a physical method (dip coating). Dip coating is preferred over more classical deposition methods (Langmuir-Blodgett-LB-, vesicle fusion or spin-coating) because of its versatility, compatibility with aqueous solutions and robust control of the thickness below 10 nm. Defect-free glycosylated SLM from a microbial biosurfactant are then easily developed. A combination of ellipsometry, fluorescence microscopy, atomic force microscopy and infrared nanospectroscopy (AFMIR) show that the glycosylated SLM are defect-free, have a thickness of 2.8 ± 1.0 nm and they are highly homogeneous at scales going from the nm to cm.
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Polycarboxylate ether (PCE) superplasticizers with different molecular structure were synthesized by copolymerizing macro-monomer with cis-butenedioic anhydride (MAH) and trans-1,2-ethenedicarboxylic acid (FA). Gel permeation chromatography, specific charge density, Fourier transform infrared spectroscopy, ¹H and ¹³C nuclear magnetic resonance were used to characterize these co-polymers. Their Ca²⁺ binding capacity, adsorption behaviors, retardation effects and dispersion efficiency were investigated by the calcium-ion selective electrode, total organic carbon, X-ray Photoelectron Spectroscopy, zeta potential, calorimetry measurements, mini-cone and rheological tests. Results indicated that PCE containing more FA possesses the higher density of –COO– groups, due to the higher reactivity of FA than MAH. The high density of –COO– groups in PCEs significantly affects their adsorption behaviors, retardation, and dispersion of cement pastes. Intermolecular chelation between –COO– groups and Ca²⁺ is dominated for FA-PCE, while the main coordination modes between –COO– in MAH-PCE and Ca²⁺ are intramolecular chelation owing to more adjacently distributed –COO– groups. FA-PCE exhibits larger adsorption amount and thicker adsorption layer compared with MAH-PCE. Hence, the FA-PCE demonstrated stronger dispersion efficiency, with which the cement pastes showed excellent flowability and rheological properties, correspondingly.
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Herein, a facile, water-compatible, and one-pot synthesis of a core-shell polysilicate molecularly imprinted polymer (SiO2MIP) on polyvinylpyrrolidone capped gold nanoparticles ([email protected]) through the condensation polymerization of vinyltrimethoxysilane (VTMS) as a functional monomer, tetraethoxysilane (TEOS) as a cross-linker, and uric acid (UA) as a template has been reported. The response surface methodology based on central composite design (RSM−CCD) was used to optimize the conditions of the reaction. The characteristics of the resulting composite ([email protected]@SiO2MIP) produced under the optimized conditions were evaluated using UV-vis spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), and water contact angle measurement. Next, the as-synthesized [email protected]@SiO2MIP served as a novel electrochemical platform for the detection and determination of UA in a urine sample. Differential pulse voltammetry (DPV) was used to construct the calibration curve that showed two linear concentration ranges. In addition, the limits of detection (LOD) and quantification (LOQ) of the method were obtained to be 4 × 10⁻⁷ and 1 × 10⁻⁶ M, respectively. Also, the repeatability and reproducibility of the sensor (RSD%) were achieved to be 7% (n=8) and 3% (n=5), respectively. At last, the proposed sensor was successfully applied for the measurement of UA in a urine sample.
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Two types of carbon, i.e. carbon electrode (CE) and carbon furnace lining (CFL) were modified with silicon oxycarbide (SiOC) or carbon nanotubes-containing SiOC (SiOC/fCNT) by means of polysiloxane impregnation and pyrolysis. The two carbon materials differed in pore size and in surface chemical state. The impact of these factors on the infiltration efficiency was investigated by comparing the physical, electrical and mechanical properties in samples before and after infiltration. It was shown that SiOC phase is formed in the CE macropores, leading to a reduction in the average pore size from 8.2 to 5.3 μm, and in porosity from 12.6 to 7.3%. For CFL, which contains both meso- and macropores, the observed changes in porosity are smaller. Introducing fCNT into the resin changes its surface nature from hydrophobic to hydrophilic. This modified solution better wets a CE surface containing functional groups and provides an enhanced interface contact between this carbon and SiOC. The fCNT-modified SiOC phase improves the compressive strength and modulus of both types of carbon. The electrical resistivity of CE modified with SiOC/fCNT is slightly higher, whereas for CFL it does not change. Oxidation tests in air up to 1000 °C showed a significant reduction in the mass loss of both carbon materials after their modification with pure SiOC and SiOC/fCNT. The proposed infiltration procedure can be applied to conventional carbon and graphite technology, in particular to porous carbons containing a macropore fraction.
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Flexible supercapacitors (SCs) are promising energy storage devices for wearable and soft technologies. However, efforts to obtain reliable performance during mechanical deformation have been frustrated by the inevitable displacement and...
Chapter
Acquiring information about the fatty acids profile in cow milk is an important feedback for managing feed at the level of individual cows and improving the milk’s nutritional value. This chapter explores the feasibility of using near-infrared (NIR) spectroscopy for measuring some of the most common dietary fatty acids (FA) in liquid, thawed cow milk. For this study, 252 milk samples were collected from 9 cows over the course of 14 weeks. The content of 18 individual FA was measured using gas chromatography and NIR spectra were acquired in transmittance mode in the range of 400–2499.5 nm with 0.5 nm resolution. The spectra were preprocessed using smoothing and detrending, and quantitative analysis was performed using partial least squares regression. Interestingly, the most influential variables were found in two regions 1300–1400 nm and 1600–1800 nm. In both regions, the influential variables were attributable to absorbance bands of the same water species—small proton hydrates (one to eight water molecules in a hydrate complex), hydration water and free water. The best prediction results were obtained for 8 FA when the spectral region was narrowed to 1600–1800 nm, where both absorbance of FA and water contributed to the measurements.
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We demonstrate the ability to modulate polyacrylamide hydrogel surface morphology, rheological properties, adhesion and frictional response by combining acrylic acid copolymerization and network confinement via grafting to a surface. Specifically, Atomic Force Microscopy imaging reveals both micellar and lamellar microphase separations in grafted copolymer hydrogels. Bulk characterization was conducted to reveal the mechanisms underlying microstructural changes and ordering of the polymer network, supporting that they stem from the balance between hydrogen bonding in the substrate-grafted hydrogels, electrostatic interactions, and a decrease in osmotically active charges. The morphological modulation has direct impacts on the spatial distribution of surface stiffness and adhesion. Furthermore, lateral force measurements show that the microphase separations lead to speed and load-dependent lubrication regimes as well as spatial variation of friction. A proof of concept via salt screening demonstrates the dynamic control of surface morphology and adhesion. This work advances the knowledge necessary to design complex hydrogel 2 interfaces that enable spatial and dynamic control of surface morphology and thereby of friction and adhesion through modulation of hydrogel composition and surface confinement, which is of significance for applications in biomedical devices, soft tissue design, soft robotics, and other engineered tribosystems.
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Traditional nanofiltration (NF) membranes meet a bottleneck in throughput due to the lack of flexibility in pore structure control of the polyamide selective layer. This work developed a highly-permselective NF membrane by creating a controlled polyarylester selective layer via a facile method of metal-phenolic network (MPN) modulated interfacial polymerization between 5,5,6′,6′-tetrahydroxy-3,3,3′,3′-tetramethyl spirobisindane (TTSBI) and trimesoyl chloride (TMC). It was hypothesized that in the presence of FeCl3, the catechol groups of TTSBI first formed a Fe³⁺/TTSBI complex to construct the MPN and subsequently reacted with TMC, eliminating structural defects in the selective layer. The solution chemistry studies and membrane optimization results verified the significant role of Fe³⁺ in forming metal-phenolic coordination and thus defectless pore structure. The resulted Fe-TTSBI-TMC membrane exhibited greatly reduced pore size of 0.68 nm and narrow pore size distribution. The rigid and twisted feature of TTSBI endowed the polyarylester layer with high porosity. This ingeniously designed synergistic effect rendered the resulted membrane with a high pure water permeability of 15 L m⁻² h⁻¹ bar⁻¹, about 3 times higher than typical polyamide NF membrane prepared by piperazine and TMC; while achieved high salt and molecular rejections (e.g., 98% rejection of Na2SO4, 100% rejection of vitamin B12), exhibiting superior perm-selective properties as compared to most NF membranes incorporating microporous materials. Accurate separation between molecules of different sizes of vitamin B2 and vitamin B12 was achieved with 100% efficiency. Hence, this work provides a promising alternative for skillful control of NF membrane pore structure towards efficient and precise molecular separation.
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Deep Eutectic Monomers were prepared by dissolution of selected tetrabutylammonium salts serving as hydrogen bond acceptors (HBA) in methacrylic acid (MAA) acting both as hydrogen bond donor (HBD) and vinyl monomer. In this study, we systematically investigate the influence of chloride, nitrate, hydrogensulphate and fluoroborate anions on properties of DEMs and the course of radical photopolymerization. Combining FTIR, 1 H and 13 C NMR spectroscopy we found the that degree of coordination of MAA in DEMs by anions follows the order: Cl⁻ > NO3⁻> HSO4⁻>>BF4⁻. Moreover, the studies indicated that the strength of hydrogen bonds between HBD and HBA in DEMs is lower than in MAA dimers. Real-time FT-IR spectroscopy studies of photopolymerization of DEMs indicate that the mixtures formed from MAA and tetrabutylammonium fluoroborate show significant lower initial photopolymerization rate in comparison with other investigated DEMs, which polymerize with similar rates.
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The titration of sulphuric acid by infrared spectroscopy using the attenuated total reflection (ATR) technique was made in the 0 to 14 pH range for solutions ranging from 1.89 to 0.01 M. The subtraction of the water spectrum was made using acidic, neutral, and basic waters which exhibit different spectra. The results gave the spectra of mixtures of the HSO4/- and SO4/2- ionic species in solutions. For each concentration, factor analysis (FA) sorted the spectra of the pure ionic species and gave through the multiplying factors (MF) the distribution of the species as a function of pH. This distribution is the same as that obtained from the equilibrium equations. The IR measurements gave directly the ratios of the activity coefficients of HSO4/- and SO4/2- ions. This ratio varies with the total concentration of both ions but is independent of the relative concentration. The fitting of the experimental and theoretical volumetric titration curves in the high and low pH regions gave the mean activity coefficients of the other species present in the solutions. The values obtained are comparable to those obtained by electrochemical measurements. These results show that it is possible to use IR spectroscopy to study aqueous solutions of inorganic acids from low to high concentrations.
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The light and heavy liquid water (H2O–D2O) mixtures in the 0–1 molar fraction were studied in the mid-infrared by Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy. Five principal factors were retrieved by factor analysis (FA). When D2O is mixed with H2O, the HDO formed because of the hopping nature of the proton (H or D) results in three types of molecules in equilibrium. Because of the nearest-neighbor interactions, the three molecules give rise to nine species. Some of the species evolve concomitantly with other species giving the five principal factors observed. We present the spectra of these factors with their abundances. The calculated probability of the species present at different molar fractions which when the concomitant species are combined gives the observed abundances. To appreciate clearly the difference between the principal spectra, a Gaussian simulation of the bands was made. Because of the numerous components that make up the stretch bands, they are not very sensitive to changes in composition of the solutions; nevertheless, they do indicate the presence of new entities other than the pure species. The deformation bands, more sensitive to such changes than the stretch bands, clearly indicate the presence of the three types of molecules as well as of intermediate species. These bands are sensitive to the two hydrogen bonds on the oxygen atom that a reference molecule makes with its nearest-neighbors, but not to the hydrogen bonds that the nearest-neighbors make with the next nearest neighbors.
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The aqueous solutions of CsCl were studied at room temperature by infrared (IR) spectroscopy in the entire solubility range, 0–1200 g/L, using attenuated total reflection (ATR) sampling. The influence of anomalous dispersion on the IR–ATR spectra was evaluated by calculating the imaginary refractive index, k(ν), of each sample. Factor analysis (FA) was used to determine the number and abundance of species in the solutions. FA applied to both k(ν) spectra and IR-ATR spectra produced two principal spectra with a similar abundance of species. This result indicates that, even at high salt concentration, the optical effects do not influence the chemical analysis of IR–ATR spectra. The spectral modifications related to the salt concentrations are mainly first order. Second order effects were observed, but being weak, were not investigated. The two principal spectra are related to the two species present in the solution: pure water and CsCl–solvated water. From the latter, 2.8±0.4 water molecules were calculated to be associated with each close-bound Cs+/Cl− ion pair. In the case of KCl and NaCl aqueous solutions, both of which showed the same number of species, the number of water molecules associated to an ion pair was 5.0±0.4. That the latter number is different from that of CsCl indicates that the interaction between water molecules and ion pairs is different when cation Na or K in the chloride salt is replaced by Cs.
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The infrared (IR) spectra of glycine in aqueous solutions were obtained in the pH range 0.2 to 14 in order to determine the ionic distribution of the molecule as a function of pH by factor analysis (FA). After subtraction of the water bands, FA was used to separate the spectra of each ionic species and determine their real abundance. The p K values were retrieved from the volumetric titration a as a function of pH and were used to obtain the theoretical abundance of each ionic species as a function of pH. These distribution curves were compared with the distribution curves obtained from IR. The agreement between the two curves was good. The following species were observed for glycine in water: the cation (pH 0 to 5); the zwitterion (pH 0 to 12.5); and the anion (pH 7 to 14).
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Transmission spectra of aqueous solutions are difficult to obtain because in the 3 mu m infrared region, the high absorptivity of water requires the use of thin films. In contrast, attenuated total reflectance (ATR) spectra of aqueous solutions, not requiring thin films, are easily obtained. Unfortunately, compared to measurements made by transmission, ATR measurements cause some variation in the band shape due to the anomalous dispersion (AD) effect. To evaluate these variations, we studied pure water and KCl aqueous solutions. We then compared the ATR spectra of both substances with the real and imaginary refractive index spectra calculated by using the Kramers-Kronig relation. As long as the proper material is used in the ATR cell and the concentration of water is not significantly decreased, then the IR-ATR measurements directly reflect the chemistry of the sample.
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The infrared (IR) spectrum of a sample in a saline solution cannot be retrieved adequately when the spectrum of pure water is subtracted. Some water bands remain in the spectrum. The retrieved spectrum is good only when the spectrum of NaCl in water at the right concentration is subtracted. However, when the concentration of the salt is unknown, it is still possible to obtain a good spectrum of the sample free of water. This is done by subtracting from the original spectrum a fraction of two eigenspectra of water: one for pure water and one for NaCl solvated water. The fraction of the eigenspectra is determined with the 2100 and 3300 cm -1 bands. The effectiveness of the method is illustrated with a solution of sodium monochloroacetate in a saline solution.
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Factor analysis of the attenuated total reflection (ATR) absorbance spectra of aqueous saline solutions has shown that these spectra are linear combinations of two eigenspectra: pure water and salt-solvated water. This paper outlines the general equations needed to formalize these experimental results. In the case of binary salts in aqueous solutions, the equations allow interpolation and extrapolation from one concentration to another. The accuracy of the calculation method was adequately verified on aqueous solutions of KCl. The equations made it possible to calculate the ATR absorbance spectrum of a "pure" KCl-solvated water. The latter, which contains no ordinary water, enabled us to determine that solvated water forms clusters made up of a pair of ions with five molecules of water. The same results were obtained with NaCl aqueous solutions.
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The IR spectrum of a sample in acidic and alkaline solutions cannot be retrieved adequately when only the spectrum of pure water is subtracted. After such an operation, some water bands remain in the spectrum, which also has a distorted baseline. An analysis of a series of IR spectra of HCl and NaOH solutions showed that they could be represented by two pairs of eigenspectra, one pair for the acidic solutions and the other for the basic solutions. The fraction of each eigenspectrum of a sample in an acidic or alkaline solution is determined with the 2100 and 3300 cm-1 water bands. After subtraction, no baseline adjustment is necessary. The effectiveness of the method used to subtract the water bands is illustrated with solutions of malic acid at low and high pH.
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The titration of NaOH by HCl is achieved through infrared spectral measurement of the various mixtures. Factor Analysis (FA) is used to separate the spectra. Four principal spectra were necessary to perform the analysis: pure water, 2.09 M HCl, 2.23 M NaOH, and 2.60 M NaCl solvated water. Each of the 18 experimental spectra obtained was determined to be a linear combination of these principal spectra. The composition of the solutions retrieved from the IR analysis is identical to what was determined by the mass balance. The mean activity coefficient of HCl was calculated using the concentration of HCl obtained by IR and the activity obtained by pH measurements. It was found that the mean activity coefficient increased by a factor greater than 2 in the presence of 1 M NaCl. Because the water molecules associated to the ionic pair H+/Cl-, as observed by IR, an unmodified by the presence of the salt, such an increase cannot be attributed to a modification of the strong association of the water molecules to the pair of ions.
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Extrapolation techniques were used to obtain pure salt-solvated water spectra from the attenuated total reflection infrared spectra (ATR-IR) of aqueous solutions of the nine alkali halide salts LiCl, NaCl, KCl, CsCl, NaBr, KBr, NaI, KI, and CsI and the alkaline–earth chloride salt MgCl2. These salts ionize completely in water. The ions by themselves do not absorb in the IR, but their interactions with water can be observed and analyzed. A pure salt-solvated water spectrum is easier to analyze than that of a combined solution of pure water and salt-solvated water. Although the salt-solvated water spectra examined have distinctive signatures, they can be classified in three categories: those similar to NaCl; those not similar to NaCl; and MgCl2, in a class by itself. Each of the pure salt-solvated water spectra differs from that of liquid water, though the number of bands is the same. From the Gaussian band fitting, we found that the positions of the bands were fairly constant, whereas their intensities differed. The salt hydration numbers were determined: for NaCl, KCl, NaBr, KBr, and CsI solutions it is 5; for KI and MgCL2 it is 4; for NaI it is 3.5; for CsCl it is 3; and for LiCl it is 2. From these results we found that each pair of ions (monoatomic ions) of the ten salt solutions studied are close bound and form a complex in a cluster organization with a fixed number of water molecules. © 2001 American Institute of Physics.
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This paper presents the infrared (IR) titration of aqueous sulfuric acid solutions (0.50 M) obtained by the attenuated total reflection (ATR) sampling technique. After subtracting the water spectra, the spectra of the ionic species of H2SO4 in the 0−14 pH range were separated by factor analysis (FA) which also gave their abundance. The results were in agreement with the theoretical calculation of the distribution of the species. Three sulfate species were found:  HSO4-, SO42-, and HSO4-/HCl. The latter stands for the bisulfate−hydronium complex formed by the addition of HCl to obtain measurements in the 0−0.47 pH range. For 0.50 M sulfuric acid, the comparison between the experimentally IR-determined quantities and the theoretical values gave a mean activity coefficient of 0.12 ± 0.04, a value comparable to that from electrochemical measurements. Three types of water were quantitatively determined in the solutions:  acidic water, basic water, and neutral water. The latter is always present while the two others are present in the low and high pH range, respectively. Another type of water strongly associated with the sulfates is also present. Moreover, knowledge of the behavior of the different types of water as the titration proceeded permitted us to give the details of the neutralization reactions of aqueous sulfuric acid by sodium hydroxide.
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The effects of ions on bulk properties of liquid water, such as viscosity, have suggested that ions alter water's hydrogen-bonding network. We measured the orientational correlation time of water molecules in Mg(ClO4)2, NaClO4, and Na2SO4 solutions by means of femtosecond pump-probe spectroscopy. The addition of ions had no influence on the rotational dynamics of water molecules outside the first solvation shells of the ions. This result shows that the presence of ions does not lead to an enhancement or a breakdown of the hydrogen-bond network in liquid water.
Chapter
Infrared spectroscopy can be described as the use of instrumentation in measuring a physical property of matter, and the relating of the data to chemical composition. The instruments used are called infrared spectrophotometers, and the physical property measured is the ability of matter to absorb, transmit, or reflect infrared radiation.
Article
For the first time absorption spectra of H5O+2, D5O+2, (CH3OH)2H+, H3O−2, D3O−2 and (CH3O)2H− ions are extracted from IR spectra of solutions of acids and strong bases and detailed theoretical analysis of these spectra is performed with due regard for the kinematic, dynamic and electro-optical anharmonicities of vibrations. The set of ions chosen for the study provided the possibility to compare the spectra of positively and negatively charged ions, of an ion and its isotopically different analogue and of hydrated and solvated proton forms. A good agreement between the calculated and experimental data, without using any kind of fitting, indicates that the model proposed for description of any-strength hydrogen-bond spectral properties is applicable for spectra calculation of systems containing strong (about 32 kcal mol−1) H bonds. This agreement is also a direct proof (in terms of molecular structure approach) for complexes of the type (A⋯H⋯A)± to be simplest stable proton and hydroxyl ion solvates in solutions of acids and strong bases. This study elucidates the origin and mechanisms of the continuous absorption in IR spectra of ions with symmetric hydrogen bonds and shows that the constancy of the O⋯H⋯O group properties in all systems containing this group can be a basis for creating a unified catalytic action theory of acids and bases.
Article
The previously reported nonreproducibility of the intensity of the OH stretching band of liquid water has been explored. It was found that it can be eliminated in measurements with the Circle® multiple ATR cell by ensuring that the ATR rod is coaxial with the glass liquid holder. It was also found that normal laboratory temperature variations of a few degrees change the intensity by ≤~1% of the peak height. A new imaginary refractive index spectrum of water has been determined between 4000 and 700 cm-1 as the average of spectra calculated from ATR spectra recorded by four workers in our laboratory over the past seven years. It was obtained under experimental and computational conditions superior to those used previously, but is only marginally different from the spectra reported in 1989. In particular, the integrated intensities of the fundamentals are not changed significantly from those reported in 1989. The available imaginary refractive index, k, values between 15,000 and 1 cm-1 have been compared. The values that are judged to be the most reliable have been combined into a recommended k spectrum of H2O(l) at 25°C between 15,000 and 1 cm-1, from which the real refractive index spectrum has been calculated by Kramers-Kronig transformation. The recommended values of the real and imaginary refractive indices and molar absorption coefficients of liquid water at 25 ± 1 °C are presented in graphs and tables. The real and imaginary dielectric constants and the real and imaginary molar polarizabilities in this wavenumber range can be calculated from the tables. Conservatively estimated probable errors of the recommended k values are given. The precision with which the values can be measured in one laboratory and the relative errors between regions are, of course, far smaller than these probable errors. The recommended k values should be of considerable value as interim standard intensities of liquid water, which will facilitate the transfer of intensities between laboratories.
Article
The multiple attenuated total reflection IR spectra of solutions of sodium acetate in acetic acid have been recorded in the range from 9000 to 4000 cm-1. The CH3COO- anion and an acid molecule form be complex (CH3COO...H...OOCCH3) with a strong symmetric H-bond.
Article
The far infrared hydrogen bond vibration and the infrared continua observed when hydrogen bonds show large proton polarizability are studied as a function of the pKa of the donor or acceptor molecules with three families of systems: (1) substituted phenols-trimethylamine N-oxide, (2) pyridinium-pyridine, and (3) methanesulfonic acid-S, P, As oxide.With the first family of systems the hydrogen bond vibration depends only on the pKa of the phenols and is independent of changes in the mass of the phenols. With the second family of systems the continua and hence the proton polarizability are independent of the pKa of the protonated pyridines. With the third family, i.e., the methanesulfonic acid-S, P, As oxide systems, single minimum proton potentials are present. In these systems with largely symmetrical O− ⋯ H+ ⋯ O bonds the proton potentials are broad and flat. These bonds also show proton polarizability, and the continua extend into the far infrared region. With the most symmetrical systems the hydrogen bond vibration is strongly broadened and merges into the continuum. All these experimental results are explained by semiempirical and by SCF ab initio treatments.
Article
Aqueous attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of 24 aliphatic monocarboxylates have asymmetric COO− stretch frequencies (νas) of 1541 cm−1 to 1678 cm−1, while the symmetric stretch frequencies range from 1202 cm−1 to 1417 cm−1. The pKa values of these acids are linearly correlated with νas according to the equation (pKa = 66.70-0.04018νas, σ = 0.266 pKa units, r2 = 0.968). This correlation should be useful in determining the pKa values of acids in complex mixtures and the site pKa values of carboxyl groups in polyacids. Semi-empirical molecular orbital calculations using the AM1 parameter set give νas values which correlate well with experimental νas (σ = 11.3 cm−1), although model νas values are ≈ 500 cm−1 too high; the PM3 parameter set predicts νas values that are only ≈ 300 cm−1 too high, but which do not correlate as well with experiment (σ = 17.6 cm−1).
Article
Twelve carboxylic acid–pyridine systems have been studied in chloroform solutions in the mid-IR and the far-IR regions as a function of the pKa of the carboxylic acids at 25 °C and at –40 °C. If the acidity of the carboxylic acid is small a strongly asymmetrical double-minimum proton potential is present. With increasing acidity the hydrogen bonds become stronger, i.e. the bond length shortens and the proton potentials become more symmetrical in character. In these cases the barrier of the potentials becomes very low and the situation may be compared with a broad, flat, asymmetrical single minimum. Therefore, the continua in these complexes are very similar to those in systems with broad, flat, single-minimum proton potentials. With increasing polarity of the complexes the hydrogen bonds lengthen again and the double minimum becomes still more symmetrical. The two proton-limiting structures OHN O–H+N can be distinguished by different carbonyl bands; the band of the polar structure is found at relatively high wavenumbers indicating that the barrier is low. Almost symmetrical double-minimum proton potentials are now present. With the most acidic system at –40 °C, the polar structure has a larger weight.
Article
Trifluoroacetic, difluoroacetic and formic acids have been studied, pure and in aqueous solutions, by i.r. spectroscopy. The formation of monomers from the dimers and dissociation of the acids with increasing dilution is demonstrated by bands in the spectra; the polarizability of hydrogen bonds formed is indicated by regions of continuous absorption. At very high concentrations (n= number of water molecules per acid molecule < 1), acid–water hydrogen bonds are formed. With trifluoroacetic acid a double minimum energy surface (with a deeper well at the anion) is present in these hydrogen bonds. They cause an i.r. continuum extending from 3000 cm–1 over the whole range studied (3000-600 cm–1) indicating that these hydrogen bonds are easily polarizable. With difluoroacetic acid, the degree of asymmetry of these bonds is larger, but they are still polarizable, as indicated by a continuum in the range 3000-1750 cm–1. With formic acid, these acid–water hydrogen bonds are largely asymmetric. In the case of trifluoro- and difluoroacetic acids, with addition of more water the absorbance of the continuum continues to increase between n= 1 and n= 3, since the degree of asymmetry of the acid–water hydrogen bonds decreases because of the influence of these water molecules. An additional reason for this intensity increase may be the coupling of transitions in the polarizable hydrogen bonds with vibrations in the environment. On further dilution, the absorbance of the continuum decreases. With increasing dilution, trifluoroacetic acid protons transfer into water–water hydrogen bonds, i.e., H5O+2 is formed. Also in relatively diluted solutions the continuum is caused not only by the easily polarizable hydrogen bonds in H5O+2 groupings, but also by polarizable acid–water hydrogen bonds which are still present.
Article
As in aqueous base solutions (BHB)–(where B is CH3O–) hydrogen bonds form in alcohol solutions of CH3OK and KOH. A continuous i.r. absorption shows that a double minimum potential well is present in these hydrogen bonds and that their polarisability is extremely large. Based on the experimental results presented here and on previously developed theories the following are discussed: (1) the fluctuation of the H7O–3 group; (2) the transition of the anomalous defect proton conductivity (Grotthus mechanism) to the normal hydrodynamic mechanism with increasing concentration; (3) the processes occurring during dissociation of a base. Furthermore, the i.r. spectra of solutions of pyrrole in alcohol and of imidazole and hydroxypyridine both in water and alcohol are plotted as a function of their deprotonation by CH3OK or KOH. In addition to the symmetrical (BHB)– hydrogen bonds between alcohol molecules, strongly polarisable (NHN)– hydrogen bonds between pyrrole molecules and polarisable (NHO)– bonds between pyrrole and alcohol are also found in the pyrrole solutions. Strongly polarisable (NHN)– hydrogen bonds form in the imidazole solutions at deprotonation degrees of up to 50 %. Unsymmetrical polarisable (NHO)– hydrogen bonds with the solvent molecules at degrees of deprotonation > 50 % and symmetrical (BHB)– hydrogen bonds between the solvent molecules at degrees of deprotonation > 80 % are found. This is shown by the variation in the plots of the absorbance of the continuum against % deprotonation. Finally, the formation of polarisable hydrogen bonds on deprotonation of the 2-hydroxypyridine is discussed.
Article
Experimentally observed and calculated infrared (IR) continua of the homoconjugated hydrogen bonds in H5O⁺2 or deuterium bonds in D5O⁺2, both of which show large polarizability, are compared. With N⁺H⋯N⇌N⋯H⁺N bonds, for instance, the far IR continua give information on how strongly these bonds are polarized to one or the other side. In the case of heteroconjugated AH⋯B ⇌ A⁻⋯H⁺B bonds it is shown how the reaction field creates two minima within these bonds. The wavenumber-dependent intensity distribution of the IR continua is discussed as a function of the length and strength of the hydrogen bonds.
Article
Homoconjugated B+H·B⇌B·H+B hydrogen bonds cause intense continua in the IR spectra. Continua are also observed in the case of heteroconjugated (I) AH·B⇌A−·H+B (II) bonds if the two proton limiting structures have noticeable weight. In this case, with the exception of extreme systems, the double minimum of the proton potentials is created by the interactions of these hydrogen bonds with their environments. Finally, structurally symmetrical or largely structurally symmetrical hydrogen-bonded chains or chains which are built up by the above mentioned hydrogen bonds cause continua by collective proton motion.Theory proves that all these three types of hydrogen bonds and hydrogen-bonded systems show so-called proton polarizabilities due to proton shifts. These proton polarizabilities are two orders of magnitude larger than usual polarizabilities due to distortion of electron systems, and with hydrogen-bonded chains they may be much larger still. The calculated line spectra of all these systems show many lines which shift as a function of the electrical field strength at the hydrogen bonds (simulating their environments). In the whole region some lines vanish, some arise with changes of the electrical field strength. The IR continua occur due to strong interaction effects of these hydrogen bonds or hydrogen-bonded systems with their environments which are caused by the large proton polarizability. Hydrogen bonds with large proton polarizability are of great significance with the electrochemistry of acid and base solutions. Furthermore, it is proved that a large number of hydrogen bonds and hydrogen-bonded systems occurring in biochemistry show large proton polarizability. Their hypothetical importance for biological functions is discussed. Finally, it is shown that at surfaces hydrogen bonds and hydrogen-bonded systems with large proton polarizability may be present and should be taken into account, when studying reactions at surfaces in which protons are involved.
Article
The complexes formed by phenols with 1,3,4,6,7,8-hexahydro-1-methyl-2H-pyrimido[1,2-a]pyrimidine (mTBD), an N-base with guanidine-like character, were studied as a function of the pKa of the phenols by FT-IR spectroscopy. The following phenols were used: 4-cyanophenol (4-CNPh), pentachlorophenol (PCP) and 2,6-dichloro-4-nitrophenol (DNPh). In the case of chloroform solutions of 1:1 mixtures of the phenols with MTBD the corresponding complexes are formed completely. With increasing acidity of the phenols the hydrogen bonds become increasingly asymmetrical. The OH … N ⇔ −O … H+N hydrogen bond in the 4-CNPh-MTBD complex shows large proton polarizability. In the other cases only the polar structure is realized. With increasing phenol MTBD ratio, the formation of chains with two phenol molecules is observed. With decreasing pKa of the phenols the fluctuation is limited to the phenol-phenolate bond and finally, the phenol-protonated MTBD bond begins to dissociate. In acetonitrile solutions, N+H … O− hydrogen bonds are observed in the case of the 1:1 mixture of 4-CNPh with MTBD. A weak continuum indicates the presence of homoconjugated phenol-phenolate bonds with large proton polarizability. In the case of 2:1 mixtures only protonated MTBD and homoconjugated phenol-phenolate bonds are observed, independent of the pKa of the phenols. The results are discussed with regard to the proton pathway in bacteriorhodopsin.
Article
N,N-((Butyloxy)propyl)amino diacetic acid is an amphoteric surfactant of the glycinate family. The synthesis of this glycinate was achieved via the ester route to obtain a pure compound. The infrared (IR) spectra of the aqueous solutions of this compound were obtained in the pH range 0.2−14 in order to determine the ionic distribution of the molecule as a function of pH. After subtracting the water bands in the IR spectra, factor analysis (FA) was used to separate the spectra of the ionic species and determine their abundance. The pKa's were retrieved from the volumetric titration as a function of pH. The values were used to calculate the volumetric abundance of each ionic species as a function of pH. The distribution curves thus obtained were compared with the normalized distribution curves obtained from the IR data. There is a good agreement between the two curves. The following species were obtained for the glycinate in water: the cation (pH 0−3.4), the zwitterion (pH 0−5.4), the monocarboxylate (pH 1−12), and the dicarboxylate (pH 7−14).
Article
Quantitative infrared (IR) titration of 1.80 M malic acid is presented where factor analysis (FA) was used to obtain the principal species' spectra and their abundances. Three malic species and three water species were obtained. The distribution of the species as a function of pH was made from which their pKa values were determined. The experimental points of the distribution curves correspond to the values calculated from the thermodynamic equilibrium equations. A precise determination of aqueous malic IR bands was obtained from the real spectra of the malic species. The hydrates' hydration numbers were determined to be 2.0 ± 1.0, 3.0 ± 2.0, and 4.0 ± 0.5 for malic acid, mono-, and disodium malate, respectively. The hydrates are stable throughout the pH range where the species are present. The double and single CO stretch bands of malic acid are situated at 1719 and 1272 cm-1, respectively. The antisymmetric and symmetric CO stretch bands of mono- and disodium malate are situated at 1580, 1400 cm-1 and 1563, 1395 cm-1, respectively. Malic acid shows four very broad bands in the 3800−1800 cm-1 region as a continuous absorption assigned to the OH stretch of hydrogen bonded water and alcoholic groups to carboxylic groups. The 2930 and 2580 cm-1 bands, which are far from the 3500 cm-1 band, indicate strong hydrogen bonds. Disodium malate shows one large band at 3320 cm-1 assigned to the OH stretch of solvated water and alcoholic groups. Monosodium malate has the bands of both malic and disodium malate slightly displaced, but with half their intensities.
Article
Two sucrose hydrates were found by factor analysis (FA) of the mid-infrared attenuated total reflectance (MIR-ATR) spectra of a series of aqueous sucrose solutions:  sucrose penta- and dihydrate. The spectra of the isolated hydrates and their abundances as a function of concentration were obtained. Apart from the intensity of the water bands, the two hydrates differ only in a few sucrose bands in the C−O region. From the distribution of the species, the equilibrium between penta- and dihydrate was deduced:  3H2O + C12H22O11·2H2O C12H22O11·5H2O. The pentahydrate equilibrium constant was found to be Ke = (4.1 ± 0.3) × 10-5 L3 mol-3. The two hydrates observed in aqueous solution are not found in the solid state. Analysis of the integrated intensity of the OH stretching band of sucrose−H2O mixtures shows that the OH vibrations in both the sucrose and the associated water are modified in the mixtures, indicating strong intermolecular interactions that influence the band intensities.
Article
A method based on factor analysis is developed that permits us to retrieve the real spectra and multiplication factors (or concentrations) of individual species in spectra of evolving complex systems with no a priori information. The application of constraints of non-negative intensities and non-negative concentrations to the matrices of abstract factors gives the unoptimized real spectra. Then searching for the most likelihood spectra by using the maximum entropy criterion gives the real spectra. Mixtures of experimental spectra are used to illustrate the method.
Article
1. The intense broad-band absorption (CA) in solutions of (NH2)SO4 and K2SO4 in anhydrous H2SO4 has been recorded by PTIR IR spectroscopy; the concentration of undissociated H2SO4, molecules decreases to a greater extent than if the acid were consumed only in the formtion of HSO4 – ions. 2. The formation is proposed of ions having a quasisymmetrical, strong hydrogen bond (HSO3O...H...OSO3H–) responsible for the CA.
Article
The ions (H2O … H … OH2)+ and (HO … H … OH)− are the simplest stable H+ and OH− hydrates in aqueous acid and base solutions, respectively. Using the attenuated total reflection method, the IR spectra of aqueous HCl and KOH solutions are obtained and the assignment of the H5O2+ and H3O2− vibrational frequencies is performed. The absorption spectrum of the OHO fragment is separated from the spectra of the solutions investigated. This spectrum exhibits a broad continuous band and two rather narrow bands at its background which are assigned to the antisymmetrical stretching vibration and to the bending vibrations of the fragment. A theoretical model is suggested which explains the origin of the continuum by a strong proton-phonon coupling. The model takes into account the large number of low-frequency vibrational modes of the system; the frequency dispersion for these modes is assumed to be sufficiently large. The continuous absorption bandshape is calculated in the Condon approximation. The theoretical absorption curve is in good agreement with experiment at reasonable values of the parameters involved.
Article
Aqueous attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of 18 aliphatic di-carboxylic acids are reported as a function of pH. The spectra show isosbestic points and intensity changes which indicate that Beer's law is obeyed, and peak frequencies lie within previously reported ranges for aqueous carboxylates and pure carboxylic acids. Intensity sharing from the symmetric carboxylate stretch is evident in many cases, so that bands which are nominally due to alkyl groups show increased intensity at higher pH. The asymmetric stretch of the HA− species is linearly related to the microscopic acidity constant of the H2A species, with σpK<0.25 log units; this relationship falls on the same line as previously observed for mono-carboxylic acids. The linear relationship applies to the acidity constant of the HA− species only when the two acid groups are well separated (>2 intervening atoms). The results suggest that aqueous ATR-FTIR may be able to estimate `intrinsic' pKa values of carboxylic acids, in addition to providing quantitative estimates of ionization.
Article
We designed an improved wedge shaped cell for measuring Lambert absorption coefficient spectra alpha(nu) of highly absorbent liquids. The design allows for accurate determination of the apex angle of the wedge, sealing the cell, and injection of the liquid without disassembling the cell. We measured alpha(nu) for water through the 500-12,500-cm(-1) wavenumber region to determine the range of alpha(nu) for which the cell provided accurate measurements. We then determined the imaginary part of the complex refractive index N(nu) = n(nu) + ik(nu) from alpha(nu) and used Kramers-Kronig methods to compute n(nu) from k(nu).
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