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Novel Functionalization of Boron-Doped Diamond (BDD) by Microwave Pulsed-Plasma Polymerized Allylamine Film
Abstract
We report the novel modification of hydrogen-terminated polycrystalline boron-doped electrode
with microwave pulsed-plasma polymerized allylamine. BDD was coated with a very thin layer
of adherent cross-linked, pinhole- and additive-free allylamine plasma polymer (PPAAm)
resistant to hydrolysis and delamination, and characterized by a high density of positively
charged amino groups. The pulsed microwave plasma was applied to improve the cross-linking
degree and bonding of the plasma polymeric films to boron-doped diamond. The amine treated
BDD films were assessed by advanced surface analytical techniques, such as XPS, FT-IR, SEM,
laser induced fluorescence and water contact angle measurements. The amine-modified Si/BDD
surface was functionalized with selected organic molecules containing carboxylic group in the
presence of coupling agents such as diisopropylcarbodiimide (DIC). The anthraquinone
derivatives Boc-Lys(AQ)-OH, and peptide anthraquinone derivatives of dendrimere were used as
electro-active agents for characterization by cyclic voltammetry (CV). The fluorescence
reference standards Rhodamine 110 and Fmoc-Trp(Boc)-OH were selected for fluorescence
studies.
... The boron level expressed as [B]/[C] ratio in the gas phase was 10,000 ppm (boron dopant concentrations 2 × 10 21 atoms cm −3 ) [39]. A more detailed description of the thin film synthesis can be found elsewhere [40,41]. Then, the electrode surface was cleaned and hydrogenated. ...
... The as-prepared BDD sample is characterized by E value of approximately 350 mV. The value is quite high taking into consideration other reported heavy boron-doped electrodes, which is due to the lack of any other electrode pretreatment procedures [41,44]. Nevertheless, the E increase resulting from the applied hightemperature treatment should be explained by the move further away from the diffusion-controlled mechanism, due to the slowing down of the charge transfer kinetics. ...
... The oxidation of BDD surface termination, occurring as a result of high-temperature treatment in air, results in the substitution of hydrogenated terminal bonds with oxygen-containing species: hydroxyl C-OH (peak at 285.6 eV), but also carbonyl >C=O (at 287.0 eV) and carboxyl COOH (at 288.7 eV) groups [41,57,61]. The XPS analyses confirmed that hydroxyl species are the dominant ones on the surface of high-temperature-treated BDD electrode, unlike other types of surface oxidation treatments (electrochemical, oxygen plasma, ozone treatment, etc.) [29]. ...
In this work, we reveal in detail the effects of high-temperature treatment in air at 600 °C on the microstructure as well as the physico-chemical and electrochemical properties of boron-doped diamond (BDD) electrodes. The thermal treatment of freshly grown BDD electrodes was applied, resulting in permanent structural modifications of surface depending on the exposure time. High temperature affects material corrosion, inducing crystal defects. The oxidized BDD surfaces were studied by means of cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM), revealing a significant decrease in the electrode activity and local heterogeneity of areas owing to various standard rate constants. This effect was correlated with a resultant increase of surface resistance heterogeneity by scanning spreading resistance microscopy (SSRM). The X-ray photoelectron spectroscopy (XPS) confirmed the rate and heterogeneity of the oxidation process, revealing hydroxyl species to be dominant on the electrode surface. Morphological tests using scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that prolonged durations of high-temperature treatment lead not only to surface oxidation but also to irreversible structural defects in the form of etch pits. Our results show that even subsequent electrode rehydrogenation in plasma is not sufficient to reverse this surface oxidation in terms of electrochemical and physico-chemical properties, and the nature of high-temperature corrosion of BDD electrodes should be considered irreversible.
... The presence of C 1s, O 1s, N 1s and V 2p in the survey scan of PS-1 (Fig. 6) confirms the presence of neat complex 1 on the polymer. The high resolution XPS spectrum of C 1s in PS-1 can be deconvoluted into three peaks due to functional groups C-C/C = C (284.3), C-N/C-Cl (286.3) and C-O (287.4) (Fig. 6b) [75][76][77]. The peak due to C-N validates the successful immobilization of ligand I onto the polymer. ...
... The k cat values for the complex 1 aligns favourably with those reported for metal complexes in prior literature. Table 2 provides a comparison of k cat values for various metal complexes previously published [75][76][77][78][79][80][81][82][83][84][85]. ...
Oxidovanadium(V) complex [VVO{Hen(3,5-dcp)4}] (where H4en(3,5-dcp)4, is a Mannich base synthesized from ethylenediamine, paraformaldehyde and 2,4-dichlorophenol) has been anchored onto chloromethylated polystyrene (PS–Cl) cross-linked with divinylbenzene to obtain [VVO{en(3,5-dcp)4}]@PS (@ refers to anchoring of complex onto polymer), a heterogeneous compound. Both of the synthesized (homogeneous as well as heterogeneous) vanadium compounds, after characterization, have been explored as biomimicking model catalysts for the type II copper site in phenoxazinone synthase. These compounds catalyze the oxidative condensation of o-aminophenol (OAP) into 2-aminophenoxazine-3-one (APX) by utilizing aqueous hydrogen peroxide in acetonitrile. Various reaction conditions like amounts of catalyst and oxidant, and temperature have been optimized to obtain maximum yield of APX. The polymer-immobilized complex demonstrates excellent catalytic activity, giving 96% yield of 2-aminophenoxazine-3-one under the optimized reaction conditions selectively. Its homogeneous analogue i.e. [VVO{Hen(3,5-dcp)4}], is also active and exhibits 83% yield. The heterogeneous catalyst i.e. [VVO{en(3,5-dcp)4}]@PS is stable, recyclable and reusable.
Graphical Abstract
... As it has been shown in the literature [9,10], an important factor in the plasma modification process is the duration of the deposition process. In order to optimize this factor, the FTO electrodes were modified using three times: 72 s, 144 s, 288 s. ...
... The above statement finds confirmation in the C1s peak analysis, where the highest share of oxidized carbon components is visible for the lowest modification time (C ox :C red ¼ 1.1:1, 0.5:1, and 0.6:1, respectively with the increase of the polymerization time). Finally, the surface chemistry after 288 s is highly resembling analogous layers reported for the modification of BDD electrodes [9]. As expected, the thinnest layer is obtained after 72 s-long PPAAm polymerization process. ...
We report here the dry, one-step, and low-temperature modification of FTO surfaces using pulsed plasma polymerization of allylamine (PPAAm). PPAAm/FTO surfaces were characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and contact angles to understand the morphological, structural, and optical properties. FTO were coated with a very thin layer of adherent cross-linked, pinhole-, and additive-free allylamine plasma polymer resistant to hydrolysis and delamination, and characterized by a high density of positively charged amino groups. Electrochemical studies revealed that PPAAm/FTO electrodes show wide range pH stability and reaction rates tuned by the duration of plasma treatment. We show how the modification of plasma treatment duration between 72 s and 288 s affects the chemical structure and thickness of the obtained modification, having a strong influence on the charge transfer kinetics. In particular, XPS revealed the occurrence of the reduction processes under long-term plasma exposure proving the need for monitoring of this key factor. This covalent immobilization of amine compounds on FTO surface using rapid process in microwave pulsed-plasma makes it a promising electrode for future applications in electrochemical biosensors and optoelectronic devices.
... Excited plasma was ignited by microwave radiation (2.45 GHz). The plasma microwave power, optimized for diamond synthesis, was kept at 1300 W (Bogdanowicz et al., 2014). The gas mixture ratio was 1% of the molar ratio of CH 4 -H 2 at a gas volume of 300 sccm of total flow rate. ...
The 21st century has already brought us a plethora of new threats related to viruses that emerge in humans after zoonotic transmission or drastically change their geographic distribution or prevalence. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first spotted at the end of 2019 to rapidly spread in southwest Asia and later cause a global pandemic, which paralyzes the world since then. We have designed novel immunosensors targeting conserved protein sequences of the N protein of SARS-CoV-2 based on lab-produced and purified anti-SARS-CoV-2 nucleocapsid antibodies that are densely grafted onto various surfaces (diamond/gold/glassy carbon). Titration of antibodies shows very strong reactions up to 1:72 900 dilution. Next, we showed the mechanism of interactions of our immunoassay with nucleocapsid N protein revealing molecular recognition by impedimetric measurements supported by hybrid modeling results with both density functional theory and molecular dynamics methods. Biosensors allowed for a fast (in less than 10 min) detection of SARS-CoV-2 virus with a limit of detection from 0.227 ng/ml through 0.334 ng/ml to 0.362 ng/ml for glassy carbon, boron-doped diamond, and gold surfaces, respectively. For all tested surfaces, we obtained a wide linear range of concentrations from 4.4 ng/ml to 4.4 pg/ml. Furthermore, our sensor leads to a highly specific response to SARS-CoV-2 clinical samples versus other upper respiratory tract viruses such as influenza, respiratory syncytial virus, or Epstein-Barr virus. All clinical samples were tested simultaneously on biosensors and real-time polymerase chain reactions.
... For example, an electrode described as Si/B-NCD-2k has a (B)/(C) ratio of 2000 ppm. The synthesis of carbon layers (BDD, CNW, and B-NCD) on the silicon/quartz glass surface, along with the selection of deposition parameters, was carried out in accordance with the procedures described in earlier works [18,25,31,33,69] by the team of Prof. Robert Bogdanowicz from the Department of Metrology and Optoelectronics from the Faculty of Electronics, Telecommunications and Informatics of the Gdańsk University of Technology. ...
The search for new electrode materials has become one of the goals of modern electrochemistry. Obtaining electrodes with optimal properties gives a product with a wide application potential, both in analytics and various industries. The aim of this study was to select, from among the presented electrode materials (carbon and oxide), the one whose parameters will be optimal in the context of using them to create sensors. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were used to determine the electrochemical properties of the materials. On the other hand, properties such as hydrophilicity/hydrophobicity and their topological structure were determined using contact angle measurements and confocal microscopy, respectively. Based on the research carried out on a wide group of electrode materials, it was found that transparent conductive oxides of the FTO (fluorine doped tin oxide) type exhibit optimal electrochemical parameters and offer great modification possibilities. These electrodes are characterized by a wide range of work and high chemical stability. In addition, the presence of a transparent oxide layer allows for the preservation of valuable optoelectronic properties. An important feature is also the high sensitivity of these electrodes compared to other tested materials. The combination of these properties made FTO electrodes selected for further research.
... Furthermore, N 1s spectra of LC-CNS@NTA showed two additional peaks at ∼398.3 and 401.2 eV, which were characteristic peaks for C−N and CN, respectively. 26 Thus, the spectroscopic characterization con-firmed the presence of graphitic carbon, imine (CN), and carboxyl groups in LC-CNS@NTA. ...
Development of metal-free, recyclable enzyme mimics is challenging and requires key chemical modifications at the molecular level. Here, nitrilotriacetic acid-functionalized carbon nanospheres (LC-CNS@NTA) were prepared from the nitrogen-rich weed Lantana camara (LC) using a simple hydrothermal reaction condition. Transmission electron microscopy (TEM) studies revealed size of ∼160 ± 20 nm for LC-CNS@NTA whereas, the same showed fluorescence emission at ∼520 nm with a ∼63% quantum yield. Furthermore, LC-CNS@NTA showed strong peroxidase (Pxrd) activity toward a wide range of substrate viz., H2O2, 3,3',5,5'-tetramethylbenzidine, and o-phenylenediamine with Km and Vmax values of ∼257 μM and 1.06 μM/s, 282 μM and 1.47 μM/s, and 270.8 μM and 1.647 μM/s, respectively. Interestingly, this also showed catalase (CAT) activity against H2O2 with Km and Vmax values of ∼0.374 μM and 1.87 μM/s, respectively. It was observed that LC-CNS@NTA could effectively reduce the oxidative stress-induced cytotoxicity of HEK293 cells via retention of mitochondrial membrane potential, prevention of lipid peroxidation and DNA damage. It was further found that LC-CNS@NTA-treated cells showed reduced level of intracellular protein carbonylation and protein aggregation. The finding of the present study is expected to pave the path for designing engineered metal-free carbon nanozyme with dual enzyme mimic activity.
... A comparison of the N 1s XPS spectra recorded inside ( Figure 2a) and outside ( Figure 2d) the wear track reveals the tribochemically induced formation of N−C bonds, as evidenced by the peak at 399.6 eV after sliding. 27,28 This peak is 10 times less intense than the Si 3 N 4 surface peak (at 397.3 eV), and therefore, the ratio of nitrogen−carbon to nitrogen−silicon bonds is about 0.1. The nitrogen−carbon signal comes either from a carbon nitride surface layer or from To better understand the chemical structure of this tribolayer and to quantify its thickness, high-resolution timeof-flight secondary ion mass spectrometry (ToF-SIMS) with a depth resolution of less than 1 nm is performed in exactly the same areas as those of previous XPS analyses of the T = 150°C wear track. ...
... The share of mixed TiO 2 -SiO 2 , SiO 2 , and TiO 2 components drops approximately by a factor of 1.5. Last, but not least, a strong signal recorded in the N1s energy range revealed the presence of the amino -NH 2 species (398.5 eV) [62,63]. The N1s signal is characterized by a complex structure, with a second, two times smaller component, which may be the effect of NH 3 + protonation or deprotonation on NH-. ...
In this paper, we described the synthesis procedure of TiO2@SiO2 core-shell modified with 3-(aminopropyl)trimethoxysilane (APTMS). The chemical attachment of Fmoc–glycine (Fmoc–Gly–OH) at the surface of the core-shell structure was performed to determine the amount of active amino groups on the basis of the amount of Fmoc group calculation. We characterized nanostructures using various methods: transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) to confirm the modification effectiveness. The ultraviolet-visible spectroscopy (UV-vis) measurement was adopted for the quantitative determination of amino groups present on the TiO2@SiO2 core-shell surface by determination of Fmoc substitution. The nanomaterials were functionalized by Fmoc–Gly–OH and then the fluorenylmethyloxycarbonyl (Fmoc) group was cleaved using 20% (v/v) solution of piperidine in DMF. This reaction led to the formation of a dibenzofulvene–piperidine adduct enabling the estimation of free Fmoc groups by measurement the maximum absorption at 289 and 301 nm using UV-vis spectroscopy. The calculations of Fmoc loading on core-shell materials was performed using different molar absorption coefficient: 5800 and 6089 dm³ × mol⁻¹ × cm⁻¹ for λ = 289 nm and both 7800 and 8021 dm³ × mol⁻¹ × cm⁻¹ for λ = 301 nm. The obtained results indicate that amount of Fmoc groups present on TiO2@SiO2–(CH2)3–NH2 was calculated at 6 to 9 µmol/g. Furthermore, all measurements were compared with Fmoc–Gly–OH used as the model sample.
... Microwave irradiation was also known to induce crystallization of metal and oxide nanoparticles in the presence of reducing agents from plant extracts [240][241][242]. Examples of indirect microwaves application in nanoparticle synthesis were microwave plasma related methods [243], which included microwave assisted spray synthesis [244], microwave plasma sintering, [245] and many personalized methods like microwave pulsed plasma polymerization [246] or microwave plasma deposition of nanoparticles on substrate [247]. ...
Hereby the possible applications of oxide nanoparticles in the cancer diagnostics and therapy are presented. Cancer diseases are nowadays one of the most common causes of death in the highly-developed countries. Discussed will be the current clinical cancer detection methods with their shortcomings. The role of nanomedicine in cancer medicine and the potential applications of nanoparticles debated in the literature will be critically evaluated. In the second part, the most common methods for the nanoparticle synthesis will be discussed. Finally, the system for cancer detection based on the enhanced permeation-retention of multimodal high-k oxide nanoparticles doped with lanthanides will be proposed for both for themagnetic resonance imaging (non-gadolinium contrast agents) and for fluorescence guided biopsy and surgery.
... The highmolecular weight HA-modified nanoparticles showed severe agglomeration (Figure 4(a) XPS. The spectrum decomposition was performed using the XPSPEAK41 program with Gaussian functions after subtraction of a Shirley background; the ratio between the Lorentzian and Gaussian functions is 60%. Figure 5 [30,31]. As the weight proportion of the oHA increased during modification, the C-N bond proportion decreased ( Figure 5(b)), and the C=O-N and C-NH 3 group proportions increased accordingly. ...
Superparamagnetic iron oxide nanoparticles (SPIONs) conjugated with hyaluronic acid (HA) functional groups have potential applications as cell targeting materials. However, SPIONs incubated with high-molecular weight HA can result in severe agglomeration. In this work, we found that when modified with degraded HA (hyaluronan oligosaccharides (oHAs)), the nanoparticles were uniformly dispersed with small hydrodynamic sizes, and the oHA-modified SPIONs exerted minimal cytotoxicity. With the same functional groups as HA, the oHA-modified SPIONs may have various biomedical applications.
... A major C1s peak appears on the XPS spectra, within the energy range characteristic for unsaturated C=C bonds (284.0 eV) as in isatin molecule. This observation comes together with the appearance of two additional peaks; first at 286.0 eV is typically observed for C-N and C=O interaction, and the latter one at 288.2 eV is characteristic for C=O in carboxyl and carbonyl species [43][44][45]. Finally, the amount of nitrogen-based on N1s spectra analysis (Fig. 4b) is said to be 6.4 at.%, while N1s peak location at 399.9 eV is characteristic to nitrogen in amine groups [46,47]. ...
Ultra-thin nanocrystalline boron-doped diamond electrodes (B:NCD) were used for the
electrochemical determination of isatin in dog urine samples using cyclic voltammetry and
square wave voltammetry in a phosphate buffer saline, pH = 7.2. No additional modification
or pretreatment of the electrode surface was required in this approach, being of high importance
for the facile detection procedure. The increase of the peak current was linearly related to the
raised concentration of isatin in phosphate buffer. The limit of isatin detection was equal to 0.2
μM and 3 μM for B:NCD and reference glassy carbon electrodes respectively. The relatively
high current sensitivities of 1.32 μAcm-2μM-1 were achieved thanks to the nanocrystalline
diamond surface. We have demonstrated that isatin could be determined at B:NCD electrode
in the complex urine matrix within the limit of detection having 1 μM along with sensitivity of
0.46 μAcm-2μM-1 without pre-treatment procedure of the analyte.
... Nowadays, the development and fabrication of electrochemical sensors require the modification of electrode's surface with the reactive molecules [1][2][3][4]. The lack of chemically reactive groups precludes the attachment of organic compounds to the surface. ...
In this work, the Mach-Zehnder interferometer was designed to monitor the electrochemical processes conducted at boron-doped diamond electrode surface. The diamond electrodes were synthesized via Microwave Plasma-Assisted Chemical Vapor Deposition on optical grade quartz glass. The achieved transmittance in working are of diamond electrodes reached 55 %. A cage system-based Mach-Zehnder interferometer was used which allowed the insertion of thin-layer electrochemical cells. Electrochemical studies were carried out in a thin-layer working cell. The application of such setup, allows to combine optical monitoring of surface of the working electrode during electrochemical measurements, electropolymerization or surface modification. The conducted investigation shows that during surface modification by melamine the phase shift is up to 0.0328 μm−1. The aforementioned set up can be applied for in situ monitoring of surface modifications with various compounds, and to detect organic substances whose oxidation or reduction products absorb onto the electrode surface.
... The BDD electrodes (attn. 10000 ppm [B]/[C] in plasma) were synthesized in MWPECVD system (SEKI Technotron AX5400S, Japan) on p-type Si wafers as reported elsewhere [32,33]. A 6 h growth period produced microcrystalline diamond of ca. 2 mm in thickness, dominated by (110) and (111) facets, containing also (100)-oriented crystals revealed by morphological investigation [27,34]. ...
The electrochemical active surface area (EASA) of polycrystalline boron-doped diamond (BDD) electrodes is heterogeneous and can be affected by numerous factors. There is a strong need for proper consideration of BDD heterogeneity in order to improve this material’s range of application in electrochemistry. Localized changes in surface termination due to the influence of oxidation agent result in increased surface resistance. The observed behavior of this characteristic feature varies among individual grains, depending on their crystallographic orientation. Still, there is not much information about this key factor in terms of its influence on the electrochemical response of BDD. In this study we compared two approaches towards BDD surface oxidation, namely: anodic polarization at potentiostatic and potentiodynamic conditions. The surface impedance measurements via Nanoscale
Impedance Microscopy (NIM) allowed the confirmation of diversified propensity for the modification of surface termination in BDD. We showed that the NIM studies provide a deep understanding on the
electrical characterization and variation of surface resistance in BDD electrodes. In order to evaluate the actual heterogeneity of electrochemical activity distribution, voltammetry, dynamic electrochemical
impedance spectroscopy (DEIS) and scanning electrochemical microscopy (SECM) studies were performed. For each investigated electrode, departure from the Randles-Sevcik equation was observed,
with its level depending on the surface heterogeneity and oxidation treatment, justifying the standardization of pre-treatment procedure and development of non-standard model for diffusion transport
in proximity of BDD electrode.
... Nanodiamonds are an allotropic form of carbon whose core consists of the sp 3 orbital crystal structure and the sp 2 phase forms most of their surface. Interestingly, it has unique characteristics, such as hardness, fine-tuning of their size distributions, emission of strong fluorescence, color centers, such as nitrogen vacancy (NV)-centers, photostability, chemical stability, small size, large surface area, high adsorption capacity, and good biocompatibility [201][202][203][204][205]. Fungi used to cause several diseases in domestic animals by producing mycotoxins. ...
Nanoscience and nanotechnology shows immense interest in various areas of research and applications, including biotechnology, biomedical sciences, nanomedicine, and veterinary medicine. Studies and application of nanotechnology was explored very extensively in the human medical field and also studies undertaken in rodents extensively, still either studies or applications in veterinary medicine is not up to the level when compared to applications to human beings. The application in veterinary medicine and animal production is still relatively innovative. Recently, in the era of health care technologies, Veterinary Medicine also entered into a new phase and incredible transformations. Nanotechnology has tremendous and potential influence not only the way we live, but also on the way that we practice veterinary medicine and increase the safety of domestic animals, production, and income to the farmers through use of nanomaterials. The current status and advancements of nanotechnology is being used to enhance the animal growth promotion, and production. To achieve these, nanoparticles are used as alternative antimicrobial agents to overcome the usage alarming rate of antibiotics, detection of pathogenic bacteria, and also nanoparticles being used as drug delivery agents as new drug and vaccine candidates with improved characteristics and performance, diagnostic, therapeutic, feed additive, nutrient delivery, biocidal agents, reproductive aids, and finally to increase the quality of food using various kinds of functionalized nanoparticles, such as liposomes, polymeric nanoparticles, dendrimers, micellar nanoparticles, and metal nanoparticles. It seems that nanotechnology is ideal for veterinary applications in terms of cost and the availability of resources. The main focus of this review is describes some of the important current and future principal aspects of involvement of nanotechnology in Veterinary Medicine. However, we are not intended to cover the entire scenario of Veterinary Medicine, despite this review is to provide a glimpse at potential important targets of nanotechnology in the field of Veterinary Medicine. Considering the strong potential of the interaction between the nanotechnology and Veterinary Medicine, the aim of this review is to provide a concise description of the advances of nanotechnology in Veterinary Medicine, in terms of their potential application of various kinds of nanoparticles, secondly we discussed role of nanomaterials in animal health and production, and finally we discussed conclusion and future perspectives of nanotechnology in veterinary medicine.
... 14 (ii) B:NCD has a hole diffusion coefficient (2-30 cm 2 s À1 ) that is eight orders of magnitude higher than that for NiO (4 Â 10 À8 cm 2 s À1 ). 15 (iii) Diamond surfaces, and Hterminated ones in particular, can be readily functionalized through diazonium chemistry, [16][17][18] photochemical graing, 19,20 or plasma treatment. 21,22 In a subsequent step, light-harvesting molecules can be covalently attached to the surface, leading to the formation of carbon-carbon bonds between the dye and the electrode. [23][24][25][26] These covalent bonds are stronger than the coordination bonds formed with NiO and should lead to improved stability of the diamond-dye interface. ...
Improving the performance of p-type photoelectrodes represents a key challenge toward significant advancement in the field of tandem dye-sensitized solar cells. Herein, we demonstrate the application of boron-doped nanocrystalline diamond (B:NCD) thin films, covalently functionalized with a dithienopyrrole–benzothiadiazole push–pull chromophore, as alternative photocathodes. First, a primary functional handle is introduced on H-terminated diamond via electrochemical diazonium grafting. Afterwards, Sonogashira cross-coupling and Cu(I) catalyzed azide–alkyne cycloaddition (CuAAC) reactions are employed to attach the chromophore, enabling the comparison of the degree of surface functionalization and the importance of the employed linker at the diamond-dye interface. X-ray photoelectron spectroscopy shows that surface functionalization via CuAAC results in a slightly higher chromophore coverage compared to the Sonogashira cross-coupling. However, photocurrents and photovoltages, obtained by photoelectrochemical and Kelvin probe measurements, are approximately three times larger on photocathodes functionalized via Sonogashira cross-coupling. Surface functionalization via Sonogashira cross-coupling is thus considered the preferential method for the development of diamond-based hybrid photovoltaics.
... For the functionalization of H-terminated diamond surfaces, a two-step approach is generally required, wherein functional groups are initially introduced via spontaneous or electrochemical diazonium grafting of an (in situ generated) aryl diazonium salt, 18−20 photochemical grafting under illumination with UV light (254 nm), 21,22 or plasma treatment of the surface. 23,24 Subsequently, the freshly introduced functional handles can be employed to attach a variety of (bio)molecules utilizing several coupling reactions, such as EDC-NHS, 25 thiol− ene/yne, 26 Cu-catalyzed azide−alkyne cycloaddition, 27−29 or Pd-catalyzed Suzuki cross-coupling. 16,30,31 By employing a combination of diazonium grafting and Pdcatalyzed Suzuki cross-coupling, organic molecules can be readily attached to the diamond surface via stable carbon− carbon bonds in a fully conjugated fashion. ...
Well-defined covalent surface functionalization of diamond is a crucial, yet non-trivial, matter because of diamonds intrinsic chemical inertness and stability. Herein, we demonstrate a two-step functionalization approach for H-terminated boron-doped diamond thin films, which can lead to significant advances in the field of diamond hybrid photovoltaics. Primary diamond surface functionalization is performed via electrochemical diazonium grafting of in situ diazotized 4-iodoaniline. The freshly grafted iodophenyl functional moieties are then employed to couple a layer of thiophene molecules to the diamond surface via two well-established Pd-catalyzed cross-coupling reactions, i.e. Stille and Sonogashira. X-ray photoelectron spectroscopy analysis indicates a dense coverage and successful cross-coupling in both cases. However, we find that the Stille reaction is generally accompanied with severe surface contamination, in spite of process optimization and thorough rinsing. Sonogashira cross-coupling on the other hand provides a clean, high quality functionalization over a broad range of reaction conditions. The protocols employing Sonogashira reactions thus appear to be the method of choice toward future fabrication of high-performance dye-functionalized diamond electrodes for photovoltaic applications.
... The presence of B−N bonds, in the form of peak at 398.0 eV, has not been confirmed. 42,43 The concentrations of both oxygen and nitrogen increased with increasing B dopant concentration, which suggests a higher reactivity of the electrode. However, boron itself was not directly detected due to insufficient detection sensitivity of XPS system. ...
The growth of B-CNW with different boron doping levels controlled by the [B]/[C] ratio in plasma, and the influence of boron on the obtained material’s structure, surface morphology, electrical properties and electrochemical parameters, such as -ΔE and k°, were investigated. The fabricated boron-doped carbon nanowalls exhibit activity towards ferricyanide redox couple, reaching the peak separation value of only 85 mV. The flatband potential and the concentration of boron carriers were estimated in the B-CNW samples using the Mott-Schottky relationship. It was shown that the vertically oriented carbon planes are characterized by p-type conductivity and very high hole-acceptor concentration (3.33×1023 cm-3 for a highly doped sample), which provides high electrical conductivity. The enhanced electrochemical performance of B-CNWs electrodes is an advantageous feature that can be applied in ultrasensitive detection or energy storage devices.
... The boron-doped diamond electrodes (attn. 10,000 ppm [B]/[C] in plasma) were synthesized in an MWPECVD system (SEKI Technotron AX5400S, Japan) on p-type Si wafers as reported elsewhere [39,40]. A 6 h growth period produced microcrystalline diamond of ca. 2 μm in thickness, dominated by (110) and (111) facets, containing also (100) oriented crystals revealed by morphologic investigation [41][42][43][44]. ...
... The PE CVD process was also usefully applied for fabrication of polymerized thin films such as allylamine (PPAAm), which can be used to prepare direct modification or activation of various optical surfaces [45]. Films are highly transparent and FT-IR shows that the molecular structure of the plasma deposited polymer film reproduces the monomer structure H 2 C═CH-CH 2 -NH 2 . ...
Plasma-based techniques are widely applied for well-controlled deposition, etching
or surface functionalization of a number of materials. It is difficult to imagine fabrication of novel microelectronic and optoelectronic devices without using plasma-enhanced deposition
of thin films, their selective etching or functionalization of their surfaces for subsequent selective binding of chemical or biological molecules. Depending on the process parameters, i.e., generator frequency
and power, composition of gases
, pressure, temperature, and applied substrates, different effects of the process can be obtained. The chapter discusses current trends in application of plasma-based techniques for fabrication of novel optical sensing
devices. Fabrication of materials with different structure (from amorphous to crystalline, porous, and multilayers), optical properties (absorption, refractive index
), and surface activity, as well as their processing are reviewed. Application of the plasma
methods enhancing sensing properties of various optical fiber sensing
structures, namely long-period gratings, intermodal interferometers based on photonic crystal fiber, sensing structures based on lossy mode resonance or stacks of nano-films are given as examples and are discussed.
... Deconvolution of XPS spectra was carried out using earlier studies on similar electrodes. 23 C1s spectra contained four peaks (see Fig. 1 Table I, and Fig. S3 in the supplementary material) 20 and two peaks located at binding energies of $284.2 and $285.0 eV contributed to sp 2 C-C and sp 3 C-C bond atoms, respectively. 24 The peaks at 285.8 eV corresponds to sp 2 C ¼ N but may as well be interpreted as C-O bonds due to small energy difference between those peaks. ...
The influence of N-2 concentration ( 1%-8%) in CH4/H-2/N-2 plasma on structure and optical properties of nitrogen doped diamond ( NDD) films was investigated. Thickness, roughness, and optical properties of the NDD films in the VIS-NIR range were investigated on the silicon substrates using spectroscopic ellipsometry. The samples exhibited relatively high refractive index ( 2.6+/-0.25 at 550nm) and extinction coefficient ( 0.05+/-0.02 at 550nm) with a transmittance of 60%. The optical investigation was supported by the molecular and atomic data delivered by Raman studies, bright field transmission electron microscopy imaging, and X-ray photoelectron spectroscopy diagnostics. Those results revealed that while the films grown in CH4/H-2 plasma contained micron-sized diamond grains, the films grown using CH4/H-2/(4%)N-2 plasma exhibited ultranano-sized diamond grains along with n-diamond and i-carbon clusters, which were surrounded by amorphous carbon grain boundaries. Published by AIP Publishing.
... Among those, the sp 2 carbon peak is located at 284.6 eV (width = 1.43 eV) while the peak assigned to 285.4 eV (width = 2.27 eV) stems from the alkyl chain (C−C, C−H) of TFAAA. 18 The peaks located at 288.3 eV (width = 1.86 eV) and 292.5 eV (width = 1.20 eV) are indication of carbonyl (CO) and CF 3 groups, respectively. 6 This carbonyl is related to the trifluoroacetamide (TFA) protecting group. ...
As a potential material for biosensing applications, gallium nitride (GaN) films have attracted remarkable attention. In order to construct GaN biosensors, a corresponding immobilization of biolinkers is of great importance in order to render a surface bioactive. In this work, two kinds of n-alkenes with different carbon chain lengths, namely allylamine protected with trifluoroacetamide (TFAAA) and 10-aminodec-1-ene protected with trifluoroacetamide (TFAAD), were used to photochemically functionalize single crystalline GaN films. The successful linkage of both TFAAA and TFAAD to the GaN films is confirmed by time of flight secondary ion mass spectrometry (ToF-SIMS) measurement. With increased UV illumination time, the intensity of the secondary ions corresponding to the linker molecules initially increases and subsequently decreases in both cases. Based on the SIMS measurements, the maximum coverage of TFAAA is achieved after 14 h of UV illumination, while only 2 h are required in case of TFAAD to reach the situation of a fully covered GaN surface. This finding leads to the conclusion that the reaction rate of TFAAD is significantly higher compared to TFAAA. Measurements by atomic force microscopy (AFM) indicate that the coverage of GaN films by a TFAAA layer leads to an increased surface roughness. The atomic terraces, which are clearly observable for the pristine GaN films, disappear once the surface is fully covered by a TFAAA layer. Such TFAAA layers will feature a homogeneous surface topography even for reaction times of 24. In contrast to this, TFAAD shows strong cross-polymerization on the surface, this is confirmed by optical microscopy. These results demonstrate that TFAAA is a more suitable candidate as biolinker in context of the GaN surfaces due to its improved controllability.
Diamond nanomaterials are renowned for their exceptional properties, which include the inherent attributes of bulk diamond. Additionally, they exhibit unique characteristics at the nanoscale, including high specific surface areas, tunable surface structure, and excellent biocompatibility. These multifaceted attributes have piqued the interest of researchers globally, leading to an extensive exploration of various diamond nanostructures in a myriad of applications. This review focuses on non‐zero‐dimensional (non‐0D) diamond nanostructures including diamond films and extended diamond nanostructures, such as diamond nanowires, nanoplatelets, and diamond foams. It delves into the fabrication, modification, and diverse applications of non‐0D diamond nanostructures. This review begins with a concise review of the preparation methods for different types of diamond films and extended nanostructures, followed by an exploration of the intricacies of surface termination and the process of immobilizing target moieties of interest. It then transitions into an exploration of the applications of diamond films and extended nanostructures in the fields of biomedicine and electrochemistry. In the concluding section, this article provides a forward‐looking perspective on the current state and future directions of diamond films and extended nanostructures research, offering insights into the opportunities and challenges that lie ahead in this exciting field.
Photocatalytic N2 fixation is a complex reaction, thereby prompting researchers to design and analyze highly efficient materials. Herein, one-pot hydrothermal Bi2WO6-BiOCl (BW-BiOCl) heterojunctions were synthesized by varying the molar ratio of tungsten: chlorine precursor. Major morphological transformations in BiOCl were observed wherein it turned from thick sheets ∼230 nm in pure BiOCl to ∼30 nm in BW-BiOCl. This was accompanied by extensive growth of {001} facets verified from X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) analyses. A p-n heterojunction was formed between Bi2WO6 and BiOCl evidenced via photoluminescence (PL), time-resolved photoluminescence (TRPL), photocurrent response, and electrochemical impedance spectroscopy (EIS) analyses. The formation of heterojunction between Bi2WO6 and BiOCl led to the reduction of the work function in the BW-BiOCl 0.25 hybrid confirmed via ultraviolet photoelectron spectroscopy (UPS) analysis. BW-BiOCl 0.25 could produce ammonia up to 345.1 μmol·L-1·h-1 owing to the formation of a robust heterojunction with an S-scheme carrier transport mechanism. Recycle tests resulted in no loss in N2 reduction activities with post-catalytic analysis, showcasing the high stability of the synthesized heterojunction. Novel performance was owed to its excellent chemisorption of N2 gas on the heterojunction surface verified by N2-temperature programmed desorption (TPD). BW-BiOCl 0.25 also displayed a superior rate constant of 3.03 × 10-2 min-1 for 90 min CIP degradation time, higher than pristine BiOCl and Bi2WO6. Post-photocatalytic Fourier transform infrared (FTIR) spectroscopy of BW-BiOCl 0.25 revealed the presence of C-H stretching peaks in the range of 2850-2960 cm-1 due to adsorbed CIP and methanol species in CIP degradation and N2 fixation, respectively. This also confirmed the enhanced adsorption of reacting species onto the heterojunction surface.
Bioremediation of real-time petroleum refining industry oily waste (PRIOW) is a major challenge due to the poor emulsification potential and oil sludge disintegration efficiency of conventional bioamphiphile molecules. The present study was focused on the design of a covalently engineered supramolecular bioamphiphile complex (SUBC) rich in hydrophobic amino acids for proficient emulsification of hydrocarbons followed by the concomitant degradation of total petroleum hydrocarbons (TPH) in PRIOW using the hydrocarbonoclastic microbial bio-formulation system. The synthesis of SUBC was carried out by pH regulated microbial biosynthesis process and the yield was obtained to be 450.8 mg/g of petroleum oil sludge. The FT-IR and XPS analyses of SUBC revealed the anchoring of hydrophilic moieties of monomeric bioamphiphilic molecules, resulting in the formation of SUBC via covalent interaction. The SUBC was found to be lipoprotein in nature. The maximum loading capacity of SUBC onto surface modified rice hull (SMRH) was achieved to be 45.25 mg/g SMRH at the optimized conditions using RSM-CCD design. The SUBC anchored SMRH was confirmed using SEM, FT-IR, XRD and TGA analyses. The adsorption isotherm models of SUBC onto SMRH were performed. The integrated approach of SUBC-SMRH and hydrocarbonoclastic microbial bio-formulation system, emulsified oil from PRIOW by 92.86 ± 2.26% within 24 h and degraded TPH by 89.25 ± 1.75% within 4 days at the optimum dosage ratio of SUBC-SMRH (0.25 g): PRIOW (1 g): mass of microbial-assisted biocarrier material (0.05 g). The TPH degradation was confirmed by SARA fractional analysis, FT-IR, ¹H NMR and GC-MS analyses. The study suggested that the application of covalently engineered SUBC has resulted in the accelerated degradation of real-time PRIOW in a very short duration without any secondary sludge generation. Thus, the SUBC integrated approach can be considered to effectively manage the hydrocarbon contaminants from petroleum refining industries under optimal conditions.
Two mononuclear cis‐[MoVIO2] complexes with Schiff base ligands, H4L¹ (I) and H4L² (II) (derived from the condensation of 3,5‐diformyl‐4‐hydroxybenzoic acid with isonicotinoylhydrazide and nicotinoylhydrazide) were synthesized using [MoVIO2(acac)2] (Hacac=acetylacetone) and ligand in 1 : 1 molar ratio in methanol. The obtained homogeneous complexes [MoVIO2(H2L¹)]n (1) and [MoVIO2(H2L²)(MeOH)] (2) were supported on titania functionalized with amine group (APTMS‐TiO2) to obtain heterogeneous complexes [MoVIO2(HL¹)(MeOH)]@APTMS‐TiO2 (3) and [MoVIO2(HL²)(MeOH)]@APTMS‐TiO2 (4), respectively. All the isolated complexes were characterized by various spectral techniques (FT‐IR, UV‐visible, ¹H and ¹³C NMR), elemental (CHN) and thermogravimetric analyses; heterogeneous complexes were additionally characterized by transmission electron microscopy, diffuse reflectance, X‐ray photoelectron spectroscopy and Powder‐X‐ray diffraction studies. The single‐crystal X‐ray diffraction analysis of complexes 1 and 2 confirms the distorted octahedral geometry for both complexes, where ligands coordinate to the metal centre through Ophenolate, Nazomethine, and Oenolate. Complex 1 has a 3D polymeric structure, where the sixth site of one molecule of Mo is coordinated to the pyridinic nitrogen of the other molecule while 2 is monomeric. These complexes are explored as bio‐mimicking model catalysts for the type II copper site in phenoxazinone synthase. These complexes catalyze the oxidative condensation of o‐aminophenol (OAP) into 2‐aminophenoxazine‐3‐one (APX) utilizing aq. H2O2 in the MeCN‐MeOH mixture. For complexes 1 and 2, the value of turnover number (kcat) obtained for phenoxazinone synthase‐like activity is 2.14 and 1.76 h⁻¹, respectively. Under the optimized reaction parameters, the yield of 2‐aminophenoxazine‐3‐one (APX) obtained is 97 and 92 % for complexes 3 and 4, respectively.
Ceramic-supported-polymeric (CSP) composite membranes combine the benefits of robust ceramic support with tunable surface properties of polymeric active layer. The present work reports the fabrication of novel CSP composite nanofiltration membranes wherein surface ionization of the membrane active layers has been carried out by a facile process of chelating copper ions with the crosslinked polyethyleneimine polymer matrix of membrane top layer. Different concentrations of copper chloride solutions were used and their effect on membrane surface properties was investigated using EDX, XPS and AFM analyses. Performance of the membranes in removal of both cationic and anionic heavy metals, namely, Ni(II), Cd(II), Pb(II), Zn(II), As(V) and Cr(VI) from aqueous solution was studied. Excellent removal (> 95%) of all the heavy metals and optimum flux was achieved in case of GPCu0.5 membrane (surface modified with 0.5 wt% copper chloride solution). No significant decrease in flux and rejection rate of the membrane during 10 h high pressure (8 bar) operation suggested longevity of the membrane. The slow release of copper ions indicated the much-expected anti-biofouling nature of the membrane. Appreciable rejection behavior of the copper ion enhanced CSP composite membrane towards multiple heavy metals demonstrates its potential for practical water treatment application.
In the present study, we examined a novel functionalised magnetic nanoparticles Fe3O4@SiO2-Nn as a nano adsorbent for binding of Cd²⁺, Pb²⁺, Cu²⁺ ions in an aqueous solution. First, we obtained the nanoparticles functionalised with various carbon chains containing different number of amino groups: (3-amino)propyltriethoxysilane (Fe3O4@SiO2-N1), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (Fe3O4@SiO2-N2) and N¹-(3-trimethoxysilylpropyl)diethylenetriamine (Fe3O4@SiO2-N3). In the next step, we conducted their characterisation using SEM, TEM, FT-IR, and XPS methods.
The detection of Cd²⁺, Pb²⁺, Cu²⁺ metal ions was performed under optimised experimental conditions using DPASV and HDME techniques. Using these methods we conducted the Cd²⁺, Pb²⁺, Cu²⁺ binding comparison in 4.5 μM concentration with 4 mg of Fe3O4@SiO2-Nn. Obtained results show that the adsorption rate of each ion differs due to the nanoparticles modification.
The highest Pb²⁺ binding capacity was achieved using Fe3O4@SiO2-N1 and Fe3O4@SiO2-N2. The smallest binding capacity was observed for Cd²⁺ ions by Fe3O4@SiO2-N2 and Fe3O4@SiO2-N1.
The Cd²⁺ biding was not observed for both Fe3O4@SiO2-N2 and Fe3O4@SiO2-N3 nanoparticles. Additionally, Pb²⁺ was not bound by Fe3O4@SiO2-N3. The research results show that the Fe3O4@SiO2-N3 nanoparticles bind copper ions with high selectivity.
For the first time we performed the adsorption-desorption experiments using DPASV to prove the Cu²⁺ binding activity of Fe3O4@SiO2-N3 nanoparticles. Obtained results indicate that examined nanoparticles show strong binding capability. Additionally, we obtained 99.9% recovery of Cu²⁺ ions.
Novel amine functionalized composite membranes were prepared over tubular ceramic substrate using facile dip-coating and cross-flow filtration approach. The two fabricated membranes, P-60S and P-60S-EDTA with polyethyleneimine (PEI) and EDTA-modified PEI as functional layers respectively, were characterized in terms of EDX, FTIR, XPS, FESEM, AFM and contact angle analyses which confirmed their stable physical and chemical structure for use in high pressure application. Clean water permeability and MWCO study revealed the superior permeability and rejection efficiency of the P-60S-EDTA compared to the P-60S membrane. Incorporation of bulky EDTA molecules in the membrane functional layer simultaneously decreased pore size and increased membrane hydrophilicity. The removal of As(V), Cr(VI) and Cu(II) heavy metals by both membranes were found to be highly pH dependent and overall rejection improved in case of P-60S-EDTA membrane [99.82% for Cu(II), 96.75% for As(V) and 97.22% for Cr(VI)]. Interestingly, rejection of As(V) and Cr(VI) was significantly improved in presence of Cu(II) due to volume resistance provided by EDTA-Cu(II) complex towards the passage of other heavy metal ions. Excellent stability of P-60S-EDTA membrane in continuous operation of 36 hours in both ideal and practical water environment suggests its promising application in real field heavy metal contaminated waste water treatment.
While positively charged nanomaterials induce cytotoxicity in many organisms, much less is known about how the spatial distribution and presentation of molecular surface charge impacts nanoparticle-biological interactions. We systematically functionalized diamond nanoparticle surfaces with five different cationic surface molecules having different molecular structures and conformations, including four small ligands and one polymer, and we then probed the molecular-level interaction between these nanoparticles and bacterial cells. Shewanella oneidensis MR-1 was used as a model bacterial cell system to investigate how molecular length and conformation of cationic surface charges influence their interactions with the Gram-negative bacterial membranes. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) demonstrate the covalent modification of nanoparticle surface with the desired cationic organic monolayers. Surprisingly, bacterial growth-based viability (GBV) and membrane damage assays both show only minimal biological impact by the NPs functionalized with short cationic ligands within the concentration range tested. Yet NPs covalently linked to a cationic polymer induce strong cytotoxicity, including reduced cellular viability and significant membrane damage at the same concentration of cationic groups. Transmission electron mi-croscopy (TEM) images of these NP-exposed bacterial cells show that NPs functionalized with cationic polymers induce significant membrane distortion and production of outer membrane vesicles, while NPs bearing short cationic ligands exhibit only weak membrane association. Our results demonstrate that the spatial distribution of molecular charge plays a key role in controlling the interaction of cationic nanoparticles with bacterial cell membranes and subsequent biological impact. Nanoparticles functionalized with ligands having different lengths and conformations can have large differences in interactions even while having nearly identical zeta potentials. While zeta potential is a convenient and commonly used measure of nanoparticle charge, it does not capture essential differences in molecular-level nanoparticle properties that control their biological impact.
Diamond is a highly attractive material for photoelectrochemical applications such as dye-sensitized solar cells or photocatalysis because of its high chemical stability, high conductivity upon doping and the ease by which synthetic diamond thin films or nanostructures can be grown on various substrates. For these applications in particular, a well-defined surface functionalization is a crucial, yet non-trivial matter. In the first part of this review we therefore provide an extensive overview of the surface chemistry of doped and intrinsic diamond thin films. Different techniques to alter the surface termination of freshly grown diamond electrodes are illustrated and compared. Next, the subsequent functionalization steps to form stable covalent bonds between (linker) molecules and the diamond surface are discussed, with special emphasis on photochemical and (electro)chemical diazonium grafting. Several strategies to fabricate macromolecular brushes via surface initiated and direct polymerization techniques are proposed as well. In the second part, the photocurrent generation of dye-sensitized boron-doped diamond electrodes is compared and the influence of the employed chromophores, functionalization strategy, surface contamination and doping concentrations is analyzed. To conclude, the emerging photocatalytic applications of diamond are highlighted, such as the reduction of carbon monoxide, ammonia synthesis and water splitting.
The impact of the surface modification on the subcellular distribution of nanoparticles in the brain remains elusive. The nanoparticles prepared by conjugating poly (ethylene glycol) (PEG) and maleic anhydride (Mal) coated superparamagnetic iron oxide nanoparticles (Mal‐SPIONs) with bovine serum albumin (BSA/Mal‐SPIONs), and with Arg‐Gly‐Asp (RGD) peptide (RGD/Mal‐SPIONs) were injected into the rat substantia nigra. Observation of TEM (transmission electron microscopy) samples obtained 24 h after perfusion showed that abundant RGD/Mal‐SPIONs accumulated in the myelin sheath, dendrites, axon terminals and mitochondria and on cell membranes in the brain tissue near the injection site. For rats injected with BSA/Mal‐SPIONs, a few nanoparticles accumulated in the myelin sheath, axon terminals, endoplasmic reticulum，mitochondria, golgi and lysosomes of neurons and glial cells while least SPIONs in rats injected with Mal‐SPIONs were found. TEM pictures showed some Mal‐SPIONs were expelled out of the brain. RGD/Mal‐SPIONs diffused extensively to the thalamus, frontal cortex, temporal lobe, olfactory bulb and brain stem after injection. Only a few BSA/Mal‐SPIONs diffused to the afore‐mentioned brain areas. This work reveals different surface modifications on the iron oxide nanoparticles play crucial roles in their distribution and diffusion in the rat brains.
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This article reports the use of pulsed remote Ar‐O2 microwave plasma assisted chemical vapor deposition with an −NH2 containing organosilicon precursor ((3‐Aminopropyl)triethoxysilane: APTES). It is shown that modifying the plasma pulses duration (ton) and the plasma off duration (toff) allows to finely tune the deposited layer composition. In addition, the results of this work demonstrate that an important film growth occurs during toff, which results in an increased −NH2 density. Besides, high resolution MALDI‐ORBITRAP Mass spectrometry analysis clearly points out that APTES oligomers up to eight base units, including silsesquioxanes (cages), and cyclosiloxanes (rings) molecules with intact −NH2 groups are embedded into the as grown pp‐APTES thin film.
In this work we present a simple and efficient method of nitrogen plasma modification of carbon nanotubes
(CNTs). The process allows for treatment of the nanotubes in the form of powder with quite a high yield
(65 mg of CNTs per hour). The modified carbon nanotubes contain approx. 3.8% nitrogen, mostly in the
pyridinic form. Plasma treated CNTs exhibit better dispersibility in water and higher electric capacitance
than pristine CNTs. Modified CNTs are a proper component of novel nanocomposites based on the
conducting polymer poly(3,4-ethyleneidoxythiophene). Electrodeposited thin layers of the
nanocomposite exhibit improved electrochemical properties (higher capacitance, better stability, lower
resistance, faster diffusion) compared to the pure polymer layers.
The microstructure and corrosion behavior of carbon steel (CSA516) and ferritic (SS410) and austenitic (SS304L) stainless steels were studied and compared. Corrosion tests were carried out in 0.5 M NaCl solutions. Rates of corrosion were monitored based on weight loss, Tafel extrapolation and linear polarization resistance (LPR) methods. Rates of corrosion were ranked following the order: CSA516 ≫ SS410 > SS304L. The impact of p-Nitrophenyl phosphate disodium salt (NPP) on the corrosion rate of CSA516 was also studied using Tafel polarization and LPR measurements. Optical microscopy (OM), scanning electron microscopy (SEM/EDX), and X-ray photoelectron spectroscopy (XPS) were employed to assess the chemical compositions and morphologies of the corroded and inhibited surfaces. FT-IR analyses were also performed to assess the functional groups of the inhibited sample in a comparison with NPP itself. XPS and FT-IR studies revealed the presence of phosphate groups originating from tested inhibitor, thus proving formation of the protective layer on the steel surface. The microstructural and defect investigations of as-polished, corroded, and inhibited CSA516 samples were also carried out using positron annihilation lifetime (PAL) and positron annihilation Doppler broadening (PADB) techniques. Experimental findings revealed that NPP acted as an efficient mixed-type inhibitor with anodic predominance. It reached about 97% inhibition efficiency at a low concentration of 0.02M.
The influence of N2 concentration (1%–8%) in CH4/H2/N2 plasma on structure and optical properties of nitrogen doped
diamond (NDD) films was investigated. Thickness, roughness, and optical properties of the NDD films in the VIS–NIR range were investigated on the silicon substrates using spectroscopic ellipsometry. The samples exhibited relatively high refractive index (2.6 ± 0.25 at 550 nm) and extinction coefficient (0.05 ± 0.02 at 550 nm) with a transmittance of 60%. The optical investigation was supported by the molecular and atomic data delivered by Raman studies, bright field transmission electron microscopy imaging, and X-ray photoelectron spectroscopy diagnostics. Those results revealed that while the films grown in CH4/H2 plasma contained micron-sized diamond grains, the films grown using CH4/H2/(4%)N2 plasma exhibited ultranano-sized diamond grains along with n-diamond and i-carbon clusters, which were surrounded by amorphous carbon grain boundaries.
Fabrication processes of thin boron-doped nanocrystalline diamond (B-NCD) films on silicon-based micro- and nano-electromechanical structures have been investigated. B-NCD films were deposited using microwave plasma assisted chemical vapour deposition method. The variation in B-NCD morphology, structure and optical parameters was particularly investigated. The use of truncated cone-shaped substrate holder enabled to grow thin fully encapsulated nanocrystalline diamond film with a thickness of approx. 60 nm and RMS roughness of 17 nm. Raman spectra present the typical boron-doped nanocrystalline diamond line recorded at 1148 cm−1. Moreover, the change in mechanical parameters of silicon cantilevers over-coated with boron-doped diamond films was investigated with laser vibrometer. The increase of resonance to frequency of over-coated cantilever is attributed to the change in spring constant caused by B-NCD coating. Topography and electrical parameters of boron-doped diamond films were investigated by tapping mode AFM and electrical mode of AFM–Kelvin probe force microscopy (KPFM). The crystallite–grain size was recorded at 153 and 238 nm for boron-doped film and undoped, respectively. Based on the contact potential difference data from the KPFM measurements, the work function of diamond layers was estimated. For the undoped diamond films, average CPD of 650 mV and for boron-doped layer 155 mV were achieved. Based on CPD values, the values of work functions were calculated as 4.65 and 5.15 eV for doped and undoped diamond film, respectively. Boron doping increases the carrier density and the conductivity of the material and, consequently, the Fermi level.
This work describes the electrochemical method of boron-doped diamond (BDD) modification by poly-melamine to obtain organic films. The detection of adenine, guanine and caffeine was carried out by differential pulse wave voltammetry (DPV). The poly-melamine modified B-NCD electrodes exhibit excellent activity towards the electrochemical oxidation of all examined analytes. The poly-melamine modified BDD electrodes in all measurements exhibit a larger peak current and are more sensitive compared to the unmodified BDD electrodes. The detection limit for adenine, guanine and caffeine using poly-melamine modified BDD electrodes was found with 0.2 mM, 0.02 nM and 0.4 mM, respectively. Moreover, the double-stranded (ctDNA), and single stranded DNA from calf thymus (ssDNA) was detected by DPV.
A dry two-step plasma process is introduced for the fabrication of particulate surfaces showing negative charges over a wide range of pH. Plasma polymerized thiophene (PPT) was initially deposited onto silica particles using an inductively coupled plasma polymerization reactor fitted with a rotating barrel. Sulfur-functionalized particles were further chemically modified through an oxidative air or water plasma treatment. Wide ranges of plasma specific energies (0.06-2.4 kJ cm−3) and treatment times (5-60 minutes) were employed to manipulate the surface chemistry, hydrophobicity and surface charge of the silica particles. Surface chemistry of the modified silica particles was studied using X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectroscopy (ToF-SIMS). Changes in hydrophobicity and surface charge of the modified particles were quantified via Washburn capillary rise measurements and electrokinetic analysis, respectively. Plasma treatment of PPT coated particles resulted in homogenous formation of -SOx(H) functionalities such as sulfonate (SO3−), sulfonic acid (SO3H), and sulfate (SO42−) on surfaces. Such changes in surface chemistry significantly decreased the zeta potential and isoelectric point of the particles as well as their degree of hydrophobicity. In comparison to air plasma, water plasma was found to be a better candidate for the treatment of PPT coated particles as it produced surfaces with lower zeta potentials and isoelectric points. Our introduced solvent-free approach is applicable for the modification of almost any other particles regardless of their shape and surface chemistry. Such surface engineered particles could be utilized as protein detectors/adsorbents, solid-state catalysts, and heavy metal removal agents.
The novel microwave pulsed-plasma based method for modification of the hydrogen-terminated polycrystalline boron-doped diamond (BDD) with thin film of polymerised allylamine (PPAAm) is reported. Modified BDD surface is resistant to hydrolysis and delamination and characterized by a high density of positively charged amino groups. The pulsed microwave plasma was applied to improve the cross-linking degree and bonding of the plasma polymeric films to boron-doped diamond. The primary amino groups of the amine-modified Si/BDD surface were coupled with antraquinone derivatives as model electroactive compounds.
Synthetized thin BDD-PPAAm films were investigated with X-Ray photoelectron spectroscopy (XPS), laser induced fluorescence (LIF) and Fourier Transform Infrared Spectroscopy (FT-IR). The FT-IR studies confirm that the molecular structure of deposited layer reproduces the monomer structure with partial transformation of amino groups into amide and nitrile. XPS results show that PPAAm film on Si/BDD electrode is electrochemically stable within range of polarization potentials between -1.1 and +1.1 V. The fluorescence properties of the PPAAm modified BDD surface makes its promising for the application as a sensors with optical readout. At the same time the electrochemical stability of the surface investigated over the wide potential range makes it an ideal for electrochemical sensors.
Development of the optoelectronic system for monitoring of diamond/DLC (Diamond-Like-Carbon) thin films growth during μPA ECR CVD (Microwave Plasma Assisted Electron Cyclotron Resonance Chemical Vapour Deposition) process is described. The multi-point Optical Emission Spectroscopy (OES) and Raman spectroscopy were employed as non-invasive optoelectronic tools. Dissociation of H2 molecules, excitation and ionization of hydrogen atoms as well as spatial distribution of the molecules became subjects of the OES investigation. The most significant parameters of the deposited film like molecular composition of the film (ratio of diamond sp3, graphite sp2 and amorphous phases), presence of defects and rate of the film growth can be investigated by means of Raman spectroscopy. Modular Raman system for in-situ monitoring of the film growth, equipped with fibre probes, was designed. Investigation with use of optoelectronic tools provides important data about CVD process progress as well as enables optimization of DLC synthesis parameters and improvement of synthesized films quality.
Boron-doped diamond (BDD) thin films, as one kind of electrode materials, are superior to conventional carbon-based materials including carbon paste, porous carbon, glassy carbon (GC), carbon nanotubes in terms of high stability, wide potential window, low background current, and good biocompatibility. Electrochemical biosensor based on BDD electrodes have attracted extensive interests due to the superior properties of BDD electrodes and the merits of biosensors, such as specificity, sensitivity, and fast response. Electrochemical reactions perform at the interface between electrolyte solutions and the electrodes surfaces, so the surface structures and properties of the BDD electrodes are important for electrochemical detection. In this paper, the recent advances of BDD electrodes with different surfaces including nanostructured surface and chemically modified surface, for the construction of various electrochemical biosensors, were described.
Electrochemical reduction of phenyl diazonium salts in acetonitrile at boron-doped diamond electrodes yielded covalent bonding of aromatic groups to the sp 3 carbon surface. Diamond surfaces modified with nitrophenyl, trifluoromethylphenyl, and nitroa- zobenzene showed strong X-ray photoelectron spectroscopy (XPS) signals for surface nitrogen or fluorine, which were stable to exposure to air or solvents. Raman spectra of chemisorbed nitroazobenzene on boron-doped diamond were obtained, and were sim- ilar to those observed for derivatized glassy carbon. Estimated surface coverages of 50-70% of a compact monolayer were calcu- lated from XPS spectra, indicating that the coverage is too high to be attributed solely to modification of sp 2 carbon impurities or boron dopant. The high coverages of covalently bonded molecules on diamond achievable by diazonium reduction imply that a vari- ety of surface functionalities may be introduced on the normally unreactive diamond surface. © 1999 The Electrochemical Society. S1099-0062(98)12-080-1. All rights reserved.
The system based on spatially resolved optical emission spectroscopy dedicated for in situ diagnostics of plasma assisted CVD processes is presented in this paper. Measurement system coupled with chemical vapour deposition chamber by dedicated fiber-optic paths enables investigation of spatial distribution of species densities (Hx, H+, CH, CH+) during chemical vapour deposition process. Experiments were performed for a various gas inlet configuration at range of microwave power up to 800 W. Spatially resolved optical spectroscopy results showed that inlet configuration based on injecting hydrogen in ECR region and methane in substrate area is the most efficient for H+ and CH3+ excitation. The designed prototype of the spatially resolved optical spectroscopy system enables the high-sensitivity measurements of concentration of the species in the microwave plasma and can be used for optimisation of diamond-like carbon synthesis.
We report on the electronic and optical properties of boron-doped nanocrystalline diamond (NCD) thin films grown on quartz substrates by CH(4)/H(2) plasma chemical vapor deposition. Diamond thin films with a thickness below 350 nm and with boron concentration ranging from 10(17) to 10(21) cm(-3) have been investigated. UV Raman spectroscopy and atomic force microscopy have been used to assess the quality and morphology of the diamond films. Hall-effect measurements confirmed the expected p-type conductivity. At room temperature, the conductivity varies from 1.5x10(-8) Omega(-1) cm(-1) for a nonintentionally doped film up to 76 Omega(-1) cm(-1) for a heavily B-doped film. Increasing the doping level results in a higher carrier concentration while the mobility decreases from 1.8 down to 0.2 cm(2) V(-1) s(-1). For NCD films with low boron concentration, the conductivity strongly depends on temperature. However, the conductivity and the carrier concentration are no longer temperature dependent for films with the highest boron doping and the NCD films exhibit metallic properties. Highly doped films show superconducting properties with critical temperatures up to 2 K. The critical boron concentration for the metal-insulator transition is in the range from 2x10(20) up to 3x10(20) cm(-3). We discuss different transport mechanisms to explain the influence of the grain boundaries and boron doping on the electronic properties of NCD films. Valence-band transport dominates at low boron concentration and high temperatures, whereas hopping between boron acceptors is the dominant transport mechanism for boron-doping concentration close to the Mott transition. Grain boundaries strongly reduce the mobility for low and very high doping levels. However, at intermediate doping levels where hopping transport is important, grain boundaries have a less pronounced effect on the mobility. The influence of boron and the effect of grain boundaries on the optoelectronic properties of the NCD films are examined using spectrally resolved photocurrent measurements and photothermal deflection spectroscopy. Major differences occur in the low energy range, between 0.5 and 1.0 eV, where both boron impurities and the sp(2) carbon phase in the grain boundaries govern the optical absorption.
A systematic study on the morphology and electronic properties of thin heavily boron-doped nanocrystalline diamond (NCD) films is presented. The films have nominally the same thickness (≈150 nm) and are grown with a fixed B/C ratio (5000 ppm) but with different C/H ratios (0.5–5%) in the gas phase. The morphology of the films is investigated by x-ray diffraction and atomic force microscopy measurements, which confirm that lower C/H ratios lead to a larger average grain size. Magnetotransport measurements reveal a decrease in resistivity and a large increase in mobility, approaching the values obtained for single-crystal diamond as the average grain size of the films increases. In all films, the temperature dependence of resistivity decreases with larger grains and the charge carrier density and mobility are thermally activated. It is possible to separate the intra- and intergrain contributions for resistivity and mobility, which indicates that in these complex systems Matthiessen's rule is followed. The concentration of active charge carriers is reduced when the boron-doped NCD is grown with a lower C/H ratio. This is due to lower boron incorporation, which is confirmed by neutron depth profiling.
AbstractIn this work, the synthesis of various thiol-functionalized anthraquinone compounds is presented. The studied compounds were
characterized by mass spectrometry and the main fragmentation pathways are discussed. The compounds studied formed stable
self-assembled monolayers (SAMs) in the gold surface. The parameters for the reduction processes in the gold surface of the
studied new anthraquinones were determined by cyclic voltamperometry tests.
Graphical abstract
KeywordsAnthraquinones–Mass spectrometry–Cyclic voltamperometry
A single wavelength ellipsometry and cyclic voltammetry measurements were simultaneously used for the investigation of oxide
growth on copper in 0.1M NaOH solution. These investigations were part of joint research of electric and physical properties
of cuprous and cupric oxide during layer formation and growth. This type of joint impedance and ellipsometric study has not
been performed before. In this paper, authors discuss composition of multilayer film structure using various models and fitting
methods enabling interpretation of multilayer oxides structure formation during passivation process. It is shown that implementation
of effective medium approximation allows to obtain an accurate model fitting, using Levenberg–Marquardt optimization algorithm
and mean square error.
Surfaces and interfaces of hydrogen-terminated diamonds are reviewed. The control and preparation of diamond surfaces have been greatly advanced by the recent progress in epitaxial growth, which is discussed in Section 2. In Section 3, the hydrogen-terminated surfaces of (1 1 1) and (0 0 1) are explained in terms of types of hydrides, surface reconstructions, stability of surface CH bonds, and surface p-type conduction. In Section 4, metal/diamond contacts are reviewed. Schottky and ohmic properties are discussed on the basis of hydrogen termination, surface treatment, metal electronegativity, interfacial reaction, and surface states. The first application of hydrogen-terminated surfaces as electron devices is presented for the metal-semiconductor field effect transistor.
The aim of this review is to summarize the most relevant contributions in the development of electrochemical sensors based on carbon materials in the recent years. There have been increasing numbers of reports on the first application of carbon derived materials for the preparation of an electrochemical sensor. These include carbon nanotubes, diamond like carbon films and diamond film-based sensors demonstrating that the particular structure of these carbon material and their unique properties make them a very attractive material for the design of electrochemical biosensors and gas sensors.
This paper is concerned with the study of the influence of electrochemical pre-treatments on the behavior of highly boron doped diamond electrodes. Anodic and cathodic preconditioning, performed during 10 s either with 10− 4 A/cm− 2 (10− 3 C cm− 2) or 10− 1 A/cm− 2 (1 C cm− 2), has been studied. Cyclic voltammetry at as-deposited, anodically and cathodically treated electrodes, in presence of 2 redox couples serving as electrochemical probes is analyzed in the light of the surface characterization given by XPS chemical analysis. Ce4+/3+ redox couple in 0.5 M H2SO4 medium and Fe(CN)63−/4− redox couple in 0.1 M KOH medium, have been studied before and after the different treatments. The results of Mott–Schottky plots and current voltage curves are reported and show that the electrochemical response of BDD electrodes is very dependent on the current density involved in the electrochemical preconditioning. The modification of surface bond termination – either hydrogen or oxygen – studied by XPS analyses is also strongly dependent on electrochemical pre-treatment. In particular, it is evidenced that the most important conversion of surface functionalities from hydrogen to oxygen is obtained when the anodic treatment is performed with the smallest current density. Finally, a correlation between surface terminations and charge transfer is evidenced.
Surface functionalization of diamond with amine groups and immobilization of gold nanoparticles (AuNPs) on boron doped nanocrystalline diamond (BDND) films deposited by microwave plasma chemical vapor deposition were investigated. Hydrogen-terminated BDND film surfaces were activated through bonding with allylamine molecules under UV light irradiation. The resulting diamond surfaces were characterized by using X-ray photoelectron spectroscopy and water contact angle measurement. The amine groups were successfully bonded covalently on the BDND diamond surface via a direct photochemical reaction with allylamine. Gold nanoparticles with the average size of 15 nm were then further self-assembled on the amine-terminated diamond surface by immersing the film surface into the gold colloidal solution, and a dense and well distributed AuNPs array in two dimensions with controlled density was obtained. Standard Rhodamine 6G probe molecules were used to access the surface enhanced Raman scattering (SERS) activity of the prepared new SERS substrate based on AuNPs modified BDND film. The results indicated that such AuNPs modified BDND film showed an excellent and stable SERS activity in the low concentration detection of R6G due to the electromagnetic enhancement mechanism.
Nanoscale diamond has recently received considerable attention due to the various possible applications such as luminescence imaging, drug delivery, quantum engineering, surface coatings, seeding etc. For most of these fields a suitable surface termination and functionalization of the diamond materials are required. In this feature article we discuss recent achievements in the field of surface modification of nanoscale diamond including the establishment of a homogeneous initial surface termination, the covalent and non-covalent immobilization of different functional moieties as well as the subsequent grafting of larger (bio)molecules onto previously functionalized nanodiamond.
New, electroactive, positively charged peptides consisting of either L‐lysine or L‐arginine and containing one or two anthraquinone units in the structure were synthesized. Electrochemical properties of the synthesized compounds were examined by cyclic‐, normal pulse‐ and microelectrode voltammetries. Spectroscopic and potentiometric methods were used to characterize such properties of the new peptides as: pK a, diffusion coefficients and formal potentials in water and DMSO. The obtained results show that the number of noninteracting, anthraquinone units incorporated into one peptide chain leads to proportional increase of height of voltammetric and spectroscopic signals.
The H-terminated polycrystalline diamond thin film surface is photochemically functionalized using allylamine. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) aided by principal components analysis (PCA) is then employed to systematically elucidate (i) the photochemical grafting of trifluoroacetamide group protected allylamine (TFAAA) onto the diamond thin film surface and (ii) the deprotection of the amine group. PCA of the SIMS shows that the diamond surface is fully covered by TFAAA after 24 h of UV illumination. SIMS spectra (in the high mass range) show that TFAAA cross-polymerizes on the diamond surface before the whole surface is covered by TFAAA. PCA of the SIMS also shows that the deprotection reaction follows approximately an exponential law with a time constant of 1 h. Additionally, the unchanged CN-intensity in the deprotection step shows that the allylamine linkage to diamond is stable. A shadow mask was employed during the photochemical grafting of allylamine, leaving the masked region unfunctiona-lized. The SIMS mapping shows high intensities and homogeneous distribution of CN-in the region which is UV illuminated. On the basis of the overall SIMS analysis a modified chain reaction grafting model which illustrates a competition between TFAAA bonding and its cross-polymerization is discussed.
In this study the efficiency of electrochemical oxidation of aromatic pollutants, such as reactive dyes, at boron-doped diamond on silicon (Si/BDD) electrodes was investigated. The level of [B]/[C] ratio which is effective for the degradation and
mineralization of selected aromatic pollutants, and the impact of [B]/[C] ratio on the crystalline structure, layer conductivity and
relative sp3/sp2 coefficient of a BDD electrode were also studied. The thin film microcrystalline electrodes have been deposited on highly doped silicon substrates via MW PE CVD. Si/BDD electrodes were synthesized for different [B]/[C] ratios of the gas phase.
Mechanical and chemical stability of the electrodes was achieved for the microcrystalline layer with relatively high sp3/sp2 band
ratio. Layer morphology and crystallite size distribution were analyzed by SEM. The resistivity of BDD electrodes was studied using four-point probe measurements. The relative sp3/sp2 band ratios were determined by deconvolution of Raman and X-ray photoelectron spectra. The efficiency of degradation and mineralization of the reactive azo dye rubin F-2B was estimated based on
the absorbance measurements at 545 nm. The influence of commonly used electrolytes NaCl and Na2SO4 on the dye removal
efficiency was also investigated. The results suggest that, in general, the oxidation occurs indirectly at the anode through generation of hydroxyl radicals •OH, which react with the dye in a very fast and non-selective manner. In NaCl electrolyte the dye was also
decomposed by more selective, active chlorine species (Cl2, HOCl). However the efficiency of this process in BDD depended on
the electrode's doping level. Higher amounts of dopant on the surface of BDD resulted in the higher efficiency of dye removal in both electrolytes.
The surface bond structure and electronic surface barrier in electrolytes were analysed for fluorinated boron-doped single crystal diamond. The diamond surface was exposed to a CF4 RF-plasma combined with in-situ pre-heating in ultra-high vacuum to remove adsorbates. This treatment resulted in full surface coverage by mixed carbon–fluorine functionalities of 2nm in thicknesses and possibly with cross-linked or branched structures, leaving no traces of carbon-oxygen groups and non-diamond carbon phase, as determined by high-resolution X-ray photoemission spectroscopy. The capacitance-voltage, impedance spectroscopy and redox characteristics of the fluorinated diamond were investigated in various electrolytes. The analysis of data showed that electronic barrier at the fluorinated surface was close to zero at equilibrium, meaning no surface depletion of the boron-doped diamond. In comparison, the surface barrier of identical oxygen-terminated diamond was approx. 1.6eV using the same evaluation methods. The low surface barrier of the fluorinated surface remained stable after anodic polarisation and did not depend on pH or ion species.
In this work, we have used X-ray photoelectron spectroscopy (XPS) to investigate the nature of surface adsorbed species and their sensitivity to the boron concentration [B] in two sets of as-grown diamond films: homoepitaxial {111} and polycrystalline. These sets cover each one at least three of the four doping ranges: low doping (5 x 10(16)<[B] <1.5 x 10(19) cm(-3)), high doping (1.5 x 10(19)<[B] <3 x 10(20) cm(-3)), heavy doping (3 x 10(20)<[B]<2 x 10(21) cm(-3)), and phase separation ([B]>2 x 10(21) cm(-3)). The results are compared to those we have previously obtained on (100) homoepitaxial films in the same doping ranges. A detailed description of both the nature and the relative concentrations of the main surface chemical species on every set of films is reported. Besides the usual CHx bonds on the diamond surface, the following oxygen-related groups: Ether (C-O-C), hydroxyl (C-OH, only on polycrystalline films), carbonyl (>C=O) and carboxyl (HO-C=O) have been found on the surface of grown diamond films, upon spontaneous oxidation under air (no oxidation treatment has been applied). The evolution of each surface chemical group according to the boron concentration in the films is.
It was demonstrated that an atmospheric pressure dielectric barrier glow discharge system is a powerful tool for the surface functionalization of nano-crystalline diamond films. Diamond film functionalization was performed in minutes using plasma discharges generated with fluorine containing gases. The chemical bonds formed between reactive species generated in the plasma and diamond surface were confirmed by FTIR and XPS analysis. Following plasma treatment, XPS analysis revealed a high concentration of F on the diamond surface, nearly 50 atomic percent. FTIR analysis revealed the presence F-bands related to CF3 (CF2) stretching vibrations and symmetric and asymmetric CF2 vibrations. It was concluded that atmospheric pressure dielectric barrier glow discharge is a highly effective means to fluorinate diamond surfaces within a modest time.
Due to its surface properties, especially the presence of abundant amine groups, pulsed-plasma polymerized allylamine (PPAa) is used to manufacture biosensor and modify surface of metallic biomaterials. In the present study, PPAa films on 316L medical stainless steel are prepared by pulsed radio frequency (RF) plasma polymerization using allylamine as a precursor under different duty cycles. The effect of the pulsed duty cycles on the composition, structure, surface morphology, wettability and mechanical properties of PPAa films are investigated by Fourier transform infrared (FTIR) spectroscopy, laser Raman spectra, X-ray photoelectron spectroscope (XPS), atom force microscope (AFM), contact angle measurement, nanoscratch test and substrate straining method. All results of FTIR, XPS and Raman indicate that there are more amine groups from allylamine monomer on the 20/80 film fabricated by 20% duty cycle. The wettability of the 20/80 film is higher than that of 20/30 film prepared using 40% duty cycle. AFM micrographs demonstrate no remarkable differences in the morphological characteristics, but grain size of 20/30 film is larger than that of 20/80 film. The critical force of 20/80 film is about 71.86mN, higher than that of 20/30 film and has a better scratch resistance. It is estimated that the mechanical properties of the plasma polymerization are different.
Several possibilities exist to produce a modified polymer surface with a high density of only one sort of functional group such as: (i) the plasma grafting of unfragmented monomer molecules and their polymerization forms OH, NH2, COOH groups, etc. in concentrations of approximately 25 groups per 100 C atoms; (ii) selective plasma bromination provides 10–25 CBr groups; (iii) the plasma oxidation of polymer surfaces in an O2 plasma followed by the chemical reduction of all O-containing groups to OH groups by diborane, vitride™ (Na complex) or LiAlH4 yields 9–14 OH groups per 100 carbon atoms; and (iv) the grafting of spacers with different endgroups onto OH or CBr groups produces 7–10 spacer molecules/100 C. This work was focused on the formation of thin plasma deposited polymer layers with a maximum of (homo)functional groups and with a minimum of chemical irregularities using the pulsed plasma technique. The monomers were allylalcohol, allylamine, acrylonitrile and acrylic acid. The further intent was to study the interactions of functional groups (OH, COOH, NH2) and deposited metals (Cr, Al, Ti). It was expected that more basic (NH2), weakly basic or neutral (OH) or more acidic (COOH) groups would show different interactions and chemical reactions with metal atoms.
The chemical reaction of a hydrogenated diamond surface with the radical initiator benzoyl peroxide was performed in order to investigate the reactivity of the diamond surface. It was found that the hydrogen atoms on the diamond surface are abstracted by the radical species generated from benzoyl peroxide. The reaction rate was calculated from the experimental data. The hydrogen abstracted diamond surface reacts with radical species generated from the benzoyl peroxide, not with the solvent.
Continuous wave and pulsed plasma polymerization coatings of allylamine were investigated for antibody immobilization as a function of plasma power, monomer pressure and treatment time, and duty cycle. Conditions were optimized by evaluating the surface amine density of plasma polymer coated samples before and after aging in dry ethanol for 3 hrs. In addition, plasma polymer coatings were characterized by contact angle analyzer, α-step, and FT-IR/ATR. The continuous wave plasma polymerization provided amine density of 4.8 molecules/nm2 at the optimum condition of 20 W, 1 min, and 60 mTorr, while the pulsed plasma polymerization coating resulted in further increased amine density to 5.2 molecules/nm2 at the duty cycle of 60/100.
Summary A synthesis ofl-Nɛ-(9,10-dioxo-9,10-dihydroanthracen-1-yl)-lysine [Lys(AQN)], the dabcyl-like chromophore, and its derivatives useful in peptide
chemistry is described. Nα-tert-butoxycarbonyl derivative of the title compound was obtained in a good yield using aromatic nucleophilic substitution reaction.
In this form, or after conversion to the Nα-fluorenylmethoxycarbonyl derivative, it can be directly used in the solid phase peptide synthesis using either Boc- or Fmoc-strategy.
The problem of obtaining the infrared spectrum of a molecular monolayer adsorbed on a bulk metal is discussed. The intensity of an infrared absorption band in radiation reflected from the surface is calculated for (a) various optical constants of the adsorbed layer and the metal, (b) various thicknesses of the adsorbed layer, (c) various angles of incidence, and (d) both states of polarization of the incident radiation. The absorption factor for infrared radiation polarized parallel to the plane of incidence typically has a peak at an incident angle of about 88°, where the absorption is 5000 times greater than at normal incidence. The absorption of a thin layer by the reflection technique, at optimum conditions, is calculated to be about 25 times greater than by transmission through the unsupported film at normal incidence.
Total photoyield experiments are applied to characterize p-, intrinsic, and n-type diamond with hydrogen-terminated surfaces. On all hydrogen-terminated samples a photoelectron threshold energy of 4.4 eV is detected which is discussed in detail in this letter. We attribute this threshold to the energy gap between the valence-band maximum and the vacuum level, which is 1.1 eV below the conduction-band minimum, and generally referred to as ”negative electron affinity” (NEA). Hydrogen terminated p-type and intrinsic diamond show a rise of secondary photoyield in the excitation regime hν>5.47 eV. However, this is not detected on n-type diamond. We ascribe this to the formation of an upward surface band bending in the vicinity of the n-type diamond surface which acts as an energy barrier for electrons.
A boron-doped diamond (BDD) sensor is proposed for effective detection of chemical oxygen demand (COD) by means of amperometric technique. Boron-doped diamond thin films, acting as active sensors, were deposited on both silicon wafer and glassy carbon (GC) substrates by microwave plasma assisted chemical vapour deposition. SEM micrographs showed that BDD–Si displays triangle-faceted crystallites ca. 0.5–3 μm in size, while BDD–GC has triangle-faceted crystallites ranging from 0.5 to 3 μm and also a small amount of square-faceted grains 0.5–1 μm in size. The structure of BDD was confirmed by broad Raman bands centred at 483 cm−1 and 1216 cm−1. Cyclic voltammograms were measured in tetrabutylammonium perchlorate/dimethyl sulfoxide solution to determine chemical oxygen demand by amperometric technique. The reduction of oxygen at boron-doped diamond predominantly involves the one electron reduction of oxygen to superoxide. The reduction of oxygen on BDD–Si and BDD–GC was found to be quasi-reversible (ΔE = 59 − 100 mV). The lowest detection limit was about 0.9 mg l−1. Two different types of electrochemical behaviour were observed at BDD–Si and BDD–GC electrodes which indicates a complexity of electroreduction of oxygen on the BDD surface
We demonstrate a facile method for the Suzuki coupling of aryl molecules on the diamond surface. This is a more versatile alternative compared to previous coupling methods based on alkene linkers because it opens up possibilities for the application of diamond in molecular electronics and photovoltaics. The diamond surface is premodified with aryldiazonium salt in order to functionalize it with aryl halide or aryl boronic acid, and these are then used as synthons in the subsequent Suzuki coupling to aryl molecules. This method is highly specific and can be used for the uninterrupted molecular conjugation of diamond to a large class of organic molecules. As a proof of concept, we also demonstrate a diamond−fullerene photocurrent converter by using Suzuki coupled oligothiophene as the conjugated linker between diamond (electron donor) and fullerene (electron acceptor).
The reaction of nanoscale diamond (ND) powder with an elemental fluorine/hydrogen mixture at temperatures varying from 150 to 470 °C resulted in the high degree of ND surface fluorination yielding a fluoro-nanodiamond with up to 8.6 at. % fluorine content. The fluoro-nanodiamond was used as a precursor for preparation of the series of functionalized nanodiamonds by subsequent reactions with alkyllithium reagents, diamines, and amino acids. The fluoro-nanodiamond and corresponding alkyl-, amino-, and amino acid-nanodiamond derivatives were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), and thermal gravimetry-mass spectrometry (TG-MS) measurements. In comparison with the pristine nanodiamond, all functionalized nanodiamonds show an improved solubility in polar organic solvents, e.g., alcohols and THF, and a reduced particle agglomeration. The developed methodology provides an efficient method for the chemical modification of nanodiamond powder, which enables a variety of engineering and biomedical applications of ND derivatives.
Interactions of dsDNA and ssDNA, at the surface of gold and silver electrodes, with three novel anthraquinone derivatives: 3-(9′,10′-dioxo-9′,10′-dihydro-anthracen-1-yl)-7,11-di(carboxymethyl)-3,7,11-triazatridecanedioic acid, (AQ-1); 1-(9′,10′-dioxo-9′,10′-dihydro-anthracen-1yl)-9-carboxymethyl-5-methyl-1,5,9-triazaundecanoicacid, (AQ-2); and N-(2-(9,10-dioxo-9,10-dihydro-anthracen-1-ylamino)ethyl)-2-(1,4,10,13-tetraoxa-7,16-diazacyclooctadecan-7-yl)acetamide, (AQ-3) are studied. These derivatives are well soluble in water and phosphate buffer solutions. The square wave voltammetric behavior of these redox indicators is described and the parameters of interactions with DNA are reported. It is also pointed out that these compounds can be employed as the hybridization indicators. The difference in the binding ability of the particular redox indicator to single and double stranded DNA can be used for the detection of the complementary nucleic acids.
Primary amine‐based plasma polymer films (NH 2 ‐PPF) were synthesized using plasma polymerization of allylamine in continuous wave (CW) and pulsed radio‐frequency (RF) modes. Plasma chemistry, studied by residual gas analysis mass spectrometry, revealed that the precursor fragmentation is a function of the equivalent power ( P eq ) dissipated in the discharge, independently of the plasma mode used. X‐ray photoelectron spectroscopy combined with time‐of‐flight secondary ion mass spectrometry suggests as the precursor fragmentation in the plasma increases: (i) a decrease of the primary amine concentration in the NH 2 ‐PPF (% NH 2 ) and (ii) an increase of the cross‐linking degree. For a given P eq , similar to the precursor fragmentation in the plasma, the NH 2 ‐PPF characteristics were found to be independent of the plasma mode used. Therefore, the main advantage of using pulsed RF processes over CW ones is the possibility to work at very low P eq which enables low precursor fragmentation, optimization of % NH 2 , and reduction of the film cross‐linking degree. The chemical composition and the cross‐linking degree of the NH 2 ‐PPF synthesized by allylamine plasma polymerization can thus be tailored by adjusting the equivalent RF power injected in the plasma.
magnified image
Low-pressure downstream microwave plasma was used to deposit thin water resistant PPAAm and PPAAc films on titanium substrates. Film stability against dissolution was tested under sonication in ultrapure water. Variation of duty cycle on mean power was applied to evaluate the sensitivity of film properties on plasma conditions. Strong cross-linked and therewith water resistant PPAAm and PPAAc films correlate with a relatively low but for biomedical applications sufficient density of functional groups. Furthermore, some similarity exists between process parameter and dissolution stability of deposited plasma polymer films prepared by microwave and reported for radio frequency plasmas.
Highly boron-doped diamond (BDD) electrodes were modified covalently with tyrosinase for the determination of estrogenic phenol derivatives. BDD was anodically polarized for the introduction of hydroxyl groups onto its surface, then treated with (3-aminopropyl)triethoxysilane and finally coated with a tyrosinase film cross-linked with glutaraldehyde. The modified electrodes responded amperometrically to phenol derivatives including estrogenic derivatives, bisphenol-A and 17β-estradiol, at −0.3 V versus Ag ∣ AgCl. Interference from direct reduction of oxygen at the electrode surface was almost negligible because the overpotential for the oxygen reduction at BDD was greater than those for most conventional electrode materials. The electrodes were applied to a flow injection system, and the lower detection limit for bisphenol-A was 10−6 M. The stability and proper sampling interval were also studied.
The use of square wave voltammetry in conjunction with a boron-doped diamond electrode for the analytical determination of pentachlorophenol is described. After optimization of the experimental conditions, that model molecule was analyzed in pure and natural waters using a Britton–Robinson buffer (pH=5.5) as the supporting electrolyte. Oxidation occurs at 0.80 V vs. Ag/AgCl in a two-electron process controlled by adsorption of the species. The detection limits obtained were 5.5 in pure water and 15.5 μg l−1 for polluted water taken from a local creek. The combination of square wave voltammetry and diamond electrodes is an interesting and desirable alternative for analytical determinations.
Oxygen-containing functional groups can be introduced onto the surface of polycrystalline boron-doped diamond (BDD) electrodes by either anodic polarization or oxygen plasma treatment. Of these, the hydroxyl groups are of particular interest and can be studied specifically by means of specific chemical modification with 3-aminopropyltriethoxysilane (APTES). The modification of the surface hydroxyl groups with APTES accelerates the [Fe(CN)(6)](3-/4-) redox reaction, compared to the retardation by the oxidized surface. These changes can be explained in terms of changes in the electrostatic interaction between the surface functional groups and the [Fe(CN)(6)](3-/4-) anion. In particular, electrostatic attraction between [Fe(CN)(6)](3-/4-) and protonated amino groups at the APTES-treated surfaces should be responsible for the acceleration. These results, as well as those obtained in contact angle measurements and X-ray photoelectron measurements, indicate that hydroxyl groups are generated on the oxidized BDD surfaces and that they can be modified with silane coupling agents for introduction of various functionalities onto the BDD electrode surface. (C) 2001 The Electrochemical Society.
This paper aims to discuss and review developments in plasma surface modification techniques which have been seen over the past few years, with particular emphasis on low energy or soft plasma assisted surface polymerisation processes. While early work focussed mainly on protective coatings and surface activation, the advancements in microtechnology in the 1980s followed by those in nanotechnology in the 1990s and 2000s have resulted in new challenges for surface processing and surface modification processes. The latest advancements in plasma polymer chemistry have shown tremendous potential for the synthesis of reasonably well defined molecular structures with a high retention of functional groups. Some of the latest achievements and newest insights into the behaviour of such deposits in a liquid environment will be discussed, with a particular focus on bio‐nanotechnological applications. Utilising novel approaches in surface and interface analysis, it will be shown that plasma polymers can be tailored to have considerable elasticity with reversible swelling characteristics, offering a three‐dimensional interface for biomolecular immobilisation procedures in a liquid environment.
SPR data suggesting the elastic and reproducible swelling and shrinking of pp‐allylamine under a humid nitrogen environment.
magnified image SPR data suggesting the elastic and reproducible swelling and shrinking of pp‐allylamine under a humid nitrogen environment.
Functionalization of diamond surfaces holds considerable promise from both fundamental and applied research aspects. This
review summarizes briefly the state of the art of chemical, photochemical and electrochemical strategies for the grafting
of different organic functionalities on diamond. Depending on the sought-after application and the desired physical property
of diamond, halogenated, aminated, carboxylated and oxidized diamond surfaces have been proposed. After a brief introduction,
the review is primarily divided into two parts, presenting chemical functionalisation strategies used on oxygen-terminated
diamond, followed by methods used for the formation of C–C, C–X and C–N bonds on hydrogen-terminated diamond.
The photochemical attachment of 10-amino-dec-1-ene molecules protected with trifluoro acetamide acid group (“TFAAD”) on hydrogen terminated single crystalline CVD diamond, using a high-pressure mercury lamp with a peak emission around 250 nm, is described and characterized by XPS measurements. Angular resolved XPS experiments reveal oriented molecular bonding on diamond with protecting amide groups at the top. The time dependence of photoattachment follows an exponential law, with a time constant of only 1.7 h due to spin-coating of TFAAD. Based on total photoyield spectroscopy (TPYS) and spectrally resolved photoconductivity (SPC) data, measured on high quality single crystalline diamond, we introduce a model where valence-band electrons are optically excited with energies of 4.7 to 5.2 eV into empty states of TFAAD molecules. This transition is stimulated by the negative electron affinity of H-terminated diamond, which shifts the photochemical reaction window of diamond below its optical gap (5.47 eV) into a regime where commercially available UV light sources emit and organic molecules like TFAAD are still transparent.
The effect of surface pre-treatment on the electrochemical response of boron-doped diamond (BDD) electrodes is reported. Initially, several examples from published works illustrate the dramatic changes observed when a cathodic polarisation is applied before measurements instead of the classically adopted anodic treatment. In particular, electroanalytical determinations of pesticides in pure and contaminated waters could only be possible after holding the BDD electrode at −3.0 V versus Ag/AgCl for 30 min. Cyclic voltammetry of well-known reversible systems such as K4Fe(CN)6 and ferrocene in aqueous solutions rendered the expected behaviour after the cathodic pre-treatment while for the usual anodic treatment considerable distortions were recorded. Electrochemical impedance spectroscopy carried out in the presence and in the absence of the mentioned electroactive species confirmed the previously observed differences. Nyquist plots showed that in both cases the resistance associated to a high-frequency element diminishes from over 300 to about 4 Ω cm2 when a cathodic pre-treatment replaces the anodic pre-treatment. Moreover, Mott–Schottky plots in the absence of electroactive species revealed that the flat-band potential decreases by ca. 250 mV when measurements are carried out after the cathodic pre-treatment. All these effects could be explained in terms of the presence of a discontinuous passive layer on the BDD surface but they still require further studies for a definite conclusion.
This paper reports on direct amination of hydrogen-terminated polycrystalline boron doped electrode. The technique consists of NH3 plasma treatment of hydrogenated diamond substrate to generate surface terminal amino groups. The aminated diamond surface was further investigated for its ability to bind gold nanoparticles. Homogeneous and well-distributed gold nanoparticles were obtained by simple exposure of the amine-terminated surface to an aqueous solution of gold colloid. The resulting surfaces were characterized using X-ray spectroscopy (XPS), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The presence of gold nanoparticles led to more reversible electron transfer process on the modified electrode.
A method for the simultaneous determination of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) in food was developed using square-wave voltammetry (SWV). The determination of these phenolic antioxidants was carried out using a cathodically pre-treated boron-doped diamond electrode (BDD) and an aqueous-ethanolic (30% ethanol, v/v) 10 mmol L−1 KNO3 solution (pHcond. 1.5) as supporting electrolyte. In the SWV measurements using the BDD electrode, the oxidation peak potentials of BHA and BHT present in binary mixtures were separated by about 0.3 V. The attained detection limits for the simultaneous determination of BHA and BHT (0.14 and 0.25 μmol L−1, respectively) are lower than the ones by voltammetric techniques reported in the literature. The proposed method was successfully applied in the simultaneous determination of BHA and BHT in food products, with results similar to those obtained using a high-performance liquid chromatography method, at a 95% confidence level.
The activity of diamond electrodes depends on the chemical state of the diamond surface, and the present work is focussed on understanding how chemical changes either produced in situ electrochemically, or by ex situ plasma treatments, influence the electrochemical properties. Conductive boron-doped diamond electrodes were produced by depositing adherent boron-doped diamond films on tungsten substrates using a hot filament reactor and were characterised by Raman spectroscopy, scanning electron microscopy (SEM), high-resolution X-ray photoelectron spectroscopy (XPS) and electrochemical methods. In order to produce electrochemically induced surface modifications, anodic and cathodic polarisation experiments were performed in an aqueous 0.2 M phosphate buffer solution (pH=2). The surface composition of the electrode, as determined by ex situ high-resolution XPS measurements, could be linked to the electrochemical performance of diamond film electrodes. The extent to which changes in surface composition and electrode performance can be controlled and reversed by suitable plasma treatments is explored.
Here we present data on growth of thin nanocrystalline diamond (NCD) layers on silicon and glass substrates by microwave plasma-enhanced chemical vapor deposition. The typical NCD layer thickness is below 500 nm with a typical grain size about 50 nm. NCD films are optically transparent, have a smooth surface and a low background photoluminescence. We have applied a radio-frequency (RF) plasma discharge in vaporized silane coupling agent N-(6-aminohexyl) aminopropyl trimethoxysilane to successfully functionalize the NCD surface with the primary amino group NH2 as confirmed by using fluorescamine-in-acetone spray as a fluorescence marker.
Chemical modification of diamond powder surfaces was performed using chlorine chemisorption as an intermediate. We found OH, NH, and CF groups on the diamond surface. Chemisorbed species on the diamond powder surface were characterized by diffuse reflectance IR Fourier-transform spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption spectroscopy. Hydrogen chemisorbed on the diamond surface is abstracted by chlorine above 250 °C, followed by the chemisorption of chlorine. Chlorine desorbs thermally from the diamond surface at approximately 300 °C. Hydroxyl groups are produced by treatment of the chlorinated diamond with water vapor at room temperature. Amino groups are produced by treatment of chlorinated diamond with ammonia at 425 °C. CF groups are produced by treatment of chlorinated diamond with CHF3 at 600 °C. Chlorine can easily chemisorb onto the diamond surface and easily desorb from the diamond surface. Using the chlorinated surface as an intermediate state, it is possible further to modify chemically the diamond surface.
A novel bio-sensing platform is introduced by combination of a) geometrically controlled DNA bonding using vertically aligned diamond nano-wires and b) the superior electrochemical sensing properties of diamond as transducer material. Ultra-hard vertically aligned diamond nano-wires are electrochemically modified to bond phenyl linker-molecules to their tips which provide mesospacing for DNA molecules on the transducer. The nano-wires are generated by reactive ion etching of metallically boron doped atomically smooth single crystalline CVD diamond. Surface properties are characterized by atomic force, scanning electron and scanning tunneling microcopy. Electro- and bio-chemical sensor properties are investigated using cyclic and differential pulse voltammetry as well as impedance spectroscopy with Fe(CN)63-/4- as redox mediators which reveal sensitivities of 2 pM on 3 mm2 sensor areas and superior DNA bonding stability over 30 hybridization/denaturation cycles. The fabrication of “all diamond” ultra-micro-electrode (UME) arrays and multi-gene sensors are discussed taking into account the unique properties of diamond.
A novel and robust amperometric enzyme electrode for the detection of glucose has been constructed by immobilizing glucose oxidase (GOD) on a boron-doped diamond (BDD) electrode with a cross-linking technique. Cyclic voltammograms were used to characterize the enzyme electrode. The response was evaluated with respect to the enzyme amount on the electrode and the concentration of BSA used in the cross-linking reagent. Linear calibration curve was obtained for glucose over the concentration range up to 35 mM in phosphate buffer, with the lowest experimental value measured being 0.5 mM.
Differently deposited amino functionalized surfaces were compared regarding their physico-chemical surface properties in connection with cell biological response. The nitrogen containing coatings were prepared on polished titanium alloy substrates by microwave or radio frequency discharges using allylamine and ethylenediamine as precursors, respectively, or by means of radio frequency magnetron sputtering of nylon 6.6 under N(2)/H(2) 1:1 gas mixture. The chemical composition of the deposited films was determined by FT-IR and XPS analyses. Closed pinhole-free polymer films resistant to hydrolysis and delamination were detected in most cases. Advantageous medium hydrophilicities exist. The density of primary amino groups NN(2)/C differs on plasma polymerized allylamine (2.5%), and plasma polymerized ethylenediamine (3.7%) from the value on plasma sputtered nylon films in N(2)/H(2) 1:1 atmosphere (7.2%), determined after preparation. The positively charged surfaces improve adhesion and spreading of MG-63 osteoblastic cells as initial cellular effect. Furthermore, it could be demonstrated that a direct correlation does not exist between the densities of primary amino groups and an enhanced cell growth. In fact, not only the primary amino groups but also other nitrogen-functional groups as e.g. acid amides or imides play a role for initial cell functions. All examined plasma polymer coatings enable the cells to literally melt into the structure of the titanium alloy substrate. The edges of the cells can hardly be distinguished from the surface. (C) 2011 Elsevier B.V. All rights reserved.