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Scheme of the formation of the structure of a silica surface ( ≡ Si -OH silanol groups): (a) condensation polymerization and (b) rehydroxylation.
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The physicochemical properties of amorphous silica precipitated from a hydrothermal solution were studied. Low-temperature
nitrogen adsorption in conjunction with the BET method was used to determine the specific surface area of this silica. Based
on thermogravimetry data, the total content of water was estimated. A comparison of the thermogravimet...
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Context 1
... silicas with various degrees of hydroxylation are widely used in science and technology [4]. Generally, surface silanol groups ( ≡ Si -OH) are formed via two thermodynamically favorable processes [4]. First, such groups are formed during synthesis, for example, the polycondensation polymerization of Si ( OH ) 4 (Fig. 1a), when a supersaturated solution of orthosilicic acid transforms into polysilicic acids, with the subsequent formation of SiO 2 sols and gels containing surface OH groups. When dried, the final product, xerogel, retains surface silanols, at least partially. Second, silanols can be produced by rehydroxylation of thermally dehydroxylated ...
Context 2
... transforms into polysilicic acids, with the subsequent formation of SiO 2 sols and gels containing surface OH groups. When dried, the final product, xerogel, retains surface silanols, at least partially. Second, silanols can be produced by rehydroxylation of thermally dehydroxylated silica during its treatment with water of an aqueous solution (Fig. ...
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Citations
... The isolated MS-NPs' vibrational bands at about 3436, 2921, 1627, 1552, 1095, 806, and 470 cm − 1 included adsorbed moisture and/or amorphous silica and/or silicic acid 37,49 . Si-OH showed symmetric and asymmetric vibrational absorption bands at 3436 cm − 1 and 806 cm − 1 , respectively 50,51 . The estimated adsorbed moisture of 4.38 wt% for MS-NPs, as determined by TG analysis, may be the reason for the broadening of the silanol peak between 3070 and 3750 cm − 1 owing to the H-bonded silanol groups. ...
This study investigates how biogenic mesoporous silica nanoparticles (MS-NPs) extracted from rice straw residues, a sustainable and economical bio-source, affect White Ordinary Portland Cement (WOPC) paste performance. A comprehensive investigation using varied fractions of 0.25, 0.50, 0.75, and 1.0% MS-NPs as an additive to WOPC was conducted to analyze the physicomechanical characteristics of WOPC-MS hardened composites, including compressive strength, fire resistance, and water demand. The beneficial impact of biogenic MS-NPS was verified by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and differential thermo-gravimetric analysis (TGA/DTG) methods, revealing several hydration products such as calcium silicate hydrates (CSHs), calcium ferrosilicate hydrates (CFSHs), and calcium aluminosilicate hydrates (CASHs). These products enhance the overall physical and mechanical properties and the thermal stability of hardened WOPC-MS. The composite comprising WOPC-0.75 MS provides numerous advantages from both an economic and environmental perspective.
... The drastic decrease in weight observed in the TGA graph of bioactive glass samples between 20-90 °C (Figure 2c) has been attributed to the removal of physically adsorbed water and residues from the bioactive glass production process [44]. Subsequently, the gradual reduction in weight observed between temperatures of 100-700 °C is attributed to the removal of internal water molecules due to the slow condensation of silanol groups [45,46]. ...
Several therapeutic approaches have been developed to promote bone regeneration, including guided bone regeneration (GBR), where barrier membranes play a crucial role in segregating soft tissue and facilitating bone growth. This study emphasizes the importance of considering specific tissue requirements in the design of materials for tissue regeneration, with a focus on the development of a double-layered membrane to mimic both soft and hard tissues within the context of GBR. The hard tissue-facing layer comprises collagen and zinc-doped bioactive glass to support bone tissue regeneration, while the soft tissue-facing layer combines collagen and chitosan. The electrospinning technique was employed to achieve the production of nanofibers resembling extracellular matrix fibers. The production of nano-sized (~116 nm) bioactive glasses was achieved by microemulsion assisted sol-gel method. The bioactive glass-containing layers developed hydroxyapatite on their surfaces starting from the first week of simulated body fluid (SBF) immersion, demonstrating that the membranes possessed favorable bioactivity properties. Moreover, all membranes exhibited distinct degradation behaviors in various mediums. However, weight loss exceeding 50% was observed in all tested samples after four weeks in both SBF and phosphate-buffered saline (PBS). The double-layered membranes were also subjected to mechanical testing, revealing a tensile strength of approximately 4 MPa. The double-layered membranes containing zinc-doped bioactive glass demonstrated cell viability of over 70% across all tested concentrations (0.2, 0.1, and 0.02 g/mL), confirming the excellent biocompatibility of the membranes. The fabricated polymer bioactive glass composite double-layered membranes are strong candidates with the potential to be utilized in tissue engineering applications.
... In summary, the charge density on the solid surface of MPS is related to the pore size, surface functional groups, pH of the solution, and ionic strength. With quantitative data www.nature.com/scientificreports/ on mesoporous silica's surface charge and hydroxyl density 26 , one can explain the mechanism of heavy metal adsorption on mesoporous materials at a certain pH level. In Fig. 2D, we can see the TGA curve that was obtained after mixing MPS with deionized water for 24 h. ...
This research delved into the influence of mesoporous silica’s surface charge density on the adsorption of Cu²⁺. The synthesis of mesoporous silica employed the hydrothermal method, with pore size controlled by varying the length of trimethylammonium bromide (CnTAB, n = 12, 14, 16) chains. Gas adsorption techniques and transmission electron microscopy characterized the mesoporous silica structure. Surface charge densities of the mesoporous silica were determined through potentiometric titration, while surface hydroxyl densities were assessed using the thermogravimetric method. Subsequently, batch adsorption experiments were conducted to study the adsorption of Cu²⁺ in mesoporous silica, and the process was comprehensively analyzed using Atomic absorption spectrometry (AAS), Fourier transform infrared (FTIR), and L3 edge X-ray absorption near edge structure (XANES). The research findings suggest a positive correlation between the pore size of mesoporous silica, its surface charge density, and the adsorption capacity for Cu²⁺. More specifically, as the pore size increases within the 3–4.1 nm range, the surface charge density and the adsorption capacity for Cu²⁺ also increase. Our findings provide valuable insights into the relationship between the physicochemical properties of mesoporous silica and the adsorption behavior of Cu²⁺, offering potential applications in areas such as environmental remediation and catalysis.
... The surface charge density of silica is usually controlled by protonation and deprotonation reactions, which belong to the category of solid surface ionization. These reactions are in uenced by counterions and are referred to as "charge screening," which implies that co-ions accumulate and counter ions are repelled 24 . Normally, the interfacial region is electrically neutral. ...
This research delved into the influence of mesoporous silica's surface charge density on the adsorption of Cu ²⁺ . The synthesis of mesoporous silica employed the hydrothermal method, with pore size controlled by varying the length of trimethylammonium bromide (C n TAB, n = 12,14,16) chains. Gas adsorption techniques and transmission electron microscopy characterized the mesoporous silica structure. Surface charge densities of the mesoporous silica were determined through potentiometric titration, while surface hydroxyl densities were assessed using the thermogravimetric method. Subsequently, batch adsorption experiments were conducted to study the adsorption of Cu ²⁺ in mesoporous silica, and the process was comprehensively analyzed using Atomic absorption spectrometry (AAS), Fourier transform infrared (FTIR), and L3 edge X-ray absorption near edge structure (XANES). The research findings suggest a positive correlation between the pore size of mesoporous silica, its surface charge density, and the adsorption capacity for Cu ²⁺ . More specifically, as the pore size increases within the 3-4.1 nm range, the surface charge density and the adsorption capacity for Cu ²⁺ also increase. Our findings provide valuable insights into the relationship between the physicochemical properties of mesoporous silica and the adsorption behavior of Cu ²⁺ , offering potential applications in areas such as environmental remediation and catalysis.
... A siloxane linkage subsequently forms through attack on the silanol silicon centre (the rate-determining step), rendering a silane network on the NP surface. 58,59 The nal FTIR spectra also indicates peaks spanning 1400-1200 cm −1 which signal Si-O-Si bridging bonds via condensation; specically, the Si-O-Si asymmetric stretch and the strained siloxane networks in amorphous silica. 60 The sharp peak around 1066 cm −1 represent the oxygen asymmetric stretch which is obvious in both NPs FTIR spectra. ...
Robust, hydrophobic woven cotton fabrics were obtained through the sol–gel dip coating of two different nanoparticle (NP) architectures; silica and silica-ZnO. Water repellency values as high as 148° and relatively low tilt angles for fibrous fabrics (12°) were observed, without the need for fluorinated components. In all cases, this enhanced functionality was achieved with the broad retention of water vapor permeability characteristics, i.e., less than 10% decrease. NP formation routes indicated direct bonding interactions in both the silica and silica-ZnO structures. The physico-chemical effects of NP-compatibilizer (i.e., polydimethoxysilane (PDMS) and n-octyltriethoxysilane (OTES) at different ratios) coatings on cotton fibres indicate that compatibilizer-NP interactions are predominantly physical. Whenever photoactive ZnO-containing additives were used, there was a minor decrease in hydrophobic character, but order of magnitude increases in UV-protective capability (i.e., UPF > 384); properties which were absent in non-ZnO-containing samples. Such water repellency and UPF capabilities were stable to both laundering and UV-exposure, resisting the commonly encountered UV-induced wettability transitions associated with photoactive ZnO. These results suggest that ZnO-containing silica NP coatings on cotton can confer both excellent and persistent surface hydrophobicity as well as UV-protective capability, with potential uses in wearables and functional textiles applications.
... Microwave-assisted synthesis has emerged as a powerful tool for material synthesis (Zengin et al., 2023) (Santos et al., 2021) due to its rapid processing, lower energy consumption, and enhanced control over material properties (Istrati et al., 2021) (Bucek et al., 2019). However, limited research has been conducted on tailoring the properties of silica gel, specifically the silanol group content, through microwave synthesis for improved moisture adsorption (Zhuravlev & Potapov, 2006). This study aims to fill this gap by investigating the influence of microwave-assisted synthesis parameters on the peak area of silanol groups in silica gel prepared from clear glass waste. ...
This research investigates the influence of microwave irradiation on the silanol content and moisture adsorption capacity of silica gel prepared from clear glass waste. Employing a green and efficient microwave-assisted synthesis method, we demonstrate rapid formation of silica gel with enhanced properties. Fourier-transform infrared (FTIR) analysis confirms the presence of silanol (Si-OH) groups on the synthesized gel, with a focus on the characteristic peak at 956.44 cm⁻¹ indicating their abundance. Notably, the peak area of this peak significantly increases with increasing irradiation time (5 to 15 minutes). This translates to a parallel increase in moisture adsorption capacity, rising from 56% to 82%. The enhanced silanol content suggests the potential of microwave-derived silica gel as a high-performance desiccant, as these groups directly contribute to moisture binding. Our findings highlight the promising potential of waste glass valorization via microwave synthesis for developing sustainable and effective moisture adsorbents.
... The surface of quartz glass is mainly composed of silanol groups (-SiOH), which can oxidize in the presence of an ozone-rich atmosphere and form siloxane groups (-Si-O-Si-). The oxidation reaction can be seen in These siloxane groups are naturally hydrophobic and contribute to quartz's low surface energy and therefore to its hydrophobicity (Zhuravlev, 2006;Owen, 2012;Ozçam, 2014;Schrader, 2018). (Zhuravlev, 2006;Owen, 2012;Ozçam, 2014;Schrader, 2018). ...
... The oxidation reaction can be seen in These siloxane groups are naturally hydrophobic and contribute to quartz's low surface energy and therefore to its hydrophobicity (Zhuravlev, 2006;Owen, 2012;Ozçam, 2014;Schrader, 2018). (Zhuravlev, 2006;Owen, 2012;Ozçam, 2014;Schrader, 2018). growth mechanism can be seen in Figure 3. Immediately after evacuating the tube with a mechanical pump, it is filled with highpurity nitrogen gas and allowed to flow at a constant rate for 5 min. ...
O primeiro material bidimensional descoberto foi o grafeno em 2004. A partir de então, estudos foram desenvolvidos com outros materiais e, um dos primeiros semicondutores a ser isolado foi o dissulfeto de molibdênio, o MoS2. Ao contrário do grafeno, o MoS2 tem gap de energia, e na forma de monocamada o gap passa de indireto para direto. Essa mudança resulta em uma fotoluminescência de alto brilho. Devido ao alto desempenho elétrico e óptico, o MoS2 (2D) tem grande potencial de aplicação nos dispositivos eletrônicos e campos fotoeletrônicos. Existem diversas técnicas para produzir este material, e uma delas é através do método de Deposição Química de Vapor (CVD) que consiste na formação de cristais no substrato, pela deposição atômica ou molecular, sendo o sólido oriundo de uma reação química onde os precursores estão na fase de vapor. O objetivo deste trabalho será sintetizar e caracterizar o MoS2 pelo método de CVD, a partir de um sistema de equipamento robusto construídos no laboratório. Para preparar os substratos foram submetidos a um tratamento de ultravioleta para permitir que os materiais depositados resistam ao desgaste por contato. Então construiu-se uma câmara para tratamento por radiação UV/ozônio, e, após a preparação, os substratos foram colocados em um forno com temperatura controlada e com atmosfera inerte. Este forno tubular também foi construído com o intuito da produção do MoS2. Após os ensaios foi possível obter a formação de MoS2 com a caracterização pelo MEV, EDS e DRX para análise e identificação dos materiais formados no substrato.
... The surface density of OH groups on the prepared a-SiO 2 layer was 4.4 nm −2 , which is consistent with previous experimental observations. 32,33 The c-SiO 2 surface was constructed following the procedure described in Ref. 16. The α-cristobalite system, comprised of 540 Si atoms and 1080 O atoms, was cleaved in the (111) plane. ...
As the semiconductor industry relentlessly reduces device sizes, efficient and precise cleaning processes have become increasingly critical to address challenges such as nanostructure stiction. Gaining insight into the molecular behavior of water and isopropyl alcohol (IPA) on silicon dioxide (SiO2) surfaces is essential for controlling semiconductor wet cleaning processes. This study investigated the interactions between these liquids and SiO2 surfaces. Using molecular dynamics (MD) simulations, we examined the adsorption behavior of water and IPA molecules on both amorphous and crystalline SiO2 (a-SiO2 and c-SiO2) surfaces. Our findings reveal a preferential adsorption of water molecules on a-SiO2 surfaces compared to c-SiO2. This preference can be ascribed to the irregularity of the a-SiO2 surface, which results in the presence of silanol groups that remain inaccessible to the liquid molecules. In contrast, the c-SiO2 surface exhibits a more uniform and accessible structure. This study not only imparts crucial insights into the molecular behavior of water and IPA on SiO2 surfaces but also provides valuable information for future enhancements and optimization of semiconductor wet surface preparation, cleaning, etching and drying.
... In both of the modified silica samples, the density of the grafted groups (see Table 2) is lower than the density of silanol in fully hydroxylated silica (~5-7 OH nm −2 [39][40][41]). This is the result of the reaction between each APTES or TMPS molecule through one, two or three hydrolyzed ethoxy moieties with the same number of silanol groups of the MSNs' surface [42]. ...
To investigate the impact of the surface functionalization of mesoporous silica nanoparticle (MSN) carriers in the physical state, molecular mobility and the release of Fenofibrate (FNB) MSNs with ordered cylindrical pores were prepared. The surface of the MSNs was modified with either (3-aminopropyl) triethoxysilane (APTES) or trimethoxy(phenyl)silane (TMPS), and the density of the grafted functional groups was quantified via ¹H-NMR. The incorporation in the ~3 nm pores of the MSNs promoted FNB amorphization, as evidenced via FTIR, DSC and dielectric analysis, showing no tendency to undergo recrystallization in opposition to the neat drug. Moreover, the onset of the glass transition was slightly shifted to lower temperatures when the drug was loaded in unmodified MSNs, and MSNs modified with APTES composite, while it increased in the case of TMPS-modified MSNs. Dielectric studies have confirmed these changes and allowed researchers to disclose the broad glass transition in multiple relaxations associated with different FNB populations. Moreover, DRS showed relaxation processes in dehydrated composites associated with surface-anchored FNB molecules whose mobility showed a correlation with the observed drug release profiles.
... Nitrogen adsorption-desorption isotherm, and DFT-calculated pore size distributions (insert) curves for SiO 2 depending on condition of coagulation(Kamenskyh et al. 2022) Fig. 2 XRD powder patterns for SiO 2 depending on condition of coagulation(Kamenskyh et al. 2022) According toZhuravlev and Potapov 2006, three peaks at 1082-1076, 798-781, and 434-428 cm −1 corresponded to the vibrations of the Si-O-Si bonds of the SiO 4 tetrahedron. These are all the essential bonding's found in the structure of mesoporous silica. ...
It is known that the physicochemical characteristics of amorphous SiO2 are influenced by the raw material, process temperature, pH of the reaction medium, the ratio of reagents, the addition of coagulant, and modes of washing and drying. Previously, a waste-free technology for the production of biogenic silicon dioxide was described. However, there was a question of the ability to control the grain size of the final product. Therefore, the aim of our work was to study the effect of the ratio of mass concentrations of silicon-containing solution and coagulant (5:100; 5:500; 5:1000) on the physicochemical properties of the final product. The obtained samples of silicon dioxide were studied by various physicochemical methods. XRD pattern of the obtained silica showed that the 2-theta region between 5° to 80° at long collection times indicates no crystalline peaks. The FT-IR spectrum of the whole silica samples shows typical functional groups corresponding to pure silicon dioxide at 1074, 982, 800 and 457 cm−1. There are two distinct mass loss steps in termograms (TGA). It was established that obtained samples had a specific surface area of 86.8, 318.3 and 310.2 m2/g and pore size of 3.3, 13.8 and 9.2 nm depending on coagulant concentration (100, 500 and 1000), respectively. The atomic force microscope method established that the 3D image clearly shows the pointed vertices of SiO2 tetrahedral for the whole gels and some powders depending on the ratio of silicon-containing solution and coagulant (5:100; 5:500; 5:1000).
