Tetraethoxyorthosilicate Research Articles

Synthesis mechanism and phase stability analysis of z‐Y2Si2O7 by sol‐gel process

AbstractSynthesis mechanism and phase stability analysis of square z‐Y2Si2O7 was studied in this research by using Y(NO3)3·6H2O and tetra ethoxy orthosilicate as precursors. The concentration of the precursor directly affects the degree of hydrolysis of tetra ethoxy orthosilicate and the uniformity of the gel by Fourier transform infrared spectral analysis. The thermogravimetric analysis shows that the crystallization temperature of the precursor decreases gradually with the decrease of precursor concentration. Because the low precursor concentration is beneficial to the formation of the homogeneous molecular level of yttrium silica network gel. Finally, the crystallized z‐Y2Si2O7 was detected by X‐ray diffraction and further verified by a transmission electron microscope after calcining at 800°C. The maximum stable temperature of z‐Y2Si2O7 was less than 1050°C. The microscopic morphology of z‐Y2Si2O7 is square nanoparticles. The grain size of z‐Y2Si2O7 increases with the decrease of precursor concentration.

Preparation of Poly styrene coated nano silica superhydrophobic coating and evaluation of stability for optical purposes

Super-hydrophobic nanocoatings are having enormous applications in various fields. In this paper, an attempt was made to prepare the adhesive transparent superhydrophobic coating for optical applications. Nano-silica based coatings were prepared by using tetraethoxyorthosilicate (TEOS) as a silica precursor. Hexamethyldisilazane (HMDS) and Polystyrene were used to make coatings superhydrophobic, transparent, and durable. To evaluate the coating properties, contact angle, and transparency were observed. A tape test was performed to determine coating stability. It was found that the HMDS is responsible for hydrophobicity and Poly-styrene is for adhesion. Poly-Styrene based coatings were more stable compared to only HMDS based coatings.

Comprehensive study of loading and release of sodium valproate drug molecule from functionalized SBA-15 with aminopropyl groups through Co-condensation modification method

Mesoporous Santa Barbara amorphous (SBA-15) was functionalized through co‐condensation using tetraethoxy orthosilicate and 3-aminopropyltriethoxysilane in the presence of the copolymer Pluronic P-123 (EO20PO70EO20) as a pore‐directing agent under an acidic condition. A comprehensive study of the sodium valproate (SV) loading and release was carried out on SBA-15 and functionalized SBA-15. The functionalized and drug loaded mesoporous materials were comprehensively characterized using X-ray diffraction, nitrogen adsorption isotherms, FTIR, TGA, SEM, and TEM techniques. The Box-Behnken design was applied to optimize the variables of drug loading time, ultrasound irradiation time, and carrier dose. Results indicated that the COO− group of SV was associated with the amine group of functionalized SBA-15. SV release was performed in HCl 0.01 M, acetate buffer solution pH = 4.5, and phosphate buffer solution pH = 6.8. The release date indicated that the loading of the aminopropyl group in SBA-15 influenced the release properties of SV. Eventually, the drug release kinetic models were investigated for both carriers.

Fabrication and Evaluation of Trimethylmethoxysilane (TMMOS)-Derived Membranes for Gas Separation.

Gas separation membranes were fabricated with varying trimethylmethoxysilane (TMMOS)/tetraethoxy orthosilicate (TEOS) ratios by a chemical vapor deposition (CVD) method at 650 °C and atmospheric pressure. The membrane had a high H2 permeance of 8.3 × 10−7 mol m−2 s−1 Pa−1 with H2/CH4 selectivity of 140 and H2/C2H6 selectivity of 180 at 300 °C. Fourier transform infrared (FTIR) measurements indicated existence of methyl groups at high preparation temperature (650 °C), which led to a higher hydrothermal stability of the TMMOS-derived membranes than of a pure TEOS-derived membrane. Temperature-dependence measurements of the permeance of various gas species were used to establish a permeation mechanism. It was found that smaller species (He, H2, and Ne) followed a solid-state diffusion model while larger species (N2, CO2, and CH4) followed a gas translational diffusion model.

Hexadecyltrimethylammonium Bromide Surfactant-Supported Silica Material for the Effective Adsorption of Metanil Yellow Dye.

The adsorption behavior of an organic dye, metanil yellow (My), from water using micro–nano silica particles (MNSPs) was investigated. MCM-41-like (Mobil Composition of Matter No. 41) MNSPs were synthesized using tetraethoxy orthosilicate as a silica source and hexadecyltrimethylammonium bromide (CTAB) as a surfactant under basic conditions. Comparative studies were performed to assess the adsorption behaviors of the organic dye using the as-synthesized MCM-41 before the removal of CTAB and MCM-41, either after one, two, and three times of chemical etching or after calcination. My was adsorbed more effectively from water on the as-synthesized MCM-41 without the removal of the surfactant than on MCM-41 after the removal of the surfactant by chemical etching or calcination. In addition, MCM-41 after removing the surfactant by one-time chemical etching in the presence of hydrochloric acid also showed better adsorption of My from water than MCM-41 after removing the surfactant by further two and three times of chemical etching or calcination. For comparison, other kinds of dye molecules with different chemical structures such as methylene blue (Mb) and rhodamine B (Rb) were also used to check the possibility of adsorption of various dyes by the CTAB-supported MNSPs. To better understand the reason behind the adsorption phenomena, detailed studies on the kinetics and thermodynamics of adsorption of the MNSPs were performed. Excellent adsorption of My was observed at concentrations up to 100 mg L–1 at 25 °C, whereas the adsorption was lower at higher concentrations of the My dye. Furthermore, enhanced My dye adsorption was observed at higher concentrations by increasing the adsorption temperature. It can be concluded that the MNSPs exhibited efficient adsorption of My, when the MNSPs are used without the removal of the surfactant and any further modifications, suggesting that the surfactant played key roles in the effective adsorption of the anionic dye. The as-synthesized MCM-41 was, however, not a good adsorbent for cationic dyes such as Mb and Rb.

Investigation of toxic effects of amorphous SiO2 nanoparticles on motility and oxidative stress markers in rainbow trout sperm cells.

In this study, we investigated the effects of SiO2 nanoparticles (SiO2-NPs) (1, 10, 25, 50, and 100mg/L) for 24h in vitro on the motility parameters and oxidative stress markers such as total glutathione (TGSH), catalase (CAT), and malondialdehyde (MDA) of rainbow trout, Oncorhynchus mykiss sperm cells. Therefore, SiO2-NPs were synthesized with sol-gel reaction from tetraethoxy orthosilicate (TEOS). The prepared nanoparticle structures were characterized for chemical structure, morphology and thermal behavior employing Fourier transform infrared spectroscopy, X-ray spectroscopy, scanning electron micrograph, and thermal analysis (DTA/TGA/DSC) techniques. After exposure, there was statistically significant (p< 0.05) decreases in velocities of sperm cells. CAT activity significantly (p <0.05) decreased by 9.6% in sperm cell treated with 100mg/L. In addition, MDA level significantly increased by 70.4% and 77.5% in sperm cell treated with 50 and 100mg/L SiO2-NPs, respectively (p <0.05). These results showed that SiO2-NPs may have toxic effect on rainbow trout sperm cells in 50mg/L and more.

Development of amino-functionalized silica nanoparticles for efficient and rapid removal of COD from pre-treated palm oil effluent

In this study, low cost synthesis of three-dimensional mesoporous amino-functionalized silica nanoparticles (AFS-NPs) were synthesized by sol–gel method with the addition of two different silica modifiers, 3-aminopropyltrimethoxysilane (APTMS) and 3-aminopropyltriethoxysilane (APTES) to two different silica sources, tetramethoxyorthosilicate (TMOS) and tetraethoxyorthosilicate (TEOS) separately. The presence of amino group on synthesized nanoparticles from the four different combinations was confirmed by Fourier transform infrared (FTIR) spectroscopy. The synthesized AFS-NPs were of narrow particle size within the range of 500–600nm and having high specific surface area (148m2g−1). The AFS-NPs were then utilized to investigate the adsorptive removal of COD from palm oil mil effluent (POME). The maximum removal efficiency (>90%) of AFS-NPs was found at pH 7, adsorbent dose 0.25g and temperature 30°C. At equilibrium the maximum adsorption capacity was found to be 271.11mgg−1. The Langmuir adsorption isotherm gave the best fit to the experimental data signifying the presence of adsorption monolayer on the surface of the adsorbent. The results have positively qualified grafted silica nanoparticles as one of the adsorptive media for removal of COD from POME.

Electrospun biomimetic catalytic polymer template for the sol-gel formation of multidimensional ceramic structures

A biomimetic block copolymer, poly(hydroxylated isoprene-b-2-vinyl pyridine), mimicking the catalytic and templating properties of the protein Silicatein α, was used to template the condensation of 2-dimensional and 3-dimensional silica and titania materials. Spin-coating and electrospinning techniques were used to process the block copolymer into fibers and films that were treated with tetraethoxy orthosilicate (TEOS) or titanium (IV) iso-propoxide (TiP) to form organic-inorganic hybrid fibers and films. All hybrid materials were synthesized at room temperature and neutral pH, and even after calcination and removal of the polymer, the ceramics retain the structure templated by the block copolymer.

Synthesis of CaCO3–SiO2 composite using CO2 for fire retardant

Calcium carbonate (CaCO3) and calcium silicate (Ca2SiO4) are widely used fillers for fire retardant to polymer and other materials. In recent years, reducing greenhouse gas has become a key issue for environmental concern. Capturing CO2 gas as a solid form in room temperature and ambient condition is attractive method to reduce the greenhouse gas and uses as a fire retardant, such as CaCO3–SiO2 composite. Calcium carbonate–silica composite (CaCO3–SiO2) has been synthesized by bubbling CO2 gas into an aqueous Ca(OH)2 medium with NH4OH catalyst. Completely dissolved and transparent Ca(OH)2 solution was prepared to react Ca(OH)2, tetraethoxy orthosilicate (TEOS), and CO2. The characteristic FTIR absorption peaks of CaCO3 and SiO2 appeared at 1450, 1100, 875 and 712 cm−1. Field emission scanning electron microscope (FESEM) images show mixed particle sizes with small particles (approximately several hundred nanometers) and large particles (approximately several micrometers). Using completely dissolved Ca(OH)2 and TEOS with NH4OH catalyst is one of the effective method not only capturing CO2 greenhouse gas and use as fire retardant.

Characterization and synthesis of polyester and viscose nonwovens fabrics embedded with nanoporous amorphous silica

Supreme thermal insulating properties of fibre composite can fortify its niche as a middle layer for numerous cold wear articles. Aiming to achieve lowest thermal conductivity, two separate nonwoven composites were successfully developed by using polyester and viscose fibres. Both were reinforced separately with in-house synthesized nanoporous amorphous silica via sol-gel processing using Tetraethoxy orthosilicate as a precursor with ambient pressure drying. Both nonwovens with two levels of GSM were subjected to silica sol for synthesis of nonwoven/SiO2 composite followed by solvent exchange, silylation and ambient pressure drying. The resulted structures were analyzed and evaluated for their thermal conductivity, pore size and characterized by The Fourier Transform Infrared spectroscopy and Scanning electron microscopy. Properties of composites were examined and compared to each level and attributes. Significant differences between the parameters were calculated using statistica v7.0. One of composite showed lowest thermal conductivity value 0.028 W/m.K

Comparison Study of Paraquat Herbicide Adsorption by Xerogels: Application of Experimental Design

This study dealt with the Paraquat dichloride herbicide (PQT) adsorption on xerogels. The xerogels were synthesized with tetra methoxy orthosilicate (TMOS) and tetra ethoxy orthosilicate (TEOS) as a precursor. Whereas xerogels have free silanol groups on their surface and PQT has a positive charge as an ion, xerogels have shown a high affinity for the PQT adsorption in aqueous solution. Scanning Electron Microscopy, Fourier Transform‐IR, and BET analysis were characterized xerogels. The effect of four process factors such as PQT dosage, pH, a dose of adsorbent, and time was evaluated by the Box‐Behnken design. Between four parameters, pH was more effective. The second order equation (quadratic model) was also used for the analysis of the experimental data. Additionally, the optimum points for parameters were determined by desirability function in the Experimental Design. Removal Percentages of PQT at the optimum process parameters were found to be 98.05 and 92.83%, for TMOS and TEOS xerogels, respectively. In addition, the isotherm study showed that the Freundlich isotherm indicated better harmonic between experimental and theoretical results. Finally, in the kinetic study, Pseudo‐second order model had a better correlation than Pseudo‐first order model. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S128–S138, 2019

A Comparative Study of Fluorescein Isothiocyanate-Encapsulated Silica Nanoparticles Prepared in Seven Different Routes for Developing Fingerprints on Non-Porous Surfaces

Preparation of fluorescein isothiocyanate (FITC)-encapsulated silica nanoparticles (F-SiNPs) via seven different approaches to be used as developing agents for fingerprints detection is presented in this report. In this study, the suitability of each synthesis route toward incorporation of the selected fluorophore into silica matrix and its efficiency in fingerprints detection were systematically studied. The composition of the particles was designed to examine the hydrophobic and dipole-dipole interactions between the silicate backbone and both of the fluorescent reporter molecules and the fingerprint residues. F-SiNPs were prepared with two conventional sol-gel approaches; the Stöber method and the water in oil reverse microemulsion (WORM) method. The alkoxysilane precursor, tetraethoxyorthosilicate (TEOS) and its binary mixtures with phenyltriethoxysilane (PTEOS) or 3-aminopropyl triethoxysilane (APTES) have been used in preparing the F-SiNPs to study the effect of nanoparticles composition on fingerprints development. In addition, FITC was conjugated with APTES so it can be covalently bonded to the silica matrix and to be compared with non-covalently FITC-doped SiNPs. Moreover, the enhancement effect of introducing polyvinylpyrrolidone (PVP) onto the surface of the less hydrophobic F-SiNP on fingerprints detection on different non-porous surfaces was also investigated. The mean diameters of the F-SiNPs were between 4.1 ± 0.6 and 110.4 ± 31.1nm as obtained from the TEM size measurement for the nanoparticles prepared by the WORM and Stöber methods, respectively. The obtained results clearly highlight the advantages of using a mixture of TEOS and PTEOS alkoxysilane precursors in preparing F-SiNPs with remarkable encapsulation efficiency and clear detection of fingerprints due to efficient embedding of the fluorophore inside the silica network even without conjugation. It was also observed that both the Stöber and WORM methods can be used in preparing the F-SiNPs developing agents and that PVP coated particles did not show any significant enhancement in fingerprints visualization.

Graphite Supported Silica Immobilized Phosphotungstic Acid Based Ion-Conducting Inorganic Membrane

An asymmetric, inorganic ion-conducting membrane was synthesized by depositing a top layer containing silica-immobilized phosphotungstic acid (Si-PWA) over a graphite sheet. Surface morphology, thermal stability, and structure of the top layer of the membrane were studied using scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR), respectively. The transport number and specific conductivity of the membrane were measured using membrane potential and impedance measurements, respectively. The composition of the top layer was varied by changing the molar ratio of PWA and tetraethoxy orthosilicate (TEOS) in the casting sol. The transport number and specific conductivity of the membrane increased on increasing PWA fraction in the casting solution. The highest transport number for sodium ion was 0.98 for PWA: TEOS molar ratio of 1.5. Specific conductivity of the membrane, with 0.5 PWA: TEOS, was 0.0082 S cm−1 which was lower compared to the membrane with 1.5 PWA: TEOS of specific conductivity 0.017 S cm−1. The specific conductivity of the membrane increased with increase in the temperature for both 0.5 and 1.5 molar ratio of PWA: TEOS with the calculated activation energy 18.9 and 8.8 kJ/mol, respectively.

Synthesis and characterization of hydrogen selective silica membranes prepared by chemical vapor deposition of vinyltriethoxysilane

Hydrogen-selective silica membranes were prepared on a macroporous alumina support by chemical vapor deposition (CVD) of vinyltriethoxysilane (VTES) at 873 K at atmospheric pressure. The membrane had a high H2 permeance of 5.4 × 10−7molm−2s−1Pa−1 with H2 selectivity over CO2, N2, CO and CH4 of 95, 170, 170 and 480, respectively. In situ Fourier transform infrared (FTIR) measurements after CVD on an alumina disk at the same conditions as for the membrane preparation showed that the vinyl groups remained in the silica structure. The VTES-derived membrane had higher hydrothermal stability than a pure tetraethoxyorthosilicate (TEOS)-derived silica membrane, during exposure to 16mol% water vapor at 872 K for 72h. The temperature dependence of the permeance of various molecules (He, Ne, H2, CO2, N2, CO, CH4) before and after hydrothermal treatment gave information about the mechanism of permeance and the structure of the membrane. The membrane was composed of a contiguous silica network through which small species permeated by a solid-state mechanism and a small number of pores through which the large molecules diffused. The silica-based structure became more compact after hydrothermal treatment with decreasing permeance of small molecules (He, Ne, H2), while small pores were enlarged increasing permeance of large molecules (CO2, N2, CO, CH4). Calculation results for the small species based on a mechanism involving jumps of the permeating species between solubility sites showed lower activation energy and larger jump distances than those of a TEOS-derived silica membrane. The retention of the vinyl groups in the structure mostly associated with the defect pores resulted in interactions with CH4 and CO2, so that these species permeated by a surface diffusion mechanism.

Preparation of fluorescently labeled silica nanoparticles using an amino acid-catalyzed seeds regrowth technique: Application to latent fingerprints detection and hemocompatibility studies

The efficiency of an amino acid catalyzed seed regrowth technique (ACSRT) in synthesizing twelve fluorescently labeled core-shell silica nanoparticles (FLSNPs) with tunable sizes, tailored hydrophobicity, low polydispersity as well as high labeling efficiency and minimized dye leakage using different combinations of organosilicate monomers and fluorophores have been systematically investigated in this report. The utilization of some of these FLSNPs in some applications that are facilitated by hydrophobicity such as developing and visualizing latent fingerprints (LFPs) on different surfaces was also investigated. The non-specific binding affinity of the developed nanoparticles to human serum albumin (HSA) and immunoglobulin G (IgG) has also been studied. Fluorescein, fluorescein isothiocyanate and its more hydrophilic butenamine derivative (WA6) have been used in this study. Also, the alkoxysilane precursor, tetraethoxyorthosilicate (TEOS) and its binary mixture with phenyltriethoxysilane (PTEOS) or 3-aminopropyl triethoxysilane (APTES) have been used in preparing the FLSNPs with tailored compositions for the core and shell of the nanoparticles. The mean diameters of the PTEOS-coated FLSNPs were between 33.4±5.9 and 42.2±10.8 nm as shown by the SEM measurements. The obtained results highlight the advantages of having a hydrophobic surface along with proper selection of the monomers forming the core to match the properties of the fluorescent reporters for clear detection of LFPs even using dyes of low hydrophobicity such as fluorescein and WA6. Furthermore, some of the developed FLSNPs were compared with bare silica nanoparticles in terms of nonspecific protein adsorption and hemolysis. The obtained results proved that the selected FLSNPs had a superior hemocompatibility in comparison with bare silica nanoparticles. These FLSNPs could also be used in some bio-related and diagnostic applications such as immunoassays and cell imaging purposes.

Decarboxylative Coupling Strategy To Afford N-Heterocycles Driven by Silica-Nanosphere-Embedded Copper Oxide (Cu@SiO2-NS)

An environmentally benign and surfactant-free method was developed for the preparation of porous silica nanospheres (SiO2 NS) from the hydrolysis of tetraethoxyorthosilicate (TEOS), using corn starch as a sacrificial template. The stabilization of malachite on SiO2 NS, followed by calcination at 600 °C, afforded silica-nanosphere-embedded copper oxide (Cu@SiO2-NS). The obtained Cu@SiO2-NS was found to be a versatile nanocatalyst for the decarboxylative coupling strategies to afford aromatic or aliphatic N-heterocycles such as aminoindolozines, pyrrolo[1,2-a]quinolones, and substituted pyrrolidine. The Cu@SiO2-NS was successfully recycled for six times without significant loss in its catalytic efficiency. The present method shows several advantages, such as being an environmentally benign approach for the catalyst preparation, being easy to handle, and having a wide substrate scope for decarboxylative couplings with excellent yields in short reaction time, and showed excellent green chemistry metrics, such as E-factor, process mass intensity (PMI), reaction mass efficiency (RME), carbon efficiency (CE), and comparatively high turnover number/turnover frequency (TON/TOF) values.

Controlled drug release in silicone adhesive utilizing particulate additives

Polydimethylsiloxane (PDMS) based adhesives were prepared by cross-linking tetraethoxyorthosilicate (TEOS) while controlling stoichiometry with PDMS, acid catalyst, and water. Particulate additives, alginate and bentonite, were added during the cross-linking process. Cationic drug lidocaine was incorporated into the adhesive with or without additive, and the time-dependent drug release profile was evaluated in phosphate buffered saline and ethanol, respectively. According to kinetic fitting to power function and parabolic diffusion, both solvent and additive type influenced drug release. In particular, particulate additives were found to suppress or facilitate drug release in water or ethanol, respectively.

High Temperature Processable Flexible Polymer Films

Recent developments in the field of flexible electronics motivated the researchers to start working in verdict of new flexible substrate for replacing the existing rigid glass and flexible plastics. Flexible substrates offer significant rewards in terms of being able to fabricate flexible electronic devices that are robust, thinner, conformable, lighter and can be rolled away when needed. In this work, a new flexible and transparent substrate with the help of organic materials such as Polydimethylsiloxane (PDMS) and tetra ethoxy orthosilicate (TEOS) is synthesized. Transmittance of about 90–95% is acquired in the visible region (400–700[Formula: see text]nm) and the synthesized substrate shows better thermal characteristics and withstands temperature up to 200[Formula: see text]C without any significant degradation. Characteristics such as transmittance ([Formula: see text]), absorption ([Formula: see text]), reflectance ([Formula: see text]), refractive index ([Formula: see text]) and extinction coefficient ([Formula: see text]) are also reported.

Controlling the bio-inspired synthesis of silica

The influence of different parameters on the silicification procedure using lysozyme is reported. When polyethoxysiloxane (PEOS), an internally crosslinked silica reservoir, is used, regular structures with a narrow size distribution could be obtained only via introducing the silica precursor in two steps including initial dropping and subsequent addition of residual oil phase in one portion. We found that mixing sequence of mineralizing agents in the presence of a positively charged surfactant plays a key role in terms of silica precipitation when tetraethoxyorthosilicate (TEOS) is the oil phase. In contrast, well-mineralized crumpled features with high specific surface area could be synthesized in the presence of PEOS as a silica precursor polymer, regardless of mixing sequence. Moreover, introducing sodium dodecyl sulfate (SDS) as a negatively charged surfactant resulted in regular silica sphere formation only in combination with hexylene glycol (MPD) as a specific co-solvent. Finally, it is demonstrated that by inclusion of different nanoparticles even more sophisticated hybrid materials can be generated.

PH responsive cylindrical MSN for oral delivery of insulin-design, fabrication and evaluation

Objective: The objective of the present study was to develop novel PMV [poly (methacrylic acid-co-vinyl triethoxylsilane)]-coated mesoporous silica nanoparticles (MSN) with improved hypoglycemic effect for oral insulin (INS) delivery.Methods: MSN was synthesized under acidic condition using Pluronic® P 123 and Tetra ethoxy orthosilane. Surfactant was removed by calcination. Calcined MSN was coated with pH sensitive polymer PMV. Cytotoxicity of this coated MSN was evaluated by MTT assay using CHO-K1 cell line. Different MSN samples were characterized with BET surface area analyzer, FESEM, TEM, FT-IR, XRD, TG-DTA. In vivo study was performed using male rats. Pharmacokinetic study was conducted using HPLC.Results and discussion: Highest surface area (304.3921 m2/g) was observed in case of calcined sample. Adsorption pore width of final coated sample was highest (64.7844 nm) compared with others. No noticeable cytotoxicity was observed for this coated support. The entrapment efficiency of insulin was found to be 39.39%. In vitro studies were done at different pH using Franz-diffusion cell. Results showed significant release at pH 7.4. Cumulative drug release over a period of 6 h was more than 48% at this systemic pH. Effect of this MSN-PMV-INS on blood glucose level was retained for 16 h. This novel formulation has shown 73.10% relative bioavailability of insulin.Conclusion: A novel-coated mesoporous silica support was successfully developed for delivery of insulin through oral route.