Tetramethoxysilane Research Articles

Determination of Al(III), Pb(II), and Cu(II) in Gunshot Residue Using Amino-Functionalized Silica Adsorbents in Dispersive Solid Phase Microextraction (DSPME) with Capillary Electrophoresis (CE)

Here is reported the design, synthesis, and application of an amino silica adsorbent for the extraction and determination of Al(III), Pb(II), and Cu(II) in gunshot residue (GSR) from the dorsal and palmar zones by capillary electrophoresis. The extraction procedure was used to determine the adsorbent composition by varying the molar ratio of the cross-linking agent tetramethyl orthosilicate (TMOS) and the functional monomer 3-aminopropyl trimethoxysilane (APTMS). (5.0:0.0 to 0.0:5.0). The optimal composition (3.0:2.0) was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and adsorption isotherm analysis. A univariate method was used to optimize critical factors in dispersive solid phase microextraction (DSPME), including the adsorbent mass, contact time, sample volume, and elution solution. Using the optimal conditions (adsorbent, 10 mg; contact time, 10 min; sample volume, 5 mL; eluent solution, methanol/10−1 mol L−1 HNO3), the method provides limits of detection of 0.06 mg L−1 for Pb(II), 0.08 mg L−1 for Cu(II), and 0.11 mg L−1 for Al(III). The precision and accuracy were evaluated in terms of inter- and intra-day repeatability (n = 3) with a relative standard deviation below 10%. The developed method was applied for gunshot residue analysis, providing concentrations from 12.6 to 702 mg L−1 for Al(III), 11.8 to 280 mg L−1 for Pb(II), and 29.8 to 395.6 mg L−1 for Cu(II).

An Overview of Current and Prognostic Trends on Synthesis, Characterization, and Applications of Biobased Silica

Silica has shown numerous applications in different fields such as environmental, biomedical, agriculture, and even in chemical processing. However, due to high energy-intensive and cost-effective issues, researchers show interest to replace the conventional methods with biobased environmentally-friendly techniques for biosilica production from renewable biomass sources. Generally, silica is found to be available in amorphous and crystalline structures. For commercial purposes, silica is produced from alkyl orthosilicates ore that consists of polyethlydiorthosilicate, tetraethyl ortothosilicate, and tetramethyl orthosilicate. Another form of silica, silica gel, is produced from the selected resources of biomass, such as palm tree, wheat straw, maize leaves, teff straw, sugarcane bagasse, rice husk, rice straw, sugarcane leaf, oat husk, bamboo leaf, and corn cob. The production of biobased silica gel from agricultural residues is found to be a sustainable which receives a significant attention that can be replaced with inorganic-based silica gel for environmental concerns. Based on this context, there is a huge look for developing a process to produce biobased silica and silica gel from biomass resources with low energy utilization as promising alternatives to conventional methods. Keeping in view, current trends and methods for synthesis, the characterization of biobased silica and silica gel, as well as its wide prognostic applications were focused on a comprehensive review.

Synthesis of SiO2-coated perovskite quantum dots for micro-LED display applications

Cadmium quantum dots (QDs) have good luminous properties, but cadmium is toxic. So, cadmium-free perovskite QDs were synthesized by chemical solution methods, realizing the new structure of the green CsPbBr3/Cs4PbBr6 perovskite QDs. The SiO2 layer passivated the perovskite QDs by the sol-gel method and hydrolysis of tetramethoxysilane (TMOS) and then dispersed in a polar solvent to facilitate mixing with negative photoresist (SU8-3010) to ensure their luminous properties are not affected by moisture and oxygen. Afterward, perovskite QDs were exposed and developed on the glass substrate by a photolithography process. The pixels were spaced apart through the black matrix to reduce the crosstalk between each other. Applying the pixelated perovskite QDs to the blue light micro-light-emitting diodes (LED) display as the color conversion layer showed that excessive blue light could penetrate through the green pixels, decreasing color purity. Therefore, we used a 23-layer distributed Bragg reflector (DBR) to reflect excess blue light on pixels back to perovskite QDs. DBR did not filter the green light, and the actual luminous intensity of green light increased by 118%, and the transmittance of blue light was only 0.5%. Finally, the alignment attaching of the graph pixelated perovskite QDs on a glass substrate to the blue light display realized monochrome/area color and full-color micro-LED display.

NondemandingIn SituEncapsulation Route to Ultrastable Perovskite Nanocrystals for White Light-Emitting Diodes

Although tremendous advancement regarding the highly stable metal halide perovskite nanocrystals (PNCs) has been achieved, previous studies were primarily focused on green light-emitting PNCs (i.e., bromine-based PNCs). The stability of chlorine-based PNCs with a violet or blue emission property was still lagging behind that of their bromine-based counterparts. Herein, a nondemanding and versatile strategy for in situ encapsulating all-inorganic chlorine-based PNCs with multifold exceptionally high stabilities was presented. Well-ordered mesoporous silica enabled the confined growth of PNCs in its pores followed by the porosity sealing by tetramethyl orthosilicate hydrolysis, thereby rendering full encapsulation of chlorine-based PNCs in dense silica that originated from high-temperature calcination. This judiciously designed structure imparted enclosed violet/blue emitting PNCs impart with outstanding long-term stability (>1.5 year) with high photoluminescence quantum yield (i.e., 30.4%) in pure water as the result of complete isolation of PNCs from detrimental stimuli, eventually leading to the application in the white light-emitting diode device.

Direct Conversion of Low-Concentration CO2 into N-Aryl and N-Alkyl Carbamic Acid Esters Using Tetramethyl Orthosilicate with Amidines as a CO2 Capture Agent and a Catalyst.

Herein, we report the direct conversion of low-concentration CO2 (15 vol %), equivalent to the CO2 concentration in the exhaust gas from a thermal power station, into carbamic acid esters (CAEs), which are precursors for pharmaceuticals, agrochemicals, and isocyanates. The reaction was performed using Si(OMe)4 as a nonmetallic regenerable reagent and 1,8-diazabicyclo[5.4.0]undec-7-ene as a CO2 capture agent and catalyst. This reaction system does not require the addition of metal complex catalysts or metal salt additives and is therefore simpler than our previously reported reaction system involving Ti(OR)4 and a Zn(II) catalyst. A variety of N-aryl, N-alkyl, and bis CAEs (precursors of polyurethane raw materials) were obtained in moderate to high yields (45-77% for 6 examples, 84-89% for 7 examples). In addition, bis CAEs were successfully synthesized from simulated exhaust gas containing impurities such as SO2, NO2, and CO or on a gram scale. We believe that this method can eliminate the use of toxic phosgene as the raw material for isocyanate production and mitigate CO2 emissions.

Catalytic Biomaterials for Atrazine Degradation

In this paper, triazine hydrolase from Arthrobacter aurescens TC1 (TrzN) was successfully immobilized in alginate beads (TrzN:alginate), alginate beads coated in chitosan (TrzN:chitosan), and tetramethylorthosilicate (TMOS) gels using the sol–gel method (TrzN:sol–gel) for the first time. TrzN:alginate and TrzN:chitosan hydrolyzed 50 µM of atrazine in 6 h with negligible protein loss with an ~80% conversion rate. However, the TrzN:sol–gel biomaterial converted >95% of a 50 µM atrazine solution in an hour with negligible protein loss. The treatment of each of these biomaterials with trypsin confirmed that the catalytic activity was due to the encapsulated enzyme and not surface-bound TrzN. All three of the biomaterials showed potential for long-term storage and reuse, with the only limitation arising from the loss of protein in the storage buffer for the TrzN:alginate and TrzN:chitosan biomaterials, not the denaturation of the encapsulated TrzN. TrzN:sol–gel stood out, with ~100% activity being retained after 10 consecutive reactions. Additionally, the materials stayed active in methanol concentrations <10%, suggesting the ability to increase the solubility of atrazine with organic solvents. The structural integrity of the TrzN:alginate and TrzN:chitosan materials became limiting in extreme pH conditions, while TrzN:sol–gel outperformed WT TrzN. Overall, the TrzN:sol–gel biomaterial proved to be the best atrazine dichlorination biocatalyst. As sol–gels can be cast into any desired shape, including pellets, which can be used in columns, the TrzN:sol–gel biomaterial provides a new avenue for the design of bioremediation methodologies for the removal of atrazine from the environment.

One-pot removal of pharmaceuticals and toxic heavy metals from water using xerogel-immobilized quartz/banana peels-activated carbon

ABSTRACT Here, we report the efficient one-pot removal of heavy metal ions and pharmaceuticals using xerogel, activated carbon and gravel. The simplest xerogel from tetramethyl orthosilicate showed ∼ twice the adsorption capacity of activated carbon derived from banana peels at 600 °C and far greater (x 35) than quartz pellets of diameter ∼300 μm. Functional groups present in both xerogel and activated carbon greatly enhanced the adsorption process. The combination of the three adsorbents resulted in the removal of > 95% of heavy metal ions and pharmaceuticals from water. The data fitted well in linear equations of Langmuir and Freundlich adsorption isotherms, and pseudo-first-order and pseudo-second-order kinetics, an indication for physisorption, chemisorption, adsorption and desorption processes during pollutant capture by the adsorbents.

Temperature responsive poly(N-isopropylacrylamide-co-styrene) nanofilms for non-enzymatic cell sheet harvesting

In this study, temperature-responsive cell culture substrates with non-enzymatic cell sheet detachment attributes in response to temperature reduction were prepared. Poly(N-isopropylacrylamide) (PNIPAAm) with a physiologically proximal lower critical solution temperature (LCST) induces a temperature responsivity to the substrate, and polystyrene was used to regulate the hydrophobicity of the substrate. Different compositions of poly(NIPAAm-co-styrene) were synthesized by free radical polymerization. The resulting copolymers were characterized using Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopy. The copolymer composition was calculated from 1HNMR results. The molecular weight and molecular weight distribution were measured by gel permeation chromatography (GPC). The nanofilms of the prepared copolymers were physically coated by spin-coating technique on tetramethyl orthosilicate (TMOS) pre-coated glass slides. Attenuated total reflection-FTIR (ATR-FTIR) and field emission scanning electron microscopy (FESEM) analyses showed that the spin coating procedure was performed successfully, and the change in the water contact angle (WCA) in response to temperature alteration indicated the temperature-responsive behavior of the polymer layers. L929 mouse fibroblast cell line was cultured on nanofilm-coated glass slides until a confluent cell sheet covered the entire surface. An almost integrated cell sheet was harvested by temperature reduction from 37 °C to 20 °C. The results revealed that copolymer composition is vital in harvesting contiguous cell sheets. This fabrication method, compared to others such as plasma polymerization and surface-initiated atom transfer radical polymerization (SI-ATRP), is very cost-effective and applicable for large-scale cell culture investigations.

Solvent Volatilization-Induced Cross-Linking of PDMS Coatings for Large-Scale Deicing Applications

Icing of surfaces has become a serious issue, and effective methods for preventing ice accretion have received much attention in recent years. Here, a solvent volatilization-induced cross-linking hydroxy-terminated dimethylsiloxane (Si–OH) coating with tetramethoxysilane (TMOS) as a cross-linker is proposed for large-scale deicing applications. Interfacial adhesion tests and shear force analysis were conducted to confirm the large-scale deicing properties of the polydimethylsiloxane (PDMS) coating. Through characterization of morphology, it was found that there were negative correlations between roughness and constant shear force and shear strength. The mean constant shear force per unit width could be lower than 14 N/cm when the roughness was in the highest range fabricated in this research. In addition to the morphology of the surface, the mass ratio of the cross-linker to the premonomer affected the state of the surface and the deicing properties. When the mass ratio was lowered, uncross-linked molecular chains of the premonomer existed on the surface, which resulted in an increase in interfacial toughness and a reduction in shear strength. Finally, durability tests showed that the coating had excellent durability and could endure at least 50 cycles without an apparent increase in the constant shear force.

Plastic Optical Fiber pH Sensor Based on Sol-Gel Film

A plastic optical fiber (POF) pH sensor is developed based on a sol-gel film. A sol-gel film was prepared by mixing tetramethyl orthosilicate (TMOS), trimethoxymethylsilane (MTMS), ethanol, distilled water and Neutral Red (NR) powder. Then, plastic optical fiber is coated by manually depositing the sol-gel film onto the tip of the POF. The sensing probe is dissolved into analytes with different pH levels, such as Coca-Cola (pH 3), tomato sauce (pH 4), black coffee (pH 5), tea (pH 6), distilled water (pH 7), soap (pH 8), baking soda (pH 9) and Clorox bleach(pH 10). The Refractive index will increase when the analytes are more acidic or more alkaline because they are concentrated with hydrogen and hydroxide ions at pH 3 and pH 10. The output power is varied based on the chemical reaction with the pH sol-gel film in the fiber-optic sensing probe. From the experimental results, it is concluded that the sensitivity of coated POF sensor, which is 0.0566 a.u/RIU, is higher than the sensitivity of the uncoated POF, which is 0.0429 a.u/RIU.

Synthesis, analysis, and multi-faceted applications of solid wastes-derived silica nanoparticles: a comprehensive review (2010-2022).

The synthesis of silica nanoparticles (SiNPs) has emerged as an extensive area of research in the last century. Owing to their instinctive properties like modifiable mesoporous structure, high surface area, adjustable pore size, and pore volume, SiNPs could be utilized in numerous fields like chemical, biochemical, catalysis, adsorption, and pollution control. Conventionally, SiNPs are produced by tetraethylorthosilicate (TEOS), tetramethylorthosilicate (TMOS), and sodium silicate, which are toxic and expensive. Therefore, the development of green, cost-effective approaches for the synthesis of SiNPs is highly desirable. In this course, during the last decade, silica-rich solid wastes (rice husk, corn cob, sugarcane bagasse, palm ash, fly ash, waste glass, waste packaging materials, photonic industrial wastes, etc.) were acknowledged as economical precursors to produce green SiNPs. In this respect, the present review focuses on reviewing several solid waste materials used for the synthesis of SiNPs, their properties, and different characterization techniques used for the analysis of SiNPs. The present review also accounts for the potential applications of such green SiNPs in several fields like catalysis, adsorption, biomedical applications, and energy storage. Moreover, despite the potential applications of SiNPs, still there is a lot to explore about their synthesis and utilization. Hence, in the last section of this review, future scope, challenges, and risk assessment of SiNPs have been discussed.

Quaternary alloyed quantum dots with a wide-ranging tunable emission for high color-rendering white light-emitting diodes

Quaternary alloyed quantum dots (QDs) Ag-Zn-In-S(AZIS)/ZnS were prepared by using of heating-up method for the synthesis of AZIS cores followed by a hot-injection method for the shelling of ZnS. By regulating the Ag:Zn:In ratio, the peak emissions of the resulted AZIS/ZnS QDs exhibited an unreported wide ranging tunable emission from 475 nm to 645 nm. With the increasing silver components, redshift in the photoluminescence spectrum was observed. White light-emitting diodes (WLEDs) were fabricated successfully by employing the yellow-green emission AZIS/ZnS QDs and the combination of the green and the red emission ones as color converters respectively. These devices showed satisfied luminescent properties including a highest color-rending index of 88 accompanied by a corelated color temperature of 3260 K. However, AZIS/ZnS QDs integrated on the chips exhibited large redshift compared to their solution states. This redshift was suppressed remarkably by coating the as synthesized AZIS/ZnS QDs with a silica shell using the hydrolysis of tetramethoxysilane (TMOS). The WLEDs based on silica-coated AZIS/ZnS QDs showed an ultrahigh CRI of 96.3 accompanied by a CCT of 3653 K and good resistance to the invasion of room temperature and humidity after placed under room environment for 11 months. Possessing no heavy metal elements and satisfied luminescent properties combined with good resistance to the invasion of room temperature and humidity in devices make AZIS/ZnS QDs be expected to play a critical role in various applications of lighting.

Silica aerogel-filled polymer foams by emulsion-templating: One-pot synthesis, hierarchical architecture and thermal conductivity

The ability of combining different material chemistries to obtain hybrids with a hierarchical architecture is an emerging trend in materials engineering. In this article, we report on co-continuous organic–inorganic macro-mesoporous hybrid materials in which a Si-aerogel network is homogeneously intertwined with a macroporous polymer network, creating an architectural hierarchy. The main thrust of this manuscript is an innovative one-pot synthesis strategy that uses hydrosol-in-oil HIPEs (high internal phase emulsions) as structural templates, where polymerization of monomers in the external phase and hydrolytic condensation of tetramethyl orthosilicate in the internal phase occur simultaneously. The molecular and porous structures as well as thermal and mechanical properties are described and discussed in detail. The resulting multicomponent monoliths yield a hierarchically porous system with pronounced macro-mesoporosity and a specific surface area that increases from 5 m2·g−1 for the bare polyHIPE structure to as high as 242 m2·g−1 for the hybrid structure. The incorporation of Si-aerogel in the polyHIPE lowers its thermal conductivity to 27 mW·m−1·K−1, a value lower than that of commercial high-performance insulators such as superthermally insulating Styrofoam. The Si-aerogel content also affects the mechanical properties. The compressive modulus of the hybrid polyHIPEs increases with Si-aerogel content from 20 MPa for bare polyHIPEs to 98 MPa for the polyHIPEs with the highest Si-aerogel content.

Annealing and TMOS coating on PSF/ZTC mixed matrix membrane for enhanced CO2/CH4 and H2/CH4 separation.

Recently, natural gas (mostly methane) is frequently used as fuel, while hydrogen is a promising renewable energy source. However, each gas produced contains impurity gases. As a result, membrane separation is required. The mixed matrix membrane (MMM) is a promising membrane. The huge surface area and well-defined pore structure of zeolite templated carbon (ZTC)-based MMM allow for effective separation. However, the interfacial vacuum in MMM is difficult to avoid, contributing to poor separation performance. This research tries to improve separation performance by altering membrane surfaces. MMM PSF/ZTC was modified by annealing at 120, 150, and 190°C; coating using 0.01, 0.03, and 0.05 mol tetramethyl orthosilicate (TMOS); and a combination of both, i.e. annealing at 190°C and coating using 0.03 mol TMOS. MMM PSF/ZTC successfully significantly improved CO2/CH4 selectivity by a combination of annealing at 190°C and coating 0.03 mol TMOS from 1.37 to 5.90 (331%), and H2/CH4 selectivity by coating with 0.03 mol TMOS from 4.58 to 65.76 (1378%). The enhancement of selectivity was due to structural changes to the membrane that became denser and smoother, which SEM and AFM observed. In this study, annealing and coating treatments are the methods investigated for improving the polymer matrix and filler particle adhesion.

Sustainable synthesis of ordered mesoporous materials without additional solvents

Micelles with well-defined nanostructures were generally formed in the presence of a suitable solvent. We report herein the accelerated construction of micelles with ordered nanostructures without assistance of additional solvents. The micelles were employed for ultrafast fabrication of ordered mesoporous silicas (OMS) using tetramethyl orthosilicate (TMOS) as silica source. When γ-aminopropyl triethoxysilane precursor was introduced, we obtained amine group (–NH2) decorated ordered mesoporous silicas (OMS-NH2-x, where x stands for the molar ratio of γ-aminopropyl triethoxysilane to TMOS). The resulted materials are large in BET surface area and tunable in content of –NH2 site, which are highly efficient for catalytic elimination of gaseous carbonyl sulfide and hydrogen sulfide. Using this strategy, other functionalized groups such as thiol and benzene can be also introduced into OMS. Furthermore, the introducing of phenolic precursor into the system leads to multiphase co-assembly for the formation of ordered mesoporous silica-polymer nanocomposites. It is demonstrated that the solvent-free ultrafast assembly offers a sustainable route for preparation of ordered mesoporous functional materials.

Interface-Engineered Hollow Nanospheres with Titanium(IV) Binding Sites and Microwindows as Affinity Probes for Ultrafast and Enhanced Phosphopeptides Enrichment.

Enrichment and identification of phosphopeptides in real biological samples are of great significance in many aspects. Herein, Ti4+-immobilized silica hollow nanospheres were tailored via chelating with phosphonic acid groups produced from dealkylation of phosphonate ester functionalized silica hollow nanospheres, which were synthesized through a single micelle templated method with diethylphosphatoethyltriethoxysilane (DPTES) and tetramethoxysilane (TMOS) as silane precursors under neutral conditions. The characterization results of transmission electron microscopy (TEM), nitrogen sorption isotherms, FT-IR, and energy-dispersive X-ray (EDX) spectroscopy confirmed the successful preparation of Ti4+-immobilized silica hollow nanospheres (SHS-Ti; approximately 17 nm particle size), which possessed a 10 nm hollow cavity with 1.6 nm micropores on the thin shell (about 3.5 nm). Attributed to the immobilized Ti4+ and high specific area (396 m2/g), SHS-Ti was applied as a Ti4+-immobilized metal affinity chromatography (Ti-IMAC) material and showed good specificity, a low limit of detection (5 fmol), high selectivity (tryptic digestion mixture of bovine serum albumin/β-casein, 1000:1 molar ratio), high binding capacity (120 mg/g for pyridoxal 5'-phosphate), and a high binding constant (1.30 × 103 L/mg). Particularly, benefiting from the unique hollow structure with microwindows on the thin shell, a short transport path, and small mass transfer resistance, SHS-Ti exhibited excellent enrichment speed in which both phosphopeptide loading and elution could be completed in 1 min. The 5298 unique phosphopeptides from 1618 unique phosphoproteins were identified after enrichment by SHS-Ti from 100 μg Jurkat cell lysates within three independent replicates. The results showed that SHS-Ti could be utilized as a novel and promising enrichment probe for phosphopeptide characterization in MS-based phosphoproteomics and related fields.

Cationic polyelectrolyte-assisted synthesis of silica nanochains for enhancing mechanical properties of sodium alginate composite films

For the improvement of the transparency of silica nanomaterials and their dispersibility in polymer films, a series of silica nanochains were synthesized via a simple and cost-effective self-assembly method. Herein, silica oligomers were prepared through chemical hydrolysis-condensation reactions of tetramethyl orthosilicate; the growth of negative-charged silica oligomers in the confinement of positive-charged poly(dimethyldiallylammonium chloride) (PDDA) led to the formation of silica nanochains. By tuning the synthesis parameters (i.e., PDDA concentration, reaction temperatures, water:ethanol volume ratios, and ammonium water contents), it is possible to control the structure of silica nanochains and subsequently mechanical properties of sodium alginate (SA) composite films. Using optimal synthesis parameters, the obtained silica nanochains exhibited exceptional performances with high transparency, excellent hydrophilicity and good dispersibility, which surpassed silica nanospheres. Compared with pure SA film, the tensile strength and storage modulus in the glassy region of the SA composite film containing 0.5 wt% silica nanochains was improved by 93.0% and 824.7%, respectively. The work demonstrates the great promise of such silica nanochains toward practical application in optoelectronic thin-film materials.

Hydrogel-Coated Gate Field-Effect Transistor for Real-Time and Label-Free Monitoring of β-Amyloid Aggregation and Its Inhibition.

In this paper, we propose a hydrogel-coated gate field-effect transistor (FET) for the real-time and label-free monitoring of β-amyloid (Aβ) aggregation and its inhibition. The hydrogel used in this study is composed of poly tetramethoxysilane (TMOS), in which Aβ monomers are entrapped and then aggregate, and coated on the gate insulator; that is, Aβ aggregation is induced in the vicinity of the sensing surface. With the Aβ hydrogel-coated gate FET, the steplike decrease in the surface potential of the Aβ hydrogel-coated gate electrode is electrically monitored in real time, according to the stepwise aggregation of Aβ monomers to form into fibrils through oligomers and so forth in stages. This is because the capacitance of the Aβ-hydrogel membrane decreases depending on the stage of aggregation; that is, the hydrophobicity of the Aβ-hydrogel membrane increases stepwise depending on the amount of Aβ aggregates. The formation of Aβ fibrils is also confirmed in the measurement solution using a fluorescent dye, thioflavin T, which selectively binds to the Aβ fibrils. Moreover, the addition of daunomycin, an inhibitor of Aβ aggregation, to the measurement solution suppresses the stepwise electrical response of the Aβ hydrogel-coated gate FET. Thus, a platform based on the Aβ hydrogel-coated gate FET is suitable for a simple screening system for inhibitors of Aβ aggregation, which may lead the identification of potential therapeutic agents for Alzheimer's disease.

The Evaluation of Counter Diffusion CVD Silica Membrane Formation Process by In Situ Analysis of Diffusion Carrier Gas.

A new evaluation method for preparing silica membranes by counter diffusion chemical vapor deposition (CVD) was proposed. This is the first attempt to provide new insights, such as the decomposition products, membrane selectivity, and precursor reactivity. The permeation of the carrier gas used for supplying a silica precursor was quantified during the deposition reaction by using a mass spectrometer. Membrane formation processes were evaluated by the decrease of the permeation of the carrier gas derived from pore blocking of the silica deposition. The membrane formation processes were compared for each deposition condition and precursor, and the apparent silica deposition rates from the precursors such as tetramethoxysilane (TMOS), hexyltrimethoxysilane (HTMOS), or tetraethoxysilane (TEOS) were investigated by changing the deposition temperature at 400–600 °C. The apparent deposition rates increased with the deposition temperature. The apparent activation energies of the carrier gas through the TMOS, HTMOS, and TEOS derived membranes were 44.3, 49.4, and 71.0 kJ mol−1, respectively. The deposition reaction of the CVD silica membrane depends on the alkoxy group of the silica precursors.

Consolidation of volcanic tuffs with TEOS and TMOS: a systematic study

In this study, nine volcanic tuffs from Armenia, Germany and Mexico were treated with two commercially available consolidants on base of silicic acid ester, as well as different pretreatments with an anti-swelling agent and/or primer components. Prior to the treatment, the tuffs were analyzed regarding their petrography and mineralogy, with a greater focus on their clay mineral content. The effect of the consolidation was evaluated by comparative analyses of petrophysical properties and weathering behavior before and after the treatments. The main goals of this study were to identify a general suitability of different consolidating treatments for different types of tuff, evaluating tartaric acid as a primer component for tuff consolidation and to pursue the approach of finding a molecular answer for apparent tuff consolidation problematics, by testing a consolidation agent with smaller molecule sizes than current products on the market: tetramethoxysilane (TMOS).