Concentration Of Silanol Groups Research Articles

Bioactive Glasses Modulate Anticancer Activity and Other Polyphenol-Related Properties of Polyphenol-Loaded PCL/Bioactive Glass Composites.

In this work, bioactive glass (BG) particles obtained by three different methods (melt-quenching, sol-gel, and sol-gel-EISA) were used as modifiers of polyphenol-loaded PCL-based composites. The composites were loaded with polyphenolic compounds (PPh) extracted from sage (Salvia officinalis L.). It was hypothesized that BG particles, due to their different textural properties (porosity, surface area) and surface chemistry (content of silanol groups), would act as an agent to control the release of polyphenols from PCL/BG composite films and other significant properties associated with and affected by the presence of PPh. The polyphenols improved the hydrophilicity, apatite-forming ability, and mechanical properties of the composites and provided antioxidant and anticancer activity. As the BG particles had different polyphenol-binding capacities, they modulated the kinetics of polyphenol release from the composites and the aforementioned properties to a great extent. Importantly, the PPh-loaded materials exhibited multifaceted and selective anticancer activity, including ROS-mediated cell cycle arrest and apoptosis of osteosarcoma (OS) cells (Saos-2) via Cdk2-, GADD45G-, and caspase-3/7-dependent pathways. The materials showed a cytotoxic and antiproliferative effect on cancerous osteoblasts but not on normal human osteoblasts. These results suggest that the composites have great potential as biomaterials for treating bone defects, particularly following surgical removal of OS tumors.

Confinement and Polarity Effects on the Peptide Packing Density on Mesoporous Silica Nanoparticles.

The adsorption of cationic peptide JM21 onto different mesoporous silica nanoparticles (MSNs) from an aqueous solution was studied as a function of pH. In agreement with the literature, the highest loading degrees could be achieved at pH close to the isoelectric point of the peptide where the peptide-peptide repulsion is minimum. However, mesopore size, mesopore geometry, and surface polarity all had an influence on the peptide adsorption in terms of both affinity and maximum loading at a given pH. This adsorption behavior could largely be explained by a combination of pH-dependent electrostatic interactions and confinement effects. It is demonstrated that hydrophobic interactions enhance the degree of peptide adsorption under pH conditions where the electrostatic attraction was absent in the case of mesoporous organosilica nanoparticles (MONs). The lower surface concentration of silanol groups for MON led to a lower level of peptide adsorption under optimum pH conditions compared to all-silica particles. Finally, the study confirmed the protective role of MSNs in preserving the biological activity of JM#21 against enzymatic degradation, even for large-pore MSNs, emphasizing their potential as nanocarriers for therapeutic peptides. By integrating experimental findings with theoretical modeling, this research elucidates the complex interplay of factors that influence peptide-silica interactions, providing vital insights for optimizing peptide loading and stabilization in biomedical applications.

Regulable surface hydroxyl group content in disperse ultrafine amorphous SiO2 nanoparticles

AbstractAmorphous silica (SiO2) nanoparticles (NPs) can be applied in environmental pollutant remediation, element removal, and water purification. The content of surface silanol groups in amorphous SiO2 NPs affects the characteristics of SiO2 NPs. However, the regulation of surface silanol group content in amorphous SiO2 NPs below 10 nm remains a challenge. Herein, tunable surface silanol group content was achieved in disperse ultrafine amorphous SiO2 NPs by controlling calcination and rehydroxylation. The surface silanol group content in amorphous SiO2 NPs is low (10 nm) and can be tuned from 0% to 2.5%. The amount of naphthalene adsorbed by the SiO2 NPs increases with increasing surface silanol group content. The surface silanol group content in SiO2 NPs can be an effective means to tune their adsorption performance and applications.

Alternative Synthesis of MCM-41 Using Inexpensive Precursors for CO2 Capture

We explore the use of industrial sources of silicon and surfactant for obtaining low-cost MCM-41 materials and evaluate their performances as CO2 adsorbents. All of them presented a high specific surface area with different structural characteristics and textural properties. Interestingly, the MCM-41 manufactured with the most economical reagents presented a SBET of 1602 m2·g−1. The template was removed by using thermal treatments in an air atmosphere or a washing process. Preservation of silanol groups proved to be more effective under washing or mild thermal treatment conditions with the advantage of their lower cost and environmental benefit. Surface reactivity against CO2 was enhanced by anchoring APTS to silanol groups through wet grafting. All amino-functionalized materials showed a performance as CO2 adsorbents comparable to those reported in the literature, reaching values close to 30 cm3·g−1 at 25 °C and 760 mmHg. Samples with a higher concentration of silanol groups showed better performance. Our studies indicate that adsorbed CO2 is retained at least up to 50 °C, and the CO2 is chemisorbed on the silica modified with amine groups. The chemisorbed gas at very low pressures points to the potential use of these materials for CO2 storage.

Development of sulfhydryl grafted hierarchical porous geopolymer for highly effective removal of Pb (II) from water

Geopolymers have captured increasing attention in the adsorption of lead ions due to their zeolite-like three-dimensional network structure, and several advantages such as low cost and environmental friendliness. However, their adsorption performance is limited by a small specific surface area and fewer adsorption sites. In this study, a metakaolin-based geopolymer was first pretreated with different concentrations of nitric acid to increase the porosity and surface area. Subsequently, the sulfhydryl functional group was grafted onto the above hierarchical porous geopolymer, which is a inorganic material with multistage pore structure. The result of N2 adsorption and desorption results demonstrated that an increase in specific surface area and number of grafting sites for sulfhydryl groups with increasing acid concentration when the highest nitric acid concentration used is 5 mol/L and acid treatment time is for 5 h. The specific surface area of the fabricated geopolymers was as high as 343.87 m2/g and the concentration of silanol groups reached 4.46 mmol/g at 3 mol/L acid concentration. The maximum Pb2+ adsorption quantities for SH-1HGeo, SH-2HGeo, and SH-3HGeo samples were 173.2 mg/g, 239.8 mg/g, and 386.3 mg/g, respectively. The adsorption processes were in accordance with the pseudo-second-order kinetic model and the Langmuir models, indicating that the Pb2+ adsorption on the sulfhydryl grafted hierarchical porous geopolymer was mainly chemisorption and monolayer adsorption. The contribution of different Pb2+ adsorption mechanism on geopolymer was ion-exchange, while that on SH-3HGeo was functional group complexation.

Sour Gas Adsorption on Silica Gels.

One of the essential factors for water adsorption on silica gels is the concentration of silanol groups on the silica surface. However, no systematic investigation on the adsorption of sour gas components, methane (CH4), carbon dioxide (CO2), and hydrogen sulfide (H2S) on silica gels with different textural properties and surface silanol concentrations, has been conducted. Three silica gels of 22, 30, and 60 Å pore sizes, with silanol concentrations of αtotal = 2.516, 2.340, and 2.152 OH nm-2, respectively, were studied in this work. The adsorption data for CH4, CO2, H2S, and H2O at T = 0, 25, and 50 °C on the 22 and 30 Å pore size silica gels were presented, and a comparison of the data for the 60 Å pore size silica gel on the same adsorbates was conducted. All three silica gels showed an adsorption affinity in the order of H2O > H2S > CO2 > CH4. The isosteric heats of adsorption of H2O and H2S had a greater dependence on the silanol concentration than CO2 and CH4. At p < 10 bar, there was no difference in the adsorption per m2 of CH4 between the silica gels (n ads = 1.7 mmol m-2, for all silicas at p = 10 bar), while higher pressures resulted in greater adsorption capacity in the larger pore volume silica gels (at p = 20 bar: n ads = 3.0, 3.3, and 3.4 mmol m-2 for the 22, 30, and 60 Å pore size silicas, respectively). H2S adsorption at low pressures (p < 4 bar) was larger on the samples with larger silanol concentrations (at p = 3 bar: n ads = 6.1, 4.7, and 4.5 mmol m-2 for the 22, 30, and 60 Å pore size silicas, respectively), but above p = 4 bar, the 60 Å pore size silica had a greater adsorption capacity than the 30 Å pore size (at p = 5 bar: n ads = 8.0, 6.0, and 6.2 mmol m-2 for the 22, 30, and 60 Å pore size silicas, respectively).

Hydrothermal rehydroxylation of SBA-15 material: Effect of initial silanol concentration and pore size on the textural properties

Materials SBA-15 were synthesized with different initial concentrations of silanol groups. These groups depend on the calcination temperatures 350 °C, 450 °C, 550 °C, 650 °C, and 750 °C; which produced an initial concentration (mmol g−1) of 4.1, 3.1, 1.8, 1.8, and 1.6 respectively. Textural properties of materials were analyzed by nitrogen adsorption and powder X-ray diffraction (XRD). Furthermore, silanol concentration was analyzed using thermogravimetric analysis (TGA). Finally, silanol species were obtained by 29Si nuclear magnetic resonance (NMR). The materials were submitted to a hydrothermal treatment at 80 °C for 12 or 24 h. After hydrothermal treatment, all the materials increased their silanol concentration. Materials with a higher initial concentration of silanol groups and larger pore diameters presented more significant changes in their textural properties. Thus, the material with 4.1 mmol g−1 (calcined at 350 °C) showed a decrease in its specific surface area of 33% and an increase in its pore diameter of 4%, while the material with 1.6 mmol g−1 (calcined at 750 °C) only presented a decrease in its specific surface area of 8% and no changes in its pore diameter.

Chemical and Structural Comparison of Different Commercial Food Supplements for Silicon Uptake

Various food supplements for silicon uptake were compared in terms of their structures and chemical compositions. In particular, we analyzed the silanol group content, which can be an indicator of the uptake of the siliceous species in the human body. We analyzed the commercial products Original Silicea Balsam®, Flügge Siliceous Earth Powder, Pure Colloidal Silicon, and BioSil® by applying various methods such as FTIR, 29Si NMR, and TGA. The Si-OH group content of the samples containing pure silica was the highest for the Original Silicea Balsam followed by the Pure Colloidal Silicon. The siliceous earth powder revealed the lowest content of such groups and the densest structure. BioSil® contained a considerable concentration of organic molecules that stabilized orthosilicic acid. The study may help to understand the silicon uptake behavior of different food supplements depending on their chemical structure.

Unraveling the Effect of Silanol Defects on the Insertion of Single-Site Mo in the MFI Zeolite Framework.

The preparation of defect-free MFI crystals containing single-site framework Mo through a hydrothermal postsynthesis treatment is reported. The insertion of single Mo sites in the MFI zeolite samples with different crystal sizes of 100, 200, and 2000 nm presenting a diverse concentration of silanol groups is revealed. The nature of the silanols and their role in the incorporation of Mo into the zeolite structure are elucidated through an extensive spectroscopic characterization (29Si NMR, 1H NMR, 31P NMR, and IR) combined with X-ray diffraction and HRTEM. In addition, a DFT-based theoretical modeling of a large Si154O354H92 nanoparticle containing 600 atoms is carried out to understand the expansion of the unit cell volume measured by X-ray diffraction. An accurate quantification of the silanols in the MFI crystals with different particle sizes and the insertion of Mo in the zeolitic framework is reported for the first time. The results confirmed that the non-H-bonded silanols seem to be the gateway for the insertion of single Mo atoms in the zeolite structure. Such materials with single metal sites present high crystallinity and perfect structure, thus providing great stability in catalytic applications.

The biogenic silica-derived Ni-phyllosilicate catalyst with Ru modification: effect of the hydroxylation enhancement and reduction procedure

Ni-phyllosilicate is difficultly formed on the surface of biogenic silica (E) extracted from equisetum fluviatile after calcination, resulting in poor catalytic activity at low temperature (<400 °C). In this work, the hydroxylation treatment of E was carried out to address the problem of lack of the surface silanol group and difficult formation of Ni-phyllosilicate, and the second metal Ru was added using a special procedure to further improve the activity of the catalyst. The surface silanol group concentration of silica (HE) was increased from 0.5 to 0.7 mmol/g after hydroxylation treatment, resulting in formation of more Ni-phyllosilicate with Ni content increase from 11.3 to 17.0 wt%. Considering the great gap of reduction difficulty of Ni-phyllosilicate (>800 °C) and RuO2 species (190 °C), RuO2 species was doped onto the 750 °C-pre-reduced Ni-phyllosilicate via impregnation, and metallic Ru together with Ni could be obtained simultaneously after reduction at a low temperature of 400 °C. The obtained Ru-modified Ni-phyllosilicate catalyst showed high CO2 conversion of 77.3% and CH4 selectivity of 96.4% with high turnover frequency (1.22 s−1, 180 °C) and low activation energy (71.25 kJ/mol). In situ Diffused Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) results revealed that more active formate intermediates (m-HCOO- and m-CO32−) result in high catalytic activity of the Ru-modified Ni-phyllosilicate catalyst. In addition, this catalyst exhibited high anti-sintering property, long-term stability, and hydrothermal stability under severe conditions owing to the Ni-phyllosilicate–based structure.

Determination of silanol group content on the surface of fumed silica by chemical reaction-headspace gas chromatography

建立了一种基于化学反应-顶空气相色谱测定气相二氧化硅表面硅羟基含量的新方法。实验取气相二氧化硅放入顶空瓶中于105 ℃烘箱中加热2 h去除水分,将甲苯稀释的格氏试剂注入密闭的顶空瓶中,格氏试剂与气相二氧化硅表面硅羟基快速反应产生甲烷(CH4),甲烷量与气相二氧化硅表面硅羟基含量成正比。经过气相色谱-氢火焰离子化检测器测定甲烷,通过外标法定量,根据化学反应方程式计算出样品中羟基含量。同时对反应溶液用量与反应时间等条件进行优化,确定2.0 mL反应溶液,反应15 min为最优的前处理条件。结果表明,硅羟基含量与气相色谱信号值之间存在良好的线性相关性,相关系数为0.9990,相对标准偏差小于3%,本方法的检出限为0.30 mg/g,定量限为1.00 mg/g,开展了4家实验室对5个不同比表面积的样品测试,数据结果的重复性限(r)小于2.5%,再现性限(R)小于6.5%。该方法结合自动化技术,顶空反应操作简单,样品量和试剂用量少,准确性高,重复性好,优于酸碱滴定法,适用于快速检测气相二氧化硅表面硅羟基的含量,解决了硅羟基利用传统方法难以准确测定的难题。该方法的建立对我国二氧化硅产业硅羟基检测标准的制定和产业技术优化,均具有重要的理论和现实意义。

Nickel phyllosilicate derived Ni/SiO2 catalysts for CO2 methanation: Identifying effect of silanol group concentration

For the conventional Ni/SiO2 catalyst, the weak metal-support interaction usually resulted in serious Ni sintering at high temperature. To address this problem, a group of Ni-phyllosilicate-derived Ni/SiO2 catalysts were synthesized via the hydrothermal reaction of nickel nitrate and mesostructured silica nanoparticles (MSN) with three different sizes of 99 (MS), 184 (MM), and 725 (ML) nm. The Ni contents of three nickel phyllosilicate catalysts varied from 5.9 to 19.7 wt%, which exhibited a reverse order of the particle size. It was found that the concentration of silanol group (SiOH) of MSN significantly affected the construction of Ni-phyllosilicate material. The surface silanol group concentration increased with the decrease of particle size of MSN, resulting in the improved formation of nickel phyllosilicate and enhanced catalytic activity for CO2 methanation. Among all catalysts, MS/H-24 showed the highest CO2 conversion of 76.5 % at 450 °C due to the highest Ni dispersion and largest CO2 and H2 uptakes. In addition, the optimal catalyst exhibited higher anti-sintering property, long-term stability and hydrothermal stability than an impregnated catalyst (Ms/Im) with the similar Ni content in a lifetime test (450 °C, 100 h) and steam treatment test (600 °C, 6 h), owing to its strong metal-support interaction derived from nickel phyllosilicate.

Increasing the Uniformity of Nano-Dispersed SiO&lt;sub&gt;2 &lt;/sub&gt;Distribution in Polymeric Binder of Composite Material

Ultrasonic dispersion of a silica hydrosol is compared with the effects of mechanical activation through the combined action of high shear stresses, ultrasound and cavitation. This action leads to breaking the siloxane bonds and increasing the content of silanol groups. The mechanical activation of binary silica system with acrylate dispersion promotes a chemisorption of oligoacrylate with the formation of Si – O – C and Si – C bonds. The effect of modification of oligoacrylate on the formation of a graft-copolymer and the stiffness of a composite material was evaluated.

Influence of Wettability on the Impedance of Ion Transport Through Mesoporous Silica Films

AbstractFunctionalized nanopores have attracted strong interest in different fields in which nanopore transport is essential. Detailed insights into mass transport through nanopores and its correlation to pore wall properties such as wettability are essential. The potential and challenges using electrochemical impedance spectroscopy (EIS) to analyze mass transport through mesoporous silica thin films with precisely adjusted wettability are discussed. The accessible area of the electrode, the charge transfer or film resistance and the diffusion coefficients of the redox probe [Ru(NH3)6]2+/3+ inside the mesopores are determined. The influence of experimental parameters such as silica film pre‐treatment is evaluated. Hydrophilic mesoporous films display comparable diffusion coefficients around 1*10–8 cm2 s–1 independently of the exact wettability. As expected, hydrophobic films do not exhibit transport due to water exclusion. The sample pre‐treatment strongly influences the transport characteristics. Incubation into aqueous KCl leads to a decrease in the resistance for all tested mesoporous films. This is ascribed to an increase in the silanol group concentration at the pore wall. Besides the insights into mass transport in mesoporous films and on how to measure EIS in such films, this study elucidates the importance of sample pre‐treatment and surface chemistry concerning mesoporous film performance.

Synthesis and comparative characterization of functionalized nanoporous silica obtained from tetrachloro- and tetraethoxysilane by a sol-gel method

Functionalized silica supports were synthesized under various conditions using tetraethoxysilane (TEOS) and silicon tetrachloride (STC) as precursors by the sol-gel method. The polyethylene glycol with a molecular weight of 1500 was used as a structure-controlling agent. The use of STC as a SiO2 precursor allowed getting a higher specific surface area in comparison with TEOS. The influence of hydrothermal and acidic treatment on the specific surface area of the obtained structures was studied. The concentration of silanol groups was evaluated applying diffuse reflectance infrared Fourier transform spectroscopy. SEM micrographs showed that the use of toluene as an additional solvent of polyethylene glycol led to the formation of the agglomerates from sphere-shaped SiO2, meanwhile, the use of hexane led to the formation of a rhombohedral cell structure.

Modified Organosilane Monolayers With Enhanced Radiation Stability.

Organosilane monolayers containing long carbon chains are susceptible to damage when exposed to X-rays and other radiation during characterization or processing. The origin of the damage has been attributed to both energetic photons and photoelectrons. These particles can break bonds in the molecules comprising the layer altering its composition and structure and can create silanol groups at the interface between the monolayer and the silicon dioxide surface. A common practice to minimize damage is to keep the X-ray beam time as short as possible. In this study, we report a method to deposit an organosilane monolayer on silicon dioxide that withstands X-ray beam damage to the interface. Adding the small monofunctional trimethylchlorosilane to a layer composed of the long-chain trifunctional octadecyltrichlorosilane prevented X-ray beam damage for at least 4 h. Interfacial damage was monitored by titrating silanol groups with TiCl4 and water atomic layer deposition and measuring the TiO2 deposited by X-ray photoelectron spectroscopy (XPS). The small monofunctional silane reacted with residual silanol groups capping the siloxane (-Si-O-Si-O-) chains at the interface. The low silanol group concentration minimized X-ray beam damage and prevented TiO2 from depositing to the detection limit of XPS. Using a small molecule to terminate reactive groups could improve the stability of monolayers not only during characterization and processing, but also when the monolayer is a component in an electrical device by reducing sources of interfacial charge traps.

Comparative study of the thermal diffusivity of SiO2–Au nanoparticles in water base

Two SiO2–Au nanoparticles were prepared. Silicon dioxide (SiO2) structures with average size of 143 and 90 nm were synthesized using the sol–gel method. Gold (Au) nanoparticles of ~ 5 nm were deposited using the deposition–precipitation process on each dielectric platform. The concentration of silanol groups of SiO2 spheres was obtained. The size and form of SiO2, Au and SiO2–Au nanoparticles were evaluated by transmission electron microscopy (TEM). The TEM micrographs confirmed the size and spherical form for SiO2 and Au nanoparticles with high monodispersity, the decoration of SiO2 spheres with metallic nanoparticles was also confirmed. The reflectance spectrum revealed a decreased of reflectivity around 516 nm for SiO2–Au structures, the decrease of reflectance was associated with the presence of gold nanoparticles on dielectric spheres. The SiO2–Au structures (at different mass 0.1–0.6 mg/ml) were dispersed in deionized water. Thermal diffusivity of SiO2–Au particles in water was studied using the thermal lens (TL) spectroscopy. The results revealed an increase in thermal diffusivity as the SiO2–Au concentration was increased. The thermal property was independent on the size of the SiO2 spheres used.

Synthesis of hierarchically porous silica aerogel supported Palladium catalyst for low-temperature CO oxidation under ignition/extinction conditions

Abstract Synthesis of well-dispersed palladium nanoparticles within silica aerogel pores with controlled size was carried out using sol-gel synthesis under supercritical ethanol drying. The high concentration of silanol groups on silica (SiO2) surface facilitated a superior palladium (Pd) loading up to 10 wt %. The synthesized Pd/SiO2 nanocomposite aerogels were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopic methods. The silica aerogel supported catalysts were found to have a wide pore size distribution. TEM investigations confirmed that Pd nanocrystals were located within the SiO2 microspores and mesopores. The catalyst was evaluated for carbon monoxide (CO) oxidation reaction under ignition/extinction conditions. The synthesized catalyst demonstrated a high catalytic activity at low operating temperatures (

Quantitative arrangement of Si/Al ratio of natural zeolite using acid treatment

Acid treatment is an effective way to arrange SiO2/Al2O3 ratio of natural zeolite. However, limited researches have been done on quantitative regulation of SiO2/Al2O3 ratio of natural zeolite. In this paper, an orthogonal test was designed to optimize the acid treated conditions. Acid concentration, treated time and temperature were then employed to quantitatively arrange the SiO2/Al2O3 ratio of natural zeolite, respectively. The results showed that the primary and secondary factors of acid treatment were acid treated time, acid concentration and acid treated temperature, respectively. The extent of dealumination of zeolite and its corresponding SiO2/Al2O3 ratio of natural zeolite could rise up to 98.4% and 372.7 under the optimized condition for 48 h, 8 M and 70 °C, respectively. Acid concentration, treated time and temperature could effective quantitatively arrange the extent of dealumination of zeolite and SiO2/Al2O3 ratio of natural zeolite. The as-prepared acid treated zeolites with different SiO2/Al2O3 ratio regulated by acid concentration had higher specific surface area, micropore volume, silanol group content and hydrophobicity than those for the natural zeolite.

Silica- and diatomite-modified fluorine rubber nanocomposites

To find the most suitable filler system for fluorine rubber, a simple and green method to introduce a limited content of silanol groups on the surfaces of silica and fluorine rubber was studied. Fluorine rubber nano-composites were prepared by using nano-silica, diatomite and carbon black as the reinforcement and filler and the coupling agents KH550, KH590 or Si69 as the compatibilizer between the filler and fluorine rubber. The structure and morphology of the composites were investigated by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The results showed that the most suitable filler system for fluorine rubber was the diatomite and silica compound (8:12 mass ratio), the best coupling agent was KH550 at 2 parts per hundred rubber (phr). The modified compound filler was silanized with the coupling agent KH550 for fluorine rubber by FTIR analysis, the compatibility between the filler and fluorine rubber was improved by SEM analysis and further confirmed by thermogravimetric analysis to improve the thermal properties of fluorine rubber with the filler compound system.