Tetra Orthosilicate Research Articles

Synthesis and characterization of Guar gum based biopolymeric hydrogels as carrier materials for controlled delivery of methotrexate to treat colon cancer

Guar Gum has been evaluated for its importance in food and pharmaceutical industry. A blended biopolymeric hydrogel was prepared by solution casting technique using guar gum (GG), chitosan (CS), polyvinyl alcohol (PVA), chemically crosslinked with tetra orthosilicate (TEOS) and impregnated with methotrexate (MTX) to assess its drug carrying capacity against colon cancer (HCT-116). The surface morphology, chemical bonding, hydrophilicity and water absorbing capacity were analyzed by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), contact angle measurements and swelling properties in variable conditions. Furthermore, degradation, drug release kinetics, hemocompatibility, and cytotoxicity of MTX-loaded hydrogel was tested. The release of MTX from GG/CS/PVA biopolymeric blend occurred in sustained manner. Results displayed that in 7 h 25 min duration 96% of the drug was released in phosphate buffer saline (PBS) at pH 7.4. These blends were non-hemolytic, and antiproliferative against HCT-116. Furthermore, the MTT assay has revealed that MTX-loaded hydrogel had prominently decreased the cell viability (with IC50 11.7 µg/ml) as compared to free MTX (with IC50 21.57 µg/ml). Hence, these results suggest that guar gum based hydrogels are potential biomaterials for colon cancer treatment.

CO2 methanation with Ru@MIL-101 nanoparticles fixated on silica nanofibrous veils as stand-alone structured catalytic carrier

An important challenge in the valorization of CO2 and H2 into fuels is the development of a stable, reusable and easy to handle heterogeneous catalyst. Here, a silica nanofibrous membrane is investigated as carrier for Ru nanoparticles, themselves encapsulated inside the metal organic framework (MOF) Cr-MIL-101. The catalytic membrane is investigated for the Sabatier methanation reaction. The direct electrospinning of a tetraorthosilicate (TEOS) sol results in a highly thermal resistant silica nanofibrous structure (up to 1100 °C) with pores between the fibers in the µm-range, allowing a high gas throughput with low pressure requirements. A straightforward dip-coating procedure of the carrier was used to obtain a Ru@MIL-101 functionalized silica nanofibrous veil, avoiding Ru clustering. The obtained catalytic membrane exhibited an apparent turnover frequency of 3257 h-1 at 250 °C. This system therefore paves the way towards structured reactors for efficient CO2 hydrogenation processes.

Development of Antibacterial, Degradable and pH-Responsive Chitosan/Guar Gum/Polyvinyl Alcohol Blended Hydrogels for Wound Dressing.

The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels’ crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker–Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R2 = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications.

Chemical bonding of polycaprolactone on the surface of hydroxyapatite via silanization and ring opening polymerization

In this study, surface modification of hydroxyapatite (HAp) by grafting polycaprolactone (PCL) is described. This method is carried out into two steps: (1) A treatment of HAp powder with a mixture of tetraorthosilicate (TEOS) and 3-aminopropyl-etriethoxysilane (APTES) to introduce amine groups and enhance nucleophilicity of surface functionalities; (2) Initiation of the Ring Opening Polymerization (ROP) of the ε-caprolactone (CL) in the presence of the silanized HAp. Moreover, the impact of the reaction time (24, 48 and 72 h) on the grafting amount of PCL is performed. The results of FTIR analysis confirmed the presence of carbonyl groups on the silanized HAp, providing evidence of grafting of PCL on the HAp surface. WAXS pattern showed no formation of a secondary phase after surface modification and the crystallinity is preserved. SEM/TEM analysis revealed a homogenous surface powder composed of irregular nanoscale crystals. TGA analysis indicated the dependence of PCL graft amount on the reaction time. Finally, the effect of surface modification on HAp/PCL nanocomposites morphology was investigated.

Study of the Photocatalytic Activity Using Silica-Based Materials Doped with Silver Nanoparticles for Degradation of Rhodamine B Dye

Rhodamine B (RhB) is a cationic organic dye widely used industrially, mainly in the textile and food industries. Then, the work aims to study on the photocatalytic degradation of RhB dye, under UV and visible radiation, using photocatalyst silica-based materials synthesized by sol-gel route with different solvents (ethanol and n-propanol) and catalysts (C12H27N, HNO3, NH4OH, and NaOH) to the hydrolysis and condensation of tetraorthosilicate (TEOS). In addition, the effect of doping with silver nanoparticles (AgNPs) was evaluated on the photocatalytic activity. The samples were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), N2 porosimetry, zeta potential measurements (ZP), and Fourier transform infrared spectroscopy (FTIR). To evaluate the photocatalytic activity, photocatalytic tests were carried out in a stirred batch reactor, with the photocatalyst in suspension, under ultraviolet and visible radiation, and the target molecule chosen was the Rhodamine B dye (RhB). The photocatalyst Si–HNO3–AgNPs showed the best photocatalytic activity with a degradation of the RhB dye of 90.16% (k = 0.0198 min−1, under ultraviolet radiation) and 82.79% (k = 0.0148 min−1, under visible radiation), after 120 min of reaction; while under the same conditions, the commercial catalyst TiO2 (P25) showed a degradation of 50.02% and 42.14%, respectively.

Organo-silica membrane for brine water pervaporation

Pervaporation is currently used for brine water desalination. This high water salt content may impact the environment if it may not be treated. So, in this paper demonstrates the performance of organo-silca membrane to produce potable water from brine water. Organo-silica membrane was employed by sol gel process for 3 hours using tetra orthosilicate (TEOS) as precursor as well as dual catalyzed (organo catalyst/citric acid) and base (ammonia) on reflux temperature of 0°C. The molar ratios were 1:38:0.0007:5:003 for TEOS:EtOH:Citric Acid:H2O:NH3. Organo-silica membrane was applied in various artificial brine water (7.5-15 wt % NaCl) operated at 40 and 60°C as feed temperatures. The citric acid was chosen as carbon source to increase the carbon chains in the silica matrices. It was found that the water flux was increased as the feed temperature also increased from 40°C (1.27 kg.m2.h−1) to 60°C (1.55 kg.m2.h−1). Organo–silica membranes can produce water with a salt rejection of >90%.

Bisphenol A adsorption in aqueous medium by investigating organic and inorganic components of hybrid polymer (polyvinylpyridine/SiO2/APTMS)

The synthesis, characterization, and evaluation of new hybrid polymers towards bisphenol A (BPA) adsorption in aqueous medium were described. Different parameters related to the synthesis, such as catalyst nature, solvent type and the influence of 4-vynilpyridine (4-VP), 3-aminopropyltrimethoxysilane (APTMS) and tetraorthosilicate (TEOS) were investigated. The synthesized materials were named as polyvinylpyridine/SiO2/APTMS, polyvinylpyridine/SiO2, and polyvinylpyridine and characterized by FT-IR, SEM, TGA, elemental analysis and nitrogen adsorption/desorption measurements, as well as by kinetics and isotherms assays. From textural data results and binding adsorption assays, it was observed that the presence of APTMS in the hybrid polymer (polyvinylpyridine/SiO2/APTMS) gives rise to a adsorbent with lower adsorption capacity towards BPA and lower porosity. On the other hand, the presence of TEOS in the hybrid polymer (polyvinylpyridine/SiO2) provided a substantial improvement on the surface area and satisfactory adsorption capacity towards BPA compared with polyvinylpyridine/SiO2/APTMS. The organic polymer polyvinylpyridine, in turn, presented a slight superior adsorption capacity towards BPA (295 mg g−1) and lower surface area (75.1 m2 g−1) compared with polyvinylpyridine/SiO2 (232 mg g−1 and 132.5 m2 g−1), but drawbacks of overpressure when packed into extraction columns, which limits its use in solid phase extraction (SPE) procedures. Therefore, polyvinylpyridine/SiO2 has demonstrated the best performance towards BPA adsorption in aqueous medium, thereby showing the symbiosis of organic and inorganic components for obtaining materials with complementary properties.

Facile synthesis of hollow bioactive glass nanospheres with tunable size

Hollow nanospherical bioactive glasses were conducted though sol–gel process using poly(acrylic acid) (PAA) as the template. The incorporation of PAA was to form the core after air combustion, whereas the inorganic shell was produced by glass precursor. The mixture of different tetraorthosilicate (TEOS)/PAA contents into a glass network tailored the shell thickness, morphological, and structural properties of HBGs. The in vitro bioactivity evaluation confirmed that HBG2 sample exhibited good apatite formation ability, thereby denoting that the proposed method enhanced the potential application of HBGs in bone tissue regeneration and drug delivery.

Roll-to-roll fabrication of high surface area mesoporous carbon with process-tunable pore texture for optimization of adsorption capacity of bulky organic dyes

Large-scale (multigram-to-kilogram) fabrication of soft-templated ordered mesoporous carbon (OMC) is enabled by roll-to-roll (R2R) processing via evaporation induced self assembly of Pluronic F127, oligomeric phenolic resin (resol), and tetraorthosilicate (TEOS) from ethanolic solution. The solution concentration, TEOS loading (etchable for microporous framework), and crosslinking temperature impact the pore structure. Here we demonstrate that mesoporous carbons with surface areas up to 2455 m2/g can be obtained under the proper processing conditions. Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and nitrogen adsorption–desorption isotherms reveal (i) suppressed framework shrinkage with increasing solution concentration during casting, (ii) improved long range order and higher surface area with increasing TEOS content up to 3:1 TEOS:resol, and (iii) enhanced porosity with crosslinking at 100 °C. These differences can be explained on the basis of block copolymer thermodynamics and mechanical reinforcement by silica. This family of OMCs are effective adsorbents for bulky aqueous organic dyes, such as methylene green (MG) and methyl blue (MB), with high adsorption capacities of 0.436 g MG/g OMC and 0.378 g MB/g OMC obtained. This R2R method provides a facile method to generate significant quantities of OMCs with tunable pore textures.

Synthesis and CO2 sorption of silica particles, kinetics and thermodynamics

Spherical ordered mesoporous silica particles with radially oriented mesopores were successfully prepared by using non-ionic amphiphilic di-block co-polymers CnH2n+1-(EO)x-OH as template and tetraorthosilicate (TEOS) as silica precursor. The synthesized mesoporous silica materials were characterized by XRD, N2 adsorption-desorption and SEM techniques. CO2 adsorption at 0 °C was evaluated by a volumetric method, and the CO2 sorption behavior was described by applying both Langmuir and Freundlich equations. Results indicate a high adsorption capacity of CO2 (5-9 mmol/g), depending essentially on the porous texture of the materials. An adsorption kinetic model was proposed to describe the adsorption of CO2 over template-free mesoporous siliceous materials. A good agreement with experimental data was found.

Corrosion resistance properties of hybrid organic–inorganic epoxy–amino functionalised polysiloxane based coatings on mild steel in 3·5%NaCl solution

New hybrid organic–inorganic coatings have been developed by reacting a mixture of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraorthosilicate (TEOS) with 2–4% aminoethylaminopropyl-methylsiloxane dimethylsiloxane (APDMS) copolymer as a modifier. The sol–gel polymerisation of the inorganic components was achieved by base catalysation using NaOH. The resultant base coating (CGA) was further modified using two different corrosion inhibitors: Moly-white 101-ED and Hfucophos Zapp yielding coatings (CGA-M) and (CGA-Z) respectively. The corrosion resistant efficiency of these coatings for the protection of mild steel sheets in 3·5%NaCl electrolyte was assessed using AC and DC electrochemical methods, notably, electrochemical impedance spectroscopy (EIS) and DC polarisation scans. Based on the results, the order of corrosion protection of the above coatings was in the order: CGA-M>>CGA-Z>CGA.

Experimental investigation of inorganic nanofiltration membranes prepared by atomic layer deposition and sol-gel methods for saltless water softening

This study explored saltless water softening with inorganic Nanofiltration (NF) membranes prepared by Atomic Layer Deposition (ALD) and a Tetraorthosilicate (TEOS) sol-gel process applied by the slip cast method. The experimental investigations were performed on different material-based inorganic NF membranes, including titanium dioxide (TiO2), alumina (Al2O3), silver (Ag) and iron oxide (Fe2O3). The experimental results demonstrated that saltless water softening can be achieved with high flux through the viable rejection of Ca2+ with an initial rate between 7.1% and 34.1% in a single pass flow through filter in a solution of 0.5 g L–1 CaCl2 at neutral pH. A maximum rejection of 28.7% and 29.5% was achieved for Ca2++ at pH 4 and pH 10, respectively. The highest hardness rejection was achieved with a 25% waste water volume. In the recirculating loop tests with the same solution, a rejection rate of 9% was achieved within 15 min at a flow rate of 0.3 L min–1.

Integrating sol–gel with cold plasmas modified porous polycaprolactone membranes for the drug-release of silver-sulfadiazine and ketoprofen

A controlled release system composed of surface modified porous polycaprolactone (PCL) membranes combined with a layer of tetraorthosilicate (TEOS)–chitosan sol–gel was reported in this study. PCL is a hydrophobic, semi-crystalline, and biodegradable polymer with a relatively slow degradation rate. The drugs chosen for release experiments were silver-sulfadiazine (AgSD) and ketoprofen which were impregnated in the TEOS–chitosan sol–gel. The surface modification was achieved by O2 plasma and the surfaces were characterized by water contact angle (WCA) measurements, atomic force microscope (AFM), scanning electron microscope and electron spectroscopy for chemical analysis (ESCA). The results showed that the release of AgSD on O2 plasma treated porous PCL membranes was prolonged when compared with the pristine sample. On the contrary, the release rate of ketoprofen revealed no significant difference on pristine and plasma treated PCL membranes. The prepared PCL membranes showed good biocompatibility for the wound dressing biomaterial applications.

Synthesis and characterization of SiO 2–CaO–P 2O 5 hollow nanospheres for biomedical applications

A ternary system of SiO 2–CaO–P 2O 5 hollow nanospheres has been successfully prepared by sol–gel method using polystyrene (PS) nanospheres as template. The inorganic shell was produced using tetraorthosilicate (TEOS) as the silica source and tri-calciumphospate as calcium and phosphorus sources, respectively. The positive surface charge of the template and the [template]/[TEOS] ratio were the key parameters for the creation of a stable primary inorganic network and the further growth of the shell. The removal of the polymeric core through a thermal treatment procedure created an inner void space with mean diameter 250 nm while the outer mean diameter was 330 nm.

Fine‐Tuning Mesochannel Orientation of Organically Functionalized Mesoporous Silica Nanoparticles

AbstractThree orientations to choose from: 2D hexagonal organically functionalized mesoporous silica nanoparticles with tunable mesochannel orientation (straight, helical, and radial mesochannels) were synthesized through a simple addition of various amounts of ureidopropyltrimethoxylsilane (UDPTMS) in the condensation of tetraorthosilicate (TEOS) in aqueous solution.magnified image

Spherical particles from tetraorthosilicate (TEOS) sol–gel process with dimethyldiethoxysilane (DDS) and diphenyldiethoxysilane (DPDS) addition

In acid-catalyzed tetraorthosilicate(TEOS) sol–gel process, dimethyldiethoxysilane (DDS) and diphenyldiethoxysilane (DPDS) were added to obtain TDP spherical particles which, according to scanning electron microscopy (SEM) and thermogravimetric (TG) analysis, showed smooth surface and good thermal stability. The formation of the final TDP particles are discussed following three steps, which were much related with the formation of TEOS oligomer and TEOS–DDS reactive skeleton.

Sol-gel coatings on carbon steel: Electrochemical evaluation

Degradation of carbon steel has always been a concern. The use of coatings is especially recommended in aggressive atmospheres at moderate temperatures. Ceramic films can be used to improve the resistance against high temperature oxidation and corrosion of metals. Amid the different options, a sol-gel process provides a low cost, simple and non-hazardous method for processing ceramic coating with controllable composition and microstructure. This work evaluates the electrochemical behaviour of carbon steel coated by sol-gel method. Hybrid organic–inorganic silica sol-gel coatings were obtained by dip coating of planar samples in an organically modified silica sol made from hydrolysis and polycondensation of tetra-orthosilicate (TEOS) and methyltriethoxisilane (MTES) by acidic catalysis. Coatings free of defects were obtained at a sintering temperature of 400 °C. The coated samples were inspected by optical and electron microscopy and coating thickness was measured by using a Talystep surface roughness tester. Electrochemical evaluation was made by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. A comparison of the corrosion resistance of the coated metal with the uncoated one is presented. The measurements show the improvement of the corrosion resistance of the coated carbon steel.

Generation of nanodroplets and nanoparticles by ion-induced nucleation

Abstract A charged nanodroplet generator using a sonic-jet ionizer was developed, and the size distributions and currents of ions and charged nanodroplets generated were measured. The sonic-jet ionizer produced O − 2 (H 2O) n ions with a high density of 10 9−10 10 cm −3. When tetraorthosilicate (TEOS) and H2O vapors were added in the oxygen gas, the generator formed negatively charged nanodroplets with an average diameter of 1.3-1.8 and 1.3 nm, respectively. SiO 2 nanoparticles synthesized from the charged TEOS nanodroplets were non-agglomerated. The size distributions measured at various furnace temperatures indicated the formation mechanism of the nanoparticles was ion-induced nucleation. To investigate sterilization effects of negatively charged H 2O nanodroplets, yeast fungi were exposed to the gas flow from the charged nanodroplet generator. Survival rates of yeast were clearly reduced by the discharge.

Effect of calcination environment on the selective oxidation of n-butane to maleic anhydride over promoted and unpromoted VPO catalysts

A vanadium phosphate (VPO) catalyst promoted with indium and tetraorthosilicate (TEOS) was calcined in atmospheres of different oxidizing potential. The resulting catalysts afer activation showed significantly different stable activity and selectivity. The vanadium valence of the used catalyst increased with increasing oxidizing potential of calcining gases. The selectivity to maleic anhydride and specific activity increased with the vanadium valence, but the surface area decreased with the vanadium valence. Amorphous V 5+ species in the working catalyst was readily hydrated. The phase evolution during the thermal dehydration of the hydrate was similar to that of α-VOPO 4·2H 2O. The oxidation reaction did not result in surface enrichment of V 5+ relative to V 4+. The calcination atmospheres affect the catalyst morphology and the vanadium valence. An unpromoted VPO catalyst was more resistant to oxidation than the promoted catalyst in calcination, and achieved its optimized maleic anhydride yield when calcined in a more oxidizing atmosphere. The study suggests that dispersed V 5+ species in contact with (VO) 2P 2O 7 is important for the oxidation of n-butane to maleic anhydride. Calcination atmospheres need to be chosen in accordance with the oxidizability of the VPO catalyst precursors to achieve the optimized performance.