SiO2 Hybrid Materials Research Articles

Review: Synthesis of Chemical Materials for Fingerprint Detection

Fingerprint is a famous tool for identifying the identity of people by using the ten fingers, which should be left traced for remaining materials, and that could be achieved by specific chemical compounds made as developer reagents. In this review, we mention some chemical compounds that are used for developing fingerprints and that include inorganic and organic materials in classic and Nano size. The reported materials in this work include pristine samples such as SiO2 and carbon dote or hybrid materials with specific materials to produce new compounds with new physio-chemical properties able to interact with trace fingerprints.

A Study of Thermal Stability and Degradation Kinetics of Microcrystalline Cellulose (MCC)/Sol-Gel Silica (SiO<sub>2</sub>) Hybrid Materials

Microcrystalline cellulose (MCC) has been widely used in the production of composite materials because it is inexpensive, easy to process, good mechanical properties and environmentally friendly. Despite its advantages, MCC has disadvantages such as poor thermal stability, hygroscopic and poor compatibility with hydrophobic materials. Understanding the thermal behavior of MCC is important because thermal degradation occurs at different rates and directly affects the final product. In this study, the MCC/ SiO2 hybrid materials were prepared using in-situ sol-gel synthesis, followed by the investigation of their thermal stability and degradation kinetics using thermogravimetric analysis (TGA). Degradation kinetics were analysed using two model-free analysis (i.e. Flynn-Wall-Ozawa, FWO and modified Coats-Redfern, CRm) to evaluate the degradation behaviour (conversion degree (α) of 0.1 to 0.8) and activation energies (Ea) of MCC, MCC/ sol-gel silica (MCC/SiO2) and modified MCC (mMCC/SiO2) at heating rates (β) of 10, 20, 30 and 40 °C/min. Thermal stability results showed that the presence of silica on MCC had no influence on the degradation temperature of the hybrid material however, it slightly shifted the Tonset to higher values. The presence of silica also increased the final residue of the hybrid, especially in mMCC/SiO2 samples. DTG curves clearly show that all samples exhibited one step degradation process. The kinetics study assumed that all samples has single reaction mechanism as the fitted line was parallel in almost all conversion degrees (α) in both FWO and CRm methods. Ea calculated for MCC, MCC/SiO2 and mMCC/SiO2 are in good fit with both FWO and CRm model where the R2 observed more than 0.97. Ea was increased in both methods, MCC/SiO2 and mMCC/SiO2 as compared to MCC, which implied that the addition of sol-gel silica to MCC could promote a stepwise degradation.

Electrochemical Glyphosate Sensor Based on Hybrid Material SiO2/Sm2O3/Carbon Modified with Meldola Blue

AbstractIn this work, we have proposed an electrochemical sensor for the detection of pesticides by using a ceramic composite with a SiO2 surface modified with Sm2O3 nanoparticles and C‐graphite (SSMG), obtained by the sol‐gel process and immobilized by adsorption in Meldola Blue cationic dye (MB). The composite was called (SSMG/MB), which was characterized by spectroscopic, electrochemical techniques, Fourier‐transform infrared spectroscopy, and Cyclic Voltammetry. The proposed sensor was applied for the glyphosate electrochemical detection, using Differential Pulse Voltammetry, and, under optimized parameters has presented the linear response for the pesticide in the concentration range from 0.99 to 7.94 (μmol L−1; R2=0.9963; n=8). The calculated values for the detection limit and the quantification limit were 0.15 and 0.49 μmol L−1, respectively. Therefore, the new electrochemical sensor based on SiO2, NPsSm2O3, C‐graphite, and MB hybrid material was developed for the first time for glyphosate determination, which has demonstrated high potential for the development of new hybrid devices for environmental control.

Antimicrobial property and photocatalytic antibacterial mechanism of the TiO2-doped SiO2 hybrid materials under ultraviolet-light irradiation and visible-light irradiation

Abstract In this study, an antibacterial hybrid material of TiO2-doped SiO2 (TiO2@SiO2) was prepared by hydrolysis, where the SiO2 carrier was synthesized by a sol–gel method. The as-prepared antibacterial materials were characterized by scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller measurements and particle size analysis. The antibacterial effect of the prepared hybrid materials on Escherichia coli (E. coli) was investigated by the plate coating method. The presence of the Ti–O–Si bond between anatase-TiO2 and SiO2 was confirmed by the above characterization methods, which was beneficial to enhance the photocatalytic inactivation effect of E. coli under ultraviolet-light (UVA) irradiation and visible-light irradiation. With the increase in the TiO2 content from 1.5% to 4.4%, antibacterial activities were clearly enhanced under different types of light irradiation. For the optimum sample of 4.4%-TiO2@SiO2, antibacterial rates of 99.3% and 90.5% under UVA irradiation and visible-light irradiation were obtained, respectively. The antibacterial mechanism was demonstrated by fluorescence detection of the reactive oxygen species (ROS) and SEM images of the changes in the bacterial morphology. Results revealed that the hybrid materials can generate ROS under not only UVA irradiation but also visible-light irradiation. A majority of the ROS migrated into the bacterial cells and caused the oxidative damage of cells. This is a crucial study for the photocatalytic inactivation mechanism of the bacteria under both UVA and visible-light irradiation.

Boosting the Catalytic Performance of Metal-Organic Frameworks for Steroid Transformations by Confinement within a Mesoporous Scaffold.

Solid-state crystallization achieves selective confinement of metal-organic framework (MOF) nanocrystals within mesoporous materials, thereby rendering active sites more accessible compared to the bulk-MOF and enhancing the chemical and mechanical stability of MOF nanocrystals. (Zr)UiO-66(NH2 )/SiO2 hybrid materials were tested as efficient and reusable heterogeneous catalysts for the synthesis of steroid derivatives, outperforming the bulk (Zr)UiO-66(NH2 ) MOF. A clear correlation between the catalytic activity of the dispersed Zr sites present in the confined MOF, and the loading of the mesoporous SiO2 , is demonstrated for steroid transformations.

Boosting the Catalytic Performance of Metal–Organic Frameworks for Steroid Transformations by Confinement within a Mesoporous Scaffold

AbstractSolid‐state crystallization achieves selective confinement of metal–organic framework (MOF) nanocrystals within mesoporous materials, thereby rendering active sites more accessible compared to the bulk‐MOF and enhancing the chemical and mechanical stability of MOF nanocrystals. (Zr)UiO‐66(NH2)/SiO2 hybrid materials were tested as efficient and reusable heterogeneous catalysts for the synthesis of steroid derivatives, outperforming the bulk (Zr)UiO‐66(NH2) MOF. A clear correlation between the catalytic activity of the dispersed Zr sites present in the confined MOF, and the loading of the mesoporous SiO2, is demonstrated for steroid transformations.

Preparation and performance study on P(St‐MMA)‐SiO2 doped P(VDF‐HFP) based composite polymer electrolyte

AbstractThe organic–inorganic hybrid material poly(styrene‐methyl methacrylate)‐silica (P(St‐MMA)‐SiO2) was successfully prepared by in situ polymerization confirmed by Fourier transform infrared spectroscopy and was employed to fabricate poly(vinylidene fluoride‐hexafluoropropylene) (P(VDF‐HFP)) based composite polymer electrolyte (CPE) membrane. Desirable CPEs can be obtained by immersing the CPE membranes into 1.0 mol L−1 LiPF6‐EC/DMC/EMC (LiPF6 ethylene carbonate + dimethyl carbonate + ethylmethyl carbonate) liquid electrolyte for about 0.5 h for activation. The corresponding physicochemical properties were characterized by SEM, XRD, electrochemical impedance spectroscopy and charge–discharge cycle testing measurements. The results indicate that the as‐prepared CPEs have excellent properties when the mass ratio of the hybrid P(St‐MMA)‐SiO2 particles to polymer matrix P(VDF‐HFP) reaches 1:10, at which point the SEM analyses show that the as‐prepared P(St‐MMA)‐SiO2 particles are uniformly dispersed in the membrane and the CPE membrane presents a homogeneous surface with abundant interconnected micropores. The XRD results show that there may exist interaction forces between the P(St‐MMA)‐SiO2 particles and the polymer matrix, which can obviously decrease the crystallinity of the composite membrane. Moreover, the ionic conductivity at room temperature and the electrochemical working window of the CPE membrane can reach 3.146 mS cm−1 and 4.7 V, respectively. The assembled LiCoO2/CPE/Li coin cell with the CPE presents excellent charge–discharge and C‐rate performance, which indicates that P(St‐MMA)‐SiO2 hybrid material is a promising additive for the P(VDF‐HFP) based CPE of the lithium ion battery. © 2016 Society of Chemical Industry

A versatile and efficient approach to separate both surfactant-stabilized water-in-oil and oil-in-water emulsions

Oil/water separation is an important field aiming to resolve industrial oily wastewater and oil-spill pollution, as well as environmental protection. However, the separation of oil-water mixtures, especially surfactant-stabilized oil-water emulsions, is a worldwide challenge. To this end, we developed a versatile and efficient approach to separate various highly stable emulsions including both surfactant-stabilized W/O emulsions and O/W emulsions with high separation efficiency using nanoporous divinylbenzene (DVB)/SiO2 hybrid material. The highly effective separation property of the hybrid material is attributed to its superhydrophobicity, high specific surface area and nanopore size distribution. Therefore, the versatile emulsion separation of hybrid material shows obvious advantage over most superwetting surfaces that only have effect on free oil-water mixtures or one form emulsion (W/O emulsions or O/W emulsions). Besides, the as-prepared hybrid material can rapidly swell various organic solvents from water selectively with high absorption capacity because of the present multi-level nanopores which can enhance adsorption performance for their improved accessibility and high surface area. Moreover, the hierarchical nanoporous structure of hybrid material still remained even after repeated separation procedures indicating the outstanding fouling resistance and good reusability. (C) 2016 Elsevier B.V. All rights reserved.

Preparation, Characterization, and Properties of Novel Polyimide–SiO2 Hybrid Composites Based on Bipyridine for Low Dielectric Applications

Novel low dielectric polyimide–SiO2 hybrid materials containing bipyridine were prepared with three-step sol–gel process from poly(amic acid)s. (3-Aminopropyl)triethoxysilane as coupling agent was used to increase the intrachain chemical bonding between the polyimide and SiO2 groups. The thermal, dielectric, and physical properties of the hybrid materials were investigated and correlated with the porous structure. The glass transition temperatures of all the hybrids were found to be higher than polyimides. The effect of SiO2 groups on the porous structure and dielectric properties was investigated. The dielectric constant of the hybrid materials was observed a decrease from 3.30 to 2.15 with increased SiO2 amount.

Preparation of modified epoxy–SiO2 hybrid materials and their application in the stone protection

• Preparation of epoxy–SiO 2 –PDMS-OH polymer. • Structural properties of epoxy–SiO 2 –PDMS-OH polymer were characterized. • Protective ability of epoxy–SiO 2 –PDMS-OH agents for limestone was evaluated. Epoxy–SiO 2 polymers modified by poly(dimethylsiloxane) hydroxyl terminated (PDMS-OH) were presented in this paper in order to evaluate their potential use as protective agents for stone surface. No volatile organic components were employed in this synthesis route which was environmentally friendly. FTIR, TG-DSC, SEM and AFM techniques were used to investigate the effect of adding PDMS-OH to (3-glycidyloxypropyl)-methyldiethoxysilane (GPTMS) and (3-aminopropyl)triethoxysilane (ATS), which leaded to epoxy–SiO 2 –PDMS-OH materials. The addition of PDMS-OH into GPTMS and ATS accelerated the curing process and increased the viscosity of sol. It was found that PDMS-OH was chemically incorporated into the polymer matrix via Si O Si bonds by FTIR analysis. Furthermore, an appreciable reduction of microcracks was obtained for epoxy–SiO 2 –PDMS-OH polymers when adding 30% w/w of PDMS-OH. The effectiveness of the epoxy–SiO 2 –PDMS-OH polymers synthesized as stone protective agents was evaluated.

Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

A new kind of asymmetric organic–inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m−2 h−1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology.

Synthesis, characterization and antibacterial assessment of SiO2-hydroxypropylmethyl cellulose hybrid materials with embedded silver nanoparticles

Antibacterial SiO2 hybrid materials based on tetraethyl orthosilicate (TEOS), hydroxypropylmethylcellulose (HPMC) and silver were prepared by the sol-gel method. The content of cellulose derivate was 5 wt% and the silver concentration varied from 0.5 wt% to 2.5 wt%. The amorphous nature, morphology and antibacterial behaviour were studied. Fourier transform infrared (FTIR) spectra of the hybrids showed characteristic peaks for SiO2 network. Scanning electron microscope (SEM) analysis confirmed the formation of spherically shaped silver nanoparticles with a size of 30 nm on the matrix surfaces. Bacillus subtilis and Escherichia coli K12 were used as model microorganisms. The hybrid materials demonstrated bacteriostatic and bactericidal effect on the tested bacteria. Highest sensitivity to the obtained hybrids was observed in B. subtilis with significant lag-phase delay and biggest inhibition zone sizes.

A facile way to fabricate a superamphiphobic surface

Compared to superhydrophobic surfaces, superamphiphobic surfaces possess more potential applications but are difficult to fabricate. Herein, to address this problem, we describe a simple method to fabricate a superamphiphobic surface based on a CNTs–SiO2 hybrid material. The CNTs–SiO2 hybrid material obtained by a sol–gel approach was sprayed onto glass slides to form coatings. After surface fluorination, the sprayed coating displayed superamphiphobicity toward water and a number of organic liquids, such as dodecane. It was found that the time of fluorination slightly influenced the surface wettability of the sprayed coating. We also investigated the role of CNTs and SiO2 on superamphiphobicity establishment separately, and such information allowed us to engineer surfaces with specific wettability.

One-step synthesis of graphene nanoplatelets/SiO2 hybrid materials with excellent toughening performance

Graphene nanoplatelets (GNPs)/SiO2 hybrid materials had been prepared successfully via chemical grafting in one step. Herein, SiO2 particles and GNPs were connected by poly acryloyl chloride (PACl). The results from Fourier transform infrared spectroscopy showed that functionalized GNPs and SiO2 particles had been successfully bridged with chemical bonds like OCO and SiOC. And the nanostructure of hybrid materials was characterized by scanning electron microscopy and transmission electron microscopy. All the images indicated that SiO2 particles were grafted on the surface of GNPs successfully. Moreover, the result of Raman spectroscopy showed that carbon atoms of GNPs became much more disorder, due to destroying the carbon domains during the process of chemical drafting. Meaningfully, the results from tensile tests indicated that Graphene/SiO2 hybrid materials had better toughening effect on epoxy composites than graphene oxide and SiO2 particles. POLYM. COMPOS., 36:907–912, 2015. © 2014 Society of Plastics Engineers

SiO2 reinforced HDPE hybrid materials obtained by the sol–gel method

ABSTRACTNovel high density polyethylene (HDPE)/SiO2 hybrid materials were prepared by the sol–gel process using tetraethoxysilane (TEOS). HDPE and synthesized HDPE‐g‐vinyl trimethoxysilane (VTMS) through melt grafting method was used as the raw material. The structure and thermal, mechanical properties of hybrid materials were investigated by Fourier transform infrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), simultaneous thermogravimetric (TG), differential thermal analysis (DTA), and tensile tests, respectively. Silica phase in the HDPE‐g‐VTMS hybrids showed a network structure and nano‐scale size. The covalent bonds between organic and inorganic phases were introduced by the HDPE‐g‐VTMS bearing trimethoxysilyl groups, which underwent hydrolytic polycondensation with TEOS. The thermal stability and mechanical properties of HDPE‐g‐VTMS hybrids were obviously improved by embedded silica networks. It was found that the silica content in the HDPE‐g‐VTMS hybrid material was linearly increased with the TEOS dosage. The formation of the HDPE‐g‐VTMS hybrid was beneficial for enhanced mechanical strength and thermal stability, in comparison with the neat HDPE. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39891.

Tin Oxide Nanoparticles and SnO2 /SiO2 Hybrid Materials by Twin Polymerization Using Tin(IV) Alkoxides.

Twin polymerization was used to prepare composite materials composed of SnO2 nanoparticles entrapped in a polymer matrix. Novel, well-defined tin-containing molecular precursors, so-called twin monomers, were synthesized by transesterification starting from Sn(OR)4 (R=tBu, tAm) to give Sn(OCH2 C4 H3 O)4 (1), [Sn(OCH2 C4 H3 S)4 ⋅HOCH2 C4 H3 S]2 (2), [Sn(OCH2 -2-OCH3 C6 H4 )4 ⋅HOCH2 -2-OCH3 C6 H4 ]2 (3), [Sn(OCH2 -2,4-(OCH3 )2 C6 H3 )4 ⋅HOCH2 -2,4-(OCH3 )2 C6 H3 ]2 (4), 2,2'-spirobi[4H-1,3,2-benzodioxastannine] (5), 2,2'-spirobi[6-methylbenzo(4H-1,3,2)-dioxastannine] (6), and 2,2'-spirobi[6-methoxybenzo(4H-1,3,2)dioxastannine] (7). 13 C and 119 Sn NMR spectroscopy in the solid state and in solution as well as IR spectroscopy and elemental analysis were used to characterize the tin alkoxides. The molecular structures of compounds 2 and 3 were determined by single-crystal X-ray diffraction analysis. The moisture sensitivity of the tin(IV) alkoxides was demonstrated by the formation of the tin oxocluster [Sn3 (μ3 -O)(μ2 -OH)(μ2 -OCH2 C4 H3 S)3 (OCH2 C4 H3 S)6 (HOCH2 C4 H3 S)]2 (2 a), a hydrolysis product of compound 2. Polymerization reactions in the melt (for 1 and 5) and in solution (for 2-4) resulted in cross-linked nanocomposites of the type polymer/SnO2 . Subsequent oxidation of the composites gave SnO2 with BET surface areas up to 178 m2 g-1 . Simultaneous twin polymerization of compounds 5-7 with the silicon derivative 2,2'-spirobi[4H-1,3,2-benzodioxasiline] resulted in the formation of polymer/SnO2 /SiO2 hybrid materials. Oxidation gave porous materials with SnO2 nanoparticles embedded in a silica network with BET surface areas up to 378 m2 g-1 . The silica acts as a crystal growth inhibitor, which prevents sintering of the SnO2 nanoparticles 20-32 nm in size.

Influence of the variation of carbon nanotubes on the morphology of carbon nanotubes–SiO2hybrid materials

Three different carbon nanotube (CNT)-SiO2 hybrid materials were prepared by a simple sol-gel process using benzyl alcohol as a surfactant, and the variation of morphology of the CNT-SiO2 hybrid materials was investigated. The results showed that the morphology was influenced by the diameter of the different CNTs, and the quality of silica coatings on the CNT surfaces became better when the diameter of CNTs used was larger. We think the detailed understanding of the variation of morphology of CNT-SiO2 hybrid materials should be crucial in order to synthesise ideal CNT-SiO2 hybrid materials for the potential applications in many fields.

Synthesis and Characterization of SAR/SiO<sub>2</sub> Hybrid Materials with High Thermal Stability

A silicon-containing arylacetylene resin, poly[(dimethylsilyl)eneethynylene phenyleneethynylene] with methoxy silyl terminal group (abbreviated MSAR) was synthesized. The resin and tetraethoxysilane (abbreviated TEOS) were used to prepare silicon-containing arylacetylene resin (abbreviated SAR) /SiO2 hybrid materials by a sol-gel method. Both the curing process of the xerogel and thermal properties of the hybrid materials were studied by FT-IR, DSC and TGA. The thermogravimetric analysis of the hybrid materials showed that Td5 (temperature of 5% weight loss) was 696°C and char yield was 92.1% at 800°C in nitrogen. A Si-C-O ceramic residue was obtained in high yield(86.8%) by sintering up to 1450°C in nitrogen.

Synthesis and Characterization of Titanium Dioxide Phases in Mesostructured Silica Matrices with Photocatalytic Activity

AbstractAn imidazole type ionic liquid (IL), 1‐hexadecyl‐3‐methylimidazolium chloride (I16IL) was used as a template in the preparation of mesoporous silica with incorporated titanium dioxide. In this process, the IL is the structural template as well as the source of the Ti. The steps leading to the formation of the nanocrystalline metal oxide include: a) formation of metal‐containing IL (M‐IL); b) using the M‐IL as a template for the mesoporous silica; c) calcination of the sample to remove the organic moiety, while leaving the metal centers to form oxides on the porous framework. By varying the TiO2–SiO2 calcination temperature, the particle size and phase of TiO2 have been studied. These TiO2–SiO2 hybrid materials were characterized by using various physicochemical techniques, such as UV/Vis diffuse‐reflectance spectroscopy, Raman spectroscopy, X‐ray diffraction, N2 adsorption‐desorption isotherm measurement, Fourier transform infrared spectroscopy, and transmission electron microscopy. The resultant hybrid silica demonstrated effective photocatalytic activity for the oxidation of cyclohexene and styrene.

Design of mesoporous SO42−/ZrO2–SiO2(Et) hybrid material as an efficient and reusable heterogeneous acid catalyst for biodiesel production

Mesoporous sulfated zirconia material functionalized by ethane-bridged organosilica moieties was prepared in a single step. Compared with alkyl-free sulfated zirconia materials, the as-prepared hybrid catalyst showed much higher catalytic activity towards biodiesel production from pure triglyceride as well as low-cost virgin plant oil.