Organically Modified Silicate Research Articles

Silica aerogel infused hierarchical glass fiber polymer composites

Hierarchical systems can address the matrix-dominated failures of structural fiber polymer composites. Here, a new synergistic hierarchical structure combines conventional structural glass fibers with a bi-continuous silica-based aerogel matrix; both pure-silica and organically-modified silicate aerogels are demonstrated. When infused with an epoxy matrix, this type of hierarchical architecture showed a marked improvement in mechanical properties: without any loss in modulus, both the compressive strength and the interlaminar shear strength increased by up to 27%, relative to the equivalent glass-fiber reinforced epoxy composite baseline. The bi-continuous network modification strategy uses industrially-relevant infusion techniques, at or near room temperature, and retains a similar final composite density (within 2%). The strategy presented here provides a versatile and readily applicable means to improve state-of-the art continuous fiber reinforced composite systems in compression and offers an opportunity to develop a new generation of composite materials.

Effect of Solvent and Catalyst Types on Stability and Properties of Zinc Phthalocyanine in the Organic–Inorganic Hybrid Materials

Hybrid materials, i.e., the organically modified silicates (ORMOSIL) based on zincphthalocyanine (ZnPc) and silica glass matrix were synthesized by the sol-gel method using protic solvents (methanol, ethanol, isopropanol, butanol) and aprotic solvent (N,N-dimethylformamide; DMF). The effect of an alkaline environment with NaOH addition (a single-stage process) and acid–alkaline environment with CH3COOH-NH4OH and HCl-NaOH (a two-stage process) was analyzed. UV-Vis spectroscopy was used to study the stability of ZnPc in the sol. The highest stability of zinc phthalocyanine in the glass was obtained for synthesis with isopropanol in the presence of the alkaline catalyst. The lowest stability of ZnPc was observed when the aprotic solvent was used. The structure and optical properties of the gels were studied by SEM, FTIR, and XRD techniques and optically stimulated luminescence (OSL) and thermoluminescence (TL), respectively. The thermal stability of the materials was analyzed by TG-DSC methods.

Curable hybrid materials for corrosion protection of steel: development and application of UV-cured 3-methacryloxypropyltrimethoxysilane-derived coating

A UV-crosslinkable two-component organically modified silicate (ORMOSIL) sol–gel coating was made using 3-methacryloxypropyltrimethoxysilane (MaPTMS) and tetraethoxysilane (TEOS) in two stages. In the first stage, key synthetic parameters, such as use of co-solvents, reaction temperature, reaction time, and catalyst, were optimized for the rapid hydrolysis and condensation of the ORMOSIL. The ORMOSIL material was made using isopropanol as the solvent and HNO3 as the acid catalyst. This resulted in a sol–gel that underwent rapid hydrolysis in 35 s. The ORMOSIL demonstrated extensive condensation after 10 min of stirring at room temperature followed by 10 min of heating at 60°C as monitored by 29Si-NMR. In the second stage, the ORMOSIL was successfully crosslinked with up to 70% consumption of the acryl functionality within 5 min under UV light exposure in the presence of photoinitiator. The UV-crosslinked coating exhibited high adhesion to low-carbon steel and impeded substrate corrosion from 17 to 25 h under an accelerated corrosive environment. Schematic representation of the hydrolysis and condensation of 3-methacryloxypropyltrimethoxysilane (MaPTMS) and tetraethoxysilane (TEOS) system and the 2D gHMBC 29Si NMR of the system.

Osteoblast response to zirconia modified-ORMOSILs.

In this study, an in vitro evaluation of the human osteoblasts response to Organically Modified Silicate (ORMOSIL) biomaterials was conducted. These materials were synthetized by sol-gel process being modified with zirconia (ZrO2) and/or Ca2+. The materials were immersed into phosphate buffer solution (PBS) in order to test precipitation of mimetic apatite-like on their surfaces. ORMOSILs were characterized by SEM, FT-IR and X-RD analysis. The response of osteoblast to ORMOSILs was analyzed as a measure of cell adhesion, proliferation and differentiation. The results showed that the addition of Ca2+ ions modifies the surface morphology of ORMOSILs by forming precipitates of mimetic apatite-like with cauliflower and scales morphologies. On the other hand, biological results suggest that the incorporation of zirconia to ORMOSILs increases their ability to support cell adhesion and proliferation. However, the inclusion of both zirconia and Ca2+ in the ORMOSILs decreases their biological compatibility by showing less cell proliferation and lower osteonectin expression, a protein related to osteoblasts. The unfavorable effect of Ca2+ on cell proliferation and cell viability could be due to its ability to induce the formation of mimetic apatite-like with incompatible morphology. The analysis of other proteins related to bone formation on ORMOSIL-Zr and ORMOSIL-Zr-Ca surfaces demonstrated clear expression of osteopontin and osteocalcin in cells growth. In the case of ORMOSIL-Zr, the expression of osteonectin occurred at early stages while the expression of osteopontin and osteocalcin begun at later stages, indicating a switch from an early to a mature stage being stimulated by the biomaterial. Together, these results highlight the important role of zirconia and Ca2+ ions in the composition of materials regulating their biocompatibility when used as scaffolds in bone regeneration.

Preparation of SiO2 nanoparticles with adjustable size for fabrication of SiO2/PMHS ORMOSIL superhydrophobic surface on cellulose-based substrates

Silica (SiO2) nanoparticles with controlled particle size and poly(methylhydrogen)siloxane (PMHS) were applied to fabricate superhydrophobic SiO2/PMHS ORMOSIL (organically modified silicate) coating on cellulose-based substrates (wood, cotton and filter paper). The influence of weight ratio of ammonia to TEOS, H2O to TEOS and ethanol to TEOS on the particle size of SiO2 nanoparticles was evaluated by the response surface methodology. The results indicated that the particle size of SiO2 nanoparticles could be well-controlled between 25 nm and 100 nm. The effect of particle size on hydrophobicity of SiO2/PMHS ORMOSIL coated wood was investigated. The modified wood had the best hydrophobicity as the particle size of SiO2 was 75 nm, possessing a water contact angle of 158.2°. After deposition of SiO2/PMHS ORMOSIL coating, the water resistance and anti-fouling property of wood increased obviously. The water absorption decreased significantly from 70.3% to 24.1%. In addition, SiO2/PMHS ORMOSIL was further applied to functionalize filter paper and cotton for oil/water separation. The separation efficiency of diesel from water was 96%–99% for modified filter paper after separation for 20 cycles, while the absorption capacity was 10.5 times of the modified cotton.

In Situ Fabrication of a Superhydrophobic ORMOSIL Coating on Wood by an Ammonia–HMDS Vapor Treatment

A superhydrophobic ORMOSIL (organically modified silicate) coating was in situ fabricated on a wood surface by ammonia–hexamethylisilazane (HMDS) vapor treatment. The wood was immerged in tetraethoxysilane (TEOS), and then the TEOS absorbed on the wood surface was hydrolyzed and condensed to hydrophobic SiO2 nanoparticles with ammonia and HDMS vapor treatment. The effect of the treatment temperature and time on the hydrophobicity of wood was investigated. At a treatment temperature of 50 °C, a superhydrophobic surface was achieved on the wood with a treatment time longer than 2 h. SEM images indicated that there were SiO2 nanoparticles fabricated on the wood surface, and FTIR revealed that the hydrophobic –Si(CH3)3 groups were incorporated on the wood surface. The ORMOSIL-modified wood possessed improved liquid repellency. The water absorption decreased significantly from 72.3% to 31.9% after modification.

Investigations on the blue luminescence enhancement of organically modified SiO2-TiO2-PDMS glass matrix

A novel class of Organically Modified Silicates (ORMOSILs) has been synthesized by non-hydrolytic sol–gel method at low temperature, incorporating the organic polymer, polydimethylsiloxane (PDMS) in tetraethylorthosilicate (TEOS) and titanium (IV) isopropoxide (TIP) based glassy gels. The structural modification of pure SiO2-TiO2 matrix by PDMS and its effects on optical and photoluminescence spectroscopy were investigated in detail. XRD pattern and HR-TEM images confirm the structural modification of the SiO2-TiO2-PDMS glass matrix. The formation of TiO2 nanocrystals of about 5–6 nm in size, embedded in the amorphous SiO2 matrix, has been confirmed from HR-TEM and SAED patterns. The TG–DTA analysis revealed the improved thermal stability of the ORMOSIL and the DSC analysis shows that its glass transition temperature decreases to 55.23 °C. A distinctive enhanced blue emission at 470 nm has been observed in photoluminescence studies of the prepared samples. FT-IR studies confirmed the formation of Ti–O–Ti, Si–O–Ti and Si–CH3 bonds by the PDMS modification of pure SiO2-TiO2 glass. These bonds and TiO2 nanocrystals embedded in the amorphous glass matrix together play an important role in the photoluminescence properties of the ORMOSIL. SiO2-TiO2 matrix has a luminescence quantum efficiency of 22.2% and the PDMS incorporation has increased the quantum efficiency to 55.8%. Thus SiO2-TiO2-PDMS ORMOSIL can be used as an efficient blue emitting host matrix for WLED fabrication.

Easy functionalization process applied to develop super‐hydrophobic and oleophobic properties on ASTM 1200 aluminum surface

Super‐hydrophobic and oleophobic surfaces on ASTM 1200 H14 aluminum alloy substrates were achieved by chemical etching followed by deposition of organically modified silicate (ORMOSIL) coatings synthesized through sol‐gel method. The chemical etching using FHH solutions (FeCl3 + HCl + H2O2) was adapted for the studied aluminum alloy by varying the concentration of iron (III) chloride and the etching time in order to increase the surface roughness of the material. This chemical etching produces rough surfaces exhibiting superficial square pores with edges about 1 to 2 μm. The chemical modifications with ORMOSIL solutions based on 1H,1H,2H,2H‐perfluorooctyltriethoxysilane (PFOTES) and hexadecyltrimethoxysilane sol‐gel precursors induced water contact angles about 154° and 150°, respectively, and sliding angles smaller than 5°, on the previously optimized etched surface. Moreover, the surface modification with ORMOSIL based on PFOTES reached also an oleophobic character with an oil contact angle about 136° due to air entrapment in the surface roughness at the oil‐aluminum interface. Finally, ORMOSIL coatings produced with varied concentrations of PFOTES and tetraethoxyorthosilane precursors proved that the super‐hydrophobic and oleophobic properties can be maintained with an important decrease of the PFOTES precursor, which should significantly decrease the cost production of such functional surfaces and could favour its mechanical durability.

Functionalization of hexagonal boron nitride nanosheets and their copolymerized solid glasses

Hexagonal boron nitride nanosheets (h-BNNSs) with unique properties, including wide band gap, excellent thermal conductivity and thermal stability, are among the most promising 2D inorganic nanomaterials in recent years. Functionalization of h-BNNSs is necessary to prevent them from strong tendency to agglomeration and to improve their dispersity and interfacial properties in solvents and polymer composites. In this work, amino and silane functionalized h-BNNSs were obtained, respectively. The chemical-bonding amino and silane functionalization of h-BNNSs were verified by FTIR, XPS and TG-MS analyses. The functionalized h-BNNSs show higher concentration, improved compatibility and dispersity in solvents and gel matrices after doping them into organically-modified silicate gel glasses using a sol-gel method. The functionalized h-BNNSs have broadband absorption and their doped glasses show high transmittances in the visible and near-infrared regions. The nonlinear optical properties of the functionalized h-BNNSs and their doped glasses were measured using Nd:YAG laser system and the doped glasses show broadband optical limiting responses at 532–1570 nm with the lowest onset threshold of 9 mJ cm−2. The optical limiting mechanisms investigated through Z-scan technique were nonlinear absorption. This work indicates that the functionalized h-BNNSs and their doped glasses are promising candidates for nonlinear optical, optical limiting and other optoelectronic materials and devices.

Biocompatible Microporous Organically Modified Silicate Material with Rapid Internal Diffusion of Protons.

A new four-component organically modified silicate (ORMOSIL) material was developed with optical pH sensors in mind. Through a sol-gel process, the porosity of an ORMOSIL framework was optimized to allow rapid diffusion of protons, ideal for fast response to pH in an optical sensor. The optically transparent material was produced by catalyzing the dual polymerization of 3-(glycidoxy)propyltrimethoxysilane (GPTMS) and propyltriethoxysilane (PrTES) with boron trifluoride diethyl etherate. The performance of the resulting material in fluorescence based optical pH sensors was evaluated by incorporation of active dye components in the inorganic polymer framework. It is demonstrated that the material has a short response time ( t90 < 30 s) and high stability in medium and during storage, and resulting sensor spots are biocompatible. It is concluded that this ORMOSIL material has excellent properties for optical pH sensors.

Characterization of sol-gel ORMOSIL antireflective coatings from phenyltriethoxysilane and tetraethoxysilane: Microstructure control and application

Chemical structure, microstructure and properties of organically modified silicate (ORMOSIL) antireflective (AR) coatings from phenyltriethoxysilane (PTES) and tetraethoxysilane (TEOS) were characterized. The reaction between PTES and TEOS was verified by means of FTIR, XPS, and 29Si NMR. N2 adsorption-desorption analysis and TEM were utilized to investigate the pore structure and microstructure control of ORMOSIL AR coatings. It was revealed that, by increasing PTES/TEOS molar ratio, the porosity of ORMOSIL AR coating decreased and then the refractive index increased gradually from 1.21 to 1.27. The hydrophobicity of ORMOSIL AR coatings was also improved significantly by increasing the water contact angle from 21.2° to 112°. Most importantly, the OIH mechanism between PTES and TEOS and hence the microstructure control of ORMOSIL AR coatings were induced in detail based on a deep discussion of results from 29Si MAS NMR, N2 adsorption-desorption analysis and TEM characterization. Finally, the feasibility of application of PTES/TEOS ORMOSIL thin films in preparation of double-layer broadband AR coatings was verified.

Exploring electrochemical reactivity toward ametryn of hybrid silicate films with phosphomolybdic acid

This paper describes the synthesis of organically-modified silicates (ormosils) with phosphomolybic acid (HPMo), and their use to detect ametryn. Gold electrodes coated with an ormosil film made of 3-cyanopropyltriethoxysilane (CPTS) and HPMo were used to detect ametryn between 3.5 and 24 µmol L−1 in an acidic medium. There was no evidence of electroreduction of ametryn when ormosils with HPMo and (3-glycidyloxypropyl)trimethoxysilane (GLPTS) or 3-aminopropyltriethoxysilane (APTS) were used. This difference in behavior is ascribed to aggregation in CPTS ormosil, while GLPTS and APTS ormosils displayed homogeneous surfaces, according to scanning electron microscopy. HPMo had its structure preserved in CPTS ormosil as indicated by 31P solid-state nuclear magnetic resonance spectra. Using polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), we inferred that the functional group dipole moments in all ormosils are oriented parallel to the interface. Control of morphology thus seems essential for applications of ormosil films, being particularly promising to monitor environmentally-relevant herbicides.

"Effect of Alumina Nanoparticles on the Photoluminescence of Rh110 Laser Dye Doped with organically modified silicate (ORMOSIL) "

"Alumina nanoparticles was synthesized using sol-gel technique and the structural characteristics of these nanoparticles were investigated using AFM where found the size of particles about (80- 100 nm), and it has been studying the effect of these nanoparticles on photoluminescence (absorption and fluorescence) of Rh110 dye laser solution also doped it with non-organic media (ORMOSIL). FTIR analysis has been recorded to the final sample to investigate the vibrational mode of both the silica and the alumina bonds."

Effect of Alumina Nanoparticles on the Photoluminescence of Rh110 Laser Dye Doped with organically modified silicate (ORMOSIL)

Effect of Alumina Nanoparticles on the Photoluminescence of Rh110 Laser Dye Doped with organically modified silicate (ORMOSIL)

Local pH monitoring of small cluster of cells using a fiber-optic dual-core micro-probe

Biological studies of tissues and cells have enabled numerous discoveries, but these studies still bear potential risks of invalidation because of cell heterogeneity. Through high-accuracy techniques, recent studies have demonstrated that discrepancies do exist between the results from low-number-cell studies and cell-population-based results. Thus the urgent need to re-evaluate key principles on limited number of cells has been provoked. In this study, a novel designed dual-core fiber-optic pH micro-probe was fabricated and demonstrated for niche environment pH sensing with high spatial resolution. An organic-modified silicate (OrMoSils) sol-gel thin layer was functionalized by entrapping a pH indicator, 2′, 7′-Bis (2-carbonylethyl)-5(6)-carboxyfluorescein (BCECF), on a ∼70μm sized probe tip. Good linear correlation between fluorescence ratio of I560nm/I640nm and intercellular pH values was obtained within a biological-relevant pH range from 6.20 to 7.92 (R2=0.9834), and with a pH resolution of 0.035±0.005pH units. The probe’s horizontal spatial resolution was demonstrated to be less than 2mm. Moreover, the probe was evaluated by measuring the localized extracellular pH changes of cultured human lung cancer cells (A549) when exposed to titanium dioxide nanoparticles (TiO2 NPs). Results showed that the probe has superior capability for fast, local, and continual monitoring of a small cluster of cells, which provides researchers a fast and accurate technique to conduct local pH measurements for cell heterogeneity-related studies.

A miniaturized oxygen sensor integrated on fiber surface based on evanescent-wave induced fluorescence quenching

In this work, a miniaturized sensor was integrated on fiber surface and developed for oxygen determination through evanescent-wave induced fluorescence quenching. The sensor was designed by using light emitting diode (LED) as light source and optical fiber as light transmission element. Tris(2,2′-bipyridyl) ruthenium ([Ru(bpy)3]2+) fluorophore was immobilized in the organically modified silicates (ORMOSILs) film and coated onto the fiber surface. When light propagated by total internal reflection (TIR) in the fiber core, evanescent wave could be produced on the fiber surface and excite [Ru(bpy)3]2+ fluorophore to produce fluorescence emission. Then oxygen could be determinated by its quenching effect on the fluorescence and its concentration could be evaluated according to Stern–Volumer model. Through integrating evanescent wave excitation and fluorescence quenching on fiber surface, the sensor was successfully miniaturized and exhibit improved performances of high sensitivity (1.4), excellent repeatability (1.2%) and fast analysis (12s) for oxygen determination. The sensor provided a newly portable method for in-situ and real-time measurement of oxygen and showed potential for practical oxygen analysis in different application fields. Furthermore, the fabrication of this sensor provides a miniaturized and portable detection platform for species monitoring by simple modular design.

Template-free sol–gel preparation of nanoporous ORMOSIL films with adjustable refractive index

A nanoporous organically modified silicate (ORMOSIL) film with adjustable refractive index from 1.21 to 1.10 was prepared at room temperature via a template-free sol–gel method, using tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) as co-precursors and hexamethylisilazane (HMDS) as surface modifier. Heating the ORMOSIL film, the refractive index of the ORMOSIL film can be further decreased to as low as 1.07. This adjustable refractive index thin film can find potential application in optical and microelectronic fields.

Preparation of hydrophobic SiO2/PMHS sol and ORMOSIL antireflective films for solar glass cover

Adjusting the porosity of films to obtain a suitable refractive index is one of the key technical concerns of the porous silica antireflective coatings (ARCs) preparation via sol–gel process. However, it is challenging to reduce the refractive index below than 1.20 with the conventional process. In the meantime, residual silanol groups (Si–OH) on coated glasses may deteriorate the weatherability of the ARCs. In this paper, a novel organically modified silicate (ORMOSL) ARCs with good hydrophobicity property and variable refractive index from 1.18 to 1.36 were prepared by modifying the silica sol with polymethylhydrosiloxane (PMHS). In the reaction with PMHS, silica micelle was cross-linked and regrew to synthesize partly clustered ORMOSIL micelle. The ORMOSIL micelles were coated on the soda-lime glasses to form monolayer ARCs. The antireflection and hydrophobicity properties of the coated glasses were significantly improved, i.e., optical transmittance up to 7% gain in the visible range with 130° water contact angle was obtained. Satisfyingly, the SiO2–PMHS sol showed excellent stability with a shelf life of up to 40–105days. In addition, the structure and morphology of the ORMOSIL films were investigated and “Cross-link and fill” model was proposed to explain the effect of PMHS content on the properties of sols and ARCs.

Structure–property relationship of new polyimide–organically modified silicate–phosphotungstic acid hybrid material system

A new hybrid material system was successfully developed from the combination of polyimide (PI), organically modified silicate (ORMOSIL), and phosphotungstic acid (HPW) from polycondensation reactions and sol–gel process. The materials were obtained in the form of flexible and free-standing films, with the formation of PI and ORMOSIL network confirmed by Fourier transform infrared. Solid-state phosphorus-31 nuclear magnetic resonance evaluated the HPW structure and confirmed its presence and also structural integrity in the materials after synthesis procedure. Thermogravimetric analysis revealed that the materials were thermally stable up to 773 K, and scanning electron microscopy images and X-ray micro-fluorescence mapping showed very good compatibility between the organic and inorganic phases with ORMOSIL improving the HPW dispersion. Furthermore, both ORMOSIL and HPW enhanced the permittivity of the materials from 2.5 to 4.3, compared to the neat PI, appointing them as potential candidates for electric and electronic applications.

Photo-Physical Properties of Stilbine-3 (STB-3) Laser Dyes Embedded in Sol-Gel Glasses

Solid-state tunable dye laser materials developed by incorporation of stable laser dye molecules into solid host matrices like polymers, organically modified silicates (ORMOSILS) and porous sol-gel glasses. These materials have technical advantages such as compactness, better manageability and suitability for field measurement. The recent research work with highly porous sol-gel glasses having good transparency in UV-Near UV region used as solid host for solid-state dye laser materials has attracted a great deal of attention because of its high potential utility than polymers. Two different procedure’s are used for incorpoerating the Stilbine-3 (STB-3) laser dyes into porous sol-gel matrices such as dope or dip methods. In dope method dye is mixed at the sol state and drying is carried out afterward; while in dip method matrix is first prepared and the matrix is dipped in desired dye solution. After preparation of these dye embedded sol-gel glasses we studied their spectroscopic properties of using absorption and fluorescence spectroscopy. Along with spectroscopy properties, the studies for longevity or the shelf life and lasing action of these materials were carried out. Laser dye STB-3 incorporated in sol-gel glass samples shows the same result as in methanolic solution.