Responsive microstructures on organic–inorganic hybrid films

Micro-periodic structures exhibiting shape memory have been fabricated on organic–inorganic hybrid films. The microscale structures are obtained by forming wrinkles via buckling of the stiff surface layer. The surface-modified layers are obtained by surface photopolymerization or by oxidation of the hybrid films. The microscale structures are spontaneously formed by the shrinkage of the underlayer via gelation. The surface microstructures on titania- or silica-based films with hydrophilic swellable polymers exhibit a humidity response, i.e., a shape memory effect. This is observed when the surface microstructure disappears and is subsequently recovered with cyclic variation of the surrounding humidity. Micro-rolls are also fabricated by the selective swelling of surface-modified layers.     

Self-supported bacterial cellulose/boehmite organic–inorganic hybrid films

Self-supported organic-inorganic hybrid transparent films have been prepared from bacterial cellulose and boehmite. SEM results indicate that the BC membranes are covered by Boehmite and XRD patterns suggest structural changes on cellulose due to Boehmite addition. Thermal stability is accessed through TG curves and is dependent on Boehmite content. Transparency, as evaluated by UV?CVis absorption, increases with increasing content of boehmite suggesting application of these materials as transparent substrates for opto-electronic devices.     

Multi-component hybrid inorganic–organic–inorganic particles with various metal oxide outer shells

Non-agglomerated hybrid particles of 200 nm diameter with an outer metal oxide shell were prepared by reacting the COOH groups of poly((S)-N-dicarbazolyl-lysine)-covered silica particles with metal alkoxides, such as titanium, zirconium and aluminum alkoxides, followed by sol–gel processing. With tetraethoxysilane (Si(OEt)₄), the silica particle core was growing rather than forming an external metal oxide shell, as observed for the other tested metal alkoxides.     

Structure and surface properties of fluorinated organic–inorganic hybrid films

Fluorinated organic–inorganic hybrid films were prepared by sol–gel process from tridecafluoroctyltriethoxysilane (PFAS), 3-glycidoxypropyltrimethoxysilane, and tetraethoxysilane (TEOS). It has been found that the fluorinated hybrid films possessed fluorinated side chains originating from PFAS as top layer, and silica network as bottom layer, which had very low surface energy and could be used as water repellent functional coatings. The outermost layer of the water-repellent film may be fully covered by the perfluoroalkyl side chains as the molar ratio of PFAS/TEOS increases up to about 0.005:1. The addition of BPA can enhance the cross-link density of fluorinated hybrid films, and make more perfluoroalkyl groups enriching at the coating film-air interface to lower the surface free energy. However, the improvement of the cross-link density of fluorinated hybrid films tends to exhibit brittleness and micro-cracks. Consequently, it can be concluded that a small BPA additive content is preferred for the formation of fluorinated hybrid films with a smooth surface and less detectable cracks.     

PMMA-SiO<Subscript>2</Subscript> organic–inorganic hybrid films: determination of dielectric characteristics

Organic–inorganic hybrid thin films have been prepared by a modified sol–gel route using tetraethyl orthosilicate as the inorganic (silica) source, methyl methacrylate (MMA) as the organic source, and 3-trimetoxysilylpropyl methacrylate as the coupling agent. The films were prepared by spin coating on Si (100) p-type substrates and subsequently heat-treated at 90 °C. Fourier transform infrared results reveal a set of absorption bands associated with the formation of both PMMA and SiO₂ phases in the hybrid films. Capacitance–voltage (C–V) characterization was carried out on metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) structures, with the hybrid films as the insulator layer to evaluate the electrical properties. We present a detailed comparative analysis of the dielectric constant obtained from C–V characterization in the frequency range of 1 kHz–1 MHz. For the PMMA-SiO₂ hybrid material the dielectric constant values obtained were around 9.5 at 1 MHz which is superior to the values reported for thermally grown SiO₂ and pure PMMA materials. The interface state density for PMMA-SiO₂ on Si was approximately 10¹⁰ cm⁻², which is comparable to the standard SiO₂/Si structures. Due to the electrical behavior and low processing temperatures this hybrid dielectric is a very promising candidate for flexible electronic devices and its subsequent implementation does not require complex equipment.     

Elastic organic–inorganic hybrid aerogels and xerogels

Novel aerogels and xerogels with methylsilsesquioxane (MSQ, CH₃SiO_1.5) networks have been prepared by a modified sol–gel process using surfactant and urea as a phase-separation inhibitor and as an accelerator for the condensation reaction, respectively. Optimized aerogels dried under a supercritical condition not only showed the similar properties as conventional pure silica aerogels such as high transparency and porosity etc, but also demonstrated outstanding mechanical strength against compression; the aerogel drastically shrank upon loading and then recovered when unloaded, which is called a “spring-back” behavior. On ambient pressure drying, the wet gel also exhibited the similar response against compression stress originated from the capillary pressure, and thus xerogels with the comparative structure and properties to those of corresponding aerogels have also been obtained. This unusual mechanical behavior is attributed to the trifunctional flexible networks of MSQ, low silanol concentration which prevents the irreversible shrinkage, and high concentration of a hydrophobic methyl group directly attached to every silicon atom which helps re-expansion after the temporal shrinkage.     

Sedimentation analysis of organic–inorganic hybrid colloids

Hybrid organic–inorganic latex particles are synthesized to combine the beneficial properties of the constituents which thus lead to synergistic improvement in the properties. The properties of hybrid particles are dependent on the successful hybridization process, thus controlling or tuning of such processes by effective characterization is immensely important. Analytical ultracentrifugation provides these characterization possibilities owing to its high statistical capability and ability to characterize multiple parameters. The use of different detection methodologies can help in generating valuable information on the overall size and density distributions of the particles. Apart from that, it is also possible to quantify the presence of any free polymer and inorganic particles in the hybrid latex which would affect the properties of hybrid latexes. By following the densities of the pure and hybrid particles, it is also possible to quantify the amounts of the constituent phases in the hybrid particles. The density gradients generated in preparative ultracentrifugation also provide additional possibilities for the characterization of the hybrid particles which have densities higher than the measurable range in the analytical ultracentrifuge. Evolution of hybrid particles can also be studied as a function of time. It also provides advantage of separation of the various fractions for further characterization.     

Growth and characterization of molybdenum oxide thin films prepared by photochemical metal–organic deposition (PMOD)

Molybdenum oxide thin films have been successfully prepared by direct UV irradiation of amorphous films of a molybdenum dioxide acetylacetonate complex on Si(1 0 0) substrates. Photodeposited films were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the surface morphology examined by Atomic Force Microscopy (AFM). It was found that as-photodeposited films are uniform and smooth, with thickness of 350 nm, with rms surface roughness of 28 nm and contain non-stoichiometric oxides (MoO_3−x). The results of XRD analysis showed that post-annealing of the films in air at 450 °C transforms the sub-oxides to α-MoO₃ phase with a much rougher surface morphology (rms = 144 nm). The as-photodeposited MoO_3−x films are amorphous, and exhibit better optical quality than annealed films.     

Research progress on hybrid organic–inorganic perovskites for photo-applications

Hybrid organic–inorganic perovskite materials have attracted significant attention of most researchers in recently years, which is ascribed to the superior photoelectric properties, such as the suitable band gaps for harvesting sunlight, and exhibit high optical adsorption, high charge-carrier lifetimes and long diffusion lengths. The photodetectors, light-emitting diodes, solar cells and photocatalysts represent the remarkable applications for the hybrid organic–inorganic perovskite materials. Herein, we review the recent progress of hybrid organic–inorganic perovskite-based photodetectors, light-emitting diodes, solar cells and photocatalysts. The challenges and outlook for the hybrid organic–inorganic perovskite-based photodetectors, light-emitting diodes, solar cells and photocatalysts are considered.     

New route to 3-methacryloxypropyltrimethoxysilane-base organic–inorganic hybrid film

A series of poly(3-methacryloxypropyltrimethoxysilane)/waterborne polyurethane (PMPS/WPU) composite latexes and organic–inorganic hybrid films with PMPS contents of 0, 10, 20, 30, 40 and 50 wt.% were prepared via seeded emulsion polymerization initiated by AIBN and hydrolysis–condensation process of PMPS during the evaporation of water, respectively. WPU, that is anionic polyurethane emulsion, was synthesized using isophorone diisocyanate, polytetramethylene ether glycol, dimethylol propionic acid, 1,4-butanediol, and triethylamine. An investigation of transmission electron microscopy confirmed the core–shell morphology of the composite latex particle which was composed of a PMPS core and a polyurethane shell. A dynamic light scattering analysis showed that the average particle size distributed in the range of 42–134 nm. The proposed novel preparation method included the use of polyurethane as macromolecular emulsifier and steric stabilizer, control of (3-methacryloxypropyltrimethoxysilane) (MPS) content less than 50 wt.%, slow addition of MPS and application of AIBN ensured the preparation of a stable PMPS/WPU composite latex. Formed PMPS/WPU organic–inorganic hybrid film with high PMPS content via sol-gel process had uniform transparency at visible band because of less crystalline and phase separation between organic and inorganic phases.     

Photoregulated uptake and release of drug by an organic–inorganic hybrid sol–gel material

A photo-responsive molecularly imprinted sol–gel organic-inorganic hybrid material prepared by covalent imprinting of the template-functional monomer complex formed between 4,4′-dihydroxylazobenzene and ibuprofen was developed to explore the photo-regulated uptake and release of drug by a silicate-based smart molecularly imprinted materials. After imprinting, the template molecules (ibuprofen) were removed via hydrolysis in acid, and accurate cavities were left, which could be used as the receptor recognition sites for ibuprofen. The new organic–inorganic hybrid material shows specific affinity to ibuprofen and reversible uptake and release of ibuprofen upon alternate irradiation at 365 and 440 nm, respectively. The favorable binding strength of the imprinted receptor sites in the molecularly imprinted polymer (MIP) for ibuprofen is found to be 2.28 × 10³ M⁻¹. Density of receptor sites in the MIP material was 4.0 μmol/g—MIP.     

Synthesis and characterization of organic–inorganic hybrid materials prepared by sol–gel and containing CdS nanoparticles prepared by a colloidal method using poly(N-vinyl-2-pyrrolidone)

This paper describes the synthesis and characterization of CdS nanoparticles (NPs) stabilized with poly(N-vinyl-2-pyrrolidone) and their further immobilization on a hybrid organic–inorganic matrix produced by the sol–gel process. The production of the hybrid matrix doped with CdS NPs was carried out in two steps. In the first step a precursor, designated diureasil precursor, was synthesized from the reaction between the terminal amine groups of α,ω-diamine-poly(oxyethylene-co-oxypropylene) and the isocyanate group of 3-isocyanatopropyltriethoxysilane. The next step involved the hydrolysis and condensation reactions of ethoxy groups attached to silicon, this step resulting in the formation of a crosslinked siliceous network linked through urea bonds to a poly(oxyethylene)/poly(oxypropylene) chain. The NPs were added to the diureasil precursor before the gelation process to allow a homogeneous dispersion of the NPs within the matrix. The developed method allowed the transfer of colloidal NPs to a solid matrix without the need of exchange the capping agents or the solvent. The materials were characterized by absorption, steady-state photoluminescence spectroscopy and by TEM. The results obtained showed the presence of CdS NPs with quantum size effect dispersed within the diureasil matrix. The obtained nanocomposites show a high transparency in the visible range accounting for the good dispersion of the NPs within the matrix. The TEM analysis confirmed that the NPs are uniformly dispersed within the diureasil matrix.     

High transparent thermal curable hybrid polycarbonate films prepared by the sol–gel method

Polycarbonate/epoxy/silica hybrid films were prepared by curing an epoxy reaction via in situ sol–gel process. The influence of the synthetic conditions, such as the ratio of different epoxy reagents and the contents of [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane on the physical and optical properties of these hybrid films were investigated in details. The coefficient of thermal expansion, surface roughness, and light transmittance at a wavelength range from 250 to 800 nm were measured. These excellent overall performances make it a promising photonic packaging material.     

Effect of diphenyldiethoxysilane on the self-organized formation of nanocrystalline layered organosilicates in organic–inorganic hybrid films

Hybrid organic–inorganic films containing layered organosilicate nanocrystals have been obtained through self-organization from aqueous precursor sols containing 3-glycidoxypropyltrimethoxysilane. Diethoxydiphenylsilane has been added, in different amounts, to the precursor sol containing 3-glycidoxypropyltrimethoxysilane to prepare hybrid films with the ordered nanostructures. The effect of aging time of the precursor sol has been studied preparing different samples from sols aged up to 8 days; the formation of crystalline layered films has been observed in the samples obtained from sols of higher aging time. The hybrid films have been characterized by gracing incidence X-ray diffraction, Raman and Fourier transform infrared spectroscopy, transmission electron microscopy and UV–Vis spectroscopy. The change of the surface contact angle as a function of sol aging time and composition has been also measured. The capability of the films to be used in devices through lithographic techniques has been tested by writing the films with direct exposition to deep X-ray lithography and soft lithography with micromolds; patterns of different geometries with a thickness up to 100 μm have been obtained.     

Thermal analysis in swirling flow of titanium dioxide–aluminum oxide water hybrid nanofluid over a rotating cylinder

Journal of Thermal Analysis and Calorimetry - The purpose of this study is to examine the flow features and heat transfer in the presence of nanoparticles which are used to enhance the...     

Synthesis and properties of organic–inorganic hybrid liquid crystal gels

Organic–inorganic hybrid liquid crystal (LC) gels have been synthesised by the thiol-ene reaction of a multifunctional cyclic siloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (TVMCTS) and alkane dithiols, 1,6-hexanedithiol (HDT) or 1,9-decanedithiol (DDT), in LC matrices, 4-cyano-4?-pentylbiphenyl (5CB) or 4′-n-octyl-4-cyano-biphenyl (8CB). The LC gels were prepared in an isotropic phase at 70°C or mesophases at 25°C using radical initiators. The phase transition temperatures from a mesophase to an isotropic phase of the resulting gels were lower than those of the original LCs. The gels containing 8CB (8CB gels) prepared at 25°C showed two phase transitions: smectic-to-nematic and nematic-to-isotropic transitions. By contrast, the 8CB gels synthesised in the isotropic phase showed only one phase transition from smectic phase directly to isotropic phase. Reaction conversions in the LC gels prepared at 70°C were higher than that in the gels prepared at 25°C. Scanning microscopic light scattering analysis of the LC gels cleared homogeneous small size mesh with a small amount of large defect. Polarisation micrographs of the LC gels showed framed optical textures derived from the LC molecules at room temperature. The LC gels containing more than 90 wt% of LC showed electro-optic response.