Nanohybrid Thin Films Research Articles

Synthesis and morphology of new functional polyimide/titania nano hybrid materials

The synthesis and full characterization of 3,5-diamino-N-(1-oxo-3-phenyl-1-(phenylamino)propan-2-yl)benzamide (5), as a new diamine monomer containing l-phenylalanine fractions in the structure of pendant group is presented. The stated diamine is employed as a key monomer for the in situ sol–gel fabrication of polyimide/titania nano hybrid thin films containing different titania contents. It is shown that titania particles are created in the size range of 20–80 nm, well-dispersed and enjoy the favorable spherical shapes supposing the constructive organic–inorganic interactions. The superior thermal stabilities of resulted nanocomposite films are confirmed using thermal analysis techniques. Moreover, the UV–Vis spectroscopy has shown the growing up in blocking efficiency along with the increase in titania contents. Predictably, the produced titania nanoparticles have amorphous structures.

High performance n-type organic–inorganic nanohybrid semiconductors for flexible electronic devices

We report a high-performance and air-stable flexible and invisible semiconductor which can be substitute for the n-type organic semiconductors. N-type organic–inorganic nanohybrid superlattices were developed for active semiconducting channel layers of thin film transistors at low temperature of 150 °C by using molecular layer deposition with atomic layer deposition. In these nanohybrid superlattices, self-assembled organic layers (SAOLs) offer structural flexibility, whereas ZnO inorganic layers provide the potential for semiconducting properties, and thermal and mechanical stability. The prepared SAOLs–ZnO nanohybrid thin films exhibited good thermal and mechanical stability, good flexibility, transparent in the visible range, and excellent field effect mobility (>7cm 2/V s) under low voltage operation (from −1 to 3 V). The nanohybrid semiconductor is also compatible with pentacene in p–n junction diodes.

Optical properties of poly(methyl methacrylate)–titania nanostructure thin films containing ellipsoid-shaped titania nanoparticles from ex-situ sol-gel method at low growth temperature

This paper reports on the linear and nonlinear optical responses of the PMMA-TiO2 nanohybrid thin films which are synthesized by a flexible ex-situ sol-gel/polymerization process, assisted by spin coating and multi-step baking. Triethanolamine (TEOA) as surfactant and shape controller is used to modify the interface between PMMA and TiO2, allowing a highly homogeneous dispersion of the ellipsoid-shaped TiO2 nanoparticles. The resulting nanohybrid thin films have highly optical transparency as proved by the linear absorption photon-energy spectra and indicate an enhanced nonlinear optical (NLO) response as confirmed by the Z-scan technique using 800-nm, 120-femtosecond (fs) laser pulses, highlighting the potential of the nanocomposites for efficient optical devices.

Ordered luminescent nanohybrid thin films of Eu(BA) 3Phen nanoparticle in polystyrene matrix from diblock copolymer self-assembly

A simple route for fabricating highly ordered luminescent thin films based on hybrid material of diblock copolymer and europium complex, assisted with self-organization of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer upon solvent annealing, is presented. PS-b-PEO self-organized into hexagonal patterns and europium complex of Eu(BA) 3Phen was selectively embedded in PS blocks after solvent annealing in benzene or benzene/water vapor. During benzene annealing, the orientation of the PEO cylindrical domains strongly depended on the Eu(BA) 3Phen concentration. In contrast, when the hybrid thin films were annealed in mixture of benzene and water vapor, high degree of orientation of the PEO cylindrical domains is more easily obtained, which is independent of Eu(BA) 3Phen concentration. Furthermore, preferential interaction of PEO domains with water induces a generation of nanopores in the hybrid thin film. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the long-range lateral order and phase composition of the hybrid thin films. The ordered nanohybrid thin films kept the fluorescence property of Eu(BA) 3Phen and showed a strong red emission under the 254 nm light's irradiation. The fluorescence property was confirmed by photoluminescence (PL) spectra.

Preparation and the optical nonlinearity of surface chemistry improved titania nanoparticles in poly(methyl methacrylate)–titania hybrid thin films

With 800-nm, 120-fs laser pulses, optical nonlinearity has been studied in a series of thin films containing poly(methyl methacrylate) (PMMA), filled with surfactant acetylacetone (Acac) capped TiO 2 nanoparticles, which were synthesized by a simple in situ sol–gel/polymerization process, assisted by spin coating and multi-step baking. The resulting nanohybrid thin films have highly optical transparency and demonstrate a unique nonlinear optical (NLO) response. The highest nonlinear refractive index ( n 2) is observed up to 6.55 × 10 −2 cm 2 GW −1 in the nanohybrid thin film of 60 wt% Ti(OBu) 4 in PMMA, with a negligible two-photon absorption (TPA), as confirmed by the Z-scan technique. The titanium precursor loading combined with the nature of the capping molecules are used to influence the ability of nanoparticles to nonlinear optical response. Indeed, the ligands at the nanoparticles’ surface can not only control the extent of the interaction between the organic molecules and the embedded nanoparticles but also influence the optical nonlinearities of nanoparticles.

Optical properties of polysiloxane hybrid thin films containing nano-sized Ag–As–Se chalcogenide clusters

Chalcogenide glasses are attractive for all-optical signal processing due to their outstanding optical properties, including large optical nonlinearity, a high refractive index and high photosensitivity. In device fabrication, a challenge lies in the difficulty of obtaining thin films with a high stability and good uniformity. In this paper, optical thin films containing nano-sized chalcogenide clusters in polysiloxane matrices are fabricated by a modified plasma deposition process. The optical absorption and luminescence emission properties of the hybrid thin films were characterized by UV-Vis-NIR and fluorescence spectroscopy. Luminescent emission from Ag–As–Se nano-sized clusters was observed for the first time in these nano-hybrid thin films, and the mechanism was discussed.

Microstructure and properties of polyamideimide/silica hybrids compatibilized with 3-aminopropyltriethoxysilane

In this work, we prepared and characterized polyamideimide (PAI)/silica hybrids compatibilized with 3-aminopropyltriethoxysilane (APTES). PAI/silica nanohybrid thin films were prepared using an in situ sol–gel process, followed by thermal imidization. We have investigated the microstructures and properties of the PAI/silica hybrids using FT-IR spectroscopy, X-ray diffraction, small-angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC). We also measured their tensile properties, thermal properties, refractive indices, and dielectric constants. In general, the properties of the PAI/silica hybrids were optimized when the silica content was 6 wt.%.

Preparation and Characterization of Polyimide/Fluorinated Silicate Nano-hybrid Thin Films with Low Refractive Indices

-octylsilane (13FTES) andtetraethoxysilane (TEOS) were employed to prepare the silicate precursors. Furthermore,2-aminopropyl triethoxysilane (APrTEOS) was used as a coupling agent to improve thecompatibility between the polymeric and inorganic domains of the nano-hybrid materials.The chemical structures of organo-silicate and hybrid materials were examined with solidstate

Preparation of layered organic–inorganic nanohybrid thin films of molybdenum trioxide with polyaniline derivatives for aldehyde gases sensors of several tens ppb level

Abstract The present study is an investigation of the aldehyde gas sensing property of MoO 3 with polyaniline (PANI) or poly( o -anisidine) (PoANIS) thin films, which are one of the layered organic–inorganic hybrids. The (PANI) x MoO 3 and (PoANIS) x MoO 3 hybrid thin films are formed by a modified intercalation process. A sodium molybdenum oxide ([Na(H 2 O) 2 ] x MoO 3 ) thin film is soaked in an intercalation solution, i.e . PANI or PoANIS solution, which is synthesized by polymerization of aniline or o -anisidine hydrochloride in a water solution. In this modified process, the intercalation solutions are filtrated in order to remove insoluble polymers possessing a high-polymerization degree. The (PANI) x MoO 3 and (PoANIS) x MoO 3 hybrid thin films prepared by the modified process can exhibit excellent response of a resistance increase when exposed to formaldehyde and acetaldehyde of several tens ppb because insoluble PANI or PoANIS impurities possessing opposite response of resistance decreases against the hybrids are prevented adsorbing onto the surfaces of the hybrid thin films.

Diblock Copolymer Templated Nanohybrid Thin Films of Highly Ordered TiO2 Nanoparticle Arrays in PMMA Matrix

Solvent modification with a mixture of tetrahydrofuran and water in a proportional volume ratio of 50% has been employed to enable poly(methylmethacrylate)-b-polyethylene oxide diblock copolymer to be used as a template for preparing nanohybrid thin films containing highly ordered arrays of titanium dioxide (TiO2) nanoparticles. With control of the processing parameters involved in the block copolymer templating, nanoarrays consisting of nanocrystalline TiO2 particles were successfully assembled in the hexagonal-like or cubical-like hierarchical structures, as revealed by TEM studies. The phases and chemical nature of the titania nanoparticles have been confirmed by Raman and XPS spectroscopies. A significant enhancement in nanocrystallinity of the TiO2 phase in the nanohybrid thin films was achieved by the application of an appropriate hydrothermal treatment in high-pressure water vapor at 150 °C. The nanocrystallinity strongly affects the UV absorbance and photoluminescence emission of the nanohybrid thin films.

Titania-PMMA nanohybrids of enhanced nanocrystallinity

Nanohybrid thin films consisting of titania nanoparticles embedded in a suitable polymer matrix represent a new class of functional materials for optoelectronic applications. For instance, our previous studies show that titania-poly(methylmethacrylate) or TiO2-PMMA nanohybrids derived from in situ sol-gel technique are promising as nonlinear optical materials since they can demonstrate a very fast recovery time of ∼1.5 picosecond and a large third-order nonlinear susceptibility, χ(3) up to 1.93 × 10−9 esu, as observed by pump-probe and Z-scan techniques. However, it was realized that the conventional in situ sol-gel technique employed led to a largely amorphous TiO2 phase in the PMMA matrix. In order to overcome this limitation, we have performed two modification approaches making use of high pressure water vapor, i.e.: pre-and post-hydrothermal treatments applied on the sol-gel precursors. The degree of TiO2 crystallinity in the resulting nanohybrids was studied by XRD, FTIR, and TEM. Both approaches can enhance the nanocrystallinity TiO2 phase considerably and at the same time preserve the integrity of polymer matrix. It was found, however, that while the nanohybrid thin films derived from the pre-hydrothermal treatment show a high absorption in the visible length, those derived from the post-hydrothermal treatment are highly transparent. Nonlinear optical measurement using the Z-scan technique on the latter sample shows a significant enhancement in χ(3) as high as 5.27 × 10−9 esu.

Pulsed Laser Deposition and Fabrication of CoO/ZnO and CoO/TiO<sub>2</sub> Nano-Hybrid Thin Film

Nano-hybrid CoO/ZnO and CoO/TiO2 thin films are interesting magnetic semiconductors, which may be the potential candidates in spintronic devices. We report a study of the morphology and properties of highly crystalline and textured CoO/ZnO and CoO/TiO2 nanohybrid thin films grown on Al2O3 (006) substrates by pulse laser deposition (PLD). The structural and magnetic properties of the deposited films were analyzed by AFM, SEM, XRD and AGM. Highly crystalline CoO/ZnO and CoO/TiO2 films were formed on single crystal Al2O3 substrates at 1x10-4 Torr oxygen partial pressure. It has been found that with a fine tune of the deposition conditions and heat treatment, the films can have highly crystalline ZnO zincite hexagonal and TiO2 rutile structure. The XRD rocking curves showed that the thin films grown are highly textured with FWHM of 0.251o for ZnO zincite and 0.065o for TiO2 rutile respectively. Both zincite and rutile exhibited properties of ferromagnetics above room temperature. The AGM results show that the saturation magnetization (Ms) is strongly dependent on substrate temperature.

TRANSPARENT TiO2-PMMA NANOHYBRIDS OF HIGH NANOCRYSTALLINITY AND ENHANCED NONLINEAR OPTICAL PROPERTIES

Nanohybrid thin films of titania-polymethyl methacrylate ( TiO2 -PMMA) with varying degrees of nanocrystallinity have been successfully synthesized via an in-situ sol gel-polymerization route, assisted by subsequent thermal and water vapor treatments. Post-hydrothermal treatment by water vapor at relatively low temperatures led to a higher degree of crystallinity for TiO2 nanoparticles than the conventional thermal annealing. The degree of TiO2 crystallinity in the resulting nanohybrid films was studied by using XRD, FTIR, UV-Vis spectroscopies and HRTEM. The resulting nanohybrid thin films are highly transparent in the visible region, with an estimated band gap energies, Eg, close to that of anatase TiO2 (~ 3.20 eV). The nanocrystallinity level of TiO2 phase strongly affects both linear and nonlinear optical properties of the nanohybrids. A significant enhancement in linear refractive index, no, up to 1.780 and a third-order nonlinear optical susceptibility, χ(3) as high as 5.27 × 10-9 esu , were demonstrated with the nanohybrid exhibiting the enhanced TiO2 crystallinity and well-preserved PMMA matrix.

Nonlinear Optical Behavior of Transparent Nanohybrids of Nanocrystalline TiO<sub>2</sub> in Poly(methyl methacrylate) Prepared by In Situ Sol-Gel Polymerization Technique

Nanohybrid thin films consisting of nanocrystalline TiO2 particles in poly(methyl methacrylate)(PMMA) were successfully synthesized by in-situ sol-gel and polymerization assisted by spin coating. Using titanium isoproproxide (Ti-iP), methyl methacrylate (MMA) and 3-(trimethoxysily)propyl methacrylate (MSMA) as the starting materials, nanohybrids containing up to 60% Ti-iP in PMMA were realized. The resulting nanohybrid thin films coated on quartz substrates are optically transparent and demonstrate nonlinear optical behaviour, where their nonlinear absorption increases with the loading of Ti-iP in PMMA, as confirmed by Z-scan measurements. Using pump-probe technique, these thin films are shown to exhibit an ultrafast relaxation time of ~1.5 picosecond.

Development of Photo-functional Materials from Organic/Inorganic Nano-Hybrids

Organic/inorganic nano-hybrids are molecularly dispersed composite materials with polymers and metal oxides. As these materials have excellent transparency, they are expected to be applied for the optical usage. In particular, organic/inorganic hybrids with photo-functional polymers would be interesting materials with optical properties. Polysilanes are one of photo-functional polymers, whose functions are photodegradation, photoconductive, high refractive index, etc. We have been investigating about the preparation and properties of the novel nano-hybrids of polysilane with inorganic substances. Polymethylphenylsilane (PMPS)/silica or titania nano-hybrid thin films were prepared by a sol-gel reaction with PMPS block copolymers and corresponding metal alkoxides. The refractive index of nano-hybrid thin films could be controlled with the composition ratio of PMPS. After development of the UV-irradiated hybrid thin films with organic solvents, nano porous (ca. 20 nm) silica or titania thin films were obtained by removing the decomposed PMPS segments, and a high refractive index difference occurred between irradiated and non-irradiated part in the hybrid thin films. Furthermore, a hybrid thin film of polydihexylsilane (PDHS) and zirconia suppressed the thermochromism which is known as a characteristic of polydialkylsilane, and this hybrid thin film provided the high thermo-optic (TO) effect with an advantage for optical devices.

Controlling the crystallinity and nonlinear optical properties of transparent TiO2–PMMA nanohybrids

Titania–polymer nanohybrid thin films represent a new class of potential materials for optoelectronic applications. While most such nanohybrid thin films lack control in crystallinity, we report in this paper transparent nanohybrids of titania-polymethyl methacrylate (TiO2–PMMA) thin films having a remarkably enhanced nanocrystallinity. Post-treatments with water vapor at relatively low temperatures were applied on these thin films, following in situ sol–gel polymerization. They promoted rearrangement of flexible Ti–O–Ti bonds leading to enhanced crystallization of the TiO2 phase. The degree of TiO2 crystallinity in the resulting nanohybrid films was studied by using XRD, FTIR, UV–Vis spectroscopies and HRTEM. Both linear and nonlinear optical responses increase with the enhancement of TiO2 crystallinity in the nanohybrids. The highest two-photon absorption coefficient (β) and nonlinear refractive index (n2) were observed for the nanohybrid thin films with highest TiO2 crystallinity, as confirmed by open and closed aperture Z-scan techniques using 250 fs laser pulses at 800 nm, having a value of 2260 cm GW−1 and 6.2 × 10−2 cm2 GW−1, respectively.

Preparation of Intercalative Organic/MoO3 Nanohybrid Thin Films and Their VOC Gas Sensing Properties

ABSTRACTOrganic/MoO3 nanohybrid thin films have been successfully prepared by an ex-situ intercalation process. The host MoO3 films were first deposited on LaAlO3 (LAO) single crystal substrates by using a CVD method followed by the intercalation of butylammonium ions, (BuNH3)+, into the MoO3 films to give (BuNH3)xMoO3 thin films. The preparation of highly b-axis oriented MoO3 films is crucial to prepare the (BuNH3)xMoO3 films. The (BuNH3)xMoO3 thin films exhibit a resistance-increasing response to aldehyde gases as in the case of bulk samples, whereas no response was observed for methanol, ethanol, chloroform, acetone, toluene, and xylene. The thin film process developed for intercalative organic-inorganic hybrid makes it possible to apply this material in VOC sensor devices.

Photo-induced Optical and Chemical Properties of Polysilane/Inorganic Nano-Hybrids

ABSTRACTPolysilane/inorganic (silica, titania) nano-hybrids might be attractive materials for organic photonics. Polymethylphenylsilane (PMPS)/silica nano-hybrid thin films were prepared by a sol-gel reaction of PMPS block copolymers with alkoxysilanes. The refractive index of hybrid thin films could be controlled with the composition ratio of PMPS, and the value was changed by UV irradiation accompanying photodecomposition of PMPS. After development of the irradiated hybrid thin films, nano porous (ca. 20nm) silica thin films were generated by removing the decomposed PMPS segments and a high refractive index difference occurred between irradiated and non-irradiated part in the hybrid thin films. Furthermore, under photodecomposition of polysilane copolymers, polysilane functioned as a reducing agent of gold (III) ions to prepare the gold nanoparticles.

Transparent nanohybrids of nanocrystalline TiO2 in PMMA with unique nonlinear optical behavior

PMMA is one of the most versatile polymeric materials for applications in various technological areas including optics and electro-optics. While the current applications of PMMA in optics and electro-optics are limited by their linear optical behavior, we report here in this paper the unique nonlinear optical behavior of nanohybrids consisting of nanocrystalline TiO2 in PMMA. Transparent thin films of TiO2–PMMA nanohybrid on substrates were synthesized by in-situ sol–gel and polymerisation, assisted by spin coating. Using titanium isoproproxide (Ti-iP) as the starting material for nanocrystalline titania, together with methyl methacrylate and 3-(trimethoxysilyl)propyl methacrylate, nanohybrids containing up to 80% Ti-iP in PMMA were successfully realized. The resulting nanohybrid thin films coated on quartz substrates are optically transparent and demonstrate large nonlinear optical behavior, with an ultrafast response of <1.5 ps. The highest two-photon absorption coefficient (β) and nonlinear refractive index (n2) are observed with the nanohybrid thin film of 60 wt% Ti-iP in PMMA, as confirmed by the Z-scan technique.

Synthesis and VOC gas sensing properties of Polypyrrole / MoO3 Nanohybrids

ABSTRACTWe have prepared polypyrrole (PPy) / MoO3 nanohybrid thin films and evaluated their volatile organic compound (VOC) gas sensing properties. The (PPy)xMoO3 thin films have been prepared by intercalation reactions of highly oriented MoO3 thin films. Intercalation of hydrated sodium ions successfully proceeded without loosing the crystallographic orientation. The (PPy)xMoO3 thin films was obtained by replacing the hydrated sodium ions with PPy. The (PPy)xMoO3 thin films can detect formaldehyde gas by increasing in their electrical resistance, whereas they showed no response to toluene.