Organic-inorganic Hybrid System Research Articles

Photo-responsive properties of azobenzene small molecules in sol-gel hybrid TiO_2/ormosil organic-inorganic matrices

Azodye-doped TiO(2)/ormosil hybrid materials for photonic applications were prepared by a low temperature sol-gel process from an organic-inorganic hybrid system. Acid-catalyzed solutions of gamma-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane mixed with tetrapropyl orthotitanate were used as hybrid matrix precursors. The trans-cis-trans photoisomerization of azobenzene small molecules in sol-gel hybrid organic-inorganic matrices was induced by a photoirradiation with UV light and subsequent visible light. It was found that the hybrid film doped with azodyes and heated at a lower temperature was much better for applications in optical storage or optical switch. The planar waveguide properties of the hybrid films were also investigated by using a prism coupling technique. These results indicates that it is possible for the as prepared hybrid films to allow directly integrating on the same chip the optical storage or optical switch devices with the pump source.

Enhancement of the Curie Temperature by Isomerization of Diarylethene (DAE) for an Organic−Inorganic Hybrid System: Co4(OH)7(DAE)0.5·3H2O

Intercalation of an organic photochromic molecule into layered magnetic systems may provide multifunctional properties such as photomagnetism. To build up a photosensitive multifunctional magnet, an organic-inorganic hybrid system coupled with a photochromic diarylethene anion, 2,2'-dimethyl-3,3'-(perfluorocyclopentene-1,2-diyl)bis(benzo[b]thiophene-6-sulfonate) (DAE), and cobalt LDHs (layered double hydroxides), Co4(OH)7(DAE)0.5.3H2O, was synthesized by the anion exchange reaction between Co2(OH)3(CH3COO).H2O and DAE. In the dark and under UV-irradiated (313 nm) conditions, Co4(OH)7(DAE)0.5.3H2O with open and closed forms of DAE were obtained, respectively. The magnetic susceptibility measurements elucidated ferromagnetic intra- and interlayer interactions and Curie temperatures of TC = 9 and 20 K for cobalt LDHs with the open and closed forms of DAE, respectively. The enhancement of the Curie temperature from 9 to 20 K by substitution of the open form of DAE with the closed form of DAE as an intercalated molecule is attributed to the delocalization of the pi-electrons in the closed form of DAE, which enhances the interlayer magnetic interaction. The enhancement of the interlayer magnetic interaction induced by the delocalization of pi-electrons in intercalated molecules is strongly supported by the fact that the Curie temperature (26.0 K) of cobalt LDHs with (E,E)-2,4-hexadienedioate having a conjugated pi-electron system is enormously higher than that (7.0 K) of the cobalt LDHs with hexanedioate. By UV irradiation at 313 nm, Co4(OH)7(DAE)0.5.3H2O shows the photoisomerization of DAE from the open form to the closed one in the solid state, which leads to the enhancement of Curie temperature.

Yellow-to-violet up-conversion luminescence in neodymium-doped sol-gel GeO2∕γ-glycidoxypropyltrimethoxysilane hybrid planar waveguides

Neodymium-doped GeO2∕γ-glycidoxypropyltrimethoxysilane hybrid planar waveguide films were prepared by a low-temperature sol-gel technique from an organic-inorganic hybrid system for photonic applications. Optical properties such as refractive index, thickness, propagation modes, and attenuation coefficient of the hybrid planar waveguides were investigated by using a prism coupling technique. An intense room-temperature yellow-to-violet up-conversion emission at 397nm (D3∕24→I13∕24) was measured from the hybrid planar waveguide film heated at a low temperature of 100°C upon excitation with a xenon lamp at the wavelength of 580nm. In addition to this intense violet emission, a relatively weak ultraviolet emission at 376nm and a blue emission at 468nm were also observed. The mechanism of the up-conversion emission is proposed, and they indicate that the excited-state absorption process originating from the long-lived F3∕24 excited state should be responsible for the up-conversion process.

Investigation of the two-photon polymerisation of a Zr-based inorganic–organic hybrid material system

Abstract Two-photon polymerisation of photo-sensitive materials allows the fabrication of three dimensional micro- and nano-structures for photonic, electronic and micro-system applications. However the usable process window and the applicability of this fabrication technique is significantly determined by the properties of the photo-sensitive material employed. In this study investigation of a custom inorganic–organic hybrid system, cross-linked by a two-photon induced process, is described. The material was produced by sol–gel synthesis using a silicon alkoxide species that also possessed methacrylate functionality. Stabilized zirconium alkoxide precursors were added to the precursor solution in order to reduce drying times and impart enhanced mechanical stability to deposited films. This enabled dry films to be used in the polymerisation process. A structural, optical and mechanical analysis of the optimised sol–gel material is presented. A Ti:sapphire laser with 80 MHz repetition rate, 100 fs pulse duration and 795 nm is used. The influence of both material system and laser processing parameters including: laser power, photo-initiator concentration and zirconium loading, on achievable micro-structure and size is presented.

Ferromagnetism and its photo-induced effect in 2D iron mixed-valence complex coupled with photochromic spiropyran

Iron mixed-valence complex, ( n-C 3H 7) 4N[Fe IIFe III(dto) 3](dto = C 2O 2S 2), shows a spin-entropy driven phase transition called charge transfer phase transition around 120 K and a ferromagnetic transition at 6.5 K. These phase transitions remarkably depend on the hexagonal ring size in two-dimensional honeycomb network structure of [Fe IIFe III (dto) 3] ∞. In order to control the magnetic properties and the electronic state in the dto-bridged iron mixed-valence system by means of photo-irradiation, we have synthesized a photo-sensitive organic-inorganic hybrid system, (SP)[Fe IIFe III(dto) 3](SP = spiropyran), and investigated the photo-induced effect on the magnetic properties by the measurements of magnetic susceptibility, ESR, IR, UV-vis and 57Fe Mössbauer spectra. Upon UV irradiation at 337 nm, a broad absorption band between 500 nm and 600 nm appears and continuously increases with the photo-irradiation time, which implies that the UV irradiation changes the structure of spiropyran from closed form to open one in solid state. The photochromism in spiropyran changes the ferromagnetic transition temperature and the coercive force.

Study on photomagnetism of 2-D magnetic compounds coupled with photochromic diarylethene cations

Intercalation of an organic photochromic molecule into the magnetic system provides multifunctionalities such as photomagnetism. In order to build up a photosensitive multifunctional-material, we have synthesized an organic-inorganic hybrid system consisting of layered-perovskite-type copper halides and photochromic diarylethenes. By mixing the stoichiometric amounts of CuCl 2 and 2,2′-dimethyl-3,3′-(perfluorocyclopentene-1,2′-diyl)bis-(benzo-[b]thiophene-6-ammonium)( 1) in aqueous hydrochloric acid and methanol solution, we obtained ( 1)CuCl 4. In the dark synthetic condition, the resulting compound with open-form 1a has an intralayer ferromagnetic interaction whose exchange coupling constant is estimated at J/ k B = 10.7 K. Additionally, this compound shows antiferromagnetic transition at T N = 3 K because of the antiferromagnetic interaction between adjacent sheets. In UV irradiated synthetic condition, the resulting compound with close-form 1b has a weaker intralayer ferromagnetic interaction ( J/ k B = 6.9 K) and shows no magnetic phase transition above 2 K. By the photo-irradiation, we can control the antiferromagnetic transition and the intralayer magnetic interaction.

Hybrid Organic–Inorganic Conductor Coupled with BEDT-TTF and Photochromic Nitrosyl Ruthenium Complex

Abstract An organic–inorganic hybrid system coupled with an organic conductor and photosensitive transition metal complex has a possibility to exhibit fascinating multifunctionalities, such as photo-controllable conductor. To explore multifunctional materials, such as a photo-tunable conductor, we prepared (BEDT-TTF)4[RuCl5(NO)]·C6H5CN (BEDT-TTF: 4,5-bis(ethylenedithio)tetrathiafulvalene) by electrocrystallization, and investigated the structural and physical properties. X-ray crystallographic analysis shows alternate layers of BEDT-TTF cations and ruthenium complex anions. The organic layer is formed by the dimers of BEDT-TTF arranged almost perpendicular to each other, which indicates that the donor arrangement of this salt belongs to κ-type. Based on the Raman spectrum, the oxidation state of the BEDT-TTF molecules is estimated to be +0.7. X-ray structural analysis and the EPR spectra suggest that there is a partial electron transfer from BEDT-TTF to the π* orbital of NO ligand in [RuCl5(NO)] through a short intermolecular contact. A magnetic susceptibility measurement and the EPR spectra proved this compound to be a localized spin system due to a strong on-site Coulomb repulsion, which results in the semiconducting behavior of this compound.

Reversible photomagnetism in a cobalt layered compound coupled with photochromic diarylethene

Photomagnetism is one of the most attractive topics in recent research on molecular solids. In order to produce a photo-controllable magnet, we have synthesized a novel organic–inorganic hybrid system coupled with a photochromic diarylethene anion, 2,2′-dimethyl-3,3′-(perfluorocyclopentene-1,2-diyl)bis(benzo[ b]thiophene-6-sulfonate) ( 1a) and cobalt LDHs (layered double hydroxides). Based on the elemental analysis, the title compound, which was synthesized by the anion exchange reaction between Co 2(OH) 3(CH 3COO)·H 2O ( 2) and 1a, has the chemical composition, Co 4(OH) 7( 1a) 0.5·3H 2O ( 3). Powder X-ray diffraction analysis revealed the interlayer distance of c=27.8 Å. The magnetic susceptibility measurements elucidated the ferromagnetic intra- and inter-layer interactions and the Curie temperature of T c=9 K. By UV irradiation of 313 nm, 3 shows the photo-isomerization of diarylethene anion from the open form to the closed one in solid state, which leads to the decreases in the coercive field and the remnant magnetization. Furthermore, the photo-excited state is returned to the initial state (open form) almost reversibly by visible irradiation of 550 nm.

New organosilyl derivatives of the Dawson polyoxometalate [alpha2-P2W17O61(RSi)2O]6-: synthesis and mass spectrometric investigation.

In the field of functionalized polyoxometalates, organosilyl derivatives of polyoxotungstate constitute a special class of hybrid organic-inorganic system. The first organosilyl derivative of the monovacant Dawson heteropolyoxotungstate [alpha2-P2W17O61]10- was obtained by three different methods. The use of two organosilanes as reagents enabled the preparation of the functionalized polyoxometalate [alpha2-P2W17O61(RSi)2O]6- in good yield. Electrospray (ESI-MS) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and 183W, 31P, and 29Si NMR spectroscopy were used to characterize the composite systems. In several cases, ESI-MS analyses generated reduction processes which were compared to those related to [PMo11VO40]4-, the highly reducible Keggin polyoxometalate.

Preparation and electrochemical study of cerium–silica sol–gel thin films

Design and development of suitable multilayered systems for delaying corrosion advance in metals requires that both the alteration mechanisms of the metal and the behaviour and properties of the protective coatings be known. Coatings prepared by the sol–gel method provide a good approach as protective layers on metallic surfaces. This kind of coatings can be prepared from pure chemical reagents at room temperature and atmospheric pressure, with compositions in a very wide range of environmentally non-aggressive precursors. Sol–gel coatings based on siloxane bonded units were prepared starting from an organic–inorganic hybrid system. The precursors were γ-methacryloxypropyltrimethoxysilane (MAP) and tetramethoxysilane (TMOS). Cerium nitrate hexahydrate in three different concentrations was added. Cerium salts may perform a similar protective effect to that carried out by the well-known lead oxides and chromium salts, even though in this case a negative environmental impact is not expected. Application of coatings upon pure zinc substrates and common glass slides were performed by spinning. Coated samples were heat treated at 40°C for 6 days. Optical measurements (UV-Vis absorption and diffuse reflectance spectroscopies) pointed out that the coatings were colourless and transparent, reducing the diffuse reflectance of the metallic surface up to ∼60%. Optical and scanning electron microscopies (SEM) allowed observation of the texture and microstructure of the coated samples, both before and after the corrosion tests were carried out. Likewise, the remaining sols were kept to gelify at 60°C for 4 days and then powdered to obtain suitable samples for analysing them by other characterisation techniques (Fourier transformed infrared, FTIR and differential thermal analysis, DTA). Electrochemical measurements were performed by impedance spectroscopy. This technique was used to clarify the anticorrosive protection role of cerium ions incorporated into the hybrid sol–gel network. The effect of cerium concentration on the impedance spectra was analysed, as well as the system behaviour against the corrosive medium (0.6M NaCl aqueous solutions), as a function of exposure time. From the electrochemical point of view, the sol–gel films behave as a conversion coating on the metallic surface.

Effects of titanium content on sol-gel hard optical films prepared in an organic-inorganic hybrid system

The effects of titanium content on the optical and mechanical properties of silica–titania hard optical films by the sol-gel technique using γ-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, and tetrapropylorthotitanate as starting materials are studied. Thermal gravimetric analysis, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy are used to investigate the optical and structural properties of the films. The results indicate that crack-free and high transparency silica–titania film with a thickness more than 0.6 μm can be obtained by a single spin-coating process after a heat treatment at 500 °C. The hardness and Young’s modulus of the films are characterized by a nanoindenter and they show a linear dependence on titanium content. Hardness as high as 6.60 GPa is obtained in a 0.5 M titanium content film and heat treated at 800 °C. It is proposed that the high hardness of the film may be related to the carbon and titanium content in the film.

Complex nanostructured materials from segmented copolymers prepared by ATRP.

The development of new controlled/living radical polymerization processes, such as Atom Transfer Radical Polymerization (ATRP) and other techniques such as nitroxide mediated polymerization and degenerative transfer processes, including RAFT, opened the way to the use of radical polymerization for the synthesis of well-defined, complex functional nanostructures. The development of such nanostructures is primarily dependent on self-assembly of well-defined segmented copolymers. This article describes the fundamentals of ATRP, relevant to the synthesis of such systems. The self-assembly of block copolymers prepared by ATRP is illustrated by three examples. In the first, block copolymers of poly(butyl acrylate) with polyacrylonitrile phase separate, leading to spherical, cylindrical or lamellar morphologies, depending on the block copolymer composition. At a higher temperature, polyacrylonitrile block converts to nanostructured carbon clusters, whereas poly(butyl acrylate) block serves as a sacrificial block, aiding the development of designed nanostructures. In the second example, conductive nanoribbons of poly(n-hexylthiophene) surrounded by a matrix of organic polymers are formed from block copolymers prepared by ATRP. The third example describes an inorganic-organic hybrid system consisting of hard nanocolloidal silica particles (approximately 20 nm) grafted by ATRP with well-defined polystyrene-poly(benzyl acrylate) block copolymer chains (approximately 1000 chains per particle). Silica cores in this system are surrounded by a rigid polystyrene inner shell and softer polyacrylate outer shell.

Preparation and Characterization of Hybrid Silica-Poly(ethylene glycol) Sonogel

An inorganic-organic hybrid system, silica-poly(ethylene glycol) songel is reported. This system was prepared via sol-gel method by varying varous processing variables. e.g. ultrasonic radiation time, gelling temperanture, PEG content and its molecular weight. Various experimental techniques wee employed to analyze the morphological, mechanical and optical properties of the system. The results were discussed in the light of existing theories. The sonogel system exhibited the common features of inorganic-organic hybrids. wt% PEG sonogel exhibited the morphological and optical properties superior to those reported earlier for the classic gels and found suitable for device applications.

Low optical loss planar waveguides prepared in an organic–inorganic hybrid system

HfO 2 -(3-glycidoxipropil)trimethoxisilane (GPTS) planar waveguides were prepared by a sol–gel route. A stable sol of Hafnia nanocrystals was prepared and characterized by photon correlation spectroscopy and high resolution transmission electron microscopy. The suspension was incorporated in GPTS host and the resulting sol was deposited on borosilicate substrates by the spin coating technique. Optical properties such as refractive index, thickness, number of propagating modes, and attenuation coefficient were measured at 632.8, 543.5, and 1550 nm by the prism coupling technique as a function of the HfO2 content.

Electron Paramagnetic Resonance Study of Magnetic Ordering in MnPS3, Mn0.79PS3(4,4′-bipy)0.42 and Mn0.84PS3(1,10-Phen)0.64 Compounds

We report Electron Paramagnetic Resonance (EPR) studies on intercalation ferromagnets Mn0.79PS3(4,4′-bipy)0.42 and Mn0.84PS3(1,10-phen)0.64 and their antiferromagnetic host MnPS3, in the temperature range 300–15 K. The nature of the organic guest cation appears to have a strong influence on the magnetic behaviour of this inorganic-organic hybrid system. The continued appearance of the exchange-narrowed sharp line, characteristic of the paramagnetic phase, even at 15 K suggests that the bulk of the intercalate ferromagnets in this system do not attain a completely ordered state.

TG-DTA-MS and DSC studies on the thermal-treatment process of the 20% AlO 3/2–SiO 2–epoxySiO 3/2 organic–inorganic hybrid system

TG-DTA-MS and DSC techniques were applied to study the thermal behaviors, such as volatilization, evaporation of the liquid solvent phase and the organic modifying radicals of 20% AlO 3/2–SiO 2–epoxySiO 3/2 organic–inorganic hybrid system prepared by the sol–gel method in the thermal treatment process.

Filling control of the 1-D band of TCNQ in H-bonded organic-inorganic hybrid system

A new concept for filling control of the 1-D band of TCNQ is proposed in the charge-transfer complex, [Pd(H 2edag)(Hedag)]TCNQ (edag=ethylenediaminoglyoxime). By using protonation-deprotonation processes, the CT complexes having different band-fillings (−0.2, −0.7, −1.0) have successfully been obtained.