Preparation and second-order optical nonlinearity of inorganic–organic hybrid films

The sol–gel technique has been used to prepare a thin film for second-order nonlinear optics (NLO). An azo-dye molecule 2,5-dimethyl-4-(4′-nitrophenylazo)phenol (DMNPAP) was covalently bonded to the silicon oxide network through hydrolysis and co-condensation between the alkoxysilane dye and tetraethyl silicate (TEOS) in relatively high loading densities (43 wt%). The resulting film showed a thermal stability up to 302 °C in thermogravimetric analysis (TGA) thermograms and a flat surface morphology in atomic force microscope (AFM) image. The orientation behavior of the poled film was studied by UV–visible spectroscopy. The NLO activity (d₃₃), which was estimated to be 6.5 pm/v at 1064 nm by in situ second harmonic generation (SHG) measurement, the thermal stability of the second-order nonlinearity was also reported.     

Synthesis,structure and fluorescent property of a novel inorganic–organic zinc compound

Single crystals of a symmetrically substituted molecule, [Zn(C₃N₆H₆)(H₂O)_0.5Cl₂] (C₃N₆H₆)(H₂O)(1), have been obtained. The crystal structure of 1 shows the existence of novel layered type supramolecular structure constructed by dumbbell-shape coordinated Zn moleculeand one 2,4,6-triamine-s-triazine ligand. Crystallographic data for 1: monoclinic system, space group: C2/c, a = 12.2532(9), b = 13.8606(10), c = 18.3603(13) Å, = 99.7860(10), V = 3072.9(4) ų and Z = 8, D_c = 1.758 Mg/m³, R₁ = 0.0518. The fluorescent property of 1 has also been studied. The luminescent property of 1 attributable to both ligand ^* transitions and electronic transfer of Zn^II O transitions.     

Syntheses and structures of two new organic–inorganic hybrid lanthanide derivatives based on Keggin-type polyoxometalates

Two new organic–inorganic hybrid Keggin-type polyoxometalates containing lanth-anide(III) cations with 3D supramolecular framework structures, [La(DMSO)₈][PW₁₂O₄₀] (1) and [La(DMSO)₈][PMo₁₂O₄₀] (2) (DMSO = dimethyl sulfoxide), have been synthesized in aqueous solution under moderate conditions and further characterized by elemental analysis, inductively coupled plasma (ICP) analyses, IR spectroscopy, electronic spectra, thermogravimetric analysis, and single-crystal X-ray diffraction analyses. The title complexes exhibit similar 3D supramolecular frameworks directed by the different hydrogen bonding interactions. The TG curve exhibit the weight loss of complex 1, which can be divided into five stages, suggesting that the intensity of coordination bonds are different between La(III) and DMSO molecules.     

Study of the mechanical properties of two organic–inorganic hybrid systems: GPTMS/colloidal silica and GPTMS/TEOS

This work investigates the mechanical properties of different scratch resistant coatings, namely, a mixture of 3-glycidoxypropyltrimethoxysilane (GPTMS) with either colloidal silica particles or tetraethoxysilane (TEOS). Coatings were prepared by the hydrolysis and the condensation of the precursor's alkoxide (sol–gel process) with thermally catalyzed polymerization of epoxy ring of GPTMS. Dip deposition techniques were used on silicon substrate.The nanoindentation technique was used to analyze the force required to indent the coating with a diamond tip. At low forces, this technique, based on indentation depth, predicts the hardness and the elastic modulus of the coating, while at higher forces, cracks appear. Another analysis based on geometric approach, namely, the crack length, allows the determination of both coating and interface toughness.     

Dielectric investigations of organic–inorganic hybrid based on (2-hydroxypropyl) cellulose with nanosheet crystallites of quasi-TiO2

In this paper, dielectric spectroscopy investigations of organic–inorganic hybrid composite obtained from (2-hydroxypropyl)cellulose (HPC) with nanosheet crystallites of quasi-TiO₂ are presented. This hybrid belongs to the class of composites, which have no covalent bonds between organic and inorganic constituents and the behaviour of composite is determined mainly by interface of two constituents. The analysis of the molecular dynamics of the hybrid system reveals the influence of the nanosheet crystallites of quasi-TiO₂ on the relaxation processes of HPC matrix. The relaxation strength of γ process strongly increases in composite as compared to neat HPC. A shift to higher temperature has been evidenced in the case of α and β processes. A higher value of the slope of the maximum frequency vs. the inverse temperature for the α-relaxation of the composite has been observed. At high temperatures the mesomorphic behaviour of HPC has been drastically reduced in the composite. The results of our investigations are interpreted in terms of a presence of intermolecular forces between HPC and nanosheet crystallites of quasi-TiO₂.     

Solvothermal synthesis and crystal structure of an inorganic–organic hybrid compound [DAMS]2[CdI4] (DAMS = 4-dimethylaminostyryl-1-methyl-pyridinium)

An inorganic–organic hybrid compound [DAMS]₂[CdI₄] (DAMS = 4-dimethyl-amino- styryl-1-methylpyridinium cation) was synthesized via the solvothermal reaction of equimolar CdI₂ and DAMSI^– in a mixture of acetonitrile and H₂O (2:1 in volume ratio) at 130°C. The product was characterized by X-ray single crystal structure analysis. The crystals of the title compound are triclinic, , with a = 12.9849(19) Å, b = 13.1935(13) Å, c = 13.8792(10) Å, = 106.798(6)°, = 109.827(6)°, = 108.206(9)°, V = 1906.0(4) ų, Z = 2. The cadmium atom was bonded to 4 iodine atoms to form a distorted tetrahedron, which was surrounded by DAMS cations. There exist – stacking interaction between the 2 adjacent antiparallelly arrayed DAMS cations.     

Structure of hybrid (organic/inorganic) TiO2–SiO2 xerogels II: thermal behavior as monitored by temperature-programmed techniques and spectroscopy

Titanium-containing xerogels made by acid pre-hydrolysis of tetraethylorthosilicate (TEOS) and dimethyl-dimethoxysilane (SiMe₂(OMe)₂), followed by reaction with dichloro-diisopropyl titanium (TiCl₂(i-OPr)₂) were characterized by means of several techniques. The decomposition patterns of these xerogels, both in the presence and in the absence of oxygen are discussed in terms of the gaseous products' evolution under temperature-programmed (TP) reaction conditions, and diffuse reflectance infrared spectroscopy (DRIFTS). The primary decomposition routes of residual alkoxide groups are: (i) auto-redox (CO, CO₂) and dehydration (to olefins) under pyrolysis conditions; (ii) oxidative (CO, CO₂) under flowing air. The decomposition of the Si–C bond upon heating, as monitored by all three techniques, follows a pattern independent of that of (CH) species from −OR groups. The ²⁹Si MAS/NMR of these materials is dominated by the so-called D² (Me₂Si(OX)₂), Q³ ((OR)Si(OX)₃) and Q⁴ (Si(OX)₄) resonances. Fairly homogeneous proton envelopes around Si centers are evident from the NMR spectra of these materials in the proton cross-polarization mode.     

Nanostructured crystals of fluorite phases Sr1 − x R x F2 + x and their ordering: 9. The defect crystal and real structure of quenched fluorite phases Sr1 − x Ce x F2 + x (x = 0–0.5)

A Sr_0.7Ce_0.3F_2.3 crystal (CaF₂ type, sp. gr. $Fm\bar 3m$ ), obtained by quenching from melt, has been studied for the first time by X-ray diffraction. Fluorine vacancies and interstitial anions are found in the 8c and 32f sites, respectively. The defect ratio in the Sr_0.7Ce_0.3F_2.3 structure corresponds to the tetrahedral cluster configuration of defects {Sr_{4 ? n} Ce _n F₂₆}. The defect structure of quenched (at a rate of ～25 K/min) crystal differs from that of a crystal grown from melt (cooling at a rate of ～3 K/min) by the displacement of some cations (presumably Ce³⁺) along the threefold axis to the 32f site and the anisotropy of thermal vibrations of ions in the cluster core (F _int(32f)3). The concentration dependence of the lattice parameters of quenched Sr_{1 ? x} Ce _x F_{2 + x} phases (x = 0–0.5) is described by a third-order polynomial: a = 5.80009 + 1.166518 × 10^?3 x ? 1.124969 × 10^?5 x ² + 8.258155 × 10^?8 x ³. The compositional dependence of microdistortions is also nonlinear; maximum microdistortions are observed in the SrF₂ crystal. They decrease with an increase in the cerium concentration x to ～ 0.35. The minimum in the range x = 0.30–0.35 correlates with a composition corresponding to the peak (at x ～ 0.29) in the melting curves of the fluorite phase estimated from the phase diagram of the SrF₂-CeF₃ system (the method of thermal analysis).