Organic-inorganic Precursor Research Articles

Microstructure Changes of Copper Nano Particles via Polymer Solution and Reduction Firing Processes.

Cu nano particles were fabricated at a very low temperature via polymer solution and reduction firing processes using a polyvinyl alcohol (PVA) and Ar-4%H2 gas mixture. In the process, copper nitrate and 5 wt% PVA solution were dissolved in D.I. water and the organic-inorganic precursor sols were dried to porous gels. The precursor gels were calcined in an air atmosphere, and then refired at 250 degrees C-300 degrees C under an Ar-4%H2 atmosphere for the reduction of CuO. The morphology of precursor gels and CuO and Cu powders was strongly dependent on the PVA content, and the as- calcined CuO readily deoxidized to Cu with minimal residual carbon. The polymer also contributed to an atomic-scale copper cation distribution, which resulted in nano-sized CuO and Cu powders. The Cu powder synthesized with PVA content in a 4:1 ratio showed a crystallite size of about 20 nm or less. In this paper, the microstructure changes of Cu nano particles at each set of processing conditions were examined by SEM and TEM observations.

Hybrid Nanogels Based on Chitosan Hydrochloride-Ascorbate Derived by Sol-Gel Biomimetic Synthesis

Nanostructured hydrogels obtained by the in situ sol-gel technology represent innovative systems for theranostic applications. Controlled self-assembly of charged macromolecular chains to form a polymer network due to specific non-covalent interactions is one of the methods to produce ionic biopolymer-based nanoscale gels. However, the structural lability and kinetic instability of such systems are significant disadvantages. In this study, we propose a preparation process of hybrid nanogels based on chitosan hydrochloride-ascorbate by biomimetic sol-gel synthesis at 20 and 80 °С using an organic-inorganic precursor. With the influence of the concentrations of the precursor, the binary chitosan salt, and a low-molecular-weight accelerator, the temperature of the sol-gel synthesis on the gelation time of our multicomponent chitosan-containing systems was evaluated. An increased concentration of the polymer salt, the introduction of an accelerator, and an increased temperature are shown to accelerate the gelation process. The refractive index (nD25) and pH of the silicon-chitosan-containing hydrogels were measured. A solid phase in these hydrogels was isolated by cold extraction combined with cryotreatment. Scanning electron microscopy shows that the solid phase of the hybrid nanogels is a matrix of agglomerated particles whose sizes increase with the chitosan concentration in the system.

Perpendicular growth of few-layered MoS2 nanosheets on MoO3 nanowires fabricated by direct anion exchange reactions for high-performance lithium-ion batteries

The morphologies and structures can be controlled by adjusting the solvent and sulfur source although an organic–inorganic precursor was not used.

Nano Copper Powders Synthesized by a Polymer Solution Method at Low Temperature.

Copper (Cu) nano particles were successfully fabricated at a significantly low temperature through a simple polymer solution route. In the process, the organic-inorganic precursor sols were turned to porous gels exhibiting volume expansion during the drying process. The PVA polymer, as an organic carrier, contributed to make an atom-scale homogeneous copper precursor gel, which resulted in fully crystallized, nano-sized copper powders through a low calcination temperature of 300 °C under Ar-4%H2 atmosphere. Variations in the processing technique, such as the content of PVA and calcination temperature, affected the microstructure and crystallization behavior of the synthesized powders. The copper powder synthesized with the PVA content of 4:1 ratio showed a crystallite size of about 10 nm or less with a high surface area. In this paper, the PVA solution technique for the fabrication of a nano-sized copper powder is introduced. The effects of the PVA content and calcination conditions on the powder morphology and crystallization are also studied. The characterization of the synthesized powders is conducted by using XRD, DTA/TG, SEM and TEM.

Hydroxyl-rich nanoporous carbon nanosheets synthesized by a one-pot method and their application in the in situ preparation of well-dispersed Ag nanoparticles

Nanoporous carbon nanosheets (CNSs) with high surface area have been synthesized by pyrolysis of organic–inorganic precursor. The CNSs with rich hydroxyl groups display remarkable reactivity and capability for in situ loading ultrafine Ag NPs.

Synthesis, structure, and properties of silicon oxycarbide aerogels derived from tetraethylortosilicate /polydimethylsiloxane

Abstract Porous silicon oxycarbide (SiCO) aerogel monoliths were prepared by the sol-gel method using Tetraethylortosilicate/Polydimethylsiloxane as organic-inorganic precursors. The precursor gels were dried by supercritical ethanol fluid and pyrolyzed at 1200 °C in nitrogen atmosphere to form SiCO aerogels. The as-prepared SiCO aerogels are amorphous and present a network microstructure, surface area of 198.04 m 2 /g, average pore diameter of 56 nm, and pore volume of 0.648 cm 3 /g. The thermal conductivity of aerogel monoliths is only 0.027 W/m·K at 25 °C (Hot disk method). The atom ratios of Si, C, O elements in the SiCO aerogels are 30.77%, 14.67%, 54.56% respectively. The network microstructure of the SiCO aerogels are retained until 1100 °C, and the chemical groups and crystal phase structures are kept up until 1200 °C. There is only 1.65% of weight-loss until the same heated at 1200 °C in air, which is one of the highest thermally stable temperatures for SiCO aerogels ever reported.

The properties of capillary columns with silica organic–inorganic MCM-41 type porous layer stationary phase

In this work, we report the method of capillary columns preparation for gas-solid chromatography with a porous layer of MCM-41 type silica sorbent. The porous layer was synthesized by the sol-gel method inside the column. Scanning electron microscopy (SEM) measurements were performed to obtain information about the porous layer. The loading capacity of the prepared columns was investigated. An adsorbent selectivity was changed by using different relative contents of organic-inorganic precursors: vinyltriethoxysilane (VTEOS) and tetraethoxysilane (TEOS). Properties of the columns prepared are discussed. Separating examples of C1-C4 hydrocarbons and some other compounds are presented.

Effect of ceria and zirconia nanoparticles on corrosion protection and viscoelastic behavior of hybrid coatings

Organic–inorganic hybrid nanocomposite coatings contain inorganic particles that are dispersed in organic phase in nanometric dimensions. Ceria and zirconia colloidal dispersions are uniformly distributed in the epoxy silica-based hybrid nanocomposite by sol–gel method and coated on 1050 aluminum alloy substrate with spin-coating technique. The hybrid sol is prepared by organic–inorganic precursors formed by hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane and tetraethylorthosilicate (TEOS) in acidic solution using bisphenol A as networking agent and 1-methylimidazole as initiator in the presence of various ratios of ZrO2 and CeO2 colloidal nanoparticles. Particle size distribution, surface morphology and inorganic components distribution were determined by scanning electron microscopy (SEM) and EDXA techniques. SEM and Si, Zr, Ce mapping micrographs proved the uniform distribution of nanoparticles in the coatings. Transmission electron microscopy indicated that the nanoparticles dimension stay at the nanoscale level. The glass transition temperature (Tg) and loss properties (damping) of coatings were evaluated by dynamic mechanical thermal analysis. The corrosion protection of the coatings on the 1050 AA substrate was studied by potentiodynamic measurements. The results indicated that by introducing ceria nanoparticles in 1:1 molar ratio to TEOS in coating composition, corrosion protection was improved. However, the simultaneous presence of two nanoparticles (i.e., ceria and zirconia in 1:1 molar ratio) in the coating compositions increased the corrosion protection efficiency up to 99.8 %. The multiple glass transitions and shifting to higher and wide range of temperatures by adding ceria and zirconia nanoparticles indicated a better network interaction between inorganic nanoparticles and organic molecular chains which also led to better corrosion protection of the coating in this composition.

A Facile Route Towards Inorganic Particles with Two Distinct Compartments Based on Electro‐Hydrodynamic Co‐Jetting

Inorganic Janus particles are prepared by electro-hydrodynamic (EHD) co-jetting of mixtures of organic polymers and inorganic precursors and are converted into inorganic particles by thermal calcination. Using this approach, bicompartmental SiO2 particles with iron oxide nanocrystals selectively loaded into one hemisphere are created. Moreover, bicompartmental particles composed of TiO2 and SiO2 are fabricated by EHD co-jetting.

Improvement of the hydrogen storage kinetics of NaAlH4 with nanocrystalline titanium dioxide loaded carbon spheres (Ti-CSs) by melt infiltration

Abstract Nanocrystalline titanium dioxide loaded carbon spheres (Ti-CSs) with 10wt% TiO 2 were synthesized through an easy one-step method using phenolic resols, titania nanoparticles and Pluronic F127 as organic carbon sources, inorganic precursors and surfactant, respectively. The results show that the as-prepared Ti-CSs composite is spherical shape with a diameter ranging from 0.3 to 2 μm, and rutile TiO 2 nanoparticles are distributed on the surface of the carbon spheres. Then the kinetics of NaAlH 4 was improved through depositing it on the surface of as-prepared Ti-CSs by melt infiltration. The results show that NaAlH 4 with Ti-CSs exhibits better hydrogen desorption kinetics than TiF 3 or nanocrystalline TiO 2 catalysted-NaAlH 4 , and it starts to release hydrogen at about 40 °C and releases about 25% of the hydrogen content during heating to 60 °C. The results from SEM and XPS show that hydrogen storage properties of NaAlH 4 were considerably improved due to the formation of special structure during melt infiltration and the nanocrystalline TiO 2 and/or amorphous phase Ti–Al clusters near the subsurface sites, which succeed in combining catalyst addition (TiO 2 nanoparticles) and nanoconfinement to improve the kinetics of NaAlH 4 .

Optimization of Ormosil Glasses for Luminescence Based Dissolved Oxygen Sensors

In the recent years, sol-gel films have been intensively used in optical sensors configurations. Due to its hydrophobic nature, ormosil films have been reported to be a promising supporting matrix for oxygen sensing dyes for measurements in aqueous media. In this work, the impact of the sol-gel host fabrication parameters in the characteristics of the resulting oxygen sensing membranes is thoroughly evaluated. Different combinations of organic-inorganic precursors, with different aging times, were tested as oxygen sensors. All the solution were doped with ruthenium complex Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline) to introduce oxygen sensitivity. Thin films were produced by dip coating of glass slides. The oxygen sensitive films were tested in aqueous phase in equilibrium with different oxygen gas compositions, using a phase-modulation technique. Sensor performance parameters such as Stern-Volmer constant, quenching efficiency and lifetime response are reported. The data obtained clearly indicates that increased aging times and longer organic groups produce sensors with the highest sensitivity to dissolved oxygen. From all sol-gel films produced, the BTEOS:TEOS (1:1) mixture is the most promising for sensor construction.

Polymerization of Hybrid Sol-Gel Materials Catalyzed by Photoacids Generation

Various methodologies combining sol-gel chemistry and photopolymerization were implemented to yield novel organic-inorganic nanocomposite photomaterials through photoacids generation. The first part of this paper focuses on cationic systems based on bifunctional organic-inorganic precursor. The photoacid-catalyzed cationic poly- merization and sol-gel polycondensation of an epoxytrialkoxysilane precursor enabled the simultaneous generation of the organic and inorganic phases. With a similar strategy, the combination of both radical and cationic photoinitiators is highlighted to achieve an efficient polymerization of a methacrylate silane derivative. Finally, the last part is devoted to the sol-gel photopolymerization of 3 different organo-bridged trialkoxysilane precursors [(R'O)3Si-R-Si(OR')3].

Tetraphenylporphyrin electronic properties: a combined theoretical and experimental study of thin films deposited by SuMBD

Porphyrins and their metal complexes are particularly well suitable for applications in photoelectronics, sensing, energy production, because of their chemical, electronic and optical properties. The understanding of the electronic properties of the pristine molecule is of great relevance for the study and application of the wide class of these compounds. This is notably important for the recently achieved in-vacuo synthesis of organo-metallic thin films directly from the pure free base organic-inorganic precursors in the vapor phase, and its interpretation by means of surface electron spectroscopies. We report on a combined experimental and theoretical study of the physical/chemical properties of tetraphenylporphyrin, H(2)TPP, deposited on the SiO(2)/Si(100) native oxide surface by supersonic molecular beam deposition (SuMBD). Valence states and 1s core level emissions of carbon and nitrogen have been investigated with surface photoelectron spectroscopies by using synchrotron radiation light. The interpretation of the spectra has been guided by density functional numerical experiments on the gas-phase molecule. Non-relativistic calculations were carried out for the valence states, whereas a two component relativistic approach in the zeroth-order regular approximation was used to investigate the core levels. The good agreement between theoretical and experimental analysis results in a comprehensive overview of the chemical properties of the H(2)TPP molecule, highly improving reliability in the interpretation of experimental photoemission spectra.

One-pot synthesis of amino functionalized mesoporous silica materials: using simulations to understand transitions between different structures

The rich phase behavior of surfactants can be exploited to design materials with a given desired structure and properties. One example includes amino functionalized mesoporous silicas, which can be used in different environmental applications, including removal of heavy metals from water and CO2 separation and purification. These applications may require a high concentration of functional groups, but the increased concentration of hybrid organic–inorganic precursors can lead to the destruction of the liquid crystals or transformation into other phases. In this work, we modeled the phase behavior of such systems using lattice Monte Carlo simulations and analyzed the distribution of hybrid organic–inorganic precursors to explain the observed changes in the liquid crystal structures. In particular, we observed that if the hybrid precursor is sufficiently hydrophobic, it can act as a cosurfactant, swell the core of the surfactant liquid crystal, and lead to structures with smaller interfacial curvature. On the other hand, if the hybrid precursor acts as a cosolvent it will solubilize the surfactant leading to the destruction of the preformed liquid crystal.

Monte Carlo simulations of self-assembling hexagonal and cage-like bifunctional periodic mesoporous materials

Self-assembly of lyotropic liquid crystalline mesophases formed by amphiphilic molecules was studied using computer simulations. The addition of an inorganic and two hybrid organic–inorganic precursors, one with a bridging and the other with a terminal organic functionality, lead to the formation of bifunctional hexagonally-packed mesoporous materials. These structures exhibit very ordered and uniform mesopores with the organic functional groups located in the cylindrical pores and in their walls, and are found to be stable over a relatively broad range of precursor concentrations. Hexagonal-to-lamellar and hexagonal-to-cubic phase transitions have been observed at constant surfactant concentrations by tuning the relative content of the hybrid precursors which modify the overall solvophilic character of the solvent and, as a consequence, the surfactant solubility in its surrounding environment. The long range ordered cubic phases show interconnected, roughly spherical mesocages of uniform size and an interesting distribution of the organic functionalities.

Electron beam writing of epoxy based sol–gel materials

We report the use of an epoxy based hybrid sol–gel material as negative resist for electron beam lithography (EBL). The matrix has been prepared starting from 3-glycidoxypropyltrimethoxysilane as specific organic–inorganic precursor and the synthesis has been strictly controlled in order to preserve the epoxy ring and to obtain a proper inorganic cross-linking degree. The film has been exposed to an electron beam, inducing the polymerization of the organic part and generating the film hardening. Preliminary results of a resolution test on the synthesized epoxy based sol–gel material, performed with electron beam lithography, are presented. Structures below 300 nm were achieved. The direct nanopatterning of this hybrid sol–gel system simplify the nanofabrication process and can be exploited in the realization of photonic devices. A demonstration has been carried out doping the hybrid films with commercial Rhodamine 6G and reproducing an already tested laser structure.

Laser damage of glycidoxypropyltrimethoxysilane based hybrid materials

Abstract The preparation of solid samples, having specific optical properties, is one of the main goals for the realization of devices in the photonic field. To this end, it is important to attain the best control of the optical properties in the final materials. The sol–gel technique is a powerful synthesis method allowing the preparation of matrices with high stability, mechanical resistance and high optical quality. The use of hybrid organic–inorganic precursors permits samples with different thicknesses, ranging from films of hundreds of nanometers to bulk samples of millimeters, to be obtained. The control of the synthesis protocol and the choice of precursors and catalyst allows the control of the final matrix microstructure, which is related to optical properties, like the laser damage threshold. In this work four different matrices, based on glycidoxypropyltrimethoxysilane and Zr alcoxide, have been prepared through sol–gel synthesis. An interpenetrating organic and inorganic network, controlled by the synthesis protocol, characterizes these matrices. The obtained materials show high resistance to the optical damage and long term stability.

A polymer solution technique for the synthesis of nano-sized Li 2TiO 3 ceramic breeder powders

Abstract Nano-sized Li2TiO3 powder was fabricated by an organic–inorganic solution route. A steric entrapment route employing ethylene glycol was used for the preparation of the nano-sized Li2TiO3 particles. Titanium isopropoxide and lithium nitrate were dissolved in liquid-type ethylene glycol without any precipitation. With the optimum amount of the polymer, the metal cations (Li and Ti) were dispersed in the solution and a homogeneous polymeric network was formed. The organic–inorganic precursor gels were turned to crystalline powders through an oxidation reaction during a calcination process. The dried precursor gel showed the carbon-free Li2TiO3 crystalline form which was observed above 400 °C. The primary particle size of the carbon-free Li2TiO3 was about 70 nm, and the structure of the crystallized powder was porous and agglomerated. The powder compact was densified to 92% of TD at a relatively low sintering temperature of 1100 °C for 2 h.

Nb–Ta, Nb–Mo and Nb–V oxides prepared from hybrid organic–inorganic precursors

New hybrid organic-inorganic materials based on group 5 elements and a well-defined polymeric matrix have been prepared and used as precursors for Nb-Ta and Nb-Mo mixed oxides. In this non-conventional but easily accessible route to multimetallic oxides, a copolymer of N,N-diallyl-N-hexylamine and maleic acid was synthesised and used as matrix to stabilise inorganic species generated in solution from (NH4)(6)Mo7O24-4H(2)O, NH4VO3, (gu)(3)[Nb(O-2)(4)] and (gu)(3)[Ta(O-2)(4)]. Solid-state studies indicate that the homogeneity of the blends can be kept up to about 0.5 mol Nb-v and Ta-v and 0.25 mol V-v per mol of repeat units of the copolymer. The calcination conditions of these homogeneous hybrid precursors were optimised to produce Nb-Mo, Nb-Ta and Nb-V oxides. While the thermal treatment of the Nb-V hybrid blends led only to a mixture of different phases, the characterisation of the final phases by X-ray diffraction (XRD) proved the formation of pure Nb2MO3O14 and showed that Nb-Ta oxides could be synthesised as single phases corresponding to a continuous series of solid solutions. (c) 2007 Elsevier Inc. All rights reserved.

Textural and electrochemical properties of carbon replica obtained from styryl organo-modified layered double hydroxide

Negative carbon replicas were obtained after pyrolysis of organo-modified layered double hydroxides (LDH) and dissolution of the inorganic moiety. The hybrid organic–inorganic precursors consisted of polystyrene sulfonate incorporated directly between LDH sheets of cationic composition Zn2Al or after in situ polymerisation of the monomers. The preparation conditions of the hybrid phase and the constraint imparted by the inorganic framework were found to affect strongly the textural properties. The carbons sequestered into the LDH intersheet gap present a textural hierarchy, i.e. a pronounced microporous character (micropore volume up to 1.07 mL g−1 and SBET = 2300 m2 g−1) and a mesoporosity. The nanotexture of the carbon replica was characterized by Raman spectroscopy. Finally, the carbons tested by cyclic voltammetry and complex impedance spectroscopy in two-electrode electrochemical supercapacitors in sulfuric acid medium present a capacitive behavior, i.e. a quasi rectangular response of intensity versus potential and a phase angle in the Z″–Z′ impedance plane close to π/2.