Stimulated Raman scattering in transparent glass-ceramics (TGCs) based on bulk nucleating phase Ba2NaNb5O15 were investigated with the aim to explore the influence of micro- and nanoscale structural transformations on Raman gain. TGCs are composed of nanocrystals that are 10–15 nm in size, uniformly distributed in the residual glass matrix. A significant Raman gain improvement for both BaNaNS glass and TGCs with respect to SiO2 glass is demonstrated, which can be clearly related to the nanostructuring process.

Stimulated Raman scattering in transparent glass-ceramics (TGCs) based on bulk nucleating phase Ba2NaNb5O15 were investigated with the aim to explore the influence of micro- and nanoscale structural transformations on Raman gain. Nanostructured TGCs were synthesized, starting with 8BaO·15Na2O·27Nb2O5·50SiO2 (BaNaNS) glass, by proper nucleation and crystallization heat treatments. TGCs are composed of nanocrystals that are 10–15 nm in size, uniformly distributed in the residual glass matrix, with a crystallinity degree ranging from 30 up to 50% for samples subjected to different heat treatments. A significant Raman gain improvement for both BaNaNS glass and TGCs with respect to SiO2 glass is demonstrated, which can be clearly related to the nanostructuring process. These findings show that the nonlinear optical functionalities of TGC materials can be modulated by controlling the structural transformations at the nanoscale rather than microscale.

The surface and catalytic properties of oxide ternary materials consisting of niobium-phosphorus-silicon, Nb-P-Si, with Nb/P = 1 and general formula xNb(2)O(5)center dot xP(2)O(5)center dot(100-2x)center dot SiO2, with x=2.5, 5, 7.5, and 10, and Si content ranging from 95 to 80 mol% are presented. Amorphous gel-derived samples were obtained, characterized by a very high degree of silicon cross-linking with presence of Si-O-Nb bridges, allowing phosphorus to be stably anchored to the matrix through Nb-O-P bonds. The morphology (surface area and porosity), the intrinsic acidity (density and average strength of the surface acid sites, by PEA-TPD in a TGA-DSC coupled instrument), and the nature of the acid sites were determined. The LAS/BAS ratio has been evaluated by FTIR of adsorbed pyridine in absence/presence of water to discover the differences between the intrinsic and effective nature of the acid sites. The amount of acid sites decreased with the Nb-content in the samples as well as the surface average acid strength. Both LAS and BAS are maintained in the presence of water, even if BAS are predominant in any case. The catalytic performances of the Nb-P-Si samples in the reaction of inulin hydrolysis were investigated in aqueous solution under mild conditions (below 100 degrees C). (C) 2017 Elsevier B.V. All rights reserved.

A series of TiO2-based hybrid inorganic-organic materials was synthesized by sol-gel and characterized by thermal and spectroscopic techniques. The xerogels have an amorphous structure, with part of Ti4+ ions stably coordinated to acetylacetonate ligands. Ligand-to-metal charge transfer results in an extended light absorption in the visible range, with a significant reduction of the band gap compared to the reference TiO2. The hybrid structure is also related to the unusual presence of superoxide radical anions stably adsorbed on the materials surface. These properties make the studied materials active in the degradation of organic pollutants: their catalytic efficiency was tested in the removal of 2,4-dichlorophenol from water without light irradiation.

Here, we report the structural characteristics, the surface properties, and the catalytic performances of a Nb-P-Si ternary oxide material (2.5Nb(2)O(5).2.5P(2)O(5).95SiO(2), 2.5NbP) in two reactions of importance for biomass valorisation and green industrial production: hydrolysis of inulin and esterification of oleic acid with, polyalcohol for biolubricant production. High dispersion of the Nb centers, ascertained by UV-vis-DRS, Si-29, P-31, and H-1 solid-state NMR spectroscopy, is the key point for the successful activity of 2.5NbP. Intrinsic and effective acidities of the sample were studied by FT-IR of adsorbed pyridine in the absence and presence of water and by volumetric titrations of the acid sites in cydohexane and in water, to enlighten the nature and amount of acid sites in different environments. For both studied reactions, 2.5NbP catalyst exhibits water-tolerant acidic sites, mainly Bronsted ones, giving higher activity and better stability in the reaction medium than well-known niobium oxophosphate catalyst, which is considered one of the best water-tolerant acid catalysts.

Ti3+ self-doped black titania is obtained by a simple annealing in air without harsh conditions nor external reducing agents.

Two synthetic strategies were developed for in-situ modification of a silica sol gel matrix in a PEEK tubing, to obtain a hybrid monolith with entrapped lipases. A suitable combination of the sol-gel precursors (tetramethoxysilane, methyltrirnethoxysilane and n-propyltrimethoxysilane) was found, for the simultaneous improvement of the monolith adhesion to the tubing internal surfaces and of the catalytic properties of the entrapped enzyme.The effects of the immobilization procedure were characterized as regards both the catalytic properties of the enzyme, as well as the secondary structure of lipases by FTIR The catalytic efficiency of the entrapped enzyme was better preserved in more hydrophobic microenvironment. The improved stability of the biocatalysts allows further industrial applications. (C) 2016 Elsevier B.V. All rights reserved.

Amorphous niobium–phosphorus–silicon mixed oxide gels in which phosphorus remains stably bonded to a siloxane matrix by niobium bridges have been obtained by a new hydrolytic sol–gel route.

˙O2−superoxide radicals are firmly adsorbed on the surface of the hybrid material giving oxidative degradation without any light irradiation.

The hybrid sol-gel zirconia-acetylacetonate amorphous material (HSGZ) shows high catalytic activity in oxidative degradation reactions without light or thermal pretreatment. This peculiar HSGZ ability derives from the generation of highly reactive oxygen radical species (ROS) upon exposure to air at room conditions. We disclose the origin of such unique feature by combining EPR and DRUV measurements with first-principles calculations. The organic ligand acetylacetonate (acac) plays a pivotal role in generating and stabilizing the superoxide radical species at the HSGZ-air interfaces. Our results lead the path toward further development of HSGZ and related hybrid materials for ROS-based energy and environmental applications.

A fast method for the preparation of block-copolymer-based hybrid composite nanostructures and titania substrates well oriented over a large area, is illustrated.

The sol-gel synthesis of undoped and B- or Al-doped ZnO thin films were critically examined with particular reference to the influence of the pH of the reaction medium on some of their specific characteristics, such as thickness, morphology, doping level and optical properties, in view of their application in the photovoltaic field.Using triethanolamine (TEA) as chelating agent, a range of basic pH from 7.66 to 8.76 was explored starting from a very concentrated zinc acetate dehydrate (ZAD) solution in ethanol, [Zn2+] = 1.0 M, and keeping the ZAD/TEA= 1.A more basic environment gives more porous films whose thickness and crystallinity are higher than those achieved at lower pH. It was found that the morphology, as well as the sheet resistance (Rs) of films, depends on both pH and doping. Increasing the pH the Rs decreases for both undoped and doped films. At a certain pH undoped films exhibit a granular microstructure and lower Rs than B- or Al-doped films which exhibit a finer texture, characterized by a lower porosity. Optical properties strongly depend on the pH as well. Increasing the pH, a noticeable blue shift effect was observed, that was attributed mainly to structural changes and to a lesser extent to the Burnstein-Moss effect. (C) 2014 Elsevier B.V. All rights reserved.

A method is developed for rapid preparation of titania substrates using a sol-gel preparation route in combination with an amphiphilic block copolymer (BCP) template, acting as structure directing agent. The method consists in performing the spin coating of an initial solutions of BCP and titania species in a controlled atmosphere using a flux of solvent vapors (Rapid-Flux-Solvent-Atmosphere, RFSA method). The method is demonstrated in the case of thin films of polystyrene-b-poly(oxyethylene) BCP (PS-PEO) with cylindrical morphology of PEO domains in the PS matrix, characterized by the selective inclusion of titanium species inside the PEO cylinders. Upon removal of the organic matrix by heat treatment at 600 degrees C, titania substrates of different morphology are obtained depending on the concentration of titania precursor and processing conditions. The method allows preventing the negative effect of hydrolysis and condensation reactions of Ti species and titania substrates with morphology reminiscent of that one achieved in the hybrid nanostructured thin films are obtained. The RFSA method is simple, direct, and it is of particular interest for systems that require a short processing time to eliminate the solvent and to obtain regular nanostructured thin-films over large area. Merit figures such as the degree of hexagonal order and the degree of coverage of the surface with titania motifs are identified to characterize the hybrid composites and titania substrates. (C) 2014 Elsevier Ltd. All rights reserved.

The intrinsic catalytic activity of a hybrid gel-derived ZrO2-acetylacetonate (HSGZ) material towards the oxidative degradation of phenanthrene (PHE), in aqueous solution and in the dark, was revealed for the first time.The HSGZ catalyst is a polymeric network of zirconium oxo-clusters on the surface of which part of Zr4+ ions are involved in strong complexation with acetylacetonate (acac) ligands. The HSGZ gave significant PHE degradation rates acting as radicals initiator without any light irradiation at 30 degrees C.Free radicals were formed on the solid surface by the coexistence of Zr(IV)-acac and Zr(III)-acac(center dot) complexes in equilibrium at a given temperature, from which reactive oxygen species were produced in the presence of molecular O-2. A direct evidence of radical's presence on HSGZ solid surface was obtained by EPR spectroscopy.The analysis of the degradation products confirmed that the reaction goes on through the formation of intermediate free radicals, leading to the first ring-opening and to the formation of phthalates as main intermediates. Subsequently, low molecular weight alkanes are produced. Finally, a deep oxidation of the intermediates occurs completing the mineralization process. The HSGZ catalyst showed a good stability under the reaction conditions, retaining its catalytic activity after repeated tests. (C) 2014 Elsevier B.V. All rights reserved.

The oxidative degradation of 2-methyl-4-chlorophenoxyacetic acid (MCPA), 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB), 4-chlorophenoxyacetic acid (4-CPA) and 2,4-dichlorophenoxyacetic acid (2,4 D) by ZrO2-acetylacetonate hybrid catalyst (HSGZ) without light irradiation was assessed. The thermal stability of the catalyst was investigated by thermogravimetry, differential thermal analysis, and Fourier transform infrared spectroscopy. For each herbicide, a virtually complete removal in about 3 days without light irradiation at room temperature was achieved. The removal kinetics of the herbicides has been satisfactorily characterized by a double-stage physico-mathematical model, in the hypothesis that a first-order adsorption on HSGZ surface is followed by the herbicide degradation, catalytically driven by HSGZ surface groups. The long-term use of the HSGZ catalyst was assessed by repeated-batch tests. The specific cost for unit-volume removal of herbicide was evaluated by a detailed cost analysis showing that it is comparable with those pertaining to alternative methods.

Manganese oxide catalysts supported on monolithic yttria stabilized zirconia honeycombs were studied for H2O2 decomposition in view of space propulsion applications. The materials were prepared by impregnation (IM), precipitation (PR) and sol-gel (SG) methods and characterized by N-2 adsorption, SEM and H-2 temperature programmed reduction (TPR). The catalytic activity for H2O2 decomposition was studied under vapour phase conditions. The tests were carried out in a flow apparatus at T = 200 degrees C, gas hourly space velocity (GHSV) = 2.00 and 2.67 s(-1), H2O2 concentrations of 11.3 mol%. The redox properties of the catalysts were markedly influenced by the preparation method. In the SG catalyst, a large fraction of Mn was not reducible in the TPR tests differently from the PR and IM materials. Despite this effect, the SG catalyst showed an activity comparable or higher than that of PR and IM, due to a more effective dispersion of Mn species. A too strong effect of space velocity on H2O2 conversion was attributed to an autocatalytic effect. A radical mechanism was hypothesized: it was assumed that a reaction between O-2 and Mn species produced radicals that promoted the overall reaction. (C) 2013 Elsevier B.V. All rights reserved.