Probing the chemical environment of 3-hydroxyflavone doped ormosils by a spectroscopic study of excited state intramolecular proton transfer

Abstract The spectroscopic properties of 3-hydroxyflavone (3-HF) molecules entrapped in films and in monoliths of sol–gel derived organically modified silicates (Ormosils) xerogels are studied by excitation and fluorescence spectroscopy as a function of the sol–gel precursors used for the synthesis. Different molar ratios of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and phenyltriethoxysilane (PTES) as precursors are used for the sol preparation. Emission and excitation spectra in the ultraviolet–visible range and photo-degradation curves as a function of time are collected with a spectrofluorimeter. The 3-hydroxyflavone optical properties change in the different networks, owing to the effects of the chemical environment on the excited state intramolecular proton transfer and to the solubility of the dye molecules in the different sol–gel systems. It turns out that the spectroscopic features can be used to probe the chemical state of the dye molecules microenvironment

Porphyrin-containing polyimide films deposited by high vacuum co-evaporation

Abstract Thin films of porphyrin-containing polyimide were produced by high vacuum co-evaporation of 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), 3,3′-diaminodiphenyl sulfone (DDS) and 5,10,15,20 meso-tetraphenyl porphyrin (TPP). The films were characterized by FT-IR analysis, optical absorption and emission spectroscopy. FT-IR analysis shows that the film matrix is comprised of only unreacted monomers. The conversion of monomers to polyamic acid and the following condensation to polyimide were studied by curing the samples at temperatures up to 240 °C. The amount of polyamic acid increases from room temperature to 120 °C, while at higher temperature it starts to condense to polyimide. Optical analysis shows that TPP is incorporated in the film matrix and its chemical state is determined by the interaction with the monomers, polyamic acid and polyimide. After curing the TPP molecules are finely dispersed in the polyimide matrix and their absorption and fluorescence properties are wholly preserved

Soluble phthalocyanines as optical gas sensing materials

A novel soluble phthalocyanine compound, i.e zinc phthalocyanine (sulfonamide) has been synthesized by chemical substitution of zinc phthalocyanine and used to produce thin solid films by means of the spin coating technique. The chemical structure of the spin coated films has been investigated by FT-IR analysis. Atomic Force Microscopy (AFM) has been used to characterize the film morphology and to measure the film thickness. The spin coated films have been tested as optical sensing materials of volatile organic compounds such as methanol, ethanol and 2-propanol. The change of optical reflectance of the films upon exposure to alcohol-vapour-containing atmospheres has been measured versus alcohol concentration and exposure time. The films exhibit a fast and reproducible response, with a complete and fast recovery in methanol and ethanol-containing atmospheres, while diffusion-driven effects appear during exposure to 2-propanol. The response and sensitivity of the films to ethanol vapour is higher than to methanol and 2-propanol

Optical and Scintillation Properties of Polydimethyl-Diphenylsiloxane Based Organic Scintillators

Polysiloxane based scintillators with high light yield have been synthesized. The polymer consists in cross-linked polydimethyl-co-diphenylsiloxane with different molar percentages of phenyl units. 2,5-diphenyl oxazole (PPO) and 2,5-bis(5-ter-butyl-2-benzoxazolyl)thiophene (BBOT) have been dispersed in the polymer as dopants. The energy transfer and scintillation capabilities have been investigated, for two different amounts of phenyl groups in the polymer network and for different concentrations of dye molecules, by means of fluorescence spectroscopy, ion beam induced luminescence (IBIL) and scintillation yield measurements with ? particles from an 241Am source. The luminescence features and the scintillation yields have been correlated to the composition of the scintillators

Siloxane-Based Nanocomposites Containing 6LiF Nanocrystals for Thermal Neutrons Detection

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Vapour Deposition Techniques for Producing Advanced Optical Materials

Vapour Deposition Techniques for Producing Advanced Optical Material

Plasma-deposited copper phthalocyanine: A single gas-sensing material with multiple responses

Copper phthalocyanine (CuPc) thin films have been deposited by glow discharge-induced sublimation (GDS). This physical technique allows to produce very high porosity films, whose response to gases is much more intense than evaporated films. It has been found that both electrical and optical properties of these films change upon gas exposure due to the gas/film interaction. Electrical response of the films has been tested by exposing the samples to NOx-containing atmospheres and by measuring the slope of the electrical surface current versus gas concentration. This way NO2 and NO concentrations down to 0.1ppm and 10ppm have been measured, respectively, with response times shorter than 2min. Optical responses have been tested by measuring the change of light reflectance at a fixed wavelength upon exposure to ethanol-containing atmospheres down to concentrations of few thousands of ppm. Response times of less than 10s have been obtaine