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Summary.:  The structure and the gasochromic properties of sol-gel-derived WO3 films with a monoclinic structure (m-WO3) were studied by focusing attention on the size of the monoclinic grains. The size of the m-WO3 grains is modified by the addition of an organic–inorganic hybrid to the initial peroxopolytungstic acid (W-PTA) sols which are based on chemically bonded poly-(propylene glycol) to triethoxysilane end-capping groups (ICS-PPG). The results obtained with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the heat treatment (500°C) of WO3/ICS-PPG (0.5, 1, 2, 5, and 10 mol%) composite films results in a change of their morphology, and nanodimensional pores are formed between the grains. High-resolution TEM (HRTEM) analysis revealed the presence of an amorphous phase on the outside of the m-WO3 grains, whereas energy-dispersive X-ray spectra (EDXS) showed that this amorphous phase contained W and Si. Impregnation of the WO3/ICS-PPG film with H2PtCl6/i-propanol solution followed by heat treatment at 380°C gave the films their gasochromic properties. Infrared and Raman spectroscopic studies of the WO3/ICS-PPG film confirmed the results of the corresponding HRTEM and EDXS analysis. In situ UV/Vis and in situ IR spectra of the films were measured in hydrogen and in air, and colouring/bleaching changes and the corresponding kinetics were assessed. The IR spectra of gasochromically coloured films showed that the mesoporous WO3/ICS-PPG (1 mol%) film transforms to tetragonal H x WO3 bronze. The IR spectra of the H x WO3 bronze are discussed with the aim to establish the existence of the metal-OH vibrations of gasochromically formed oxyhydroxide tungsten bronze.

The hydration mechanism of bovine serum albumin (BSA) is studied, and we analyze (de)hydration spectra displayed previously. We first determine the three elementary (de)hydration spectra on which all these (de)hydration spectra can be decomposed. They correspond to three different hydration mechanisms for the protein, which we define after a quantitative analysis performed in a second step. The first mechanism, which involves ionization of carboxylic COOH groups, occurs at low hydration levels and rapidly reaches a plateau when the hygroscopy is increased. It is a mechanism that involves a single H2O molecule and consequently requires somewhat severe steric conditions. The second mechanism occurs at all hydration levels and, because it involves more H2O molecules, requires less severe steric conditions. It consists of the simultaneous hydration of one amide N&bond;H group and one carbonyl-amide C&dbond;O group by four H2O molecules and one carboxyl COO⁻ group by eight H2O molecules. The third mechanism is simpler and consists of the introduction of H2O molecules into the hydrogen-bond network of the hydrated protein. It becomes important at a high hydration level, when the presence of an appreciable number of H2O molecules makes this hydrogen-bond network well developed. This analysis also shows that 80 H2O molecules remain embedded in one dried protein made of 604 peptide units. They are held by hydrogen bonds established by N&bond;H groups and at the same time they establish two hydrogen bonds on two carbonyl-amide C&dbond;O groups. The proportion of free N&bond;H groups can be determined together with that of carbonyl-amide C&dbond;O groups accepting no hydrogen bonds and that of carbonyl-amide C&dbond;O groups accepting two hydrogen bonds. The proportion of N&bond;H groups establishing one hydrogen bond directly on a carbonyl-amide C&dbond;O group is 65%, which is the proportion of peptide units found in α helices in BSA. © 2000 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 54–67, 2001

The results of preliminary infrared (IR) spectrometry experiments on bovine serum albumin (BSA) films are presented. An analysis of spectral variations due to raising the temperature and deuteration of N&bond;H groups leads to the assignment of most IR bands of BSA. From this analysis we furthermore deduce that at 115°C only hydrogen bonds established by N&bond;H groups on the still present H2O molecules, which are so strongly bound to the protein that they do not evaporate, are weakened, some of which are broken. These N&bond;H⋮OH2 groups represent some 5% of all N&bond;H groups in the dried protein. Spectral changes due to hydration by water vapor are also analyzed and a precise method to measure the water-vapor pressure of the atmosphere surrounding the BSA film, or equivalently the relative humidity, is described. Various procedures to measure the number of H2O molecules embedded in BSA are then presented and evaluated. One of them is selected as the best one for proteins, because it matches previous measurements based on gravimetric methods. This procedure is subsequently used in a study that is devoted to the determination of the various hydrogen-bond configurations, or interaction configurations, which are adopted by H2O molecules during the various steps of hydration of BSA. This first analysis of hydration spectra allows the completion of the assignment of IR bands. The various spectral components of the amide I band, which are interchanged during the hydration process, cannot be assigned to various secondary structures, as is usually proposed. It suggests that this usual assignment should be used with care, especially by taking into account the state of hydration, when one wishes to obtain structural information from it. © 2000 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 40–53, 2001