The resonance Raman (RR) spectra of beta-carotene have been studied in solution and in the protein complexes of photosystems I and II (PS I, PS II). The experimental studies are complemented by density functional theory (DFT) calculations that allow for a consistent assignment of most of the experimental RR bands in the region between 900 and 1650 cm(-1). Thus, it was shown that the prominent peak at ca. 1525 cm(-1) is composed of two closely spaced modes, both of which dominated by C=C stretching coordinates of the polyene chain. These two modes exhibit different excitation profiles in the region of the allowed electronic S(0) --> S(2) transition with maxima that are separated by ca. 1300 cm(-1). Calculated RR spectra and excitation profiles obtained by time-dependent DFT in conjunction with the transform method indicate that the enhancement pattern of these modes cannot be rationalised within the Condon approximation (A-term scattering). Furthermore, symmetry considerations rule out enhancement via vibronic coupling. Instead, we suggest that the different excitation profiles of the two modes result from force constant changes and mode mixing upon electronic transition (Dushinsky rotation). RR spectra and excitation profiles are very similar in solution and in the protein complexes. Thus, the excitation-dependent frequency variation of the 1525-cm(-1) peak in PS I and PS II is an intrinsic molecular property of beta-carotene and does not reflect different pools of the pigments in specific molecular environments.

Organic coatings based on inhibitor loaded inorganic containers for smart corrosion inhibition are presented. The overall coating performance is strongly infl uenced by the containers as well as their inhibitor capacity, compatibility with the coating matrix, and size. The important effect of container size is described for the fi rst time in this work by investigating two types of mesoporous silica containers of different diameters: 80 and 700 nm. The coating physical properties (thickness and adhesion) are comparable for both container types. In contrast, the coating barrier properties are strongly infl uenced by the container size as assessed with electrochemical impedance spectroscopy (EIS). The incorporation of bigger containers reduces the coating resistance by a factor of two. Surprisingly, despite the similar amounts (20 wt%) of loaded inhibitor (2-mercaptobenzothiazole), different active inhibition ability is detected with the scanning vibrating electrode technique (SVET). Therefore, it is found that coatings with smaller containers exhibit better self-healing performance.

Application of mesoporous silica nanoparticles (MSNs) as delivery tools for self-healing coatings is limited by spontaneous leakage and specifically responsive release of small molecular inhibitors. In this work, a pH/sulfide ion responsive release system based on MSNs using a Cu-BTA complex forms at the openings of the mesopores into which BTA (corrosion inhibitor) and benzalkonium chloride (biocide) are loaded. The spontaneous leakage of active species is completely avoided and premature release of the loaded composition was lowered to 0.02. The responsive release begins when the pH is lower than 5 or [S^2-] is higher than 0.02 mM (about 0.6 ppm). The hybrid coating containing the responsive release system exhibits feedback self-healing property sensitive to lowering of pH and sulfide ion concentration and, at the same time, provides a high barrier level for a long time. Due to incorporation of biocide in the release system, the coating is also provided with antifouling properties

In the present work we have studied β ‐carotene dissolved in dichloromethane by means of resonance Raman spectroscopy. To obtain the Raman excitation profiles Raman spectra of β ‐carotene have been acquired at various wavelengths throughout the visible region. It was found that the position of the prominent peak at ca. 1524 cm–1 varies with the excitation wavelength indicating the involvement of two different modes. Possible origins of the different enhancement pattern of the two modes are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)