A basic understanding of the properties of thin polymer films is of fundamental importance for developing applications in nanotechnology. Results of energy and angle dispersive x-ray reflectivity measurements on polymer thin films as a function of temperature exhibit reversible negative thermal expansion below the glass transition temperature T(g). Above T(g), the thickness expansion becomes almost equal to the expected bulk volume expansion. These results could be explained on the basis of evolution of disorder with temperature at the interfaces, chain entanglement and associated entropy changes.

Results of thermal gravimetric analysis, electrical conductivity and 'H n.m.r. studies of Prussian Blue, Fei+[Fe2+(CN),], -nH,O, a classical mixed-valence compound exhibiting semiconducting behaviour in the temperature range 3&150 OC, are presented. Three different stages of hydration together with the anhydrous form have been identified by thermal gravimetric analysis. The proton magnetic resonance investigation suggested that there are bound water molecules and electrical conductivity studies confirm the existence of these four forms by the four different values of the activation energy. Variations of the activation energy on hydration have been interpreted qualitatively in terms of the energy band and energy levels of Fe2+ and Fe3+.

The glass transition process gets affected in ultrathin films having thickness comparable to the size of the molecules. We observe systematic broadening of the glass transition temperature (T(g)) as the thickness of an ultrathin polymer film reduces below the radius of gyration but the change in the average T(g) was found to be very small. The existence of reversible negative and positive thermal expansion below and above T(g) increased the sensitivity of our thickness measurements performed using energy-dispersive x-ray reflectivity. A simple model of the T(g) variation as a function of depth expected from sliding motion could explain the results.

The actin cytoskeleton is required for the maintenance of the cell shape and viability of bacteria.

We report an effective method to produce surface-enhanced Raman scattering (SERS) substrates with improved enhancement efficiency, high uniformity, greater chemical and physical stability, and absolute synthetic reproducibility. Nanobipyramidal gold (Au) core and silver (Ag) shell nanorods (NRs) with variable length were prepared simply by varying the Ag precursor amount during growth, and we successfully prepared NRs of lengths from 200 to 1200 nm and studied their formation mechanism and morphology using transmission electron microscopy (TEM) and their optical properties by using UV–vis–near-IR (NIR) and Raman spectroscopy. Here we have utilized the properties of both Au and Ag nanoparticles by synthesizing Au@Ag core–shell NRs for high SERS enhancement. NRs have stronger absorption and large scattering cross sections for electromagnetic radiation, and variation of the aspect ratios of these NRs leads to a broad-band surface plasmon tuning in the vis–NIR region. The relative SERS enhancement efficiencies of these core–shell Au@Ag NRs have been measured by using 4-mercaptobenzoic acid (4-MBA), crystal violet, and 4-mercaptopyridine as Raman tags, and the obtained SERS results show their huge enhancement (∼1010 for 4-MBA), which was substantiated through finite-difference time-domain computer simulations. Our work shows superior SERS enhancement compared to the previously reported results for pure Au and Ag NRs and bimetallic NRs, with the Au core and Ag shell having an aspect ratio in the same range.