Improvement of the photovoltaic efficiency via exposure of organic poly(3-hexylthiophene) (P3HT) and phenyl-C₆₁-butyric acid methyl ester (PCBM) devices to solvent vapor at room temperature is reported. In situ photoluminescence (PL) and Raman spectroscopy, in conjunction with ex situ optical absorption and atomic force microscopy, have been used to provide insight into the nanoscale morphological changes occurring during solvent vapor annealing. We found that in 1 : 1 composites of P3HT : PCBM, suppression of PL, narrowing in line-width of the 1442 cm⁻¹ P3HT Raman peak, and strong modifications in the optical absorption spectra were observed during solvent vapor annealing, while minimal changes occurred in pure P3HT films. We attribute these spectral modifications to de-mixing of PCBM and subsequent stacking of P3HT in coplanar conjugated segments, similar to what is observed during thermal annealing.

A simple postdeposition method for improving the conductivity of transparent and conducting single-wall carbon nanotube (SWNT) thin films via exposure to nitric acid and thionyl chloride is reported. A systematic study on a range of films of variable density and from different commercial sources of SWNTs is performed. The functionalized films possess sheet resistances as low as that of indium tin oxide (ITO) $(\sim 30\Omega ∕◻)$ albeit at lower transmittance $(\sim 50\%)$ . At $80\pm 5\%$ transmittance, the functionalized films have resistance values ranging from $150\text{to}300\Omega ∕◻$ . The SWNT films, however, are more flexible than ITO. The stability of the functionalized films upon annealing and processing in solvents (water, methanol, and chloroform) is also reported.

Gibbs free-energy calculations based on density functional theory have been used to determine the possible source of failure of boron carbide just above the Hugoniot elastic limit (HEL). A range of ${\mathrm{B}}_4\mathrm{C}$ polytypes is found to be stable at room pressure. The energetic barrier for shock amorphization of boron carbide is by far the lowest for the ${\mathrm{B}}_{12}(\mathrm{CCC})$ polytype, requiring only $6\mathrm{GPa}\approx \mathrm{P}(\mathrm{HEL})$ for collapse under hydrostatic conditions. The results clearly demonstrate that the collapse of the ${\mathrm{B}}_{12}(\mathrm{CCC})$ phase leads to segregation of ${\mathrm{B}}_{12}$ and amorphous carbon in the form of 2–3 nm bands along the (113) lattice direction, in excellent agreement with recent transmission electron microscopy results.

In this study we introduce in situ Raman spectroscopy as an effective tool to distinguish between reversible and irreversible thiol modifications in L-cysteine, the most critical host for sulphydryls in proteins and enzymes. We place special emphasis on the conditions under which the formation and breakage of disulphide bonds is reversible and produces free thiol groups. Thiol groups from L-cysteine are highly reactive and are frequently converted into disulphide bonds via reaction with mercaptans, including S-methyl methanethiosulfonate (MMTS). It was previously claimed that disulphide groups can be reversibly introduced in and eliminated from L-cysteine in order to restore a free thiol group, using a reductant such as tris(2-carboxyethyl)phosphine (TCEP). Raman spectroscopy is found to effectively monitor the formation and subsequent breaking of disulphide bonds, and demonstrates that although TCEP is effective in breaking disulphide bonds, an excess of TCEP is required to reversibly form free thiol groups from L-cysteine. These results will be critical for cysteine–metal bonding investigations. Our Raman mode assignment in MMTS and TCEP also provides a benchmark for future studies using these compounds.