Measurements of the temperature- and concentration-dependent surface tensions of aqueous solutions of methanol, 1- and 2-propanol, 1- and 2-butanol, acetic, propionic, and butanoic acids, and acetone were used to determine the standard free energies, enthalpies, and entropies of adsorption from the vapor phase onto a water surface. The saturated surface coverage of all these species is approximately 1014 molecules cm-2. The standard enthalpies of adsorption are correlated to the enthalpies of solution, suggesting that these molecules are partially solvated in the adsorbed state. These results further suggest that atmospheric water droplets could be coated with an organic layer.

A series of SERS-active nanostructures were produced by exposing a freshly deposited silver film (fabricated to be as free from roughness as practicable) to a solution containing a mixture of 1-decanethiol (m) and 1,9-nonanedithiol (d) of varying concentrations of m to d, then allowing colloidal silver nanoparticles to interact with the surface. Silver nanoparticles were found to bind exclusively to films which were prepared from solutions with a nonzero concentration of the dithiol implying that the nanoparticles were tethered to the silver surface by the dithiol with one of the thiolate groups bound to the nanoparticle and the other to the silver film. Intense SERS spectra were observed even from samples in which the m/d concentration ratio was so large that the adsorbed molecules in the vicinity of only approximately 8 +/- 3 nanoparticles were illuminated by the diffraction-limited focused laser beam. At such high dilution, the molecules (numbering at most approximately 330) residing in the SERS "hot spots" associated with the approximately 8 nanoparticles consisted primarily of m (although, of course, for each nanoparticle, at least one molecule in the hot spot had to be d to serve as the linker). This was corroborated by the SERS spectra. An analysis is presented, which accounts for the fact that as the concentration ratio of m/d increases, the SERS intensity associated with bands belonging to m first increases to a maximum then decreases. The nanoparticle-metal film system presented here is a simple embodiment of a more general range of SERS-active sensing platforms in which a molecular tether is used to create a SERS hot spot that (although nanosized) is large enough to accommodate analyte molecules that cannot themselves function as linkers, which are subsequently detected by SERS at the few-molecule level.

Plant protection products containing nanomaterials that alter the functionality or risk profile of active ingredients (nano-enabled pesticides) promise many benefits over conventional pesticide products. These benefits may include improved formulation characteristics, easier application, better targeting of pest species, increased efficacy, lower application rates, and enhanced environmental safety. After many years of research and development, nano-enabled pesticides are starting to make their way into the market. The introduction of this technology raises a number of issues for regulators, including how does the ecological risk assessment of nano-enabled pesticide products differ from that of conventional plant protection products? In this paper, a group drawn from regulatory agencies, academia, research, and the agrochemicals industry offers a perspective on relevant considerations pertaining to the problem formulation phase of the ecological risk assessment of nano-enabled pesticides.

Abstract. Room temperature surface tension measurements on the ternary system: nitric acid -sulfufic acid -water are reported. There is a dramatic decrease in the surface tension of sulfuric acid -water solutions as nitric acid is added. This decrease is most pronounced in the stratospherically-relevant range of sulfuric acid concentrations, between 50 and 75 wt% sulfuric acid. The surface tension decrease indicates a change in surface energy and surface composition and / or structure associated with partitioning of molecular HNO3 to the surface. The presence of HNO3 at the surface may be related to the reported changes in heterogeneous reactivity of sulfuric acid solutions when exposed to nitre acid.Introduction.