Sonication In Ethanol Research Articles

Synthesis of ribbons of silver nanoparticles in lamellar liquid crystals

Ribbons of silver nanoparticles have been synthesized in lamellar lyotropic liquid crystals formed from a nonionic surfactant, C 12E 4 (tetraethylene glycol monododecyl ether), and aqueous silver ion solution by the reduction of the silver ions using the surfactant itself as reductant. The effects of temperature, composition, and ageing are studied by UV–vis absorption spectroscopy and transmission electron microscopy (TEM). It has been shown that the obtained ribbons either at 50°C or at room temperature mainly consist of roughly close-packed silver nanoparticles about 2–3 nm and a few larger silver nanoparticles distributed in or attached on the ribbons. The nanoparticles constituting the ribbons are revealed to have a crystal order corresponding to metallic silver. These ribbons, which are up to several hundred nanometers wide and several micrometers long, can withstand repeated sonication in ethanol and can readily twist and fold into three-dimensional spatial configurations. On decreasing C 12E 4 concentration, i.e. on increasing water layer thickness, the sizes of the smaller particles that form the ribbons remain essentially unchanged whereas the proportion and/or sizes of the larger particles are increased. The proportion of the larger particles also increases with ageing.

Characterization of the surface carbonyl and hydroxyl coverage on glassy carbon electrodes using Raman spectroscopy

A fluorescein derivative was synthesized and covalently bonded to hydroxyl groups on glassy carbon surfaces. Since the fluorescein fluorescence was quenched by the carbon surface, its resonance Raman spectrum could be observed at surface coverages of approximately 1%. The fluorescein/GC bond was stable to repeated sonication in ethanol, but was rapidly hydrolyzed by mild base. This new label for surface hydroxyl groups was combined with a similar label for carbonyl groups to assess changes in the coverage of surface C–OH and CO with GC pretreatment. The relative densities of these species varied with both the initial GC heat treatment and with subsequent chemical treatment in hot HNO3 or hot KOH solutions. HNO3 increased the CO coverage on vacuum heat treated (VHT) GC, while KOH increased the C–OH coverage. Chemical treatments of GC following polishing or heat treatment were less selective, due to the significant initial coverage of CO and C–OH. In all cases, significant surface oxygen on GC was present in forms other than CO and C–OH.