Some of the most active scientific research fronts of the past decade are centered on ionic liquids. These fluids present characteristic surface behavior and distinctive trends of their surface tension versus temperature. One way to explore and understand their unique nature is to study their surface properties. This critical review analyses most of the surface tension data reported between 2001 and 2010 (187 references).

No abstract

No abstract

In the present work, the adsorption of human serum albumin (HSA) on commercially pure titanium with a titanium oxide layer formed in a H(2)O(2) solution (TiO(2) cp) and on TiO(2) sputtered on Si (TiO(2) sp) was analyzed. Adsorption isotherms, kinetic studies, and work of adhesion determinations were carried out. HSA exchangeability was also evaluated. Surface characterization was performed by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and wettability studies. The two TiO(2) surfaces have very distinct roughnesses, the TiO(2) sp having a mean R(a) value 14 times smaller than the one of TiO(2) cp. XPS analysis revealed consistent peaks representative of TiO(2) on sputtered samples as well as on Ti cp substrate after 48 h of H(2)O(2) immersion. Nitrogen was observed as soon as protein was present, while sulfur, present in disulfide bonds in HSA, was observed for concentrations of protein higher than 0.30 mg/mL. The work of adhesion was determined from contact angle measurements. As expected from the surface free energy values, the work of adhesion of HSA solution is higher for the TiO(2) cp substrate, the more hydrophilic one, and lower for the TiO(2) sp substrate, the more hydrophobic one. The work of adhesion between plasma and the substrates assumed even higher values for the TiO(2) cp surface, indicating a greater interaction between the surface and the complex protein solutions. Adsorption studies by radiolabeling of albumin ((125)I-HSA) suggest that rapid HSA adsorption takes place on both surfaces, reaching a maximum value after approximately 60 min of incubation. For the higher HSA concentrations in solution, a multilayer coverage was observed on both substrates. After the adsorption step from single HSA solutions, the exchangeability of adsorbed HSA molecules by HSA in solution was evaluated. The HSA molecules adsorbed on TiO(2) sp seem to be more easily exchanged by HSA itself than those adsorbed on TiO(2) cp after 24 h. In contrast, after 72 h, nearly all the adsorbed albumin molecules effectively exchange with other albumin molecules.

Room-temperature ionic liquids based on the imidazolium cation are presently widely studied, but more data on important properties such as viscosity and surface tension are required. In this work, two imidazoliumbased ionic liquids, 1-ethanol-3-methylimidazolium tetrafluoroborate [C 2 OHMIM][BF 4 ] and 1-methyl-3octylimidazolium tetrafluoroborate [OMIM][BF 4 ], were investigated. The former is a member of a new series that contains the alcohol (CH 2 ) 2 OH as a functional group. The latter, already studied by several authors, has a long side chain in the imidazolium ring that is responsible for its surfactant properties. The surface tension was determined using the pendant drop technique in a wide temperature range, (298 to 470) K, which has never been explored before with ILs. The viscosity was measured using a new technique (a quartz crystal microbalance) between (288 and 328) K. The surface tension and the viscosity of [C 2 OHMIM][BF 4 ] are unexpectedly high when compared with those of [OMIM][BF 4 ]. The experimental values were interpreted in terms of the existing theories.