TNP [BSA-Biotin]

Charging and aggregation of titania nanosheets (TNS) and spherical titania nanoparticles (TNP) were studied in aqueous solutions of ionic liquids. The pH and the length of the alkyl chain of the IL cations [1-methylimidazolium (MIM+), 1-ethyl-3-methylimidazolium (EMIM+), and 1-butyl-3-methylimidazolium (BMIM+)] were systematically varied in the experiments. No detectable interaction was observed between the IL cations and the positively charged TNS or TNP surfaces at low pH, where the imidazolium derivatives are the co-ions. For the negatively charged titania nano-objects, significant adsorption of MIM+ and EMIM+ took place, leading to charge neutralization and overcharging at appropriate concentrations. The BMIM+ behaved like a simple salt constituent causing charge screening. For both TNS and TNP, the MINI+ < EMIM+ < BMIM+ counterion order was obtained in the critical coagulation concentrations, indicating that MIM+ was the most effective in destabilization of the dispersions. The major interparticle forces were of electrostatic origin; however, viscous stabilization was also observed at high IL concentrations. The same aggregation mechanism and charging behavior were found for the titania nano-objects irrespective of their shape. The results shed light on the hydrophilic nature of the surface of the TNS and TNP of negative charge, in contrast to earlier findings with hydrophobic colloidal particles, where the increasing alkyl chain length gave rise to higher destabilization power. The charging properties were governed by specific adsorption of the IL constituents, while the major interparticle forces were qualitatively well-predicted by the Derjaguin, Landau, Verwey, and Overbeek theory.

In photocatalytic systems, TiO2 based particles in suspensions tend to aggregate spontaneously, resulting in low efficiency for light utilization and photocatalytic activity. In this study, various TiO2 nanoparticles with different shapes were synthesized and characterized via various analysis. In atmosphere and aqueous environment, the nanoparticles demonstrated different properties in the nature of the agglomerations. Photocatalytic performances of the as-prepared samples were confirmed to be strongly influenced by the dispersion stabilities with TiO2 nanotube exhibited higher colloidal dispersion stability and photocatalytic activity. Mixing binary TiO2 photocatalysts with different shapes as a simple approach was firstly proposed for enhancing photoreforming hydrogen production from bio-glycerol aqueous solution. At a specific mixing ratio, the mixed suspension of TiO2 nanosphere and nanosheet retained excellent colloidal dispersion stability, and photocatalytic hydrogen production was significantly promoted with its maximum H-2 production amount as 2.1-2.9 times high as that of TNP and TNS, respectively. This strategy of enhancing colloidal dispersion stability may provide new ideas for the design of efficient and energy-saving photocatalytic system. (c) 2018 Elsevier B.V. All rights reserved.