A series of nitrogen-doped TiO2 nanocatalysts have been synthesized successfully by a two-step hydrolysis-calcination method in which condensed HNO3 (∼16 mol/L) was first used. In contrast to the traditional hydrolysis method, the time consumed in the hydrolysis process was shortened greatly. The content of nitrogen decreases as the calcination temperature increases, resulting in the variation of bandgaps of the as-synthesized N-doped TiO2 from 1.55 to 2.95 eV. Decomposition of methylene blue under visible light irradiation (λ ≥ 400 nm) has been carried out to evaluate the photocatalytic activity of the as-synthesized N-doped nanocatalysts. Compared to P25, greatly improved photocatalytic activity for water contaminant decomposition under visible light irradiation was obtained due to the doping of nitrogen into the titania system. The crystallinity of the photocatalysts was found to be less influential than the nitrogen content in determining the photocatalytic activity.

Nanoceria with phosphatase-like behavior shows its great potential for many important biological applications through a catalytic dephosphorylation process. Herein, we synthesize a series of porous nanorods of ceria (PN-CeO2) with the controllable surface Ce3+ fractions modulated by thermal annealing, understanding the correlations between their surface properties and reactivity for the dephosphorylation of p-nitrophenyl phosphate (p-NPP) and investigating their catalytic performance under various interferences. Our results suggest that PN-CeO2 with abundant surface defects deliver higher catalytic activity to break down p-NPP. Most importantly, PN-CeO2 exhibited a better adaptability over a wide pH range and preserved the catalytic activity over a wide temperature range from 20 to 80 °C, if compared with natural enzymes. Moreover, PN-CeO2 delivered the high catalytic stability against various interference ions. Their great prospects for practical applications were further demonstrated by dephosphorylation of DNA.

The impacts of a model globular protein (bovine serum albumin, BSA) on aggregation kinetics of graphene oxide (GO) in aquatic environment were investigated through time-resolved dynamic light scattering at pH 5.5. Aggregation kinetics of GO without BSA as a function of electrolyte concentrations (NaCl, MgCl, and CaCl) followed the traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and the critical coagulation concentration (CCC) was 190, 5.41, and 1.61 mM, respectively. As BSA was present, it affected the GO stability in a concentration dependent manner. At fixed electrolyte concentrations below the CCC values, for example 120 mM NaCl, the attachment efficiency of GO increased from 0.08 to 1, then decreased gradually and finally reached up to zero as BSA concentration increased from 0 to 66.5 mg C/L. The low-concentration BSA depressed GO stability mainly due to electrostatic binding between the positively charged lysine groups of BSA and negatively charged groups of GO, as well as double layer compression effect. With the increase of BSA concentration, more and more BSA molecules were adsorbed on GO, leading to strong steric repulsion which finally predominated and stabilized the GO. These results provided significant information about the concentration dependent effects of natural organic matters on GO stability under environmentally relevant conditions.

No abstract

Silver nanowires (AgNWs) are being widely utilized in an increasing number of consumer products, which could release silver to aquatic environments during the use or washing process, and have received growing concerns on their potential risks to bio-organisms and humans. The present study demonstrated that AgNWs mainly experienced direct oxysulfidation by reacting with dissolved sulfide species (initial S concentration at 1.6 mg/L) to produce silver sulfide nanostructures under environmentally relevant conditions. Granular AgS nanoparticles were formed on the surface of the nanowires. The sulfidation rate constant (k) of AgNWs was compared with those of silver nanoparticles (AgNPs) at different particle sizes. It was found that the k positively correlated with the specific surface areas of the silver nanomaterials. Natural organic matter (NOM) suppressed the sulfidation of AgNWs to different extents depending on its concentration. Divalent cations (Mg and Ca ions) substantially accelerated the sulfidation rates of AgNWs compared to monovalent cations (Na and K ions). At the same ionic strengths, Ca ions displayed the highest promoting effect among the four metallic ions.