Optimization of N doping in TiO2 nanotubes for the enhanced solar light mediated photocatalytic H2 production and dye degradation.

Herein, we report the optimization of nitrogen (N) doping in TiO2 nanotubes to achieve the enhanced photocatalytic efficiencies in degradation of dye and H2 gas evolution under solar light exposure. TiO2 nanotubes have been produced via hydrothermal process and N doping has been tuned by varying the concentration of urea, being the source for N, by solid-state dispersion process. The structural analysis using XRD showed the characteristic occupancy of N into the structure of TiO2 and the XPS studies showed the existence of Ti-N-Ti network in the N-doped TiO2 nanotubes. The obtained TEM images showed the formation of 1D tube-like structure of TiO2. Diffuse reflectance UV-Vis absorption spectra demonstrated that the N-doped TiO2 nanotubes can efficiently absorb the photons of UV-Vis light of the solar light. The optimized N-doped TiO2 nanotubes (TiO2 nanotubes vs urea @ 1:1 ratio) showed the highest degradation efficiency over methyl orange dye (∼91% in 90 min) and showed the highest rate of H2 evolution (∼19,848 µmol h-1.g-1) under solar light irradiation. Further, the recyclability studies indicated the excellent stability of the photocatalyst for the durable use in both the photocatalytic processes. The observed efficiency was ascribed to the optimized doping of N-atoms into the lattices of TiO2, which enhanced the optical properties by forming new energy levels of N atoms near the valence band maximum of TiO2, thereby increased the overall charge separation and recombination resistance in the system. The improved reusability of photocatalyst is attributed to the doping-induced structural stability in N-doped TiO2. From the observed results, it has been recognized that the established strategy could be promising for synthesizing N-doped TiO2 nanotubes with favorable structural, optical and photocatalytic properties towards dye degradation and hydrogen production applications.

An efficient green multi-component reaction strategy for the synthesis of highly functionalised pyridines and evaluation of their antibacterial activities.

An efficient green multi-component reaction (MCR) method has been developed for the synthesis of 2-amino-4-aryl/heteroaryl-6-(pyridin-2-ylthio)pyridine-3,5-dicarbonitrile(s) via a 3-component reaction of aryl aldehyde(s), malononitrile and 2-mercaptopyridine in the presence of K2CO3 under solvent free reaction conditions (SFRC) using grinding technique at room temperature in a single step. The advantages of the present protocol is operationally simple, environmentally benign, solvent-free reaction conditions (SFRC), simple work up, excellent isolated yields of desired products and viable method for large scale applications in pharmaceutical industry. Interestingly, the synthesized compounds showed moderate to excellent antibacterial activities against Gram-positive and Gram-negative bacterial strains.