Surfactant-free synthesis of Ag@TiO₂ and CuO@TiO₂ photocatalyst: a comparative study of their photocatalytic activity for reduction of nitroaromatics in water

Abstract

The reduction of harmful nitroaromatics to useful amino-aromatics have significant opportunities in synthetic chemistry. Here a visible-light-driven eco-friendly method for the selective reduction of aromatic nitro compounds to their corresponding amines in aqueous solution by using Ag@TiO2 and CuO@TiO2 is described. It was observed that both Ag@TiO2 and CuO@TiO2 are photo-catalytically more efficient compared to bare TiO2 and CuO@TiO2 has higher activity over Ag@TiO2 for the said conversion. The structural and morphological characterization of the as-synthesized catalysts has been done with SEM-EDX, TEM, powder XRD, ICP-AES, XPS, Photoluminescence, and UV-vis spectroscopic techniques. The nanocomposites Ag@TiO2 and CuO@TiO2 exhibit pure anatase phase with average crystallite size of 5.89 nm and 5.87 nm respectively as calculated from the Debye-Scherrer equation depending on the (101) plane. UV-visible results inferred enhanced optical properties of both the synthesized catalysts and revealed a reduced band gap (3.07 eV for Ag@ TiO2 and 2.5 eV for CuO@ TiO2) as compared to neat TiO2 (3.36 eV). Various nitro compounds were tolerated under 150 W LED as a light source (13.9 lumens for an area of 0.2 ft2) in an aqueous medium at room temperature (30℃) using NaBH4 as a reducing agent to access corresponding amines in satisfying yields (78-99%). The catalyst can be separated from the reaction mixture by simple centrifugal precipitation and reused for up to six consecutive cycles without apparent loss of its catalytic activity. The products were characterized by 1H-NMR spectroscopic techniques and compared with authentic samples.

A novel functionalized CuTi hybrid nanocomposites: facile one-pot mycosynthesis, characterization, antimicrobial, antibiofilm, antifouling and wastewater disinfection performance

“…As referred previously by [ 73 ], UV–Vis spectroscopy could easily give insinuation about the signal architecture of any binary or hybrid nanomaterials, wherein, the presence of single SPR peak at an intermediate location between the SPR of the two metals indicates a randomly organized hybrid metal/metal oxides. In this sense [ 36 ], found that the phyto- synthesized CuO-TiO 2 -NCs displayed their characteristic absorption band at 301 nm; however [ 74 ] and [ 75 ], detected an absorption peak of chemically synthesized CuO‐TiO 2 -NCs at 380 and 363 nm, respectively,. Such variations in results could be attributed to the differences in particle surface properties (e.g.…”