Effect of synthesis medium on aggregation tendencies of ZnO nanosheets and their superior photocatalytic performance

A simple soft chemical method has been sug- gested for large-scale production of zinc oxide (ZnO) nanosheets at room temperature using two synthesis mediums: aqueous (H2O) and non-aqueous (C2H5OH). In H2O medium, nanosheets interwoven group wise in flower- like structures revealing the strong inter-hydrogen bonding among initially nucleated ZnO nanocrystals, whereas weak hydrogen bonding in C2H5OH medium leads to the for- mation of un-aggregated interwoven’ nanosheets. The growth of ZnO flower-like and interwoven nanosheets proceeded via anisotropic oriented attachment of ZnO nanocrystals. Obtained nanosheets were faceted, possess- ing large surface area, width hundreds of nanometers, and thickness in tens of nanometer, as characterized by scan- ning electron microscopy and transmission electron microscopy. These nanosheets show high sunlight photo- catalytic activity toward the degradation of an organic pollutant ‘methylene blue dye.’ The enhancement in pho- todegradation efficiencies, interwoven sheets 99.94 %, and flower-like nanosheets 79.76 % for 120 min of irradiation is attributed to the surface oxygen vacancies narrowing the band gap as confirmed by photoluminescence spectra, faceted geometry, and large surface area of ZnO nanosheets