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

A simple soft chemical method has been suggested 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 formation 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, possessing large surface area, width hundreds of nanometers, and thickness in tens of nanometer, as characterized by scanning electron microscopy and transmission electron microscopy. These nanosheets show high sunlight photocatalytic activity toward the degradation of an organic pollutant 'methylene blue dye.' The enhancement in photodegradation 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.