Nanoparticles-shape influenced high-efficient degradation of dyes: Comparative evaluation of nano-cubes vs nano-rods vs nano-spheres

Abstract

Implementation of engineered nanoparticles as efficient catalysts for the degradation of hazardous dyes is being explored drastically. However, with predominant focus on correlating the catalytic activity with nanoparticle size and one particular shape (spheres), but other factors such as shape or morphology that can likely have a significant role in determining the catalytic reactivity remains elusive. In the present study we for the first time comparatively evaluate the influence of nearly uniform size-distributions of gold nanoparticles but with different crystallographic shapes; nano-cubes vs nano-rods vs nano-spheres, imparting overall diverse packing, density, electronic state, surface area and surface chemistry that can essentially determine the catalytic performances, on the catalysis of commonly used organic dyes; Methylene Blue and Safranin O as models. Our results highlighted that shape-influenced surface nano-chemistry had a drastic influence on the dye-degradation efficiencies. Relatively, at constant experimental parameters; nano-cubes possessing multi-flat-faceted surfaces were found to be highly efficient with instant degradation, followed by nano-rods with bilateral flat surface, that took up to 10min for Methylene Blue and 16min for Safranin O, whereas non-flat structured nano-spheres were least catalytic and took up to 90min for Methylene Blue, and showed only partial degradation against Safranin O, even after several hours. Nanoparticles shape assessments, quantitative and qualitative analysis of the dye-degradation, along with kinetic parameters were evaluated based on visual confirmation, capturing images using a digital camera, and advanced physical characterization techniques including UV-Vis Spectroscopy, Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy measurements.