Synthesis and photocatalytic activity of dumbbell-like mesoporous ZnO micro-nanomaterials with tetrasulfonatomethyl-n-hexyl calix [4]resorcinarene tetrasodium salt as hard-soft template

Abstract

Dumbbell-like ZnO micro-nanomaterials with uniform morphology were prepared with tetrasulfonatomethyl-n-hexyl calix [4]resorcinarene tetrasodium salt (THCRT) by a simple reflux method. The ZnO samples were characterized by X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis, Brunauer-Emmett-Teller technique, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectra, and Photoluminescence. The as-prepared ZnO micro-nanomaterials with a hexagonal wurtzite structure exhibited dumbbell-like morphology with a length of 700–900 nm and a hemisphere diameter of 500–700 nm. The THCRT was involved in the formation of ZnO nanostructure framework during the assembly and stacking of ZnO nanoparticles. The as-obtained dumbbell-like micro-nanomaterials possessed obvious mesoporous structure after the calcination at 500 °C and 650 °C, which is due to the rigid hydrophobic cavity of THCRT as hard template. The effects of the zinc sources, amount of THCRT, surfactants and amount of ammonia on the size and morphology of the ZnO samples were studied. The results indicate that THCRT with multi-head and multi-tail as soft template has a good protective effect on the growth of ZnO crystals. This study shows that the as-prepared ZnO product has a dumbbell-like mesoporous micro-nanostructure due to the special structure of THCRT which consists of rigid cup cavity, hydrophilic heads and hydrophobic tails. The evolution process of the dumbbell-like ZnO micro-nanostructures was investigated by FE-SEM, and a possible formation mechanism was proposed. The as-prepared ZnO micro-nanomaterials exhibited good adsorption capacity without calcination and excellent photocatalytic activity for degradation of methyl violet after calcination. Due to the excellent properties of micro-nanoscale, suitable pore size, high specific surface and good photoabsorption, the as-prepared dumbbell-like mesoporous ZnO micro-nanomaterials exhibit potential application as photocatalyst.