In situ synergistic crystallization-induced synthesis of novel Au nanostar-encrusted ZnO mesocrystals with high-quality heterojunctions for high-performance gas sensors

Abstract

The designed synthesis of mesocrystal materials and their advanced heterostructures in a simple, mild and low-cost way is of great significance, for the purpose of exploring their novel properties and large-scale applications. Herein, we report a unique one-pot additive-free route for the facile synthesis of novel strawberry-like Au nanostar/ZnO mesocrystal (Au NS/ZnO MC) heterostructures where Au nanostars were grown in the superficial layer of spherical ZnO mesocrystals. In situ synergistic crystallization of Au nanostars and ZnO mesocrystals accounts for the formation of Au NS/ZnO MC heterostructures with high-quality heterojunctions. The growth mechanism of the Au NS/ZnO MC heterostructures has been proposed on the basis of substantial evidence, which involves two sequential processes with morphology/structure evolution driven by surface energy minimization at two different dimensions. The novel Au NS/ZnO MC heterostructures that integrate Au nanostars and ZnO mesocrystals through high-quality Au–ZnO heterojunctions are expected to possess open architecture, high surface area, good electronic conductivity, and effective charge transfer interfaces, showing promise in a wide range of applications in solar cells, photocatalysis, gas sensors, etc. When employed as a sensing material towards H₂S, the Au NS/ZnO MC electrode exhibits extraordinary performance including high sensitivity (≤5 ppb), high selectivity and low working temperature under stimulating realistic environmental conditions. The superior sensing performance can be ascribed to the synergistic effect that derives from the unique Au NS/ZnO MC heterostructures.