Piezo-Triggered Formation of Functional ZnO@Au Interfaces: Toward Instant and Sustainable Interface Engineering

We report an ultra-rapid and sustainable method for the fabrication of metal–semiconductor hybrid interfaces via piezoelectrically-assisted ultrasound activation. A one-minute sonication of zinc oxide (ZnO) nanoflowers in aqueous Au³⁺ solution induces the in situ nucleation of gold nanoparticles (AuNPs), driven by local piezopotentials generated through cavitation. This reagent-free and low-energy process yields tunable surface architectures with AuNPs selectively decorating the ZnO interface, in the absence of external reducing agents, surfactants, light, or heat. Structural and spectroscopic analyses (TEM, XRD, Raman) reveal a controlled modification of both surface and sub-surface regions, confirming interface-level coupling between the semiconductor and the metal phase. The photocatalytic performance of the resulting ZnO@Au hybrids was explored as a proof of interfacial functionality, using two representative redox reactions: selective H₂O₂ generation via a two-step oxygen reduction pathway, and Cr(VI) photoreduction in aqueous solution. In both cases, catalytic activity was strongly dependent on nanoparticle size and interfacial distribution. Scavenger experiments further supported the proposed mechanisms, highlighting the role of AuNPs in facilitating charge separation and enhancing photocatalytic selectivity. The results offer new insights for the design of functional nanointerfaces for catalysis, environmental remediation, and light-driven surface processes.