TiO 2 ‐Au NPs Heterojunction Arrays for Sensitive and Specific Detection of Copper Ions

Developing simple and effective methods to detect heavy metals is a research focus in the field of environmental science and materials science. However, the interference in complex matrix is one of the main obstacles when applying those methods to in-field detection. In this work, by anchoring Au nanoparticles (NPs) on TiO2 nanotube arrays (NTAs), a Schottky junction is successfully introduced into a Ti/TiO2/Au/chitosan heterostructure, which shows outstanding performance for sensing copper ions. The high specific surface area of TiO2 NTAs offer numerous binding sites of Au NPs and Cu2+, which increase the density of the nanoscale Schottky junctions and extend the effective detection range of the sensor. The excellent conductivity of Au NPs can reduce the impedance and improve the overall quality of the Schottky junction. Most importantly, two factors are designed to increase the specificity of the sensor: the energy barriers oriented from the Schottky junction and the Cu2+ absorbing layer composed by chitosan. The excellent sensing properties are further confirmed in real-life samples, demonstrating its potential applications in complex scenarios.