Light regulated heterojunctions with tunable interfacial energy barriers for sensitive and specific detection of copper ions

Abstract

Recently, photoelectrochemical (PEC) sensing based on light-induce electrochemical redox has emerged as a promising technique for trace heavy metal detection, due to its sensitivity and simplicity. However, the interfering species with similar redox potentials impose a challenge when such technique is to applied to complex detection scenarios such as in seawater. In this work, by constructing a three-dimensional Ni/Co3O4/MnO2/chitosan (CS) heterostructure, we propose an alternative PEC method for detecting Cu2+. Instead of relying on redox, this method focuses on utilizing the change of the interfacial energy barriers. When light and the specifically absorbed Cu2+ interact with the heterojunctions, such two factors synergistically lower the energy barriers at the interface through electrostatic interaction, exponentially magnify the sensing signal of Cu2+ without involving redox, thus significantly improve both the sensitivity and specificity. The Ni/Co3O4/MnO2/CS sensor performs well in measuring real-life samples such as seawater, suggesting future applications of in-field detection of Cu2+ pollution.