UV-Induced Surface Photovoltage and Photoluminescence on n-Si/TiO2/TiO2:Eu for Dual-Channel Sensing of Volatile Organic Compounds

In this work, a novel dual-channel sensing mode, i.e., UV-induced surface photovoltage (SPV) and photoluminescence (PL) on n-type Si/TiO2/Eu3+-doped TiO2 (n-Si/TiO2/TiO2:Eu), was demonstrated for the discrimination of 20 volatile compounds. The SPV signaling in this work employed a laboratory-constructed microvoltammeter with good analytical performances. This device also features wireless communication, portability, along with low cost and power consumption. The SPV and PL pattern of each analyte was distinct, and the hierarchical clustering analysis (HCA) result showed that these 20 volatile species were distinguishable, even for structural isomers. Linear discriminant analysis (LDA) further demonstrated the robustness of this sensor: 180 unknown samples from three groups at concentrations of 15.3, 31.7, and 79.2 mg/L were classified with accuracies of 96.7%, 95.0%, and 100%, respectively. Principal component analysis (PCA) revealed that SPV and PL channels contributed equally to the good discrimination ability due to two distinct sensing mechanisms. This dual-channel sensor was also successfully applied in the discrimination of beverage samples such as liquor, wine, and vinegar.