Nanostructure-Based Solution Sensor Fabricated with p-CuOx/n-TiO2 Nanojunctions To Identify Species and Concentrations of Alcohol Molecules.

Abstract

Chemiresistive sensors fabricated based on metal-oxide-semiconductors, the most widely used high-sensitivity sensor materials, are required for detecting target solutions and gases and identifying them with a high degree of accuracy. In this study, we used p-n nanojunctions and nanowire shapes for identifying alcohol solutions. The solution sensors fabricated based on CuOx nanowires with p-CuOx/n-TiO2 nanojunctions detected ethanol, ethylene glycol, and diethylene glycol solutions via DC voltage and electrochemical impedance measurements. The p-n nanojunctions affected the sensors' sensitivity in the diethylene glycol solution, and the nanowire surface areas affected the relaxation time in ethanol and ethylene glycol solutions. To identify alcohol solutions, principal component analysis was performed based on the relationship between the sensor information, such as the presence of p-n nanojunctions and nanowire surface areas, and the sensing performance. This analysis identified alcohol molecular species and predicted alcohol-solution concentrations in the 0.1-20 vol % range with a high degree of accuracy. The concept of using sensors with different surface conditions with respect to p-n nanojunctions and nanowire surface areas offers designs for metal-oxide-semiconductor sensors to identify various molecules in solution.