Hierarchical ZnO Nanorods With Tailored Surface Defects for Enhanced Acetone Sensing

Abstract

Hierarchical ZnO nanorods were synthesized via mild solvothermal approach followed by calcination at elevated temperatures (i.e. 250 °C and 450 °C) to induce surface defects. The defect induced nanostructures were utilized as resistive devices for low level acetone detection (~10-50 ppm). The porosity and the surface area of ZnO nanorods were seen to increase with increase in calcination temperature as evident from BET results (surface area of 450 °C calcined sample ~55.45 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /g whereas for un-calcined sample ~38.63 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /g). The 450 °C sample exhibited excellent acetone sensing (response ~705% at 20 ppm of acetone) with fast response and recovery time (25 s and 31 s respectively) in comparison to the other samples (i.e. 250 °C and un-calcined). The sensing performance was found to improve with increasing calcination temperature which was due to the formation of oxygen vacancies as evident from photoluminescence spectroscopy (enhancement of peak at ~538 nm). A higher surface area coupled with increased oxygen vacancies was responsible for enhanced sensing performance of the calcined nanostructures. The sensor was found to be repeatable and highly selective toward acetone compared to five other volatile organic compounds. Thus, the defect induced ZnO-based sensor shows potential to develop future commercial acetone sensor.