Photoluminescent properties of ZnO nanorods films used to detect methanol contamination in tequila

Abstract

Zinc oxide (ZnO) nanorod films with thickness of 700 nm were prepared via a chemical bath deposition method using a ZnO seed layer deposited on a silicon substrate by a conventional dip-coating technique. The morphology and structural properties of the obtained ZnO nanorods were characterized by field emission scanning electron microscopy and Raman spectroscopy. Photoluminescence spectroscopy exhibited an intense emission located at 380 nm related to near band edge (NBE) recombination and a yellow emission band at 575 nm attributed to intrinsic defects of ZnO. Changes in intensity of the NBE and yellow emissions were determined through room-temperature photoluminescence measurements of ZnO nanorods films when exposed to vapors of ethanol, methanol and tequila-methanol mixtures respectively. ZnO nanorods based sensors showed rapid response times and moderate recovery times together with good selectivity for methanol and ethanol vapors. For tequila-methanol mixtures samples, the change in photoluminescence intensity of both said emissions of ZnO nanorods presented an opposite behavior in comparison against methanol and ethanol samples. Intensity changes of the NBE emission showed a linear trend depending on the increase in methanol concentration, while the yellow emission intensity presented an exponential trend for concentrations below 50 % of methanol in tequila.