High-sensitive and stable photonic crystal sensors for visual detection and discrimination of volatile aromatic hydrocarbon vapors

Abstract

Photonic crystals (PCs) are promising as intelligent sensors for detection of volatile organic compounds (VOCs) due to their visual identifiability, room-temperature operability and easy portability. In order to realize high-sensitive and repeated detection of the most hazardous volatile aromatic hydrocarbon vapors, a kind of nanoporous and multilayered organic-inorganic composite PC sensors are designed and prepared via alternate assembly of poly(styrene-acrylic acid) and TiO2 nanoparticles. The structures of the PC sensors are characterized and their optical properties are easily modulated. With a three-stack PC sensor, visual detection of different concentrations of benzene, toluene, xylene and 1,2,4-trimethylbenzene (TMB) vapors is realized and the detection limits of 1,2,4-TMB and xylene can reach 14.7 ppm and 99.2 ppm, respectively. When exposing to toluene gas stream, the sensor quickly generated a reversible shift of over 500 nm within 1.5 s and large red-shifts within several seconds are also achieved upon exposure to the other aromatic vapors. With toluene as an example, a colorimetric analysis program on smartphone is developed and through capturing the color with the program, the concentration value can be facilely obtained. In addition, the PC sensor is also served as visual recognizer for discriminating these aromatic vapors based on their differences in solubility parameters and polarity. With the excellent characteristics, the PCs are promising as high-performance aromatic VOCs sensors for environment quality monitoring.