Abstract
The sensing behavior of a thin film composed of metal-free 5, 10, 15, 20-tetrakis (p-hydroxy phenyl) porphyrin and zinc phthalocyanine complex towards m-xylene, styrene, and HCl vapors in a homemade planar optical waveguide (POWG), was studied at room temperature. The thin film was deposited on the surface of potassium ion-exchanged glass substrate, using vacuum spin-coating method, and a semiconductor laser light (532 nm) as the guiding light. Opto-chemical changes of the film exposing with hydrochloric gas, m-xylene, and styrene vapor, were analyzed firstly with UV-Vis spectroscopy. The fabricated POWG shows good correlation between gas exposure response and absorbance change within the gas concentration range 10–1500 ppm. The limit of detection calculated from the logarithmic calibration curve was proved to be 11.47, 21.08, and 14.07 ppm, for HCl gas, m-xylene, and styrene vapors, respectively. It is interesting to find that the film can be recovered to the initial state with trimethylamine vapors after m-xylene, styrene exposures as well as HCl exposure. The gas-film interaction mechanism was discussed considering protonation and π-π stacking with planar aromatic analyte molecules.
Highlights
Accepted: 18 June 2021Aromatic organic solvents such as m-xylene, styrene are common chemicals in almost every chemistry laboratory, while exposure to these solvents or their vapors causes health issues such as insomnia, damage to the neurological system, respiratory system, liver, and kidney
Different materials are reported in the literature for the detection of aromatic compounds and hydrochloric acid (HCl), for example, V2 O5 doped ZnFe2 O4 composited thin film was used to detect xylene and styrene at room temperature using optical waveguide [3], pentacene-based organic field-effect transistor (FET) was applied to detect HCl [4], terbium-based metal-organic frameworks (MOF) to detect styrene through fluorescence mechanism [5]
Composite sensors of poly(styrene-acrylic acid) with TiO2 nanoparticles [6] and MOF/polymer-based photonic crystal [7] were applied for the detection of volatile aromatic hydrocarbon vapors
Summary
Aromatic organic solvents such as m-xylene, styrene are common chemicals in almost every chemistry laboratory, while exposure to these solvents or their vapors causes health issues such as insomnia, damage to the neurological system, respiratory system, liver, and kidney. The analyte detection by POWG sensors has several advantages with respect to other sensor materials: high potential sensitivity, fast response and recovery times, ability to work at room temperature, anti-electromagnetic interference, remote monitoring, safe detection, simple structure with easy manufacturing, and important, low production costs [11,12] In this contest, optical waveguides composed of metal-oxides, organic dyes, or carbon nanomaterials are promising methods for gas exposure detection due to the optical and chemical changes within the sensing layer [9]. 3 ofZn17 phthalocyanine dyes deposited on potassium ion-exchanged glass substrate was reported In this application, a UV-Vis spectrophotometer was used to investigate the sensing behavior of HCl gas, m-xylene, and styrene vapor at room temperature. To explore the absorption behavior of the film interacting with various amounts of vapors within 300–800 nm range at room temperature
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