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Highly sensitive free-base-porphyrin-based thin-film optical waveguide sensor for detection of low concentration NO2 gas at ambient temperature

Abudukeremu, Hannikezi, Kari, Nuerguli, Zhang, Yuan, Wang, Jiaming, Nizamidin, Patima, Abliz, Shawket, Yimit, Abliz
Journal of materials science 2018 v.53 no.15 pp. 10822-10834
X-ray diffraction, absorption, ambient temperature, chloroform, coatings, gases, hydrogen sulfide, nitrogen dioxide, porphyrins, scanning electron microscopy, spectral analysis, sulfur dioxide, volatile organic compounds
Meso-5,10,15,20-tetrakis-(4-tertbutyl phenyl) porphyrin was synthesized using Adler–Longo method and was served as sensing material. Electronic absorption spectra of the porphyrin chloroform solution and its thin film were studied comparatively. An optical waveguide sensor based on free-base porphyrin was fabricated by spin coating method. Absorption variation of porphyrin film was studied before and after exposure to NO₂, H₂S, SO₂, and volatile organic gases. XRD patterns of porphyrin film before and after exposure to analytes (NO₂, SO₂, and H₂S) were provided, and light source of the OWG testing system was selected. This facile-prepared sensor exhibited high sensitivity and selectivity to NO₂ with fast response time of 3 s and slow recovery time of 10 min or so and was capable of measuring NO₂ down to 10 ppb at ambient temperature. Scanning electron microscopy was employed to characterize film morphology before and after contact with NO₂. Film thickness was measured before (71.3 nm) and after (76.8 nm) exposure to NO₂, and film thickness variation value (5.20 nm) was calculated. The sensing behavior of the studied sensing device was tested through mixture of H₂S, SO₂, and VOC gases with NO₂ and without NO₂ for determination of the selectivity of the device. Film stability was probed by UV–Vis spectra, and response values of sensing element to NO₂ gas were detected after several days of film preparation, and its RSD value was 1.66%.