Journal
SENSORS AND ACTUATORS B-CHEMICAL
Volume 108, Issue 1-2, Pages 393-397Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.snb.2004.10.055
Keywords
gas sensor; porphyrin; toxic gases; polymer composite; photo-reflection spectrum
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The optochemical sensing performances of the porphyrin dyes dispersed in ethylcellulose (EC) matrix to toxic gases such as HCl, NO2 and SO2 were examined using a photo-reflection spectrum technique. The intensity of the characteristic Soret- and Q-bands of the porphyrins sensitively changed with the concentration of the gasses. Introducing electron-donating -OCH3 and -OH groups to the phenyl-group in the tetraphenylporphyrin (TPPH2) molecule enhanced the sensitivity and that was in the order of TP(4-OH)(4)PH2 > TP(3,5-OCH3)(4)PH2 > TPPH2 to HCL In contrast, electron-withdrawing -COOH group decreased in the sensitivity. It was interpreted that the electron density at the pyrrole nitrogen increased with the electron-donationing groups. Doping of dioctylphthalate (DOP) as a plasticizer to the porphyrin-EC composites remarkably modified their sensitivity and response behavior. The sensitivity to NO2 was extremely high and sub-ppm level of detection was possible for all the composites. In the case of SO2, the sensitivity was lower than NO2, but the composite of TP(4-OH)(4)PH2 exhibited enough sensitivity to detect the concentration of 0.5 ppm. The sensing performance was strongly dependent on the humidity. (c) 2004 Elsevier B.V. All rights reserved.
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