Nitrogen dioxide sensing characteristics at elevated temperature of sol–gel glass thin films containing substituted porphyrin dyes

Abstract

An optical gas sensor device based on tetra-substituted porphyrin dye entrapped in sol±gel glass displays greatly improved signal strength (1400% at 295 K) on exposure to 4.4 ppm nitrogen dioxide (in N 2 ) gas compared to a multilayer Langmuir±Blodgett ®lm fabricated from the same porphyrin. Temporal response was found to be similar, but differences in the two deposition methods were observed in terms of signal strength and response/recovery times. This behaviour is explained in terms of the differing nature of the two ®lm types. A room temperature sensitivity of 176 ppb was measured and the response obeyed Langmuir adsorption kinetics.

Optical sensing responses of tetraphenyl porphyrins toward alcohol vapours: A comparison between vacuum evaporated and spin-coated thin films

“…In order to quantify the concentration dependence of the response, a number of isotherm models, which describe the adsorption/desorption of the analyte molecules onto the solid surface, can be applied [20]. In particular, the Langmuir adsorption isotherm [21] has been used by a number of workers to characterize their systems [14,22] and provides a preliminary insight into the active process. The linear form of the Langmuir adsorption isotherm is usually expressed by:…”

Chemical Sensors Based on Molecularly Imprinted Sol-Gel Materials

“…Worsfold et al [45] designed NO 2 gas sensors based on sol-gel entrapped prophyrins that were deposited as thin sensitive film on glass substrates. Grant et al [46] employed the sol-gel based fiber optical sensors for monitoring nitrogen dioxide considering two different strategies.…”

Langmuir–Schaefer films of five different free base tetraphenylporphyrins for optical-based gas sensing of NO2

“…Considerable research has been done to investigate the NO 2 -sensing properties of free base porphyrins [1][2][3][4][5][6]. This research has been driven by the need to develop more sensitive, reliable and cost-effective sensors for toxic gases.…”