Optochemical HCl gas detection using alkoxy substituted tetraphenylporphyrin-polymer composite films

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

“…The VE plot shows a linear relationship over the first 14 s, while it deviates from linearity at longer times. This behaviour is quite common in thin film organic sensing materials [17][18][19]: the linear region represents a fast surface adsorption, in which EtOH molecules can adhere to the porphyrin binding sites at the surface, whilst the deviation from linearity results from the slow diffusion of the gas molecules into the buried layers of the film. SPIN data are characterized by a slower progress that deviates quite soon from linearity.…”

Growth, characterization and sensing capabilities of 5,10,15,20-meso-tetraphenyl iron (III) porphyrin chloride films obtained by means of a novel plasma-based deposition technique

“…As can be seen, both the samples are characterized by fast responses: nevertheless GDS sample shows shorter response and recovery times than the SPIN one. These data can be explained on the basis of surface absorption and bulk diffusion process which is commonly observed in the interaction between analyte molecules and organic sensing films [39][40][41]: this process assumes that this interaction (and thus the sensing response of the film) is the result of two steps: (i) at first a fast surface absorption in which EtOH molecules can adhere to the porphyrin binding sites at or very near the surface; (ii) the second step consists in the slow diffusion of the gas molecules into the buried layers of the film. From the point of view of the analyte molecules, in fact, the "surface" of such a thin films may not only be confined to the upper edge of the film and it may occur thorough the film rather like the surface of a sponge.…”

Toxic gas detection using porphyrin dispersed polymer composites

“…Optochemical sensing of toxic gases using porphyrin [1][2][3] and phthalocyanine [4] dyes is an attractive technique for its simplicity, high stability and sensitivity. In such sensors, the intensity of the characteristic Soret-and Q-bands located in a visible light region is variable with the protonation/deprotonation reaction at the central nitrogens, i.e., TPPH 2 + 2HCl ⇔ TPPH 4 2+ ·2Cl − .…”

“…So far, many efforts have been made to utilize the porphyrin sensors in the condition of such low toxic gas contents. It was reported that the introduction of electron donating groups to the tetraphenylporphyrin (TPPH 2 ) molecule enhanced its sensitivity, probably due to the increase of the electron density or basicity at the central nitrogens [2,3]. However, the stacking through the -conjugated orbitals frequently causes a split and/or shift of the absorption bands, giving rise to a loss of sensitivity and long-term reproducibility.…”

“…However, the stacking through the -conjugated orbitals frequently causes a split and/or shift of the absorption bands, giving rise to a loss of sensitivity and long-term reproducibility. Thus many porphyrin-dispersed composites have been intensively examined, for example, dispersing them in polymer matrices [2,3] or inorganic sol-gel films [5,6]. In this study, TPPH 2 and its OCH 3 , OH and COOH substituted derivatives were dispersed in an ethylcellulose (EC) matrix to form a porphyrin-polymer composite film.…”