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Sensors 2017, 17(1), 24; doi:10.3390/s17010024

Optical Gas Sensing of Ammonia and Amines Based on Protonated Porphyrin/TiO2 Composite Thin Films

1
Instituto de Ciencia de Materiales de Sevilla, CSIC–Universidad de Sevilla, Américo Vespucio 49, Sevilla 41092, Spain
2
Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Ctra. Utrera Km. 1, Sevilla 41013, Spain
*
Author to whom correspondence should be addressed.
Academic Editor: Spas D. Kolev
Received: 15 November 2016 / Revised: 14 December 2016 / Accepted: 20 December 2016 / Published: 23 December 2016
(This article belongs to the Section Chemical Sensors)
View Full-Text   |   Download PDF [3638 KB, uploaded 23 December 2016]   |  

Abstract

Open porous and transparent microcolumnar structures of TiO2 prepared by physical vapour deposition in glancing angle configuration (GLAD-PVD) have been used as host matrices for two different fluorescent cationic porphyrins, 5-(N-methyl 4-pyridyl)-10,15,20-triphenyl porphine chloride (MMPyP) and meso-tetra (N-methyl 4-pyridyl) porphine tetrachloride (TMPyP). The porphyrins have been anchored by electrostatic interactions to the microcolumns by self-assembly through the dip-coating method. These porphyrin/TiO2 composites have been used as gas sensors for ammonia and amines through previous protonation of the porphyrin with HCl followed by subsequent exposure to the basic analyte. UV–vis absorption, emission, and time-resolved spectroscopies have been used to confirm the protonation–deprotonation of the two porphyrins and to follow their spectral changes in the presence of the analytes. The monocationic porphyrin has been found to be more sensible (up to 10 times) than its tetracationic counterpart. This result has been attributed to the different anchoring arrangements of the two porphyrins to the TiO2 surface and their different states of aggregation within the film. Finally, there was an observed decrease of the emission fluorescence intensity in consecutive cycles of exposure and recovery due to the formation of ammonium chloride inside the film. View Full-Text
Keywords: MMPyP; TMPyP; TiO2; GLAD-PVD; optically active composites; ammonia and amine gas sensing; porous thin films MMPyP; TMPyP; TiO2; GLAD-PVD; optically active composites; ammonia and amine gas sensing; porous thin films
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Castillero, P.; Roales, J.; Lopes-Costa, T.; Sánchez-Valencia, J.R.; Barranco, A.; González-Elipe, A.R.; Pedrosa, J.M. Optical Gas Sensing of Ammonia and Amines Based on Protonated Porphyrin/TiO2 Composite Thin Films. Sensors 2017, 17, 24.

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