Free-Base Carboxyphenyl Porphyrin Films Using a TiO2 Columnar Matrix: Characterization and Application as NO2 Sensors
AbstractThe anchoring effect on free-base carboxyphenyl porphyrin films using TiO2 microstructured columns as a host matrix and its influence on NO2 sensing have been studied in this work. Three porphyrins have been used: 5-(4-carboxyphenyl)10,15,20-triphenyl-21H,23H-porphyrin (MCTPP); 5,10,15,20-tetrakis(4-carboxyphenyl)-21H,23H-porphyrin (p-TCPP); and 5,10,15,20-tetrakis(3-carboxyphenyl)-21H,23H-porphyrin (m-TCPP). The analysis of UV-Vis spectra of MCTPP/TiO2, p-TCPP/TiO2 and m-TCPP/TiO2 composite films has revealed that m-TCPP/TiO2 films are the most stable, showing less aggregation than the other porphyrins. IR spectroscopy has shown that m-TCPP is bound to TiO2 through its four carboxylic acid groups, while p-TCPP is anchored by only one or two of these groups. MCTPP can only be bound by one carboxylic acid. Consequently, the binding of p-TCPP and MCTPP to the substrate allows them to form aggregates, whereas the more fixed anchoring of m-TCPP reduces this effect. The exposure of MCTPP/TiO2, p-TCPP/TiO2 and m-TCPP/TiO2 films to NO2 has resulted in important changes in their UV-Vis spectra, revealing good sensing capabilities in all cases. The improved stability of films made with m-TCPP suggests this molecule as the best candidate among our set of porphyrins for the fabrication of NO2 sensors. Moreover, their concentration-dependent responses upon exposure to low concentrations of NO2 confirm the potential of m-TCPP as a NO2 sensor. View Full-Text
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Roales, J.; Pedrosa, J.M.; Guillén, M.G.; Lopes-Costa, T.; Castillero, P.; Barranco, A.; González-Elipe, A.R. Free-Base Carboxyphenyl Porphyrin Films Using a TiO2 Columnar Matrix: Characterization and Application as NO2 Sensors. Sensors 2015, 15, 11118-11132.
Roales J, Pedrosa JM, Guillén MG, Lopes-Costa T, Castillero P, Barranco A, González-Elipe AR. Free-Base Carboxyphenyl Porphyrin Films Using a TiO2 Columnar Matrix: Characterization and Application as NO2 Sensors. Sensors. 2015; 15(5):11118-11132.Chicago/Turabian Style
Roales, Javier; Pedrosa, José M.; Guillén, María G.; Lopes-Costa, Tânia; Castillero, Pedro; Barranco, Angel; González-Elipe, Agustín R. 2015. "Free-Base Carboxyphenyl Porphyrin Films Using a TiO2 Columnar Matrix: Characterization and Application as NO2 Sensors." Sensors 15, no. 5: 11118-11132.