Free-Base Carboxyphenyl Porphyrin Films Using a TiO2 Columnar Matrix: Characterization and Application as NO2 Sensors

Sensors

Javier Roales²  José M. Pedrosa²  Mar໚ G. Guillén²  Tânia Lopes-Costa²  Pedro Castillero²  Angel Barranco¹  Agustín R. González-Elipe¹ 

[1] Instituto de Ciencia de Materiales de Sevilla, Universidad de Sevilla–CSIC, Américo Vespucio 49, 41092 Sevilla, Spain; E-Mails:;Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Ctra. Utrera Km. 1, 41013 Sevilla, Spain; E-Mails:

关键词: carboxyphenyl porphyrin;    microstructured TiO₂ film;    NO₂;    optical gas sensor;    thin film;   

DOI  :  10.3390/s150511118

来源: mdpi

【 摘 要 】

The 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.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.