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

Roales J, Pedrosa JM, Guillén MG, Lopes-Costa T, Castillero P, Barranco A, González-Elipe AR - Sensors (Basel) (2015)

Bottom Line: 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.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 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.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Ctra. Utrera Km. 1, 41013 Sevilla, Spain. jroabat@upo.es.

ABSTRACT
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.

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Kinetics of the exposure of MCTPP/TiO2, p-TCPP/TiO2 and m-TCPP/TiO2 composite films to 500 ppm NO2 measured at 447, 445 and 442 nm, respectively.
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sensors-15-11118-f007: Kinetics of the exposure of MCTPP/TiO2, p-TCPP/TiO2 and m-TCPP/TiO2 composite films to 500 ppm NO2 measured at 447, 445 and 442 nm, respectively.

Mentions: The speed of response was analyzed by monitoring the absorbance at one of the wavelengths of maximum change during the exposure of the composite films to 500 ppm NO2 (Figure 7). All porphyrins featured fast changes with similar response shapes. After the signal was stabilized, we proceeded to the recovery phase with N2 while heating the samples, which led to a partial reversibility, as indicated before. To quantify the speed of response, we calculated t50, which is the time taken for the absorbance to reach 50% of its maximum value. The obtained t50 values for MCTPP/TiO2, p-TCPP/TiO2 and m-TCPP/TiO2 composite films were 31, 30 and 33 s, respectively, confirming the fast response of all films.


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

Roales J, Pedrosa JM, Guillén MG, Lopes-Costa T, Castillero P, Barranco A, González-Elipe AR - Sensors (Basel) (2015)

Kinetics of the exposure of MCTPP/TiO2, p-TCPP/TiO2 and m-TCPP/TiO2 composite films to 500 ppm NO2 measured at 447, 445 and 442 nm, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481993&req=5

sensors-15-11118-f007: Kinetics of the exposure of MCTPP/TiO2, p-TCPP/TiO2 and m-TCPP/TiO2 composite films to 500 ppm NO2 measured at 447, 445 and 442 nm, respectively.
Mentions: The speed of response was analyzed by monitoring the absorbance at one of the wavelengths of maximum change during the exposure of the composite films to 500 ppm NO2 (Figure 7). All porphyrins featured fast changes with similar response shapes. After the signal was stabilized, we proceeded to the recovery phase with N2 while heating the samples, which led to a partial reversibility, as indicated before. To quantify the speed of response, we calculated t50, which is the time taken for the absorbance to reach 50% of its maximum value. The obtained t50 values for MCTPP/TiO2, p-TCPP/TiO2 and m-TCPP/TiO2 composite films were 31, 30 and 33 s, respectively, confirming the fast response of all films.

Bottom Line: 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.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 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.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Ctra. Utrera Km. 1, 41013 Sevilla, Spain. jroabat@upo.es.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus