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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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Langmuir adsorption plot for m-TCPP/TiO2 composite films upon exposure to 25, 33, 50 and 100 ppm NO2.
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sensors-15-11118-f009: Langmuir adsorption plot for m-TCPP/TiO2 composite films upon exposure to 25, 33, 50 and 100 ppm NO2.

Mentions: In our case, the plot of c/ΔAbsorbance vs.c fitted a straight line (Figure 9), indicating that the conditions for the Langmuir adsorption model are satisfied. Therefore, and according to the assumptions of this model, it can be concluded that the activation energy of adsorption is the same for all binding sites in the porphyrin film, that there are a fixed number of localized surface sites present on the surface and that NO2 molecules striking a surface site that is already occupied do not adsorb onto that particular site.


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)

Langmuir adsorption plot for m-TCPP/TiO2 composite films upon exposure to 25, 33, 50 and 100 ppm NO2.
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-11118-f009: Langmuir adsorption plot for m-TCPP/TiO2 composite films upon exposure to 25, 33, 50 and 100 ppm NO2.
Mentions: In our case, the plot of c/ΔAbsorbance vs.c fitted a straight line (Figure 9), indicating that the conditions for the Langmuir adsorption model are satisfied. Therefore, and according to the assumptions of this model, it can be concluded that the activation energy of adsorption is the same for all binding sites in the porphyrin film, that there are a fixed number of localized surface sites present on the surface and that NO2 molecules striking a surface site that is already occupied do not adsorb onto that particular site.

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