{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T10:50:00Z","timestamp":1768819800647,"version":"3.49.0"},"reference-count":31,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2015,5,12]],"date-time":"2015-05-12T00:00:00Z","timestamp":1431388800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Ministerio de Econom\u00eda y Competitividad of Spain","award":["TEC2010-21830-C02-01"],"award-info":[{"award-number":["TEC2010-21830-C02-01"]}]},{"DOI":"10.13039\/501100011011","name":"Junta de Andaluc\u00eda","doi-asserted-by":"publisher","award":["FQM-2310"],"award-info":[{"award-number":["FQM-2310"]}],"id":[{"id":"10.13039\/501100011011","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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.<\/jats:p>","DOI":"10.3390\/s150511118","type":"journal-article","created":{"date-parts":[[2015,5,12]],"date-time":"2015-05-12T11:05:31Z","timestamp":1431428731000},"page":"11118-11132","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":37,"title":["Free-Base Carboxyphenyl Porphyrin Films Using a TiO2 Columnar Matrix: Characterization and Application as  NO2 Sensors"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2110-5023","authenticated-orcid":false,"given":"Javier","family":"Roales","sequence":"first","affiliation":[{"name":"Departamento de Sistemas F\u00edsicos, Qu\u00edmicos y Naturales, Universidad Pablo de Olavide,  Ctra. Utrera Km. 1, 41013 Sevilla, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8750-6220","authenticated-orcid":false,"given":"Jos\u00e9","family":"Pedrosa","sequence":"additional","affiliation":[{"name":"Departamento de Sistemas F\u00edsicos, Qu\u00edmicos y Naturales, Universidad Pablo de Olavide,  Ctra. Utrera Km. 1, 41013 Sevilla, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mar\u00eda","family":"Guill\u00e9n","sequence":"additional","affiliation":[{"name":"Departamento de Sistemas F\u00edsicos, Qu\u00edmicos y Naturales, Universidad Pablo de Olavide,  Ctra. Utrera Km. 1, 41013 Sevilla, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"T\u00e2nia","family":"Lopes-Costa","sequence":"additional","affiliation":[{"name":"Departamento de Sistemas F\u00edsicos, Qu\u00edmicos y Naturales, Universidad Pablo de Olavide,  Ctra. Utrera Km. 1, 41013 Sevilla, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pedro","family":"Castillero","sequence":"additional","affiliation":[{"name":"Departamento de Sistemas F\u00edsicos, Qu\u00edmicos y Naturales, Universidad Pablo de Olavide,  Ctra. Utrera Km. 1, 41013 Sevilla, Spain"},{"name":"Instituto de Ciencia de Materiales de Sevilla, Universidad de Sevilla\u2013CSIC, Am\u00e9rico Vespucio 49, 41092 Sevilla, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Angel","family":"Barranco","sequence":"additional","affiliation":[{"name":"Instituto de Ciencia de Materiales de Sevilla, Universidad de Sevilla\u2013CSIC, Am\u00e9rico Vespucio 49, 41092 Sevilla, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6417-1437","authenticated-orcid":false,"given":"Agust\u00edn","family":"Gonz\u00e1lez-Elipe","sequence":"additional","affiliation":[{"name":"Instituto de Ciencia de Materiales de Sevilla, Universidad de Sevilla\u2013CSIC, Am\u00e9rico Vespucio 49, 41092 Sevilla, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2015,5,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"629","DOI":"10.1126\/science.1209688","article-title":"Porphyrin-sensitized solar cells with cobalt (II\/III)-based redox electrolyte exceed 12 percent efficiency","volume":"334","author":"Yella","year":"2011","journal-title":"Science"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"889","DOI":"10.1093\/jnci\/90.12.889","article-title":"Photodynamic therapy","volume":"90","author":"Dougherty","year":"1998","journal-title":"J. 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