Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Ctra. Utrera Km. 1, 41013 Sevilla, Spain.
ACS Appl Mater Interfaces. 2012 Oct 24;4(10):5147-54. doi: 10.1021/am3010169. Epub 2012 Sep 28.
In this work, the carboxylic acid derivatives of a free-base porphyrin, 5,10,15,20-tetrakis(4-carboxyphenyl)-21H,23H-porphyrin, and 10 of its metal derivatives (TCPPs) have been used for optical gas sensing. For this purpose, microstructured columnar TiO(2) thin films prepared by GAPVD (glancing angle physical vapor deposition) have been used as host materials for the porphyrins as they are non-dispersive and porous, allowing their use for UV-visible spectroscopy and gas sensing. The chemical binding between the dye molecules and the TiO(2) has been studied through infrared spectroscopy, and the obtained spectral changes have been found to be compatible with chelating and/or bidentate binding modes of the carboxylate groups on the TiO(2) surface. When hosted in the film, the UV-visible spectra of the porphyrins featured a blue shift and broadening of the Soret band with respect to the solution, which has been attributed to the formation of π-π aggregates between porphyrin molecules. The composite porphyrin/TiO(2) films obtained from each of the 11 porphyrins have been exposed to 12 different volatile organic compounds (VOCs), and their respective gas-sensitive properties have been analyzed as a function of the spectral changes in their Soret band region in the presence of the analytes. The set of composite films has shown high selectivity to the analyzed volatile compounds. For each analyte, an innovative way of showing the different responses has been developed. By means of this procedure, an imagelike recognition pattern has been obtained, which allows an easy identification of every compound. The kinetics of the exposure to several analytes showed a fast, reversible and reproducible response, with response times of a few seconds, which has been attributed to both the sensitivity of the porphyrins and the high porosity of the TiO(2) films. Also, increasing concentrations of the analytes resulted in an increase in the magnitude of the response, indicating that the sensor behavior is also concentration-dependent.
在这项工作中，使用了自由碱基卟啉 5,10,15,20-四（4-羧基苯基）-21H,23H-卟啉及其 10 种金属衍生物（TCPPs）的羧酸衍生物进行光学气体传感。为此，使用 GAPVD（掠角物理气相沉积）制备的微结构柱状 TiO2 薄膜作为卟啉的主体材料，因为它们是非分散和多孔的，允许它们用于紫外可见光谱和气体传感。通过红外光谱研究了染料分子与 TiO2 之间的化学结合，并且发现获得的光谱变化与 TiO2 表面上的羧酸盐的螯合和/或双齿结合模式兼容。当在薄膜中承载时，与溶液相比，卟啉的紫外可见光谱显示出 Soret 带的蓝移和展宽，这归因于卟啉分子之间形成了π-π聚集。从 11 种卟啉中的每一种获得的复合卟啉/TiO2 薄膜暴露于 12 种不同的挥发性有机化合物（VOCs），并分析了它们各自的气体敏感性质，作为存在分析物时其 Soret 带区域光谱变化的函数。该组复合膜对分析的挥发性化合物表现出高选择性。对于每种分析物，已经开发了一种新颖的显示不同响应的方式。通过这种程序，获得了类似图像的识别模式，使得可以轻松识别每个化合物。对几种分析物的暴露动力学显示出快速，可逆和可重复的响应，响应时间为几秒钟，这归因于卟啉的敏感性和 TiO2 薄膜的高多孔性。此外，分析物浓度的增加导致响应幅度的增加，表明传感器行为也与浓度有关。
