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Published on: January 30, 2015
Active and optically transparent tetracationic porphyrin/TiO(2) composite thin films
Pedro Castillero1, Juan R Sánchez-Valencia, Manuel Cano
1Departamento de Sistemas Fisicos, Quimicos y Naturales, Universidad Pablo de Olavide, Carretera Utrera km 1, E-41013 Sevilla, Spain.
ACS Applied Materials & Interfaces
|April 2, 2010
Summary
Tetracationic porphyrin (TMPyP) molecules were infiltrated into porous TiO(2) thin films. Infiltration efficiency depended on pH, and adsorption followed Langmuir-type isotherms and Elovich-like kinetics.
Area of Science:
- Materials Science
- Nanotechnology
- Physical Chemistry
Background:
- Optically transparent titanium dioxide (TiO(2)) thin films with columnar structures and open pores were fabricated using glancing angle physical vapor deposition (GAPVD).
- The porous nature of the TiO(2) films is crucial for incorporating guest molecules.
- Fluorescent tetracationic porphyrin (TMPyP) molecules are of interest for optical applications.
Purpose of the Study:
- To incorporate TMPyP molecules into TiO(2) thin films.
- To investigate the infiltration efficiency, adsorption kinetics, and molecular state of TMPyP within the TiO(2) matrix.
- To assess the accessibility and responsiveness of the infiltrated TMPyP molecules.
Main Methods:
- Fabrication of porous TiO(2) thin films via GAPVD.
- Estimation of film porosity using water adsorption isotherms and a quartz crystal monitor.
- Infiltration of TMPyP molecules into TiO(2) films by immersion in aqueous solutions at controlled pH.
- Characterization of infiltrated films using UV-vis absorption and fluorescence spectroscopy.
- Assessment of TMPyP accessibility via exposure to acid vapors.
Main Results:
- The infiltration efficiency of TMPyP into TiO(2) films was found to be pH-dependent, increasing at higher pH values, consistent with the point of zero charge (PZC) of oxides.
- The adsorption of TMPyP onto the TiO(2) films followed a Langmuir-type adsorption isotherm.
- The adsorption kinetics were described by an Elovich-like model.
- The optical properties of the infiltrated TMPyP molecules changed upon exposure to acid vapors, indicating their accessibility and reversibility.
Conclusions:
- TMPyP molecules can be successfully incorporated into porous TiO(2) thin films.
- The infiltration process is governed by pH-dependent adsorption obeying Langmuir and Elovich models.
- The infiltrated TMPyP molecules retain their optical responsiveness, demonstrating potential for sensing applications.
