Optical response of monolayer films of a metal-free sulfonamido-porphyrin

• Author(s): Richardson, T. ; Smith, V. C. ; Johnstone, R. A. W. ; Sobral, A. J. F. N. ; Rocha-Gonsalves, A. M. d'A.
• Date: 1998
• Persistent ID: http://hdl.handle.net/10316/5280
• Origin: Estudo Geral - Universidade de Coimbra
• Subject(s): Chlorine; Porphyrin; Langmuir-Blodgett
• Document Type: Article
• Language: English

Description

The influence of gaseous chlorine on monolayers of metal-free meso-tetra(4-amino sulfonyl)phenylporphyrin is discussed. These films exhibit characteristic intense optical absorption bands in the region 400-700 nm. Upon exposure to chlorine vapour in the concentration range 0.1-10 ppm, the Soret and Q-bands decrease in intensity and new bands at ~455 nm and ~660 nm appear. The rate of response has been measured as a function of deposition surface pressure and gas concentration. Repeated dosing experiments have shown that reversible and reproducible sensing action occurs provided that a threshold concentration is not exceeded. The recovery of the original optical spectrum can be accelerated with moderate heat treatment (60°C for 10 min). Ageing experiments have shown that the basic response of the monolayer is not effected over a time period of at least 5 months. http://www.sciencedirect.com/science/article/B6TW0-3VV0K4W-2D/1/d4a4ed344aa0216ef5d8648dd4c71029