Porphyrin Langmuir-Blodgett Thin Film for Organic Vapor Detection

Abstract

The detection of volatile organic compounds (VOC’s) is a very important task due to stringent environmental standards and regulations on VOC’s in many countries. They are highly toxic and may cause metabolic diseases, genetic disorders, acute, chronic or long-term effects and cancer. In order to control the air quality and human health respect to standards and regulations gas sensors are widely used to measure the level of VOCs. The performance of the gas sensing devices mostly depends on the performance of the sensing materials which depends on their chemical structures. Organic materials are widely studied in the field of VOC’s sensor application due to their low cost, physical and chemical properties. Porphyrin molecule was deposited as an Langmuir-Blodgett thin film onto gold substrates for the study of sensor properties using benzene, toluene, ethyl benzene and xylene. Surface plasmon resonance technique was employed for the characterization of these LB films. A high quality and uniform Langmuir monolayer from the water surface can be transferred onto a gold coated substrate with a transfer ratio of over 90%. For the sensing application towards benzene vapor, this LB film yields a fast and almost fully reversible response to benzene in few seconds.