Exhaled human breath contains thousands of different volatile organic compounds (VOCs) derived from the body's metabolic processes. It is well known that the diabetes patients produce excess amounts of ketones such as acetone. Hence rapid and easy detection of the presence of acetone vapors in the breath of such patients, especially done in a non-invasive way, is of great importance for the early discovery and control of diabetes. The existing non-invasive methods for detecting acetone in the breath of diabetes patients use analytical techniques such as gas chromatography and mass spectrometry, as well as many other highly sensitive methods including electrochemical sensors and devices of the “electronic nose” type. However, their disadvantage is the complexity of the methods and complications of using them for daily monitoring.
In this work we propose a simple method of optical detection of acetone vapors based on color/reflectance change. Acetone-sensitive thin films of poly(vinyl alcohol)-graft-poly(methyl acrylate) with two different copolymer compositions were deposited on a silica substrates by spin-coating of aqueous dispersions. Comprehensive optical characterization of the films has been made and films thickness, refractive index and extinction coefficient were calculated. Sensing properties of the films toward acetone vapors were studied by measuring reflectance spectra before and after exposure to the analyte at room temperature. Maximum reflectance change ∆Rmax was calculated from measured spectra in order to evaluate the reaction of the films. The possibility of using this copolymer as a sensitive element in the design of optical sensors has been demonstrated and discussed.
Acknowledgments: Research equipment of Distributed Research Infrastructure INFRAMAT, part of Bulgarian National Roadmap for Research Infrastructures, supported by Bulgarian Ministry of Education and Science was used in this investigation.
