Development of a simple cataluminescence sensor system for detecting and discriminating volatile organic compounds at different concentrations.

The detection and identification of volatile organic compounds (VOCs) is one of the most serious subjects in the field of chemical sensing, but it remains an enormous challenge. Usually, during the sensing of gases involved in chemical reactions, the residual gas of that reaction (including undecomposed analytes and reaction products) are considered waste gases and released into the air. Here, a novel cataluminescence (CTL) sensing method based on detection of the luminescent intensities of both the analyte (I(A)) and its products (I(R)) was developed and used to identify VOCs at different concentrations. After the analyte gas passed through the first sensing material, the product gas was treated as a new reactant and passed through the second sensing material (which could be the same as or different from the first material). The luminescent signals of I(A) and I(R) were recorded over a short period of time using one photomultiplier. We found the ratio of I(A) to I(R) (I(A)/I(R)) to be a unique characteristic of a given analyte within a wide range of concentrations. To illustrate the new method, 11 kinds of organic gases were successfully identified using I(A)/I(R) values. The most distinct feature of this method is that it allows the user to obtain many more luminescent signals from the sensing materials than common methods. It does so by allowing different flow channels of the analyte gas. This simple method here was used to discriminate different species, homologous series, and isomers in different concentrations. This method could be applied to chemical sensing arrays to increase the discrimination ability or decrease the number of sensing units required.