Sol-gels doped with polymer-coated ZnS/CdSe quantum dots for the detection of organic vapors

Abstract

A novel luminescent sensing material for the detection and discrimination of different organic vapors has been developed and characterized. For such purpose, colloidal polymer surface-modified ZnS/CdSe semiconductor quantum dots (QDs) were synthesized and trapped into sol–gel inorganic matrices following a simple and friendly procedure. It was observed that the QDs entrapped into the sol–gels maintain invariable optical properties. Moreover, rapid and reversible quenching of the fluorescence from the immobilized QDs upon exposure of the doped sol–gel materials to several organic vapors was observed, with the onset of the quenching process being dependent on the target gas type and on its concentration. After a necessary previous photoactivation, the luminescence of the immobilized quantum dots was found to exhibit a distinct behavior when exposed to different organic vapors at atmospheric pressure. The sensing response from the surface-modified quantum dots was also dependent upon the porous sol–gel matrix composition. Two different active materials were prepared using the same colloidal polymer-coated ZnS/CdSe QDs but changing the composition of the precursors used during the sol–gel preparation and doping process. After exposing the synthesized materials to the different organic analytes gaseous samples, the measured luminescence responses were processed, by multivariate analysis and a dynamic pattern recognition method. Results obtained demonstrated the analytical potential of ZnS/CdSe doped sol–gels as luminescent sensing materials for the rapid detection of organic vapors in contaminated atmospheres.