We report photoluminescence-based ozone sensing using composite films composed of gold or platinum and red-emitting CdSe/ZnS core-shell quantum dots. The sensing efficiency of quantum dots is enhanced by the addition of noble metals. The composite films undergo reversible changes in photoluminescence intensity (measured at excitation/emission wavelengths of 365/652-659 nm) in the presence of ppm levels of ozone in air at 25°C and at atmospheric pressure. The sensitivity of the composite films does not saturate with ozone in the 0.5-200 ppm concentration range. When compared with a quantum dot-only film, the composite films show higher sensitivities to 0.5 ppm ozone of 27% (gold) and 43% (platinum). When compared with a quantum dot-only film, the photoluminescence of the gold-or platinum-palladium alloy-based film recovers faster after the removal of ozone in the surrounding atmosphere. Thus, platinum-or gold-conjugated quantum-dot films form sensor modules for the reversible and highly sensitivie detection of ozone under the tested ambient conditions.

We report here a novel, sensitive detection method for nitrogen dioxide (NO 2 ) using thin films of CdSe/ZnS coreshell type quantum dots (QDs) with and without noble metal (NM) nanoparticles (Au, Pt, or Pt-Pd alloy) deposited on a glass substrate. The photoluminescence (PL) intensity of the QD-only film and NM-QD composite films with porous microstructure rapidly decreased on exposure to NO 2 (1100 ppm) in air, and it reversibly recovered after the atmosphere was changed back to air without NO 2 . Interestingly, the Au-QD, Pt-QD, and Pt-Pd-QD films showed higher sensitivity when compared with the QD-only film. The reversible responses of QDonly film, Au-QD film, Pt-QD film, and Pt-Pd-QD film to NO 2 in air suggested that the CdSe/ZnS QD film and NM-QD films could be promising PL-based optical NO 2 sensors. Furthermore, the high NO 2 sensitivity, but low ozone sensitivity, in the Pt-Pd-QD film suggests the possibility of recognizing these two oxidizing gases by using the gas-selective catalytic activity of Pd.

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