Reversible sensing of nitrogen dioxide using photoluminescent CdSe/ZnS quantum dots and enhanced response by combination with noble metals

Abstract

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.

Optical Oxygen Sensors Show Reversible Cross-Talk and/or Degradation in the Presence of Nitrogen Dioxide

“…A recent report indicated minor crosssensitivity of an oxygen optode to NO, but the potential influence of NO 2 has not been investigated. 15 Several literature reports document luminescence quenching by NO 2 for some chromophores including a ruthenium(II) complex, 5 metal-free porphyrin, 17 ZnO nanowires, 18 and CdSe/ZnS quantum dots 19 and propose to utilize this process for optical sensing of nitrogen dioxide. Other reported optical sensors for nitrogen dioxide utilize modulation of the energy transfer between linker and metal nodes in a lanthanide metal− organic framework (MOF) leading to luminescence enhancement or quenching, 20 luminescence quenching in another lanthanide MOF via electron exchange with NO 2 acting as an electron acceptor, 21 fluorescence quenching due to disruption of highly emissive J-aggregates in Langmuir−Blodgett films, 22 or reversible absorption changes upon interactions of NO 2 with a porphyrin 23 or osmium(II) tris-bipyridyl complex.…”