Monitoring the impact of ionizing radiation on CdSe/ZnS semiconductor quantum dot photoluminescence

Abstract

The impact of 60Co gamma irradiation on the photoluminescent properties of surface passivated CdSe/ZnS semiconductor quantum dots (QDs) in toluene are investigated. Two sets of triplicate samples of the quantum dots in toluene were subjected to increasing absorbed doses of gamma radiation from a 60Co source. One set of samples was prepared with zero (0% volume) headspace. The other set was prepared with appreciable (90% volume) headspace to investigate the impact of air on the QD-gamma ray interaction. Samples were exposed to radiation for periods of 1, 5, 15, 30, or 45 min, producing radiation doses of 0.03, 0.15, 0.45, 1.02, or 1.55 kilo-gray (kGy). Monitoring the impact of gamma irradiation on CdSe/ZnS QDs using wavelength- and frequency-resolved fluorescence decay measurements allows construction of reaction progress Fourier-transform emission-decay matrices (RP-FT-EDMs), which can be analyzed numerically for the evolution of the spectra, decays, and relative intensities of the photoluminescent QD components during gamma irradiation. Analysis of the photoluminescence data shows that the QD emission is composed of three components that change with increasing gamma ray exposure: two quantum dot components that degrade with 0.45 kGy exposure dose; and one component that is associated with particle aggregation and is promoted by exposure in the zero headspace samples. The results also show that QD degradation is accelerated in the samples that have appreciable headspace. Dynamic light scattering measurements corroborated the disruption of the smaller QDs and formation of larger particles observed in the fluorescence measurements after gamma radiation, however, it did not reveal the QD heterogeneity observed in the fluorescence of unirradiated samples.