Abstract
A facile hot injection approach to synthesize high-quality non-stoichiometric ZnxAgyInS1.5+x+0.5y nanocrystals (NCs) in the size range of 2.8–3.1 nm was presented. The fluorescence spectra had single band gap features, and indicated the formation of alloy states rather than simple composite structures. The chemical compositions, photoluminescence (PL) emission wavelengths, and quantum yields of ZnxAgyInS1.5+x+0.5y nanocrystals were significantly influenced by the concentration of an organic capping agent. The appropriate proportion of 1-dodecanthiol in the precursor prevented the precipitation, increased the fluorescence quantum yield, and improved their optical properties. The proper ratio of capping agent allowed Zn, Ag, and In to form a better crystallinity and compositional homogeneity of ZnxAgyInS1.5+x+0.5y nanocrystals. The photoluminescence was tunable from blue to red in the range of 450–700 nm as the Ag content changed independently. The PL and absorption spectra of ZnxAgyInS1.5+x+0.5y nanocrystals showed a significant blue shift with the decrease of Ag content in the precursor. As there were no obvious differences on the average particle sizes of ZnxAgyInS1.5+x+0.5y samples, these results fully revealed the composition-dependent photoluminescence properties of ZnxAgyInS1.5+x+0.5y nanocrystals. The relative quantum yield reached 35%. The fluorescence lifetimes (τ1=115–148 ns and τ2=455–483 ns) were analogous to those of AgInS2 and (AgIn)xZn2(1−x)S2.
Highlights
Ternary I-III-VI2 nanocrystals (NCs), including AgInS2 (AIS) and CuInS2 (CIS), have been developed recently to replace the toxic Cd- and Pb-contained NCs as fluorescence label and probes for biomedical and biological investigations [1,2,3,4]
These diffraction peaks were attributed to the (111), (220), and (311) planes [28], respectively. This indicated that the X-ray powder diffraction (XRD) diffraction peaks did not originate from the mixture of AgInS2 and ZnS. These results demonstrated that the ZAIS NCs were not a simple mixture of AgInS2 and ZnS but the compositional homogeneous ZnxAgyInS1.5+x+0.5y solid solution [35]
These results indicated that the ZAIS NCs had monocrystalline structures which coincided with the HRTEM measurements (Figure 1c)
Summary
Ternary I-III-VI2 nanocrystals (NCs), including AgInS2 (AIS) and CuInS2 (CIS), have been developed recently to replace the toxic Cd- and Pb-contained NCs as fluorescence label and probes for biomedical and biological investigations [1,2,3,4]. These semiconductor nanomaterials have many advantages, such as high absorption coefficient, low toxicity, high energy conversion efficiency, and stability to solar radiation [5]. The fluorescence emission peak of AIS is adjustable from visible to near infrared, and it possesses good photostability and large absorption coefficient, making it suitable for lighting and bio-imaging in vivo and in vitro [13,14]
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