Enhanced Fluorescence from CdTe Quantum Dots Self-Assembled on the Surface of Silver Nanoparticles

Abstract

This paper presents an investigation on the fluorescent properties of semiconductor CdTe quantum dots (QDs) self-assembled on the surface of PVP (polyvinylpyrrolidone)-capped silver nanoparticles (NPs) by the ligand field effect. A significant 2.5-fold enhancement in the integrated fluorescence intensities, red shift of fluorescence peak, and obvious decrease of lifetime were observed in the CdTe QDs assembled on the Ag NPs in comparison with the pure CdTe QDs. The fluorescence enhancement factor and red shift were found to depend on the Ag NP concentration. The fluorescence enhancement was attributed to a highly localized electromagnetic field on the Ag NPs generated by the surface plasma and the change in the surface trap state of the CdTe QDs originating from plasma oscillations in the Ag NPs. It is first proposed that the surface passivation of CdTe QDs is also an important factor for metal-enhanced fluorescence. The surface defects of CdTe QDs can be modified by the Cd-O coordination interaction between the CdTe QDs and PVP molecules, which will cause the trap state density and luminescence lifetime to decrease. The surface passivation of CdTe QDs can also improve fluorescence quantum yield and lead to the red shift of the fluorescence peak. Compared with previous reports, the occurrence of the self-assembly of CdTe QDs on the surface of PVP-capped Ag NPs is fairly simple and easy. From a practical point of view, the combination of CdTe QDs with Ag NPs may lead to the fluorescence enhancement, which could be utilized in a variety of chemical and biological detection applications.

The unique role of nanoparticles in nanomedicine: imaging, drug delivery and therapy

“…268 In addition, a range of different fluorophore based experiments have been conducted including carbon nanotubes, 269 hypericin, 260,261 chlorophyll, 270 phycobiliproteins, 258 RNA, 257 fluorescein-labeled oligonucliotides, 255,256 and recently, a dynamic observation of protein translation has been reported. 271 Interestingly, it has also been reported that PL of QDs at the surface of metallic NPs can also be enhanced, [272][273][274][275] opening up the possibilities for rationally designed plasmonic/QD PL probes with enhanced emission.…”

Ultrafast carrier dynamics in Ag–CdTe hybrid nanostructure: non-radiative and radiative relaxations

“…The excitonic peak in case of Ag-nCdTe colloid also got bleached compared to the bare CdTe QD colloid. Various groups have reported similar changes in the extinction spectrum in metal-semiconductor HNS when compared to that of individuals [18][19][20][21][22] . The increase in the absorption cross-section in the longer wavelength of Ag-nCdTe is attributed to the defect states created by the attachment of Ag NP to CdTe QD.…”

Role of Auger Recombination in Plasmon Controlled Photoluminescence Kinetics in Metal-Semiconductor Hybrid Nanostructures

“…The extinction spectra of the H AgP T colloid looks more like that of CdTe QD but with two modified features, (i) the bleaching of the exciton peak at around 2.21 eV and (ii) band tailing at the lower energy side below 2 eV. Bleaching of exciton peak in the presence of MNP has been attributed to exciton dissociation in the presence of high electric fields 40,41 . On the other hand the band tailing below 2 eV is also observed in several other metal-semiconductor HNS and has been attributed to the formation of additional surface defect states 42 .…”