Photoinduced Enhancement of Photoluminescence of Colloidal II-VI Nanocrystals in Polymer Matrices

Abstract

The environment strongly affects both the fundamental physical properties of semiconductor nanocrystals (NCs) and their functionality. Embedding NCs in polymer matrices is an efficient way to create a desirable NC environment needed for tailoring the NC properties and protecting NCs from adverse environmental factors. Luminescent NCs in optically transparent polymers have been investigated due to their perspective applications in photonics and bio-imaging. Here, we report on the manifestations of photo-induced enhancement of photoluminescence (PL) of aqueous colloidal NCs embedded in water-soluble polymers. Based on the comparison of results obtained on bare and core/shell NCs, NCs of different compounds (CdSe, CdTe, ZnO) as well as different embedding polymers, we conclude on the most probable mechanism of the photoenhancement for these sorts of systems. Contrary to photoenhancement observed earlier as a result of surface photocorrosion, we do not observe any change in peak position and width of the excitonic PL. Therefore, we suggest that the saturation of trap states by accumulated photo-excited charges plays a key role in the observed enhancement of the radiative recombination. This suggestion is supported by the unique temperature dependence of the trap PL band as well as by power-dependent PL measurement.

ZnO and Ag NP-decorated ZnO nanoflowers: green synthesis using Ganoderma lucidum aqueous extract and characterization

“…37,38 The excitonic PL (EPL) is more typical for NPs and polycrystalline lms obtained at higher temperatures, 36,39 while NPs synthesized under mild conditions also showed pronounced EPL in some previous work. 37,40 The spectrum of the as-synthesized ZnO NPs in the present work exhibits distinct bands centered at 460 and 550 nm, and another band is seen as a shoulder at 415 nm (Fig. 4a).…”

“…Raman spectra for sample #1 were measured at different laser powers: 10 4 W cm −2 (curve 1) and 10 5 W cm −2 (curve 2). and excitonic (EPL) 37,40 bands. Therefore, we investigated the inuence of adding DMSO (aer synthesis) on the PL spectrum of the present ZnO NPs.…”

“…Modifying the NP surface is a well-known approach to both modifying the properties of the NPs and clarifying the nature of some properties, particularly the origin of different PL bands. 40,45,46 Dimethyl sulfoxide (DMSO), for instance, a very useful solvent, miscible with water, oen used in biomedical applications and the synthesis of nanoparticles, [47][48][49] was shown to be an efficient stabilizer of the ZnO colloidal NPs, 37,38 ensuring a very high intensity of both surface-related (DPL) 38,45 Fig. 3 XRD patterns (a) and Raman spectra (b) of ZnO NPs synthesized using G. lucidum extract.…”

Temperature-Dependent Excitonic Photoluminescence and Nonlinear Absorption of CdTe Nanocrystal/Polyvinyl Alcohol Films

“…From a technological perspective, many methods have been applied to synthesize CdTe NCs in thin film form, which includes vacuum evaporation, inkjet printing [ 9 ], chemical bath deposition [ 10 ], spin coating, electrodeposition, and ion-track templates [ 11 ]. However, among these methods, the spin coating technique is suitable for the preparation of polymer-capped II-VI group nanofilm, as it is cost-effective and easy to handle for large-area deposition [ 12 ]. The polymer matrix shows no PL, due to its lack of a photoluminescent center.…”

Special Issue “II-VI Semiconductor Nanocrystals and Hybrid Polymer–Nanocrystal Systems”

“…The Special Issue also includes three papers on hybrid organic NC systems. The paper by V. Dzhagan et al [4] investigates in depth the origin of photoluminescence (PL) intensity variation under continuous laser illumination in a polymer-NC film. Several previous experiments reported a wide variety of results on the evolution of PL intensity and line shape over time, indicating that several physical and chemical processes, significantly different between particular studies, take place when NCs are continuously illuminated by laser light.…”