CdSe and CdSe/CdS core-shell QDs: New approach for synthesis, investigating optical properties and application in pollutant degradation.

In this work, CdSe quantum dots (QDs) were synthesized by a simple and rapid microwave activated approach using CdSO4 , Na2 SeO3 as precursors and thioglycolic acid (TGA) as capping agent molecule. A novel photochemical approach was introduced for the growth of CdS QDs and this approach was used to grow a CdS shell around CdSe cores for the formation of a CdSe/CdS core-shell structure. The core-shells were structurally verified using X-ray diffraction, transmission electron microscopy and FTIR (Fourier-transform infrared (FTIR)) spectroscopy. The optical properties of the samples were examined by means of UV-Vis and photoluminescence (PL) spectroscopy. It was found that CdS QDs emit a broad band white luminescence between 400 to 700 nm with a peak located at about 510 nm. CdSe QDs emission contained a broad band resulting from trap states between 450 to 800 nm with a peak located at 600 nm. After CdS shell growth, trap states emission was considerably quenched and a near band edge emission was appeared about 480 nm. Optical studies revealed that the core-shell QDs possess strong ultraviolet (UV) - visible light photocatalytic activity. CdSe/CdS core-shell QDs, showed an enhancement in photodegradation of Methyl orange (MO) compared with CdSe QDs.

Abbasi S ，Molaei M ，Karimipour M 《-》

Investigation of biocompatible and protein sensitive highly luminescent quantum dots/nanocrystals of CdSe, CdSe/ZnS and CdSe/CdS.

The size and shape dependent semiconductor quantum dots (0D nanoparticles) with color tunability demonstrating significant influence in a biological system and considered as ideal probes. Here, a non-coordinated colloidal approach was used for the synthesis of CdSe, CdSe/ZnS and CdSe/CdS core-shell quantum dots (QDs) of 3-4nm. The synthesized nanocrystals show a high crystallinity, examined by X-ray diffraction (XRD) and high-resolution electron microscopy (HRTEM). The core-shell semiconductor QDs exhibit stronger photoluminescence (PL) as compared to the core QDs. The strong PL with small full-width half maximum (FWHM) indicates that the prepared QDs have a nearly uniform size distribution and well dispersibility. The quantum yield (QY) of core-shell QDs increases due to the surface passivation. Further, the PL of BSA is quenched strongly by the presence of core-shell QDs and follows the well-known Stern-Volmer (S-V) relation, whereas the PL lifetime does not follow the S-V relation, demonstrating that the observed quenching is predominantly static in nature. Among CdSe core, CdSe/ZnS and CdSe/CdS core-shell QDs, the CdSe/ZnS QDs shows the least cytotoxicity and most biocompatibility. Thus, the prepared core-shell QDs are biocompatible and exhibit strong sensing ability.

Ratnesh RK ，Mehata MS 《-》

Design and synthesis of highly luminescent near-infrared-emitting water-soluble CdTe/CdSe/ZnS core/shell/shell quantum dots.

Zhang W ，Chen G ，Wang J ，Ye BC ，Zhong X ... -  《-》

[Study of water-sol core-shell CdSe/CdS quantum dots].

Teng F ，Tang AW ，Gao YH ，Liang CJ ，Xu Z ，Wang YS ... -  《SPECTROSCOPY AND SPECTRAL ANALYSIS》

Synthesis of ZnSe and ZnSe:Cu quantum dots by a room temperature photochemical (UV-assisted) approach using Na(2) SeO(3) as Se source and investigating optical properties.

In this study, ZnSe and ZnSe:Cu quantum dots (QDs) were synthesized using Na2 SeO3 as the Se source by a rapid and room temperature photochemical (UV-assisted) approach. Thioglycolic acid (TGA) was employed as the capping agent and UV illumination activated the chemical reactions. Synthesized QDs were successfully characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and UV-visible (UV-vis) spectroscopy, Fourier transform-infrared (FT-IR), and energy dispersive X-ray spectroscopy (EDX). XRD analysis demonstrated the cubic zinc blend phase QDs. TEM images indicated that round-shaped particles were formed, most of which had a diameter of about 4 nm. The band gap of the ZnSe QDs was higher than that for ZnSe in bulk. PL spectra indicated an emission with three peaks related to the excitonic, surface trap states and deep level (DL) states. The band gap and QD emission were tunable only by UV illumination time during synthesis. ZnSe:Cu showed green emission due to transition of electrons from the Conduction band (CB) or surface trap states to the 2 T2 acceptor levels of Cu2+ . The emission was increased by increasing the Cu2+ ion concentration, such that the optimal value of PL intensity was obtained for the nominal mole ratio of Cu:Zn 1.5%.

Khafajeh R ，Molaei M ，Karimipour M 《-》