Papers by Keyword: Semiconductor Quantum Dots

Abstract: Uniform and well-dispersed photoluminescent semiconductor ZnSe (zinc selenium) QDs (Quantum dots) were in-situ prepared stabilized by G4.0-NH₃⁺ PAMAM(polyamidoamine) dendrimers in methanol. The properties of ZnSe QDs encapsulated in PAMAM dendrimers were characterized by UV-Vis absorption spectra and photoluminescence (PL) emission spectra. The results were: ZnSe/PAMAM NCs (nanocomposites) with molar ratio 15 emitted strongest fluorescence.

Abstract: We here report the temperature effect on photoluminescence(PL) spectra of PbSe quantum dots (QDs), which exhibit a strong temperature dependence on their spectra position and intensity. They potentially act as the temperature marker, sensing temperature variations and reporting temperature changes remotely through optical readout. In addition, the temperature sensitivity characterized by peak position of PbSe QDs was found to be 0.39nm/°C in a range of 10-100 °C.

Abstract: Uniform and well-dispersed photoluminescent semiconductor CdSe(Cadmium selenium) QDs(Quantum dots) were in-situ prepared stabilized by G4.0-NH₂ PAMAM dendrimers in water and effects of metallic ions such as Zn²⁺, Cd²⁺, Cu²⁺, Ag⁺, Pb²⁺, K⁺, Na⁺ on the photoluminescence(PL) properties of CdSe QDs were studied using spectrophotometric titration. The results show that Zn²⁺ and Cd²⁺ ions enhance the PL intensity of CdSe QDs, Cu²⁺, Ag⁺ and Pb²⁺ ions quench the PL intensity, while K⁺ and Na⁺ ions have no obvious effects. Those are attributed to the surface modification of CdSe QDs. Excess Cd²⁺ ions can reduce the non-combination centers, increase the passivation of PAMAM on the surface of CdSe QDs, and form a Schottky-like barrier which enhanced the PL efficiency. Excess Zn²⁺ ions can also increase the PL intensity of CdSe QDs in the same way as Cd²⁺ ions because of the much similar lattice parameters of CdSe and ZnSe. However, a CuSe, Ag₂Se or PbSe shell on CdSe QDs emerges due to the substitution of Cd²⁺ ions, which leads to the decrease of band-edge emmiting of CdSe QDs. And the quenching effect of Ag⁺ is stonger than Cu²⁺ and Pb²⁺ because of the lower solubility of Ag₂Se formed on the surface of CdSe QDs. Oil latent fingerprints deposited on tinfoil surface treated with CdSe/dendrimer NCs(Nanocomposites)、Cd²⁺-CdSe/ PAMAM NCs and Zn²⁺-CdSe /PAMAM NCs emitted bright yellow photoluminescence under ultraviolet excitation of 365nm from an UV LED in the dark., among, fingerprint treated with Cd²⁺-CdSe/dendrimer NCs and Zn²⁺-CdSe /PAMAM NCs was detected with better resolving rate.

Abstract: CdS(Cadmium sulfide)/PAMAM(polyamidoamine) Nanocomposites were in-situ prepared taking PAMAM dendrimers as stabilization in water. The prepared solution containing photoluminescent semiconductor CdS QDs(Quantum dots) was utilized for detection of aged fingermarks on adhesive tape strips. The fingermarks were aged for 1 d, 7 d and 30 d in nature light respectively. The results show that the latent aged fingermarks treated with CdS/PAMAM nanocomposites emit yellow luminescence under ultraviolet excitation of 365 nm in the dark. Aged fingermarks were detected successfully with better resolving rate comparing with existing nano-scale commercial TiO₂ powder suspension.