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Heterogeneous nucleation is a frequently encountered phenomenon in the crystallization of inorganic nanoparticle/polymer systems, and has a great influence on the morphology and properties (such as optical, mechanical and degradable properties) of the nanocomposites. In this study, a solution casting method was adopted to fabricate CdSe–ZnS quantum dots (QDs)/poly(lactic acid) (PLA) nanocomposites films of various QDs concentrations by using chloroform as the solvent. Fourier transform infrared (FT-IR) spectroscopy, polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffractometry (XRD) were used to characterize the crystallization behavior of the nanocomposites films that had been thermally treated differently from the as-cast state. The FT-IR and POM results showed that the nucleation density and the crystallization ability of PLA are greatly enhanced with addition of the QDs in the processes of isothermal crystallization at 403 K. The results of DSC revealed that the glass transition temperature of PLA has no obvious change with the addition of QDs. For the QDs/PLA samples which were isothermally annealed at 403 K for 30 min, the degree of (melt) crystallinity increased with increase of QD concentrations in the PLA matrix. All the results obtained from FT-IR spectroscopy, POM, DSC, and XRD were consistent, suggesting that the CdSe–ZnS QDs can serve as an efficient heterogeneous nucleating agent for the acceleration and enhancement of the melt crystallization of PLA at the optimized condition. [ABSTRACT FROM AUTHOR]

Abstract: A one-pot method was used to prepare poly(vinyl alcohol) (PVA)/ZnO quantum dots (QDs) nanocomposites. In this method, separation and purification of ZnO QDs is not required. The optical properties of the ZnO QDs and PVA/ZnO QDs nanocomposites were characterized by UV–vis spectrophotometry and photoluminescence (PL). X-ray diffraction (XRD), transmission electron microscopy (TEM) and FT-IR spectrophotometry were used to characterize the morphology and structure of the nanocomposites. TEM imaging confirmed that QDs of around 4nm diameter were uniformly dispersed in the PVA matrix. The PL spectra of the PVA/ZnO QDs nanocomposites showed a blue shift as compared with the ZnO QDs solution, while the thermal stability of the PVA was sharply enhanced after the addition of the ZnO QDs. The results confirmed that PVA/ZnO QDs nanocomposites with strong fluorescence emission can be easily prepared by the one-pot method, with good potential for applications in the fields of photoelectricity and display. [Copyright &y& Elsevier]

Abstract: In this study, cadmium selenide/zinc sulfide (CdSe/ZnS) quantum dots (QDs) were introduced into poly(lactic acid) (PLA) for fabrication of photoluminescent PLA/QDs scaffolds. TEM images revealed that the QDs were uniformly dispersed in the PLA. Compressive modulus and thermal stability of the PLA/QDs scaffolds are higher than those of the unfilled PLA scaffold. Cytotoxicity test results confirmed the non-cytotoxicity of the PLA/QDs scaffolds. During the process of in vitro degradation, the degradation rate of the PLA was accelerated by the presence of the QDs, and the molecular weight distributions of the PLA/QDs scaffolds were much broader when compared with the unfilled PLA ones. During the first 84weeks of the degradation process, the photoluminescence (PL) intensity of the PLA/QDs scaffolds decreased with almost the same degradation ratio. The results suggested that the CdSe/ZnS QDs have potential applications for monitoring in vivo degradation of tissue engineering scaffolds. [Copyright &y& Elsevier]