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The success of matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry for the characterization of polymer structures and for the determination of average molecular weights and distributions depends on the use of a proper sample/matrix preparation protocol. This work examines the effect of solvents, particularly solvent mixtures, used to prepare polymer, matrix, and cationization reagent solutions, on MALDI analysis. It is shown that the use of solvent mixtures consisting of polymer solvent does not have a significant effect on the molecular weight determination of polystyrene 7000 and poly(methyl methacrylate) 3750. However, solvent mixtures containing a polymer nonsolvent can affect the signal reproducibility and cause errors in average weight measurement. This solvent effect was further investigated by using confocal laser fluorescence microscopy in conjunction with the use of a fluorescein-labeled polystyrene. It is demonstrated that sample morphology and polymer distribution on the probe can be greatly influenced by the type of solvents used. For sample preparation in MALDI analysis of polymers, it is important to select a solvent system that will allow matrix crystallization to take place prior to polymer precipitation. The use of an excess amount of any polymer nonsolvent should be avoided.

We report a simple biomolecule-assisted synthesis of ZnS nanostructured spheres assembled from ZnS nanocrystals with the controllable crystal phase and morphology. L-Cysteine, a biomolecule, was used as the sulfur source and played a key role in the formation of ZnS nanostructured spheres. ZnS nanostructured spheres assembled from various ZnS nanocrystal building blocks, such as nanosheets, quantum dots, nanorods, and multimorphology nanocrystals, were successfully prepared by this simple method. The crystal phase of ZnS nanostructured spheres could be controlled by introducing ethanolamine or ethanediamine as a surfacemodifying reagent in this synthetic system. The hexagonal ZnS nanocrystals were obtained in mixed solvents of water and ethanolamine at temperature as low as 95 °C. The growth mechanism of the nanostructured spheres assembled from nanorods was proposed. The optical properties of ZnS nanostructured spheres were investigated by ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectra.

Luminescence D 6540 Rapid Synthesis of Highly Luminescent CdTe Nanocrystals in the Aqueous Phase by Microwave Irradiation with Controllable Temperature. -Luminescent CdTe nanocrystals are synthesized by microwave irradiation of aqueous solutions of CdCl2, NaHTe, and HS-(CH2)2-COOH at 100-160°C. The samples are characterized by powder XRD and HRTEM. They exhibit strong pH-independent luminescence ranging from 505 to 733 nm with quantum yields of 40-60%. -(LI, L.; QIAN, H.; REN*, J.; Chem.