We described a method for the rapid synthesis of uni- form silver nanoparticles （NPs） under microwave heating, using poly（ethylene glycol） （PEG） as reducing agent and solvent and poly（vinylpyrrolidinone） （PVP） as capping agent. The transmis- sion electron microscopy （TEM） and UV-Vis extinction spectra were used to characterize the size and uniformity of the silver NPs. At the same reaction temperature, the products with microwave heating were more uniform than that with oil heating. We also investigated the influence of reaction temperature, microwave power, and molar ratio of PVP to AgNO3. In our experiments, uniform silver NPs with mean diameter of 50 nm were synthesized at 140 ℃ under 700 W microwave irradiation with PVP/AgNO3 molar ratio of 5 ： 1.
The concentration dependence of the fluorescence spectra and lifetimes of chlorophyll𝑏and sodium magnesium chlorophyllin are compared to explore the influences of intramolecular relaxation and intermolecular interaction of chlorophylls on the fluorescence dynamics.With different concentrations of chlorophyll𝑏and sodium magnesium chlorophyllin in the suspensions,three different fluorescence emission bands are observed.Intermolecular inter-actions increase as the concentrations increase,which lead to redshifts in both fluorescence and lifetime spectra.Additionally,the lifetime is increased by re-absorption in the sodium magnesium chlorophyllin suspensions.These observations increase the understanding of the light harvesting and energy relaxation mechanisms of chlorophyll molecules.
WANG Ya-LanZHOU Zhang-KaiPENG Xiao-NiuZHOU LiHAO Zhong-HuaWANG Qu-Quan
Cadmium sulfide （CdS） nanowires were synthesized on Cd foil via a simple solvothermal reaction at 180℃ using thiosemicarbazide as the sulfide source and ethylenediamine as the solvent. The CdS nanowires are hexagonal-phase single crystals with an average diameter of 50 nm and length of several microns. The as-prepared CdS nanowires show an absorption peak of around 483 nm in the absorption spectrum. The CdS nanowires exhibit bright photoluminescence （PL） with two distinct emission bands at 503 nm and 697 nm, which shows that the as-prepared CdS nanowires are high-quality nanocrystals.
