Dongyeon Son

Nanoparticle iron-phosphate anode material for Li-ion battery

Nanoparticle crystalline iron phosphates (FePO4∙2H2O and FePO4) were synthesized using a (CTAB) surfactant as an anode material for Li rechargeable batteries. The electrochemical properties of the nanoparticle iron phosphates were characterized with a voltage window of 2.4–0 V. A variscite orthorhombic FePO4∙2H2O showed a large initial charge capacity of 609mAh∕g. On the other hand, a tridymite triclinic FePO4 exhibited excellent cyclability: the capacity retention up to 30 cycles was ∼80%, from 485 to 375mAh∕g. The iron phosphate anodes exhibited the highest reported capacity, while the cathode LiFePO4 has an ideal capacity of 170mAh∕g.

Synthesis and photoluminescence of Mn-doped zinc sulfide nanoparticles

Mn-doped zinc sulfide nanoparticles were synthesized using a liquid-solid-solution method, as a simple synthetic route for preparing nearly monodispersed nanocrystals with a diameter of 7.3±0.7nm. The influence of doping concentration for optimum luminescence properties was studied with the nonuniform distribution of local strain and the capping effect. The improved photoluminescence properties of the 450°C-annealed samples with 1.0at.% Mn doping are attributed to both the removal of water/organics and the enhanced crystallinity (reduced local strain).

Highly luminescent surface-passivated ZnS:Mn nanoparticles by a simple one-step synthesis

Highly luminescent surface-passivated ZnS:Mn nanoparticles were synthesized straightforwardly by a simple liquid-solid-solution method. Compared to the pristine Mn-doped zinc sulfide nanocrystals (quantum efficiency: ∼19%), the Li-added ZnS:Mn exhibited significantly enhanced luminescence properties (quantum efficiency: ∼43%). The surface passivation was investigated by x-ray photoelectron spectroscopy, transmission electron microscopy, and by the change in the radiative/nonradiative recombination rates. The photoluminescence enhancement is due to the formation of an effective passivation layer induced by lithium, and consequent suppression of the nonradiative recombination transitions.