Study on the diffusion mechanism of graphene grown on copper pockets.

A correlation between graphene domains grown on the outer and the inner surfaces of Cu pockets is found, which discloses a new graphene growth mechanism based on the fast diffusion of carbon atoms through the 25 micro-meter-thick Cu foil, confirmed by isotopic labeling. Subsequently, on the outer surface of the Cu pocket, bilayer graphene with a coverage of about 78% is grown.

Ultraviolet-blue to near-infrared downconversion of Nd(3+)-Yb(3+) couple.

To reduce energy losses by thermalization of charge carriers in a silicon solar cell, quantum-cutting luminescent materials are desired for the efficient downconversion of UV-visible radiation into near-IR radiation. In this Letter, quantum cutting involving emission of two near-IR photons for each UV-blue photon absorbed is demonstrated in Nd(3+)/Yb(3+):beta-YF(3) nanocrystals embedded in transparent bulk-glass ceramics. Upon excitation of an Nd(3+) ion with a UV-blue photon, Yb(3+) ions emit two near-IR photons through an efficient two-step energy transfer from Nd(3+) to Yb(3+) with Nd(3+):(4)F(3/2) acting as the intermediate state.

Color-tunable luminescence for Bi3+/Ln3+:YVO4 (Ln = Eu, Sm, Dy, Ho) nanophosphors excitable by near-ultraviolet light.

Bi(3+)/Ln(3+):YVO(4) nanocrystals with a mean size of 6 nm are prepared through a mixed solvothermal route. With Bi(3+) doping, the excitation band corresponding to the Ln(3+) emission is shifted from 280 nm to 345 nm, owing to the occurrence of Bi(3+) --> V(5+) metal-metal charge transfer and the subsequent energy transfer to Ln(3+) ions. Under near-ultraviolet excitation, the emission color of Bi(3+)/Ln(3+):YVO(4) nanophosphors can be easily tuned by changing the Ln(3+) ions.

CeF3-based glass ceramic: a potential luminescent host for white-light-emitting diode.

Rare earth (RE) ion doped glass ceramics containing hexagonal CeF(3) nanocrystals with a mean size of 12 nm were fabricated. Using Eu(3+) as the structural probe, Stark splitting emissions and the low forced electric dipole D5(0)-->F7(2) transition of Eu(3+) revealed the partition of RE ions into low-phonon-energy CeF(3) nanocrystals. Efficient energy transfers from Ce(3+) to Tb(3+) or Dy(3+) were found, and the energy transfer efficiency was evaluated. Under ultraviolet excitation, intense white-light emission was observed in Dy(3+)-doped samples owing to Dy(3+) resided in CeF(3) crystalline environment, indicating their potential application in white-light-emitting diodes.