Jisen Zhang

Ultraviolet upconversion emissions of Gd3

Under 980 nm excitation, upconversion (UC) emissions in the UV range of 270-320 nm were observed in nanocrystals Y(0.795-x)Gd(x)Yb(0.2)Tm(0.005)F(3) (x=0, 0.1, 0.2, 0.5, and 0.795), which were synthesized through a hydrothermal method. These UC emissions can be assigned to the transitions of (6)I(J), (6)P(J)-->(8)S(7/2)(Gd(3+)), and (3)P(0)/(1)I(6)-->(3)H(6) (Tm(3+)). The energy transfer from Tm(3+) to Gd(3+) plays a crucial role in populating the excited states of Gd(3+). The shortest wavelength of upconverted emission converted from the infrared region was demonstrated here.

Ultraviolet upconversion fluorescence from 6 D J of Gd 3+ induced by 980 nm excitation

Ultraviolet upconversion emissions of 246.2 and 252.8 nm from (6)D(J) levels of Gd(3+) ions were observed in GdF(3): 10% Yb(3+), 0.7% Tm(3+) nanocrystals under 980 nm excitation from a laser diode. The (6)D(J) levels of Gd(3+) ions can be efficiently populated by energy transfer processes of Yb-->Tm-->Gd and Yb-->Gd. A six-photon upconversion process was confirmed by the dependence of 252.8 nm emission intensity on the pumping power. The upconversion mechanism in the six-photon process was discussed based on excited state absorption of Gd(3+) ions, cross relaxation energy transfer between two excited Gd(3+) ions, and energy transfer between Gd(3+) and Yb(3+) or Tm(3+) ions.

Synthesis of colloidal LaF3: 0.04Yb3+, 0.01Er3+ nanocrystals with green upconversion luminescence

Abstract A synthesis of LaF 3 0.04Yb 3+ ,0.01Er 3+ nanocrystals with oleic acid as a capping ligand was presented. The X-Ray Diffraction (XRD) pattern indicated that the power was a single hexagonal phase. Transmission Electron Microscopy (TEM) demonstrated that the average size of the nanocrystals was less than 10 nm, with a narrow size distribution. The nanocrystals were dispersible in nonpolar solvents and form a fully transparent colloidal solution, and the solution was stable for several months without any aggregates. The Yb 3+ -Er 3+ codoped nanocrystal colloidal solution exhibited a bright green upconversion fluorescence under 980 nm excitation from a diode laser. The nanocrystals were potentially applicable in biolabeling and bioimaging.

Multicolor up-conversion emissions of Tm3+/Er3+/Yb3+ tri-doped YF3 phosphors.

A new and general approach based on vapor-phase transport technique using Au-coated plant cell walls has been developed to synthesize patterned ZnO nanostructures. Nanowires, nanodendrites and nanotowers were fabricated by adsorption of different metallic ions on plant cell walls. It is shown that plant cell wall can serve as a well-defined template to grow patterned nanostructures. Using transmission electron microscope and Raman spectroscopy, the structural characteristic of the nanostructures were investigated, exhibiting good crystallinity and hexagonal symmetry of the nanomaterials. Quite interestingly, the shape of the nanostructures can be controlled by the metallic ions adsorbed on plant cell walls. Without metallic ions, a homogeneous distribution of nanowires was obtained. On the other hand, with Ni+2 or Fe+3 ions, nanodendrites and nanotowers were observed, respectively. Our approach provides a low cost method that opens up new possibilities for the growth of patterned nanomaterials with desired shapes.