The quantum-confined Stark effect in single cadmium selenide (CdSe) nanocrystallite quantum dots was studied. The electric field dependence of the single-dot spectrum is characterized by a highly polarizable excited state (∼10 5 cubic angstroms, compared to typical molecular values of order 10 to 100 cubic angstroms), in the presence of randomly oriented local electric fields that change over time. These local fields result in spontaneous spectral diffusion and contribute to ensemble inhomogeneous broadening. Stark shifts of the lowest excited state more than two orders of magnitude larger than the linewidth were observed, suggesting the potential use of these dots in electro-optic modulation devices.

Quantum Confined Stark Effect in Single CdSe Nanocrystallite Quantum Dots

A review on the advancements in phosphor-converted light emitting diodes (pc-LEDs): Phosphor synthesis, device fabrication and characterization

Effect of Yb3+ concentration on upconversion luminescence and temperature sensing behavior in Yb3+/Er3+ co-doped YNbO4 nanoparticles prepared via molten salt route

The electronic structures of zero-dimensional quantum wells are studied with a spherical model in the framework of the effective-mass theory. The mixing effect of the heavy and light holes is taken into account, and the symmetry classification and the energy levels of hole states are obtained. The energies of the donor and acceptor states are calculated. The difference between the shallow-impurity states and the eigenstates for the small semiconductor sphere disappears. The selection rules for the optical transition between the conduction- and valence-band states are obtained. The An =0 selection rule is not followed strictly because of the mixing of the L- and (L +2)-orbital wave functions in the wave functions of the hole states. The exciton binding energies are calculated for the small GaAs spheres. The energy levels of the ZnSe spheres are given as functions of the radius and compared with the experiments.

Electronic structures of zero-dimensional quantum wells

Dual-functional of non-contact thermometry and field emission displays via efficient Bi3+ → Eu3+ energy transfer in emitting-color tunable GdNbO4 phosphors

Nanocrystalline GdNbO4:Tm3+ and GdNbO4:Dy3+ phosphors were prepared through a Pechini-type sol gel process. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD reveals that the samples begin to crystallize at 900 degrees C and the pure GdNbO4 phase can be obtained at 1000 degrees C. FE-SEM images indicate that the GdNbO4:Tm3+ and GdNbO4:Dy3+ samples consist of fine and spherical grains with a size around 30-50 nm. Under the excitation of UV light (264 nm) and low-voltage electron beams (1-3 kV), the GdNbO4:Tm3+ and GdNbO4:Dy3+ phosphors showed the characteristic emissions of Tm3+ (D-1(2) -> H-3(6), H-3(5), H-3(4), and (1)G(4) -> H-3(6) transitions) and Dy3+ (F-4(9/2) -> H-6(15/2) and F-4(9/2) -> H-6(13/2) transitions), respectively. The blue CL of the GdNbO4:Tm3+ phosphor has higher color purity and comparable intensity to the Y2SiO5:Ce3+ commercial product. A single-composition white light emitting in response to near UV and low-voltage electron beam excitation has been realized in GdNbO4:Dy3+ phosphor. The obtained GdNbO4:Tm3+ and GdNbO4:Dy3+ phosphors have potential applications in the areas of near UV white-light-emitting diodes and field emission display devices.

Synthesis and Luminescent Properties of GdNbO4:RE3+ (RE = Tm, Dy) Nanocrystalline Phosphors via the Sol-Gel Process

Nanocrystalline Tb 3+ -doped La 2 0 3 phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field-emission-scanning electron microscopy (FESEM), photoluminescence, cathodoluminescence (CL) spectra, and lifetimes were utilized to characterize the synthesized phosphors. The XRD results revealed that a pure La 2 0 3 phase can be obtained at 700°C. FESEM images indicated that the La 2 O 3 :Tb 3+ phosphors are composed of aggregated spherical particles with sizes ranging from 60 to 100 nm. Under the excitation of UV light and low voltage electron beams (0.5-3 kV), the La 2 O 3 :Tb 3+ phosphors showed the characteristic emissions of Tb 3+ ( 5 D 3,4 - 7 F 6,5,4,3 transitions). The CL colors of La 2 O 3 :Tb 3+ phosphors was tuned from blue to green by changing the doping concentration of Tb 3+ to some extent. The optimum blue CL of La 2 O 3 :Tb 3+ phosphors had better Commission International l'Eclairage (CIE) coordinates and higher emission intensity than those of the commercial product Y 2 SiO 5 :Ce 3+ (blue, product no. 1047, Nichia Kagaku Kogyo Kabushiki, Japan).

Tunable Cathodoluminescence Properties of Tb3 + -Doped La2O3 Nanocrystalline Phosphors

LaInO3:Eu3+ phosphors were prepared by a Pechini sol-gel process X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), diffuse reflectance, photoluminescence, cathodoluminescence spectra, as well as lifetimes were utilized to characterize the synthesized phosphors XRD results reveal that the sample begins to crystallize at 600 degrees C and pure LaInO3 phase can be obtained at 800 degrees C The crystallinity increases upon raising the annealing temperature The FE-SEM images indicate that LaInO3:Eu3+ phosphors are composed of fine and spherical grains around 40-80 nm in size Under the excitation of UV light and low-voltage electron-beams, LaInO3:Eu3+ phosphors show the characteristic emissions of the Eu3+ (D-5(J)-F-7(J) J,J(')=0,1,2,3 transitions) The luminescence colors can be tuned from yellowish warm white to red by changing the doping concentration of Eu3+ to some extent The corresponding luminescence mechanisms have been proposed

Tunable Photoluminescence and Cathodoluminescence Properties of Eu3 + -Doped LaInO3 Nanocrystalline Phosphors

[Cd2(C7H3NO5)2 · 4(H2O)] n · 3nH2O · 0.5n(CH3OH) (1) and [Cd3(C7H2NO5)2 · 10(H2O)] · 2H2O ·0.5CH3OH (2) were synthesized and characterized by X-ray single-crystal diffraction. The crystal structure of 1 reveals that both Cds are seven-coordinate with pentagonal bipyramid geometries. Coordination polyhedra are interlinked into a 1-D chain, further linked by hydrogen bonds into a 3-D network. Complex 2 is a discrete structure, then independent [Cd3(C7H2NO5)2 · 10(H2O)] are linked by hydrogen bonds into a 3-D network. The optical properties of 1 and 2 were investigated with fluorescent spectra; both exhibit strong green luminescence probably originating from π–π* transition of the ligand.

Syntheses, structures, and optical properties of two cadmium complexes with chelidamic acid

The electric field response of lead sulfide (PbS) quantum dots with near-infrared absorption of 1000–1600 nm (corresponding to diameters of 2–5 nm) embedded in a PMMA film has been systematically studied by using electric field modulation spectroscopy. For all PbS quantum dots samples, the electroabsorption spectra across the first and second exciton bands are similar in shape to the second derivative of the absorption spectra, indicating the enhancement of the electric dipole moment following the optical transition to these exciton bands. The analysis of the electroabsorption spectra shows that the dipole moments for both first and second exciton bands increase a little bit with increasing particle size. The quadratic field dependence is observed between the modulated absorption spectrum and the electric field of PbS quantum dots doped in a PMMA film.

Liushui Yan

Papers

Synthesis and Luminescent Properties of GdNbO4:RE3+ (RE = Tm, Dy) Nanocrystalline Phosphors via the Sol-Gel Process

Tunable Cathodoluminescence Properties of Tb3 + -Doped La2O3 Nanocrystalline Phosphors

Tunable Photoluminescence and Cathodoluminescence Properties of Eu3 + -Doped LaInO3 Nanocrystalline Phosphors

Syntheses, structures, and optical properties of two cadmium complexes with chelidamic acid

Electroabsorption Spectra of Lead Sulfide (PbS) Quantum Dots in a Polymer Film