Enhanced Photoluminescence of Gd3Al4GaO12: Cr3+ by Energy Transfers from Co-Doped Dy3.

LEDs for plant lighting have attracted wide attention and phosphors with good stability and deep-red emission are urgently needed. Novel Cr3+ and Dy3+ co-doped Gd3Al4GaO12 garnet (GAGG) phosphors were successfully prepared through a conventional solid-state reaction. Using blue LEDs, a broadband deep-red emission at 650−850 nm was obtained due to the Cr3+ 4T2 → 4A2 transition. When the Cr3+ concentration was fixed to 0.1 mol, the crystal structure did not change with an increase in the Dy3+ doping concentration. The luminous intensity of the optimized GAGG:0.1Cr3+, 0.01Dy3+ was 1.4 times that of the single-doped GAGG:0.1Cr3+. Due to the energy transfer from Dy3+ to Cr3+, the internal quantum efficiency reached 86.7%. The energy transfer from Dy3+ to Cr3+ can be demonstrated through luminescence spectra and fluorescence decay. The excellent properties of the synthesized phosphor indicate promising applications in the agricultural industry.

YAG:Ce3+ Transparent Ceramic Phosphors Brighten the Next-Generation Laser-Driven Lighting.

Y3 Al5 O12 :Ce3+ (YAG:Ce3+ ) transparent ceramic phosphors (TCPs) are regarded as the most promising luminescent converter for laser-driven (LD) lighting. High-quality YAG:Ce3+ TCPs are still urgent for high efficiency LD lighting devices. YAG:Ce3+ TCPs in a vacuum ambience by using nano-sized raw materials are prepared. Controlling defects by adding nano-sized MgO and SiO2 simultaneously enables a high transmittance nearly 80%. After annealing in air furthermore, the luminous efficiency is enhanced greatly from 106 to 223 lm W-1 , which is the best result reported now for LD lighting. These results demonstrate that the optimizing YAG:Ce3+ TCPs in a fitting strategy will brighten once again in the next-generation LD lighting. Based on scanning electron microscopy (SEM) coupled with a cathodoluminescence system, defects and Ce3+ distributions in grains are identified directly for the first time.

The Enhanced Red Emission and Improved Thermal Stability of CaAlSiN3:Eu2+ Phosphors by Using Nano-EuB6 as Raw Material.

Synthesizing phosphors with high performance is still a necessary work for phosphor-converted white light-emitting diodes (W-LEDs). In this paper, three series of CaAlSiN3:Eu2+ (denoted as CASN:Eu2+) phosphors using Eu2O3, EuN and EuB6 as raw materials respectively are fabricated by under the alloy precursor normal pressure nitridation synthesis condition. We demonstrate that CASN:Eu2+ using nano-EuB6 as raw material shows higher emission intensity than others, which is ascribed to the increment of Eu2+ ionic content entering into the crystal lattice. An improved thermal stability can also be obtained by using nano-EuB6 due to the structurally stable status, which is assigned to the partial substitution of Eu-O (Eu-N) bonds by more covalent Eu-B ones that leads to a higher structural rigidity. In addition, the W-LEDs lamp was fabricated to explore its possible application in W-LEDs based on blue LEDs. Our results indicate that using EuB6 as raw materials can provide an effective way of enhancing the red emission and improving the thermal stability of the CASN:Eu2+ red phosphor.

Energy transfer from CdSe quantum dots to porphyrin via two-photon excitation.

CdSe quantum dots have been used as energy donors to activate meso-tetra (4-sulfonatophenyl) porphine dihydrochloride. Pulses of 130 fs duration at a wavelength of 800 nm are used as the two-photon excitation light source. After excitation, steady-state and time-resolved fluorescence spectra are collected for samples with different ratio between the amount of porphyrins and quantum dots. Decay kinetic curves of CdSe quantum dots with and without porphyrins are well fitted by the biexponential decay curve, which indicates a combination of two components (excitonic and trapping state) in the luminescence behavior of CdSe quantum dots. Relative intensity weights of the excitonic and trapping state, total and nonradiative energy transfer efficiency, average luminescence lifetimes of donors are calculated. The nonradiative transfer mechanism becomes the leading factor as the concentration of acceptors gets higher. It is considered to take place through the channel of trapping states of CdSe quantum dots, which is expressed by the weight change between the fast and slow luminescence components. This deduction presents a new way of raising the energy transfer efficiency by increasing the trapping state proportion of the quantum dots, which can be easily realized by surface modification.

[Study of applying fluorescence spectrum imaging to quantitative assay of proteins in bio-chip].

In the present work, the amount and the activity of the goat anti-human IgG, to bind the human IgG labelled with fluorescein isothiocyanate (FITC), immobilized on silicon surfaces modified with APTES and APTES-Glu, respectively, were studied using the fluorescence spectrum imaging (FSI), the results of which were compared with that of ellipsometry. It is shown that the amount of the human IgG labeled with FITC on APTES-Glu measured using FSI is 2.8 times higher than that on APTES, which is nearly coincident with the 2.2 times obtained using ellipsometry, showing that the activity of the goat anti-human IgG on APTES-Glu is higher than that on APTES. It is reasoned that the FSI is used in the fluorescence immunoassay the for measurement of quasi-quantification or quantification.

Microstructure and environment dependence of 2H11/2 --> 4I15/2 upconversion emission in YVO4:Er3+, Yb3+ nanocrystals.

Upconversion emission of different nanocrystalline YVO4:Er3+, Yb3+ synthesized by a hydrothermal process at low temperature was studied under 980 nm excitation where green [(2H11/2, 4S3/2) --> 4I15/2] and red (4F9/2 --> 4I15/2) emissions demonstrate sensitivity to the local environments of Er3+. Small particle size, high Yb3+ concentration, or high temperature favors the emission of the 2H11/2 --> 4I15/2 transition. Both XRD patterns and Raman spectra have confirmed that crystal lattice distortion of YVO4:Er3+, Yb3+ nanocrystals is more serious when the nanoparticle size is decreasing or Yb3+ concentration is increasing. This distortion is thought to play a key role in the observed spectral properties, which might lead to a new route to improve the monochromatic upconversion emission efficiency in these nanocrystals.

[Surface enhanced Raman spectroscopic study on the gold-labeled protein self-assembled surface].

The human IgG molecules were labeled with 13 nm gold nanoparticles and the complex of the gold-labeled human IgG molecules was immobilized on a silicon surface modified by 3-aminopropyltriethoxysilane and glutaraldehyde. The method increases not only the tightness but also the surface coverage for immobilization of the complex and retains protein configuration well on the silicon surface. The self-assembled complex surface was observed by AFM. The complex aggregated on the silicon surface and the "island" monolayer of the complex was obtained. Meanwhile the SERS spectrum of the complex self-assembled "island" monolayer on silicon surface was presented. In the present paper, the gold labeled human IgG molecules were self-assembled on the silicon surface, SERS spectra of protein were obtained and as SERS active substrates were provided for the study of the protein molecules.