Qingyan Han

Enhanced red upconversion luminescence by codoping Ce3+ in β-NaY(Gd0.4)F4:Yb3+/Ho3+ nanocrystals

In this work, hexagonal phase NaY(Gd0.4)F4:Yb3+/Ho3+ nanocrystals were obtained by solvothermal method. The upconversion emission tuning from green to red in NaY(Gd0.4)F4:Yb3+/Ho3+ nanocrystals was successfully achieved by replacing Y3+ ions in the nanocrystal structure with Ce3+ ions under 980 nm excitation. The red upconversion emission intensity was enhanced with Ce3+ concentration increasing. The output colors for the samples can be clearly observed in a confocal microscopy setup. It was found that two efficient cross-relaxation processes between Ho3+ and Ce3+ ions had been employed to enhance red emission and suppress green emission. The possible upconversion mechanisms and conversion efficiency between Ho3+ and Ce3+ ions were investigated in detail. In addition, the influence of the matrix and surface properties on the upconversion emission of the samples was also discussed. The red upconversion emission of Yb3+, Ho3+ and Gd3+ codoped nanocrystals in this work will have great potential applications in biological imaging, magnetic resonance imaging agents, and display and anti-counterfeiting applications.

Higher Order Fano Resonances and Electric Field Enhancements in Disk-Ring Plasmonic Nanostructures with Double Symmetry Breaking

Optical properties of disk-ring plasmonic nanostructures with double symmetry breaking are investigated theoretically. Tunable higher order Fano resonance is achieved, and it is sensitive to the degree of asymmetry of the nanoring, the offset and the dimension of the nanodisk. It is demonstrated that such higher order Fano resonances originate from the destructive interference between the bright mode of the displaced nanodisk and the dark mode of the asymmetric nanoring. By tunning the asymmetry degree of the nanoring, the offset, and the dimension of the nanodisk, certain higher order Fano resonances can be suppressed or enhanced. Double asymmetry breaking also allows the realization of the stronger electric field enhancement, resulting from the stronger interaction between the displaced nanodisk and the asymmetric nanoring.

Facile fabrication and upconversion luminescence enhancement of LaF3:Yb3+/Ln3+@SiO2 (Ln=Er, Tm) nanostructures decorated with Ag nanoparticles

A novel hybrid nanostructure, that is a Ag nanoparticle decorated LaF(3):Yb(3+)/Ln(3+)@SiO(2) nanosphere (Ln=Er, Tm), was constructed by a facile strategy, and characterized by XRD, TEM, FTIR, XPS and UV-vis-NIR absorption. Obvious spectral broadening and red-shift on the surface plasmon resonance were obtained by adjusting the size and configuration of Ag nanoparticles. Effective upconversion luminescence enhancements for Er(3+) and Tm(3+) containing samples were obtained. It is suggested that the luminescence enhancement results from both the excitation and emission processes, and the configuration of the studied hybrid nanostructure is an efficient system to enhance the luminescence emission of rare earth doped nanomaterials. It is believed that the enhancement from the hybrid nanostructure will find great potential in the development of photovoltaic solar cells.

Unique adjustable UC luminescence pattern and directional radiation of peculiar-shaped NaYF 4 : Yb 3+ /Er 3+ microcrystal particle

A new design of peculiar-shaped β-NaYF4: 20% Yb3+/2% Er3+ hexagonal microcrystal (PSβHM) is proposed and its upconversion (UC) luminescence with adjustable color pattern is studied with near infrared excitation. Flower-like green UC luminescence emission pattern from blooming to withering process and intensive directional red emission are achieved by simply adjusting the focal point position of the excitation light. The mechanism that determines the unique UC luminescence phenomena are investigated systematically. The function of the internal light reflection and waveguide effect with annular microcavity is explored based on the structure characteristic of the hexagonal microplate. The current work may have great significant and potential applications in the development of optoelectronic device, color display, directional light and laser emission of microsystem.

Investigation on Optical Properties of Ag–Au Alloy Nanoparticles

The outstanding chemical stability of Au and intense localized surface plasmon resonance of Ag make it possible to obtain a nanostructure with a good balance of good chemical stability and optical response. In this paper, we investigated the relationship between optical properties and the composition and size of Ag–Au alloy nanoparticle with numerical calculation by applying experimental data. Simplified empirical formulas are proposed through numerical simulation. The properties of extinction efficiency and the relative contribution of scattering and absorption efficiency to the extinction efficiency have been researched in detail. The calculated result and experimental data has been compared, and good agreement is obtained. Our work contributes greatly to catalysis application of Au–Ag alloy NPs in specific regions.