Papers by Keyword: Up-Conversion

Abstract: In this article, Ho³⁺ doped and Yb³⁺/ Ho³⁺ co-doped Y₂WO₆ phosphors were successfully prepared via high temperature solid method. Their structures were investigated with X-ray diffraction, the up-conversion (UC) excitation from a 980 nm diode laser, and the developed phosphor shown two UC emission bands in the visible region 540 and 643 nm. Based on the result, the intensity of the frequency up-conversion emission was enhanced significantly through co-doping with Yb³⁺ ions in the Y₂WO₆: Ho³⁺ phosphor. The dependence of emission intensity on the pump power indicated that the up-conversion emission was a two-photon process. At last, the energy level diagrams was discussed. The results show that Y₂WO₆ is a promising host material for UC phosphors.

Abstract: Na (Y_1.5Na_0.5)F₆ microparticks were prepared by hydrothermal method. EDTA as the chelating agent. The samples were characterized by X-ray diffraction, scanning electron microscopy and fluorescence spectrometer. The X-ray diffraction indicates that the crystal shows a hexagon phase structure. Under the excitation of 980nm laser, the Na (Y_1.5Na_0.5)F₆ exhibited strong up-conversion light: ⁴F_9/2→⁴I_15/2(red), ⁴H_11/2/⁴S_3/2→⁴I_15/2(green) and ⁴G_11/2→²H_9/2 (near-ultraviolet).

Abstract: A series of ytterbium and erbium co-doped sodium yttrium fluoride (NaYF₄:Yb³⁺, Er³⁺) ceramics have been successfully prepared by pressureless sintering. The ceramic samples were characterized by X-ray diffraction (XRD), photoluminescence (PL), density and field emission scanning electron microscope (FESEM). The results showed that the phases of the NaYF₄:Yb³⁺, Er³⁺ ceramic samples transformed when the sintering temperature was changed. The ceramic samples sintered below 600 ^oC contained both cubic α-NaYF₄:Yb³⁺, Er³⁺ and hexagonal β-NaYF₄:Yb³⁺, Er³⁺. The sample sintered at 600^oC is the pure hexagonal β-NaYF₄:Yb³⁺, Er³⁺. When the sintering temperature is above 600 ^oC, the ceramic samples present the α-NaYF₄:Yb³⁺, Er³⁺ again. The fluorescence intensity increased firstly and then decreased with the sintering temperature increasing. The luminous intensity of the sample sintered at 600 ^oC was the highest. The densities of as-prepared ceramic sample increased with the sintering temperature rising. The samples sintered at 600 ^oC with different holding time possessed the similar crystal phases (β-NaYF₄:Yb³⁺, Er³⁺) and fluorescence intensity. As the holding time increased, the densities of the samples increased. To obtain more dense ceramics, the ceramics using β-NaYF₄:Yb³⁺, Er³⁺ powders were prepared by spark plasma sintering (SPS). The maximum relative density reached 97%.

Abstract: Modifying the optical characteristics of rare earth (RE) doped inorganic glasses by stimulating surface plasmon resonance (SPR) via controlled growth of metal nanoparticles (NPs) is an outstanding quest in glass plasmonics. Glasses with composition 70TeO₂-20ZnO-10Na₂O-(x)Er₂O₃-(y)Au (x = 0.0 and 1.0 mol%; y = 0.0 and 0.6 mol% both in excess) are synthesized using melt-quenching technique and characterized. Influences of heat treatment temperature on the growth of Au NPs and their subsequent impacts on Raman spectral features modifications are inspected. The amorphous nature of glass is confirmed by using XRD. TEM reveal the non-spherical Au NPs with average diameter vary from 7.4 to 10.3 nm. Surface plasmon band is evidenced around 627 - 632 nm. Raman spectra demonstrate the presence of Er-O and Zn-O bond, anti-symmetric vibrations of Te-O-Te bonds and stretching modes of non-bonded oxygen exists in TeO₃ and TeO₃₊₁ unit. The amplifications in Raman signals by a factor of 1.39, 1.40, 0.88 and 1.29 and 1.25 corresponding to the peak centered at 262, 382, 536, 670 and 725 cm^-1 are attributed to the contribution of a surface plasmon (SP) generating a strong, localized and secondary field. The excellent features of the results suggest that our systematic method of controlled NPs growth may constitute a basis for improving the spectral features of tellurite glasses useful for the development of efficient and economic up-converted lasers.

Abstract: This presentation provides a panoramic overview of the recent progress in nanoglass plasmonics, challenges, excitement, applied interests and the future promises. A glimpse of our gamut research activities with some significant results is highlighted and facilely analyzed. The term 'nanoglass' refers to the science and technology dealing with the manipulation of the physical properties of rare earth doped inorganic glasses by embedding metallic nanoparticles (NPs) or nanoclusters. On the other hand, the word 'plasmonics' refer to the coherent coupling of photons to free electron oscillations (called plasmon) at the interface between a conductor and a dielectric. Nanoglass plasmonis being an emerging concept in advanced optical material of nanophotonics has given photonics the ability to exploit the optical response at nanoscale and opened up a new avenue in metal-based glass optics. There is a vast array of nanoglass plasmonic concepts yet to be explored, with applications spanning solar cells, (bio) sensing, communications, lasers, solid-state lighting, waveguides, imaging, optical data transfer, display and even bio-medicine. Localized surface plasmon resonance (LSPR) can enhance the optical response of nanoglass by orders of magnitude as observed. The luminescence enhancement and surface enhanced Raman scattering (SERS) are new paradigm of research. A thumbnail sketch of the fundamental aspects of SPR, LSPR, SERS and photonic applications of various rare earth doped/co-doped binary glasses containing metallic NPs are presented. The recent development in nanoglass in the context of Malaysia at the outset of international scenario is projected.

Abstract: Rare-earth (RE) ions-doped oxyfluoride transparent glass-ceramics containing nano-crystalline phases with very low phonon energies like LaF₃, NaLaF₄ and KLaF₄ combine the superior optical performance of low phonon energy phases with the high mechanical, chemical and thermal stability of oxide silicates. The insertion of the doping RE ions in the fluoride nanocrystals enhances the radiative optical emission processes currently focused on up- and down-conversion emissions. Thus, a key point is to identify and quantify the RE ions in the fluoride nano-crystals. In this contribution an oxyfluoride glass and the corresponding glass-ceramics of composition 55 SiO₂. 20 Al₂O₃.15 Na₂O.10 LaF₃ mol % doped with 1 mol % Tm₂O₃ is presented. The Tm³⁺ incorporation in the precipitated LaF₃ nano-crystals has been analysed by two different techniques. Firstly, TEM and Energy Dispersive X-Ray Spectroscopy (EDXS) were used to perform elemental distribution mappings of RE elements that allow to directly localising RE ions in the glass and glass-ceramics. Additionally, X-ray absorption spectroscopy (XAS) measurements were performed to analyse the distribution and first coordination sphere of Tm³⁺ ions in the glass and glass–ceramics by using X-ray absorption near edge structure spectroscopy (XANES) and extended absorption X-ray fine structure spectroscopy (EXAFS), which have allow to quantify the Tm³⁺ incorporation in the LaF₃ nano-crystals.

Abstract: For producing RGB tricolor luminescence, three kinds of components of rare-earth ions is chosen, which are Er³⁺ doping, Er³⁺-Yb³⁺ co-doping and Tm³⁺-Yb³⁺ co-doping, respectively. Three kinds of rare-earth doped up-conversion fluoride material are prepared based on high temperature solid-state method. Under being excited by 980nm laser, three materials emit red, green and blue light, whose peak wavelengths are 660nm, 550nm and 480nm, respectively. Through analysis of luminescence process, it can be concluded that red and green luminescence are belong to two-photon absorption transversion, and blue luminescence is three-photon absorption transversion.

Abstract: β-NaGdF₄: Yb, Tm/β-NaGdF₄: Eu and β-NaGdF₄: Yb, Tm, Eu particles were successfully synthesized by two different methods, solvothermal method and high-energy ball milling. The properties were measured by X-ray diffraction (XRD), TEM and luminescence spectra. All samples shown the strong photoluminescence intensity under 980 nm light excitation and emission of Eu³⁺ was observed. Finally, two methods are compared in paper.

Abstract: LiTaO₃: Tm³⁺, Yb³⁺ powders were synthesized by a high-energy ball-milling (HEB) method compared with the conventional solid-state reaction (SSR) method. Under the excitation of 980 nm laser, the strong blue emission (477 nm) band is observed and attributed to ¹G₄- ³H₆ of Tm³⁺. Because of it causing high local temperature and narrow particles size, increasing the contact area between the particles and improved crystallinity of the host, synthesis by high-energy ball milling show higher photoluminescence (PL) intensity compared to the solid state reaction method. In the process of mechanical milling, Tm³⁺, Yb³⁺ co-doped LiTaO₃ phosphors with high photoluminescence property could be achieved at a relatively low reaction temperature.

Abstract: Rare earth ion-doped nanoparticles NaYF₄:Yb³⁺,Ho³⁺ is one of the most efficient up-conversion nanosystems, when mixing a TiO₂ heterogeneous layer outside can extends the range of NaYF₄:Yb³⁺,Ho³⁺ nanoparticles absorb solar energy. In this work, a multi-functional mixed NaYF₄:Yb³⁺,Ho³⁺-TiO₂ structure was synthesized. The micromorphology, structure and particle size of the up-converting nanoparticles were characterized by transmission electron microscopy (TEM), and room temperature up-conversion luminescence (UCL) spectrofluorimetric measurements. The mixture of NaYF₄:Yb³⁺,Ho³⁺ and TiO₂ nanoparticles was applied to Dye-sensitized solar cells (DSSCs), the photoelectric conversion efficiency of the DSSC with up-conversion material is nearly twice as much as of the control DSSC irradiated by infrared (IR) light.