Nanoparticles phosphors

Herein we briefly mention historical aspects on preparation of monometallic or bimetallic nanoparticles as science. In 1857, Faraday prepared dispersion solution of Au colloids by chemical reduction of aqueous solution of Au(III) ions with phosphorous [6]. One hundred and thirty-one years later, in 1988, Thomas confirmed that the colloids were composed of Au nanoparticles with 3-30 nm in particle size by means of electron microscope [7]. In 1941, Rampino and Nord prepared colloidal dispersion of Pd by reduction with hydrogen, protected the colloids by addition of synthetic pol5mer like polyvinylalcohol, applied to the catalysts for the first time [8-10]. In 1951, Turkevich et al. [11] reported an important paper on preparation method of Au nanoparticles. They prepared aqueous dispersions of Au nanoparticles by reducing Au(III) with phosphorous or carbon monoxide (CO), and characterized the nanoparticles by electron microscopy. They also prepared Au nanoparticles with quite narrow... 

One of the critical issues with regard to low temperamre fuel cells is the gradual loss of performance due to the degradation of the cathode catalyst layer under the harsh operating conditions, which mainly consist of two aspects electrochemical surface area (ECA) loss of the carbon-supported Pt nanoparticles and corrosion of the carbon support itself. Extensive studies of cathode catalyst layer degradation in phosphoric acid fuel cells (PAECs) have shown that ECA loss is mainly caused by three mechanisms ... 

This comparison of the spectroscopic properties of the different types of fluorescent reporters underlines that semiconductor QDs and upconverting nanoparticles have no analogs in the field of organic dyes. Therefore, their unique features are unrivaled. The different molecular labels detailed here each display unique advantages that can compete with some of the favorable features of QDs and upconverting phosphors such as long lifetimes in the case of MLC systems and lanthanide chelates or very narrow emission bands for lanthanide chelates beneficial for spectral multiplexing. 

A general feature of doped semiconductive NC materials is described in a review paper authored by Bhargava, one of the founders of this area (8). It is generally accepted that solid particles are richer in crystallographical defects when their diameter becomes smaller. Quantum size effects associated with nanoparticles are very sensitive to the defects. In most cases, defects influence negatively the luminescent properties of phosphors. Most of these drawbacks of NC phosphors are attributed to the larger specific surface area, since defects tend to concentrate themselves in a near-surface region. 

The optical properties of lanthanide ions in some ID nanomaterials may behave differently from those of isotropic nanoparticles and bulk materials. Nanowires (NWs) of EuiLaPCU phosphors with a diameter of 10-20 nm and a length of several hundred nanometers were... 

Since oxide materials are extensively used in practical devices such as lamp phosphors or laser materials, their behavior at the nanoscale level has also been investigated. The size of yttrium oxide nanoparticles Y2C>3 Ln can be finely tuned by glycine-nitrate combustion synthesis. The overall equation of the exothermic reaction can be expressed as ... 

Tony Cheetham was a member of the Chemistry faculty at Oxford, 1974-1991, and has been at the University of California at Santa Barbara since 1991. He is Professor in both the Materials and Chemistry Departments at UCSB, and since 2004 has been the Director of the new International Center for Materials Research (ICMR). Cheetham s research interests lie in the area of functional inorganic materials and currently include hybrid framework materials, phosphors for solid state lighting, and inorganic nanoparticles. 

The resulting MnS nanoparticles can be used as a phosphor in thin-lihn electroluminescence devices (Khaorapapong et al. 2009). The incorporation of CdS, ZnS, and/or PbS into mesoporous silica (Chen et al. 1998 Zhang et al. 2001 Gao et al. 2001), layered metal oxides (Shangguan and Yoshida 2002), and layered metal phosphate (Cao et al. 1991) has also been reported. 

Igarashi, T., Kusunoki, T., Ohno, K., Isobe, T., and Seima, M., Degradation proof modification of ZnS-based phosphors with ZnO nanoparticles. Mater. Res. Bull, 36, 1317, 2001. 

Pt and Pt-bimetallic nanoparticle catalysts were employed in commercial prototype phosphoric acid fuel cells even in the mid-1970s [7], so in fact the concept of nanoparticle electrocatalysts is not new. Like many industrial catalysts, however, the catalysts are put into use long before their structure and properties are clearly understood, and that was certainly the case, for example, for the Pt-Co-Cr air cathode catalysts used at United Technologies [8]. In this chapter we review studies, primarily from our laboratory, of Pt and Pt-bimetallic nanoparticle electrocatalysts for the oxygen reduction reaction (ORR) and the electrochemical oxidation of H2 (HOR) and H2/CO mixtures. 

In the mid-twentieth century, an important paper was reported by Turkevich et al. [13]. Gold nanoparticles were prepared with various methods involving phosphorous and carbon monoxide reductions of [AuCU] in solution and characterized by electron microscopy. It is noteworthy that gold nanoparticles with quite narrow size distributions and small mean diameters in the range of 10 to... 

A long list of oxides was prepared sonochemically. Almost all the above-mentioned oxides were synthesized in organic solvents. The other oxides that will be discussed from here on were all prepared in aqueous solutions. Submicron size spheres of silica and alumina prepared by well-known methods were coated sonochemically by nanoparticles of oxides of europium and terbium using the same concentration of ions [81]. We have also used sonochemistry to prepare nanoparticles of silica and alumina doped with the same rare-earth ions for comparison. The highest luminescence intensities were observed for europium and terbium doped in nanoparticles of alumina of dimension 20-30 run. The intensities are comparable or higher than in commercial phosphors. 

Lin, S. H., Pan, C. L., Leu, H. G. (1999). Liquid membrane extraction of 2-chlorophenol from aqueous solution. Journal of Hazardous Materials 65 289-304. Raghuraman, B.J., Tirmizi, N.P., Kim, B.-S., Wiencek, J. M. (1995). Emulsion Liquid Membranes for Wastewater Treatment Equihbrium Models for Lead- and Cadmium-di-2-ethylheyl Phosphoric Acid Systems. Environmental Science and Technology 29 979-984. Liu, H. J., Wu, Q. S., Ding, Y. P., Liu, L. (2004). Biomimetic synthesis of metastable PbCrO4 nanoparticles by emulsion liquid membrane system with carrier and coupled treatment of Pb(II) and Cr(VI) wastewaters. Hrtij Chimica Sinica 62 946-950. 

The phosphoric acid fuel cell (PAFC) has a quite similar construction and components as the PEMFC the electrolyte is liquid phosphoric acid in an inert matrix. The operation temperature of 200°C avoids formation of liquid water and improves CO tolerance of the electrocatalyst. For the catalyst properties, the same requirements are valid as for the PEMFC - nanoparticles with a high surface area and a good dispersion on the carbon carrier material are required. The application of PAFC typically is the combined heat and power supply in the 200-kW power range. 

Lamellar nanohybrids composed of Ln203 layers regularly separated from each other by organic layers of intercalated benzoate molecules can be obtained by a one-pot procedure (Karmaoui et al., 2006), the benzyl alcohol route. Lanthanide isopropoxides are simply dissolved in benzyl alcohol and reacted at high temperature (250-300 °C), resulting in the isolation of nanoparticles of 50-nm mean size. Eu -doped nanohybrids have better radiance characteristics than the standard phosphor Y203 Eu while both yttrium- and gadolinium-based nanomaterials doped with Nd display intense NIR luminescence, with a Nd( F3/2) lifetime of 49 ps in the case of the yttrium nanohybrid (Sa Ferreira et al., 2006). 

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