Space-selective co-precipitation of silver and gold nanoparticles in femtosecond laser pulses irradiated Ag+, Au3+ co-doped silicate glass

We report on space-selective co-precipitation of silver and gold nanoparticles in Ag+, Au3+ co-doped silicate glasses by irradiation of femtosecond laser pulses and subsequent annealing at high temperatures. The color of the irradiated area in the glass sample changed from yellow to red with the increase of the annealing temperature. The effects of average laser power and annealing temperature on precipitation of the nanoparticles were investigated. A reasonable mechanism was proposed to explain the observed phenomena. (c) 2006 Elsevier Ltd. All rights reserved.

Effect of lithium-sodium mixed-alkali on phase transformation kinetics in Er3+/Yb3+ co-doped aluminophosphate glasses

Er3+ doped aluminophosphate glasses with various Na2O/Li2O ratios were prepared at 1250 degrees C using a silica crucible to study mixed alkali effect (MAE). The effect of relative alkali content on glass transition temperature, crystallization temperature and thermal stability were investigated using differential scanning calorimetry (DSC). In addition, apparent activation energies for crystallization, E, were determined employing the Kissinger equation. The effect of Al2O3 content on the magnitude of MAE was also discussed. No mixed-alkali effect is observed on crystallization temperature. (c) 2006 Elsevier B.V. All rights reserved.

Planar waveguides formed in a new chemically stable Er3+/Yb3+ co-doped phosphate glass

A new Er(3+)/Yb(3+) co-doped phosphate glass has been prepared, which exhibits good chemical durability and spectralproperties. Planar graded index waveguides have been fabricated in the glass by (Ag+)-Na(+) ion exchange in a mixed melt of silver nitrate and potassium nitrate. Ion exchange is carried out by varying the process parameters such as temperature, diffusion time, and molten salt compositions. The diffusion parameters, diffusion coefficients, and activation energy are determined by the guidelines of fabricated waveguides, which are determined by the input prism coupling technique.

Effects of chloride substitution on the chemical and physical properties and the crystallization behavior in heavy metal fluoride glasses

Effect of the substitutions of chloride for fluoride on the chemical and physical properties and the crystallization behavior in heavy metal fluoride glasses has been investigated. The characteristic temperature of the glass does not changed obviously when the fluoride was taken place by chloride. Compared with samples of being free of ErF3, the doping samples are more inclined to be surface crystallization. Optical basicity in the glass system increases with increasing the negative charge provided by the chloride atoms and the absorption peak red shifted is observed in absorption spectra. XRD measurements show that not a single crystalline phase appears in the heated glass samples, which indicate the substitutions of chloride for fluoride with a variety of crystalline precipitation trends. (c) 2007 Elsevier B.V All rights reserved.

Energy transfer between Cr3+ and Ni2+ in transparent silicate glass ceramics containing Cr3+/Ni2+ co-doped ZnAl2O4 nanocrystals

The emission intensity of Ni2+ at 1200 nm in transparent ZnO-Al2O3-SiO2 glass ceramics containing ZnAl2O4 nanocrystals is improved approximately 8 times by Cr3+ codoping with 532 nm excitation. This enhanced emission could be attributed to an efficient energy transfer from Cr3+ to Ni2+, which is confirmed by time-resolved emission spectra. The energy transfer efficiency is estimated to be 57% and the energy transfer mechanism is also discussed. (C) 2008 Optical Society of America.

Microwave Resonant and Zero-Field Absorption Study of Doped Magnetite Prepared by a Co-Precipitation Method

Fe3O4 and ZnxFe3-xO4 pure and doped magnetite magnetic nanoparticles (NPs) were prepared in aqueous solution (Series A) or in a water-ethyl alcohol mixture (Series B) by the co-precipitation method. Only one ferromagnetic resonance line was observed in all cases under consideration indicating that the materials are magnetically uniform. The shortfall in the resonance fields from 3.27 kOe (for the frequency of 9.5 GHz) expected for spheres can be understood taking into account the dipolar forces, magnetoelasticity, or magnetocrystalline anisotropy. All samples show non-zero low field absorption. For Series A samples the grain size decreases with an increase of the Zn content. In this case zero field absorption does not correlate with the changes of the grain size. For Series B samples the grain size and zero field absorption behavior correlate with each other. The highest zero-field absorption corresponded to 0.2 zinc concentration in both A and B series. High zero-field absorption of Fe3O4 ferrite magnetic NPs can be interesting for biomedical applications.

Exploring new labelling strategies for boronated compounds: towards fast development and efficient assessment of BNCT drug candidates

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Investigations on bismuth and aluminum co-doped germanium oxide glasses for ultra-broadband optical amplification

The broadband luminescence covering 1.2-1.6 mu m was observed from bismuth and aluminum co-doped germanium oxide glasses pumped by 808 nm laser at room temperature. The spectroscopic properties of GeO2:Bi,Al glasses strongly depend on the glass compositions and the pumping sources. To a certain extent, the Al3+ ions play as dispersing reagent for the infrared-emission centers in the GeO2:Bi,Al glasses. The broad infrared luminescence with a full width at half maximum larger than 200 nm and a lifetime longer than 200 mu s possesses these glasses with the potential applications in broadly tunable laser sources and ultra-broadband fiber amplifiers in optical communication field. (c) 2005 Elsevier B.V. All rights reserved.

Preparação e caracterização de microesferas poliméricas à base de poli(ácido metacrílico-co-divinilbenzeno) obtidas por polimerização por precipitação

Neste trabalho foi feito um estudo sobre a preparação e caracterização de microesferas poliméricas à base de poli(ácido metacrílico-co-divinilbenzeno) por polimerização por precipitação. As partículas foram sintetizadas e analisadas em diferentes condições de reação. Partículas esféricas políméricas foram sintetizadas na faixa de 1,66 - 8,41 m, assim como partículas no estado de microgel. As partículas foram caracterizadas pelas técnicas de espalhamento de luz dinâmica (DLS), análise termogravimétrica (TGA), espectroscopia na região do infravermelho (FTIR), adsorção de nitrogênio pelos métodos BET (Brunauer, Emmett e Teller) e BJH (Barret, Joyner e Halenda), microscopia ótica, microscopia eletrônica de varredura, e testes de razão de inchamento. A análise das partículas foi feita para verificar a influência da mudança na composição de comonômeros, grau de reticulação, relação de monômeros totais/diluentes em massa/volume (g/100 mL), e quanto à relação volumétrica de diluentes. Verificou-se que houve um aumento no tamanho das partículas e da resistência térmica com a diminuição da fração molar de MAA (ácido metacrílico). Na preparação de partículas com fração molar de 50% de MAA, e relação volumétrica acetonitrila/tolueno de 75/25, quanto maior a relação de monômeros totais/diluentes (g/100 mL), maior o tamanho e o rendimento das partículas. Com a mudança da relação volumétrica de diluentes, houve mudança nas características de porosidade, tamanho das partículas, e grau de inchamento das partículas, sendo que na relação volumétrica acetonitrila/tolueno de 50/50, houve formação de microgel