Optical properties and energy-transfer frequency upconversion of Yb 3+-sensitized Ho3+- And Tb3+-doped lead-cadmium-germanate glass and glass ceramic

In this report we investigate the optical properties and energy-transfer upconversion luminescence of Ho3+- and Tb3+/Yb 3+-codoped PbGeO3-PbF2-CdF2 glass-ceramic under infrared excitation. In Ho3+/Yb 3+-codoped sample, green(545 nm), red(652 nm), and near-infrared(754 nm) upconversion luminescence corresponding to the 4S 2(5F4) ��� 5I8, 5F5 ��� 5I8, and 4S2(5F4) ��� 5I 7, respectively, was readly observed. Blue(490 nm) signals assigned to the 5F2,3 ��� 5I8 transition was also detected. In the Tb3+/Yb3+ system, bright UV-visible emission around 384, 415, 438, 473-490, 545, 587, and 623 nm, identified as due to the 5D3(5G6) ��� 7FJ(J=6,5,4) and 5D4��� 7FJ(J=6,5,4,3) transitions, was measured. The comparison of the upconversion process in glass ceramic and its glassy precursor revealed that the former samples present much higher upconversion efficiencies. The dependence of the upconversion emission upon pump power, and doping contents was also examined. The results indicate that successive energy-transfer between ytterbium and holmium ions and cooperative energy-transfer between ytterbium and terbium ions followed by excited-state absorption are the dominant upconversion excitation mechanisms herein involved. The viability of using the samples for three-dimensional solid-state color displays is also discussed.

Infrared to visible up-conversion emission in Er3+/Yb 3+ codoped fluoro-phosphate glass-ceramics

Erbium Er3+ and ytterbium Yb3+ codoped fluoro-phosphate glasses belonging to the system NaPO3-YF 3-BaF2-CaF2 have been prepared by the classical melt-quenching technique. Glasses containing up to 10 wt% of erbium and ytterbium fluorides have been obtained and characterized using differential scanning calorimetry (DSC) and UV-visible and near-infrared spectroscopy. Transparent and homogeneous glass-ceramics have been then reproducibly synthetized by appropriate heat treatment above glass transition temperature of a selected parent glass. Structural investigations of the crystallization performed through X-ray diffractometry (XRD) and scanning electron microscopy (SEM) have evidenced the formation of fluorite-type cubic crystals based during the devitrification process. Finally, infrared to visible up-conversion emission upon excitation at 975 nm has been studied on the Er3+ and Yb 3+ codoped glass-ceramics as a function of thermal treatment time. A large enhancement of intensity of the up-conversion emissions-about 150 times- has been observed in the glass-ceramics if compared to the parent glass one, suggesting an incorporation of the rare-earth ions (REI) into the crystalline phase. �� 2012 The American Ceramic Society.

Estudo das propriedades estruturais e ��pticas do sistema v��treo 80TeO2-20WO3 dopado com Yb2O3

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Vidros a base de ��xido de tel��rio para dispositivos fot��nicos

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Convers��o descendente de energia envolvendo ��ons lantan��deos. Vidros emissores de luz na regi��o de 1000 nm

P��s-gradua����o em Qu��mica - IQ

Membranas de celulose bacteriana contendo nanopart��culas de 'YVO IND. 4': 'YB POT. 3+': 'ER POT. 3+'/'HO POT. 3+' para aplica����es envolvendo convers��o ascendente de energia

P��s-gradua����o em Qu��mica - IQ

Infrared to visible up-conversion in biocellulose yttrium vanadate nanoparticle composite membranes. Demonstration of chloroaluminum phthalocyanine light emission under up-converted light excitation

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

S��ntese e caracteriza����o de sab��es met��licos de lantan��deos (III)

P��s-gradua����o em Qu��mica - IQ

Up-conversion properties of lanthanide-organic frameworks and how to track ammunitions using these materials

This manuscript reports the first example of up-conversion properties involving Yb3+ and Tb3+ ions in five isostructural Lanthanide-Organic Frameworks (LnOFs), herein designated as UCMarker-1 to UCMarker-5, respectively, and their application as optical probes for the identification of gunshot residues (GSRs) and the ammunition encryption procedure. The excitation of the Yb3+2 F-7/2 <-> F-2(5/2) transition (980 nm) at room temperature leads to visible up-conversion (UC) emission of Tb3+ D-5(4) -> F-7(J). The GSR and lead-free primer residues are easily identified upon UV radiation (lambda = 254 nm). These results prove that the exploration of LnOFs to identify GSR is attractive for the identification of ammunition origins or caliber recognition.

Design and Characterization of New Luminescent Sensors and Labels

The aim of this Ph.D. project has been the design and characterization of new and more efficient luminescent tools, in particular sensors and labels, for analytical chemistry, medical diagnostics and imaging. Actually both the increasing temporal and spatial resolutions that are demanded by those branches, coupled to a sensitivity that is required to reach the single molecule resolution, can be provided by the wide range of techniques based on luminescence spectroscopy. As far as the development of new chemical sensors is concerned, as chemists we were interested in the preparation of new, efficient, sensing materials. In this context, we kept developing new molecular chemosensors, by exploiting the supramolecular approach, for different classes of analytes. In particular we studied a family of luminescent tetrapodal-hosts based on aminopyridinium units with pyrenyl groups for the detection of anions. These systems exhibited noticeable changes in the photophysical properties, depending on the nature of the anion; in particular, addition of chloride resulted in a conformational change, giving an initial increase in excimeric emission. A good selectivity for dicarboxylic acid was also found. In the search for higher sensitivities, we moved our attention also to systems able to perform amplification effects. In this context we described the metal ion binding properties of three photoactive poly-(arylene ethynylene) co-polymers with different complexing units and we highlighted, for one of them, a ten-fold amplification of the response in case of addition of Zn2+, Cu2+ and Hg2+ ions. In addition, we were able to demonstrate the formation of complexes with Yb3+ an Er3+ and an efficient sensitization of their typical metal centered NIR emission upon excitation of the polymer structure, this feature being of particular interest for their possible applications in optical imaging and in optical amplification for telecommunication purposes. An amplification effect was also observed during this research in silica nanoparticles derivatized with a suitable zinc probe. In this case we were able to prove, for the first time, that nanoparticles can work as ���off-on��� chemosensors with signal amplification. Fluorescent silica nanoparticles can be thus seen as innovative multicomponent systems in which the organization of photophysically active units gives rise to fruitful collective effects. These precious effects can be exploited for biological imaging, medical diagnostic and therapeutics, as evidenced also by some results reported in this thesis. In particular, the observed amplification effect has been obtained thanks to a suitable organization of molecular probe units onto the surface of the nanoparticles. In the effort of reaching a deeper inside in the mechanisms which lead to the final amplification effects, we also attempted to find a correlation between the synthetic route and the final organization of the active molecules in the silica network, and thus with those mutual interactions between one another which result in the emerging, collective behavior, responsible for the desired signal amplification. In this context, we firstly investigated the process of formation of silica nanoparticles doped with pyrene derivative and we showed that the dyes are not uniformly dispersed inside the silica matrix; thus, core-shell structures can be formed spontaneously in a one step synthesis. Moreover, as far as the design of new labels is concerned, we reported a new synthetic approach to obtain a class of robust, biocompatible silica core-shell nanoparticles able to show a long-term stability. Taking advantage of this new approach we also showed the synthesis and photophysical properties of core-shell NIR absorbing and emitting materials that proved to be very valuable for in-vivo imaging. In general, the dye doped silica nanoparticles prepared in the framework of this project can conjugate unique properties, such as a very high brightness, due to the possibility to include many fluorophores per nanoparticle, high stability, because of the shielding effect of the silica matrix, and, to date, no toxicity, with a simple and low-cost preparation. All these features make these nanostructures suitable to reach the low detection limits that are nowadays required for effective clinical and environmental applications, fulfilling in this way the initial expectations of this research project.

Broadband emission from a multicore fiber fabricated with granulated oxides

We demonstrate a multicore multidopant fiber which, when pumped with a single pump source around ���800���nm , emits a more than one octave-spanning fluorescence spectrum ranging from 925 to 2300���nm . The fiber preform is manufactured from granulated oxides and the individual cores are doped with five different rare earths, i.e., Nd3+ , Yb3+ , Er3+ , Ho3+ , and Tm3+ .

Identification of Novel Components of the Unfolded Protein Response in Arabidopsis

Unfavorable environmental and developmental conditions may cause disturbances in protein folding in the endoplasmic reticulum (ER) that are recognized and counteracted by components of the Unfolded Protein Response (UPR) signaling pathways. The early cellular responses include transcriptional changes to increase the folding and processing capacity of the ER. In this study, we systematically screened a collection of inducible transgenic Arabidopsis plants expressing a library of transcription factors for resistance toward UPR-inducing chemicals. We identified 23 candidate genes that may function as novel regulators of the UPR and of which only three genes (bZIP10, TBF1, and NF-YB3) were previously associated with the UPR. The putative role of identified candidate genes in the UPR signaling is supported by favorable expression patterns in both developmental and stress transcriptional analyses. We demonstrated that WRKY75 is a genuine regulator of the ER-stress cellular responses as its expression was found to be directly responding to ER stress-inducing chemicals. In addition, transgenic Arabidopsis plants expressing WRKY75 showed resistance toward salt stress, connecting abiotic and ER-stress responses.

Desenvolvimento de materiais nanoestruturados �� base de SiO2-Nb2O5 preparados por uma nova rota sol-gel com aplica����es em fot��nica

Este trabalho concentra-se na prepara����o e caracteriza����es estrutural e espectrosc��pica de materiais nanoestruturados �� base de SiO2-Nb2O5 dopados e codopados com ��ons Er3+, Yb3+ e Eu3+ na forma de p��s e guias de onda planares. Os nanocomp��sitos foram preparados atrav��s de uma nova rota sol-gel utilizando ��xido de ni��bio como precursor em substitui����o ao alc��xido de ni��bio. A correla����o estrutura propriedades luminescentes foi estudada por difra����o de raios X, microscopia eletr��nica de transmiss��o, espectroscopia vibracional de absor����o no infravermelho, espectroscopia vibracional de espalhamento Raman, an��lise t��rmica, reflect��ncia difusa e especular, espectroscopia de fotoluminesc��ncia e acoplamento M-line. Inicialmente foi avaliado a influ��ncia da concentra����o de ni��bio nas propriedades estruturais e luminescentes de nanocomp��sitos (100-x)Si-xNb dopados e codopados com ��ons Er3+, Yb3+ e Eu3+ tratados termicamente a 900 ��C por 3h. A cristaliza����o do Nb2O5 foi dependente da concentra����o de Nb na matriz, com a distribui����o dos ��ons lantan��deos preferencialmente no Nb2O5, afetando as propriedades luminescentes. Para os nanocomp��sitos codopados com ��ons Er3+ e Yb3+ foram obtidos valores de largura de banda a meia altura (FWHM) da ordem de 70 nm na regi��o de 1550 nm e tempos de vida de at�� 5,2 ms. A emiss��o na regi��o do vis��vel, decorrente de processos de convers��o ascendente, revelou-se dependente da concentra����o de ni��bio. Foi verificada emiss��o preferencial na regi��o do verde para menores concentra����es de Nb. Enquanto que, para as maiores concentra����es, processos de relaxa����o cruzada levaram a um aumento relativo na intensidade de emiss��o na regi��o do vermelho. A efici��ncia qu��ntica de emiss��o dos nanocomp��sitos (100-x)Si-xNb dopados com Eu3+ variou com o comprimento de onda de excita����o, refletindo os diferentes s��tios de simetria ocupados por este ��ons nesta estrutura complexa. A influ��ncia da temperatura de tratamento t��rmico no processo de cristaliza����o do Nb2O5 em nanocomp��sitos 70Si:30Nb codopados com ��ons Er3+ e Yb3+ foi avaliada. Material amorfo foi obtido a 700 ��C enquanto que a 900 e 1100 ��C foram identificas as fases ortorr��mbica (fase T) e monocl��nica (fase M) do Nb2O5. Intensa emiss��o na regi��o de 1550 nm com valores de FWHM de 52 e 67 nm e tempos de vida de 5,6 e 5,4 ms foram verificados a 700 e 900 ��C sob excita����o em 977 nm, respectivamente. Por fim, foram obtidos guias de onda planares com excelentes propriedades ��pticas e com grande potencial de aplica����o em dispositivos de amplifica����o ��ptica. Especificamente, materiais fot��nicos com banda larga de emiss��o na regi��o do infravermelho foram preparados, indicando fortemente a potencialidade para a aplica����o em telecomunica����es envolvendo n��o somente a banda C como tamb��m as bandas L e S em materiais contendo somente ��ons Er3+ como centros emissores.

Produ����o e caracteriza����o de guias de onda dopados com terras-raras contendo nanopart��culas semicondutoras.

O presente trabalho tem como objetivo estudar a produ����o e caracteriza����o de filmes finos do tipo GeO2-Bi2O3 (BGO) produzidos por sputtering-RF com e sem nanopart��culas (NPs) semicondutoras, dopados e codopados com ��ons de Er3+ ou Er3+/Yb3+ para a produ����o de amplificadores ��pticos. A produ����o de guias de onda do tipo pedestal baseados nos filmes BGO foi realizada a partir de litografia ��ptica seguida por processo de corros��o por plasma e deposi����o f��sica a vapor. A incorpora����o dos ��ons de terras-raras (TRs) foi verificada a partir dos espectros de emiss��o. An��lises de espectroscopia e microscopia foram indispens��veis para otimizar os par��metros dos processos para a constru����o dos guias de onda. Foi observado aumento significativo da luminesc��ncia do Er3+ (regi��o do vis��vel e do infravermelho), em filmes finos codopados com Er3+/Yb3+ na presen��a de nanopart��culas de Si. As perdas por propaga����o m��nimas observadas foram de ~1,75 dB/cm para os guias pedestal em 1068 nm. Para os guias dopados com Er3+ foi observado aumento significativo do ganho na presen��a de NPs de sil��cio (1,8 dB/cm). O ganho ��ptico nos guias de onda amplificadores codopados com Er3+/Yb3+ e dopados com Er3+ com e sem NPs de sil��cio tamb��m foi medido. Ganho de ~8dB/cm em 1542 nm, sob excita����o em 980 nm, foi observado para os guias pedestal codopados com Er3+/Yb3+ (Er = 4,64.1019 ��tomos/cm3, Yb = 3,60.1020 ��tomos/cm3) com largura de 80 ��m; para os guias codopados com concentra����o superior de Er3+/Yb3+ (Er = 1,34.1021 ��tomos/cm3, Yb = 3,90.1021 ��tomos/cm3) e com NPs de Si, foi observado aumento do ganho ��ptico de 50% para guia com largura de 100 ��m. Os resultados apresentados demonstram que guias de onda baseados em germanatos, com ou sem NPs semicondutoras, s��o promissores para aplica����es em dispositivos fot��nicos.

Condensed-phase optical refrigeration

We review progress on laser cooling of solids. The general process that enables cooling to occur is based on anti-Stokes fluorescence. Candidate materials for laser cooling are discussed, including gases, dyes, crystals, semiconductors, and ionically doped glasses. Cooling processes and necessary conditions for cooling are outlined, and general thermodynamic limitations are discussed. This is followed by a more detailed discussion of one specific material, ytterbium-doped ZBLAN, with consideration given to optimization of the laser cooling process and applications. (C) 2003 Optical Society of America.