Spectroscopic investigations of OH- influence on near-infrared fluorescence quenching of Yb3+/Tm3+ co-doped sodium-metaphosphate glasses

Energy transfer processes were studied in two sets of Yb3+ and Tm3+ co-doped sodium-metaphosphate glasses, prepared in air and nitrogen atmospheres. Using Forster, Dexter, and Miyakawa theoretical models, the energy transfer parameters were calculated. The main ion-ion energy transfer processes analyzed were energy migration among Yb3+ ions, cross-relaxations between Yb3+ and Tm3+ ions, and interactions with OH- radicals. The results indicated that Yb -> Tm energy transfer favors 1.8 mu m emissions, and there is no evidence of concentration quenching up to 2% Tm2O3 doping. As expected, samples prepared in nitrogen atmosphere present higher fluorescence quantum efficiency than those prepared in air, and this feature is specially noted in the near-infrared region, where the interaction with the OH- radicals is more pronounced. (c) 2007 Published by Elsevier B.V.

Structural-electronic aspects related to the near-infrared light emission of Fe-doped silicon films

The need of efficient (fast and low consumption) optoelectronic devices has always been the driving force behind the investigation of materials with new or improved properties. To be commercially attractive, however, these materials should be compatible with our current micro-electronics industry and/or telecommunications system. Silicon-based compounds, with their matured processing technology and natural abundance, partially comply with such requirements-as long as they emit light. Motivated by these issues, this work reports on the optical properties of amorphous Si films doped with Fe. The films were prepared by sputtering a Si+Fe target and were investigated by different spectroscopic techniques. According to the experimental results, both the Fe concentration and the thermal annealing of the samples induce changes in their atomic structure and optical-electronic properties. In fact, after thermal annealing at similar to 750 degrees C, the samples partially crystallize with the development of Si and/or beta-FeSi(2) crystallites. In such a case, certain samples present light emission at similar to 1500 nm that depends on the presence of beta-FeSi(2) crystallites and is very sensitive to the annealing conditions. The most likely reasons for the light emission (or absence of it) in the considered Fe-doped Si samples are presented and discussed in view of their main structural-electronic characteristics. (C) 2011 Elsevier Ltd. All rights reserved.

THE CRYSTAL STRUCTURE OF A MICROLITE-GROUP MINERAL WITH A FORMULA NEAR NaCaTa(2)O(6)F FROM THE MORRO REDONDO MINE, CORONEL MURTA, MINAS GERAIS, BRAZIL

We present electron-microprobe and single-crystal X-ray-diffraction data for a microlite-group mineral with a formula near NaCaTa(2)O(6)F from the Morro Redondo mine, Coronel Murta, Minas Gerais, Brazil. On the basis of these data, the formula is A(Na(0.88)Ca(0.88)Pb(0.02)square(0.22))(Sigma 2.00) (B)(Ta(1.70)Nb(0.14)Si(0.12)As(0.04))(Sigma 2.00) (X)[(O(5.75)(OH)(0.25)](Sigma 6.00) (Y)(F(0.73)square(0.27))(Sigma 1.00). According to the new nomenclature for the pyrochlore-supergroup minerals, it is intermediate between fluornatromicrolite and "" fluorcalciomicrolite"". The crystal structure, F (d3) over barm, a = 10.4396(12) angstrom, has been refined to an R(1) value of 0.0258 (wR(2) = 0.0715) for 107 reflections (MoK alpha radiation). There is a scarcity of crystal-chemical data for pyrochlore-supergroup minerals in the literature. A compilation of these data is presented here.

Cholesterol Hydroperoxides Generate Singlet Molecular Oxygen [O(2) ((1)Delta(g))]: Near-IR Emission, (18)O-Labeled Hydroperoxides, and Mass Spectrometry

In mammalian membranes, cholesterol is concentrated in lipid rafts. The generation of cholesterol hydroperoxides (ChOOHs) and their decomposition products induces various types of cell damage. The decomposition of some organic hydroperoxides into peroxyl radicals is known to be a potential source of singlet molecular oxygen [O(2) ((1)Delta(g))] in biological systems. We report herein on evidence of the generation of O(2) ((1)Delta(g)) from ChOOH isomers in solution or in liposomes containing ChOOHs, which involves a cyclic mechanism from a linear tetraoxide intermediate originally proposed by Russell. Characteristic light emission at 1270 nm, corresponding to O(2) ((1)Delta(g)) monomolecular decay, was observed for each ChOOH isomer or in liposomes containing ChOOHs. Moreover, the presence of O(2) ((1)Delta(g)) was unequivocally demonstrated using the direct spectral characterization of near-infrared light emission. Using (18)O-labeled cholesterol hydroperoxide (Ch(18)O(18)OH), we observed the formation of (18)O-labeled O(2) ((1)Delta(g)) [(18)O(2) ((1)Delta(g))] by the chemical trapping of (18)O(2) ((1)Delta(g)) with 9,10-diphenylanthracene (DPA) and detected the corresponding (18)O-labeled DPA endoperoxide (DPA(18)O(18)O) and the (18)O-labeled products of the Russell mechanism using high-performance liquid chromatography coupled to tandem mass spectrometry. Photoemission properties and chemical trapping clearly demonstrate that the decomposition of Ch(18)O(18)OH generates (18)O(2) ((1)Delta(g)), which is consistent with the Russell mechanism and points to the involvement of O(2) ((1)Delta(g)) in cholesterol hydroperoxide-mediated cytotoxicity.

Studies on the resonance Raman spectra of polyaniline obtained with near-IR excitation

The effects of near-IR (NIR) laser power over the Raman spectra of poly(aniline) emeraldine salt (PANIES) and base (PANI-EB) were investigated. The reasons for the existence of several bands from 1324 to 1500 cm-1 in the Raman spectra of poly(aniline) obtained at NIR region were also studied. The bands from 1324 to 1375 cm-` were associated to vC-N of polarons with different conjugation lengths and the bands from 1450 to 1500 cm-1 in Raman spectra of PANI emeraldine and pernigraniline base forms were correlated to vC=N modes associated with quinoid units having different conjugation lengths. The increase of laser power at 1064.0 run causes the deprotonation of PANI-ES and the formation of cross-linking segments having phenazine and/or oxazine rings. For PANI-EB only a small spectral change is observed when the laser power is increased, owing to the low absorption of this form in the NIR region. Copyright (c) 2007 John Wiley & Sons, Ltd.

Biolabeling with nanoparticles based on Y(2)O(3):Nd(3+) and luminescence detection in the near-infrared

Neodymium based fluorescence presents several advantages in comparison to conventional rare earth or enzyme-substrate based fluorescence emitting sources (e.g.Tb, HRP). Based on this fact we have herein explored a Nd-based fluoroimmunoassay. We efficiently detected the presence of an oxidized low-density lipoprotein (oxLDL) in human plasma a well-known marker for cardiovascular diseases, which causes around 30% of deaths worldwide. Conventional fluoroimmunoassay uses time-resolved luminescence techniques, with detection in the visible range, to eliminate the fluorescence background from the biological specimens. By using an immunoassay based on functionalized Y(2)O(3):Nd(3+) nanoparticles, where the excitation and emission processes in the Nd(3+) ion occur in the near-infrared (NIR) region, we have succeeded in eliminating the interferences from the biological fluorescence background, avoiding the use of time-resolved techniques. This yields higher emission intensity from the Nd(3+)-nanolabels and efficient detection of anti-oxidized low-density lipoproteins (anti-oxLDL) by Y(2)O(3):Nd(3+)-antibody-antigen conjugation, leading to a novel biolabeling method. (C) 2010 Elsevier B.V. All rights reserved.

The travel imagination and the hybrid reality in the wake of colonialism

The “traveling imagination,” is of paramount importance to both western and postcolonial travelers. Since both groups create “travel imaginations” by extensive reading, the nature of the books that inform them must directly affect their travels. A westerner, for example, who reads only colonial-era accounts has the “travel imagination” of a different generation. If all perspectives were represented equally in libraries, the “travel imagination” of a given person would be entirely his/her own. But usually the “traveler’s imagination” is biased by prevailing opinion. Libraries are not democracies, and sometimes extensive reading only indoctrinates the reader with the biases of the canon. Perhaps the following generalization will be helpful. Westerners are able to create “traveling imaginations,” based on the books they trust. But postcolonials, who have reason to be suspicious of what they read, have complicated “traveling imaginations.” Sometimes postcolonial travelers base their “traveling imaginations” on what they read, and sometimes, in opposition to what they read. The books discussed in this thesis, In Patagonia, The Cruise of the Shark, The Happy Isles of Oceania, A Passage to England and The Enigma of Arrival, were first published in, 1977, 1939, 1992, 1971 and 1987, respectively, in what Ali Behdad calls the “age of colonial dissolution.” Perhaps it would be more accurate to say these books are set in the “age of colonial demolition.” For the most part, the empires in these texts are in ruins, or at least in the process of being dismantled. In fact, two of the authors, Nirad Chaudhuri and V.S. Naipaul are canonical post-colonial thinkers.

Point of View: Going Home: Far and Near

Nikky-Guninder K. Singh on going home to Punjab.

Ant communities (Hymenoptera: Formicidae) in an urban ecosystem near the Atlantic Rainforest

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Use of near-infrared Raman spectroscopy to detect IgG and IgM antibodies against Toxoplasma gondii in serum samples of domestic cats

Near-infrared Raman spectroscopy (NIRS) is a particularly promising technique that is being used in recent years for many biomedical applications. Optical spectroscopy has gained increasing prominence as a tool for quantitative analysis of biological samples, clinical diagnostic, concentration measurements of blood metabolites and therapeutic drugs, and analysis of the chemical composition of human tissues. Toxoplasmosis is an important zoonosis in public health, and domestic cats are the most important transmitters of the disease. This disease can be detected by several serological tests, which usually have a high cost and require a long time. The goal of this work was to investigate a new method to diagnosis Toxoplasma gondii infections using NIRS. In order to confirm antibody detection, 24 cat blood scrum samples were analyzed by the Raman spectra, from which 23 presented positive serology to toxoplasmosis and one was a reference negative serum. Characteristic Raman peaks allowed differentiation between negative and positive sera, confirming the possibility of antibody detection by Raman spectroscopy. These results give the first evidence that this technique can be useful to quantify antibodies in cat sera.