Tuesday, May 12, 2015

Seminar: "“Fluorophosphate glasses doped with Er3+ and Yb3+: Structural and Photophysical Characterization”y by Andrea S. S. de Camargo" 5/12/15, 11:00am-noon/ CREOL RM 103

“Fluorophosphate glasses doped with Er3+ and Yb3+: Structural and Photophysical Characterization”
Tuesday, May 12, 2015 11:00am-12:00pm

Andrea S. S. de Camargo
Physics Institute of São Carlos, University of São Paulo, São Carlos – SP, Brazil.

Celebrating the International Year of Light 2015

Rare-earth (RE)-doped oxide glasses and glass-ceramics are still at the focus of much research for laser applications in the infrared and visible spectral regions. In order to facilitate the development of materials with optimized optical properties (high absorption and emission cross sections, suitable excited state lifetime values, manageable energy transfer) while still maintaining chemical and mechanical stability, detailed structural information is of utmost importance. This information regards the chemical bonding environment of the RE dopant, its coordination sphere, the distribution in the amorphous (or partially crystalized) network and the possible formation of clusters that can result in fluorescence quenching. The combination of optical spectroscopic techniques (UV-VIS, FT-IR, steady-state and time resolved fluorescence) with magnetic resonance techniques (NMR, EPR) offers the opportunity to approach the systems from different points of view so that structure-function correlations can be drawn. Among the most interesting materials for current applications are phosphates glasses and ceramics. Still, they present disadvantages such as low mechanical resistance and hygroscopicity which can prevent laser action due to energy transfer to OH- groups. Lately, oxyfluoride glasses have attracted much attention with the promise to combine merits of fluorides (low phonon energy, moderate refractive indexes, and extensive IR window) and of oxide glasses (high chemical and mechanical stability and higher RE solubility). In this work, we present new fluoro-aluminophosphate glasses with compositions 0.25BaF2–0.25SrF2–(0.3-x)Al(PO3)3–xAlF3–(0.2-z)YF3-zREF3 with x = 15 and 20 mol%, RE = Er3+ and/or Yb3+ (z =0.1, 0.25, 0.5, 1.0, 2.0 3.0 and 4.0 mol%). A significant increase in lifetime values and fluorescence quantum efficiencies is observed upon addition of fluorine and consecutive substitution of oxygen in the first coordination sphere of RE, as confirmed by 19F NMR. The latter also turns out to be very useful for quantifying fluoride losses during the synthesis and differentiating between P- and Al-bonded fluorine species. Furthermore, systematic compositional changes in the network structure have been monitored by 31P, 27Al single resonance as well as 31P(19F), 31P(27Al), 27Al(19F), 27Al(31P) double resonance NMR leading to a comprehensive structural description of the system. Besides the throughout characterization of near-infrared emissions at 1.0 and 1.55 µm, the favorable energy transfer between Yb3+ and Er3+ was also investigated in the visible (infrared to green and red upconversion) ranges.

Andrea de Camargo is a Bachelor (1996) and Master (1999) in Chemistry and got her PhD degree in Applied Physics at the Physics Institute of São Carlos, University of São Paulo, Brazil (2003). In 2006 she became Assistant Professor of Physics at the same institute. From 2008-2011 she worked at the Westfaelisches Wilhelms Universitaet Muenster in Germany, as an Alexander von Humboldt Fellow and then CNPq Postdoctoral Fellow. Since her return to São Carlos she has been working on the consolidation of her research group dedicated to design, synthesis, spectroscopic investigations and structural-functional correlations of luminescent and optical materials (rare-earth doped glasses and glass ceramic for laser applications, mesoporous silicates incorporated with highly luminescent molecular species, luminescent nanoparticles, etc). She is one of the principal investigators of CeRTEV – Center for Research, Technology and Education in Vitreous Materials, a joint initiative to establish an Excellence Center in Glass Science and Technology in São Carlos. In 2007 she was granted the prize L’OREAL for Women in Science, Brazil, and subsequently the CNPq Research Productivity Fellowship, which she still holds. In 2008 she became affiliated member of the Brazilian Academy of Sciences. She has published over 50 papers and advised 3 PhDs and 4 MS thesis.

For additional information:
Dr. Leonid B. Glebov


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