Department of Physics
Graduate Thesis Defense Announcement
Apr 24, 2013
Speaker: Akinloluwa Olumoroti
Date: Tuesday, April 30, 2013
Time: 2:00 pm
Room: 336 Currens Hall
Effect of Silver Nanoparticles on the Fluorescence of Pb2+ and Compositional Dependence of Sm3+ Fluorescence in Borate Glasses
Borate glasses have been widely studied due to their good optical and mechanical properties. Lead and bismuth (PbO/Bi2O3:B2O3) borate glasses belong to a family of heavy metal oxide (HMO) glasses which are well known to be chemically durable, stable against atmospheric moisture, have low melting temperatures and good corrosion resistance. The first part of this work deals with lead borate glasses with silver nanoparticles (NPs) introduced into the glass matrix. Transmission electron microscopy characterization is done to verify the nucleation of NPs. Fluorescence and optical absorption experiments are then carried out after different heat treatment duration to investigate the influence of silver NPs on the optical properties of lead (Pb2+) by comparing with a glass sample without silver NPs. Optical absorption experiments show that a well-defined surface plasmon resonance (SPR) peak due to Ag NPs can be observed only for samples that were annealed for 36 hrs. Pb2+ fluorescence spectra reveal that the presence of silver NPs creates new emission centers for Pb2+ ions by altering their chemical environment.
The second part of the work involves the use of samarium (a rare earth ion) as dopant in lead and bismuth borate glasses. The concentration of samarium (Sm3+) is fixed and the base glass composition is varied. The goal is to investigate the compositional dependence of optical properties of samarium in the base glass (PbO/Bi2O3:B2O3). Optical absorption spectra have been collected and the oscillator strength of each transition - including the hypersensitive- is obtained. Optical absorption edge is found to shift toward lower energies with increasing PbO/Bi2O3 concentration. Both the oscillator strength and the peak position of the hypersensitive transition show significant variation with glass composition. Strong interaction between Sm3+ ions and Pb2+/Bi3+ ions can also be seen from the variations in the fluorescence emission properties of Sm3+ as a function of base glass composition.
Studying the variation of these optical properties will help to create the optimum rare-earth ion-host configuration for possible technological applications. This is the thrust of our future investigations of these glass systems.