Natural Science Seminar, January 29

Join Dr. José A. Jiménez, Postdoctoral Research Associate, for a free talk in the Soo Bong Chae Auditorium on Friday, January 29, at 3:30 pm.  Dr. Jiménez’s talk is entitled “Optical Interactions and Energy Transfer Processes in Silver Nanocomposite Glasses.” This event is free and open to the public. For more information, visit the Natural Science Seminar website.

Glasses doped with noble metals are currently an attractive area of research from both fundamental and applied perspectives, especially due to the remarkable optical properties of metallic nanoparticles (NPs). In this talk, recent experimental results on optical interactions and energy transfer processes in silver-doped aluminophosphate glasses prepared by melting and heat treatment processes will be presented. The presentation will focus on: (i) optical properties of silver species in different oxidation and aggregation states and energy transfer processes between them; (ii) the influence of metallic species on rare-earth (RE) ions photoluminescence (PL); and (iii) relaxation processes involving Ag NP-host interactions following optical excitation. A novel finding regarding (i) is that PL owing to plasmon resonance energy transfer (PRET) from Ag NPs to luminescent species is observed for the first time. The excitation of ionic silver species via PRET from Ag NPs is interpreted as arising from an Ag NP → Ag+-Ag0 → Ag+-Ag+ energy transfer scheme. The spectroscopic properties of RE ions in the glass system were studied in order to address (ii), where an intensification of Eu3+ emission is observed for non-resonant UV excitation owing to photon reabsorption from single Ag+ ions and twofold-coordinated Sn centers emission. However, thermal processing of the glasses leads to formation of Ag NPs and a quenching effect on RE PL which is ascribed to excitation energy transfer to the silver particles. Concerning (iii), an important finding is that an uncommon relaxation is observed in degenerate four-wave mixing experiments which is assigned to energy transfer from polaronic and/or excitonic states in the near-interface region of the glass matrix to Ag NPs. A faster monotonic relaxation is observed for Ag nanocomposites showing indications of the accumulation of Ag+-Ag0 dimers at or near NPs surface which is consistent with PRET.