Date of Award

12-2002

Level of Access

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Howard H. Patterson

Second Committee Member

Carl P. Tripp

Third Committee Member

François G. Amar

Abstract

Exciplex tuning and optical memory behavior of [Ag(CN)2-] and [Au(CN)2-] ions doped in KCl host crystals, pure KAg(CN)2, and pure KAU(CN)2 have been studied. Additionally, d10-d10 (KAu(CN)2-KAg(CN))2) and d10-d8 (KAu(CN)2, KAg(CN)2- K2Pt(CN)4) mixed metal systems have been synthesized and characterized. Several ultraviolet and visible emission bands are observed for [Ag(CN))2-] and [Au(CN)2-] ions doped in KC1 host crystals. Each emission band becomes dominant at a characteristic excitation wavelength: that is the energy of the emission can be tuned by site-selective spectroscopy. Luminescence, Raman and theoretical results suggest the formation of Au-Au and Ag-Ag bonded excimers and exciplexes between adjacent [Ag(CN))2-] and [Au(CN))2-] ions in the host lattice. The emission and Raman bands are assigned to different [Ag(CN))2-]n, and [Au(CN))2-]n, exciplexes. These results give rise to a new optical phenomenon called "exciplex tuning". When a single crystal of [Ag(CN))2-]/KCl at 77 K is irradiated with 266 nm laser light, the intensity of the high energy peak at 338 nrn is increased with increasing exposure time and, concurrently, the intensity of the low energy peak at 415 nm is decreased. This process is reversible; that is, heating the crystal to room temperature restores the crystal to its original state. This phenomena of "optical memory" and erasure of the optical memory has been studied for both [Ag(CN))2-] ions and [Au(CN)2-] ions doped with varying concentrations in KCl as well as with pure KAg(CN)2 and pure KAu(CN)2 single crystals. The d10-d10 mixed metal system (KAu(CN)2-KAg(CN)2) shows Ag-Au delocalization in the lowest energy excited electronic state. Observed luminescence in this d10-d10 mixed system is strongly tunable; that is, the emission energy of this system can be tuned by varying physical parameters such as excitation wavelength, temperature, and the Ag/Au ratio. The d10-d8 mixed metal system (KAu(CN)2, KAg(CN)2-K2Pt(CN)4) represents an example of energy transfer between dl0 and d8 systems. In other words, the lowest excited state energy of KAu(CN)2 or KAg(CN)2 can be transferred to the lowest excited state of K2Pt(CN)4).

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