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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 8 Issue 4 (2003) pp 251-256

Room-Temperature Phosphorescence (RTP) in Aqueous Solutions. An Advanced Undergraduate Laboratory Experiment

Graciela M. Escandar*, and Arsenio Muñoz de la Peña*,

Departamento de Química Analítica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531 (2000) Rosario, Argentina,, and Departamento de Química Analítica, Universidad de Extremadura, 06071 Badajoz, España,
Received March 11, 2002 Accepted April 20, 2003

Published online: 28 June 2003

Abstract. This paper presents a detailed description of the steps and conditions required to obtain room-temperature phosphorescence signals in aqueous solution. A complete laboratory experiment, designed to familiarize students with the uses of this type of spectroscopic signal and, at the same time, the application of computational methods (model fitting and parameter estimation) to obtain relevant thermodynamic results, is described. The experiment involves the measurement of the phosphorescence spectra of acenaphthene (used as a model system) at room temperature through the formation of inclusion complexes with b- and g-cyclodextrins, the determination of the inclusion-constant value for the g-cyclodextrin complex, and the measurement of phosphorescence lifetimes. The presence of 2,3-dibromopropanol with heavy atoms is necessary in order to obtain the RTP emission. Deoxygenation with sodium sulfite is necessary in the case of b-cyclodextrin, but not in the case of g-cyclodextrin. A comparison between the phosphorescence intensity obtained in the presence of cyclodextrins with that from a system without cyclodextrin in a concentrated solution of potassium iodide deoxygenated with sodium sulfite is also presented and discussed.

Key Words:  Laboratories and Demonstrations; physical chemistry; thermodynamics

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Issue date: August 1, 2003

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