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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 10 Issue 1 (2005) pp 29-35

The Influence of Oxygen on the Lifetime of Luminescent Probes. A Simple Device for Degassing Solutions for Fluorescence Measurements

Joăo Seixas de Melo

Chemistry Department, University of Coimbra, 3004-535 Coimbra, Portugal, sseixas@ci.uc.pt
Received June 9, 2004. Accepted December 14, 2004.

Published online: 18 January 2005

Abstract. The lifetime of an emissive species is one fundamental characteristic associated with its emission. It is sensitive to the presence of quenchers, in particular oxygen dissolved in the solvent. Degassing solutions (by removing or replacing of oxygen with another gas) is a critical experimental procedure for time-resolved fluorescence studies. It is generally considered that oxygen is a strong quencher of fluorescent probes, in particular of those with long lifetimes. We wish to show the importance of efficient deoxygenation for luminescence measurements and, in addition, to introduce a simple device for conducting this procedure. This can replace the use of freeze–pump–thaw cycles in vacuum-sealed cuvettes, avoiding both working with high-vacuum conditions and handling low-temperature systems. The simple design of the fluorescence cell consists of two Teflon stopcocks with a ring-sealed immersion tube and a fitting for a purging gas. The cuvette is novel and is useful in various situations, particularly those where stringent degassing is required. The effect of variable oxygen concentrations on the fluorescence decays is described and some common examples are used to illustrate this point and to test the reliability of the fluorescence lifetimes obtained with the device. The control of this variable is important for any type of experiment involving fluorescence.

Key Words: Laboratories and Demonstrations; physical chemistry; fluorescence; photochemistry; fluorescent probes; luminescence

(*) Corresponding author. (E-mail: sseixas@ci.uc.pt)

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Issue date: February 1, 2005

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