Preliminary Positron Lifetime Results on Free Volumes in Cyclodextrins

Abstract:

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.

• Periodical: Materials Science Forum (Volume 666)
• Pages: 99-102
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.666.99
• Online since: December 2010
• Authors: Maria Fatima Ferreira Marques, A.M.G. Moreira Da Silva, P.M. Gordo, Z. Kajcsos
• Keywords: Cyclodextrin, Free Volume, Inclusion Complex, Positron Lifetime

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