A Thermoluminescence Study of Bio-Organic Compounds Adsorbed in a Clay Mineral

Clay minerals have been implicated as a probable active surface for pre-biological chemical reactions occurring during the early evolution of the Earth. In this context, it is very important to explain the role of these surfaces and how much a solid is involved in the chemical transformation that is taking place at its surface. The aim of this work is to present experimental results from the ultraviolet spectroscopy and thermoluminescence behavior of samples of adenine and poly A, nucleic acid components, adsorbed in a clay mineral (Na-montmorillonite) and irradiated with gamma rays. The results obtained show that both compounds are adsorbed readily in the clay. The TL response of the samples showed that there are differences depending on whether the adsorbate is present, and it is pH dependent. In the system under study, the recovery of adenine from the adenine-clay system was much higher than in a homogeneous phase, in which the survival of the adsorbed molecule versus doses was low. A decrease in the TL signal is observed probably because adenine interfere with the recombination of the electrons with the hole trapped and reduce the presence of sites that induce luminescence emission to the aluminum-hole centers. This is of particular interest because there are modes of energy transfer across interfaces that do not exist in homogeneous phases.