DNA-CTMA complex for applications in organic electronics: Thermal annealing phenomena

Recently, thin films of micron and sub-micron thickness, prepared from deoxyribonucleic acid (DNA) in complex with cetyltrimethyl ammonium chloride have been frequently reported as components of different electronic/optoelectronic devices. However, little researchers reports on repeatability of overall properties of this material in solid form. This paper discuss thermal stability of DNA-lipid films. Thin films, prepared from solutions, were studies by UV-vis-NIR spectroscopic ellipsometry, broadband dielectric spectroscopy and X-ray diffractometry. It was found that heating results in an irreversible transition to another structural form, different from the initial. Many features of dependence the recorded spectra on temperature prove, that the double helix of DNA splits into separate strands. Contrary to behaviour known from solution, upon cooling single strands never rearrange entirely in the double helix. This is not a sharp phenomenon, but rather Arrhenius type dependence. Similar conclusions can be drawn from measurements done for bulk samples using X-ray diffractometry.