Chemico-Physical Characterization of Quinizarin Thin Films Deposited by Evaporation

Abstract

Quinizarin (1,4-DHAQ) thin films deposited under vacuum were investigated by IR absorption, X-ray diffraction, nuclear magnetic resonance (NMR), optical absorption, electron spectroscopy for chemical analysis elemental analysis (XPS), and scanning electron microscopy and melting point measurements. It was found that amorphous quinizarin thin films are obtained. IR absorption spectra, ion mass spectroscopy, and NMR spectra show that there is no decomposition during the deposition of the film, the quinizarin powder being sublimated under vacuum from a tantalum boat sustained at T = 418 K. In addition, elemental analysis and melting point measurements demonstrate that the deposition process is also a purifying process of the quinizarin. SEM microphotographs show that continuous, smooth thin films may be obtained when they are deposited at a sufficiently slow rate. XPS analysis shows that, after decomposition of the peak spectra, the O 1s peak is composed of two different components corresponding to the oxygen bonded in the carbonyl and the hydroxyl groups. In the case of the C 1s peak, the main component corresponds to the carbon of the cycle, while it was not possible to discriminate between the carbonyl and hydroxyl bonds, perhaps because of the hydrogen bond between these two groups. The presence of an absorption band around 480 nm in the optical absorption confirms the hydrogen bond between the hydroxyl and carboxyl in the 1,4-DHAQ. Optical absorption of an Ag/DHAQ structure shows that a complex may be obtained by annealing.