Chitosan–Hydroxyapatite Composite Layers Generated in Radio Frequency Magnetron Sputtering Discharge: From Plasma to Structural and Morphological Analysis of Layers

Abstract

Chitosan–hydroxyapatite composite layers were deposited on Si substrates in radio frequency magnetron sputtering discharges. The plasma parameters calculated from the current–voltage radio frequency-compensated Langmuir probe characteristics indicate a huge difference between the electron temperature in the plasma and at the sample holder. These findings aid in the understanding of the coagulation pattern of hydroxyapatite–chitosan macromolecules on the substrate surface. An increase in the sizes of the spherical-shape grain-like structures formed on the coating surface with the plasma electron number density was observed. The link between the chemical composition of the chitosan–hydroxyapatite composite film and the species sputtered from the target or produced by excitation/ionization mechanisms in the plasma was determined on the basis of X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and residual gas mass spectrometry analysis.

The Effects of Electron Beam Irradiation on the Morphological and Physicochemical Properties of Magnesium-Doped Hydroxyapatite/Chitosan Composite Coatings

“…The surface of the unirradiated layer is smooth, and its pattern (see caption inserted in Figure 1a), is due to the polymeric molecules sputtered from the target (during the deposition process in the rf magnetron discharge) that condensate when they reach the substrate. In comparison with our previous results regarding the deposition of HApCs layers in similar experimental conditions [13], the adding of Mg into the composition of the sputtering target and the increasing of applied rf power lead to the smoothing of the layer surface [13]. In Figure 1c,e are presented the SEM images that illustrate the topography of the surfaces of MgHApCs coatings after irradiation with electron beams of 2 and 50 Gy radiation doses.…”

“…The layer thickness was calculated to be ~300 nm from the deposition rate measurements performed by using a quartz microbalance (acquired from INFICON Holding AG Company, Bad Ragaz, Switzerland) positioned on the holder substrate in the central position relative to the magnetron source. Additional details about the deposition technique, experimental set-up and deposition rate measurements can be found in [13,14].…”

“…P 2p3/2 and P 2p1/2 XPS peaks are slightly changed in the 2 Gy and 50 Gy irradiated samples. Nevertheless, the 0.8 eV difference between P 2p3/2 and P 2p1/2 XPS peaks [13,34] is maintained as an indication that the exposure to ionizing radiation does not destroy the apatite structure of the samples.…”

“…Chitosan hydroxyapatite composite coatings are produced on various substrates by the following physical and chemical methods: electrophoretic deposition [10], spin coating technique [11], plasma spraying [12], electrochemical deposition [10] or radiofrequency magnetron sputtering discharges [13,14]. In our previous papers [13,14], we produced hydroxyapatite based layers by the radio frequency magnetron sputtering technique using sputtering targets composed of calcium phosphate [14], HAp doped with Ce 3+ [15] and Sm 3+ ions [16] or HAp synthesized with chitosan powders [13]. In the present study, we have shown that magnesium doped hydroxyapatite/chitosan composites layers can also be generated in radio frequency magnetron sputtering discharge.…”

Electrical Supply Circuit for a Cold Plasma Source at Atmospheric Pressure Based on a Voltage Multiplier

“…In the case of the experimental samples, containing new materials, biopolymers or living cells, the plasma gas temperature must be maintained as low as possible and, if necessary, progressively increased after a few preliminary tests. As an example, chitosan is one of the polymers intensively studied due to its multiple potential uses [ 32 , 33 , 34 , 35 ]. According to [ 33 ], during thermal processing, chitosan goes through two or three degradation stages, the first of them occurring at 30–110 °C.…”