Immobilization of Chitosan Onto Polypropylene Foil via Air/Solution Atmospheric Pressure Plasma Afterglow Treatment

Plasma Chemistry and Plasma Processing - The combination of an atmospheric pressure plasma afterglow operated in air with wet grafting was utilized for the immobilization of chitosan on the surface...     

Kinetics and Mechanism of Cr(VI) Reduction in a Water Cathode Induced by Atmospheric Pressure DC Discharge in Air

The process of reduction of Cr⁶⁺ ions (solution of potassium dichromate, K₂Cr₂O₇) in a water cathode was studied during a DC discharge in air. The concentration range of Cr⁶⁺ was (5.7–19) ×10^?5 mol/l and discharge current range was 20–80 mA. Cr⁶⁺ ions were shown to be reversibly reduced under a discharge action. The equilibrium degree of reduction increased with increasing initial concentration of the solution at fixed discharge current. At fixed initial concentration the reduction degree increased with increasing discharge current. The reduction degrees so obtained were 0.34–0.84. A kinetic scheme of the processes taking place in a solution was proposed. The calculated data obtained as a result of application of this scheme described well the experimental results on Cr⁶⁺ kinetics. The main processes of Cr⁶⁺ reduction and Cr³⁺ oxidation were revealed. HO ₂ ^· radicals and hydrogen peroxide were shown to be responsible for Cr⁶⁺ reduction whereas ^·OH radicals and O₂ molecules provide the reverse process of Cr³⁺ oxidation to Cr⁶⁺. The mechanism of action of phenol additives improving the process efficiency is discussed. The efficiency of phenol action as a radical scavenger was shown to be determined with its mass-transfer to the reaction area rather than chemical reaction rate.     

Synthesis and microstructure investigation of heterogeneous metal-plasma polymer Ag/HMDSO nanoparticles

Metal-polymer nanocomposites have gained increasing attention due to the wide potential applications field. Synthesis of nanoparticles from the gas phase is an intensively studied alternative to the chemical preparation methods. We present a one-step procedure that combines magnetron-based gas aggregation cluster source of silver nanoparticles and simultaneous plasma-enhanced chemical vapour deposition of hexamethyldisiloxane (HMDSO). The key parameter of the process, significantly influencing the morphology and microstructure of studied nanoparticles, was found to be the amount of HMDSO added to the deposition chamber as witnessed by small angle X-ray scattering and X-ray diffraction methods combined with transmission electron microscopy and UV–Vis spectrophotometry. The presence of HMDSO in the chamber leads to changes in the size distribution and also in the architecture of prepared nanoparticles. The increasing amount of HMDSO induces the formation of individual core-shell nanoparticles, chains of core-shell nanoparticles, and for the highest concentration of HMDSO, the synthesis of multi-core-shell nanoparticles. The size of crystallites in the silver cores of nanoparticles decreases with addition of HMDSO, which prevents further aggregation.     

Mechanistic studies of plasma polymerization of allylamine

Plasma polymerization of allylamine is performed both in continuous wave and pulsed mode. Chemical derivatization is applied to determine primary and secondary amine concentration. Primary amines are efficiently formed, but secondary amines are more abundant. A polymerization mechanism is proposed to account for the difference in amine content obtained from comparison between continuous wave and pulsed mode plasma polymerization. The AFM measurements performed on ultrathin (1-10 nm) plasma polymers confirm the continuity of films and that the film growth on silicon occurs via a layer-by-layer mechanism because no islandlike structures were detected.     

SPM analysis of fibrinogen adsorption on solid surfaces

The adsorption kinetics, adhesion and orientation of human fibrinogen on solid surfaces have been studied by surface probe microscopy (SPM) and quartz crystal microbalance techniques (QCM). CF₃-, NH₂-terminated organo-silane self-assembled monolayers (SAM) and OH-terminated silicon dioxide have been used as model surfaces. Furthermore, the interaction of fibrinogen with nanocomposite Ti/hydrocarbon plasma polymer films (Ti/ppCH) deposited by dc magnetron sputtering has also been studied.     

Plasma Jet and Dielectric Barrier Discharge Treatment of Wheat Seeds

Plasma Chemistry and Plasma Processing - Low-temperature plasma treatment of wheat seeds was performed by a plasma jet and dielectric barrier discharge, both at atmospheric pressure. The influence...     

Nucleation and Growth of Magnetron-Sputtered Ag Nanoparticles as Witnessed by Time-Resolved Small Angle X-Ray Scattering

Kinetic aspects of the synthesis of Ag nanoparticles (NPs) by magnetron sputtering are studied by in situ and time-resolved small angle X-ray scattering (SAXS). Part of the NPs are found to become confined within a capture zone at 1–10 mm from the surface of the target and circumscribed by the plasma ring. Three regimes of the NP growth are identified: 1) early growth at which the average NP diameter rapidly increases to 90 nm; 2) cycling instabilities at which the SAXS signal periodically fluctuates either due to expelling of large NPs from the capture zone or due to the axial rotation of the NP cloud; and 3) steady-state synthesis at which stable synthesis of the NPs is achieved. The NP confinement within the capture zone is driven by the balance of forces, the electrostatic force being dominant. On reaching the critical size, large NPs acquire an excessive charge and become expelled from the capture zone via the electrostatic interactions. As a result, significant NP deposits are formed on the inner walls of the aggregation chamber as well as in the central area of the target.