The analysis of the gas phase chemistry of a cold atmospheric plasma is a fundamental step for a more thorough understanding of the effects it can induce on target substrates. This work aims at investigating, by means of optical spectroscopic techniques, the kinetics of O 3 , NO 2 and NO 3 produced by a Surface Dielectric Barrier Discharge. The phenomenon of discharge poisoning (or ozone quenching) in static ambient air was investigated varying the electrical power density applied to the plasma source. Kinetics of the reactive oxygen and nitrogen species production were obtained by means of time resolved UV/VIS optical absorption spectroscopy and highlighted how the discharge poisoning takes place once the applied power density ovecomes a critical value of 0.11 W cm −2 . An ozone-enriched atmosphere (with a maximum O 3 density around 3000-4000 ppm) is thus obtained when the source is operated below the critical power density, while a NO x -enriched atmosphere (highest concentrations of NO 2 around 1250 ppm and NO 3 around 35 ppm) is obtained at higher applied power densities. Moreover, since the production of NO, one of the most important quenchers of O 3 , is directly related to the vibrational energy of nitrogen molecules, the vibrational population of N 2 , determined by processing emission spectra of N 2 (B→C) band, was studied. Finally, considerations regarding both the energy cost of production of a reactive oxygen species and reactive nitrogen species atmosphere and the possibility of on-line monitoring its chemical composition, were presented in order to emphasize the potential of optical absorption spectroscopy techniques for the on-line control of plasma assisted industrial processes.

In the present work, a polydiagnostic study of an atmospheric pressure plasma jet specifically designed for the deposition of coatings by using an Ar/tetraethyl orthosilicate (TEOS) mixture is undertaken. Both passive and active diagnostic methods are utilized to shed light on the complexity of gas-phase mechanisms of precursor fragmentation. A detailed characterization is performed by (fast imaging) optical emission spectroscopy (OES) to clarify the spatial-temporal behavior of excited species. The influence of the TEOS admixture on gas temperature is studied by OES and Rayleigh scattering techniques. The evolution of streamers and their influence on radical formation in the treatment zone is also discussed. K E Y W O R D Sactive species, laser scattering, plasma diagnostics, plasma jet, plasma polymerization

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The key processes in an atmospheric‐pressure plasma jet containing Ar and tetraethyl orthosilicate (TEOS) are studied by means of two‐dimensional imaging of the important discharge radicals: OH, CH, and atomic O. The kinetics of the species generation is investigated by laser‐induced fluorescence spectroscopy. The work is focused on the behavior of the ground‐state radicals' density as a function of the applied voltage and of the Ar/TEOS mixing ratio. First insights on the physicochemical mechanisms of precursor fragmentation are provided. The influence of precursor admixture and precursor fragmentation on the OH, CH radicals, and atomic oxygen kinetics is revealed. The dominant role of gas‐phase oxidation processes in CH radical formation and polymerization is discussed and analyzed.

One interesting category of nano‐ and micro‐engineered surfaces is surface gradients, which allow the controlled optimization of biointerfaces at a small scale in an extended area length. Plasma coatings offer a large diversity of functionalities at the nanoscale, accompanied by high chemical stability and adhesion on a variety of substrates at ambient temperature. Atmospheric‐pressure plasma‐assisted deposition could be employed for the generation of surface gradients on thermosensitive materials. In this study, a corona plasma jet is used to deposit polydimethylsiloxane/SiO2‐like surface gradients on polyethylene foil by varying the O2 concentration in the discharge during the movement of the plasma source. We obtained, in a single‐step approach, gradient coatings along a length of ∼10 cm, with a gradual variation of both chemistry and surface energy.