Richard Krumpolec

The plasma-activated gas is capable of decontaminating surfaces of different materials in remote distances. The effect of plasma-activated water vapor on Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli biofilm contamination was investigated on the polypropylene nonwoven textile surface. The robust and technically simple multi-hollow surface dielectric barrier discharge was used as a low-temperature atmospheric plasma source to activate the water-based medium. The germicidal efficiency of short and long-time exposure to plasma-activated water vapor was evaluated by standard microbiological cultivation and fluorescence analysis using a fluorescence multiwell plate reader. The test was repeated in different distances of the contaminated polypropylene nonwoven sample from the surface of the plasma source. The detection of reactive species in plasma-activated gas flow and condensed activated vapor, and thermal and electrical properties of the used plasma source, were measured. The bacterial biofilm decontamination efficiency increased with the exposure time and the plasma source power input. The log reduction of viable biofilm units decreased with the increasing distance from the dielectric surface.

We present a novel method of surface processing of complex polymer-metal composite substrates. Atmospheric-pressure plasma etching in pure H₂, N₂, H₂/N₂ and air plasmas was used to fabricate flexible transparent composite poly(methyl methacrylate) (PMMA)-based polymer film/Ag-coated Cu metal wire mesh substrates with conductive connection sites by the selective removal of the thin (~10–100 nm) surface PMMA layer. To mimic large-area roll-to-roll processing, we used an advanced alumina-based concavely curved electrode generating a thin and high-power density cold plasma layer by the diffuse coplanar surface barrier discharge. A short 1 s exposure to pure hydrogen plasma, led to successful highly-selective etching of the surface PMMA film without any destruction of the Ag-coated Cu metal wires embedded in the PMMA polymer. On the other hand, the use of ambient air, pure nitrogen and H₂/N₂ plasmas resulted in undesired degradation both of the polymer and the metal wires surfaces. Since it was found that the etching efficiency strongly depends on the process parameters, such as treatment time and the distance from the electrode surface, we studied the effect and performance of these parameters.

This study solves the problem of the invasivity of laser‐induced fluorescence (LIF) measurements caused by photodissociation. It is shown with the example of OH LIF that the excess signal caused by laser‐induced photodissociation can be distinguished from the true LIF signal of the naturally presented species by its different dependence on the energy of laser pulses. This fact can be further used for the detection of photodissociable species not accessible by the standard LIF. This method is applied to OH radicals in atmospheric‐pressure multihollow dielectric barrier discharge plasma ignited in a number of holes. OH radicals are concentrated at the effluents of these holes, but they are able to spread to a distance of 5 mm, meaning that the discharge is suitable for the treatment of distant and rough surfaces.

Three cyclic silylselenides were prepared in a straightforward manner. Property tuning has been achieved by varying the ring size and the number of embedded selenium atoms. All silylselenides possess improved resistance towards moisture and oxidation as well as high thermal robustness and sufficient volatility with almost zero residues. The six‐membered diselenide proved to be particularly superior Se precursors for atomic layer deposition and allowed facile preparation of MoSe₂ layers. Their structure and composition have been investigated by Raman and X‐ray photoelectron spectroscopy as well as scanning electron microscopy revealing vertically aligned flaky shaped nanosheets.

Spatially resolved concentration of ozone has been determined in the near afterglow of a novel atmospheric multi-hollow barrier discharge using photofragmentation laser-induced fluorescence (LIF). The method consists of two steps: (i) photodissociation of ozone; (ii) predissociation LIF of the O₂ fragment via the O₂ (B ³Σ^-_u, v'=0 ← X ³Σ^-_g, v''=6) transiton. Both processes happen during the same laser pulse requiring the same excitation wavelength (248nm). The fluorescence signal has been calibrated by infrared absorption. The method allows in-situ observation before the afterglow chemistry significantly affects the O₃ concentration and is capable to reveal inhomogeneous ozoned distributions in the reactor.

The authors have used sequential pulsed vapor deposition to prepare thin films of copper(I) chloride (CuCl) on silicon. The films are nanocrystalline and show a very strong ultraviolet luminescence. The excitonic response and corresponding luminescent properties make these films promising for new short-wavelength photonic/photoelectronic devices. The authors have undertaken systematic studies of these films, using the potential of multiple-angle-of-incidence spectroellipsometry with a rotating compensator, normal-incidence reflectance with small illuminated spots, and photoluminescence with high spatial resolution. The silicon substrate presents specific problems in the interpretation of the ellipsometric and reflectance spectra, as the excitonic multiplets of CuCl are close to the E1 interband spectral structure of Si. The authors discuss appropriate procedures to isolate the response of the thin films. In addition, since the coverage of the substrates typically shows inhomogeneity, care has to be taken in accounting for its presence. A consistent picture of the passive and active excitonic response of the films results from the multitude of experimental techniques used.

This study concerns a low‐temperature method for dry hydrogen plasma reduction of inkjet‐printed flexible graphene oxide (GO) electrodes, an approach compatible with processes envisaged for the manufacture of flexible electronics. The processing of GO to reduced graphene oxide (rGO) was performed in 1–64 s, and sp²/sp²+sp³ carbon concentration increased from approximately 20 % to 90 %. Since the plasma reduction was associated with an etching effect, the optimal reduction time occurred between 8 and 16 s. The surface showed good mechanical stability when deposited on polyethylene terephthalate flexible foils and significantly lower sheet resistance after plasma reduction. This method for dry plasma reduction could be important for large‐area hydrogenation and reduction of GO flexible surfaces, with present and potential applications in a wide variety of emerging technologies.