Plasma Processes and Polymers

Cover: Copper nanoparticles were made by the interaction of an argon plasma with copper species in an ionic liquid. The electrons of the free plasma reduce the dissolved metal cations at the plasma IL interface (see schematic drawing). The TEM image shows the generated nanoparticles. Further details can be found in the article by N. Kulbe, O. Höfft, A. Ulbrich, S. Zein El Abedin, S. Krischok, J. Janek, M. Pölleth, and F. Endres^*on page 32.

This commentary addresses the contents of an essay by M. Strobel and C. S. Lyons bearing the title ‘An essay on contact angle measurements’; it is also in response to the Editors' call for a discussion on contact angle measurements in general among the readership of Plasma Processes and Polymers.

The information that could be derived from contact angle measurements is very useful to characterize the outermost layer of a surface until it is carried out carefully. To compare the results with other working groups it is essential to describe the measurement procedure properly.

The conversion of methane and carbon dioxide into more useful chemicals is an important research topic. In the present paper, we discuss a multi-diagnostic investigation on the synthesis of liquid compounds by reforming methane with CO₂ in a dielectric barrier discharge at atmospheric pressure.

Ionic liquids (IL) are electrolytes with a very low vapour pressure, therefore the generation of stable plasmas above the liquid surface is possible. This free plasma electrode could reduce dissolved metal cations at the plasma IL interface. The generated metal atoms could then form nanoparticles. In this paper we present our investigations on the growth of copper nanoparticles due to the interaction of an argon plasma with CuCl (CuCl₂) ionic liquid solutions.

Two different components emanating from a microplasma jet are identified: (i) a particle-based source which spreads from the orifice of the jet and (ii) a photon source, which is highly directional. A variety of microplasma jet operational parameters were adjusted to control both components, which influenced the expansion and nature of surface modification over microscopic areas of a polymer substrate.

Etch rates of up to 300nm·s⁻¹can be achieved using an atmospheric pressure plasma jet operating with argon and 1% oxygen admixture. Concerning the potential application of the plasma jet in biofilm removal, the etching of structurally different polymers, that represent model compounds of cell constituents, are examined. A comparison is made between argon plasma and argon with different oxygen admixtures.

In this paper, a novel procedure is explored aiming at the deposition of antibacterial coatings. SEM imaging and antibacterial tests demonstrate that the introduction of a precursor into an atmospheric pressure plasma equipment results into the homogeneous deposition of antibacterial layers. The retained antibacterial activity shows up to a 99.9999% reduction of E. coli after 24h of incubation.

Sterilization of specifically coated surfaces for cell growth by plasma can lead to loss of growth promoting properties. In this paper, a development is presented for the sterilization of microtiterplates by corona-dielectric barrier discharge plasma at atmospheric pressure. Moreover this procedure does not affect cell adhesive coatings like collagen I and poly-D-lysine.

Amino-functional films with a high content of primary amino groups (up to 5.5%) were deposited, using an atmospheric pressure plasma jet. Results for the comparison of this process for two different precursors and gaseous environments are presented and first considerations regarding the polymerisation reaction are given, reflecting the various observed dependencies on the process parameters.