We are presenting recent advances in surface functionalization of materials such as functional polymers using gaseous plasma treatments. Functionalization is a result of chemical interaction between solid materials and reactive plasma species including charged particles, neutral radicals, excited species and UV radiation. The degree of surface functionalization depends on the type of polymers and fluxes of reactive plasma species. An appropriate choice of plasma parameters thus enables almost arbitrary tailoring of the surface wettability. This review paper gives a brief introduction to the formation of reactive gaseous species upon plasma conditions in different discharge configurations and describes plasma-surface interaction with an emphasis on the differences between different reactive plasma species. Analysis of the relevant literature is given and correlations between treatment parameters and surface finish are drawn. Numerous authors have used plasma treatment for modification of the surface functionalities, however, the obtained surface properties often differ even for the same materials. The reason for such diverse results is the application of various gaseous discharges for plasma generation. Apart from the type and amount of functional groups induced by plasma treatment, the surface functionality depends also on the surface morphology on the sub-micron scale; therefore, this effect is stressed as well. Finally, some future guidelines are given.

A suitable technique for localized surface treatment of solid materials is an atmospheric pressure plasma jet (APPJ). The properties of the APPJ plasma often depend on small details like the concentration of gaseous impurities what influences the surface kinetics. The simplest and often most useful configuration of the APPJ is presented, characterized by optical emission spectroscopy (OES), and results are discussed in view of various papers. Furthermore, results of additional recent papers on the characterization of the APPJ by OES are presented as well. Because the APPJ is operating at atmospheric pressure, even the water vapor traces may significantly alter the type and concentration of reactive species. The APPJ sustained in noble gases represents a source of vacuum ultraviolet (VUV) radiation that is absorbed in the surface of the treated material, thus causing bond scission. The addition of minute amounts of reactive gases causes significant suppression of VUV radiation and the formation of reactive radicals. These radicals such as OH, O, N, NO, O₃, and alike interact chemically with the surface causing its functionalization. Huge gradients of these radicals have been reported, so the surface finish is limited to the area reached by the radicals. Particularly OH radicals significantly prevail in the OES spectra, even when using very pure noble gas. They may cause suppression of other spectral features. OH radicals are especially pronounced in Ar plasmas. Their density decreases exponentially with a distance from the APPJ orifice.

Methods for synthesizing nitrogen-doped graphene-like materials have attracted significant attention among the scientific community because of the possible applications of such materials in electrochemical devices such as fuel cells, supercapacitors and batteries, as well as nanoelectronics and sensors. The aim of this paper is to review recent advances in this scientific niche. The most common synthesis technique is nitridization of as-deposited graphene or graphene-containing carbon mesh using a non-equilibrium gaseous plasma containing nitrogen or ammonia. A variety of chemical bonds have been observed, however, it is still a challenge how to ensure preferential formation of graphitic nitrogen, which is supposed to be the most favorable. The nitrogen concentration depends on the processing conditions and is typically few at.%; however, values below 1 and up to 20 at.% have been reported. Often, huge amounts of oxygen are found as well, however, its synergistic influence on N-doped graphene is not reported. The typical plasma treatment time is several minutes. The results reported by different authors are discussed, and future needs in this scientific field are summarized. Some aspects of the characterization of graphene samples with X-ray photoelectron spectroscopy and Raman spectroscopy are presented as well.