Approaches to Inactivating Aflatoxins—A Review and Challenges

According to the World Health Organization, the contamination of crops with aflatoxins poses a significant economic burden, estimated to affect 25% of global food crops. In the event that the contaminated food is processed, aflatoxins enter the general food supply and can cause serious diseases. Aflatoxins are distributed unevenly in food or feedstock, making eradicating them both a scientific and a technological challenge. Cooking, freezing, or pressurizing have little effect on aflatoxins. While chemical methods degrade toxins on the surface of contaminated food, the destruction inside entails a slow process. Physical techniques, such as irradiation with ultraviolet photons, pulses of extensive white radiation, and gaseous plasma, are promising; yet, the exact mechanisms concerning how these techniques degrade aflatoxins require further study. Correlations between the efficiency of such degradation and the processing parameters used by various authors are presented in this review. The lack of appropriate guidance while interpreting the observed results is a huge scientific challenge.

Wettability Increase in Plasma-Treated Agricultural Seeds and Its Relation to Germination Improvement

The literature on plasma-stimulated modification of seed wettability and germination is reviewed and analyzed. The results reported by different authors are scattered, but there is a positive correlation between the change in the water contact angle and the germination improvement. There is hardly any correlation between the germination and the power density used for sustaining gaseous plasma. The wettability, on the other hand, exhibits optimal values at the power density of roughly 1 W cm−3, but the results differ significantly. In fact, a super hydrophilic surface finish was only reported at such moderate power densities. Both the wettability and germination increase with treatment time, but saturate at a certain level, depending on the discharge power. Unlike for most polymers, the hydrophobic recovery does not appear to be a considerable obstacle, so the plasma treatment may be performed well before sowing, which makes the technique applicable in agricultural practice. The scattering of results indicates that the commonly reported parameters such as the type and mode of discharge, the discharge power or power density, the type of gas and its pressure, the treatment time and the type of the seeds, are not decisive parameters governing wettability and germination. Based on the observations of the reviewing authors, conclusions and scientific challenges in this scientific niche are summarized.

Hydrophilization of corn seeds by non-equilibrium gaseous plasma

Plasma agriculture is a promising niche of interdisciplinary research where the physics, of non-equilibrium gases meets surface chemistry and biological responses. Despite numerous scientific papers, the interaction of gaseous plasma with seeds is not understood enough to make the technique useful in practical agriculture. An obstacle is an improper methodology adopted by different authors. In this paper, we show that the surface wettability does not depend on discharge parameters such as power and pressure, but rather on the fluence of oxygen atoms onto the seed surface. The proper methodology is demonstrated for the case of corn seeds. The surface activation, which enables improved water uptake or good adhesion of a coating, progresses relatively linearly up to the O-atom fluence of 3 × 1024 m−3 and remains constant thereafter. The minimal water contact angle achievable using oxygen plasma treatment is a few degrees.

Extracellular Vesicle Isolation Yields Increased by Low-Temperature Gaseous Plasma Treatment of Polypropylene Tubes

Novel Extracellular Vesicles (EVs) based diagnostic techniques are promising non-invasive procedures for early stage disease detection which are gaining importance in the medical field. EVs are cell derived particles found in body liquids, especially blood, from which they are isolated for further analysis. However, techniques for their isolation are not fully standardized and require further improvement. Herein modification of polypropylene (PP) tubes by cold Atmospheric Pressure Plasma Jet (APPJ) is suggested to minimize the EVs to surface binding and thus increase EVs isolation yields. The influence of gaseous plasma treatment on surface morphology was studied by Atomic Force Microscopy (AFM), changes in surface wettability by measuring the Water Contact Angle (WCA), while surface chemical changes were analyzed by X-Ray Photoelectron Spectroscopy (XPS). Moreover, PP tubes from different manufacturers were compared. The final isolation yields of EVs were evaluated by flow cytometry. The results of this study suggest that gaseous plasma treatment is an intriguing technique to uniformly alter surface properties of PP tubes and improve EVs isolation yields up to 42%.

Recent Advances in Surface Activation of Polytetrafluoroethylene (PTFE) by Gaseous Plasma Treatments

Fluorinated polymers are renowned for their chemical inertness and thus poor wettability and adhesion of various coatings. Apart from chemical methods employing somewhat toxic primers, gaseous plasma treatment is a popular method for the modification of surface properties. Different authors have used different plasmas, and the resultant surface finish spans between super-hydrophobic and super-hydrophilic character. Some authors also reported the hydrophobic recovery. The review of recent papers is presented and discussed. Correlations between plasma and/or discharge parameters and the surface finish are drawn and the most important conclusions are summarized. The concentration of oxygen in the surface film as probed by X-ray photoelectron spectroscopy is inversely dependent on the concentration of oxygen in gaseous plasma. The predominant mechanism leading to hydrophilic surface finish is bond scission by deep ultraviolet radiation rather than functionalization with reactive oxygen species.

Unsteady Collisionless Gaseous Plasma Flow in the Upper Layers of the Charged Atmosphere and The Investigation of Vlasov-Maxwell Equations System.

In the upper charged layers of the atmosphere, the plasma is very rarefied. The collisions between its molecules are almost non-existent, and the driving forces behind them are the Lorentz forces resulting from the electric and magnetic fields. For this reason, we are interested in studying the behavior of non-collision plasmas because of its essential applications, such as the movement of satellites in the charged atmosphere. In this paper, the flow problem of collisionless gaseous plasma is examined. For that propose, we solve the unsteady Vlasov-Maxwell system of non-linear partial differential equations analytically. Methods of moments and traveling wave parameters are used to acquire an exact solution. Specific macroscopic properties of collisionless gaseous plasma are calculated along with electrical and magnetic fields. Further, thermodynamic estimation, such as entropy and entropy production, is presented. Those calculations allow us to measure the consistency with the laws of non-equilibrium thermodynamics. Relations between internal energy modification participations are predicted using Gibbs' equation for collisionless plasma. The modification effect of internal energies due to electro-magnetic fields is found to be small compared with the internal energy change due to the effect of entropy. That is because these fields are self-induced by plasma particles due to the sudden movement of the rigid plane plate. The results are accomplished according to the typical argon gaseous plasma model. Three-dimensional diagrams showing the measured variables are drawn to investigate and discuss their behavior. The problem has many commercial applications for the movement of objects in the charged atmosphere.

N-Graphene Nanowalls via Plasma Nitrogen Incorporation and Substitution: The Experimental Evidence

Incorporating nitrogen (N) atom in graphene is considered a key technique for tuning its electrical properties. However, this is still a great challenge, and it is unclear how to build N-graphene with desired nitrogen configurations. There is a lack of experimental evidence to explain the influence and mechanism of structural defects for nitrogen incorporation into graphene compared to the derived DFT theories. Herein, this gap is bridged through a systematic study of different nitrogen-containing gaseous plasma post-treatments on graphene nanowalls (CNWs) to produce N-CNWs with incorporated and substituted nitrogen. The structural and morphological analyses describe a remarkable difference in the plasma–surface interaction, nitrogen concentration and nitrogen incorporation mechanism in CNWs by using different nitrogen-containing plasma. Electrical conductivity measurements revealed that the conductivity of the N-graphene is strongly influenced by the position and concentration of C–N bonding configurations. These findings open up a new pathway for the synthesis of N-graphene using plasma post-treatment to control the concentration and configuration of incorporated nitrogen for application-specific properties.