Micro-greens or sprouts are commonly used in the diet of many cultures owing to their health benefits. In this work we use a non-chemical solution method to stimulate the germination and growth of seeds used for sprouting, based on non-thermal plasma discharge (NTP). Such a technology could represent an alternative not only for reducing the production costs for growing micro-greens but also as a pre-sowing method for slow germinating species or those under draught stress. To evaluate the efficiency of the treatments, Brassica oleracea and Lepidium sativum seeds were exposed to a non-thermal plasma discharge produced in atmospheric air in different conditions. The strongest modifications were recorded when the discharge was produced in a closed environment when the reactive species produced in air remained in high concentrations near the seeds. The garden cress exhibited stronger modifications, with a decreasing of the water contact angle of the seeds by up to about 14%, which means an increase of the hydrophilicity of the surface of the seeds. The stimulation of the growth was evaluated as an increase of the average stem length of (9 ± 0.4)% and of the root length of (38 ± 0.5)% as compared to sprouts grown from untreated seeds. This indicated that the reactive species were not only interacting with the surface of the seeds as proved by electron microscopy imaging but also penetrated inside the seeds, activating biological pathways that lead to the stimulation of growth in this case. A noticeable influence produced by the reactive species was also reflected in the biochemical results, where the analysis of the chlorophyll pigments indicated strong modifications, especially under the intensified action of the reactive species. The results prove an important contribution from the reactive species and show the possibility of using this technology to improve the growth of these micro-greens, reducing production time and even presenting the possibility of treating packaged seeds.

Flower-like ZnO architectures assembled with many nanorods were successfully synthesized through Thermionic Vacuum Arc, operated both in direct current (DC-TVA) and a pulsed mode (PTVA), and coupled with annealing in an oxygen atmosphere. The prepared coatings were analysed by scanning-electron microscopy with energy-dispersive X-ray-spectroscopy (SEM-EDX), X-ray-diffraction (XRD), and photoluminescence (PL) measurements. By simply modifying the TVA operation mode, the morphology and uniformity of ZnO nanorods can be tuned. The photocatalytic performance of synthesized nanostructured ZnO coatings was measured by the degradation of methylene-blue (MB) dye and ciprofloxacin (Cipro) antibiotic. The ZnO (PTVA) showed enhancing results regarding the photodegradation of target contaminants. About 96% of MB molecules were removed within 60 min of UV irradiation, with a rate constant of 0.058 min⁻¹, which is almost nine times higher than the value of ZnO (DC-TVA). As well, ZnO (PTVA) presented superior photocatalytic activity towards the decomposition of Cipro, after 240 min of irradiation, yielding 96% degradation efficiency. Moreover, the agar-well diffusion assay performance against both Gram-positive and Gram-negative bacteria confirms the degradation of antibiotic molecules by the UV/ZnO (PTVA) approach, without the formation of secondary hazardous products during the photocatalysis process. Repeated cyclic usage of coatings revealed excellent reusability and operational stability.

Eco-friendly and facile zinc oxide (ZnO) synthesis of zinc-oxide-based nanomaterials with specific properties is a great challenge due to its excellent industrial applications in the field of semiconductors and solar cells. In this paper, we report the production of zinc oxide thin films at relatively low deposition temperature employing a simple and non-toxic method at low substrate temperature: pulsed laser ablation, as a first step for developing a n-ZnO/p-Si heterojunction. Single-phase n-type zinc oxide thin films are confirmed by an X-ray diffraction (XRD) pattern revealed by the maximum diffraction intensity from the (002) plane. Absorbance measurements indicate an increase in the band gap energy close to the bulk ZnO. A 350 °C substrate temperature led to obtaining a highly porous film with high crystallinity and high bandgap, showing good premises for further applications.

Hollow carbon nanospheres with controlled morphologies were synthesized via the copper-carbon direct current arc discharge method by alternating the concentrations of methane in the reactant gas mixture. A self-healing process to keep the structural integrity of encapsulated graphitic shells was evolved gradually by adding methane gas from 0% to 20%. The outer part of the coated layers expanded and hollow nanospheres grew to be large fluffy ones with high methane concentrations from 30% to 50%. A self-repairing function by the reattachment of broken graphitic layers initiated from near-electrode space to distance was also distinctly exhibited. By comparing several comparable metals (e.g. copper, silver, gold, zinc, iron and nickel)-carbon arc discharge products, a catalytic carbon-encapsulation mechanism combined with a core-escaping process has been proposed. Specifically, on the basis of the experimental results, copper could be applied as a unique model for both the catalysis of graphitic encapsulation and as an adequate template for the formation of hollow nanostructures.

Scaling up atmospheric pressure dielectric barrier discharges is a challenging prerequisite to expanding their industrial applications. In this study, we present the results of large-volume dielectric barrier discharges (DBDs) with a parallel plate electrode configuration having an electrode surface of 50 × 200 mm ² and an interelectrode gap of 5 mm. Highly dense filamentary DBD plasma was stably generated over a large area using pre-ionization electrodes embedded in the one of electrodes. We show that the role of the pre-triggering system is crucial in producing a densely distributed filamentary discharge over the electrode surface, especially at the main discharge voltage values of 14.0–18.0 kVp-p and pre-ionization voltage of 7.0–10.0 kVp-p at the same frequency, ranging from 1 to 4 kHz. By tuning the phase difference between the pre-ionization and main discharge voltages to around 180 degrees, both discharge current amplitude and duration time per period of main DBDs are maximized. The present results indicate that such a large-volume DBD is extremely versatile and suited for a wide range of industrial applications.

Non-thermal or cold plasma is an innovative agricultural technology used for the treatment of seeds, producing physicochemical and biochemical changes without thermal damage and stimulating germination and plant growth. The interaction of reactive species generated in cold plasma modifies the morphology of the seed surface, increasing porosity, producing microcracks, removing material or producing other physical changes, and chemically modifying it. The changes induced positively influence the rate, speed, and uniformity of germination, as it is believed that these changes take place as a result of activated metabolic pathways, regulated hormone balance, and stimulated production of enzymes involved in the mobilisation of nutrient reserves needed for seedling growth. Plasma sources, electrical parameters, feed gas, and processing time are some of the essential factors involved in tuning the effects on seeds. Optimising the outcomes and their adaptation for specific species is crucial to maximise the benefits and avoid inhibitory effects. In the frame of ecological and sustainable agriculture, with the benefits given by cold plasma, this review follows the modifications produced by different sources on the seeds, starting from morphological changes to biochemical ones, up to germination, aiming to facilitate the understanding of the interaction and outcomes. We also address the challenges, including variability of biological responses, the need for standard procedures and parameters, and development of scalable technologies. A thorough examination of the changes induced in seeds as a result of non-thermal plasma treatment not only facilitates the improvement of experimental designs and reproducibility but also plays an important role in advancing seed treatment technologies and, ultimately, enhancing crop yields in a sustainable manner.