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Herein, we developed a near-invisible solar cell through a precise control of the contact barrier between an indium tin oxide (ITO) electrode and a monolayer tungsten disulfide (WS 2 ), grown by chemical vapor deposition (CVD). The contact barrier between WS 2 and ITO was controlled by coating various thin metals on top of ITO (M x /ITO) and inserting a thin layer of WO 3 between M x /ITO and the monolayer WS 2 , which resulted in a drastic increase in the Schottky barrier height (up to 220 meV); this could increase the efficiency of the charge carrier separation in our Schottky-type solar cell. The power conversion efficiency (PCE) of the solar cell with the optimized electrode (WO 3 /M x /ITO) was more than 1000 times that of a device using a normal ITO electrode. Large-scale fabrication of the solar cell was also investigated, which revealed that a simple size expansion with large WS 2 crystals and parallel long electrodes could not improve the total power (P T ) obtained from the complete device even with an increase in the device area; this can be explained by the percolation theory. This problem was addressed by reducing the aspect ratio (width/channel length) of the unit device structure to a value lower than a critical threshold. By repeating the experiments on this optimized unit device with an appropriate number of series and parallel connections, P T could be increased up to 420 pW from a 1-cm 2 solar cell with a very high value (79%) of average visible transmission (AVT).

Atmospheric pressure plasma (APP) has emerged as a versatile tool for the functionalization, modification, and synthesis of carbon-based materials. This review summarizes the historical development, underlying principles, and current progress of APP in material science, with a particular focus on carbon nanomaterials. The fundamentals of plasma parameters are introduced to highlight their roles in driving plasma–surface interactions and establish the diagnostics for these parameters. Recent advances in gas-phase and plasma–liquid systems and the influence of different plasma chemistries have led to different material functionalization results, which are discussed. Applications of plasma-treated carbon in energy storage, environment, and biomedicine are critically reviewed, demonstrating significant improvements in electrochemical performance, adsorption efficiency, and biocompatibility. Finally, current challenges are outlined alongside future perspectives on integrating APP. This review aims to provide a comprehensive reference for researchers seeking to exploit APP as a green and scalable platform for next-generation carbon materials.

The very early nucleation stage of a transition metal dichalcogenide (TMD) was directly observed with in-situ monitoring of chemical vapor deposition and automated image analysis. Unique nucleation dynamics, such as very large critical nuclei and slow to rapid growth transitions, were observed during the vapor–liquid–solid (VLS) growth of monolayer tungsten disulfide (WS 2 ). This can be explained by two-step nucleation, also known as non-classical nucleation, in which metastable clusters are formed through the aggregation of droplets. Subsequently, nucleation of solid WS 2 takes place inside the metastable cluster. Furthermore, the detailed nucleation dynamics was systematically investigated from a thermodynamic point of view, revealing that the incubation time of metastable cluster formation follows the traditional time–temperature transformation diagram. Quantitative phase field simulation, combined with Bayesian inference, was conducted to extract quantitative information on the growth dynamics and crystal anisotropy from in-situ images. A clear transition in growth dynamics and crystal anisotropy between the slow and rapid growth phases was quantitatively verified. This observation supports the existence of two-step nucleation in the VLS growth of WS 2 . Such detailed understanding of TMD nucleation dynamics can be useful for achieving perfect structure control of TMDs.

Few-layered transition metal dichalcogenides (TMDs) are known as true two-dimensional materials, with excellent semiconducting properties and strong light–matter interaction. Thus, TMDs are attractive materials for semitransparent and flexible solar cells for use in various applications. Hoewver, despite the recent progress, the development of a scalable method to fabricate semitransparent and flexible solar cells with mono- or few-layered TMDs remains a crucial challenge. Here, we show easy and scalable fabrication of a few-layered TMD solar cell using a Schottky-type configuration to obtain a power conversion efficiency (PCE) of approximately 0.7%, which is the highest value reported with few-layered TMDs. Clear power generation was also observed for a device fabricated on a large SiO 2 and flexible substrate, demonstrating that our method has high potential for scalable production. In addition, systematic investigation revealed that the PCE and external quantum efficiency (EQE) strongly depended on the type of photogenerated excitons (A, B, and C) because of different carrier dynamics. Because high solar cell performance along with excellent scalability can be achieved through the proposed process, our fabrication method will contribute to accelerating the industrial use of TMDs as semitransparent and flexible solar cells.

Plasma technology, which can instantaneously transform air molecules into reactive species stimulating plants, potentially contributes to developing a sustainable agricultural system with high productivity and low environmental impact. In fact, plant immunity activation by exposure to a reactive gas mainly consisting of dinitrogen pentoxide (N 2 O 5 ) was recently discovered, while physiological responses to N 2 O 5 are rarely known. Here, we demonstrate early (within 10 min) physiological responses to N 2 O 5 gas in Arabidopsis. Exposure to N 2 O 5 gas induced an increase in cytosolic Ca 2+ concentration within seconds in directly exposed leaves, followed by systemic long-distance Ca 2+ -based signaling within tens of seconds. In addition, jasmonic acid (JA)-related gene expression was induced within 10 minutes, and a significant upregulation of the defense-related gene PDF1 . 2 was observed after 1 day of exposure to N 2 O 5 gas. These systemic resistant responses to N 2 O 5 were found unique among air-plasma-generated species such as ozone (O 3 ) and nitric oxide (NO)/nitrogen dioxide (NO 2 ). Our results provide new insights into understanding of plant physiological responses to air-derived reactive species, in addition to facilitating the development of plasma applications in agriculture.

Reactive nitrogen species (RNS) play an important role in plant immunity as signaling factors. We previously developed a plasma technology to partially convert air molecules into dinitrogen pentoxide (N 2 O 5 ), an RNS whose physiological action is poorly understood. To reveal the function of N 2 O 5 gas in plant immunity, Arabidopsis thaliana was exposed to plasma-generated N 2 O 5 gas once (20 s) per day for 3 days, and inoculated with Botrytis cinerea , Pseudomonas syringae pv. tomato DC3000 ( Pst ), or cucumber mosaic virus strain yellow (CMV(Y)) at 24 h after the final N 2 O 5 gas exposure. Lesion size with B . cinerea infection was significantly ( P < 0.05) reduced by exposure to N 2 O 5 gas. Propagation of CMV(Y) was suppressed in plants exposed to N 2 O 5 gas compared with plants exposed to the air control. However, proliferation of Pst in the N 2 O 5 -gas-exposed plants was almost the same as in the air control plants. These results suggested that N 2 O 5 gas exposure could control plant disease depending on the type of pathogen. Furthermore, changes in gene expression at 24 h after the final N 2 O 5 gas exposure were analyzed by RNA-Seq. Based on the gene ontology analysis, jasmonic acid and ethylene signaling pathways were activated by exposure of Arabidopsis plants to N 2 O 5 gas. A time course experiment with qRT-PCR revealed that the mRNA expression of the transcription factor genes, WRKY25 , WRKY26 , WRKY33 , and genes for tryptophan metabolic enzymes, CYP71A12 , CYP71A13 , PEN2 , and PAD3 , was transiently induced by exposure to N 2 O 5 gas once for 20 s peaking at 1–3 h post-exposure. However, the expression of PDF1 . 2 was enhanced beginning from 6 h after exposure and its high expression was maintained until 24–48 h later. Thus, enhanced tryptophan metabolism leading to the synthesis of antimicrobial substances such as camalexin and antimicrobial peptides might have contributed to the N 2 O 5 -gas-induced disease resistance.

Fixing atmospheric nitrogen for use as fertilizer is a crucial process in promoting plant growth and enhancing crop yields in agricultural production. Currently, the chemical production of nitrogen fertilizer from atmospheric N2 relies on the energy-intensive Haber–Bosch process. Therefore, developing a low-cost and easily applicable method for fixing nitrogen from the air would provide a beneficial alternative. In this study, we tested the utilization of dinitrogen pentoxide (N2O5) gas, generated from oxygen and nitrogen present in ambient air with the help of a portable plasma device, as a nitrogen source for the model plant Arabidopsis thaliana. Nitrogen-deficient plants supplied with medium treated with N2O5, were able to overcome nitrogen deficiency, similar to those provided with medium containing a conventional nitrogen source. However, prolonged direct exposure of plants to N2O5 gas adversely affected their growth. Short-time exposure of plants to N2O5 gas mitigated its toxicity and was able to support growth. Moreover, when the exposure of N2O5 and the contact with plants were physically separated, plants cultured under nitrogen deficiency were able to grow. This study shows that N2O5 gas generated from atmospheric nitrogen can be used as an effective nutrient for plants, indicating its potential to serve as an alternative nitrogen fertilization method for promoting plant growth.Key messageWe identified plasma-generated N2O5 gas as a promising nitrogen fertilizer with the capacity to promote agricultural production by utilizing atmospheric nitrogen.

Transition metal dichalcogenides (TMDs) attract intence attention due to its unique optoelectrical features. Recent progress in production stage of TMD enables us to synthesis uniform and large area TMD with mono layer thickness. Elucidation of growth mechanism is a challenge to improve the crystallinity of TMD, which is regargeded as a next crutial subject in the production stage. Here we report novel diffusion and nucleation dynamics during tungsten disulphide (WS 2 ) growth. The diffusion length ( L d ) of the precursors have been measured with unique nucleation control methods. It was revealed that the L d reaches up to ~750 μm. This ultra-long diffusion can be attributed to precursor droplets observed during in-situ monitoring of WS 2 growth. The integrated synthesis of >35,000 single crystals and monolayer WS 2 was achieved at the wafer scale based on this model. Our findings are highly significant for both the fundamental study of droplet-mediated crystal growth and the industrial application of integrated single-crystal TMDs.

This study was designed to assess the effects of cold atmospheric plasma on osteoblastic differentiation in pre-osteoblastic MC3T3-E1 cells. Plasma was irradiated directly to a culture medium containing plated cells for 5 s or 10 s. Alkaline phosphatase (ALP) activity assay and alizarin red staining were applied to assess osteoblastic differentiation. The plasma-generated radicals were detected directly using an electron spin resonance-spin trapping technique. Results show that plasma irradiation under specific conditions increased ALP activity and enhanced mineralization, and demonstrated that the yield of radicals was increased in an irradiation-time-dependent manner. Appropriate plasma irradiation stimulated the osteoblastic differentiation of the cells. This process offers the potential of promoting bone regeneration.

Non-equilibrium helium atmospheric-pressure plasma (He-APP), which allows for a strong non-equilibrium chemical reaction of O 2 and N 2 in ambient air, uniquely produces multiple extremely reactive products, such as reactive oxygen species (ROS), in plasma-irradiated solution. We herein show that relatively short-lived unclassified reactive species (i.e., deactivated within approximately 10 min) generated by the He-APP irradiation can trigger physiologically relevant Ca 2+ influx through ruthenium red- and SKF 96365-sensitive Ca 2+ -permeable channel(s), possibly transient receptor potential channel family member(s). Our results provide novel insight into understanding of the interactions between cells and plasmas and the mechanism by which cells detect plasma-induced chemically reactive species, in addition to facilitating development of plasma applications in medicine.