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Abstract: We have studied CO interaction with SiO2/Si system at high temperature (~1100°C) and 350mbar by core-level photoemission. Even for short annealing time (5 min) the signal from Si2p and C1s core levels shows a clear change upon CO treatment. Shifted components are attributed to formation of SiC. This is confirmed by TEM imaging which further shows that the silicon carbide is in the form of nano-crystals of the 3C polytype. Photoemission spectroscopy moreover reveals the formation of silicon oxicarbide which could not be evidenced by other methods. Combining these results with previous Nuclear Resonance Profiling study gives a deeper insight into the mechanisms involved in the nanocrystals growth and especially for the reaction equation leading to SiC formation. We show that CO diffuses as a molecule through the silica layer and reacts with the silicon substrate according the following reaction: 4 CO+4 Si→SiO2 +2SiC+SiO2C2. [Copyright &y& Elsevier]

2D materials, given their form-factor, high surface-to-volume ratio, and chemical functionality have immense use in sensor design. Engineering 2D heterostructures can result in robust combinations of desirable properties but sensor design methodologies require careful considerations about material properties and orientation to maximize sensor response. This study introduces a sensor approach that combines the excellent electrical transport and transduction properties of graphite film with chemical reactivity derived from the edge sites of semiconducting molybdenum disulfide (MoS 2 ) through a two-step chemical vapour deposition method. The resulting vertical heterostructure shows potential for high-performance hybrid chemiresistors for gas sensing. This architecture offers active sensing edge sites across the MoS 2 flakes. We detail the growth of vertically oriented MoS 2 over a nanoscale graphite film (NGF) cross-section, enhancing the adsorption of analytes such as NO 2 , NH 3 , and water vapor. Raman spectroscopy, density functional theory calculations and scanning probe methods elucidate the influence of chemical doping by distinguishing the role of MoS 2 edge sites relative to the basal plane. High-resolution imaging techniques confirm the controlled growth of highly crystalline hybrid structures. The MoS 2 /NGF hybrid structure exhibits exceptional chemiresistive responses at both room and elevated temperatures compared to bare graphitic layers. Quantitative analysis reveals that the sensitivity of this hybrid sensor surpasses other 2D material hybrids, particularly in parts per billion concentrations.

Preserving host health and homeostasis is largely dependent on the human gut microbiome, a varied and ever-changing population of bacteria living in the gastrointestinal tract. This article aims to explore the multifaceted functions of the gut microbiome and shed light on the evolving field of research investigating the impact of herbal medicines on both the composition and functionality of the gut microbiome. Through a comprehensive overview, we aim to provide insights into the intricate relationship between herbal remedies and the gut microbiome, fostering a better understanding of their potential implications for human health.The gut microbiota is composed of trillions of microorganisms, predominantly bacteria, but also viruses, fungi, and archaea. It functions as a complex ecosystem that interacts with the host in various ways. It aids in nutrient metabolism, modulates the immune system, provides protection against pathogens, and influences host physiology. Moreover, it has been linked to a range of health outcomes, including digestion, metabolic health, and even mental well-being. Recent research has shed light on the potential of herbal medicines to modulate the gut microbiome. Herbal medicines, derived from plants and often used in traditional medicine systems, contain a diverse array of phytochemicals, which can directly or indirectly impact gut microbial composition. These phytochemicals can either act as prebiotics, promoting the growth of beneficial bacteria, or possess antimicrobial properties, targeting harmful pathogens. Several studies have demonstrated the effects of specific herbal medicines on the gut microbiome. For example, extracts from herbs have been shown to enhance the abundance of beneficial bacteria, such as Bifidobacterium and Lactobacillus, while reducing potentially harmful microbes. Moreover, herbal medicines have exhibited promising antimicrobial effects against certain pathogenic bacteria. The modulation of the gut microbiome by herbal medicines has potential therapeutic implications. Research suggests herbal interventions could be harnessed to alleviate gastrointestinal disorders, support immune function, and even impact metabolic health. However, it is important to note that individual responses to herbal treatments can vary due to genetics, diet, and baseline microbiome composition. In conclusion, the gut microbiome is a critical player in maintaining human health, and its modulation by herbal medicines is a burgeoning area of research. Understanding the complex interactions between herbal compounds and gut microbiota will pave the way for innovative approaches to personalized healthcare and the development of herbal-based therapeutics aimed at promoting gut health and overall well-being., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Graphene nanowalls (GNW s ) can be described as extended nanosheets of graphitic carbon where the basal planes are perpendicular to a substrate. Generally, existing techniques to grow films of GNW s are based on plasma-enhanced chemical vapor deposition (PECVD) and the use of diverse substrate materials (Cu, Ni, C, etc) shaped as foils or filaments. Usually, patterned films rely on substrates priorly modified by costly cleanroom procedures. Hence, we report here the characterization, transfer and application of wafer-scale patterned GNW s films that were grown on Cu meshes using low-power direct-current PECVD. Reaching wall heights of ∼300 nm, mats of vertically-aligned carbon nanosheets covered square centimeter wire meshes substrates, replicating well the thread dimensions and the tens of micrometer-wide openings of the meshes. Contrastingly, the same growth conditions applied to Cu foils resulted in limited carbon deposition, mostly confined to the substrate edges. Based on the wet transfer procedure turbostratic and graphitic carbon domains co-exist in the GNW s microstructure. Interestingly, these nanoscaled patterned films were quite hydrophobic, being able to reverse the wetting behavior of SiO 2 surfaces. Finally, we show that the GNW s can also be used as the active material for C-on-Cu anodes of Li-ion battery systems., (Creative Commons Attribution license.)

Graphite sheets are known to exhibit remarkable performance in applications such as heating panels and critical elements of thermal management systems. Industrial-scale production of graphite films relies on high-temperature treatment of polymers or calendering of graphite flakes; however, these methods are limited to obtaining micrometer-scale thicknesses. Herein, we report the fabrication of a flexible and power-efficient cm 2 -scaled heater based on a polycrystalline nanoscale-thick graphite film (NGF, ∼100 nm thick) grown by chemical vapor deposition. The stability of these NGF heaters (operational in air over the range 30-300 °C) is demonstrated by a 12-day continuous heating test, at 215 °C. The NGF exhibits a fast switching response and attains a steady peak temperature of 300 °C at a driving bias of 7.8 V (power density of 1.1 W/cm 2 ). This excellent heating performance is attributed to the structural characteristics of the NGF, which contains well-distributed wrinkles and micrometer-wide few-layer graphene domains (characterized using conductive imaging and finite element methods, respectively). The efficiency and flexibility of the NGF device are exemplified by externally heating a 2000 μm-thick Pyrex glass vial and bringing 5 mL of water to a temperature of 96 °C (at 2.4 W/cm 2 ). Overall, the NGF could become an excellent active material for ultrathin, flexible, and sustainable heating panels that operate at low power.

For THz rectennas, ultra-fast diodes are required. While the metal-insulator-metal (MIM) diode has been investigated in recent years, it suffers from large resistance and capacitance, as well as a low cut-off frequency. Alternatively, a geometric diode can be used, which is more suitable due to its planar structure. However, there is only one report of a THz geometric diode based on a monolayer graphene. It is based on exfoliated graphene, and thus, it is not suitable for mass production. In this work, we demonstrate chemical vapor deposition (CVD)-grown monolayer graphene based geometric diodes, which are mass-producible. The diode's performance has been studied experimentally by varying the neck widths from 250-50 nm, the latter being the smallest reported neck width for a graphene geometric diode. It was observed that by decreasing the neck widths, the diode parameters such as asymmetry, nonlinearity, zero-bias resistance, and responsivity increased within the range studied. For the 50 nm neck width diode, the asymmetry ratio was 1.40 for an applied voltage ranging from -2 V to 2 V, and the zero-bias responsivity was 0.0628 A/W. The performance of the diode was also verified through particle-in-cell Monte Carlo simulations, which showed that the simulated current-voltage characteristics were consistent with our experimental results.

In the surge of recent successes of 2D materials following the rise of graphene, molybdenum disulfide (2D-MoS 2 ) has been attracting growing attention from both fundamental and applications viewpoints, owing to the combination of its unique nanoscale properties. For instance, the bandgap of 2D-MoS 2 , which changes from direct (in the bulk form) to indirect for ultrathin films (few layers), offers new prospects for various applications in optoelectronics. In this review, we present the latest scientific advances in the field of synthesis and characterization of 2D-MoS 2 films while highlighting some of their applications in energy harvesting, gas sensing, and plasmonic devices. A survey of the physical and chemical processing routes of 2D-MoS 2 is presented first, followed by a detailed description and listing of the most relevant characterization techniques used to study the MoS 2 nanomaterial as well as theoretical simulations of its interesting optical properties. Finally, the challenges related to the synthesis of high quality and fairly controllable MoS 2 thin films are discussed along with their integration into novel functional devices.

In the last decade, catalytic chemical vapor deposition (CVD) has been intensively explored for the growth of single-layer graphene (SLG). Despite the scattering of guidelines and procedures, variables such as the surface texture/chemistry of catalyst metal foils, carbon feedstock, and growth process parameters have been well-scrutinized. Still, questions remain on how best to standardize the growth procedure. The possible correlation of procedures between different CVD setups is an example. Here, two thermal CVD reactors were explored to grow graphene on Cu foil. The design of these setups was entirely distinct, one being a "showerhead" cold-wall type, whereas the other represented the popular "tubular" hot-wall type. Upon standardizing the Cu foil surface, it was possible to develop a procedure for cm 2 -scale SLG growth that differed only by the carrier gas flow rate used in the two reactors., (© 2021 Wiley-VCH GmbH.)

The growth of graphite on polycrystalline Ni by chemical vapor deposition (CVD) and the microstructural relation of the graphitic films and the metallic substrate continues to puzzle the scientific community. Here, we report the wafer-scale growth of a nanometer-thick graphite film (∼100 nm, NGF) on Ni foil via a fast-thermal CVD approach (5 min growth). Moreover, we shed light on how localized thickness variations of the NGF relate to the Ni surface topography and grain characteristics. While on a macro-scale (mm 2 ), the NGF film looks uniform-with a few hundred highly ordered graphene layers (d 0002 = 0.335 nm), when studied at the micro- and nano-scales, few-layer graphene sections can be identified. These are present at a density of 0.1%-3% areas in 100 µ m 2 , can be as thin as two layers, and follow an epitaxial relation with the {111} fcc-Ni planes. Throughout the 50 cm 2 NGF, the sharp graphite/substrate interfaces are either composed of a couple of NiC x layers or a graphene layer. Moreover, the NGF was successfully transferred on SiO 2 /Si substrate by a wet chemical etching method. The as-produced NGFs could complement or offer an alternative to the mm-thick films produced from natural graphite flakes or polymer sheets.

Nanorange thickness graphite films (NGFs) are robust nanomaterials that can be produced via catalytic chemical vapour deposition but questions remain regarding their facile transfer and how surface topography may affect their application in next-generation devices. Here, we report the growth of NGFs (with an area of 55 cm 2 and thickness of ~ 100 nm) on both sides of a polycrystalline Ni foil and their polymer-free transfer (front- and back-side, in areas up to 6 cm 2 ). Due to the catalyst foil topography, the two carbon films differed in physical properties and other characteristics such as surface roughness. We demonstrate that the coarser back-side NGF is well-suited for NO 2 sensing, whereas the smoother and more electrically conductive front-side NGF (2000 S/cm, sheet resistance - 50 Ω/sq) could be a viable conducting channel or counter electrode in solar cells (as it transmits 62% of visible light). Overall, the growth and transfer processes described could help realizing NGFs as an alternative carbon material for those technological applications where graphene and micrometer-thick graphite films are not an option.

Densely populated edge-terminated vertically aligned two-dimensional MoS 2 nanosheets (NSs) with thicknesses ranging from 5 to 20 nm were directly synthesized on Mo films deposited on SiO 2 by sulfurization. The quality of the obtained NSs was analyzed by scanning electron and transmission electron microscopy, and Raman and X-ray photoelectron spectroscopy. The as-grown NSs were then successfully transferred to the substrates using a wet chemical etching method. The transferred NSs sample showed excellent field-emission properties. A low turn-on field of 3.1 V/μm at a current density of 10 µA/cm 2 was measured. The low turn-on field is attributed to the morphology of the NSs exhibiting vertically aligned sheets of MoS 2 with sharp and exposed edges. Our findings show that the fabricated MoS 2 NSs could have a great potential as robust high-performance electron-emitter material for various applications such as microelectronics and nanoelectronics, flat-panel displays and electron-microscopy emitter tips.

We report 3C-SiC nano-crystals synthesis by thermal annealing of SiO2/Si wafers in CO2 gas. The nano-crystals have been characterized using scanning electron microscopy and atomic force microscopy. These results are correlated with selective area electron diffraction paterns, and transmission electron microscopy observations that evidence the formation of cubic SiC nano-crystals epitaxied on Si. In our experimental conditions, the crystals size is in the range 10-60 nm, increasing with the treatment time, as the crystals density. Using isotopic labelled SiO2 associated with Nuclear Reaction Analysis (NRA) and Nuclear Narrow Resonance Profiling (NRP), oxygen exchanges between CO2 and SiO2 could be evidenced.