Preparation of nanolignin rich fraction from bamboo stem via green technology: assessment of its antioxidant, antibacterial and UV blocking properties.

This work reports the preparation of nano lignin-rich fraction material via green technology from the holistic use of lignocellulosic biomass bamboo. The bamboo is first chemically treated, followed by acid precipitation to extract bamboo-derived macro lignin-rich fraction material. The nano lignin-rich fraction material was then prepared via ultrasonication technique from the extracted bamboo-derived macro lignin-rich fraction material. The confirmation of the distinct lignin functional groups in the extracted lignin-rich fractions has been done by FTIR. Surface morphology by FESEM and TEM revealed spherical nano-lignin-rich fraction materials from extracted bamboo-derived macro lignin-rich fraction materials. DPPH assays indicated that both the obtained fractions depict beneficial antioxidant characteristics. They were found to be effective in terms of their antibacterial activity against both gram-positive bacteria Staphylococcus aureus (S.aureus) and gram-negative bacteria Escherichia coli (E.coli), using the disc diffusion method. These fractions have UV blocking property, and nano-lignin-rich fraction material acts as a more potential UV blocking agent than others. Thus, the nano-lignin-rich fraction material has great potential as a high antioxidant, antibacterial, and UV blocking agent useful in biomedical applications.Highlights Extraction of macro-lignin rich fraction material using chemical treatment of lignocellulosic biomass bamboo via refluxing followed by acid precipitation.Preparation of nano-lignin rich fraction material from extracted bamboo-derived macro-lignin rich fraction material via ultrasonication technique as a green technology.Structural and surface morphology of the extracted macro-lignin & nano lignin-rich fraction materials have been analyzed by XRD, FTIR, EDX, SEM and TEM.The macro lignin & nano lignin-rich fraction materials showed good antioxidant, antibacterial activity and UV-blocking properties, but the nano-lignin rich fraction material exhibited more efficient properties.

Advances in Nanoarchitectonics of Antimicrobial Tiles and a Quest for Anti-SARS-CoV-2 Tiles.

Design of antimicrobial tiles seems necessary to combat against contagious diseases, especially COVID-19. In addition to personal hygiene, this technology facilitates public hygiene as antimicrobial tiles can be installed at hospitals, schools, banks, offices, lobbies, railway stations, etc. This review is primarily focused on preparing antimicrobial tiles using an antimicrobial layer or coatings that fight against germs. The salient features and working mechanisms of antimicrobial tiles are highlighted. This challenge is a component of the exploratory nature of nanoarchitectonics, that also extends farther than the realm of nanotechnology. This nanoarchitectonics has been successful at the laboratory scale as antimicrobial metal nanoparticles are mainly used as additives in preparing tiles. A detailed description of various materials for developing unique antimicrobial tiles is reported here. Pure metal (Ag, Zn) nanoparticles and a mixture of nanoparticles with other inorganic materials (SiO2,, TiO2, anatase, nepheline) have been predominantly used to combat microbes. The developed antimicrobial tiles have shown excellent activity against a wide range of Gram-positive and Gram-negative bacteria. The last section discussed a hypothetical overview of utilizing the antimicrobial tiles against SARS-CoV-2. Overall, this review gives descriptive knowledge about the importance of antimicrobial tiles to create a clean and sustainable environment.

Unusual High Hardness and Load-Dependent Mechanical Characteristics of Hydrogenated Carbon-Nitrogen Hybrid Films.

Mechanical components are exposed to a rigorous environment in a number of applications including engineering, aerospace, and automobiles. Thus, their service lifetime and reliability are always on the verge of risk. Protective coatings with high hardness are required to enhance their service lifetime and minimize the replacement cost and waste burden. Hydrogenated amorphous carbon including nitrogen-incorporated films, that are commonly deposited by plasma-enhanced chemical vapor deposition, are widely used for commercial protective coating applications. However, their mechanical hardness still falls into the moderate hard regime. This needs to be substantially enhanced for advanced applications. Here, we report the synthesis of very hard nanostructured hydrogenated carbon-nitrogen hybrid (n-C:H:N) films. The optimized n-C:H:N film displays a hardness of about 36 GPa, elastic modulus of 360 GPa, and reasonably good elastic recovery (ER) of 62.7%. The mechanical properties of n-C:H:N films are further tailored when nitrogen pressure is tuned during the growth. The realized remarkably improved mechanical properties are correlated with the films' structural properties and experimental growth conditions. We also conducted density functional theory calculations that show the trend for the elastic modulus of the amorphous carbon films with varying nitrogen concentrations matches well with experimentally measured values. Finally, we probed load-dependent mechanical properties of n-C:H:N films and found an anomalous behavior; some of the mechanical parameters, for instance, ER, reveal an irregular trend with indentation load, which we explain in the framework of the film-substrate composite concept. Overall, this work uncovers many unknown and exciting mechanical phenomena that could pave the way for new technological developments.

Angstrom-Scale Transparent Overcoats: Interfacial Nitrogen-Driven Atomic Intermingling Promotes Lubricity and Surface Protection of Ultrathin Carbon.

Lubricity, a phenomenon which enables the ease of motion of objects, and wear resistance, which minimizes material damage or degradation, are important fundamental characteristics for sustainable technology developments. Ultrathin coatings that promote lubricity and wear resistance are of huge importance for a number of applications, including magnetic storage and micro-/nanoelectromechanical systems. Conventional ultrathin coatings have, however, reached their limit. Graphene-based materials that have shown promise to reduce friction and wear have many intrinsic limitations such as high temperature and substrate-specific growth. To address these concerns, a great deal of research is currently ongoing to optimize graphene-based materials. Here we discover that angstrom-thick carbon (8 Å) significantly reduces interfacial friction and wear. This lubricant shows ultrahigh optical transparency and can be directly deposited on a wide range of surfaces at room temperature. Experiments combined with molecular dynamics simulations reveal that the lubricating efficacy of 8 Å carbon is further improved via interfacial nitrogen.

Slippery and Wear-Resistant Surfaces Enabled by Interface Engineered Graphene.

Friction and wear remain the primary cause of mechanical energy dissipation and system failure. Recent studies reveal graphene as a powerful solid lubricant to combat friction and wear. Most of these studies have focused on nanoscale tribology and have been limited to a few specific surfaces. Here, we uncover many unknown aspects of graphene's contact-sliding at micro- and macroscopic tribo-scales over a broader range of surfaces. We discover that graphene's performance reduces for surfaces with increasing roughness. To overcome this, we introduce a new type of graphene/silicon nitride (SiNx, 3 nm) bilayer overcoats that exhibit superior performance compared to native graphene sheets (mono and bilayer), that is, display the lowest microscale friction and wear on a range of tribologically poor flat surfaces. More importantly, two-layer graphene/SiNx bilayer lubricant (<4 nm in total thickness) shows the highest macroscale wear durability on tape-head (topologically variant surface) that exceeds most previous thicker (∼7-100 nm) overcoats. Detailed nanoscale characterization and atomistic simulations explain the origin of the reduced friction and wear arising from these nanoscale coatings. Overall, this study demonstrates that engineered graphene-based coatings can outperform conventional coatings in a number of technologies.