Green engineering of TMC-CMS nanoparticles decorated graphene sheets for targeting M. tuberculosis

Our current work intends to primarily engineer a new type of antibacterial composite by preparing a highly biocompatible graphene sheet decorated with TMC-CMS IPNs nanoparticles utilizing one-pot, green, cost-effective ultrasonication approach. The microstructure of as-formed materials was chemically confirmed using various analytical techniques such as ¹H-NMR, FTIR, UV/vis, SEM, and TEM. TEM data has proved the formation of uniformly distributed TCNPs on graphene surfaces with a small particle size of ~22 nm compared with that of pure nanoparticles (~30 nm). The inhibitory activity of these developed materials was examined against the growth of three different M. tuberculosis pathogens and in a comparison with the isoniazid drug as a standard anti-tuberculosis drug. The TCNPs@GRP composite attained MIC values of 0.98, 3.9, and 7.81 μg/mL for inhibiting the growth of sensitive, MDR, and XDR M. tuberculosis pathogens compared to the bare TCNPs (7.81, 31.25, >125 μg/mL) and the isoniazid drug (0.24, 0, 0 μg/mL), respectively. This reveals a considerable synergism in the antituberculosis activity between TCNPs and graphene nanosheets. Cytotoxicity of the TCNPs@GRP was examined against normal lung cell lines (WI38) and was found to have cell viability of 100% with the concentration range of 0.98-7.81 μg/mL.

Regulated electrochemical performance of manganese oxide cathode for potassium-ion batteries: A combined experimental and first-principles density functional theory (DFT) investigation

Potassium-ion batteries (KIBs) are promising energy storage devices owing to their low cost, environmental-friendly, and excellent K⁺ diffusion properties as a consequence of the small Stoke's radius. The evaluation of cathode materials for KIBs, which are perhaps the most favorable substitutes to lithium-ion batteries, is of exceptional importance. Manganese dioxide (α-MnO₂) is distinguished by its tunnel structures and plenty of electroactive sites, which can host cations without causing fundamental structural breakdown. As a result of the satisfactory redox kinetics and diffusion pathways of K⁺ in the structure, α-MnO₂ nanorods cathode prepared through hydrothermal method, reversibly stores K⁺ at a fast rate with a high capacity and stability. It has a first discharge capacity of 142 mAh/g at C/20, excellent rate execution up to 5C, and a long cycling performance with a demonstration of moderate capacity retention up to 100 cycles. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) simulations confirm that the K⁺ intercalation/deintercalation occurs through 0.46 K movement between Mn^IV/Mn^III redox pairs. First-principles density functional theory (DFT) calculations predict a diffusion barrier of 0.31 eV for K⁺ through the 1D tunnel of α-MnO₂ electrode, which is low enough to promote faster electrochemical kinetics. The nanorod structure of α-MnO₂ facilitates electron conductive connection and provides a strong electrode-electrolyte interface for the cathode, resulting in a very consistent and prevalent execution cathode material for KIBs.

Green antimicrobial adsorbent containing grafted xanthan gum/SiO2 nanocomposites for malachite green dye

Recently, removal of synthetic dyes, especially cationic dye of malachite green (MG), and inhibition of the growth of pathogenic microorganism from drinking water have gained much interest due to their high toxic potency for aquatic biosystems. Herein, a new dye adsorbent with outstanding antibacterial activity was fabricated based on xanthan gum (XG) and SiO₂ nanoparticles through ultrasonication followed by the crosslinking polymerization with vinyl imidazole monomer. The nano adsorbents were characterized with various techniques such as FTIR, XRD, SEM, EDX, and TEM. The nanocomposites were applied as a filter for discarding MG dye and killing the growth of bacterial strains such as E.coli and S.aureus which are considered as the common impurities for drinking water. The data revealed that a maximum adsorption capacity was recorded as 99.5% (Q_max = 588.2 mg/g) at optimum conditions including 10 mg nanocomposite, 10 mL of MG dye (450 ppm), pH = 7, the temperature of 30 °C, and the adsorption time was adjusted within 6 h. The process of dye adsorption was applied to the common isotherm models of Langmuir, Temkin, and Freundlich, and the findings showed that the adsorption behavior was well fitted with the Langmuir one (R² = 0.9983). Moreover, different adsorption kinetic models such as pseudo-first order, pseudo-second order, and intra-particle diffusion were studied for understanding the mechanism of MG adsorption onto nanocomposite surface. It was found that both intraparticle diffusion and pseudo-first-order have participated evenly in the adsorption mechanism of MG dye. Ultimately, the as-prepared nanocomposites were tested against the growth of S. aureus, and E.coli manifesting a superior inhibition diameter as 23.5 ± 0.50, and 25.33 ± 0.47 mm against E.coli, and S. aureus, respectively. Therefore, our new XG-g-PVI/SiO₂ adsorbent is a very promising adsorbent for the fast and efficient capture of dyes from aqueous solutions.

N-methylene phosphonic acid chitosan/graphene sheets decorated with silver nanoparticles as green antimicrobial agents

A green and scalable approach for the preparation of few-layered graphene utilizing the biowaste of potato peels has been developed. The potato peels have been dried and carbonized to obtain a new graphite structure that has been exfoliated in N-methylene phosphonic acid chitosan (MPC). The exfoliation process assisted the formation of graphene sheets with a high size diameter and quality of 50% based on the weight of graphite structure. The graphene sheets were green decorated with silver nanoparticles using microwave power to obtain new nanocomposites. The mass ratio between the graphite and silver nitrate was optimized and observed to change the morphology and size diameter of silver nanoparticles. The as-prepared MPC structure, graphene, and silver decorated graphene nanocomposites were characterized using ¹HNMR, FTIR, XRD, UV/Vis spectrophotometer, SEM, and TEM besides tested as antimicrobial agents. The bacterial performance was also controlled by changing the number of AgNPs distributed on graphene sheets based on the mass ratios of graphite/AgNO₃. The inhibition diameter of silver decorated graphene was considerably increased to 24.8, and 20.1 mm as in the case of MPC-GRP-Ag30 composite compared to the pure graphene (11.2, 13.5 mm) for E. coli and S. aureus, consecutively proposing that the blade edge of graphene sheets can destroy the bacteria membrane and release silver cations promptly that are directed for the interaction with the cytoplasmic parts of the bacteria cell. Such findings offer green and biocompatible antibacterial agents based on the graphene derived from the biowaste products.

High Stability and Long Cycle Life of Rechargeable Sodium-Ion Battery Using Manganese Oxide Cathode: A Combined Density Functional Theory (DFT) and Experimental Study

Sodium-ion batteries (SIBs) can develop cost-effective and safe energy storage technology for substantial energy storage demands. In this work, we have developed manganese oxide (α-MnO2) nanorods for SIB applications. The crystal structure, which is crucial for high-performance energy storage, is examined systematically for the metal oxide cathode. The intercalation of sodium into the α-MnO2 matrix was studied using the theoretical density functional theory (DFT) studies. The DFT studies predict Na ions' facile diffusion kinetics through the MnO2 lattice with an attractively low diffusion barrier (0.21 eV). When employed as a cathode material for SIBs, MnO2 showed a moderate capacity (109 mAh·g-1 at C/20 current rate) and superior life cyclability (58.6% after 800 cycles) in NaPF6/EC+DMC (5% FEC) electrolyte. It shows a much higher capacity of 181 mAh·g-1 (C/20 current rate) in NaClO4/PC (5% FEC) electrolyte, though it suffers fast capacity fading (11.5% after 800 cycles). Our findings show that high crystallinity and hierarchical nanorod morphology of the MnO2 are responsible for better cycling performance in conjunction with fast and sustained charge-discharge behaviors.

Innovative bactericidal adsorbents containing modified xanthan gum/montmorillonite nanocomposites for wastewater treatment

Herein, we reported the preparation of novel antibacterial nanocomposites based on biodegradable polymers. The nanocomposites were applied as capable adsorbent for removing of malachite green (MG) dye, as well as inhibiting of E. coli and S. aureus growth as the most common pollutants for water. The grafted xanthan gum with poly(vinylimidazole) (XG-g-PVI) nanocomposites were synthesized in the presence of different Montmorillonite (MMT) nanoclays concentrations (1%, 3% and 5%). The prepared modified XG nanocomposites were detected through XRD, SEM-EDX, FTIR and TEM. The maximum adsorption MG capacity was determined as 99.99% (909.1 mg/g) in basic medium at 30 °C for 90 min. The adsorption isotherm for removal of MG dye was studied against different models like Langmuir, Freundlich, Temkin, FloryHuggins isotherm models, however, the adsorption results were good fitted with Langmuir isotherm model (R² = 0.9942). Additionally, various adsorption kinetic models: pseudo-first order, second order, pseudo-second order, and intra-particle diffusion models were studied for adsorption mechanism of MG dye on top of prepared nanocomposite surface. Finally, the antibacterial activity outcomes displayed that the prepared XG-g-PVI/MMT nanocomposites had excellent inhibition growth for bacteria and the antibacterial activity increased abruptly with the increased of MMT nanoclay concentrations.