Metallic 1T-N-WS2 /WO3 Heterojunctions Featuring Interface-Engineered Cu-S Configuration for Selective Electrochemical CO2 Reduction Reaction.

Electrocatalytic carbon-dioxide reduction reactions (ECO2 RR) are one of the most rational techniques to control one's carbon footprint. The desired product formation depends on deliberate reaction kinetics and a choice of electron-proton contribution. Herein the usage of novel CuS active centers decorated over stable 1T metallic N-WS2 /WO3 nanohybrids as an efficient selective formate conversion electrocatalyst with regard to ECO2 RR is reported. The preferred reaction pathway is identified as *OCHO, which is reduced (by gaining H+  + e- ) to HCOO- (HCOO- path) as the primary product. More significantly, at -1.3 V versus RHE yield of FEHCOO - is 55.6% ± 0.5 with a Jgeo of -125.05 mA cm-2 for CuS@1T-N-WS2 /WO3 nanohybrids. In addition, predominant catalytic activity, selectivity, and stability properties are observed; further post-mortem analysis demonstrates the choice of material importance. The present work describes an impressive approach to develop highly active electrocatalysts for selective ECO2 RR applications.

Low-Cost Self-Reconstructed High Entropy Oxide as an Ultra-Durable OER Electrocatalyst for Anion Exchange Membrane Water Electrolyzer.

Future energy loss can be minimized to a greater extent via developing highly active electrocatalysts for alkaline water electrolyzers. Incorporating an innovative design like high entropy oxides, dealloying, structural reconstruction, in situ activation can potentially reduce the energy barriers between practical and theoretical potentials. Here, a Fd-3m spinel group high entropy oxide is developed via a simple solvothermal and calcination approach. The developed (FeCoMnZnMg)3O4 electrocatalyst shows a near equimolar distribution of all the metal elements resulting in higher entropy (ΔS ≈1.61R) and higher surface area. The self-reconstructed spinel high entropy oxide (S-HEO) catalyst exhibited a lower overpotential of 240 mV to reach 10 mA cm-2 and enhanced reaction kinetics (59 mV dec-1). Noticeably, the S-HEO displayed an outstanding durability of 1000 h without any potential loss, significantly outperforming most of the reported OER electrocatalysts. Further, S-HEO is evaluated as the anode catalyst for an anion exchange membrane water electrolyzer (AEMWE) in 1 m, 0.1 m KOH, and DI water at 20 and 60 °C. These results demonstrate that S-HEO is a highly attractive, non-noble class of materials for high active oxygen evolution reaction (OER) electrocatalysts allowing fine-tuning beyond the limits of bi- or trimetallic oxides.

Surface Area-Enhanced Cerium and Sulfur-Modified Hierarchical Bismuth Oxide Nanosheets for Electrochemical Carbon Dioxide Reduction to Formate.

Electrochemical carbon dioxide reduction reaction (ECO2RR) is a promising approach to synthesize fuels and value-added chemical feedstocks while reducing atmospheric CO2 levels. Here, high surface area cerium and sulfur-doped hierarchical bismuth oxide nanosheets (Ce@S-Bi2O3) are develpoed by a solvothermal method. The resulting Ce@S-Bi2O3 electrocatalyst shows a maximum formate Faradaic efficiency (FE) of 92.5% and a current density of 42.09 mA cm-2 at -1.16 V versus RHE using a traditional H-cell system. Furthermore, using a three-chamber gas diffusion electrode (GDE) reactor, a maximum formate FE of 85% is achieved in a wide range of applied potentials (-0.86 to -1.36 V vs RHE) using Ce@S-Bi2O3. The density functional theory (DFT) results show that doping of Ce and S in Bi2O3 enhances formate production by weakening the OH* and H* species. Moreover, DFT calculations reveal that *OCHO is a dominant pathway on Ce@S-Bi2O3 that leads to efficient formate production. This study opens up new avenues for designing metal and element-doped electrocatalysts to improve the catalytic activity and selectivity for ECO2RR.

Developing Outstanding Bifunctional Electrocatalysts for Rechargeable Zn-Air Batteries Using High-Purity Spinel-Type ZnCo2 Se4 Nanoparticles.

Zinc-air batteries are gaining popularity as viable energy sources for green energy storage technologies. The cost and performance of Zn-air batteries are mostly determined by the air electrodes in combination with an oxygen electrocatalyst. This research aims at the particular innovations and challenges relating to air electrodes and related materials. Here, a nanocomposite of ZnCo2 Se4 @rGO that exhibits excellent electrocatalytic activity for the oxygen reduction reaction, ORR (E1/2  = 0.802 V), and oxygen evolution reaction, OER (η10  = 298 mV@10 mA cm-2 ) is synthesized. In addition, a rechargeable zinc-air battery with ZnCo2 Se4 @rGO as the cathode showed a high open circuit voltage (OCV) of 1.38 V, a peak power density of 210.4 mW cm-2 , and outstanding long-term cycling stability. The electronic structure and oxygen reduction/evolution reaction mechanism of the catalysts ZnCo2 Se4 and Co3 Se4 are further investigated using density functional theory calculations. Finally, a perspective for designing, preparing, and assembling air electrodes is suggested for the future developments of high-performance Zn-air batteries.

Tuning the interfacial electronic transitions of bi-dimensional nanocomposites (pGO/ZnO) towards photocatalytic degradation and energy application.

The two-dimensional carbonaceous nanocomposites tend to have extreme capacitance and catalysis activity because of their surface tunability of oxygenated moieties aiding in photocatalytic degradation. Herewith, we performed microwave-assisted alkaline treatment of graphene oxide sheets to attain defective sites on the graphitic surface by altering microwave parameters. The synergism of zinc oxide (ZnO) on the graphitic surface impacts electronic transitions paving paths for vacant oxygen sites to promote photocatalytic degradation and catalytic activity. The photocatalytic efficiency of the synthesized material for the degradation of rhodamine B (RhB) because of its susceptibility in industrial effluents, and the degradation rate was estimated to be around 87.5% within a short span of 30 min by utilizing UV irradiation. Concomitantly, the pGO/ZnO coated substrate exhibits a specific capacity of 561.7 mAh/g and incredible coulombic efficiency illustrating pseudocapacitive nature. Furthermore, on subjecting the composite modified electrode to oxygen evolution catalysis due to the vacant sites located at the lattice edges attributing to the d-d coulombic interaction within the local electron clouds possessing a low overpotential of 205 mV with a Tafel slope of 84 mV/dec. This modest approach boosts an eco-friendly composite to develop photocatalytic degradability and bifunctional catalytic activity for futuristic necessity.

Simple Colorimetric and Fluorescence Chemosensing Probe for Selective Detection of Sn2+ Ions in an Aqueous Solution: Evaluation of the Novel Sensing Mechanism and Its Bioimaging Applications.

An easily accessible colorimetric and fluorescence probe 4-((3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-yl)amino)benzenesulfonamide (4CBS) was successfully developed for the selective and sensitive detection of Sn2+ in an aqueous solution. The sensing mechanism involves reduction of -C═O into -C-OH groups in 4CBS upon the addition of Sn2+, which initiates the fluorescence turn-on mode. A better linear relationship was achieved between fluorescence intensity and Sn2+ concentration in the range of 0-62.5 µM, with a detection limit (LOD) of 0.115 µM. The binding mechanism of 4CBS for Sn2+ was confirmed by Fourier transform infrared analysis, NMR titrations, and mass (electrospray ionization) spectral analysis. Likewise, the proposed sensing mechanism was supported by quantum chemical calculations. Moreover, bioimaging studies demonstrated that the chemosensing probe 4CBS is an effective fluorescent marker for the detection of Sn2+ in living cells and zebrafish. Significantly, 4CBS was able to discriminate between Sn2+ in human cancer cells and Sn2+ in normal live cells.

Simple Fluorescence Turn-On Chemosensor for Selective Detection of Ba2+ Ion and Its Live Cell Imaging.

A phenoxazine-based fluorescence chemosensor 4PB [(4-(tert-butyl)-N-(4-((4-((5-oxo-5H-benzo[a]phenoxazin-6-yl)amino)phenyl)sulfonyl)phenyl)benzamide)] was designed and synthesized by a simple synthetic methods. The 4PB fluorescence chemosensor selectively detects Ba2+ in the existence of other alkaline metal ions. In addition, 4PB showed high selectivity and sensitivity for Ba2+ detection. The detection limit of 4PB was 0.282 µM and the binding constant was 1.0 × 106 M-1 in CH3CN/H2O (97.5:2.5 v/v, HEPES = 1.25 mM, pH 7.3) medium. This chemosensor functioned through the intramolecular charge transfer (ICT) mechanism, which was further confirmed by DFT studies. Live cell imaging in MCF-7 cells confirmed the cell permeability of 4PB and its capability for specific detection of Ba2+ in living cells.

Environmentally Benign Carbon Nanodots Prepared from Lemon for the Sensitive and Selective Fluorescence Detection of Fe(III) and Tannic Acid.

Photoluminescent carbon nanodots (CNDs) were prepared using a biocarbon source of lemon extract. The obtained CNDs are of spherical shape and are enriched with the carboxylic acid fucntionalities. CNDs exhibited a fluorescence emission at 445 nm and unveiled blue luminescence in ultraviolet excitation. The influences of pH and ionic strength toward the stability of CNDs were investigated in detail and the obtained stability authenticates their applicability in different environmental conditions. The competitive binding of Fe3+ with CNDs quenches the fluorescence behavior of CNDs and was further quenched with the selective complex formation of Fe3+ with tannic acid (TA). The interference experiments specified that CNDs-Fe3+ assembly selectively detected TA and the co-existing molecules have not influenced the quenching effect of TA with CNDs-Fe3+. The analytical reliability of constructed sensor was validated from the recovery obtained in the range of 91.66-107.02% in real samples. Thus the low cost and environmentally benign CNDs prepared from natural biomass provide new avenues in the fluorescence detection of biologically significant metal ions and biomolecules, facilitating their competency in on-site applications of real environmental samples.

Bifunctional Electrocatalyst of Pd-C@MoS2-RGO Hybrid Nanostructures-Size Confined Green Synthesis for Direct Alcohol Fuel Cells.

The objective of the present study was to enhance physical interaction between noble metal catalysts (Pd QDs) and support (MoS2/RGO) using in-situ carbon atom and improve its bifunctional activity towards alcohol oxidation and water oxidation. A few layers of two-dimensional MoS2 nanosheets were synthesized over graphene oxide nanosheets via a simple one-pot green synthesis process. Pd QDs were then placed over MoS2/RGO by a simple green process at room temperature. High resolution transmission electron microscopic (HR-TEM) images revealed that Pd QDs were uniformly distributed over MoS2/RGO nanosheets and dark regions, confirming the existence of MoS2 sheets over graphene sheets. The activity of low quantity Pd QDs (5 weight%) grafted MoS2/RGO hybrid catalyst for electrocatalysis of alcohol and water oxidation reaction was tested. Improved catalytic activity and high peak current response of 11.2 mA cm-2 and 2 mA cm-2 were obtained towards methanol and ethylene glycol oxidation, respectively. Additionally, the oxidation of poisonous intermediates and water were tested with this electrode and enhanced catalytic activity was observed. These characteristic improvements of Pd QDs-MoS2/RGO nanohybrid are due to the smaller size of Pd particles and effective interaction between MoS2 and RGO. Therefore, the proposed catalyst could be a promising candidate as an anode material for energy conversion and storage.

1,4-Naphthoquinone Analogues: Potent Antibacterial Agents and Mode of Action Evaluation.

1,4-Naphthoquinones have antibacterial activity and are a promising new class of compound that can be used to treat bacterial infections. The goal was to improve effective antibacterial agents; therefore, we synthesized a new class of naphthoquinone hybrids, which contain phenylamino-phenylthio moieties as significant counterparts. Compound 4 was modified as a substituted aryl amide moiety, which enhanced the antibacterial activity of earlier compounds 3 and 4. In this study, five bacterial strains Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) were used to evaluate the antibacterial potency of synthesized naphthoquinones using the minimal inhibitory concentration (MIC) method. Most of the studied naphthoquinones demonstrated major antibacterial activity with a MIC of 15.6 µg/mL-500 µg/mL. Selected compounds (5a, 5f and 5x) were studied for the mode of action, using intracellular ROS generation, determination of apoptosis by the Annexin V-FITC/PI assay, a bactericidal kinetic study and in silico molecular modelling. Additionally, the redox potentials of the specified compounds were confirmed by cyclic voltammetry (CV).

One-Pot Facile Synthesis of Pt Nanoparticles Using Cultural Filtrate of Microgravity Simulated Grown P. chrysogenum and Their Activity on Bacteria and Cancer Cells.

Platinum nanoparticles (Pt NPs) was synthesized via a facile and cost competitive ont-pot green mediated synthesis using cell free cultural filtrate (microgravity simulated grown Penicillium chrysogenum) as a reducing agent. The toxicity effect of synthesized Pt NPs toward myoblast C2C12 carcinoma cells was then investigated. The particle size analyzer (DLS) and transmission electron microscopy (TEM) results demonstrates that both NG-Pt NPs and MG-Pt NPS are spherical in shape with an average diameter of 15 nm and 8.5 nm, respectively. The results from UV-visible (UV-vis) spectroscopy and X-ray diffraction (XRD) analysis show a characteristic strong resonance centered at 265 nm and a single crystalline nature, respectively. The results derived from in vitro cytotoxicity showed a significant concentration-dependent decrement in cell viability when C2C12 cells were exposed to Pt NPs. Such decrement in cell viability is because of increased reactive oxygen species (ROS) generation. Cell apoptosis was proved by acridine orange-ethidium bromide (AO/EtBr) dual staining, annexin V-FITC/PI-staining and immunocytochemistry. Moreover, the protein expression of both (i) apoptosis related proteins such as cas-3 and cas-9, (ii) inflammatory response proteins such as TNF-α, TGF-ß and NF-κB were significantly upregulated in MG-Pt NPs treated cells than NG-Pt NPs treated cells. Uptake and intracellular localization of MG-Pt NPs caused by accumulation of autophagosomes in C2C12 cells and bacterial cells, indicate that synthesized MG-Pt NPs enable for the swift cell apoptosis than NG-Pt NPs. Interestingly, At the concentration of 40 and 80 µg/ml MG-Pt NPs showed more potent cytotoxicity toward cancer cells while, under identical concentration, NG-Pt NPs exhibited rather lower cytotoxicity. Overall, our results demonstrated that MG-Pt NPs could be selectively inhibit the growth of cancer cells via ROS-mediated nucleus NF-κB and caspases activation when compared to NG-Pt NPs.

The Influence of Chitosan Substrate and Its Nanometric Form Toward the Green Power Generation in Sediment Microbial Fuel Cell.

A simple, environmental friendly and biologically important sediment interfaced fuel cell was developed for the green energy generation. The soil sediment used for the study is enriched of rich anthropogenic free organic carbon, sufficient manganese and high level potassium contents as evidenced from the geochemical characterizations. The saccharides produced by the catalytic reaction of substrate chitosan were utilized for the growth of microorganisms and electron shuttling processes. Chitosan substrate influenced sediment microbial fuel cells exhibited the nearly two fold power increment over the substrate free fuel cells. The fuel cell efficiencies were further increased by bringing the substrate chitosan at nanometric level, which is nearly three and two fold higher than that of substrate free and chitosan influenced sediment microbial fuel cells, respectively, and the influential parameters involved in the power and longevity issues were addressed with different perspectives.

Synthesis of Iron Nanoparticles Using Azadirachta indica Extract and Its Catalytic Activity Toward Nitrophenol Reduction.

A simple, hasty and eco-friendly approach for the synthesis of iron nanoparticles has been developed using the medicinally important Azadirachta indica extract, which act as both reducing and stabilizing agent. The formation and morphological properties of iron nanoparticles as a function of metallic precursor and Azadirachta indica extract concentration have been investigated. The influence of solvent over the size and texture of iron nanoparticles has also been evaluated in detail. The thermal behavior of prepared nanoparticles was identified from thermogravimetric analysis. Furthermore, the catalytic activity of prepared iron nanoparticles toward the reduction of p-nitrophenol was analyzed and the reduction process was occurred within 30 sec. The cost and time efficient biosynthesis process and excellent catalytic activity of the prepared iron nanoparticles construct this protocol attractive.

Facile Instep Synthesis of Palladium Nanoparticle/Carbon@Carbon Nanotube Composites for Electrooxidation of Xylitol.

The development of a facile, instep, and eco-friendly synthesis method of mono-dispersed low quantity palladium nanoparticle/carbon@functionllized carbon nanotube composite (Pd@C-f-CNT)electrocatalytic material was developed for use in the electrooxidation of xylitol. The prepared nanocatalyst was analyzed by powder X-ray diffraction analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning and transmission electron microscopy. The electrocatalytic studies were performed using voltammetric methods. Formation of Pd NPs was observed within 2 min. The microscopic analysis showed 5- to 10-nm-sized Pd NPs that uniformly covered the CNT. The instep-formed carbon helped to improve the electrocatalytic activity of the catalyst. Our proposed method provides new insight for the development of highly efficient metal NPs/CNT nanocatalyst for direct alcohol fuel cell applications.

A seed-like structured Mo@ZrS2 catalyst on graphene nanosheets for boosting the performance of rechargeable Zn-air batteries.

Novel composite materials are being studied by researchers for energy storage and renewable energy applications. Here, a seed-like Mo-doped ZrS2 catalyst was developed on a reduced graphene oxide (rGO) surface by an annealing and hydrothermal method. Using photoelectron spectroscopy, scanning microscopy, and X-ray diffraction analyses, the structure of Mo@ZrS2/rGO and the impact of heteroatoms are demonstrated, providing insight into the catalyst. Furthermore, it is demonstrated that Mo@ZrS2/rGO has been utilized as an efficient energy storage electrocatalyst by offering a very low half-wave potential of 0.80 V for the oxygen reduction reaction in an alkaline solution. Furthermore, Zn-air batteries with a high-power density of 128.6 mW cm-2 and exceptional cycling stability are demonstrated by the developed array electrocatalyst. Ultimately, the research findings suggest novel perspectives on the structure of ZrS2 nanoseeds created by Mo surface doping, promote the usage of Zn-air batteries in practical scenarios, and offer a fascinating idea for creating a redox electrocatalyst.

Low-Cost Hydrogen Production from Alkaline/Seawater over a Single-Step Synthesis of Mo3 Se4 -NiSe Core-Shell Nanowire Arrays.

The rational design and steering of earth-abundant, efficient, and stable electrocatalysts for hydrogen generation is highly desirable but challenging with catalysts free of platinum group metals (PGMs). Mass production of high-purity hydrogen fuel from seawater electrolysis presents a transformative technology for sustainable alternatives. Here, a heterostructure of molybdenum selenide-nickel selenide (Mo3 Se4 -NiSe) core-shell nanowire arrays constructed on nickel foam by a single-step in situ hydrothermal process is reported. This tiered structure provides improved intrinsic activity and high electrical conductivity for efficient charge transfer and endows excellent hydrogen evolution reaction (HER) activity in alkaline and natural seawater conditions. The Mo3 Se4 -NiSe freestanding electrodes require small overpotentials of 84.4 and 166 mV to reach a current density of 10 mA cm-2 in alkaline and natural seawater electrolytes, respectively. It maintains an impressive balance between electrocatalytic activity and stability. Experimental and theoretical calculations reveal that the Mo3 Se4 -NiSe interface provides abundant active sites for the HER process, which modulate the binding energies of adsorbed species and decrease the energetic barrier, providing a new route to design state-of-the-art, PGM-free catalysts for hydrogen production from alkaline and seawater electrolysis.

Strong intramolecular charge-transfer effect strengthening naphthoquinone-based chemosensor: Experimental and theoretical evaluation.

An aminophenol-linked naphthoquinone-based fluorometric and colorimetric chemosensor 2-chloro-3-((3-hydroxyphenyl) amino) naphthalene-1,4-dione (2CAN-Dione) was synthesized for selective detection of Sn2+ ion in aqueous solution. The amine and conversion of carbonyl into carboxyl groups play a vital role in the sensing mechanism when Sn2+ is added to 2CAN-Dione. Comprehensive characterization of the sensor was carried out using standard spectral and analytical approaches. Because of the intramolecular charge transfer (ICT) effect and the turn-on sensing mode, the strong fluorometric emission towards Sn2+ was observed at about 435 nm. The chemosensor exhibited good selectivity for Sn2+ in the presence of coexisting metal ions. An improved linear connection was established with a low limit of detection (0.167 µM). FT-IR, 1H NMR, 13C NMR, and quantum chemistry methods were performed to verify the binding coordination mechanism. The chemosensing probe 2CAN-Dione was successfully employed in bioimaging investigations, demonstrating that it is a reliable fluorescent marker for Sn2+ in human cancer cells.

Fast parallel detection of feline panleukopenia virus DNA by multi-channel microchip electrophoresis with programmed step electric field strength.

A multi-channel microchip electrophoresis using a programmed step electric field strength (PSEFS) method was investigated for fast parallel detection of feline panleukopenia virus (FPV) DNA. An expanded laser beam, a 10× objective lens, and a charge-coupled device camera were used to simultaneously detect the separations in three parallel channels using laser-induced fluorescence detection. The parallel separations of a 100-bp DNA ladder were demonstrated on the system using a sieving gel matrix of 0.5% poly(ethylene oxide) (M(r) = 8 000 000) in the individual channels. In addition, the PSEFS method was also applied for faster DNA separation without loss of resolving power. A DNA size marker, FPV DNA sample, and a negative control were simultaneously analyzed with single-run and one-step detection. The FPV DNA was clearly distinguished within 30 s, which was more than 100 times faster than with conventional slab gel electrophoresis. The proposed multi-channel microchip electrophoresis with PSEFS was demonstrated to be a simple and powerful diagnostic method to analyze multiple disease-related DNA fragments in parallel with high speed, throughput, and accuracy.

How Structure-Function Relationships of 1,4-Naphthoquinones Combat Antimicrobial Resistance in Multidrug-Resistant (MDR) Pathogens.

Antimicrobial resistance (AMR) is one of the top ten health-related threats worldwide. Among several antimicrobial agents, naphthoquinones (NQs) of plant/chemical origin possess enormous structural and functional diversity and are effective against multidrug-resistant (MDR) pathogens. 1,4-NQs possess alkyl, hydroxyl, halide, and metal groups as side chains on their double-ring structure, predominantly at the C-2, C-3, C-5, and C-8 positions. Among 1,4-NQs, hydroxyl groups at either C-2 or C-5 exhibit significant antibacterial activity against Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. (ESKAPE) and MDR categories. 1,4-NQs exhibit antibacterial activities like plasmids curing, reactive oxygen species generation, efflux pumps inhibition, anti-DNA gyrase activity, membrane permeabilization, and biofilm inhibition. This review emphasizes the structure-function relationships of 1,4-NQs against ESKAPE and MDR pathogens based on a literature review of studies published in the last 15 years. Overall, 1,4-NQs have great potential for counteracting the antimicrobial resistance of MDR pathogens.

Synergistic and Additive Effects of Menadione in Combination with Antibiotics on Multidrug-Resistant Staphylococcus aureus: Insights from Structure-Function Analysis of Naphthoquinones.

Antimicrobial resistance (AMR) interferes with the effective treatment of infections and increases the risk of microbial spread and infection-related illness and death. The synergistic activities of combinations of antimicrobial compounds offer satisfactory approaches to some extent. Structurally diverse naphthoquinones (NQs) including menadione (-CH3 group at C2) exhibit substantial antimicrobial activities against multidrug-resistant (MDR) pathogens. We explored the combinations of menadione with antibiotic ciprofloxacin or ampicillin against Staphylococcus aureus and its biofilms. We found an additive (0.590 %) were also observed. However, preformed biofilms were not affected. Dent formation was also evident in S. aureus treated with the test compounds. The structure-function relationship (SFR) of NQs was used to determine and predict their activity pattern against pathogens. Analysis of 10 structurally distinct NQs revealed that the compounds with -Cl, -Br, -CH3 , or -OH groups displayed the lowest MICs (32-256 µg/mL). Furthermore, 1,4-NQs possessing a halogen or -CH3 moiety showed elevated ROS activity, whereas molecules with an -OH group affected cell integrity. Improved activity of antimicrobial combinations and SFR approaches are significant in antimicrobial therapies.