Recent Progress in Emerging Two-Dimensional Transition Metal Carbides

Enhanced electrochemical nitrate reduction to ammonia with nanostructured Mo2C on carbon nanotube-reduced graphene oxide hybrid support

The electrochemical nitrate reduction reaction (NO3-RR) is emerging as a promising method for ammonia production under ambient conditions while simultaneously addressing nitrate pollution. Due to the complexity of NO3-RR, which involves multi-electron/proton transfer and competes with the hydrogen evolution reaction (HER), the development of efficient electrocatalysts with high activity and stability is crucial. In this study, we report the use of Mo2C nanoparticles homogeneously dispersed on a carbon nanotube-reduced graphene oxide hybrid support (Mo2C/CNT-RGO) as an effective electrocatalyst for NO3-RR. The three-dimensional CNT-RGO hybrid provides a large surface area for electrolyte contact, enhanced electrical conductivity, and prevents the aggregation of Mo2C nanoparticles. Consequently, the Mo2C/CNT-RGO electrocatalyst demonstrated high NO3-RR performance, achieving a maximum NH3 production rate of 5.23 mg h-1 cm-2 with a faradaic efficiency of 95.9%. Mo2C/CNT-RGO also exhibited excellent long-term stability during consecutive cycling tests. This work presents a promising strategy for developing high-performance and durable NO3-RR electrocatalysts.

First-Principles Calculations and Machine Learning of Hydrogen Evolution Reaction Activity of Nonmetallic Doped β-Mo2C Support Pt Single-Atom Catalysts

The most widely used catalyst for the hydrogen evolution reaction (HER) is Pt, but the high cost and low abundance of Pt need to be urgently addressed. Single-atom catalysts (SACs) have been an effective means of improving the utilization of Pt atoms. In this work, we used a nonmetal (NM = B, N, O, F, Si, P, S, Cl, As, Se, Br, Te, and I) doped β-Mo2C (100) C-termination surface as the support, with Pt atoms dispersed on the support surface to construct Pt@NM-Mo2C. Using density functional theory (DFT) calculations, we selected catalysts with excellent HER activity. Among 117 candidate catalysts, 49 catalysts exhibited ideal catalytic performance with Gibbs free energy of hydrogen intermediate (H*) adsorption (ΔGH*) values less than 0.2 eV. The ΔGH* values of 16 catalysts were even lower than that of Pt (ΔGH* ≈ 0.09 eV), with PtI@N2/4-a-Mo2C demonstrating the best performance (ΔGH* = -0.01 eV). Combined with electronic structure analysis, we could understand the impact of charge transfer between Pt and the underlying NM atoms on the strength of the Pt-H bond, thereby promoting HER activity. Using machine learning (ML), we identified that the primary influencing factors of the HER catalytic activity in the Pt@NM-Mo2C system were the Bader charge transfer of Pt (NePt), the d-band center of Pt (εdPt), and the atomic radius of NM (RNM), with NePt having the greatest impact on the HER catalytic activity.

Metal-organic framework (MOF) integrated Ti3C2 MXene composites for CO2 reduction and hydrogen production applications: a review on recent advances and future perspectives

Titanium carbide (Ti3C2) MXenes due to their structural and optical characteristics rapidly emerged as the preferred material, particularly in catalysis and energy applications. On the other hand, because of its enormous surface/volume ratio and porosity, Metal-organic Frameworks (MOFs) show promise in several areas, including catalysis, delivery, and storage. The potential to increase the applicability of these magic compounds might be achieved by taking advantage of the inherent flexibility in design and synthesis, and optical characteristics of MXenes. Thus, coupling MOF with Ti3C2 MXenes to construct hybrid composites is considered promising in a variety of applications, including energy conversion and storage. This paper presents a systematic discussion of current developments in Ti3C2 MXenes/MOF composites for photocatalytic reduction of CO2, and production of hydrogen through water splitting. Initially, the overview and characteristics of MXenes and MOFs are independently discussed and then a detailed investigation of efficiency enhancement is examined. Different strategies such as engineering aspects, construction of binary and ternary composites and their efficiency enhancement mechanism are deliberated. Finally, different strategies to explore further in various other applications are suggested. Although Ti3C2 MXenes/MOF composites have not yet been thoroughly investigated, they are potential photocatalysts for the production of solar fuel and ought to be looked into further for a range of applications.

High-Density Dual-Structure Single-Atom Pt Electrocatalyst for Efficient Hydrogen Evolution and Multimodal Sensing

Herein, we report a high-density dual-structure single-atom catalyst (SAC) by creating a large number of vacancies of O and Ti in two-dimensional (2D) Ti3C2 to immobilize Pt atoms (SA Pt-Ti3C2). The SA Pt-Ti3C2 showed excellent performance toward the pH-universal electrochemical hydrogen evolution reaction (HER) and multimodal sensing. For HER catalysis, compared to the commercial 20 wt % Pt/C, the Pt mass activities of SA Pt-Ti3C2 at the overpotentials of ∼30 and 110 mV in acid and alkaline media are 45 and 34 times higher, respectively. More importantly, during the alkaline HER process, an interesting synergetic effect between Pt-C and Pt-Ti sites that dominated the Volmer and Heyrovsky steps, respectively, was revealed. Moreover, the SA Pt-Ti3C2 catalyst exhibited high sensitivity (0.62-2.65 μA μM-1) and fast response properties for the multimodal identifications of ascorbic acid, dopamine, uric acid, and nitric oxide under the assistance of machine learning.

A review of etching methods and applications of two-dimensional MXenes

MXenes have been attracting much attention since their introduction due to their amazing properties such as unique structure, good hydrophilicity, metal-grade electrical conductivity, rich surface chemistry, low ionic diffusion resistance, and excellent mechanical strength. It is noteworthy that different synthesis methods have a great influence on the structure and properties of MXenes. In recent years, some modification strategies of MXenes with unique insights have been developed with the increasing research. In summary, this paper reviews and summarizes the recent research progress of MXenes from the perspective of preparation processes (including hydrofluoric acid direct etching, fluoride/concentrated acid hybrid etching, fluoride melt etching, electrochemical etching, alkali-assisted etching and Lewis acid etching strategies), which can provide valuable guidance for the preparation and application of high-performance MXenes-based materials.

Interlayer manipulation of bio-inspired Ti3C2Tx nanocontainer through intercalation of amino acid molecules to dramatically boosting uranyl hijacking capability from seawater

More than 4.5 billion tons of unconventional uranium resources [UO2(CO3)3]4- are uniformly dissolved in seawater, providing a sustainable and abundant fuel source for the development of nuclear energy. Herein, we presented a rational design and development of Ti3C2Tx nanocontainer inspired by the exceptional selectivity and affinity exhibited by superb-uranyl proteins through amino acid intercalation. The amino acid intercalation of Ti3C2Tx demonstrated exceptional UO22+ capture capacity (Arg-Ti3C2Tx, His-Ti3C2Tx, and Lys-Ti3C2Tx with qmax values of 594.46, 846.04, and 1030.17 mg/g). Furthermore, these intercalated materials exhibited remarkable sequestration efficiency and selectivity (Uinitial = ∼45.2 ∼7636 μg/L; ∼84.45% ∼98.08%; and ∼2.72 ×104 ∼1.28 ×105 KdU value), despite the presence of an overwhelming surplus of Na+, Ca2+, Mg2+, and Co2+ ions. Significantly, even in the 0.3 M NaHCO3 solution and surpassing 103-fold of the Na3VO4 system, the adsorption efficiency of Lys-Ti3C2Tx still achieved a remarkable 63.73% and 65.05%. Moreover, the Lys-Ti3C2Tx can extract ∼30.23 ∼8664.03 μg/g uranium after 24 h contact in ∼13.3 ∼5000 μg/L concentration from uranium-spiked natural seawater. The mechanism analysis revealed that the high binding capability can be attributed to the chelation of carboxyl and amino groups with uranyl ions. This innovative state-of-the-art approach in regulating uranium harvesting capability through intercalation of amino acid molecules provides novel insights for extracting uranium from seawater.

Two-Dimensional SnS Mediates NiFe-LDH-Layered Electrocatalyst toward Boosting OER Activity for Water Splitting

NiFe-layered double hydroxides (NiFe-LDHs), as promising electrocatalysts, have received significant research attention for hydrogen and oxygen generation through water splitting. However, the slow oxidation kinetics of NiFe-LDH, due to the limited number of active sites and the low conductivity, hinders the improvement of the water-splitting efficiency. Therefore, to overcome the obstacles, two-dimensional (2D) SnS was first explored to tailor the prepared NiFe-LDH via the hydrothermal method. A NiFe-LDH/SnS heterojunction is built, which is observed from the microstructural investigations. SnS incorporation could greatly improve the conductivity of the NiFe-LDH sheets, which was reflected by the reduced charge transfer resistance. Moreover, SnS layers modulated the electronic environment around the active sites, favoring the adsorption of intermediates during the oxygen evolution reaction (OER) process, which was verified by density functional theory calculations. A synergistic effect induced by the NiFe-LDH/SnS heterostructure promoted the OER activities in electrical, electronic, and energetic aspects. Consequently, the as-prepared NiFe-LDH/SnS electrocatalyst greatly improved the electrocatalytic performance, exhibiting 20% and 27% reductions in the overpotential and Tafel slope compared with those of pristine NiFe-LDH, respectively. The results provide a strategy for regulating NiFe-based electrocatalysts by using emerging 2D materials to enhance water-splitting efficiency.

First Principles Study of the Structure-Performance Relation of Pristine Wn+1Cn and Oxygen-Functionalized Wn+1CnO2 MXenes as Cathode Catalysts for Li-O2 Batteries

Li-O2 batteries are considered a highly promising energy storage solution. However, their practical implementation is hindered by the sluggish kinetics of the oxygen reduction (ORR) and oxygen evolution (OER) reactions at cathodes during discharging and charging, respectively. In this work, we investigated the catalytic performance of Wn+1Cn and Wn+1CnO2 MXenes (n = 1, 2, and 3) as cathodes for Li-O2 batteries using first principles calculations. Both Wn+1Cn and Wn+1CnO2 MXenes show high conductivity, and their conductivity is further enhanced with increasing atomic layers, as reflected by the elevated density of states at the Fermi level. The oxygen functionalization can change the electronic properties of WC MXenes from the electrophilic W surface of Wn+1Cn to the nucleophilic O surface of Wn+1CnO2, which is beneficial for the activation of the Li-O bond, and thus promotes the Li+ deintercalation during the charge-discharge process. On both Wn+1Cn and Wn+1CnO2, the rate-determining step (RDS) of ORR is the formation of the (Li2O)2* product, while the RDS of OER is the LiO2* decomposition. The overpotentials of ORR and OER are positively linearly correlated with the adsorption energy of the RDS LixO2* intermediates. By lowering the energy band center, the oxygen functionalization and increasing atomic layers can effectively reduce the adsorption strength of the LixO2* intermediates, thereby reducing the ORR and OER overpotentials. The W4C3O2 MXene shows immense potential as a cathode catalyst for Li-O2 batteries due to its outstanding conductivity and super-low ORR, OER, and total overpotentials (0.25, 0.38, and 0.63 V).

Ultrasensitive detection of genetic variation based on dual signal amplification assisted by isothermal amplification and cobalt oxyhydroxide nanosheets/quantum dots

PML/RARα fusion gene (P/R) is the characteristic signature genetic variation of acute promyelocytic leukemia (APL). Here, by integrating triple-stranded DNA hybridization-triggered strand displacement amplification (tri-HT SDA) and cobalt oxyhydroxide nanosheets/quantum dots (CoOOH/QD)-based amplification, we constructed a novel biosensor of easy-operating, time-saving and high sensitivity for detecting P/R to meet clinical needs. Owing to the specific recognition and efficient amplification of tri-HT SDA as well as impressive anti-interference and considerable amplification of CoOOH/QD, this biosensor demonstrated a wide dynamic range (10 fM to 10 nM) with a low limit of detection (5.50 fM) in P/R detection. Additionally, this biosensor could detect P/R spiked into human serum with good recoveries and relative standard deviation (RSD), thus potentially exhibiting ultrasensitive and specific nuclear acid sequence detection ability in clinical diagnosis owing to combing isothermal amplification and nanomaterials.

Recent Progress on Phase Engineering of Nanomaterials

As a key structural parameter, phase depicts the arrangement of atoms in materials. Normally, a nanomaterial exists in its thermodynamically stable crystal phase. With the development of nanotechnology, nanomaterials with unconventional crystal phases, which rarely exist in their bulk counterparts, or amorphous phase have been prepared using carefully controlled reaction conditions. Together these methods are beginning to enable phase engineering of nanomaterials (PEN), i.e., the synthesis of nanomaterials with unconventional phases and the transformation between different phases, to obtain desired properties and functions. This Review summarizes the research progress in the field of PEN. First, we present representative strategies for the direct synthesis of unconventional phases and modulation of phase transformation in diverse kinds of nanomaterials. We cover the synthesis of nanomaterials ranging from metal nanostructures such as Au, Ag, Cu, Pd, and Ru, and their alloys; metal oxides, borides, and carbides; to transition metal dichalcogenides (TMDs) and 2D layered materials. We review synthesis and growth methods ranging from wet-chemical reduction and seed-mediated epitaxial growth to chemical vapor deposition (CVD), high pressure phase transformation, and electron and ion-beam irradiation. After that, we summarize the significant influence of phase on the various properties of unconventional-phase nanomaterials. We also discuss the potential applications of the developed unconventional-phase nanomaterials in different areas including catalysis, electrochemical energy storage (batteries and supercapacitors), solar cells, optoelectronics, and sensing. Finally, we discuss existing challenges and future research directions in PEN.

Phase Engineering of Molybdenum Carbide-Cobalt Heterostructures for Long-Lasting Zn-Air Batteries

Developing highly active and robust oxygen catalysts is of great significance for the commercialization of Zn-air batteries (ZABs) with long-life stability. Herein, heterostructured catalysts comprising molybdenum carbide and metallic Co are prepared by a simple dicyandiamide-assisted pyrolysis strategy. Importantly, the crystalline phase of molybdenum carbide in the catalysts can be carefully regulated by adjusting the CoMo-imidazole precursor and dicyandiamide ratio. The electronic configuration of Co and Mo centers as well as the phase-dependent oxygen reduction reaction performance of these heterostructures (β-Mo2C/Co, β-Mo2C/η-MoC/Co, and η-MoC/Co) was disclosed. A highly active η-MoC/Co cathode enables ZABs with outstanding long-term stability over 850 h with a low voltage decaying rate of 0.06 mV·h-1 and high peak power density of 162 mW·cm-2. This work provides a new idea for the rational design of efficient and stable cathode catalysts for ZABs.

Enterobacter hormaechei-Driven Novel Biosynthesis of Tin Oxide Nanoparticles and Evaluation of Their Anti-aging, Cytotoxic, and Enzyme Inhibition Potential

Nanotechnology is a research hotspot that has gained considerable interest due to its potential inferences in the bioscience, medical, and engineering disciplines. The present study uses biomass from the Enterobacter hormaechei EAF63 strain to create bio-inspired metallic tin oxide nanoparticles (SnO2 NPs). The biosynthesized NPs were extensively analyzed using UV spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) techniques. The identification of the crystalline phase was confirmed by XRD. The SEM technique elucidated the morphological characteristics and size of SnO2 NPs. SEM investigation revealed that the SnO2 NPs have a size of 10 nm with spherical morphology. The capping of NPs was confirmed by FTIR analysis that revealed the presence of different compounds found in the biomass of the E. hormaechei EAF63 strain. Later, EDX confirmed the elemental composition of NPs. Moreover, the synthesized SnO2 NPs were employed for important applications including anti-aging, anti-Alzheimer's, anti-inflammatory, anti-larvicidal, and antibacterial action against sinusitis pathogens. The highest value was observed for Streptococcus pyogenes (19.75 ± 0.46), followed by Moraxella catarrhalis (17.49 ± 0.82) and Haemophilus influenzae (15.31 ± 0.73), respectively. Among the used concentrations, the highest inhibition of 76.8 ± 0.93 for 15-lipoxygenase (15-LOX) was observed at 400 μg/mL, followed by 67.4 ± 0.91 for cyclooxygenase-1 (COX-1). So, as an outcome, E. hormaechei-mediated SnO2 NPs might be considered as the safe and effective nanoplatforms for multifunctional biological applications in the field of nanomedicine.

Electrochemical nitrate reduction to high-value ammonia on two-dimensional molybdenum carbide nanosheets for nitrate-containing wastewater upcycling

Electrochemical conversion of nitrate wastewater into high-value ammonia fertilizer has attracted extensive attention in wastewater treatment and resource recovery, but presents great challenges due to complicated reaction pathways and competing side reactions. Herein, we report a feasible method for the successful fabrication of Mo₂C nanosheets (Mo₂C NSs) as electrocatalyst for the electroreduction of nitrate to ammonia. Compared to Mo₂C nanoparticles, the Mo₂C NSs exhibited superior activity and selectivity in NH₃ electrosynthesis with an NH₃ yield rate of 25.2 mg·h^-1·mg^-1_cat. at -0.4 V and a Faradaic efficiency of 81.4 % at -0.3 V versus reversible hydrogen electrode. The X-ray diffraction and transmission electron microscopy characterization verifted the controllable conversion of 2D MoO₂ NSs into 2D Mo₂C NSs. In situ spectroscopic studies and on-line differential electrochemical mass spectrometry revealed the proposed reaction pathway of NO₃^- to NH₃ conversion, *NO₃^- → *NO₂^- → *NO→*NOH → *NH₂OH → *NH₃. Density functional theory calculations further verified the effective N-end NOH pathway with the conversion of *NH₂OH to *NH₂ as the rate-determining step requiring a low energy barrier of 0.58 eV. Importantly, the key hydrogenation of *NO to form *NOH species underwent a lower energy barrier of 0.39 eV compared with the formation of *ONH species (1.06 eV).

Progress and challenges of emerging MXene based materials for thermoelectric applications

To realize sustainable development, more and more countries forwarded carbon neutrality goal. Accordingly, improving the utilization efficiency of traditional fossil fuel is an effective strategy for this great goal. Keeping this in mind, developing thermoelectric devices to recover waste heat energy resulted in the consumption process of fuel is demonstrated to be promising. High performance thermoelectric devices require advanced materials. MXenes are a kind of 2D materials with a layered structure, which demonstrate excellent thermoelectric performance owing to their unique physical, mechanical, and chemical properties. Also, substantial achievement has been gained during the past few years in synthesizing MXene based materials for thermoelectric devices. In this review, the mainstream synthetic routes of MXene from etching MAX were summarized. Significantly, the current state and challenges of research on improving the performance of MXene based thermoelectrics are explored, including pristine MXene and MXene based composites.

Large-Scale Synthesis of Multifunctional Single-Phase Co2 C Nanomaterials

Achieving scalable synthesis of nanoscale transition-metal carbides (TMCs), regarded as substitutes for platinum-group noble metals, remains an ongoing challenge. Herein, a 100-g scale synthesis of single-phased cobalt carbide (Co₂ C) through carburization of Co-based Prussian Blue Analog (Co-PBA) is reported in CO₂ /H₂ atmosphere under mild conditions (230 °C, ambient pressure). Textural property investigations indicate a successful preparation of orthorhombic-phased Co₂ C nanomaterials with Pt-group-like electronic properties. As a demonstration, Co₂ C achieves landmark photo-assisted thermal catalytic CO₂ conversion rates with photo-switched product selectivity, which far exceeds the representative Pt-group-metal-based catalysts. This impressive result is attributed to the excellent activation of reactants, colorific light absorption, and photo-to-thermal conversion capacities. In addition to CO₂ hydrogenation, the versatile Co₂ C materials show huge prospects in antibacterial therapy, interfacial water evaporation, electrochemical hydrogen evolution reaction, and battery technologies. This study paves the way toward unlocking the potential of multi-functional Co₂ C nanomaterials.

Vanadium MXenes materials for next-generation energy storage devices

Batteries and supercapacitors have emerged as promising candidates for next-generation energy storage technologies. The rapid development of new two-dimensional (2D) electrode materials indicates a new era in energy storage devices. MXenes are a new type of layered 2D transition metal carbides, nitrides, or carbonitrides that have drawn much attention because of their excellent electrical conductivity, electrochemical and hydrophilic properties, large surface area, and attractive topological structure. This review focuses on various synthesis methods to prepare vanadium carbide MXenes with and without etchants like hydrofluoric acid, lithium fluoride, and hydrochloric acid to remove the 'A' layers of the MAX phase. The goal is to demonstrate the utilization of a less toxic etching method to achieve MXenes of comparable properties to those prepared by traditional methods. The influence of intercalation on the effect of high interlayer spacing between the MXene layers and the performance of MXenes as supercapacitor and battery electrodes is also addressed in this review. Lastly, the gaps in the current knowledge for vanadium carbide MXenes in synthesis, scalability, and utilization in more energy storage devices were discussed.

State-of-the-art: MXene structures in nano-oncology

Cancer nanomedicine has been investigated widely and boomed in the last two decades, resulting in designing nanostructures with biofunctionalization, giving rise to an "All-in-One" multifunctional platform. The development of rational design technology with extended functionalities brought interdisciplinary researchers to work continuously, aiming to find a prevent or effectively treat the deadly disease of the century. Thus, it led to some Food and Drug Administration (FDA)-approving nano-based formulations for cancer treatment and opening a vast area of promising discoveries by exploiting different nanomaterials. Two-dimensional (2D) materials have recently gained tremendous interest among scientists because of their outstanding structural, optical, electronic, thermal, and mechanical characteristics. Among various 2D nanomaterials, MXenes are a widely studied nanosystem because of their close similarity to graphene analogs. So, it is synthesized using multiple approaches and exploits their inherited properties. But in most cases, surface functionalization techniques are carried out for targeting, site-specific drug clearance, renal clearance, and biocompatible with healthy cells. Thus, fabricating a multimodal agent for mono or combined therapies is also an image-guided diagnostic agent. This review will explain the recent and emerging advancements of MXenes-based composites as a multifunctional theragnostic agent and discuss the possibilities of transferring laboratory research to clinical translation.

Optimized Green Nanoemulsions to Remove Pharmaceutical Enoxacin from Contaminated Bulk Aqueous Solution

We attempted to develop green nanoemulsions (ENE1-ENE5) using capryol-C90 (C90), lecithin, Tween 80, and N-methyl-2-pyrrolidone (NMP). HSPiP software and experimentally obtained data were used to explore excipients. ENE1-ENE5 nanoemulsions were prepared and evaluated for in vitro characterization parameters. An HSPiP based QSAR (quantitative structure-activity relationship) module established a predictive correlation between the Hansen solubility parameter (HSP) and thermodynamic parameters. A thermodynamic stability study was conducted under stress conditions of temperature (from -21 to 45 °C) and centrifugation. ENE1-ENE5 were investigated for the influence of size, viscosity, composition, and exposure time on emulsification (5-15 min) on %RE (percent removal efficiency). Eventually, the treated water was evaluated for the absence of the drug using electron microscopy and optical emission spectroscopy. HSPiP program predicted excipients and established the relationship between enoxacin (ENO) and excipients in the QSAR module. The stable green nanoemulsions ENE-ENE5 possessed the globular size range of 61-189 nm, polydispersity index (PDI) of 0.1-0.53, viscosity of 87-237 cP, and ζ potential from -22.1 to -30.8 mV. The values of %RE depended upon the composition, globular size, viscosity, and exposure time. ENE5 showed %RE value as 99.5 ± 9.2% at 15 min of exposure time, which may be due to the available maximized adsorption surface. SEM-EDX (scanning electron microscopy-X-ray dispersive energy mode) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) negated the presence of ENO in the treated water. These variables were critical factors for efficient removal of ENO during water treatment process design. Thus, the optimized nanoemulsion can be a promising approach to treat water contaminated with ENO (a potential pharmaceutical antibiotics).

Computational Design of a Two-Dimensional Copper Carbide Monolayer as a Highly Efficient Catalyst for Carbon Monoxide Electroreduction to Ethanol

Rationally designing stable and low-cost electrocatalysts with high efficiency is of great significance for the large-scale electrochemical reduction of carbon monoxide (eCOR) to high-value-added multicarbon products. Inspired by the tunable atomic structures, abundant active sites, and excellent properties of two-dimensional (2D) materials, in this work, we designed several novel 2D C-rich copper carbide materials as eCOR electrocatalysts by performing an extensive structural search and comprehensive first-principles computations. According to the computed phonon spectra, formation energies, and ab initio molecular dynamics simulations, we screened out two highly stable candidates, i.e., CuC₂ and CuC₅ monolayers with metallic features. Interestingly, the predicted 2D CuC₅ monolayer exhibits superior eCOR performance for C₂H₅OH synthesis with high catalytic activity (low limiting potential of -0.29 V and small activation energy for C-C coupling of 0.35 eV) and high selectivity (significant suppressing effect on the side reactions). Thus, we predicted that the CuC₅ monolayer holds great potential as an eligible electrocatalyst for CO conversion to multicarbon products, which could motivate more study to develop highly efficient electrocatalysts in similar binary noble-metal compounds.

Proton-donating and chemistry-dependent buffering capability of amino acids for the hydrogen evolution reaction

The hydrogen evolution reaction (HER) has been widely demonstrated to have a strong dependence on pH and on the source of protons, where a clear kinetic advantage arises in acidic conditions over near-neutral and alkaline conditions due to the switch in reactant from H₃O⁺ to H₂O. Playing on the acid/base chemistry of aqueous systems can avoid the kinetic frailties. For example, buffer systems can be used to maintain proton concentration at intermediate pH, driving H₃O⁺ reduction over H₂O. In light of this, we examine the influence of amino acids on HER kinetics at platinum surfaces using rotating disk electrodes. We demonstrate that aspartic acid (Asp) and glutamic acid (Glu) can act not only as proton donors, but also have sufficient buffering action to sustain H₃O⁺ reduction even at large current density. Comparing with histidine (His) and serine (Ser), we reveal that the buffering capacity of amino acids occurs due to the proximity of their isoelectric point (pI) and their buffering pK_a. This study further exemplifies HER's dependence on pH and pK_a and that amino acids can be used to probe this relationship.

Padinjareveetil AK, Pumera M. Edges of Layered FePSe3 Exhibit Increased Electrochemical and Electrocatalytic Activity Compared to Basal Planes

Transition metal trichalcogenphosphites (MPX₃), belonging to the class of 2D materials, are potentially viable electrocatalysts for the hydrogen evolution reaction (HER). Many 2D and layered materials exhibit different magnitudes of electrochemical and electrocatalytic activity at their edge and basal sites. To find out whether edges or basal planes are the primary sites for catalytic processes at these compounds, we studied the local electrochemical and electrocatalytic activity of FePSe₃, an MPX₃ representative that was previously found to be catalytically active. Using scanning electrochemical microscopy, we discovered that electrochemical processes and the HER are occurring at an increased rate at edge-like defects of FePSe₃ crystals. We correlate our observations using optical microscopy, confocal laser scanning microscopy, scanning electron microscopy, and electron-dispersive X-ray spectroscopy. These findings have profound implications for the application of these materials for electrochemistry as well as for understanding general rules governing the electrochemical performance of layered compounds.

Multiphase Molybdenum Carbide Doped Carbon Hollow Sphere Engineering: The Superiority of Unique Double-Shell Structure in Microwave Absorption

In order to achieve excellent electromagnetic wave (EMW) absorption properties, the microstructure design and component control of the absorber are critical. In this study, three different structures made of Mo₂ C/C hollow spheres are prepared and their microwave absorption behavior is investigated. The Mo₂ C/C double-shell hollow spheres consisting of an outer thin shell and an inner rough thick shell with multiple EMW loss mechanisms exhibit good microwave absorption properties. In order to further improve the microwave absorption properties, MoC_1-x /C double-shell hollow spheres with different crystalline phases of molybdenum carbide are prepared to further optimize the EMW loss capability of the materials. Finally, MoC_1-x /C double-shell hollow spheres with α-phase molybdenum carbide have the best microwave absorption properties. When the filling is 20 wt.%, the minimum reflection loss at 1.8 mm is -50.55 dB and the effective absorption bandwidth at 2 mm is 5.36 GHz, which is expected to be a microwave absorber with the characteristics of "thin, light, wide, and strong".

Emerging MoS2 Wafer-Scale Technique for Integrated Circuits

As an outstanding representative of layered materials, molybdenum disulfide (MoS2) has excellent physical properties, such as high carrier mobility, stability, and abundance on earth. Moreover, its reasonable band gap and microelectronic compatible fabrication characteristics makes it the most promising candidate in future advanced integrated circuits such as logical electronics, flexible electronics, and focal-plane photodetector. However, to realize the all-aspects application of MoS2, the research on obtaining high-quality and large-area films need to be continuously explored to promote its industrialization. Although the MoS2 grain size has already improved from several micrometers to sub-millimeters, the high-quality growth of wafer-scale MoS2 is still of great challenge. Herein, this review mainly focuses on the evolution of MoS2 by including chemical vapor deposition, metal-organic chemical vapor deposition, physical vapor deposition, and thermal conversion technology methods. The state-of-the-art research on the growth and optimization mechanism, including nucleation, orientation, grain, and defect engineering, is systematically summarized. Then, this review summarizes the wafer-scale application of MoS2 in a transistor, inverter, electronics, and photodetectors. Finally, the current challenges and future perspectives are outlined for the wafer-scale growth and application of MoS2.

Construction of Cobalt Molybdenum Diselenide Three-phase Heterojunctions for Electrocatalytic Hydrogen Evolution in Acid Medium

Molybdenum diselenide and cobalt diselenide have been commonly implemented in electrocatalytic hydrogen evolution reaction (HER). However, there have been few research on the creation of their three-phase heterojunctions and the associated HER process. Herein, we constructed a three-phase heterostructure sample consisting of orthorhombic CoSe₂ , cubic CoSe₂ and MoSe₂ and we investigated its HER performance. The sample shows microsphere morphology composed of nanosheets with interfacial interactions between the components. It possesses an overpotential of -136 mV at -10 mA cm^-2 in acid medium, which is superior to that of single component and most two-phase heterostructures. Especially, the overpotential at -200 mA cm^-2 is smaller than that of Pt/C. The excellent performance can be attributed to the d-orbital upshift of the Co active sites due to charge redistribution between the three-phase heterojunction and the optimization of the hydrogen free energy. This work provides inspiration for exploring the application of other multi-component heterojunctions in electrocatalytic hydrogen evolution.

Selective H2O2 Electrosynthesis over Defective Carbon from Electrochemical Etching of Molybdenum Carbide

The controllable synthesis of specific defective carbon catalysts is crucial for two-electron oxygen reduction reaction (2e^- ORR) to generate H₂O₂ due to the great potential applications. Herein, the defective carbon catalysts (Mo-CDC-ns) were prepared by an electrochemical activation (ECA) method with Mo₂C/C as a parent. Electrochemical cyclic voltammetry curves, X-ray photoelectron spectroscopy, inductively coupled plasma-mass spectrometry, scanning electron microscopy, and high-resolution transmission electron microscopy confirm the evolution process of a defective carbon structure from the Mo₂C phase in which Mo species are first oxidized to Mo⁶⁺ species and then the latter are dissolved into the solution and defective carbon is simultaneously formed. Raman and electron paramagnetic resonance spectra reveal that the defect types in Mo-CDC-ns are the edge defect and vacancy defect sites. Compared with the parent Mo₂C/C, Mo-CDC-ns exhibit gradually increased kinetic current density and selectivity for H₂O₂ generation with an extension of activation cycles from 10 (Mo-CDC-10) to 30 (Mo-CDC-30). Over Mo-CDC-30, a kinetic current density of 19.4 mA cm^-2 and a selectivity close to 90% in 0.1 M KOH solution were achieved, as well as good stability for H₂O₂ production in an extended test up to 12 h in an H-cell. Graphene planes and Stone Wales 5757-carbon were constructed as basic models for density functional theory calculations. It revealed that the obtained defective structure after the removal of Mo atoms contains the double vacancy at the edge of graphene (Edge-DVC) and the topological defect on the plane of 5757-carbon (5757C-D), which show more moderate reaction free energy for forming *OOH and smaller energy barrier of 2e^- ORR.

Metal-Organic Framework-Derived Fe-Doped Ni3Se4/NiSe2 Heterostructure-Embedded Mesoporous Tubes for Boosting Oxygen Evolution Reaction

It is crucial but challenging to promote sluggish kinetics of oxygen evolution reaction (OER) for water splitting via finely tuning the hierarchical nanoarchitecture and electronic structure of the catalyst. To address such issues, herein we present iron-doped Ni₃Se₄/NiSe₂ heterostructure-embedded metal-organic framework-derived mesoporous tubes (Ni-MOF-Fe-Se-400) realized by an interfacial engineering strategy. Due to the hierarchical nanoarchitecture of conductive two-dimensional nanosheet-constructed MOF-derived mesoporous tubes, coupled with fine tuning of the electronic structure via Fe-doping and interactions between Ni₃Se₄/NiSe₂ heterostructures, the Ni-MOF-Fe-Se-400 catalyst delivers superior OER activity: it requires only a low overpotential of 242 mV to achieve 10 mA cm^-2 (E_j=10), surpassing the benchmark RuO₂ (E_j=10 = 286 mV) and displays exceptional durability in the chronoamperometric i-t test with a small current decay (6.2%) after 72 h. Furthermore, the water splitting system comprises a Ni-MOF-Fe-Se-400 anode and a Pt/C cathode requires a low cell voltage of 1.576 V to achieve E_j=10 with an excellent Faradic efficiency (∼100%), outperforming the RuO₂-Pt/C combination. This work presents a novel interfacial engineering strategy to finely adjust the morphology and electronic structure of the non-noble metal-based OER catalyst via a facile fabrication method.

Diffusion-Mediated Morphological Transformation in Bifunctional Mn2O3/CuO-(VO)3(PO4)2·6H2O for Enhanced Electrochemical Water Splitting

A strategical approach for morphological transformation and heterojunction formation was utilized to suppress the shortcomings of uni-metal oxide electrocatalysts and enhance their bifunctionality. In situ generation of copper oxide (CuO) over the surface of manganese oxide (Mn₂O₃) resulted in a morphological transformation from solid spheres to hollow spherical structures due to the ion-exchange diffusion (Kirkendall effect) of Cu ions into Mn₂O₃ particles. This hollowness resulted in the advancement of the bifunctional electrocatalytic behavior of Mn₂O₃/CuO (overpotential (η₁₀) of 280 mV for an OER and 310 mV for an HER at a current density of 10 mA/cm²) by virtue of increased exposed surface active sites aiding the adsorption of water molecules on the surface. The increased electrochemical active surface area (ECSA/C_dl = 34 mF/cm²) and reduced charge transfer resistance resulted in the formation of Mn₂O₃/CuO hollow spheres to achieve an approximately threefold enhancement in the turnover frequency (TOF) compared to the bare Mn₂O₃. The electrocatalytic efficiency of Mn₂O₃/CuO was further enhanced by virtue of the faster charge transfer coefficient of two-dimensional (2D) vanadyl phosphate hexahydrate (VOP) sheets deposited over its surface. This boosted the overall water splitting with attained overpotential (η₁₀) values of 190 and 220 mV with Tafel slopes of 60 and 105 mV/decade for an OER and HER, respectively. The morphological transformation and formation of an n-p heterojunction between Mn₂O₃ and CuO based on their work function (φ) values evaluated from the density functional theory (DFT) calculation and the effect of the VOP overlayer for faster reaction kinetics at the electrolyte interface resulted in an ∼10-fold increment in TOF values compared to the bare counterpart.

Promoting the Oxygen Evolution Reaction via Morphological Manipulation of a Lamellar Nanorod-Assembled Ni(II)-Pyrazolate Superstructure

Nanoscale pyrazolate-based coordination polymers (CPs) are becoming increasingly popular as electrocatalysts owing to their customizable compositions and structures. However, using them for oxygen evolution reaction (OER) is highly challenging due to their unsatisfactory catalytic efficiency and relatively low stability. Herein, a simple one-step solvothermal process was employed for the fabrication of polycrystalline nickel-pyrazolate [Ni(Pz)] with an unusual lamellar nanorod-assembled microsphere morphology for the first time using ethanol as a green organic solvent via controlling other physical parameters. Meanwhile, the Ni(Pz) structure and morphology are investigated to derive its formation process following the different monomeric feed ratios relying on the metal/ligand interactions of CP. Shaping the Ni(Pz) electrocatalyst in well-oriented lamellar nanorod-assembled microspheres brings the advantage of porosity and high specific surface area, which expedites mass/charge transport and contact with the electrolyte as well as creates less tortuous pathways for charge distribution, thus improving the charge homogeneity. These high-class structural features and polycrystalline nature of Ni(Pz)-E-PVP facilitate amazing catalytic OER activity with a low overpotential of 290 mV at 10 mA cm^-2 and a Tafel slope of only 94 mV dec^-1 beyond the yardstick material (i.e., RuO₂) in alkaline solution. A suite of measurements, entailing X-ray photoelectron spectroscopy and density functional theory calculations, suggest that the rich Ni-N₄ moieties in Ni(Pz)-E-PVP are central species providing adsorption sites for OER intermediates. This facile protocol is prophesied to commence the imminent development of noble metal-free, effective, and low-priced electrocatalysts for OER.

Complementary Adsorption of Binary Levelers for Highly Uniform Cu Micropillars

Highly uniform Cu micropillars were electrodeposited on a Cu seed layer in a micropatterned photoresist in the presence of binary levelers containing pyrrolidine and pyridine functional groups. The adsorption behaviors of binary levelers, i.e., 3-hydroxy-6-(tert-butyl)pyridine and pyridinium tribromide in an electroplating bath were investigated by chronopotentiometry with sequential injection of levelers and linear sweep voltammetry with a rotating disk electrode. From electrochemical analysis, pyridinium tribromide composed of a positively charged pyridine ring was strongly adsorbed on the Cu seed surface, relative to 3-hydroxy-6-(tert-butyl)pyridine. Additional microscopy, surface roughness, and nitrogen concentration analyses revealed that the binary levelers were preferentially adsorbed on the center and the edge region of the Cu seed, resulting in a uniform Cu pillar profile. The possible mechanism of highly uniform Cu pillar deposition was discussed in terms of the adsorption behaviors of the levelers dependent on their molecular structures.

Sodium Hexa-Titanate Nanowires Modified with Cobalt Hydroxide Quantum Dots as an Efficient and Cost-Effective Electrocatalyst for Hydrogen Evolution in Alkaline Media

A novel electrocatalyst with high activity and enhanced durability toward the hydrogen evolution reaction (HER) in alkaline media has been designed and fabricated based on sodium hexa-titanate (Na₂Ti₆O₁₃) nanowires synthesized by a hydrothermal process and modified with Co(OH)₂ quantum dots (QDs) by a facile chemical bath deposition (CBD) method. The current response of the developed Ti/Na₂Ti₆O₁₃/Co(OH)₂ nanocomposite electrode attained 10 mA cm^-2 at an overpotential of 159 mV. The nanocomposite electrode exhibited a high stability at an applied current of 100 mA cm^-2. The remarkable catalytic behavior was achieved with a loading amount of ca. 0.06 mg cm^-2 cobalt hydroxide. This is attributed to the high electrochemically active surface area (EASA) gained by the nanowire-structured substrate and considerable enhancement of electrochemical conductivity with the use of Co(OH)₂ quantum dots as an active material. The superior catalytic activity and high stability show that the developed catalyst is a promising candidate for hydrogen production in alkaline media.

Vanadium Carbide (V4C3) MXene as an Efficient Anode for Li-Ion and Na-Ion Batteries

Li-ion batteries (LIBs) and Na-ion batteries (SIBs) are deemed green and efficient electrochemical energy storage and generation devices; meanwhile, acquiring a competent anode remains a serious challenge. Herein, the density-functional theory (DFT) was employed to investigate the performance of V4C3 MXene as an anode for LIBs and SIBs. The results predict the outstanding electrical conductivity when Li/Na is loaded on V4C3. Both Li2xV4C3 and Na2xV4C3 (x = 0.125, 0.5, 1, 1.5, and 2) showed expected low-average open-circuit voltages of 0.38 V and 0.14 V, respectively, along with a good Li/Na storage capacity of (223 mAhg-1) and a good cycling performance. Furthermore, there was a low diffusion barrier of 0.048 eV for Li0.0625V4C3 and 0.023 eV for Na0.0625V4C3, implying the prompt intercalation/extraction of Li/Na. Based on the findings of the current study, V4C3-based materials may be utilized as an anode for Li/Na-ion batteries in future applications.

Enhanced Antioxidant Ability of PEG-Coated Ce0.5Zr0.5O2-Based Nanofluids for Scavenging Hydroxyl Radicals

The antioxidant therapy to preserve residual hearing is relatively recent, and the search for effective antioxidants is still ongoing. Though nanoceria has shown promising radical-scavenging capability, improving its antioxidant ability and the dispersion stability of its nanofluid, which is critical to the desired site, i.e., cochlea, still remains a major challenge. The objective of the present work is to study the radical-scavenging capability of poly(ethylene glycol) (PEG)-coated CeO₂ and Ce_0.5Zr_0.5O₂ nanoparticles in water and the biologically relevant fluid (PBS buffer). Nanoparticles in the size range of 4.0-9.0 nm are synthesized using the coprecipitation method and characterized using suitable techniques. The scavenging and dispersion stability of the synthesized nanofluid are analyzed using a UV-vis spectrophotometer. It is found that the addition of PEG during the synthesis process promoted the generation of finer nanoparticles with a narrow size distribution and the doping of zirconium produced a large number of defects in the crystallite structure. The PEG coating over the nanoparticles improved the dispersion stability of nanofluids without affecting their surface reactivity, and it is found to be 94 and 80% in water and PBS, respectively, at 500 μM and 60 min, which is maintained till 90 min. The highest scavenging of hydroxyl radicals by PEG-coated Ce_0.5Zr_0.5O₂ is found to be 60%, which is significantly superior to that of CeO₂. The scavenging capability is found to be increased with the concentration of nanoparticles, showing the best scavenging activity at 190 and 150 μM for PEG-coated CeO₂ and Ce_0.5Zr_0.5O₂, respectively, and the scavenging in water is at par with that of PBS, indicating that these nanoparticles are suitable to be used in sites where a biologically relevant fluid is present, e.g., the cochlea. It is proposed that PEG-coated Ce_0.5Zr_0.5O₂ having an average size of ∼ 4 nm can be a potential antioxidant in relevant biomedical applications.

Insight into Point Defects and Complex Defects in β-Mo2C and Carbide Evolution from First Principles

In this paper, first principles method was adopted to investigate the point defects, Vanadium-related defects and defect combinations (vacancy (V), substitutional (S) and/or interstitial (I)) in molybdenum β-Mo₂C and explore the use of first principles calculation data in analysing the link between different carbides and the effects of doping elements. Supercell models with different defect types were established and optimized, and the formation energy data of defects was developed. The structure evolution during the optimization process is analysed in detail to establish the main characteristics of changes and the relevant electronic properties. The data for different types of intrinsic defects and combined defects complexes was developed and key results is analysed. The results show that carbon vacancy (V_C) is stable but does not inevitably exist in pure β-Mo₂C. Interstitial site II is a very unstable position for any type of atoms (Mo, V and C), and analysis of the structure evolution shows that the atom always moves to the interface area near the interstitial site I between two layers. In particular, a C atom can expand the lattice structure when it exists between the layer interfaces. One type of the defects studied, the substitution of Mo with V (designated as ‘S_V-Mo’), is the most stable defect among all single point defects. The data for defect complexes shows that the combination of multiple S_V-Mo defects in the super cell being more stable than the combination of other defects (e.g., ‘V_Mo+I_C’, ‘S_V-Mo+V_C’). The data with increasing S_V-Mo in (Mo, V)₂C system is developed, and typical data (e.g., formation energy) for Mo-rich carbides and V carbides are correlated and the potential of the data in analysing transition of different carbides is highlighted. The relevance of using first principles calculation data in the studying of V-doping and the complex carbides (V- and Mo-rich carbides) evolution in different materials systems and future focus of continuous work is also discussed.

Heterointerface and Defect Dual Engineering in a Superhydrophilic Ni2P/WO2.83 Microsphere for Boosting Alkaline Hydrogen Evolution Reaction at High Current Density

Developing a high-performance electrocatalyst for hydrogen evolution reaction (HER) requires a comprehensive consideration of the three key factors, that is, intrinsic activity, electric conductivity, and active site number. Herein, we report the facile synthesis of a self-supported Ni₂P/WO_2.83 heterointerface microsphere as a highly active and low-cost catalyst for alkaline HER, which has simultaneously addressed these key issues by a joint application of heterointerface construction and defect and architecture engineering strategies. Our density functional theory calculations revealed Ni₂P and WO_2.83 optimized by the interface coupling effect work in concert to improve the intrinsic activity of the catalyst. Importantly, the metalloid Ni₂P in an intimate combination with the oxygen-defect-rich WO_2.83 species endowed the electrocatalyst with high conductivity. Furthermore, the Ni₂P/WO_2.83 electrocatalyst presented a superhydrophilic nanostructure, ensuring abundant active sites and their accessibility. Benefiting from these attributes, the obtained Ni₂P/WO_2.83 heterointerface electrocatalyst exhibited excellent activity along with favorable stability for alkaline HER, especially at high current density, surpassing the most reported non-precious catalysts.

Kinetic and Mechanistic Studies of the Formation of Silver Nanoparticles by Nicotinamide as a Reducing Agent

Here, in the present study, silver nanoparticles (SNPs) in the size range 6-10 nm have been synthesized by a chemical reduction method using nicotinamide (NTA), an anti-inflammatory agent, and cetyltrimethylammonium bromide (CTAB), a good stabilizing agent, to preparing the nanoparticles in the 6-10 nm size range. Kinetic studies on the formation of SNPs have been performed spectrophotometrically at 410 nm (strong plasmon band) in aqueous medium as a function of [AgNO₃], [NTA], [NaOH], and [CTAB]. The plot of ln(A _∞ - A _t ) versus time exhibited a straight line and the pseudo-first-order rate constants of different variables were calculated from its slope. On the basis of experimental findings, a plausible mechanism was proposed for the formation of SNPs colloid. From the mechanism, it is proved that the reduction of silver ions proceeded through the formation of silver oxide in colloidal form by their reaction with hydroxide ions and NTA after performing their function and readily undergo hydrolysis to form nicotinic acid as a hydrolysis product with the release of ammonia gas. The preliminary characterization of the SNPs was carried out by using a UV-visible spectrophotometer. The detailed characterization of SNPs was also carried out using other experimental techniques such as Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and powder X-ray diffraction (PXRD). SNPs show a remarkable catalytic activity of up to 90% for the reduction of the cationic dye methylene blue.

Facile Synthesis of Gold Nanoparticles for Anticancer, Antioxidant Applications, and Photocatalytic Degradation of Toxic Organic Pollutants

In the current study, a facile, rapid, and ecologically safe photosynthesis of gold nanoparticles (AuNPs) that remained stable for 3 months is reported to advocate the main aspects of green chemistry, such as safer solvents and auxiliaries, and the use of renewable feedstock. Zi-AuNPs were phytosynthesized by the aqueous extract of Ziziphus spina-christi leaves, and numerous techniques were employed for their characterization. The results demonstrated the successful phytofabrication of crystalline AuNPs with brownish-black color, spherical nanoparticles with a size between 0 and 10 nm, a plasmon peak at 540 nm, and a surface charge of -25.7 mV. Zi-AuNPs showed an effective photodegradation efficiency (81.14%) against malachite green and a good recycling capacity of 69.2% after five cycles of regeneration. The cytotoxicity test by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay signified a high anticancer efficiency for both Zi-AuNPs and Z. spina-christi extract against human breast cancer cells (MCF7 cell line) with IC₅₀'s of 48 and 40.25 μg/mL, respectively. Highly efficient antioxidant capabilities were proven with 2,2-diphenyl-1-picrylhydrazyl (DPPH) removal percentages of 67.5% for Zi-AuNPs and 92.34% for Z. spina-christi extract.

Black phosphorus coupled bismuth chloride oxide nanocomposites for efficient photocatalytic CO2 reduction

Photocatalytic CO2 reduction to useful CO and CH4 is significantly boosted by black phosphorus (BP) coupled bismuth oxychloride (BiOCl) nanocomposites, presenting an efficient and reliable approach to green and sustainable solar energy conversion.

Catalytic and Medical Potential of a Phyto-Functionalized Reduced Graphene Oxide-Gold Nanocomposite Using Willow-Leaved Knotgrass

In the current study, a simple, environmentally friendly, and cost-effective reduced graphene oxide-gold nanoparticle (rGO-AuNP) nanocomposite was successfully phytosynthesized using the aqueous leaf extract of a common weed found on the Nile banks, Persicaria salicifolia, for the first time. The phytosynthesis of rGO-AuNPs was first confirmed via the color transformation from brown to black as well as throughvarious techniques such as transmission electron microscopy (TEM) and Raman spectroscopy. Two UV-vis peaks at 275 and 530 nm were observed for the nanocomposite with a typical particle size of mostly spherical AuNPs of 15-20 nm. However, other shapes were occasionally detected including rods, triangles, and rhomboids. Existing phytoconstituents such as flavonoids and glycosides in the plant extract were suggested to be responsible for the phytosynthesis of rGO-AuNPs. The excellent catalytic efficacy of rGO-AuNPs against MB degradation was confirmed, and a high antibacterial efficiency against Escherichia coli and Klebsiella pneumonia was also confirmed. Promising antioxidant performance of rGO-AuNPs was also proved. Furthermore, it was concluded that rGO-AuNPs acquired higher efficiency than AuNPs synthesized from the same plant extract in all of the studied applications.

Layer-by-Layer Growth of AA-Stacking MoS2 for Tunable Broadband Phototransistors

The stacking configuration has been considered as an important additional degree of freedom to tune the physical property of layered materials, such as superconductivity and interlayer excitons. However, the facile growth of highly uniform stacking configuration is still a challenge. Herein, the AA-stacking MoS₂ domains with a ratio up to 99.5% has been grown by using the modified chemical vapor deposition through introducing NaCl molecules in the confined space. By tuning the growth time, MoS₂ domains would transit from an AA-stacking bilayer to an AAAAA-stacking five-layer. The epitaxial growth mechanism has been insightfully studied, revealing that the critical nucleation size of the AA-stacking bilayer is 5.0 ± 3.0 μm. Through investigation of the photoluminescence, the photoemission, especially the indirect photoexcitation, is dependent on both the stacking fashion and layer number. Furthermore, by studying the gate-tuned MoS₂ phototransistors, we found a significant dependence on the stacking configuration of MoS₂ of the photoexcitation and a different gate tunable photoresponse. The AAA-stacking trilayer MoS₂ phototransistor delivers a photoresponse of 978.14 A W^-1 at 550 nm. By correction of the external quantum efficiency with external field and illumination power density, it has been found that the photoresponse tunability is dependent on the layer number due to the strong photogating effect. This strategy provides a general avenue for the epitaxial growth of van der Waals film which will further facilitate the applications in a tunable photodetector.

Production of chlorine-containing functional group doped graphene powders using Yucel's method as anode materials for Li-ion batteries

In this study, the one-step electrochemical preparation of chlorine doped and chlorine-oxygen containing functional group doped graphene-based powders was carried out by Yucel's method, with the resultant materials used as anode materials for lithium (Li)-ion batteries. Cl atoms and ClO x (x = 2, 3 or 4) groups, confirmed by X-ray photoelectron spectroscopy analysis, were covalently doped into the graphene powder network to increase the defect density in the graphene framework and improve the electrochemical performance of Li-ion batteries. The microscopic properties of the Cl-doped graphene powder were investigated by scanning electron microscopy and transmission electron microscopy (TEM) analyses. TEM analysis showed that the one-layer thickness of the graphene was approximately 0.33 nm. Raman spectroscopy analysis was carried out to determine the defect density of the graphene structures. The G peak obtained in the Raman spectra is related to the formation of sp2 hybridized carbons in the graphene-based powders. The 2D peak seen in the spectra shows that the synthesized graphene-based powders have optically transparent structures. In addition, the number of sp2 hybridized carbon rings was calculated to be 22, 19, and 38 for the Cl-GP1, Cl-GP2, and Cl-GOP samples, respectively. As a result of the charge/discharge tests of the electrodes as anodes in Li-ion batteries, Cl-GP2 exhibits the best electrochemical performance of 493 mA h g-1 at a charge/discharge current density of 50 mA g-1.

A MXene-Based Bionic Cascaded-Enzyme Nanoreactor for Tumor Phototherapy/Enzyme Dynamic Therapy and Hypoxia-Activated Chemotherapy

The enzyme-mediated elevation of reactive oxygen species (ROS) at the tumor sites has become an emerging strategy for regulating intracellular redox status for anticancer treatment. Herein, we proposed a camouflaged bionic cascaded-enzyme nanoreactor based on Ti₃C₂ nanosheets for combined tumor enzyme dynamic therapy (EDT), phototherapy and deoxygenation-activated chemotherapy. Briefly, glucose oxidase (GOX) and chloroperoxidase (CPO) were chemically conjugated onto Ti₃C₂ nanosheets, where the deoxygenation-activated drug tirapazamine (TPZ) was also loaded, and the Ti₃C₂-GOX-CPO/TPZ (TGCT) was embedded into nanosized cancer cell-derived membrane vesicles with high-expressed CD47 (m_eTGCT). Due to biomimetic membrane camouflage and CD47 overexpression, m_eTGCT exhibited superior immune escape and homologous targeting capacities, which could effectively enhance the tumor preferential targeting and internalization. Once internalized into tumor cells, the cascade reaction of GOX and CPO could generate HClO for efficient EDT. Simultaneously, additional laser irradiation could accelerate the enzymic-catalytic reaction rate and increase the generation of singlet oxygen (¹O₂). Furthermore, local hypoxia environment with the oxygen depletion by EDT would activate deoxygenation-sensitive prodrug for additional chemotherapy. Consequently, m_eTGCT exhibits amplified synergistic therapeutic effects of tumor phototherapy, EDT and chemotherapy for efficient tumor inhibition. This intelligent cascaded-enzyme nanoreactor provides a promising approach to achieve concurrent and significant antitumor therapy.

From half-metallic to magnetic semiconducting triazine g-C4N3: computational designs and insight

We have given, for the first time, physicochemical insight into the electronic structure routes from half-metallic to magnetic semiconducting triazine g-C4N3. To this end, three material designs have been proposed using density functional calculations. In one design, this half-metal is first made semiconducting via hydrogenation, then tailored with B and N atomic species, which gives a new prototype of the antiferromagnetic semiconductor monolayer HC4N3BN. In the others, it can be rendered spin gapless semiconducting with H and B or C, followed by F or O tailoring, which eventually leads to the two new bipolar ferromagnetic semiconductors HC4N3BF and HC4N3CO. These monolayers are considered to be novel materials in spintronics.