Few-layer Nanosheets Research Articles

Two-photon absorption and negative nonlinear refraction in few-layer graphene nanosheets suspensions via liquid-phase exfoliation

Two-photon absorption and negative nonlinear refraction in few-layer graphene nanosheets suspensions via liquid-phase exfoliation

Advanced plasmonic few-layered InSe nanosheet heterojunctions for enhanced photoelectrochemical water splitting

The selenide-based Van der Waals heterojunctions show great potential for the next generation of photoelectronic nanodevices. Herein, we construct a 2D photoanode nanocatalyst that consists of ZnSe nanocrystals with exposed active surfaces coupled with few-layered InSe nanosheets decorated by Au nanoparticles. The resultant ZnSe/AuNPs@InSe multi-heterojunction photoanode demonstrates an outstanding photocurrent density of 4.86 mAcm−2 under AM 1.5 G simulated sunlight (100 mWcm−2), which is 8 times greater than that of the pristine InSe photoanode (0.61 mAcm−2). Moreover, the lifetime of photogenerated charge carriers is extended by a factor of 3. This significant enhancement in photoelectrochemical water splitting in the near-infrared region is attributed to the surface plasmonic effect produced by the modification of Au NPs when bulk InSe is exfoliated into multi-layered flakes. The interfacial coupling effects on carrier transfer dynamics, as revealed by impedance spectroscopy assisted with the First-Principal calculations, show that this photoanode significantly minimizes the internal resistance, boosts the charge carrier separation efficiency, and promotes water oxidation.

Natural Kapok fiber-derived two-dimensional carbonized sheets as sustainable electrode material

Natural biomass-derived carbon nanostructures have attracted research interest because of their unique surface and electrochemical properties. The present study embodied the carbonized micro-nano sheets derived from the low-cost natural source Kapok silk fiber. The material was obtained via a facile thermal pyrolysis process. Diffraction analysis showed a broad graphene structure-like peak, indicating the formation of graphene-like carbon nanosheets. Field emission scanning electron microscope (FESEM) and transmission electron microscopic (TEM) images confirmed the presence of fragmented carbon sheets, some of which were folded to form a tube-like structure. Raman study showed the presence of D and G band with the Id/Ig ratio of 0.96 which indicated the formation of few-layered carbon nanosheets. Furthermore, the electrochemical performance was evaluated for lithium-ion battery as well as supercapacitor. A specific capacity of 465 mAh.g-1 at 0.1 C rate for Li-ion battery and a specific capacitance of 473.61 F.g-1 for supercapacitor have been obtained with the capacitance retention of 95 %. This study provides insights into a strategy for the sustainable production and utilization of natural fiber-based carbon in energy storage systems.

Liquid Nitrogen Exfoliation and Nanodispersion of WS2 for Thermocatalysts.

The efficient and clean exfoliation of single and/or few-layer nanosheets of WS2, a two-dimensional transition metal dichalcogenides, remains a significant challenge. In this study, a simple exfoliation method was proposed to produce ultrathin WS2 nanosheets by combining the liquid nitrogen exfoliation and nanodispersion techniques. This approach efficiently exfoliated WS2 into several layers of nanosheets via rapid temperature changes and mechanical stress without inducing defects or contamination. After five cycles of heating/liquid nitrogen and nanodispersion, the resulting WS2 nanosheets (WS2-5N ND) were confirmed to have been successfully exfoliated into 1-4 layers. When applied as a promoter in a thermocatalyst for the selective catalytic reduction of NOX using NH3, 2V3WS2/Ti (WS2-5N ND) exhibited excellent NOX conversion and N2 selectivity, along with excellent durability even in the presence of SO2. This result was greater than 2V3WS2/Ti (WS2-5N) subjected to only liquid nitrogen exfoliation, proving the importance of the simultaneous action of both methods. This method is expected to be an important contribution to ongoing research on high-performance WS2-based catalysts, thereby opening up potential opportunities for a wide range of applications.

Multiple Heterointerfaces and Heterostructure Engineering in MXene@Co-P-S Hybrids Promote High-Performance Sodium-Ion Half/Full Batteries.

In this paper, heterogeneous cobalt phosphosulfide (Co4S3/Co2P) nanocrystals anchoring on few-layered MXene nanosheets (MXene@Co4S3/Co2P) were prepared by in situ growth and the subsequent high-temperature phosphorization/sulfidation processes. Thanks to the synergistic effect and the abundant phase interfaces of Co4S3, Co2P, and MXene, the electron transfer and Na+ diffusion processes were greatly accelerated. Meanwhile, the high electrical conductivity of MXene nanosheets and the heterogeneous structure of Co4S3/Co2P effectively avoided the MXene restacking and the agglomeration of phosphosulfide particles, thus mitigating volumetric expansion during charging and discharging. The results show that the MXene@Co4S3/Co2P heterostructure presents good rate capability (251.08 mAh g-1 at 1 A g-1) and excellent cycling stability (198.69 mAh g-1 after 407 cycles at 5 A g-1). Finally, the storage mechanism of Na+ in the heterostructure and the multistep phase transition reaction were determined by ex situ X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS) analyses. This study provides a new perspective on the formation of metal phosphosulfide and MXene hybrids with multiple heterointerfaces as well as demonstrates MXene@Co4S3/Co2P composites as the promising anode material in sodium-ion batteries.

Confinement synthesis of few-layer MXene-cobalt@N-doped carbon and its application for electrochemical sensing

Herein, the few-layer Ti3C2Tx nanosheets loaded zeolitic imidazolate framework-67 nanoplates (Ti3C2Tx-ZIF-67) with a unique structure has been synthesized by surfactant control method, and then is employed as the core of precursor. A thin layer of polydopamine as the shell of precursor covered Ti3C2Tx-ZIF-67 forms a micro-nano reactor, leading to the confinement carbonization process. Consequently, a novel sensing material that few-layer Ti3C2Tx nanosheets loaded Co nanoparticles coated N-doped carbon (Ti3C2Tx-Co@NC) is obtained for the non-enzymatic determination of glucose. Owing to the impressive structure, the established glucose sensor based on Ti3C2Tx-Co@NC/glassy carbon electrode exhibits 0.5–100.0 μM of linear detection range and 66.8 nM of detection limit, which tends to detect low concentration of glucose. The synergistic few-layer Ti3C2Tx nanosheets, Co nanoparticles and NC are considered through a series of control experiments. First, few-layer Ti3C2Tx nanosheets provide a good transport channel for electron transfer, resulting in the lower steric hindrance. Second, Co nanoparticles provide active centers for the electrochemical detection. Third, N-doped carbon with conductivity and hydrophilia plays the role of stabilizing material structure to prevent the fragmentation of Ti3C2Tx and the agglomeration of Co nanoparticles. Such work proposes a confined strategy to develop MXene-ZIF-67-derived nanocomposite with high-performance structure.

Nanoarchitectonics of few-layer Ni3Fe nanosheets embedded porous nitrogen-doped carbon derived from asphalt waste: An efficient electrocatalyst for oxygen evolution reaction

The design and fabrication of stable, high-performance, and affordable oxygen evolution reaction (OER) electrocatalysts is essential for performing practical water electrolysis and generating green hydrogen energy. Here, we report that 2D few layer Ni3Fe nanosheets embedded with 2D porous nitrogen doped carbon (N-NixFe@CF) from asphalt waste and then convolved and assembled into 1D hollow nanotube structures by Lewis acid molten salt etching method, which were used as electrocatalysts for OER. Benefiting from the integrate of 1D hollow nanotube structure and 2D porous nanosheets, the close contact between catalysts and support, and the increased conductivity, the resultant N-Ni3Fe@CF catalysts exhibited high catalytic activities in the OER with low overpotential at a current density of 10 mA cm−2 (114 mV), low Tafel slope (166.6 mV dec−1), and excellent electrochemical stability. This work provides a new concept for expanding the use of asphalt wastes and by-products, as well as a straightforward synthesis method for producing economical, efficient, and long-lasting alkaline OER electrocatalysts.

Strong electronic interaction in chromium-molybdenum dual incorporated few-layer cobalt sulfide nanosheets with lattice distortion for efficient bifunctional water splitting

The investigation into cost-effective and high-efficiency bifunctional electrocatalysts for electrochemical water splitting is crucial for advancing the conversion efficiency of intermittent energy systems. In this study, a novel dissolution-in situ precipitation method is introduced to synthesize few-layer CoS2 nanosheets incorporating dual cations (Cr, Mo), referred to as Cr/Mo-CoS2. The synergistic influence arising from robust dual dopant-induced coupling interactions and pronounced lattice distortions enhances the rate-determining steps of the HER and OER processes in Cr/Mo-CoS2 by optimizing the adsorption of H* and OOH* intermediates on the catalyst surface. The distinctive pinecone-like structure formed by these nanosheets provides numerous active sites and facilitates electron transfer during reactions. Consequently, the synthesized Cr/Mo-CoS2 nanosheets demonstrate superior catalytic activity, characterized by a low overpotential of 123.8 mV at 10 mA cm−2 for the hydrogen evolution reaction and 310.2 mV at 50 mA cm−2 for the oxygen evolution reaction, coupled with excellent durability in alkaline electrolytes. When utilized as bifunctional electrodes for comprehensive water splitting, Cr/Mo-CoS2 achieves a current density of 10 mA cm−2 at a cell voltage of 1.55 V. This research underscores the critical role of dual-cation doping-induced coupling interactions and significant lattice distortions in augmenting the performance of transition metal chalcogenide electrocatalysts.

Electrosynthesis of an Improbable Directly Bonded Phosphorene-Fullerene Heterodimensional Hybrid toward Boosted Photocatalytic Hydrogen Evolution.

Phosphorene and fullerene are representative two-dimensional (2D) and zero-dimensional (0D) nanomaterials respectively, constructing their heterodimensional hybrid not only complements their physiochemical properties but also extends their applications via synergistic interactions. This is however challenging because of their diversities in dimension and chemical reactivity, and theoretical studies predicted that it is improbable to directly bond C60 onto the surface of phosphorene due to their strong repulsion. Here, we develop a facile electrosynthesis method to synthesize the first phosphorene-fullerene hybrid featuring fullerene surface bonding via P-C bonds. Few-layer black phosphorus nanosheets (BPNSs) obtained from electrochemical exfoliation react with C60 2- dianion prepared by electroreduction of C60, fulfilling formation of the "improbable" phosphorene-fullerene hybrid (BPNS-s-C60). Theoretical results reveal that the energy barrier for formation of [BPNS-s-C60]2- intermediate is significantly decreased by 1.88 eV, followed by an oxidization reaction to generate neutral BPNS-s-C60 hybrid. Surface bonding of C60 molecules not only improves significantly the ambient stability of BPNSs, but also boosts dramatically the visible light and near-infrared (NIR) photocatalytic hydrogen evolution rates, reaching 1466 and 1039 μmol h-1 g-1 respectively, which are both the highest values among all reported BP-based metal-free photocatalysts.

ZIF-8 nanoparticles densely covered MXene as functionalized platform for electrochemical detection of medical small molecules

The high-performance electrochemical detection relies on sensing material with highly active structure, which requires the development of advanced synthesis technique and the study of its structure-activity mechanism. Herein, the few-layer Ti3C2Tx nanosheets densely coated zeolitic imidazole framework-8 nanoparticles (Ti3C2Tx@ZIF-8) have been successfully prepared as a unique precursor, which combines the structural advantages of two-dimensional Ti3C2Tx and porous ZIF-8 nanoparticles, leading to the vast interior spaces for loading electrocatalytic nanomaterials. For this purpose, Ti3C2Tx@Au nanoparticles-ZnO nanoparticles@N-doped carbon (Ti3C2Tx@AuNPs-ZnO@NC) has been obtained for the simultaneous electrochemical detection of pharmaceutical molecules including dopamine (DA), acetaminophen (AC), and xanthine (XA). The materials characterization and sensing analysis results of Ti3C2Tx@AuNPs-ZnO@NC reveal the structure-activity relationship of Ti3C2Tx, AuNPs and NC resulting in the high-performance behaviors, which can be summed up as stable electrochemical active sites and efficient electron transport channels. First, the abundant anchor points are offered by NC for immobilizing AuNPs, which ensure the electrochemical activity of such material. Second, the close combination of few-layer Ti3C2Tx nanosheets and NC provides an ideal channel for electron transmission along with the electrochemical reaction process. The potential application of Ti3C2Tx@AuNPs-ZnO@NC is displayed to develop the electrochemical medical sensor. The detection limits are 41 nM towards DA, 59 nM towards AC, and 67 nM towards XA. The linear ranges are 3–200 μM for DA, 15–500 μM for AC, and 8–350 μM for XA.

Utilizing supercritical fluid for efficient preparation of kaolinite nanosheets to enhance Ga(Ⅲ) adsorption

This study explores the efficient preparation of few-layered or monolayered kaolinite (K) nanosheets using supercritical gasification exfoliation technology, aiming to enhance their adsorption capacity for Ga(III). Crystal structure and morphology analysis indicated that the exfoliated K nanosheets maintained an excellent hexagonal lamellar crystal shape, with significantly reduced thickness (∼10 nm) while maintaining an unchanged lateral dimension (400 ∼ 600 nm). The exfoliation mechanism primarily relies on the considerable impact force generated by the rapid expansion of supercritical carbon dioxide (CO2) volume during fast pressure release, which facilitates exfoliation between K layers where the interlayer hydrogen bonds have been disrupted by potassium acetate. Batch adsorption experiments demonstrated a significant improvement in the removal rate of exfoliated K for Ga(III), increasing from 50.66 % to 80.47 % under the conditions of a Ga(III) concentration of 15 mg/L and an adsorbent dosage of 0.4 g/L, attributed to the exposure of numerous active sites. Kinetic and isotherm fitting results indicated a monomolecular adsorption process primarily controlled by chemical adsorption, with a maximum theoretical adsorption capacity of 32.90 mg/g for Ga(III). In multivariate mixed adsorption experiments, exfoliated K exhibited good adsorption selectivity for Ga(III), primarily through chemical adsorption of aluminum hydroxide (Al–OH) functional groups and electrostatic adsorption of silicon oxide (Si–O). Density functional theory (DFT) calculations further demonstrated that the bidentate adsorption coordination of K with Ga(III) exhibits higher stability compared to monodentate adsorption coordination, indicating that the adsorption process is mainly dominated by bidentate adsorption. Consequently, the supercritical gasification exfoliation technology, as a recyclable green process, offers efficient exfoliation of K, holding significance implications for the high-value and high-efficiency utilization of K resources, as well as for establishing a green, low-carbon, and recycling development economic system.

Reduced graphene oxide nanosheets as electron sink for MnFe2O4 nanoparticles: A synergistically boosted supercapacitance

Spinel ferrite structures have shown promise for energy storage. However, they are insulators and need a conductive substrate for better charge transfer. Here, we utilized a simple hydrothermal technique to in-situ coat a nickel foam with few-layer nanosheets of reduced graphene oxide (rGO) decorated with manganese ferrite (MnFe2O4) nanoparticles. We then studied the supercapacitance/pseudocapacitance properties of the rGO/MnFe2O4 composite. X-ray diffraction patterns, energy-dispersive X-ray maps, and X-ray photoelectron spectra of the composite were investigated to confirm its structural, elemental, and surface chemical composition, respectively. Scanning electron microscopy and transmission electron microscopy images demonstrated the decoration of rGO nanosheets with MnFe2O4 nanoparticles. In a three-electrode setup, the rGO/MnFe2O4 nanocomposite exhibits a specific capacitance per loaded material mass (2446 F/g at 1 A/g) which is higher than the sum of rGO (304 F/g) and MnFe2O4 (1084 F/g) electrodes, suggesting a synergistic effect between rGO and MnFe2O4. The energy density and power density of the rGO/MnFe2O4 electrode were also calculated 58.24 Wh/kg and 260.82 W/kg (at 1 A/g), respectively. We found that the resistance of the rGO/MnFe2O4 electrode (2.53 Ω) is much lower than the MnFe2O4 electrode (6.15 Ω), and the interfacial resistance of the rGO/MnFe2O4 electrode with electrolyte was found low, confirming the rGO role as a conductive substrate for insulating MnFe2O4 nanoparticles. We also showed that surface-related capacitance, rather than pseudocapacitance, is more dominant in the rGO/MnFe2O4 composite electrode than in the separate rGO and MnFe2O4 electrodes. We also demonstrated the practical performance of the rGO/MnFe2O4 electrode in a two-electrode setup. Finally, density functional theory calculations showed the considerable potential drop (16.5 eV) between MnFe2O4 and graphene that leads to a strong built-in electric field from graphene towards MnFe2O4. This indicates the role of graphene as a wide electron sink for MnFe2O4 nanoparticles that results in better charge distribution and storage.

Additive-Free Anode with High Stability: Nb2CTx MXene Prepared by HCl-LiF Hydrothermal Etching for Lithium-Ion Batteries.

MXenes, represented by Ti3C2Tx, have been widely studied in the electrochemical energy storage fields, including lithium-ion batteries, for their unique two-dimensional structure, tunable surface chemistry, and excellent electrical conductivity. Recently, Nb2CTx, as a new type of MXene, has attracted more and more attention due to its high theoretical specific capacity of 542 mAh g-1. However, the preparation of few-layer Nb2CTx nanosheets with high-quality remains a challenge, which limits their research and application. In this work, high-quality few-layer Nb2CTx nanosheets with a large lateral size and a high conductivity of up to 500 S cm-1 were prepared by a simple HCl-LiF hydrothermal etching method, which is 2 orders of magnitude higher than that of previously reported Nb2CTx. Furthermore, from its aqueous ink, the viscosity-tunable organic few-layer Nb2CTx ink was prepared by HCl-induced flocculation and N-methyl-2-pyrrolidone treatment. When using the organic few-layer Nb2CTx ink as an additive-free anode of lithium-ion batteries, it showed excellent cycling performance with a reversible specific capacity of 524.0 mAh g-1 after 500 cycles at 0.5 A g-1 and 444.0 mAh g-1 after 5000 cycles at 1 A g-1. For rate performance, a specific capacity of 159.8 mAh g-1 was obtained at a high current density of 5 A g-1, and an excellent capacity retention rate of about 95.65% was achieved when the current density returned to 0.5 A g-1. This work presents a simple and scalable process for the preparation of high-quality Nb2CTx and its aqueous/organic ink, which demonstrates important application potential as electrodes for electrochemical energy storage devices.

Sandwiched ReS2 nanocables with dual carbon coating for efficient K+/Na+ storage performance

In this work, the nanocables of few-layered ReS2 nanosheets sandwiched between carbon nanotubes (CNTs) and nitrogen-doped amorphous carbon (NC) coating (i.e., CNT@ReS2@NC) are synthesized as high-performance anodes of both potassium-ion batteries (PIBs) and sodium-ion batteries (SIBs). The CNT@ReS2@NC nanocables with dual carbon modifications have the several advantages for efficient K+/Na+ storage. The few-layered ReS2 nanosheets with a wide interlayer spacing of 0.64 nm contribute to accelerated reaction kinetics for fast K+/Na+ intercalation/extraction. The carbon nanotube skeleton with a hollow interior can effectively relieve the volume change and serve as a robust conductive network to boost structural stability. The NC layer provides rich defects as active sites and suppresses the shuttle effect of polysulfides produced in discharge/charge processes. Consequently, the CNT@ReS2@NC nanocables possess outstanding electrochemical performance in both PIBs and SIBs owing to the synergistic effect from the different components. A long cycling lifespan of 3500 cycles with a maintained discharge capacity of 125 mAh/g is achieved for CNT@ReS2@NC at 1 A/g in PIBs. In SIBs, it can keep a high capacity of 202 mAh/g over 3000 cycles at 5 A/g. Moreover, the CNT@ReS2@NC||Na3V2(PO4)3 full cell can exhibit remarkable cycling performance, yielding a low capacity decay rate of 0.019 % per cycle over 1000 cycles at 2C.

Fabrication of Rhenium Disulfide/Mesoporous Silica Core-Shell Nanoparticles for a pH-Responsive Drug Release and Combined Chemo-Photothermal Therapy.

A stimuli-responsive drug delivery nanocarrier with a core-shell structure combining photothermal therapy and chemotherapy for killing cancer cells was constructed in this study. The multifunctional nanocarrier ReS2@mSiO2-RhB entails an ReS2 hierarchical nanosphere coated with a fluorescent mesoporous silica shell. The three-dimensional hierarchical ReS2 nanostructure is capable of effectively absorbing near-infrared (NIR) light and converting it into heat. These ReS2 nanospheres were generated by a hydrothermal synthesis process leading to the self-assembly of few-layered ReS2 nanosheets. The mesoporous silica shell was further coated on the surface of the ReS2 nanospheres through a surfactant-templating sol-gel approach to provide accessible mesopores for drug uploading. A fluorescent dye (Rhodamine B) was covalently attached to silica precursors and incorporated during synthesis in the mesoporous silica walls toward conferring imaging capability to the nanocarrier. Doxorubicin (DOX), a known cancer drug, was used in a proof-of-concept study to assess the material's ability to function as a drug delivery carrier. While the silica pores are not capped, the drug molecule loading and release take advantage of the pH-governed electrostatic interactions between the drug and silica wall. The ReS2@mSiO2-RhB enabled a drug loading content as high as 19.83 mg/g doxorubicin. The ReS2@mSiO2-RhB-DOX nanocarrier's cumulative drug release rate at pH values that simulate physiological conditions showed significant pH responsiveness, reaching 59.8% at pH 6.8 and 98.5% and pH 5.5. The in vitro testing using HeLa cervical cancer cells proved that ReS2@mSiO2-RhB-DOX has a strong cancer eradication ability upon irradiation with an NIR laser owing to the combined drug delivery and photothermal effect. The results highlight the potential of ReS2@mSiO2-RhB nanoparticles for combined cancer therapy in the future.

Electrochemical investigation of electrophoretically deposited graphene-oxide coating on AZ31 alloy prepared using in-house synthesized few-layer graphene-oxide nanosheets

Magnesium and its alloys possess low density and superior specific strength making it a potential structural metal to be used in different engineering fields. However, its proneness to corrosion limits its applications. In this novel study, an eco-friendly graphene-oxide coating was prepared on AZ31 magnesium alloy via electrophoretic deposition to enhance its anti-corrosion properties. Scanning electron microscopy coupled with energy dispersive spectroscopy, atomic force microscopy, and scratch test were adopted to investigate surface morphology, roughness, chemical composition, and adherence of the coating. The corrosion behaviour of graphene-oxide coated alloy was studied using potentio-dynamic polarization and electrochemical impedance spectroscopy tests in 3.5 wt% NaCl and Borate Buffer solutions. The obtained results demonstrate that the coating developed on AZ31 alloy is smooth and adherent with the hardness of the as-deposited coating measuring as high as 6.0 GPa. In addition, the electrochemical corrosion behaviour studies revealed that the coating significantly increased the corrosion potential (Ecorr) of the alloy towards more noble values (−0.65 V < Ecorr < −0.35 V), with the coated alloys possessing a charge transfer resistance nearly two orders of magnitude greater than their non-coated counterparts. Consequently, the corrosion rate of the coated alloy decreased substantially, indicating that the coating exhibits exceptional corrosion resistance (0.045–0.09 mm/a in 3.5 wt% NaCl and 0.002–0.006 mm/a in Borate Buffer). These findings challenge the conventional beliefs that graphene exhibits strong cathodic behaviour towards anodic materials such as AZ31 alloy. Thus, the outcomes not only have the potential to revolutionize the advancement of graphene-oxide coatings for corrosion resistance but could also possibly expand AZ31 alloy’s applications in the aerospace and automotive sectors.

Solution Processing of Spinel Nickel Cobaltite: Exfoliation Mechanism, Dispersion Stability, and Applications.

The exfoliation of nonlayered materials to mono- or few-layers is of growing interest to realize their full potential for various applications. Nickel cobaltite (NiCo2O4), which has a spinel crystal structure, is one such nonlayered material with unique properties and has been utilized in a wide range of applications. Herein, NiCo2O4 is synthesized from NiCo2- Layered double hydroxides using a topochemical conversion technique. Subsequently, bulk NiCo2O4 is exfoliated into mono- or few-layer nickel cobaltene nanosheets using liquid-phase exfoliation in various low-boiling point solvents. An analytical centrifuge technique is also utilized to understand the solute-solvent interactions by determining their dispersion stability using parameters such as the instability index and sedimentation velocity. Among the studied solvents, water/isopropyl alcohol cosolvent is found to have better dispersion stability. In addition, density functional theory calculations are carried out to understand the exfoliation mechanism. It is found that the surface termination arising from the Co-O bond needs the least energy for exfoliation. Furthermore, the obtained nickel cobaltene nanosheets are utilized as an active material for supercapacitors without any conductive additives or binders. A solid-state symmetric supercapacitor delivers a specific capacitance of 10.2 mF cm-2 with robust stability, retaining ∼98% capacitance after 4000 cycles.

Exfoliation of Ca3Co4O9 to Two-Dimensional Single-Crystalline Misfit Calcium Cobaltates for Energy Storage Applications.

Layered materials have become indispensable in the development of two-dimensional (2D) systems, offering extensive specific surface area and exceptional electrical, electrochemical, and optical properties critical for diverse applications in energy storage, catalysis, sensing, and optoelectronics. While mono- and biatomic layered materials have demonstrated remarkable characteristics in lower dimensions, the quest for complexity in materials has opened new avenues for tailoring properties to specific requirements. Within this context, misfit-layered compounds (MLCs) stand out as promising candidates. In this study, we present a successful synthesis of few-layered misfit CaCoO2-CoO2 2D nanosheets in bulk quantities from bulk calcium cobalt oxide (CCO-B or CCO). These newly synthesized 2D exfoliated misfit nanosheets demonstrate remarkable 7-fold electrochemical energy storage properties, surpassing their parent bulk CCO, as cathode materials in aqueous Zn-ion batteries. This work addresses the longstanding challenge of exfoliating bulk MLCs to nanostructured, lower dimensional MLCs, opening doors for utilization in advanced energy storage systems and beyond.

WS2 nanosheets-based electrochemical biosensor for highly sensitive detection of tumor marker miRNA-4484

In this paper, a few-layer WS2 nanosheets-based electrochemical biosensor was fabricated for the highly sensitive detection of breast cancer tumor marker miRNA-4484. Firstly, few-layer WS2 nanosheets were prepared by shear stripping and characterized by SEM, TEM, AFM and UV spectrophotometer. After modification of few-layer WS2 nanosheets on the electrode surface, the miRNA probe was fixed on the few-layer WS2 nanosheets by polycytosine (PolyC). Then short-chain miRNA containing PolyC was used as the blocking agent to close the excess active sites on the surface of WS2 nanosheets to complete the fabrication of the sensor biosensing interface. Finally, the current changes caused by the specific binding of miRNA-4484 to the probe were analyzed by differential pulse voltammetry (DPV). The results showed that the sensor had a good linear relationship for the detection of miRNA-4484 in the concentration range of 1 aM–100 fM, and the detection limit was as low as 1.61 aM. In addition, the electrochemical sensor had excellent selectivity, stability and reproducibility. The artificial sample tests indicated that the developed biosensors have the potential for clinical application in the future.

Dual carbon modification of few-layered ReS2 nanosheets to retard polysulfide shuttling for long-cycling sodium-ion batteries

Rhenium disulfide (ReS2) is promising to work as a robust host for sodium storage, owing to the extremely weak interlayer van der Waals interactions and large interlayer spacing. However, the low electronic conductivity and huge volume expansion seriously restrict high-rate capability and cycling lifespan. In this work, few-layered ReS2 nanosheets with carbon coating (ReS2/C) grown on the hollow mesoporous carbon spheres (HMCS) are designed to form the HMCS@ReS2/C architectures that have several merits for the sodium storage, attributed to the dual carbon modification and the hollow structure. (i) HMCS provides a large interior void to relieve the volume change during discharge/charge processes and superior structural stability for long-term cycling. (ii) The large hetero-interfacial contact can enhance electron/Na+ transport in ReS2, enabling accelerated reaction kinetics. (iii) The outer carbon layer formed on ReS2 surface is capable of inhibiting dissolution of polysulfide ions and their corrosion to the copper current collector, preventing the “under-voltage failure” phenomenon. Consequently, HMCS@ReS2/C delivers superior sodium storage performance, yielding excellent high-rate capability (211 mAh g−1 at 10 A g−1), long lifespan (4000 cycles at 10 A g−1) and stable cycling stability with an extremely low capacity decay rate of 0.0096% per cycle. The high-rate cyclability surpasses the record of ReS2-based anodes reported previously. Furthermore, the fabricated Na3V2(PO4)3║HMCS@ReS2/C full cells can also exhibit outstanding cycling performance.