An ultrasensitive electrochemical/colorimetric dual-mode self-powered biosensing platform for lung cancer marker detection by multiple-signal amplification strategy

BACKGROUND

In recent years, miRNAs have emerged as potentially valuable tumor markers, and their sensitive and accurate detection is crucial for early screening and diagnosis of tumors. However, the analysis of miRNAs faces significant challenges due to their short sequence, susceptibility to degradation, high similarity, low expression level in cells, and stringent requirements for in vitro research environments. Therefore, the development of sensitive and efficient new methods for the detection of tumor markers is crucial for the early intervention of related tumors.

RESULTS

An ultrasensitive electrochemical/colorimetric dual-mode self-powered biosensor platform is established to detect microRNA-21 (miR-21) via a multi-signal amplification strategy. Gold nanoparticles (AuNPs) and VS4 nanosheets self-assembled 3D nanorods (VS4-Ns-Nrs) are prepared for constructing a superior performance enzyme biofuel cell (EBFC). The double-signal amplification strategy of Y-shaped DNA nanostructure and catalytic hairpin assembly (CHA) is adopted to further improve enhance the strength and specificity of the output signal. In addition, a capacitor is matched with EBFC to generate an instantaneous current that is amplified several times, and the output detection signal is improved once more. At the same time, electrochemical and colorimetric methods are used for dual-mode strategy to achieve the accuracy of detection. The linear range of detection is from 0.001 pg/mL to 1000 pg/mL, with a relatively low limit of detection (LOD) of 0.16 fg/mL (S/N = 3).

SIGNIFICANCE

The established method enables accurate and sensitive detection of markers in patients with lung cancer, providing technical support and data reference for precise identification. It is anticipated to offer a sensitive and practical new technology and approach for early diagnosis, clinical treatment, and drug screening of cancer and other related major diseases.

Prediction of band inversion in Janus In2XYZ (X, Y, and Z = S, Se, Te) monolayers

In this work, the electronic and spin characteristics of Janus In2X2Y and In2XYZ (X, Y, and Z = S, Se, Te) monolayers are explored. The two sides of these Janus compounds have distinct vacuum levels due to their vertical asymmetry, which causes different work functions. An emerging dipole moment alters the band alignments on both surfaces of the Janus In2X2Y structures due to electronegativity differences between various chalcogen atoms on each surface. The band structures of these monolayers with and without spin-orbit coupling (SOC) are compared. The SOC consideration opens a finite bandgap in the In2STeS, In2SSTe, In2SeTeSe, and In2SeTeTe monolayers, while demonstrating a metallic behavior without SOC. The band inversion is indicated in these monolayers using projected band structures. In addition, In2SSeTe and In2SeTeS monolayers exhibit band inversion, and In2SeTeS has the highest topological bandgap as 111 meV.

Properties of Layered TMDC Superlattices for Electrodes in Li-Ion and Mg-Ion Batteries

In this work, we present a first-principles investigation of the properties of superlattices made from transition metal dichalcogenides for use as electrodes in lithium-ion and magnesium-ion batteries. From a study of 50 pairings, we show that, in general, the volumetric expansion, intercalation voltages, and thermodynamic stability of vdW superlattice structures can be well approximated with the average value of the equivalent property for the component layers. We also found that the band gap can be reduced, improving the conductivity. Thus, we conclude that superlattice construction can be used to improve material properties through the tuning of intercalation voltages toward specific values and by increasing the stability of conversion-susceptible materials. For example, we demonstrate how pairing SnS2 with systems such as MoS2 can change it from a conversion to an intercalation material, thus opening it up for use in intercalation electrodes.

Computational Study of the Enhancement of Graphene Electrodes for Use in Li-Ion Batteries via Forming Superlattices with Transition Metal Dichalcogenides

In our study, we examined nine transition metal dichalcogenide (TMDC)-graphene superlattices as potential Li-ion intercalation electrodes. We determined their voltages, with ScS2-graphene in T- and R-phases showing the highest at around 3 V, while the others ranged from 0 to 1.5 V. Most superlattices exhibited minimal volumetric expansion (5 to 10%), similar to NMC (8%), except for SnS2-T and NiS2-T, which expanded up to nearly 20%. We evaluated their capacities using a stability metric, EIS, and found that ScS2-T, ScS2-R, and TiS2-T could be intercalated up to two Li ions per MX2 unit without decomposing to Li2S, yielding capacities of 306.77 mA h/g for both ScS2 phases and 310.84 mA h/g for TiS2-T, roughly equivalent to LiC2. MoS2-T could accept Li up to a limit of a = 15/16 in LiaMoS2Cb, corresponding to a capacity of 121.29 mA h/g (equivalent to LiC4). Examining the influence of graphene layers on MoS2-T, we observed a voltage decrease and an initial EIS decrease before effectively flat lining, which is due to charge donation to the middle graphene layer, reducing the electron concentration near the TMDC layer. As graphene layers increased, overall volume expansion decreased with Li intercalation, which is attributed to the in-plane expansion changing. Our results underscore the potential of TMDC-graphene superlattices as Li-ion intercalation electrodes, offering low volumetric expansions, high capacities, and a wide voltage range. These superlattices all show an increase in the capacity of the graphene.

Design principles for 2D transition metal dichalcogenides toward lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are regarded as a promising candidate for next-generation energy storage systems owing to their remarkable energy density, resource availability, and environmental benignity. Nevertheless, severe shuttling effect, sluggish redox kinetics, large volumetric expansion, and uncontrollable dendrite growth hamper the practical applications. To address these intractable issues, two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged expeditiously as an essential material strategy. Herein, this review emphasizes the development and application of 2D TMDs in Li-S batteries. It starts with introducing the fundamentals of Li-S batteries and common synthetic routes of TMDs, followed by summarizing the employment of pristine, hybrid, and defective TMDs in the realm of expediting sulfur chemistry and stabilizing lithium anode. Finally, the development roadmap and possible research directions of TMDs are proposed to offer guidance for the future design of high-performance Li-S batteries.

Surface Modification of Transition Metal Dichalcogenide Nanosheets for Intrinsically Self-Healing Hydrogels with Enhanced Mechanical Properties

Nanocomposites with enhanced mechanical properties and efficient self-healing characteristics can change how the artificially engineered materials' life cycle is perceived. Improved adhesion of nanomaterials with the host matrix can drastically improve the structural properties and confer the material with repeatable bonding/debonding capabilities. In this work, exfoliated 2H-WS₂ nanosheets are modified using an organic thiol to impart hydrogen bonding sites on the otherwise inert nanosheets by surface functionalization. These modified nanosheets are incorporated within the PVA hydrogel matrix and analyzed for their contribution to the composite's intrinsic self-healing and mechanical strength. The resulting hydrogel forms a highly flexible macrostructure with an impressive enhancement in mechanical properties and a very high autonomous healing efficiency of 89.92%. Interesting changes in the surface properties after functionalization show that such modification is highly suitable for water-based polymeric systems. Probing into the healing mechanism using advanced spectroscopic techniques reveals the formation of a stable cyclic structure on the surface of nanosheets, mainly responsible for the improved healing response. This work opens an avenue toward the development of self-healing nanocomposites where chemically inert nanoparticles participate in the healing network rather than just mechanically reinforcing the matrix by slender adhesion.

Transition-Metal Dichalcogenides in Electrochemical Batteries and Solar Cells

The advent of new nanomaterials has resulted in dramatic developments in the field of energy production and storage. Due to their unique structure and properties, transition metal dichalcogenides (TMDs) are the most promising from the list of materials recently introduced in the field. The amazing progress in the use TMDs for energy storage and production inspired us to review the recent research on TMD-based catalysts and electrode materials. In this report, we examine TMDs in a variety of electrochemical batteries and solar cells with special focus on MoS₂ as the most studied and used TMD material.

In-situ construction of binder-free MnO2/MnSe heterostructure membrane for high-performance energy storage in pseudocapacitors

Manganese (Mn)-based oxides are considered suitable positive electrode materials for supercapacitors (SCs). However, their cycle stability and specific capacitance are significantly hindered by key restrictions such as structural instability and low conductivity. Herein, we demonstrated a novel nanorod (NR)-shaped heterostructured manganese dioxide/manganese selenide membrane (MnO2/MnSe) on carbon cloth (CC) (denoted as MnO2/MnSe-NR@CC) with a high aspect ratio by a straightforward and facile hydrothermal process. Experiments have demonstrated that doping selenium atoms to oxygen sites reduce electronegativity, increasing the intrinsic electronic conductivity of MnO2, decreasing electrostatic interactions with electrolyte ions, and thus boosting the reaction kinetics. Further, the selenium doping results in an amorphous surface with extensive oxygen defects, which contributed to the emergence of additional charge storage sites with pseudocapacitive characteristics. As expected, novel heterostructured MnO2/MnSe-NR@CC as an electrode for SC exhibits a high capacitance of 740.63 F/g at a current density of 1.5 A/g, with excellent cycling performance (93% capacitance retention after 5000 cycles). The MnO2/MnSe-NR@CC exhibited outstanding charge storage capability, dominating capacitive charge storage (84.6% capacitive at 6 mV/s). To examine the practical applications of MnO2/MnSe-NR@CC-ASC as a positive electrode, MnO2/MnSe-NR@CC//AC device was fabricated. The MnO2/MnSe-NR@CC//AC-ASC device performed exceptionally well, with a maximum capacitance of 166.66 F/g at 2 A/g, with a capacitance retention of 94%, after 500 GCD cycles. Additionally, it delivers an energy density of 75.06 Wh/kg at a power density of 1805.1 W/kg and maintains 55.044 Wh/kg at a maximum power density of 18,159 W/kg. This research sheds fresh information on the anionic doping method and has the potential to be applied to the synthesis of positive electrode materials for energy storage applications.

Wet-chemical assisted synthesis of MnSe/ZnO nanostructures as low-resistance robust novel cathode material for advanced hybrid supercapacitors

We proposed a novel MnSe–ZnO-based binary nanocomposite synthesized via a wet-chemical assisted method which deliver high power and energy densities, suppressing previous reports on MnSe and ZnO with decent cycling durability with good rate performance.

Antibacterial Pathways in Transition Metal-Based Nanocomposites: A Mechanistic Overview

Across the planet, outbreaks of bacterial illnesses pose major health risks and raise concerns. Photodynamic, photothermal, and metal ion release effects of transition metal-based nanocomposites (TMNs) were recently shown to be highly effective in reducing bacterial resistance and upsurges in outbreaks. Surface plasmonic resonance, photonics, crystal structures, and optical properties of TMNs have been used to regulate metal ion release, produce oxidative stress, and generate heat for bactericidal applications. The superior properties of TMNs provide a chance to investigate and improve their antimicrobial actions, perhaps leading to therapeutic interventions. In this review, we discuss three alternative antibacterial strategies based on TMNs of photodynamic therapy, photothermal therapy, and metal ion release and their mechanistic actions. The scientific community has made significant efforts to address the safety, effectiveness, toxicity, and biocompatibility of these metallic nanostructures; significant achievements and trends have been highlighted in this review. The combination of therapies together has borne significant results to counter antimicrobial resistance (4-log reduction). These three antimicrobial pathways are separated into subcategories based on recent successes, highlighting potential needs and challenges in medical, environmental, and allied industries.

Electronic Band Gap Tuning and Calculations of Mechanical Strength and Deformation Potential by Applying Uniaxial Strain on MX2 (M = Cr, Mo, W and X = S, Se) Monolayers and Nanoribbons

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are new crystalline materials with exotic electronic, mechanical, and optical properties. Due to their inherent exceptional mechanical strength, these 2D materials provide us the best platform for strain engineering. In this study, we have performed first-principles calculations to study the effect of uniaxial strains on the electronic, magnetic, and mechanical properties of transition-metal dichalcogenides (TMDs) MX2 (where M = Cr, Mo, W and X = S, Se), monolayers (2D), and armchair and zigzag nanoribbons (1D). For the mechanical strength, we determined the tensile strength (σ) and Young's modulus (Y) and observed that σ and Y are higher in monolayers (most in WS2ML) as compared to nanoribbons where monolayers resist tension up to 25-28% strain while nanoribbons (armchair and zigzag) can be only up to 5-10%. Deformation potential (Δ p ) in the linear regime near the equilibrium position(ϵ < 2%) has also been calculated, and its effect on monolayers is observed less as compared to nanoribbons. In addition, unstrained nonmagnetic monolayers are direct band gap semiconductors (D) which changed to indirect band gap semiconductors (I) with the application of strain. Ferromagnetic states of metallic zigzag nanoribbons (including up spin channel of 7-CrS2NR and 7-CrSe2NR) are greatly affected by strain and show half-metal-like behavior in different strain range. The magnetic moment (μ) that is predominantly observed in zigzag nanoribbons is 2 times higher than that of other nanoribbons. This magnetism in nanoribbons is mostly caused by transition-metal atoms (M = Cr, Mo, W). Thus, our study suggests that strain engineering is the best approach to modify or control the structural, electronic, magnetic, and mechanical properties of the TMD monolayer and nanoribbons which, therefore, open their potential applications in spintronics, photovoltaic cells, and tunneling field-effect transistors.

Two-dimensional MXenes: recent emerging applications

MXenes, are a rapidly growing family of two-dimensional materials exhibiting outstanding electronic, optical, mechanical, and thermal properties with versatile transition metal and surface chemistries. A wide range of transition metals and surface termination groups facilitate the properties of MXenes to be easily tuneable. Due to the physically strong and environmentally stable nature of MXenes, they have already had a strong presence in different fields, for instance energy storage, electrocatalysis, water purification, and chemical sensing. Some of the newly discovered applications of MXenes showed very promising results, however, they have not been covered in any review article. Therefore, in this review we comprehensively review the recent advancements of MXenes in various potential fields including energy conversion and storage, wearable flexible electronic devices, chemical detection, and biomedical engineering. We have also presented some of the most exciting prospects by combining MXenes with other materials and forming mixed dimensional high performance heterostructures based novel electronic devices.

Molecular dynamics study of Cr doping on the crystal structure and surficial/interfacial properties of 2H-MoS2

Molecular doping has proved to be an efficient technique to improve the properties of pristine materials. A better understanding of it is quite necessary. For the first time, the force field parameters of the transition metal chromium (Cr) doped in 2H-MoS₂ in molecular dynamics (MD) were developed. Compared with the DFT calculation results, the error in the stable-state lattice parameters is less than 1%. The optimized force field parameters were used for the MD simulation of different amounts of Cr substitution doping in 2H-MoS₂. This study found that the Cr doping at different sites will have a significant impact on the stability of the bulk 2H-MoS₂. With increasing doping amount, the water contact angle increases from 69.2° ± 2° to 78.5° ± 0.4°, and the hydrophobic performance is obviously improved. Finally, we also found that the adsorption energy of Cr-MoS₂ decreased with increasing Cr doping content, indicating that bulk MoS₂ is easier to separate to form single- or fewer-layer 2H-MoS₂ in the case of higher doping content. Comparison between the simulated adsorption energies of typical solvents on the 2H-MoS₂ surface shows that methanol (CH₃OH) and water (H₂O) can separate bulk 2H-MoS₂, which matched with the experimental results. By using high-precision force field parameters, molecular dynamics were performed to study the surface/interface characteristics of Cr-doped 2H-MoS₂, and provided an effective and detailed description for future experimental design.

Impact of the number of surface-attached tungsten diselenide layers on cadmium sulfide nanorods on the charge transfer and photocatalytic hydrogen evolution rate

The selection of layered number and time-course destruction of layers may affect the charge transfer between 2D-to-1D heterostructure, making it possible to improve the efficiency of solar-to-hydrogen evolution. Herein, we demonstrate a simple, low-cost systematic protocol of 2D-WSe₂ nanolayer numbers ranging from 7 to 60 aiding the ultrasonication time-course. The resultant nanolayers were assembled on the surface of 1D-CdS nanorods, which demonstrated an improved surface shuttling property. Consequently, a drastic improvement in photocatalytic solar-driven hydrogen evolution was observed (103.5 mmol h^-1 g^-1) with seven-layered WSe₂ (few-layered WSe₂) attached on CdS nanorods surface. This enhanced photocatalytic performance is attributed to the selection of layers on CdS surface that expose abundant active sites; along with suitable energy levels, this can facilitate increased charge transfer leading to feasible photocatalytic reactions. Significantly, the present study proposes an efficient and sustainable process to produce hydrogen and demonstrates the potential of numbered WSe₂ nanosheets as a co-catalyst material.

Emergence of Ni-Based Chalcogenides (S and Se) for Clean Energy Conversion and Storage

Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materials for energy conversion and storage systems. Interest in these materials is due to their good electrochemical stability, eco-friendly nature, and low cost. The present review compiles recent progress in the area of nickel-(S and Se)-based materials by providing a comprehensive summary of their structural and chemical features and performance. Improving properties of the materials, such as electrical conductivity and surface characteristics (surface area and morphology), through strategies like nano-structuring and hybridization, are systematically discussed. The interaction of the materials with electrolytes, other electro-active materials, and inactive components are analyzed to understand their effects on the performance of energy conversion and storage devices. Finally, outstanding challenges and possible solutions are briefly presented with some perspectives toward the future development of these materials for energy-oriented devices with high performance.

Designing Nanostructured Metal Chalcogenides as Cathode Materials for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMBs) are regarded as promising candidates for beyond-lithium-ion batteries owing to their high energy density. Moreover, as Mg metal is earth-abundant and has low propensity for dendritic growth, RMBs have the advantages of being more affordable and safer than the currently used lithium-ion batteries. However, the commercial viability of RMBs has been negatively impacted by slow diffusion kinetics in most cathode materials due to the high charge density and strongly polarizing nature of the Mg²⁺ ion. Nanostructuring of potential cathode materials such as metal chalcogenides offers an effective means of addressing these challenges by providing larger surface area and shorter migration routes. In this article, a review of recent research on the design of metal chalcogenide nanostructures for RMBs' cathode materials is provided. The different types and structures of metal chalcogenide cathodes are discussed, and the synthetic strategies through which nanostructuring of these materials can be achieved are described. An organized summary of their electrochemical performance is also presented, along with an analysis of the current challenges and future directions. Although particular focus is placed on RMBs, many of the nanostructuring concepts that are discussed here can be carried forward to other next-generation energy storage systems.

An overview of the current status and prospects of cathode materials based on transition metal sulfides for magnesium-ion batteries

TMSs as cathode materials used in MIBs.

Two-dimensional fence-like Co-doped NiSe2/C nanosheets as an anode for half/full sodium-ion batteries

Two-dimensional fence-like Co-NiSe₂/C nanosheets are fabricated by a facile solvothermal method and followed a selenization strategy. It displays excellent long-term cycle life, rate capability and full cell performance when used as anode for SIBs.

Transition Metal Dichalcogenides for the Application of Pollution Reduction: A Review

The material characteristics and properties of transition metal dichalcogenide (TMDCs) have gained research interest in various fields, such as electronics, catalytic, and energy storage. In particular, many researchers have been focusing on the applications of TMDCs in dealing with environmental pollution. TMDCs provide a unique opportunity to develop higher-value applications related to environmental matters. This work highlights the applications of TMDCs contributing to pollution reduction in (i) gas sensing technology, (ii) gas adsorption and removal, (iii) wastewater treatment, (iv) fuel cleaning, and (v) carbon dioxide valorization and conversion. Overall, the applications of TMDCs have successfully demonstrated the advantages of contributing to environmental conversation due to their special properties. The challenges and bottlenecks of implementing TMDCs in the actual industry are also highlighted. More efforts need to be devoted to overcoming the hurdles to maximize the potential of TMDCs implementation in the industry.

TMDs beyond MoS2 for Electrochemical Energy Storage

Atomically thin sheets of two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted interest as high capacity electrode materials for electrochemical energy storage devices owing to their unique properties (high surface area, high strength and modulus, faster ion diffusion, and so on), which arise from their layered morphology and diversified chemistry. Nevertheless, low electronic conductivity, poor cycling stability, large structural changes during metal-ion insertion/extraction along with high cost of manufacture are challenges that require further research in order for TMDs to find use in commercial batteries and supercapacitors. Here, a systematic review of cutting-edge research focused on TMD materials beyond the widely studied molybdenum disulfide or MoS₂ electrode is reported. Accordingly, a critical overview of the recent progress concerning synthesis methods, physicochemical and electrochemical properties is given. Trends and opportunities that may contribute to state-of-the-art research are also discussed.

Recent Advances of Two-Dimensional Nanomaterials for Electrochemical Capacitors

Two-dimensional (2D) nanomaterials have drawn a wide range of research interests because of their unique ultrathin layered structures and attractive properties. In particular, the electrochemical properties and great variety of 2D nanomaterials make them highly attractive candidates for electrochemical capacitors, such as supercapacitors, lithium-ion capacitors, and sodium-ion capacitors. Herein, a comprehensive review of recent progress towards the application of 2D nanomaterials for electrochemical capacitors is provided. Several typical types of 2D nanomaterials are first briefly introduced, followed by detailed descriptions of their electrochemical capacitor applications. Finally, research perspectives and future research directions of these interesting areas are also provided.

Depositing reduced graphene oxide onto tungsten disulfide nanosheets via microwave irradiation: confirmation of four-electron transfer-assisted oxygen reduction and methanol oxidation reaction

Core–shell structured rGO@WS₂ nanostructures exhibited four electron transfer towards the ORR and remarkable methanol oxidation reaction.

Reduced Binding Energy and Layer-Dependent Exciton Dynamics in Monolayer and Multilayer WS2

The exciton dynamics in WS₂ from monolayer to four-layer was investigated by using fluorescence lifetime imaging measurement (FLIM). The transition process of negatively charged trions is measured and detected using a fluorescence detection method. Compared with neutral excitons, negatively charged trions have a longer fluorescence lifetime. Further exploration illustrated that the fluorescence lifetime of both neutral excitons and trions get longer when the thickness increased. When WS₂ was added from monolayer to four-layer, lifetimes of direct transition excitons and trions tended to increase over 10 and 2.5 times, separately, whereas the lifetime of indirect transition excitons tended to be reduced by nearly 2.5 times. This layer-dependent signature is ascribed to the reduced binding energy in thicker WS₂ at room temperature, which is verified by density theory functional calculation. Although the direct transition exciton dominates the whole fluorescence decay process, it is influenced by trions and dark excitons. Based on the FLIM results, we proposed four main exciton transition channels during the fluorescence luminescence process. Such layer-dependent transition channel conception helps to control the fluorescence lifetime, which determines the efficiency of the carriers' separation.

(Co, Mn)-Doped NiSe2-diethylenetriamine (dien) nanosheets and (Co, Mn, Sn)-doped NiSe2 nanowires for high performance supercapacitors: compositional/morphological evolution and (Co, Mn)-induced electron transfer

A series of MSe2-dien (M = metal(ii) ion and dien = diethylenetriamine) were grown on Ni foam (NF) based on Co(ii)/Mn(ii) salts with different molar ratios. It was found that the Co-free sample exhibited hollow tubes built by numerous interconnected nanowires, whereas nanosheets were observed in the Co-involved samples. The formation of nanosheets is associated with Co(ii), which is due to the fact that Co(ii) promotes the metal selenide nanosheet to grow along its (011[combining macron]) facet (thickness direction). Furthermore, the formation and compositional/morphological evolution of the samples were investigated. Among them, (Co, Mn)-NiSe2-dien/NF (2 : 1-Co/Mn sample) showed the largest specific capacity of 288.6 mA h g-1 at 1 A g-1 with a retention of 69% at 10 A g-1 (198.6 mA h g-1), which is associated with its ultrathin nanosheet arrays and the co-doping of (Co, Mn) into NiSe2-dien, leading to the redistribution of electron densities around the Ni and Se centers. XPS and density functional theory (DFT) calculations proved the electron transfer from NiSe2-dien to the adsorbed OH- ions from the electrolyte solution, which can facilitate the redox reaction between active sites and electrolyte ions to enhance the electrochemical performance. A hybrid supercapacitor, (Co, Mn)-NiSe2-dien/NF//activated carbon, was fabricated, which displayed an energy density of 50.9 W h kg-1 at a power density of 447.3 W kg-1 and good cycling stability with 84% capacity retention after 10 000 charge-discharge cycles. Furthermore, (Co, Mn)-doped NiSe2-dien nanosheets could be transformed into (Co, Mn, Sn)-doped NiSe2 nanowire arrays after immersion in SnCl2 alcoholic solution due to cation exchange and the Kirkendall effect, and the obtained sample exhibited a decent areal capacity of 0.267 mA h cm-2 at 5 mA cm-2.

Research advances in the detection of miRNA

MicroRNAs (miRNAs) are a family of endogenous, small (approximately 22 nucleotides in length), noncoding, functional RNAs. With the development of molecular biology, the research of miRNA biological function has attracted significant interest, as abnormal miRNA expression is identified to contribute to serious human diseases such as cancers. Traditional methods for miRNA detection do not meet current demands. In particular, nanomaterial-based methods, nucleic acid amplification-based methods such as rolling circle amplification (RCA), loop-mediated isothermal amplification (LAMP), strand-displacement amplification (SDA) and some enzyme-free amplifications have been employed widely for the highly sensitive detection of miRNA. MiRNA functional research and clinical diagnostics have been accelerated by these new techniques. Herein, we summarize and discuss the recent progress in the development of miRNA detection methods and new applications. This review will provide guidelines for the development of follow-up miRNA detection methods with high sensitivity and specificity, and applicability to disease diagnosis and therapy.

Nanoarchitecture Frameworks for Electrochemical miRNA Detection

With revolutionary advances in next-generation sequencing, the human transcriptome has been comprehensively interrogated. These discoveries have highlighted the emerging functional and regulatory roles of a large fraction of RNAs suggesting the potential they might hold as stable and minimally invasive disease biomarkers. Although a plethora of molecular-biology- and biosensor-based RNA-detection strategies have been developed, clinical application of most of these is yet to be realized. Multifunctional nanomaterials coupled with sensitive and robust electrochemical readouts may prove useful in these applications. Here, we summarize the major contributions of engineered nanomaterials-based electrochemical biosensing strategies for the analysis of miRNAs. With special emphasis on nanostructure-based detection, this review also chronicles the needs and challenges of miRNA detection and provides a future perspective on the presented strategies.

Engineering PPy decorated MnCo2O4 urchins for quasi-solid-state hybrid capacitors

In this work, three dimensional PPy decorated MnCo₂O₄ urchins on Ni foam are fabricated via a hydrothermal strategy and an electro-polymerization process.

Ultrasound-assisted synthesis of two-dimensional layered ytterbium substituted molybdenum diselenide nanosheets with excellent electrocatalytic activity for the electrochemical detection of diphenylamine anti-scald agent in fruit extract

Metal chalcogenides with large active sites have been received great attention as an excellent catalyst due to their hierarchical structural properties. Here, we have demonstrated the synthesis of ytterbium-doped molybdenum selenide (YbMoSe₂) in the form of two-dimensional nanosheets by using a simple ultrasonic method. The formation of the crystal phase of prepared YbMoSe₂ nanosheets was studied by using the selective characterization techniques. The reported HRTEM confirmed that the introduction of heterogeneous spin of Yb with MoSe₂ creates the lattice distortion. Thus, the active sites can be increased by creating the lattice distortion on the basal plane of the metal chalcogenides nanosheets. The band gap study was carried out by using UV-visible spectrometer and demonstrated the decreasing band gap of MoSe₂ from 1.30 eV to 1.15 eV due to the Yb substitution/doping. The increasing active sites with decreasing band gap facilitate an excellent electronic conductivity and electrochemical activity. Furthermore, the electrocatalytic activity of YbMoSe₂ modified glassy carbon electrode (YbMoSe₂/GCE) toward the sensing of diphenylamine (DPA) anti-scald agent. As expected, YbMoSe₂/GCE showed a high level of electrochemical activity with a low limit of detection (0.004 µM) and excellent sensitivity (11.4 µA µM^-1 cm^-2) towards the detection of DPA. In addition, the superior selectivity, stability, and reproducibility of YbMoSe₂/GCE also were recorded. The beneficial electrochemical activity of YbMoSe₂/GCE offered the more advantages to detection of DPA in the food sample also.

Harnessing the unique properties of 2D materials for advanced lithium-sulfur batteries

In the past decade, lithium-sulfur batteries have attracted tremendous attention owing to their high theoretical energy densities. The electrochemical performances of lithium-sulfur batteries are strongly dependent on the electrode materials. Among all the electrode material candidates, the application of 2D materials in lithium-sulfur batteries including a sulfur cathode, a lithium anode, a separator and/or an electrolyte has gained great success in enhancing their electrochemical performance by overcoming their intrinsic obstacles. Thus, it is necessary to summarize the relationships between the unique features of 2D materials and the electrochemical performances of lithium-sulfur batteries, guiding the development of next-generation lithium-sulfur batteries. In this review, we focus on recent advances in harnessing the unique properties of 2D materials, including their high surface area, 2D feature, high mechanical strength, plentiful active sites and functional groups to improve the electrochemical properties of sulfur cathodes, lithium anodes, electrolytes and/or separators, respectively. Finally, we propose possible directions and strategies for harnessing various properties of 2D materials to promote the development and applications of lithium-sulfur batteries.

Applications of 2D MXenes in energy conversion and storage systems

This article provides a comprehensive review of MXene materials and their energy-related applications.

Hollow Ni-CoSe2 Embedded in Nitrogen-Doped Carbon Nanocomposites Derived from Metal-Organic Frameworks for High-Rate Anodes

Developing high-rate anode materials with large capacity for lithium ion batteries (LIBs) is quite necessary for the booming electric vehicles industry. The utilization of stable and conductive hollow structures for electrode composite materials could make the desired performances possible in the future. Thus, in this study, a hollow structured Ni-CoSe₂ embedded in N-doped amorphous carbon nanocomposite (Ni-CoSe₂@NC) has been successfully synthesized with metal-organic frameworks (MOFs) as precursors. Such strategy integrates both the merits of the multicomponents and the hollow structure; the latter could facilitate both mass and charge transport, and the former (the N-doped carbon) could not only offer plenty of surface defects, improving the surface capacitive contributions, but also stabilize the electrode structure during the charge/discharge processes. As a result, the metal selenide composite delivers outstanding high-rate properties with good stability as the anode for LIBs. The structure and components design could also be extended to other anode composites in the future.

Microfluidic-spinning construction of black-phosphorus-hybrid microfibres for non-woven fabrics toward a high energy density flexible supercapacitor

Flexible supercapacitors have recently attracted intense interest. However, achieving high energy density via practical materials and synthetic techniques is a major challenge. Here, we develop a hetero-structured material made of black phosphorous that is chemically bridged with carbon nanotubes. Using a microfluidic-spinning technique, the hybrid black phosphorous–carbon nanotubes are further assembled into non-woven fibre fabrics that deliver high performance as supercapacitor electrodes. The flexible supercapacitor exhibits high energy density (96.5 mW h cm⁻³), large volumetric capacitance (308.7 F cm⁻³), long cycle stability and durability upon deformation. The key to performance lies in the open two-dimensional structure of the black phosphorous/carbon nanotubes, plentiful channels (pores <1 nm), enhanced conduction, and mechanical stability as well as fast ion transport and ion flooding. Benefiting from this design, high-energy flexible supercapacitors can power various electronics (e.g., light emitting diodes, smart watches and displays). Such designs may guide the development of next-generation wearable electronics.

Supercapacitors that exhibit flexibility and deformability are attractive for wearable devices; however achieving high energy density remains challenging. Here the authors report a non-woven fabric based on black phosphorus and carbon nanotubes for use in a supercapacitor with notable performance.

Properties, Preparation and Applications of Low Dimensional Transition Metal Dichalcogenides

Low-dimensional layered transition metal dichalcogenides (TMDs) have recently emerged as an important fundamental research material because of their unique structural, physical and chemical properties. These novel properties make these TMDs a suitable candidate in numerous potential applications. In this review, we briefly summarize the properties of low-dimensional TMDs, and then focus on the various methods used in their preparation. The use of TMDs in electronic devices, optoelectronic devices, electrocatalysts, biosystems, and hydrogen storage is also explored. The cutting-edge future development probabilities of these materials and numerous research challenges are also outlined in this review.

Three-dimensional flower-like MoS2-CoSe2 heterostructure for high performance superccapacitors

A novel three-dimensional (3D) flower-like MoS₂-CoSe₂ heterostructure has been designed and synthesized by a facile two-step hydrothermal process as the electrode materials for supercapacitors. The MoS₂-CoSe₂ heterostructure is demonstrated to deliver a high specific capacitance (2577 F g^-1 at 1 A g^-1) and remarkable rate capability (896 F g^-1 at 20 A g^-1). Besides, the MoS₂-CoSe₂ electrode also exhibits excellent cycling stability of 91.03% capacitance retention after 5000 cycles even at a relatively high current density of 20 A g^-1. A two-electrode configuration symmetric supercapacitor based MoS₂-CoSe₂ heterostructure delivers a maximum energy density of 60.5 W h kg^-1 at a power density of 800 W kg^-1 and the energy density remains at 35.6 W h kg^-1 at a power density of 8000 W kg^-1. Excellent cycling stability is also achieved with 83.62% retention after 2000 charge-discharge cycles, revealing its potential and viability for practical applications. The outstanding electrochemical performances of the fabricated electrode stem from the unique structure characteristic of the flower-like MoS₂-CoSe₂ heterostructure. The high-quality heterointerface facilitates electron conduction while the porosity not only allows fast ion transport but provides abundant active sites for Faradic reaction and the buffer for volume variety in repeat charge-discharge process. The design strategy offers a new idea for fabricating high-performance supercapacitor electrode materials.

Lithium ion storage ability, supercapacitor electrode performance, and photocatalytic performance of tungsten disulfide nanosheets

Few layered WS₂ nanosheets for energy and environmental applications.

Hollow shell-in-shell Ni3S4@Co9S8 tubes derived from core–shell Ni-MOF-74@Co-MOF-74 as efficient faradaic electrodes

Unique shell-in-shell hierarchical structures fabricated through transition from core–shell MOFs would have great potential for hybrid supercapacitor applications.

Phosphine-free synthesis and shape evolution of MoSe2 nanoflowers for electrocatalytic hydrogen evolution reactions

Free-standing colloidal MoSe₂ nanoflowers were synthesized by a phosphine-free solution-processing approach, which showed good electrocatalytic activities.

HMTA-assisted formation of hierarchical Co-based materials built by low-dimensional substructures as water oxidation electrocatalysts

We report a 3D Co-based micro-flower constructed from 2D nanosheets, which exhibits excellent OER performance.

Hierarchical MoO3/SnS2 core–shell nanowires with enhanced electrochemical performance for lithium-ion batteries

The formation of hierarchical MoO₃/SnS₂ core–shell nanowires can effectively suppress the rapid dissociation of SnS₂ nanosheets via interfacial interactions, which is responsible for the improved electrochemical performance.

Recent advances in signal amplification strategy based on oligonucleotide and nanomaterials for microRNA detection-a review

MicroRNAs (MiRNAs) play multiple crucial regulating roles in cell which can regulate one third of protein-coding genes. MiRNAs participate in the developmental and physiological processes of human body, while their aberrant adjustment will be more likely to trigger diseases such as cancers, kidney disease, central nervous system diseases, cardiovascular diseases, diabetes, viral infections and so on. What's worse, for the detection of miRNAs, their small size, high sequence similarity, low abundance and difficult extraction from cells impose great challenges in the analysis. Hence, it's necessary to fabricate accurate and sensitive biosensing platform for miRNAs detection. Up to now, researchers have developed many signal-amplification strategies for miRNAs detection, including hybridization chain reaction, nuclease amplification, rolling circle amplification, catalyzed hairpin assembly amplification and nanomaterials based amplification. These methods are typical, feasible and frequently used. In this review, we retrospect recent advances in signal amplification strategies for detecting miRNAs and point out the pros and cons of them. Furthermore, further prospects and promising developments of the signal-amplification strategies for detecting miRNAs are proposed.

One-Pot Hydrothermal Synthesis of Hexagonal WO3 Nanorods/Graphene Composites as High-Performance Electrodes for Supercapacitors

Tungsten oxide (WO₃ ) as an electrode material for supercapacitors has always suffered from low capacitance and poor rate capability. In this work, a series of WO₃ nanorods/graphene composites with different weight ratios of tungsten oxide nanorods (WO₃ NRs) and reduced graphene oxide (rGO) are synthesized successfully through a facile one-pot electrostatic adsorptive hydrothermal method. In these composites, rGO enhances the conductivity, transporting electrons and protons to the WO₃ NRs. In addition, rGO can reinforce the structure of the WO₃ NRs during frequently occurring redox reactions. At a graphene weight ratio of 1 wt %, the specific capacitance of the WO₃ NRs/rGO composite is 343 F g^-1 at a current density of 0.2 A g^-1 . Compared with pure WO₃ as electrodes, the WO₃ NRs/rGO composite shows excellent specific capacity, and superior rate performance and cycling stability owing to the combined action of the double layer and pseudocapacitor. This study provides a new convenient approach to promote the electrochemical performance of tungsten oxide.