Recent advances in transition-metal dichalcogenides based electrochemical biosensors: A review

Recent advances in catalytic hairpin assembly signal amplification-based sensing strategies for microRNA detection

Accumulative evidences have indicated that abnormal expression of microRNAs (miRNAs) is closely associated with many health disorders, making them be regarded as potentialbiomarkers for early clinical diagnosis. Therefore, it is extremely necessary to develop a highly sensitive, specific and reliable approach for miRNA analysis. Catalytic hairpin assembly (CHA) signal amplification is an enzyme-free toehold-mediated strand displacement method, exhibiting significant potential in improving the sensitivity of miRNA detection strategies. In this review, we first describe the potential of miRNAs as disease biomarkers and therapeutics, and summarize the latest advances in CHA signal amplification-based sensing strategies for miRNA monitoring. We describe the characteristics and mechanism of CHA signal amplification and classify the CHA-based miRNA sensing strategies into several categories based on the "signal conversion substance", including fluorophores, enzymes, nanomaterials, and nucleotide sequences. Sensing performance, limit of detection, merits and disadvantages of these miRNA sensing strategies are discussed. Moreover, the current challenges and prospects are also presented.

Interconnected MoS2 on 2D Graphdiyne for Reversible Sodium Storage

In this study, graphdiyne (GDY) was first reported as a substrate material for sodium-ion batteries (SIBs). The creative hybridization of GDY and molybdenum disulfide (MoS₂) endows the composite with unique heterostructural and morphological advantages that boost the charge transport rate and enhance the battery discharge properties. Electrochemical results indicated that the MoS₂@GDY anode displays a considerable discharge capacity of up to 328 mAh g^-1 at 1000 mA g^-1. A capacity retention of 93% even at testing current back to 200 mA g^-1 suggests superior rate characteristics. An outstanding stable cyclic performance of 217 mAh g^-1 is obtained at a high testing density. The attractive results not only demonstrate that GDY could be used not only as an effective conductive substrate to prevent the host material from agglomerating in the electrochemical process but also provide a novel design for fabricating efficient electrode materials for future energy-storage systems.

A sensitive electrochemical immunosensing interface for label-free detection of aflatoxin B1 by attachment of nanobody to MWCNTs-COOH@black phosphorene

A label-free electrochemical immunosensor has advantages of real-time and rapid detection, but it is weak in detection of small molecular toxins such as aflatoxin B₁ (AFB₁). The greatest obstacle to achieving this is that small molecules bound to a common immunosensing interface cannot interfere with electron transfer effectively and the detection signal is so weak. Therefore, a sensitive electrochemical immunosensing interface for small molecules is urgently needed. Here, we employed functionalized black phosphorene (BP) as electrode modification materials and anti-AFB₁ nanobody (Nb) as a biorecognition element to construct a very sensitive immunosensing interface towards small molecular AFB₁. The BP functionalized by carboxylic multi-walled carbon nanotubes (MWCNTs-COOH) via P-C bonding behaved with a satisfactory stability and good catalytic performance for the ferricyanide/ferrocyanide probe, while the small-sized Nb showed good compatibility with the functionalized BP and also had less influence on electron transfer than monoclonal antibody (mAb). Expectedly, the as-prepared immunosensing interface was very sensitive to AFB₁ detection by differential pulse voltammetry (DPV) in a redox probe system. Under optimized conditions, a linear range from 1.0 pM to 5.0 nM and an ultralow detection limit of 0.27 pM were obtained. Additionally, the fabricated immunosensor exhibited satisfactory stability, specificity, and reproducibility. The strategy proposed here provides a more reliable reference for label-free sensing of small molecules in food samples.

Aptamer Embedded Arch-Cruciform DNA Assemblies on 2-D VS2 Scaffolds for Sensitive Detection of Breast Cancer Cells

Arch-cruciform DNA are self-assembled on AuNPs/VS₂ scaffold as a highly sensitive and selective electrochemical biosensor for michigan cancer foundation-7 (MCF-7) breast cancer cells. In the construction, arch DNA is formed using two single-strand DNA sequences embedded with the aptamer for MCF-7 cells. In the absence of MCF-7 cells, a cruciform DNA labeled with three terminal biotin is bound to the top of arch DNA, which further combines with streptavidin-labeled horseradish peroxidase (HRP) to catalyze the hydroquinone-H₂O₂ reaction on the electrode surface. The presence of MCF-7 cells can release the cruciform DNA and reduce the amount of immobilized HRP, thus effectively inhibiting enzyme-mediated electrocatalysis. The electrochemical response of the sensor is negatively correlated with the concentration of MCF-7 cells, with a linear range of 10~1 × 10⁵ cells/mL, and a limit of detection as low as 5 cells/mL (S/N = 3). Through two-dimensional materials and enzyme-based dual signal amplification, this biosensor may pave new ways for the highly sensitive detection of tumor cells in real samples.

A Low Excitation Working Frequency Capacitively Coupled Contactless Conductivity Detection (C4D) Sensor for Microfluidic Devices

In this work, a new capacitively coupled contactless conductivity detection (C⁴D) sensor for microfluidic devices is developed. By introducing an LC circuit, the working frequency of the new C⁴D sensor can be lowered by the adjustments of the inductor and the capacitance of the LC circuit. The limits of detection (LODs) of the new C⁴D sensor for conductivity/ion concentration measurement can be improved. Conductivity measurement experiments with KCl solutions were carried out in microfluidic devices (500 µm × 50 µm). The experimental results indicate that the developed C⁴D sensor can realize the conductivity measurement with low working frequency (less than 50 kHz). The LOD of the C⁴D sensor for conductivity measurement is estimated to be 2.2 µS/cm. Furthermore, to show the effectiveness of the new C⁴D sensor for the concentration measurement of other ions (solutions), SO₄²⁻ and Li⁺ ion concentration measurement experiments were also carried out at a working frequency of 29.70 kHz. The experimental results show that at low concentrations, the input-output characteristics of the C⁴D sensor for SO₄²⁻ and Li⁺ ion concentration measurement show good linearity with the LODs estimated to be 8.2 µM and 19.0 µM, respectively.

Carbon nanomaterials for cardiovascular theranostics: Promises and challenges

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Heart attack and stroke cause irreversible tissue damage. The currently available treatment options are limited to "damage-control" rather than tissue repair. The recent advances in nanomaterials have offered novel approaches to restore tissue function after injury. In particular, carbon nanomaterials (CNMs) have shown significant promise to bridge the gap in clinical translation of biomaterial based therapies. This family of carbon allotropes (including graphenes, carbon nanotubes and fullerenes) have unique physiochemical properties, including exceptional mechanical strength, electrical conductivity, chemical behaviour, thermal stability and optical properties. These intrinsic properties make CNMs ideal materials for use in cardiovascular theranostics. This review is focused on recent efforts in the diagnosis and treatment of heart diseases using graphenes and carbon nanotubes. The first section introduces currently available derivatives of graphenes and carbon nanotubes and discusses some of the key characteristics of these materials. The second section covers their application in drug delivery, biosensors, tissue engineering and immunomodulation with a focus on cardiovascular applications. The final section discusses current shortcomings and limitations of CNMs in cardiovascular applications and reviews ongoing efforts to address these concerns and to bring CNMs from bench to bedside.

Enhanced sunlight driven photocatalytic activity of In2S3 nanosheets functionalized MoS2 nanoflowers heterostructures

Visible light-sensitive 2D-layered based photocatalytic systems have been proven one of the effective recent trends. We report the preparation of a 2D-layered based In₂S₃-MoS₂ nanohybrid system through a facile hydrothermal method, capable of efficiently degrading of organic contaminants with remarkable efficiency. Transmission electron microscopy (TEM) results inferred the attachment of 2D-layered In₂S₃ sheets with the MoS₂ nanoflakes. Field emission SEM studies with chemical mapping confirm the uniform distribution of Mo, In, and S atoms in the heterostructure, affirming sample uniformity. X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy results confirm the appearance of 2H-MoS₂ and β-In₂S₃ in the grown heterostructures. UV-DRS results reveal a significant improvement in the optical absorbance and significant bandgap narrowing (0.43 eV) in In₂S₃-MoS₂ nanohybrid compared to pristine In₂S₃ nanosheets in the visible region. The effective bandgap narrowing facilitates the charge transfer between MoS₂ and In₂S₃ and remarkably improves the synergistic effect. Effective bandgap engineering and improved optical absorption of In₂S₃-MoS₂ nanohybrids are favorable for enhancing their charge separation and photocatalytic ability. The photocatalytic decomposition efficiency of the pristine In₂S₃ nanosheets and In₂S₃-MoS₂ nanohybrids sample is determined by the decomposing of methylene blue and oxytetracycline molecules under natural sunlight. The optimized In₂S₃-MoS₂ nanohybrids can decompose 97.67% of MB and 76.3% of OTC-HCl molecules solution in 8 min and 40 min of exposure of sunlight respectively. 2D-layered In₂S₃-MoS₂ nanohybrids reveal the tremendous remediation performance towards chemical contaminations and pharmaceutical waste, which indicates their applicability in industrial and practical applications.

The usage of composite nanomaterials in biomedical engineering applications

Nanotechnology is still developing over the decades and it is commonly used in biomedical applications with the design of nanomaterials due to the several purposes. With the investigation of materials on the molecular level has increased the develop composite nanomaterials with exceptional properties using in different applications and industries. The application of these composite nanomaterials is widely used in the fields of textile, chemical, energy, defense industry, electronics, and biomedical engineering which is growing and developing on human health. Development of biosensors for the diagnosis of diseases, drug targeting and controlled release applications, medical implants and imaging techniques are the research topics of nanobiotechnology. In this review, overview of the development of nanotechnology and applications which is use of composite nanomaterials in biomedical engineering is provided.

Dopants and grain boundary effects in monolayer MoS2: a first-principles study

The structural, electronic and magnetic properties of large area chemical vapor deposited monolayer MoS2 rely significantly on the presence of grain boundaries (GBs) and defects. In this study, first-principles calculations were performed to investigate the electronic and magnetic properties of transition metal doped MoS2 GBs. The experimentally observed 60° tilt GBs were demonstrated with four different atomic configurations and the nonmagnetic 4|8ud GB has the lowest formation energy among the considered models. Further calculations of 4|8ud GBs doped with TMs, such as V, Cr, Mn, Fe, Co and Ni, indicate that dopants can significantly lower the formation energies of the doped GBs compared to the perfect monolayer MoS2 by occupying the GB region instead of within the grains. Magnetism can be achieved in doped GB systems by careful defect engineering. CoMo, MnMo and Niint in 4|8ud GBs are predicted to be magnetic and simultaneously energetically favorable. The electron coupling between the doped TM and surrounding GB atoms is expected to induce magnetism and high electron mobilities into the systems. This study may pave the way for optimal design of MoS2-based electronic and spintronic devices.

Two-Dimensional Nanostructures for Electrochemical Biosensor

Current advancements in the development of functional nanomaterials and precisely designed nanostructures have created new opportunities for the fabrication of practical biosensors for field analysis. Two-dimensional (2D) and three-dimensional (3D) nanomaterials provide unique hierarchical structures, high surface area, and layered configurations with multiple length scales and porosity, and the possibility to create functionalities for targeted recognition at their surface. Such hierarchical structures offer prospects to tune the characteristics of materials-e.g., the electronic properties, performance, and mechanical flexibility-and they provide additional functions such as structural color, organized morphological features, and the ability to recognize and respond to external stimuli. Combining these unique features of the different types of nanostructures and using them as support for bimolecular assemblies can provide biosensing platforms with targeted recognition and transduction properties, and increased robustness, sensitivity, and selectivity for detection of a variety of analytes that can positively impact many fields. Herein, we first provide an overview of the recently developed 2D nanostructures focusing on the characteristics that are most relevant for the design of practical biosensors. Then, we discuss the integration of these materials with bio-elements such as bacteriophages, antibodies, nucleic acids, enzymes, and proteins, and we provide examples of applications in the environmental, food, and clinical fields. We conclude with a discussion of the manufacturing challenges of these devices and opportunities for the future development and exploration of these nanomaterials to design field-deployable biosensors.

The Microbiome Meets Nanotechnology: Opportunities and Challenges in Developing New Diagnostic Devices

Monitoring of the human microbiome is an emerging area of diagnostics for personalized medicine. Here, the potential of different nanomaterials and nanobiosensing technologies is reviewed for the development of novel diagnostic devices for the detection and measurement of microbiome-related biomarkers. Moreover, the current and future landscape of microbiome-based diagnostics is defined by exploring the advantages and disadvantages of current nanotechnology-based approaches, especially in the context of developing point-of-care (PoC) devices that would meet the international guidelines known as REASSURED (Real-time connectivity; Ease of specimen collection; Affordability; Sensitivity; Specificity; User-friendliness; Rapid & robust operation; Equipment-free; and Deliverability). Finally, the strategies of the latest international scientific consortia working in this field are analyzed, the current microbiome diagnostics market are reported and the principal ethical, legal, and societal issues related to microbiome R&D and innovation are discussed.

Application of magnetic nanomaterials in bioanalysis

The importance of magnetic nanomaterials and magnetic hybrid materials, which are classified as new generation materials, in analytical applications is increasingly understood, and research on the adaptation of these materials to analytical methods has gained momentum. Development of sample preparation techniques and sensor systems using magnetic nanomaterials for the analysis of inorganic, organic and biomolecules in biological samples, which are among the samples that analytical chemists work on most, are among the priority issues. Therefore in this review, we focused on the use of magnetic nanomaterials for the bioanalytical applications including inorganic and organic species and biomolecules in different biological samples such as primarily blood, serum, plasma, tissue extracts, urine and milk. We summarized recent progresses, prevailing techniques, applied formats, and future trends in sample preparation-analysis methods and sensors based on magnetic nanomaterials (Mag-NMs). First, we provided a brief introduction of magnetic nanomaterials, especially their magnetic properties that can be utilized for bioanalytical applications. Second, we discussed the synthesis of these Mag-NMs. Third, we reviewed recent advances in bioanalytical applications of the Mag-NMs in different formats. Finally, recently literature studies on the relevance of Mag-NMs for bioanalysis applications were presented.

Highly exfoliated functionalized MoS2 with sodium alginate-polydopamine conjugates for electrochemical sensing of cardio-selective β-blocker by voltammetric methods

Molybdenum disulfide (MoS₂) surface functionalization was performed with a catechol-containing polymer sodium alginate (SA) and dopamine (DA) through simultaneous MoS₂ exfoliation and self-polymerization of DA. The MoS₂/SA-PDA nanocomposite was characterized using spectroscopic, microscopic, and electroanalytical techniques to evaluate its electrocatalytic performance. The electrocatalytic behavior of the MoS₂/SA-PDA nanocomposite modified electrode for the detection of acebutolol (ACE), a cardio-selective β-blocker drug was explored  through cyclic voltammetric and differential pulse voltammetric techniques. The influence of scan rate, concentration, and pH value on the oxidation peak current of ACE was investigated  to optimize the deducting condition. The electrochemical activity of the MoS₂/SA-PDA nanocomposite electrode was attributed to the existence of reactive functional groups being contributed from SA, PDA, and MoS₂ exhibiting a synergic effect. The MoS₂/SA-PDA nanocomposite modified electrode exhibits admirable electrocatalytic activity with a wide linear response range (0.009 to 520 μM), low detection limit (5 nM), and high sensitivity (0.354 μA μM^-1 cm^-2) also in the presence of similar (potentially interfering) compounds. The fabricated MoS₂/SA-PDA nanocomposite modified electrode can be useful for the detection of ACE in pharmaceutical analysis.

Molybdenum disulfide-based materials with enzyme-like characteristics for biological applications

Nanozyme, a kind of nanomaterials with enzymatic activity, has been developing vigorously over the past years owing to its advantages such as low-cost, easy storage, ease of use in harsh environments and so on, compared with natural enzymes. At present, as a typical two-dimensional nanomaterial, molybdenum disulfide (MoS₂) and their hybrids with unexpected enzyme-like activities have caused wide attention. In this review, we mainly investigated the enzyme-like activities of MoS₂ based nanomaterials, including peroxidase-like activity, catalase-like activity and superoxide dismutase-like activity. Furthermore, we systematically introduce recent research progress of MoS₂ based nanomaterials in the fields of biological applications such as radiation protection, cancer therapy, antibacterial, and wound healing. Finally, the current challenges and perspectives of MoS₂ based nanomaterials in the future are also discussed and proposed. We expect this review may be significant to understand the properties of MoS₂ based nanomaterials and the development of two-dimensional nanomaterials with enzyme mimicking activities.

Crystal reorientation and plastic deformation of single-layer MoS2 and MoSe2 under uniaxial stress

We investigate theoretically, through of first-principles calculations, the effect of the application of large in-plane uniaxial stress on single-layer of MoS2, MoSe2, and MoSSe alloys. For stress applied along the zigzag (zz) direction, we predict an anomalous behavior near the point fracture. This behavior is characterized by the reorientation of the MoS2 structure along the applied stress from zz to armchair due to the formation of transient square-lattice regions in the crystal, with an apparent crystal rotation of 30 degrees. After reorientation, a large plastic deformation [Formula: see text] remains after the stress is removed. This behavior is also observed in MoSe2 and in MoSSe alloys. This phenomenon is observed both in stress-constrained geometry optimizations and in ab initio molecular dynamics simulations at finite temperature and applied stress.

Gd doped molybdenum selenide/carbon nanofibers: an excellent electrocatalyst for monitoring endogenous H2S

Design and synthesis of Gd doped molybdenum selenide/carbon nanofibers for monitoring H₂S.

Electrochemical impedimetric biosensors, featuring the use of Room Temperature Ionic Liquids (RTILs): Special focus on non-faradaic sensing

Over the last decade, significant advancements have been made in the field of biosensing technology. With the rising demand for personalized healthcare and health management tools, electrochemical sensors are proving to be reliable solutions; specifically, impedimetric sensors are gaining considerable attention primarily due to their ability to perform label-free sensing. The novel approach of using Room Temperature Ionic Liquids (RTILs) to improve the sensitivity and stability of these detection systems makes long-term continuous sensing feasible towards a wide range of sensing applications, predominantly biosensing. Through this review, we aim to provide an update on current scientific progress in using impedimetric biosensing combined with RTILs for the development of sensitive biosensing platforms. This review also summarizes the latest trends in the field of biosensing and provides an update on the current challenges that remain unsolved.

Recent advances on TMDCs for medical diagnosis

Transition metal dichalcogenides (TMDCs), such as MoS₂ and WS₂, have attracted much attention in biosensing and bioimaging due to its excellent stability, biocompatibility, high specific surface area, and wide varieties. In this review, we overviewed the application of TMDCs in biosensing and bioimaging. Firstly, the synthesis methods and surface functionalization methods of TMDCs were summarized. Secondly, according to the working mechanism, we classified and gave a detailed account of the latest research progress of TMDC-based biosensing for the detection of the enzyme, DNA, and other biological molecules. Then, we outlined the recent progress of applying TMDCs in bio-imaging, including fluorescence, X-ray computed tomographic, magnetic response imaging, photographic and multimodal imaging, respectively. Finally, we discussed the future challenges and development direction of the application of TMDCs in medical diagnosis. Also, we put forward our view on the opportunity of TMDCs in the big data of modern medical diagnosis.

Mo-Based Layered Nanostructures for the Electrochemical Sensing of Biomolecules

Mo-based layered nanostructures are two-dimensional (2D) nanomaterials with outstanding characteristics and very promising electrochemical properties. These materials comprise nanosheets of molybdenum (Mo) oxides (MoO2 and MoO3), dichalcogenides (MoS2, MoSe2, MoTe2), and carbides (MoC2), which find application in electrochemical devices for energy storage and generation. In this feature paper, we present the most relevant characteristics of such Mo-based layered compounds and their use as electrode materials in electrochemical sensors. In particular, the aspects related to synthesis methods, structural and electronic characteristics, and the relevant electrochemical properties, together with applications in the specific field of electrochemical biomolecule sensing, are reviewed. The main features, along with the current status, trends, and potentialities for biomedical sensing applications, are described, highlighting the peculiar properties of Mo-based 2D-nanomaterials in this field.

Plasmonic active film integrating gold/silver nanostructures for H2O2 readout

A nanostructured Ag/Au adhesive film for H₂O₂ reagentless determination is here proposed. The film has been realised onto ELISA polystyrene microplates. Microwells surface has been initially modified with a gold nanoparticles (AuNPs)/polydopamine thin-film. The pristine AuNPs-decorated film was later functionalized with catechin (Au-CT) allowing a uniform formation of a plasmonic active nanostructured silver network in presence of Ag⁺. Changes in localized surface plasmon resonance (LSPR) of the silver network upon addition of H₂O₂ has been used as analytical signal, taking advantage of the etching phenomenon. The Ag/Au nanocomposite-film is characterized by a well-defined (LSPR_max = 405 ± 5 nm), reproducible (intraplate RSD ≤ 9.8%, n = 96; inter-plate RSD ≤ 11.4%, n = 480) and stable LSPR signal. The film's analytical features have been tested for H₂O₂ and glucose (bio)sensing. Satisfactory analytical performances were obtained both for H₂O₂ (linear range 1-200 μM, R² = 0.9992, RSD ≤ 6.3%, LOD = 0.2 μM) and glucose (linear range 2-250 μM, R² = 0.9998, RSD ≤ 8.9%, LOD = 0.4 μM). As proof of applicability, the determination of the two analytes in soft drinks has been carried out achieving good and reproducible recoveries (84-111%; RSD ≤ 9%). The developed nanostructured film overcomes analytical drawbacks associated with the use of colloidal dispersions in plasmonic assays carried out in solution; the low cost, robustness, ease of use and possibility of coupling enzymatic reactions appears very promising for (bio)sensors based on the detection of H₂O₂.

Applications of Bionano Sensor for Extracellular Vesicles Analysis

Recently, extracellular vesicles (EVs) and their contents have been revealed to play crucial roles in the intrinsic intercellular communications and have received extensive attention as next-generation biomarkers for diagnosis of diseases such as cancers. However, due to the structural nature of the EVs, the precise isolation and characterization are extremely challenging. To this end, tremendous efforts have been made to develop bionano sensors for the precise and sensitive characterization of EVs from a complex biologic fluid. In this review, we will provide a detailed discussion of recently developed bionano sensors in which EVs analysis applications were achieved, typically in optical and electrochemical methods. We believe that the topics discussed in this review will be useful to provide a concise guideline in the development of bionano sensors for EVs monitoring in the future. The development of a novel strategy to monitor various bio/chemical materials from EVs will provide promising information to understand cellular activities in a more precise manner and accelerates research on both cancer and cell-based therapy.

Electroactive polypyrrole-molybdenum disulfide nanocomposite for ultrasensitive detection of berberine in rat plasma

Electroactive polypyrrole-molybdenum disulfide (MoP) nanocomposites were synthesized and used for modifying screen-printed carbon electrodes (SPCEs) for ultrasensitive detection of berberine, an anticancer drug, in rat plasma. The electroactive nanocomposites were fabricated by exfoliating MoS₂ followed by pyrrole polymerization. The effect of polypyrrole in the MoP nanocomposite was evaluated by varying the pyrrole concentration during polymerization, and the resulting nanocomposites prepared with pyrrole concentrations of 10, 20, 30 μL were named as MoP-1, MoP-2, and MoP-3, respectively. The electrochemical characterization of the three MoP nanocomposite sensors revealed that MoP-2/SPCE exhibited the highest electroactivity. The detection of berberine by the three MoP-coated SPCEs revealed that MoP-2/SPCE exhibited the highest activity against berberine due to a two-electron transfer mechanism on the MoP-2/SPCE electrode surface. The detection limit of berberine using the MoP-2/SPCE sensor was found to be about 0.05 μM, which is remarkably lower than the reported detection limits. The interference study proved the selectivity of the MoP-2/SPCE sensor toward berberine in the presence of other bioactive molecules and metal ions. The designed MoP-2/SPCE sensor retained 92% of its initial activity after 15 days of storage at room temperature, with RSD values of about 2.95% and 3.68% for the repeatability and reproducibility studies. Finally, the detection limit of berberine in a rat plasma sample determined using the MoP-2/SPCE sensor was found to be about 5 μM.

Electrochemical sensor based on CuSe for determination of dopamine

A simple binary copper selenide, CuSe nanostructure, has been investigated as electrochemical sensor for dopamine detection. The hydrothermally synthesized and electrodeposited CuSe nanostructures showed high sensitivity for dopamine detection with low limit of detection (LOD). A sensitivity of 26 μA/μM.cm² was obtained with this electrochemical sensor which is ideal to detect even small fluctuations in the transient dopamine concentration. Apart from high sensitivity and low LOD, the dopamine oxidation on the catalyst surface also occurred at a low applied potential (< 0.18 V vs Ag|AgCl), thereby significantly increasing selectivity of the process specifically with respect to ascorbic and uric acids, which are considered to be the most prominent interferents for dopamine detection. Electrochemical redox tunability of the catalytic Cu center along with low coordination geometry is believed to enhance the rate of dopamine attachment and oxidation on the catalyst surface thereby reducing the applied potential. The presence of Cu also increases conductivity of the catalyst composite which further improves the charge transfer thus increasing the sensitivity of the device. This is the first report of electrochemical dopamine sensing with a simple binary selenide comprising earth-abundant elements and can have large significance in designing efficient sensors that can be transformative for understanding neurodegenerative diseases further. Graphical abstract.

Emerging pnictogen-based 2D semiconductors: sensing and electronic devices

Pnictogens are an intensively studied group of monoelemental two-dimensional materials. This group of elements consists of phosphorus, arsenic, antimony, and bismuth. In this group, the elements adopt two different layered structural allotropes, orthorhombic structure with true van der Waals layered interactions and rhombohedral structure, where covalent interactions between layers are also present. The orthorhombic structure is well known for phosphorus and arsenic, and the rhombohedral structure is the most thermodynamically stable allotropic modification of arsenic, antimony, and bismuth. Due to the electronic structure of pnictogen layers and their semiconducting character, these materials have huge application potential for electronic devices such as transistors and sensors including photosensitive devices as well as gas and electrochemical sensors. While photodetection and gas sensing applications are often related to lithography processed materials, chemical sensing proceeds in a liquid environment (either aqueous or non-aqueous) and can be influenced by surface oxidation of these materials. In this review, we explore the current state of pnictogen applications in sensing and electronic devices including transistors, photodetectors, gas sensors, and chemical/electrochemical sensors.

Metal Oxides-Based Semiconductors for Biosensors Applications

The present mini review contains a concessive overview on the recent achievement regarding the implementation of a metal oxide semiconductor (MOS) in biosensors used in biological and environmental systems. The paper explores the pathway of enhancing the sensing characteristics of metal oxides by optimizing various parameters such as synthesis methods, morphology, composition, and structure. Four representative metal oxides (TiO₂, ZnO, SnO₂, and WO₃) are presented based on several aspects: synthesis method, morphology, functionalizing molecules, detection target, and limit of detection (LOD).

Terahertz polarization sensing based on metasurface microsensor display anti-proliferation of tumor cells with aspirin

The inhibition effects of aspirin on cell proliferation are investigated by both traditional THz resonance sensing and the improved THz polarization sensing method based on a polarization dependent metasurface microsensor. Compared to resonance sensing, the quality factor of polarization sensing is 4∼5 times higher than that of resonance sensing, and its figure of merit is at least one order of magnitude higher than that of the resonance sensing with the same metasurface microsensor. Our proposed metasurface-based biosensors may supply a novel viewpoint on cell proliferation from a physical perspective and be a valuable complementary reference for biological study.

Ag2S QDs/Si Heterostructure-Based Ultrasensitive SWIR Range Detector

In the 20th century, microelectronics was revolutionized by silicon-its semiconducting properties finally made it possible to reduce the size of electronic components to a few nanometers. The ability to control the semiconducting properties of Si on the nanometer scale promises a breakthrough in the development of Si-based technologies. In this paper, we present the results of our experimental studies of the photovoltaic effect in Ag2S QD/Si heterostructures in the short-wave infrared range. At room temperature, the Ag2S/Si heterostructures offer a noise-equivalent power of 1.1 × 10-10 W/√Hz. The spectral analysis of the photoresponse of the Ag2S/Si heterostructures has made it possible to identify two main mechanisms behind it: the absorption of IR radiation by defects in the crystalline structure of the Ag2S QDs or by quantum QD-induced surface states in Si. This study has demonstrated an effective and low-cost way to create a sensitive room temperature SWIR photodetector which would be compatible with the Si complementary metal oxide semiconductor technology.

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.

Physical and chemical template-blocking strategies in the exponential amplification reaction of circulating microRNAs

The detection of circulating miRNA through isothermal amplification wields many attractive advantages over traditional methods, such as reverse transcription RT-qPCR. However, it is challenging to control the background signal produced in the absence of target, which severely hampers applications of such methods for detecting low abundance targets in complex biological samples. In the present work, we employed both the cobalt oxyhydroxide (CoOOH) nanoflakes and the chemical modification of hexanediol to block non-specific template elongation in exponential amplification reaction (EXPAR). Adsorption by the CoOOH nanoflakes and the hexanediol modification at the 3' end effectively prevented no-target polymerization on the template itself and thus greatly improved the performance of EXPAR, detecting as low as 10 aM of several miRNA targets, including miR-16, miR-21, and miR-122, with the fluorescent DNA staining dye of SYBR Gold™. Little to no cross-reactivity was observed from the interfering strands present in 10-fold excess. Besides contributing to background reduction, the CoOOH nanoflakes strongly adsorbed nucleic acids and isolated them from a complex sample matrix, thus permitting successful detection of the target miRNA in the serum. We expect that simple but sensitive template-blocking EXPAR could be a valuable tool to help with the discovery and validation of miRNA markers in biospecimens. Graphical abstract.

Screen-printed electrochemical biosensor based on a ternary Co@MoS2/rGO functionalized electrode for high-performance non-enzymatic glucose sensing

In this study, cobalt oxides functionalized MoS₂/reduced graphene oxide was synthesized via a facile one-pot hydrothermal approach. Morphology and crystal structure of this ternary nanoarchitecture were characterized through scanning electron microscopy, transmission electron microscopy, Raman spectra and X-ray photoelectron spectroscopy. An ultrasensitive non-enzymatic glucose sensor was developed by decorating this ternary nanohybrid on the working electrode of a screen-printed electrochemical sensor. Cycle sweep voltammetry and amperometry were used to study the electro-catalytic activity of the modified working electrode, which demonstrated superior catalytic activity towards glucose oxidation with an extremely low detection limit of 30 nM. Meanwhile, this sensor showed an excellent selectivity in the presence of interfering species such as uric acid, ascorbic acid, etc. Based on the screen-printed technique, enzyme mimic nanomaterials could be easily introduced into portable devices, which opens the way to take non-enzymatic glucose electrochemical sensing towards point-of-care.

A highly sensitive electrochemical biosensor for protein based on a tetrahedral DNA probe, N- and P-co-doped graphene, and rolling circle amplification

A tetrahedral DNA probe can effectively overcome the steric effects of a single-stranded probe to obtain well-controlled density and minimize nonspecific adsorption. Herein, a highly sensitive electrochemical biosensor is fabricated for determination of protein using a tetrahedral DNA probe and rolling circle amplification (RCA). N- and P-co-doped graphene (NP-rGO) is prepared, and AuNPs are then electrodeposited on it for DNA probe immobilization. Benefitting from the synergistic effects of the excellent electrical conductivity of NP-rGO, the stability of the tetrahedral DNA probe and the signal amplification of RCA, the biosensor achieves a low limit of 3.53 × 10^-14 M for thrombin and a wide linear range from 1 × 10^-13 to 1 × 10^-7 M. This study provides a sensitive and effective method for the detection of protein in peripheral biofluids, and paves the way for future clinical diagnostics and treatment of disease. Graphical abstract.

Organochalcogen ligands in catalysis of oxidation of alcohols and transfer hydrogenation

Organochalcogen compounds have been used as the building blocks for the development of a variety of catalysts that have been studied comprehensively during the last two decades for several chemical transformations. Transfer hydrogenation (reduction of carbonyl compounds to alcohols) and oxidation of alcohols (conversion of alcohols to their respective ketones and aldehydes) are also among such chemical transformations. Some compilations are available in the literature on the development of catalysts, based on organochalcogen ligands, and their applications in Heck reaction, Suzuki reaction, and other related aspects. Some review articles have also been published on different aspects of oxidation of alcohols and transfer hydrogenation. However, no such article is available in the literature on the syntheses and use of organochalcogen ligated catalysts for these two reactions. In this perspective, a survey of developments pertaining to the synthetic aspects of such organochalcogen (S/Se/Te) based catalysts for the two reactions has been made. In addition to covering the syntheses of chalcogen ligands, their metal complexes and nanoparticles (NPs), emphasis has also been placed on the efficient conversion of different substrates during catalytic reactions, diversity in catalytic potential and mechanistic aspects of catalysis. It also includes the analysis of comparison (in terms of efficiency) between this unique class of catalysts and efficient catalysts without a chalcogen donor. The future scope of this area has also been highlighted.

Layered α-MoO3 nanoplates for gas sensing applications

A versatile chemical route to produce rectangular layered α-MoO₃ nanoplates with enhanced NO₂ gas sensing response.

Nanoelectrochemical biosensors for monitoring ROS in cancer cells

A novel strategy has been constructed based on a SiC@C nanowire electrode for intracellular electrochemical analysis to monitor ROS levels in cancer or tumor cells.

Two-Dimensional Layered Nanomaterial-Based Electrochemical Biosensors for Detecting Microbial Toxins

Toxin detection is an important issue in numerous fields, such as agriculture/food safety, environmental monitoring, and homeland security. During the past two decades, nanotechnology has been extensively used to develop various biosensors for achieving fast, sensitive, selective and on-site analysis of toxins. In particular, the two dimensional layered (2D) nanomaterials (such as graphene and transition metal dichalcogenides (TMDs)) and their nanocomposites have been employed as label and/or biosensing transducers to construct electrochemical biosensors for cost-effective detection of toxins with high sensitivity and specificity. This is because the 2D nanomaterials have good electrical conductivity and a large surface area with plenty of active groups for conjugating 2D nanomaterials with the antibodies and/or aptamers of the targeted toxins. Herein, we summarize recent developments in the application of 2D nanomaterial-based electrochemical biosensors for detecting toxins with a particular focus on microbial toxins including bacterial toxins, fungal toxins and algal toxins. The integration of 2D nanomaterials with some existing antibody/aptamer technologies into electrochemical biosensors has led to an unprecedented impact on improving the assaying performance of microbial toxins, and has shown great promise in public health and environmental protection.