Living organisms increasingly grapple with the impact of rapid environmental changes, including climate shifts, pollution, and resource scarcity. To effectively address these challenges, advanced monitoring tools are essential. Traditional methods like gas chromatography, high-performance liquid chromatography, and mass spectrometry, while effective, suffer from high costs, time-intensive procedures, and reliance on specialized equipment and expertise. In this context, nanoparticle synthesis technology emerges as a promising solution. By precisely controlling size, shape, and properties at the nanoscale, it enables the development of advanced sensors. These nanosensors offer rapid response times, heightened sensitivity, and selectivity, making them ideal for accurate environmental and health monitoring. Nanomaterials (NMs), with their unique attributes, such as a high surface area-to-volume ratio and exceptional electronic, optical, and mechanical properties—outperform traditional methods in detecting minute quantities of contaminants and environmental fluctuations. This chapter explores the use of bismuth chalcogenides nanostructures in sensing applications. It covers synthesis methods, sensor fabrication, and characterization techniques, highlighting bismuth chalcogenides such as Bi2S3, Bi2Se3, and Bi2Te3 for their high carrier mobility, extensive surface area, and tunable properties, making them promising candidates for cost-effective, sensitive sensors

Bacterial infections and the rise of antibiotic-resistant strains pose a critical challenge to public health and has intensified the need for alternative antimicrobial agents. This study explores the synthesis, characterization, and antibacterial efficacy of hexagonal Bi2Te3 platelets prepared via a solvothermal method using polyvinylpyrrolidone (PVP) as a stabilizer, ensuring high dispersion stability and preventing agglomeration. The synthesized Bi2Te3 nanoparticles were thoroughly characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM), Raman and Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), confirming the crystalline quality, surface properties, and functional groups of the Bi2Te3 platelets. The antibacterial efficacy was assessed using well-diffusion assays and minimum inhibitory concentration (MIC) tests, demonstrating effective bactericidal action, particularly against Gram-positive bacteria, attributed to membrane disruption and reactive oxygen species (ROS) generation. Additionally, cytotoxicity studies on A549 lung carcinoma cells indicated dose-dependent effects, supporting the biocompatibility of Bi2Te3 at optimal concentrations. The scalable of hexagonal Bi2Te3 platelets position them as promising candidates for advanced antibacterial applications

This work reports the synthesis of CuFe2O4 (CFO) nanoparticles via the co-precipitation method for supercapacitor applications, emphasizing the effect of annealing temperature. High-resolution X-ray diffraction (HR-XRD) confirms a tetragonal spinel phase, with grain size increasing due to Ostwald ripening. Raman spectra further validate CFO's tetragonal phase, while FE-SEM confirms nanoparticle agglomeration. HR-TEM analysis reveals an average particle size of ?71.66 nm. FTIR identifies functional groups, and EDS confirms the presence of Cu, Fe, and O, with XPS verifying Cu2+, Fe2+, Fe3+, and O2? oxidation states. Magnetic measurements indicate ferromagnetic behaviour. BET analysis shows that CFO annealed at 800 °C has the highest specific surface area, improving electrochemical performance. Electrochemical tests (CV, GCD, and EIS) reveal optimal redox activity and ion diffusion at 800 °C, achieving a specific capacitance of 911.1 F/g at 1 A/g. An asymmetric supercapacitor with CFO-800 used as positive electrode while negative electrode made of activated carbon delivers 44.42 F/g capacitance, 12.97 Wh/kg energy density, and 3.92 kW/kg power density, with 77.26 % cycling retention and 101.8 % Coulombic efficiency over 5000 cycles. These results highlight CFO's potential for next-generation energy storage applications.

We successfully synthesized ?-MoO3 nanolayers using a proximity evaporation technique, positioning the Mo film approximately 1 mm from the target substrate at atmospheric conditions. This novel method bypasses the need for supplemental oxygen sources by utilizing ambient oxygen, resulting in cost-effective and scalable production of MoO3. The ?-MoO3 films synthesized at an optimal growth temperature of 550 °C demonstrate well-controlled layer thickness, high crystallinity, and uniform stoichiometry. Detailed characterizations were performed, including XRD for crystallographic confirmation, SEM–EDS for morphology and stoichiometry, Raman spectroscopy for vibrational modes, and UV–Vis for optical properties, revealing a tunable bandgap of approximately 3.7 eV. I-V measurements indicated a high resistance of 8.7×106 ?, confirming the material’s insulating nature, and an optimum dielectric constant of 1253. Photo-response measurements demonstrated a significant photocurrent increase under illumination, with responsivity 8.8 A.W?1, detectivity1.2×1013 J, and quantum efficiency of 18.5%, respectively. The proposed proximity evaporation technique demonstrates potential as a scalable approach for synthesizing high-quality two-dimensional (2D) transition metal oxides like MoO3, with implications for applications in optoelectronics and sensing

Easy-to-fabricate, flexible optoelectronic devices based on conducting organic polymers are in high demand due to their cost-effectiveness and low weight. The hole and electron transport layers (HTL/ELT) are central to the working of these devices. Conductive polymers are now extensively used (HTL/ETL) in solar cells, as hole injection layers in OLEDs, and as electrodes or active channel layers in organic thin film transistors. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is the mainstay of these devices. The energy levels of the tailored PEDOT:PSS determine the work function, the efficiency of charge separation, and the device’s performance. Transparent electrodes are another requirement for the efficient functioning of devices, with indium tin oxide (ITO) being a common choice. To overcome problems associated with ITO, researchers are focusing on conducting polymer materials such as PEDOT:PSS as transparent electrode materials. Flexibility, water processability, high electrical conductivity, good optical transparency, biocompatibility, and good thermoelectric properties make functionalized PEDOT:PSS a versatile conductive polymer. Priced for its versatility and good performance, it is used in cutting-edge applications including LEDs, solar cells, and sensors. Cost-effective production and easy production scalability make it a default material for optoelectronic applications despite some challenges. This review highlights recent research with special emphasis on tuning the work function of PEDOT:PSS to enhance the performance of optoelectronic devices

The increasing environmental challenges caused by pharmaceutical waste, especially antibiotics and contaminants, necessitate sustainable solutions. Cellulose-based membranes are considered advanced tools and show great potential as effective materials for the removal of drugs and organic contaminants. This review introduces an environmentally friendly composite membrane for the elimination of antibiotics and dye contaminants from water and food, without the use of toxic additives. The potential of cellulose-based membranes in reducing the impact on water quality and promoting environmental sustainability is emphasized. Additionally, the benefits of using biobased cellulose membranes in membrane biological reactors for the removal of antibiotics from pharmaceutical waste and milk are explored, presenting an innovative approach to achieving a circular economy. This review provides recent and comprehensive insights into membrane bioreactor technology, making it a valuable resource for researchers seeking efficient methods to break down antibiotics in industrial wastewater, particularly in the pharmaceutical and dairy industries.

The escalating need for lithium-ion batteries (LIBs), driven by their expanding range of applications in our daily lives, has led to a surge in interest in metal selenides as potential anode materials. Among them, Bi2Se3 stands out as a promising anode material for LIBs due to its unique layered structure. Herein, we explored hexagonally structured layered Bi2Se3 platelets synthesized using the solvothermal method. The electrochemical performance of these platelets in LIBs was thoroughly examined, revealing an impressive initial discharge specific capacity of 556 mA h g?1 at a current density of 100 mA g?1 and a coulombic efficiency of 66.5%. Improved cycling stability, rate performance, and discharge voltage profile at various current densities were observed. The plateaus observed during the charge/discharge profile were clearly illustrated by the CV results. The reaction kinetics indicated that both ion diffusion and pseudo-capacitance behavior are crucial for the observed high electrochemical performance. Moreover, the hexagonal Bi2Se3 platelets exhibited a high ion-diffusion coefficient of 1.8 × 10?13 cm2 s?1 and a charge transfer impedance of 23 ? post-cycling. Furthermore, the crystal structure, lattice vibrational bonding, and surface morphology of Bi2Se3 were explored using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. FTIR spectroscopy was utilized for identifying the functional groups, while X-ray photoelectron spectroscopy (XPS) was used to identify the elemental composition and oxidation states of Bi2Se3

The burgeoning electronics industry has sparked a corresponding surge in electromagnetic pollution, necessitating robust shielding methods with a focus on absorption. Polymer-based composites, especially those incorporating polyaniline (PANI), are pivotal in this endeavor due to their electrical conductivity and cost-effectiveness. This review provides a comprehensive examination of current state-of-the-art research in the field of electromagnetic shielding materials, exploring their applications, benefits, and limitations. Graphene’s exceptional mechanical, electrical, and optical properties, when combined with PANI matrices, elevate electromagnetic interference shielding effectiveness (EMI SE). Its unique characteristics enhance electron transport, boosting overall electrical conductivity and reflectivity. Simultaneously, carbon nanotubes show promise for polymer composites, leveraging their superior strength, stiffness, aspect ratio, and electrical conductivity. The inclusion of Fe3O4 magnetic material significantly impacts composite permeability due to its large saturation magnetization. MXene, a two-dimensional transition metal carbonitride, emerges as a promising option for electromagnetic interference (EMI) shielding. With electrical conductivity and specific surface area comparable to graphene, MXene is gaining attention in EMI shielding research. The review explores diverse strategies utilizing various fillers to enhance PANI-based nanocomposites for EMI shielding, presenting a comprehensive overview of advanced shielding materials in various applications. © 2024 Taylor & Francis.

Over the past few decades, the financial industry has shown a keen interest in using computational intelligence to improve various financial processes. As a result, a range of models have been developed and published in numerous studies. However, in recent years, deep learning (DL) has gained significant attention within the field of machine learning (ML) due to its superior performance compared to traditional models. There are now several different DL implementations being used in finance, particularly in the rapidly growing field of Fintech. DL is being widely utilized to develop advanced banking services and investment strategies. This chapter provides a comprehensive overview of the current state-of-the-art in DL models for financial applications. The chapter is divided into categories based on the specific sub-fields of finance, and examines the use of DL models in each area. These include algorithmic trading, price forecasting, credit assessment, and fraud detection. The chapter aims to provide a concise overview of the various DL models being used in these fields and their potential impact on the future of finance. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.

This study explores the capabilities of solvothermally synthesized bismuth telluride (BiTe) hexagonal platelets as a promising anode material for both Li-ion and Na-ion batteries. BiTe anode material exhibits a high initial discharge capacity of 837 mA h g at a current density of 100 mA g against Li metal whereas, an initial discharge capacity of 678 mA h g is observed at a current density of 20 mA g for the same against the Na metal. The Li- and Na-storage mechanism in BiTe platelets has been investigated by using both galvanostatic charge–discharge and cyclic voltammetry measurements. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy techniques have been used to examine the structural characteristics, surface morphology, and lattice vibrational modes of BiTe hexagonal platelets. Further, FTIR spectroscopy was employed to determine the presence of functional groups while X-ray photoelectron spectroscopy was employed for the elemental analysis of BiTe sample. Graphical abstract: (Figure presented.)

Nickel ferrite (NiFe 2 O 4 ) nanostructures (NSs) were synthesized via a low-cost and reproducible co-precipitation method. The as-synthesized material was annealed at different temperatures to investigate electrochemical performances for oxygen reduction reaction (ORR) and energy storage capacity. The X-ray diffraction (XRD) pattern confirmed the cubic structure of NiFe 2 O 4 (NF) NSs. The decreased agglomeration and increased particle size were observed by field effect scanning electron microscopy (FE-SEM) with annealing temperature. The presence of Ni–O and Fe–O bonds at tetrahedral and octahedral sites was confirmed by Fourier transform infrared (FTIR) spectroscopy. The electrochemical analysis studied using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) demonstrated that the NF NSs annealed at 900 °C exhibited impressive electrochemical activity with a specific capacitance of ?136 F/g, outperforming samples synthesized at lower temperatures. Moreover, the electrode material displayed excellent long-term stability over 3000 cycles for ORR activity. The remarkable electrochemical performance of NF NSs at higher annealing temperatures highlights their potential for future energy storage and conversion devices.

Increasing dependence and usage of electronic devices has raised the concern for electromagnetic (EM) shielding. This review article is an overview of ongoing cutting-edge research on electromagnetic shielding materials, their applications, advantages and shortcomings. The article highlights doping of polypyrrole(PPy) with different components to achieve desired properties. The work focusses on methods of achieving desired properties of PPy through doping. We have summarized results of doping it with Graphene, Nickel, MXene, Iron Oxide and CNT to achieve desired properties like better electrical conductivity, flexibility and lighter material, greater tensile strength, biocompatibility, better microwave absorption and better magnetic properties. The review presents compilation of most recent ongoing research in the field of electromagnetic shielding. We have also discussed existing limitations and possible future prospects in the ongoing research.

Green Hydrogen emerges as a promising energy solution in the quest for achieving Net Zero goals. The application of particulate semiconductors in photocatalytic water splitting introduces a potentially scalable and economically viable technology for converting solar energy into hydrogen. Overcoming the challenge of efficiently transferring photoelectrons and photoholes for both reduction and oxidation on the same catalyst is a significant hurdle in photocatalysis. In this context, we introduce highly efficient crystalline elemental boron nanostructures as photocatalysts, employing a straightforward and scalable synthesis method yield green hydrogen production without the need for additional co-catalysts or sacrificial agents. The resulting photocatalyst demonstrates stability and high activity in H 2 production, achieving over 1 % solar-to-hydrogen energy conversion efficiency (>15,000 ?mol. g ?1.h ?1 ) during continuous 12-h illumination. This efficiency is credited to broad optical absorption and the crystalline nature of boron nanostructures, paving the way for potential scale-up of reactors using crystalline boron photocatalysts.

p-type cupric oxide (p-CuO) thin films on n-type silicon substrates were grown to make p-CuO/n-Si heterojunctions. The CuO deposition on Si was carried out using radio frequency (RF) magnetron sputtering followed by rapid thermal annealing at 350°C. Plasma nitridation was used to incorporate nitrogen (N) for improving the electrical conductivity of the CuO thin films. The crystalline structure and surface composition of RF-sputtered CuO were characterized by x-ray diffraction and x-ray photoelectron spectroscopy. It was observed that the introduction of nitrogen in CuO improves the photovoltaic properties, such as the open-circuit voltage, short circuit current, and the photocurrent of the p-CuO-n-Si heterojunction.

Cadmium sulfide (CdS) nanoparticles (NPs) were synthesized using a biodegradable starch [(CHO)] polymer as a capping and stabilizing agent. The as-synthesized CdS NPs were highly crystalline and had a hexagonal structure with an average particle size of ~ 10.5 nm. Fourier transform infrared (FTIR) spectroscopy analysis was used to examine the presence and interactions of starch on the surface of the nanoparticles. The electronic behavior of CdS NPs was analyzed using I–V measurements and impedance spectroscopy. These NPs exhibit semiconducting behavior with resistance and conductance values of 1.78 ×10 ?, and 5.61 × 10 S, respectively. Photoresponse studies of CdS NPs showed significant photoresponse with improved photocurrent under light conditions. The dielectric measurements were done at different temperatures, during both the heating and cooling cycles, and the frequency dependence and temperature dependence of dielectric constant and dielectric loss were investigated.

Fabricating large-area two-dimensional (2D) metal dichalcogenide layers with stoichiometry and uniformity has been a research focus over the past few years. Most of the time, the types of growth methods determine of quality of the 2D layers, and in turn, they affect their electronic properties and applications. Here, we report a nonconventional facile way of synthesizing nearly single crystalline 2H hexagonal SnS and orthorhombic SnS layers via proximity evaporation, where the distance between the Sn precursor film and the target substrate is ~1 mm. This short distance provides self-limiting 2D layers with good uniformity and stoichiometry. The phase transition study was carried out by varying the growth temperature (300–650°C). Pure phases of SnS and SnS were formed at the optimum temperatures. Large hexagonal SnS sheets with a 1:2 stoichiometric ratio were observed. The high-resolution transmission electron microscopy (HRTEM) and Raman spectra further revealed the 2H phase of SnS sheets. Photoresponse studies of both pure phases of SnS and SnS showed significant photoresponse with improved photocurrent. Our synthesis method can be extended to grow large-area uniform sheets of other 2D materials having lower heat of formation. Graphical Abstract: [Figure : see fulltext.]

Lithium-Sulfur batteries (LSBs) are one of the most promising next-generation batteries to replace Li-ion batteries that power everything from small portable devices to large electric vehicles. LSBs boast a nearly five times higher theoretical capacity than Li-ion batteries due to sulfur’s high theoretical capacity, and LSBs use abundant sulfur instead of rare metals as their cathodes. In order to make LSBs commercially viable, an LSB’s separator must permit fast Li-ion diffusion while suppressing the migration of soluble lithium polysulfides (LiPSs). Polyolefin separators (commonly used in Li-ion batteries) fail to block LiPSs, have low thermal stability, poor mechanical strength, and weak electrolyte affinity. Novel nanofiber (NF) separators address the aforementioned shortcomings of polyolefin separators with intrinsically superior properties. Moreover, NF separators can easily be produced in large volumes, fine-tuned via facile electrospinning techniques, and modified with various additives. This review discusses the design principles and performance of LSBs with exemplary NF separators. The benefits of using various polymers and the effects of different polymer modifications are analyzed. We also discuss the conversion of polymer NFs into carbon NFs (CNFs) and their effects on rate capability and thermal stability. Finally, common and promising modifiers for NF separators, including carbon, metal oxide, and metal-organic framework (MOF), are examined. We highlight the underlying properties of the composite NF separators that enhance the capacity, cyclability, and resilience of LSBs.

In recent years, there has been a huge surge in interest in improving the efficiency of smart electronic and optoelectronic devices via the development of novel materials and printing technologies. Inkjet printing, known to deposit ‘ink on demand’, helps to reduce the consumption of materials. Printing inks on various substrates like paper, glass, and fabric is possible, generating flexible devices that include supercapacitors, sensors, and electrochromic devices. Newer inks being tested and used include formulations of carbon nanoparticles, photochromic dyes, conducting polymers, etc. Among the conducting polymers, PANI has been well researched. It can be synthesized and doped easily and allows for the easy formation of composite conductive inks. Doping and the addition of additives like metal salts, oxidants, and halide ions tune its electrical properties. PANI has a large specific capacitance and has been researched for its applications in supercapacitors. It has been used as a sensor for pH and humidity as well as a biosensor for sweat, blood, etc. The response is generated by a change in its electrical conductivity. This review paper presents an overview of the investigations on the formulation of the inks based on conductive polymers, mainly centered around PANI, and inkjet printing of its formulations for a variety of devices, including supercapacitors, sensors, electrochromic devices, and patterning on flexible substrates. It covers their performance characteristics and also presents a future perspective on inkjet printing technology for advanced electronic, optoelectronic, and other conductive-polymer-based devices. We believe this review provides a new direction for next-generation conductive-polymer-based devices for various applications.

Interest in carbon quantum dots (CQDs) has recently boomed due to their potential to enhance the performance of various solar technologies as nontoxic, naturally abundant, and cleanly produced nanomaterials. CQDs and their other variations, such as nitrogen-doped carbon quantum dots (NCQDs) and graphene quantum dots (GQDs), have improved the performance of luminescent solar concentrators (LSCs) and photovoltaic (PV) cells due to their excellent optical properties. As fluorophores in LSCs, CQDs are mostly transparent to visible light and have absorption/re-emission spectra that can be easily controlled. The outstanding optical properties of CQDs make them promising materials to replace expensive, heavy-metal-based fluorophores. Various CQDs have also been used as or doped into the photoanode, counter electrode, hole transport layer (HTL), and electron transport layer (ETL) of dye-sensitized solar cells (DSSCs), organic solar cells (OSC), perovskite solar cells (PSCs), and other PV cell configurations. The addition of CQDs into the various solar cell components has reduced electron recombination, increased charge density, and boosted electron mobility, improving the performance of the PV cells. Enhancing the power conversion efficiency (PCE) of photovoltaic devices is essential in propagating green energy technology. Thus, CQDs offer an affordable, safe, and environmentally friendly method to advance photovoltaic performance.

Starch [(CHO)]-stabilized bismuth sulfide (BiS) nanoparticles (NPs) were synthesized in a single-pot reaction using bismuth nitrate pentahydrate (Bi(NO)·5HO) and sodium sulfide (NaS) as precursors. BiSNPs were stable over time and a wide band gap of 2.86 eV was observed. The capping of starch on the BiSNPs prevents them from agglomeration and provides regular uniform shapes. The synthesized BiSNPs were quasispherical, and the measured average particle size was ?11 nm. The NPs are crystalline with an orthorhombic structure as determined by powder X-ray diffraction and transmission electron microscopy. The existence and interaction of starch on the NP's surface were analyzed using circular dichroism. Impedance spectroscopy was used to measure the electronic behavior of BiSNPs at various temperatures and frequencies. The dielectric measurements on the NPs show high dielectric polarizations. Furthermore, it was observed that the synthesized BiSNPs inhibited bacterial strains (Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) and demonstrated substantial antibacterial activity.

Despite the great advances in microsurgery, some neural injuries cannot be treated surgically. Stem cell therapy is a potential approach for treating neuroinjuries and neurodegenerative disease. Researchers have developed various bioactive scaffolds for tissue engineering, exhibiting enhanced cell viability, attachment, migration, neurite elongation, and neuronal differentiation, with the aim of developing functional tissue grafts that can be incorporated in vivo. Facilitating the appropriate interactions between the cells and extracellular matrix is crucial in scaffold design. Modification of scaffolds with biofunctional motifs such as growth factors, drugs, or peptides can improve this interaction. In this review, we focus on the laminin-derived Ile-Lys-Val-Ala-Val peptide as a biofunctional epitope for neuronal tissue engineering. Inclusion of this bioactive peptide within a scaffold is known to enhance cell adhesion as well as neuronal differentiation in both 2-dimensional and 3-dimensional environments. The in vivo application of this peptide is also briefly described.

Van der Waals (VDW) materials have shown unique electrical and optical properties depending on the thickness due to strong interlayer interaction and symmetry breaking at the monolayer level. In contrast, the study of electrical and tribological properties and their thickness-insensitivity of van der Waals oxides are lacking due to difficulties in the fabrication of high quality two-dimensional oxides and the investigation of nanoscale properties. Here we investigated various tribological and electrical properties, such as, friction, adhesion, work function, tunnel current, and dielectric constant, of the single-crystal ?-MoO nanosheets epitaxially grown on graphite by using atomic force microscopy. The friction of atomically smooth MoO is rapidly saturated within a few layers. The thickness insensitivity of friction is due to very weak mechanical interlayer interaction. Similarly, work function (4.73 eV for 2 layers (hereafter denoted as L)) and dielectric constant (6 for 2L and 10.5-11 for >3L) of MoO in MoO showed thickness insensitivity due to weak interlayer coupling. Tunnel current measurements by conductive atomic force microscopy showed that even 2L MoO of 1.4 nm is resistant to tunneling with a high dielectric strength of 14 MV/cm. The thickness-indifferent electrical properties of high dielectric constant and tunnel resistance by weak interlayer coupling and high crystallinity show a promise in the use of MoO nanosheets for nanodevice applications.

Currently, energy storage devices draw considerable attention owing to the growing need for clean energy. The depletion of fossil fuels and the generation of greenhouse gases have led to the development of alternative, environmentally friendly energy storage devices. Supercapacitors with high power densities are excellent devices for energy storage. Although carbon-based materials are widely used in such devices, their non-faradic behavior in electrical double layer capacitors (EDLCs) limits the maximum power density that can be generated. In contrast, the faradaic mechanism of transition metal hydroxides results in better capacitance rates along with good stability during cycling. This review is confined to nickel cobalt layered double hydroxides (NiCo LDHs) classified based on the fabrication of electrodes for application in supercapacitors. We discuss the growth of the active LDH material in situ or ex situ on the current collector and how the synthesis can affect the crystal structure as well as the electrochemical performance of the electrode.

Since the isolation of graphene, various two-dimensional (2D) materials have been extensively investigated. Nevertheless, only few 2D oxides have been reported to date due to difficulties in their synthesis. However, it is expected that the layered transition-metal oxides (TMOs) could be missing blocks for van der Waals heterostructures and essential elements for 2D electronics. Herein, the crystal structure and band structure of van der Waals epitaxially grown ?-MoO nanosheets on various 2D growth templates are characterized. Monolayer and multilayer ?-MoO nanosheets are successfully grown on a 2D substrate by simply evaporating amorphous molybdenum oxide thin film in ambient conditions. A single-crystal ?-MoO nanosheet without grain boundary is epitaxially grown on various 2D substrates despite a large lattice mismatch. During growth, the quasi-stable monolayer ?-MoO first covers the 2D substrate, then additional layers are continuously grown on the first monolayer ?-MoO. The band gap of the ?-MoO increases from 2.9 to 3.2 eV as the thickness decreases. Furthermore, due to oxygen vacancies and surface adsorbates, the synthesized ?-MoO is highly n-doped with a small work function. Therefore, ?-MoO field-effect transistors (FETs) exhibit a typical n-type conductance. This work shows the great potential of ultra-thin ?-MoO in 2D-material-based electronics.