Search

The synthesis of ordered gold‐copper (Au3Cu) alloy nanocrystals (≈10 nm) is reported and used in the semiconductor (2H) to metallic (1T) phase transformation of an atomically thin large‐area 2D‐MoS2 grown via CVD technique. The ordered Au3Cu nanocrystals are dispersed over 2D‐MoS2, and the phase transformation is confirmed via Raman spectroscopy followed by X‐ray photoelectron spectroscopy (XPS), while the surface properties of the Au3Cu/2D‐MoS2 is determined by the XPS valence band analysis and ultra‐violet photoemission spectroscopy (UPS). By comparing overpotential and Tafel slopes for Hydrogen Evolution Reaction (HER), a decrease is observed in overpotential by 83.2 mV and Tafel slope by ≈58.25 mV per decade for Au3Cu/MoS2 on light irradiation. This electrocatalytic enhancement of Au3Cu/MoS2 refers to the transformation of semiconducting 2D‐MoS2 to metallic phase under light illumination, thereby altering the surface electronic structures, improving carrier concentrations, lowering the valence band edge, and lowering the free energy of H* adsorption/desorption. Density functional theory (DFT) calculations, along with other surface characterizations, further illustrate that the ordered nanocrystal‐induced phase transformation in 2D‐MoS2 leads to a more durable metallic characteristic, thus, enhancing the surface electrical conductivity, reducing surface potential and Gibbs free energy, and improving the kinetics of photoelectrocatalytic performance of the hybrid structure. [ABSTRACT FROM AUTHOR]

Due to their excellent optoelectronic properties, two-dimensional nanomaterials are becoming key in developing various sensors for detecting harmful environmental pollutants. In this study, we present an approach for detecting methylene blue (MB) pollutants using a contactless optical sensor based on molybdenum disulfide (MoS2) nanostructures. Our approach involves exploiting the interaction between the optical absorption of MB and the excitons of MoS2, considered as markers, to monitor the presence of the MB contaminant at various concentrations. For this purpose, MoS2 nanostructures are deposited onto a quartz substrate via chemical vapor deposition, exhibiting exceptional crystalline quality and a triangular-like morphology. We demonstrate a high-sensitivity (with a limit of detection as low as 1 ng·L–1) dynamic response for the MoS2/quartz-based device in reflectivity measurements from MoS2 nanostructure excitons as a function of the MB concentration variation. Specifically, we show that the reflectivity intensity ratio at A and B exciton positions is directly related to the change in MB concentration in the analyte. Furthermore, the proposed sensor device features highly persistent reusability, owing to its contactless configuration with the MB pollutant, which preserves the MoS2 sensing layer from poisoning and/or alteration. Our findings provide valuable insights for potential developments aimed at achieving highly accurate and reliable next-generation optical sensors based on two-dimensional nanomaterials. [ABSTRACT FROM AUTHOR]

Monolayer Molybdenum Disulfide (MoS2) exhibits a direct bandgap characterized by strong visible photoluminescence, high on/off ratio, high optical transparency, low dissipation rate, and light absorption in a wide energy spectrum. The influence of different deposition voltages and durations on the optical and photoluminescent characteristics was investigated using Raman spectroscopy, UV–visible spectrophotometry, and photoluminescence spectroscopy. All samples were analyzed for optical properties to confirm their suitability for optoelectronics. The energy band gap and Urbach energy (band tail width) of all films were 1.87 to 2.52 eV and 0.31 to 0.49 eV, respectively. The findings reveal a correlation between enhanced absorption properties and a decrease in the bandgap of the semiconducting film layers, implying the potential utility of the deposited films as efficient solar absorbers. Furthermore, the improved transmittance observed within the visible wavelength range suggests their applicability as effective window layers in thin-film photodiodes. It was established that varying the voltage and time of deposition alone can enhance the optoelectronic performance of the material in any device.

Metal–organic chemical vapor deposition (MOCVD) is a key method for scalable synthesis of two-dimensional transition metal dichalcogenide (2D-TMDC) layers. However, it faces several challenges, such as the unintentional co-deposition of carbon impurities resulting from the pyrolysis of metal–organic precursors. This study investigates the chemical features of carbon and its impact on the photoluminescence property and air stability of 2D-MoS2. Using X-ray photoemission spectroscopy (XPS), it was found that the carbon impurities show characteristics similar to those of sp2-bonded graphitic carbon. Upon prolonged (20–40 weeks) exposure to the atmosphere, the incorporated carbon appears to react with 2D-MoS2, forming a MoS2−xCx solid solution. At the same time, a gradual decrease in the S/Mo ratio implies the formation of sulfur vacancies was also observed. These two processes lead to crystal degradation over time, as evidenced by the gradual quenching of the Raman and photoluminescence (PL) peaks. More detailed PL analyses suggest a charge transfer mechanism between sp2-carbon/2D-MoS2 and 2D-MoS2/air-adsorbates, which, in the short term, could alter PL emissions and appear to further intensify the degradation of 2D-MoS2 in the long-term. The findings highlight the strong impact of unintentionally co-deposited carbon on the optical properties and air stability of MOCVD 2D-MoS2 layers. [ABSTRACT FROM AUTHOR]

Metal–organic chemical vapor deposition (MOCVD) is a key method for scalable synthesis of two-dimensional transition metal dichalcogenide (2D-TMDC) layers. However, it faces several challenges, such as the unintentional co-deposition of carbon impurities resulting from the pyrolysis of metal–organic precursors. This study investigates the chemical features of carbon and its impact on the photoluminescence property and air stability of 2D-MoS2. Using X-ray photoemission spectroscopy (XPS), it was found that the carbon impurities show characteristics similar to those of sp2-bonded graphitic carbon. Upon prolonged (20–40 weeks) exposure to the atmosphere, the incorporated carbon appears to react with 2D-MoS2, forming a MoS2−xCx solid solution. At the same time, a gradual decrease in the S/Mo ratio implies the formation of sulfur vacancies was also observed. These two processes lead to crystal degradation over time, as evidenced by the gradual quenching of the Raman and photoluminescence (PL) peaks. More detailed PL analyses suggest a charge transfer mechanism between sp2-carbon/2D-MoS2 and 2D-MoS2/air-adsorbates, which, in the short term, could alter PL emissions and appear to further intensify the degradation of 2D-MoS2 in the long-term. The findings highlight the strong impact of unintentionally co-deposited carbon on the optical properties and air stability of MOCVD 2D-MoS2 layers.

In this research paper, we have prepared thin film of MoS2 by thermal evaporation technique and characterized it. This thin film depositions lead to amorphous thin film. To make it crystalline, thermal annealing of the film have deposited on the substrates at 800 o C for two hour under vacuum environment. X-ray diffraction data of thin film shows the poly-crystalline nature. The Atomic Force Microscopy (AFM) image of the thin film shows the crystallinity with regularly arranged grains. Furthermore, an unconventional MoS2 based FET device has been fabricated by depositing thin film of MoS2 on p-type silicon. Thereafter, its transfer and output characteristics have been studied. The results show n-type semiconductor behaviour with an on/off ratio of about 103 and field-effect mobility of ~0.015 cm2/V. s at VDS of 1 V. [ABSTRACT FROM AUTHOR]

The pursuit of environmentally friendly solvents has become an essential research topic in sustainable chemistry and nanomaterial science. With the need to substitute toxic solvents in nanofabrication processes becoming more pressing, the search for alternative solvents has taken on a crucial role in this field. Additionally, the use of toxic, non-economical organic solvents, such as N-methyl-2 pyrrolidone and dimethylformamide, is not suitable for all biomedical applications, even though these solvents are often considered as the best exfoliating agents for nanomaterial fabrication. In this context, the success of producing two-dimensional transition metal dichalcogenides (2D TMDs), such as MoS2 and WS2, with excellent captivating properties is due to the ease of synthesis based on environment-friendly, benign methods with fewer toxic chemicals involved. Herein, we report for the first time on the use of cyrene as an exfoliating agent to fabricate monolayer and few-layered 2D TMDs with a versatile, less time-consuming liquid-phase exfoliation technique. This bio-derived, aprotic, green and eco-friendly solvent produced a stable, surfactant-free, concentrated 2D TMD dispersion with very interesting features, as characterized by UV–visible and Raman spectroscopies. The surface charge and morphology of the fabricated nanoflakes were analyzed using ς-potential and scanning electron microscopy. The study demonstrates that cyrene is a promising green solvent for the exfoliation of 2D TMD nanosheets with potential advantages over traditional organic solvents. The ability to produce smaller-sized—especially in the case of WS2 as compared to MoS2—and mono/few-layered nanostructures with higher negative surface charge values makes cyrene a promising candidate for various biomedical and electronic applications. Overall, the study contributes to the development of sustainable and environmentally friendly methods for the production of 2D nanomaterials for various applications. [ABSTRACT FROM AUTHOR]

A First-principles study was accomplish to examine the various characteristics of 2-D hetero-junction layer structure Molybdenum disulfide (MoS2) material such as structural, electronic, and optical properties through variation of external static pressure 0–100 GPa with a 4-steps escalations such as 0, 50, 75 100 GPa. Scheming bandgap tuning by the external static pressure engineering of 2-D layered MoS2 is a relatively new approach for tailoring different properties. The bandgap of MoS2 is found to be decreasing from 1.65 to 0.0 eV with increased external static pressure from 0 to 100 GPa. By increasing the external static pressure in MoS2 extra gamma states are produced into an energy band gap (Eg). The bandgap nature originated indirect moreover bandgap represented that material is an eminent semiconductor. MoS2 is a proficient photo-catalysis have a large surface area for light absorption and decreases the electron–hole pairs recombination rate and increases the charge transport. A significant decrement is found in the reflectivity due to the decrement in the bandgap. It is also examined that increment in energy adsorption peaks at 0 to 35 eV furthermore optical conductivity peaks shifts at larger energy band through increment the static pressure engineering. The optical properties significantly increased by the decrement of Eg. MoS2 has high energy absorption, optical conductivity, and refractive index and is an appropriate material for photocatalytic applications. [ABSTRACT FROM AUTHOR]

Plasmonic nanocrystals (NCs) assisted phase transition of two-dimensional molybdenum disulfide (2D-MoS2) unlashes numerous opportunities in the fields of energy harvesting via electrocatalysis and photoelectrocatalysis by enhancing electronic conductivity, increasing catalytic active sites, lowering Gibbs free energy for hydrogen adsorption and desorption, etc. Here, we report the synthesis of faceted gold pentagonal bi-pyramidal (Au-PBP) nanocrystals (NC) for efficient plasmon-induced phase transition (from 2 H to 1 T phase) in chemical vapor deposited 2D-MoS2. The as-developed Au-PBP NC with the increased number of corners and edges showed an enhanced multi-modal plasmonic effect under light irradiations. The overpotential of hydrogen evolution reaction (HER) was reduced by 61 mV, whereas the Tafel slope decreased by 23.7 mV/dec on photoexcitation of the Au-PBP@MoS2 hybrid catalyst. The enhanced performance can be attributed to the light-induced 2H to 1 T phase transition of 2D-MoS2, increased active sites, reduced Gibbs free energy, efficient charge separation, change in surface potential, and improved electrical conductivity of 2D-MoS2 film. From density functional theory (DFT) calculations, we obtain a significant change in the electronic properties of 2D-MoS2 (i.e. work function, surface chemical potential, and the density of states), which was primarily due to the plasmonic interactions and exchange-interactions between the Au-PBP nanocrystals and monolayer 2D-MoS2, thereby enhancing the phase transition and improving the surface properties. This work would lay out finding assorted routes to explore more complex nanocrystals-based multipolar plasmonic NC to escalate the HER activity of 2D-MoS2 and other 2D transition metal dichalcogenides. [ABSTRACT FROM AUTHOR]

Simple hydrothermal process was used to successfully produce two-dimensional (2D) MoS2 powder flower-like nanosheets. The structure of the end product 2D-MoS2 is altered by changing the preparation conditions of reaction time and pH value with a constant autoclave temperature. Via annealing at 500°C, all samples transfer into 2H-MoS2 instead of 1T-MoS2. X-ray diffraction patterns showed that the peaks along (002) planes shifted dramatically from 14.2° to 9.4°. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images revealed that the prepared samples have a flower-like structure composed of spheres of nanosheets with a good polycrystalline structure. The energy gap for pristine and annealed samples is calculated from diffuse reflectance measurements and found to be 1.3 and 0.68 eV, respectively. Differential scanning calorimeter curves showed an impressive exothermic peak at 318°C, suggesting a structural to the stable 2H-MoS2 phase. The Brunauer–Emmett–Teller technique showed rapid decreases in the samples surface area at nearly 48 m2 g–1 with the structural transformation. [ABSTRACT FROM AUTHOR]

Host‐guest interactions are of paramount importance in supramolecular chemistry and in a wide range of applications. Particularly well known is the ability of cucurbit[n]urils (CB[n]) to selectively host small molecules. We show that the charge transfer and complexation capabilities of CB[n] are retained on the surface of 2D transition metal dichalcogenides (TMDs), allowing the development of efficient electrochemical sensing platforms. We unveil the mechanisms of host‐guest recognition between the MoS2‐CB[8] hybrid interface and melatonin (MLT), an important molecular regulator of vital constants in vertebrates. We find that CB[8] on MoS2 organizes the receptor portals perpendicularly to the surface, facilitating MLT complexation. This advantageous adsorption geometry is specific to TMDs and favours MLT electro‐oxidation, as opposed to other 2D platforms like graphene, where one receptor portal is closed. This study rationalises the cooperative interaction in 2D hybrid systems to improve the efficiency and selectivity of electrochemical sensing platforms. [ABSTRACT FROM AUTHOR]

Numerous structural defects, such as vacancies, dislocations, admixtures, grain boundaries and edges in the 2 D-MoS2 particles change their optical, mechanical, and electrical properties that influences their application. Here we investigate the heat annealing of MoS2 particles at 700 °C in an argon atmosphere, and demonstrate the appearance of sulfur vacancies in them using FTIR spectroscopy. The new IR absorption bands belonging to deformation and stretching vibrations of S O 4 2 − anions centered at 614 cm−1 and 1115 cm−1, respectively, were registered after annealing. In both MoS2 samples, those before and after the heat annealing, the Mo-Ox vibrations were registered by FTIR and Raman spectroscopy. Negligible changes observed in the Raman spectra of the title compound are discussed. [ABSTRACT FROM AUTHOR]

The pursuit of environmentally friendly solvents has become an essential research topic in sustainable chemistry and nanomaterial science. With the need to substitute toxic solvents in nanofabrication processes becoming more pressing, the search for alternative solvents has taken on a crucial role in this field. Additionally, the use of toxic, non-economical organic solvents, such as N-methyl-2 pyrrolidone and dimethylformamide, is not suitable for all biomedical applications, even though these solvents are often considered as the best exfoliating agents for nanomaterial fabrication. In this context, the success of producing two-dimensional transition metal dichalcogenides (2D TMDs), such as MoS2 and WS2, with excellent captivating properties is due to the ease of synthesis based on environment-friendly, benign methods with fewer toxic chemicals involved. Herein, we report for the first time on the use of cyrene as an exfoliating agent to fabricate monolayer and few-layered 2D TMDs with a versatile, less time-consuming liquid-phase exfoliation technique. This bio-derived, aprotic, green and eco-friendly solvent produced a stable, surfactant-free, concentrated 2D TMD dispersion with very interesting features, as characterized by UV–visible and Raman spectroscopies. The surface charge and morphology of the fabricated nanoflakes were analyzed using ς-potential and scanning electron microscopy. The study demonstrates that cyrene is a promising green solvent for the exfoliation of 2D TMD nanosheets with potential advantages over traditional organic solvents. The ability to produce smaller-sized—especially in the case of WS2 as compared to MoS2—and mono/few-layered nanostructures with higher negative surface charge values makes cyrene a promising candidate for various biomedical and electronic applications. Overall, the study contributes to the development of sustainable and environmentally friendly methods for the production of 2D nanomaterials for various applications.

• Monolayer MoS 2 thin films are electrosynthesized and optimized. • Some surface structural characterizations of the films are studied. • Optical properties of monolayer MoS 2 are investigated as a function of varying deposition conditions. • The study unveiled the optoelectronic potentials of electrodeposited MoS 2 and its modulations by simple adjustments in some deposition conditions. Monolayer Molybdenum Disulfide (MoS 2) exhibits a direct bandgap characterized by strong visible photoluminescence, high on/off ratio, high optical transparency, low dissipation rate, and light absorption in a wide energy spectrum. The influence of different deposition voltages and durations on the optical and photoluminescent characteristics was investigated using Raman spectroscopy, UV–visible spectrophotometry, and photoluminescence spectroscopy. All samples were analyzed for optical properties to confirm their suitability for optoelectronics. The energy band gap and Urbach energy (band tail width) of all films were 1.87 to 2.52 eV and 0.31 to 0.49 eV, respectively. The findings reveal a correlation between enhanced absorption properties and a decrease in the bandgap of the semiconducting film layers, implying the potential utility of the deposited films as efficient solar absorbers. Furthermore, the improved transmittance observed within the visible wavelength range suggests their applicability as effective window layers in thin-film photodiodes. It was established that varying the voltage and time of deposition alone can enhance the optoelectronic performance of the material in any device. [ABSTRACT FROM AUTHOR]

The surface functionalization of nanomaterial is relevant in terms of its selectivity toward a bacterial strain. Recently, semiconducting nanomaterials have been gaining much attention in the development of nanomaterial-based alternative antibiotics. Among the various semiconducting materials, molybdenum disulfide (MoS2) has been gaining considerable interest due to its unique electronic, physical, and chemical properties. The semiconducting nature, high colloidal stability, and biocompatibility make it a promising candidate in the field of biomedical research. The development of antibacterial material based on MoS2 quantum dots is still in its infancy. Here, we have explored the effect of hydrophobic amino acid-modified MoS2 quantum dots toward their antibacterial activity. Functionalization enhances the antibacterial activity and selectivity depending on the amino acid residue. MoS2 quantum dots with a leucine-functionalized ligand show selective antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), whereas MoS2 quantum dots with a phenylalanine-functionalized ligand show almost equal antibacterial efficacy against both MRSA and Pseudomonas aeruginosa (PA). [ABSTRACT FROM AUTHOR]

Protein N-glycosylation plays crucial roles in many biological processes and has close association with the occurrence and development of various cancers. Therefore, it is necessary to analyze the abnormal changes of N-glycopeptides in complex biological samples for biomarker discovery. However, due to their low abundance and poor ionization, N-glycopeptides identification in complex samples by mass spectrometry (MS) is still a challenging task. In this work, a novel magnetic hydrophilic material was prepared by serial functionalization of ultra-thin two-dimensional molybdenum disulfide with Fe 3 O 4 nanoparticles, gold nanowire and glutathione (MoS 2 –Fe 3 O 4 –Au/NWs-GSH) for efficient N-glycopeptides enrichment. The advantage of using the new nanocomposite is threefold. First, the introduction of magnetic Fe 3 O 4 nanoparticles efficiently simplifies the enrichment process. Second, the gold nanowire modification enlarges the surface area of the nanocomposites to facilitate interaction with N-glycopeptides. Third, the employment of highly hydrophilic glutathione leads to specific HILIC-based retention of N-glycopeptides. Low femtomolar detection sensitivity and 1:1000 enrichment selectivity can be achieved using MoS 2 –Fe 3 O 4 –Au/NWs-GSH enrichment and bio-mass spectrometry analysis. Successful applications in human urine exosome and serum proteins were demonstrated by the enrichment and identification of 1250 and 489 N-glycopeptides, respectively. This remarkable data set of N-glycoproteome indicates the application potential of the novel nanocomposites for N-glycopeptides enrichment in complex biological samples and for related glycoproteome studies. Image 1 • A novel magnetic hydrophilic material (MoS 2 -Fe 3 O 4 -Au/NWs-GSH) was prepared for N-glycopeptides enrichment. • MoS 2 –Fe 3 O 4 –Au/NWs-GSH has high hydrophilicity, large specific surface area and superparamagnetism. • Low femtomolar identification sensitivity and 1:1000 enrichment selectivity can be achieved using MoS 2 –Fe 3 O 4 –Au/NWs-GSH. • 1250 N-glycopeptides and 489 N-glycopeptides were enriched and identified from human urine exosome and serum. [ABSTRACT FROM AUTHOR]

In the surge of recent successes of 2D materials following the rise of graphene, molybdenum disulfide (2D-MoS2) has been attracting growing attention from both fundamental and applications viewpoints, owing to the combination of its unique nanoscale properties. For instance, the bandgap of 2D-MoS2, which changes from direct (in the bulk form) to indirect for ultrathin films (few layers), offers new prospects for various applications in optoelectronics. In this review, we present the latest scientific advances in the field of synthesis and characterization of 2D-MoS2 films while highlighting some of their applications in energy harvesting, gas sensing, and plasmonic devices. A survey of the physical and chemical processing routes of 2D-MoS2 is presented first, followed by a detailed description and listing of the most relevant characterization techniques used to study the MoS2 nanomaterial as well as theoretical simulations of its interesting optical properties. Finally, the challenges related to the synthesis of high quality and fairly controllable MoS2 thin films are discussed along with their integration into novel functional devices.

Organic-inorganic perovskite solar cells (PrSCs) have emerged as a promising solar photovoltaic technology in terms of realizing high power conversion efficiency (PCE). However, their limited lifetime and poor device stability limit their commercialization in future. In this regard, interface engineering of the electron transport layer (ETL) using 2D materials have been currently used owing to their high carrier mobility, high thermal stability and tunable work function which in turn enormously impact the charge carrier dynamics. In this work, we report an easy and effective way of simultaneously enhancing the efficiency and air-stability of PrSCs via interface engineering by incorporating 2D-MoS 2 (bi/tri-layered) in mesoporous-titanium dioxide (mp -TiO 2) scaffold electron transport buffer layer, and using CVD grown perovskite layers. The PrSCs were fabricated in ambient air conditions in device configuration, FTO/c-TiO 2 / mp -TiO 2 :2D-MoS 2 /CH 3 NH 3 PbI 3 /P3HT/Au, with an active area of 0.16 cm2. The best device using c -TiO 2 / mp -TiO 2 :2D-MoS 2 (0.5 wt%) ETL exhibited a substantial increase in PCE ∼13.04% as compared to PCE ∼8.75% realized in reference device fabricated without incorporating MoS 2 in mp -TiO 2 buffer layer. The incorporation of MoS 2 nanoflakes in mp -TiO 2 ETL not only enhances the PCE to ∼49%, but also improve the lifetime (retaining PCE ∼86% of its initial value up to 500 hrs, without encapsulation). The enhancement in performance of c -TiO 2 / mp -TiO 2 :2D-MoS 2 ETL based devices as compared with reference c -TiO 2 / mp -TiO 2 ETL based devices is attributed to, (i) reduction in the work function of mp -TiO 2 ETL buffer on dispersion of 2D-MoS 2 nanoflakes forming of a perfect interface at ETL/perovskite offering extremely less interfacial energy barrier to promote the charge extraction process at the interface, and suppress the surface recombination losses, (ii) fast charge collection as 2D-MoS 2 in TiO 2 strongly support the electron transport due to their highly crystalline nature, and (iii) lifetime improvement due to better moisture stability of 2D-MoS 2 and high quality of chemical vapor grown perovskite thin films. This work presents an efficient mp -TiO 2 :2D-MoS 2 scaffold ETL for realizing high performance, low cost, air-processed PrSCs for their future development. [Display omitted] • CH 3 NH 3 PbI 3 perovskite film was deposited by CVD in perovskite solar cells. • [ mp -TiO 2 :2D-MoS 2 ] buffer layer improved the performance. • Addition of 2D-MoS 2 in mp -TiO 2 suppress interface traps, promote charge extraction, and transport. • 2D-MoS 2 also improves the operational stability of the devices. [ABSTRACT FROM AUTHOR]

The electronics industry is beginning to show interest in 2D molybdenum disulfide (2D-MoS2) as a potential device material due to its low band gap and high mobility. However, current methods for its synthesis are not 'fab' friendly and require harsh environments and processes. Here, a novel method to prepare MoS2 nanowire arrays and layered structures via self-assembly of a block copolymer system is reported. Well-controlled films of microphase separated line-space nanopatterns have been achieved by solvent annealing process. The self-assembled films are used as 'templates' for the generation of nonstoichometric molybdenum oxide by in situ inclusion technique following UV/Ozone treatment. Well-ordered array of MoS2 and a layered structure are then prepared by chemical vapor deposition using sulfur powder at lower temperature. The surface morphology, crystal structure, and phases are examined by different microscopic and spectroscopic techniques. This strategy can be extended to several other 2D materials systems and open the pathway toward better optoelectronic and nanoelectromechanical systems. [ABSTRACT FROM AUTHOR]

Host-guest interactions are of paramount importance in supramolecular chemistry and in a wide range of applications. Particularly well known is the ability of cucurbit[n]urils (CB[n]) to selectively host small molecules. We show that the charge transfer and complexation capabilities of CB[n] are retained on the surface of 2D transition metal dichalcogenides (TMDs), allowing the development of efficient electrochemical sensing platforms. We unveil the mechanisms of host-guest recognition between the MoS 2 -CB[8] hybrid interface and melatonin (MLT), an important molecular regulator of vital constants in vertebrates. We find that CB[8] on MoS 2 organizes the receptor portals perpendicularly to the surface, facilitating MLT complexation. This advantageous adsorption geometry is specific to TMDs and favours MLT electro-oxidation, as opposed to other 2D platforms like graphene, where one receptor portal is closed. This study rationalises the cooperative interaction in 2D hybrid systems to improve the efficiency and selectivity of electrochemical sensing platforms., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Plasmonic nanocrystals (NCs) assisted phase transition of two-dimensional molybdenum disulfide (2D-MoS 2 ) unlashes numerous opportunities in the fields of energy harvesting via electrocatalysis and photoelectrocatalysis by enhancing electronic conductivity, increasing catalytic active sites, lowering Gibbs free energy for hydrogen adsorption and desorption, etc. Here, we report the synthesis of faceted gold pentagonal bi-pyramidal (Au-PBP) nanocrystals (NC) for efficient plasmon-induced phase transition (from 2 H to 1 T phase) in chemical vapor deposited 2D-MoS 2 . The as-developed Au-PBP NC with the increased number of corners and edges showed an enhanced multi-modal plasmonic effect under light irradiations. The overpotential of hydrogen evolution reaction (HER) was reduced by 61 mV, whereas the Tafel slope decreased by 23.7 mV/dec on photoexcitation of the Au-PBP@MoS 2 hybrid catalyst. The enhanced performance can be attributed to the light-induced 2H to 1 T phase transition of 2D-MoS 2 , increased active sites, reduced Gibbs free energy, efficient charge separation, change in surface potential, and improved electrical conductivity of 2D-MoS 2 film. From density functional theory (DFT) calculations, we obtain a significant change in the electronic properties of 2D-MoS 2 (i.e. work function, surface chemical potential, and the density of states), which was primarily due to the plasmonic interactions and exchange-interactions between the Au-PBP nanocrystals and monolayer 2D-MoS 2 , thereby enhancing the phase transition and improving the surface properties. This work would lay out finding assorted routes to explore more complex nanocrystals-based multipolar plasmonic NC to escalate the HER activity of 2D-MoS 2 and other 2D transition metal dichalcogenides., (© 2023 IOP Publishing Ltd.)

Two-dimensional (2D) dilute magnetic semiconductors (DMSs) are attractive material platforms for applications in multifunctional nanospintronics due to the prospect of embedding controllable magnetic order within nanoscale semiconductors. Identifying candidate host material and dopant systems requires consideration of doping formation energies, magnetic ordering, and the tendency for dopants to form clustered domains. In this work, we consider the defect thermodynamics and the dilute magnetic properties across charge states of 2D-MoS 2 and 2D-WS 2 with Mn magnetic dopants as candidate systems for 2D-DMSs. Using hybrid density functional calculations, we study the magnetic and electronic properties of these systems across configurations with thermodynamically favorable defects: 2D-MoS 2 doped with Mn atoms at sulfur site (Mn S ), at two Mo sites (2Mn Mo ), on top of a Mo atom (Mn-top), and at a Mo site (Mn Mo ). While the majority of the Mn-defect complexes provide trap states, Mn Mo and Mn W are amphoteric, although previously predicted to be donor defects. The impact of cluster formation of these amphoteric defects on magnetic ordering is also considered; both Mn Mo -Mn Mo (2Mn 2Mo ) and Mn W -Mn W (2Mn 2W ) clusters are found to be stable in ferromagnetic (FM) ordering. Interestingly, we observed the defect charge state dependent magnetic behavior of 2Mn 2Mo and 2Mn 2W clusters in 2D-TMDs. We investigate that the FM coupling of 2Mn 2Mo and 2Mn 2W clusters is stable in only a neutral charge state; however, the antiferromagnetic (AFM) coupling is stable in the +1 charge state. 2Mn 2Mo clusters provide shallow donor levels in AFM coupling and deep donor levels in FM coupling. 2Mn 2W clusters lead to trap states in the FM and AFM coupling. We demonstrate the AFM to FM phase transition at a critical electron density n c e = 3.5 × 10 13 cm -2 in 2D-MoS 2 and 2D-WS 2 . At a 1.85% concentration of Mn, we calculate the Curie temperature of 580 K in the mean-field approximation.

[Display omitted] • Controlled growth of 2D-MoS 2 thin films achieved from carboxylated MoS 2. • Amino tagged poly(Thymine) shows potential affinity for Hg(II) ions. • T-Hg(II)-T hybridised MoS 2 offers strong coordination for Hg(II) sensor. • 10 fM of Hg(II) concentration could be detected in aqueous medium. 2D-Molybdenum disulfide (MoS 2) is a transition metal dichalcogenide with unique conducting and optoelectronic properties. This paper proposes a novel facile method to grow 2D (MoS 2) thin films by carboxylation of (MoS 2) nanoflakes using electrochemical deposition technique. The growth of the films was confirmed by atomic force microscopy. Further, an electrochemical Hg(II) ion biosensor was developed using as-grown (MoS 2) nanosheets functionalized with single-stranded deoxyribonucleic acid (ssDNA). The label-free electrochemical biosensor offered an excellent detection limit in the range of 10 fM to 10 nM of mercury concentrations. The selectivity measurements and environmental sample studies further revealed their superior applicability in environmental monitoring purposes. [ABSTRACT FROM AUTHOR]

In the surge of recent successes of 2D materials following the rise of graphene, molybdenum disulfide (2D-MoS2) has been attracting growing attention from both fundamental and applications viewpoints, owing to the combination of its unique nanoscale properties. For instance, the bandgap of 2D-MoS2, which changes from direct (in the bulk form) to indirect for ultrathin films (few layers), offers new prospects for various applications in optoelectronics. In this review, we present the latest scientific advances in the field of synthesis and characterization of 2D-MoS2 films while highlighting some of their applications in energy harvesting, gas sensing, and plasmonic devices. A survey of the physical and chemical processing routes of 2D-MoS2 is presented first, followed by a detailed description and listing of the most relevant characterization techniques used to study the MoS2 nanomaterial as well as theoretical simulations of its interesting optical properties. Finally, the challenges related to the synthesis of high quality and fairly controllable MoS2 thin films are discussed along with their integration into novel functional devices. [ABSTRACT FROM AUTHOR]

Solution-processed photovoltaics employing perovskite as light harvester are the next generation future energy source owing to its low manufacturing cost and potential to achieve high power conversion efficiency. Significant emphasis has been laid on the performance-related investigations, however the long-term instability under operational conditions and device reproducibility obstruct its potential commercial endeavour. Herein, by tweaking the energy level alignment between the hole-transport layer and perovskite, by the placement of a 2D-MoS 2 interlayer, we demonstrate suppressed interfacial charge accumulation, fast charge extraction, and subsequently improved photovoltaic performances. Notably, with the usage of a dopant free hole transport materials, a power conversion efficiency of 18.54% with significantly upgraded open circuit voltage (V oc) and FF was recorded. The stability measurement shows that the resulting 2D-MoS 2 supported dopant-free hole selective layers exhibit notable moisture stability under ambient conditions. Our study put forward the profound experimental understanding of 2D-transition metal dichalcogenides as an agent to engineering the interface, enlightening the power conversion efficiency and lifetime of the perovskite solar cells. Image 1 • Interface engineering by placing 2D-MoS 2 in perovskite solar cell. • Dopant free polymeric hole transport gave unparalleled performance. • Generic route that can be applied to increase performance and stability. • Reduced trap density and minimized interfacial losses by placement of 2D dichalcogenide material. • Interfacial layer reduces the energy required for detrapping the trapped-charges, providing prompt extraction of photo-generated charges. [ABSTRACT FROM AUTHOR]

Conductive polymers have an important potential against the corrosion applications because they are highly resistant to chemicals besides they have homogeneous coating properties and transport metals to more noble regions. However, the major disadvantage of conductive polymers such as polypyrrole (PPy) is their low mechanical strength. In this study, the doping effect of MoS 2 into the PPy coatings by the electropolymerization of polypyrrole (PPy) and exfoliated MoS 2 on the corrosion of brass was investigated. The corrosion protection of these coatings were determined by measuring the corrosion rates with Tafel polarization method in 0.1 M H 2 SO 4 media. PPy and MoS 2 doped PPy (MoS 2 @PPy) coatings were successfully obtained by the use of chronoamperometry technique in 0.2 M H 2 C 2 O 4 solutions with 0.2 M pyrrole and various concentrations of MoS 2. It was observed that MoS 2 @PPy coatings were homogeneously coated without and with all MoS 2 concentrations on the metal surface and well adhered to the brass surface, but MoS 2 @PPy coating with 25 ppm MoS 2 showed the best corrosion protection. The surface and chemical characterizations of the coatings were performed by SEM-EDS. • MoS2@PPy coatings were homogeneously coated on the metal surface and well adhered to the brass surface. • PPy coating has been reducing the corrosion current of brass in sulfuric acid. • MoS2@PPy coating with 25 ppm MoS2 showed the best corrosion protection. • Corrosion parameters obtained by Tafel polarization curves. [ABSTRACT FROM AUTHOR]

Generation of current or potential at nanostructures using appropriate stimuli is one of the futuristic methods of energy generation. We developed an ambient soft ionization method for mass spectrometry using 2D-MoS 2 , termed streaming ionization, which eliminates the use of traditional energy sources needed for ion formation. The ionic dissociation-induced electrokinetic effect at the liquid-solid interface is the reason for energy generation. We report the highest figure of merit of current generation of 1.3 A/m 2 by flowing protic solvents at 22 μL/min over a 1 × 1 mm 2 surface coated with 2D-MoS 2 , which is adequate to produce continuous ionization of an array of analytes, making mass spectrometry possible. Weakly bound ion clusters and uric acid in urine have been detected. Further, the methodology was used as a self-energized breath alcohol sensor capable of detecting 3% alcohol in the breath.

Optoelectronic-neuromorphic transistors are vital for next-generation nanoscale brain-like computational systems. However, the hardware implementation of optoelectronic-neuromorphic devices, which are based on conventional transistor architecture, faces serious challenges with respect to the synchronous processing of photoelectric information. This is because mono-semiconductor material cannot absorb adequate light to ensure efficient light-matter interactions. In this work, a novel neuromorphic-photoelectric device of vertical van der Waals heterojunction phototransistors based on a colloidal 0D-CsPbBr 3 -quantum-dots/2D-MoS 2 heterojunction channel is proposed using a polymer ion gel electrolyte as the gate dielectric. A highly efficient photocarrier transport interface is established by introducing colloidal perovskite quantum dots with excellent light absorption capabilities on the 2D-layered MoS 2 semiconductor with strong carrier transport abilities. The device exhibits not only high photoresponsivity but also fundamental synaptic characteristics, such as excitatory postsynaptic current, paired-pulse facilitation, dynamic temporal filter, and light-tunable synaptic plasticity. More importantly, efficiency-adjustable photoelectronic Pavlovian conditioning and photoelectronic hybrid neuronal coding behaviors can be successfully implemented using the optical and electrical synergy approach. The results suggest that the proposed device has potential for applications associated with next-generation brain-like photoelectronic human-computer interactions and cognitive systems., (© 2020 Wiley-VCH GmbH.)