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We report a two-step growth process of MoS2 nanoflakes using a low-pressure chemical vapor deposition technique. In the first step, a MoS2 layer was synthesized on a c-plane sapphire substrate. This layer was subsequently re-evaporated at a higher temperature to form mono- or few-layer MoS2 flakes. As a result, the close proximity re-evaporation enabled the growth of pristine MoS2 nanoflakes. Atomic force microscopy analysis confirmed the synthesis of nanoclusters/nanoflakes with lateral dimensions of over 10 μm and a flake height of approximately 1.3 nm, demonstrating bi-layer MoS2, whereas transmission electron microscopy analysis revealed triangular MoS2 nanoflakes, with a diffraction pattern proving the presence of single crystalline hexagonal MoS2. Raman data revealed the typical modes of high-quality MoS2 nanoflakes. Finally, we presented the photocurrent dependence of a MoS2-based photoresist under illumination with light-emitting diode of 405 nm wavelength. The measured current–voltage dependence across various luminous flux outlined the sensitivity of MoS2 to polarized light and thus opens further opportunities for applications in high-performance photodetectors with polarization sensitivity. [ABSTRACT FROM AUTHOR]

With the help of a hydrothermal process, we were able to prepare vertically layered MoS2 nanoflakes that were rooted to TiO2 modified. MoS2 nanoflakes and TiO2 contribute significantly to the strong XRD peaks and μ-Raman spectroscopy, and this phenomenon may also be explained by the unique structure of vertically stacked MoS2 nanoflakes on TiO2 that has many exposed edges and large surfaces as well as high electron transfer rates between TiO2 and MoS2. As can be clearly seen, there are no noticeable changes in the self-photodegradation of MB under visible light interaction (VLI), and the MoS2 doped TiO2 photocatalyst displays ∼ 90 % degradation efficiency. By, measuring photoelectrochemically, charge carriers are separated efficiently. These experiments illustrate the transient photocurrent response of the MoS2 doped TiO2 photocatalyst while cycling between three on/off cycles. As a result of a low recombination rate of the photoexcited charge carriers, the MoS2 doped TiO2 photocatalyst displays superior photocurrent response. In other words, a lower charge transfer resistance results in a faster transfer of charge between the surfaces.

We report a two-step growth process of MoS2 nanoflakes using a low-pressure chemical vapor deposition technique. In the first step, a MoS2 layer was synthesized on a c-plane sapphire substrate. This layer was subsequently re-evaporated at a higher temperature to form mono- or few-layer MoS2 flakes. As a result, the close proximity re-evaporation enabled the growth of pristine MoS2 nanoflakes. Atomic force microscopy analysis confirmed the synthesis of nanoclusters/nanoflakes with lateral dimensions of over 10 μm and a flake height of approximately 1.3 nm, demonstrating bi-layer MoS2, whereas transmission electron microscopy analysis revealed triangular MoS2 nanoflakes, with a diffraction pattern proving the presence of single crystalline hexagonal MoS2. Raman data revealed the typical modes of high-quality MoS2 nanoflakes. Finally, we presented the photocurrent dependence of a MoS2-based photoresist under illumination with light-emitting diode of 405 nm wavelength. The measured current–voltage dependence across various luminous flux outlined the sensitivity of MoS2 to polarized light and thus opens further opportunities for applications in high-performance photodetectors with polarization sensitivity.

MoS2 nanoflakes, though with graphene-like morphology, exhibit unsatisfactory performance in the fabrication of electrochemical sensors due to the poor conductivity. Herein, MoS2 nanoflakes were electrochemically modulated, while gold nanoparticles (AuNPs) were co-electrodeposited by one-step cyclic voltammetry, forming a nanocomposite on the electrode surface. During the CV treatment, MoS2 nanoflakes could be easily transformed from the original 2H phase with semiconductor properties to 1T phase with metal properties. The good electrical conductivity and also the big specific area of the ultimate AuNPs/1T-MoS2 composite can be reflected by the CV and electrochemical impedance spectroscopy characterization. The nanocomposite exhibited attractive catalytic capacity to the electrochemical redox of dopamine (DA). Therefore, a DA sensor based on AuNPs/1T-MoS2 was constructed. Using the detection technique of amperometry, the sensor displayed a wide linear range from 0.2 μmol/L to 1.0 mmol/L with low detection limit of 0.15 μmol/L. Using the detection technique of differential pulse voltammetry, the sensor demonstrated excellent selectivity when was applied in the sample containing excessive amount of ascorbic acid. Furthermore, the sensor could be used to detect dopamine in serum with a recovery rate of 106.5-109.4%. [ABSTRACT FROM AUTHOR]

Herein, field‐effect transistors (FET) based on multilayer molybdenum disulfide (MoS2) nanoflakes are fabricated by employing poly(4‐vinylpyridine) (PVP) as the modified layer of typical inorganic dielectric (SiO2). The MoS2 nanoflakes are directly exfoliated from bulk MoS2 and transferred onto the PVP surface instead of bare SiO2 substrate that renders the enlarged nanoflake size. Taking advantage of the high surface energy and low surface roughness of PVP surface, the enhanced interaction between PVP and MoS2 bulk crystal may be achieved that is responsible for the large‐size MoS2 nanoflakes (≈2.5 × 105 μm2). Importantly, MoS2 FETs based on the double‐gate insulators consisting of PVP and SiO2 exhibit improved device performances. The on‐state current presents a fivefold increase and the field‐effect mobility is improved from 4.75 to 167.79 cm2 Vs−1, which are attributed to the PVP surface with low charge‐trap states and the lowered Schottky Barrier height (ΦSB). The current studies will effectively push the applications of MoS2 nanoflakes in flexible electronics. [ABSTRACT FROM AUTHOR]

Low-dimensional transition-metal dichalcogenides (TMDs) have recently emerged as promising materials for electronics and optoelectronics. In particular, photodetectors based on mono- and multilayered molybdenum disulfide (MoS2) have received much attention owing to their outstanding properties, such as high sensitivity and responsivity. In this study, photodetectors based on dispersed MoS2 nanoflakes (NFs) are demonstrated. MoS2 NFs interact with Ag nanoparticles (NPs) via low-temperature annealing, which plays a crucial role in determining device characteristics such as good sensitivity and short response time. The fabricated devices exhibited a rapid response and recovery, good photo-responsivity, and a high on-to-off photocurrent ratio under visible light illumination with an intensity lower than 0.5 mW/cm2. [ABSTRACT FROM AUTHOR]

Low-dimensional transition-metal dichalcogenides (TMDs) have recently emerged as promising materials for electronics and optoelectronics. In particular, photodetectors based on mono- and multilayered molybdenum disulfide (MoS2) have received much attention owing to their outstanding properties, such as high sensitivity and responsivity. In this study, photodetectors based on dispersed MoS2 nanoflakes (NFs) are demonstrated. MoS2 NFs interact with Ag nanoparticles (NPs) via low-temperature annealing, which plays a crucial role in determining device characteristics such as good sensitivity and short response time. The fabricated devices exhibited a rapid response and recovery, good photo-responsivity, and a high on-to-off photocurrent ratio under visible light illumination with an intensity lower than 0.5 mW/cm2.

Recent research interest in two-dimensional (2D) materials has led to an emerging new group of materials known as transition metal dichalcogenides (TMDs), which have significant electrical, optical, and transport properties. MoS2 is one of the well-known 2D materials in this group, which is a semiconductor with controllable band gap based on its structure. The hydrothermal process is known as one of the scalable methods to synthesize MoS2 nanostructures. In this study, the gas sensing properties of flower-shaped MoS2 nanoflakes, which were prepared from molybdenum trioxide (MoO3) by a facile hydrothermal method, have been studied. Material characterization was performed using X-ray diffraction, Brunauer–Emmett–Teller surface area measurements, elemental analysis using energy dispersive X-ray spectroscopy, and field-emission scanning electron microscopy. The gas sensing characteristics were evaluated under exposure to various concentrations of xylene and methanol vapors. The results reveal higher sensitivity and shorter response times for methanol at temperatures below 200 °C toward 200 to 400 ppm gas concentrations. The sensing mechanisms for both gases are discussed based on simulation results using density functional theory and charge transfer.

The graphitic carbon nitride (g-C 3 N 4) hollow nanotubes synthesized via a simple freeze-drying method are used for constructing Two-dimensional (2D)-one-dimensional (1D) molybdenum sulfide (MoS 2) nanoflake/g-C 3 N 4 hollow nanotube (MoS 2 /g-C 3 N 4 nanotube) photocatalysts. The MoS 2 /g-C 3 N 4 nanotube composite with 15 wt% MoS 2 shows the highest hydrogen (H 2) production rate (1124 μmol·h−1·g−1), much higher than bulk g-C 3 N 4 (64 μmol·h−1·g−1) and g-C 3 N 4 nanotubes (189 μmol·h−1·g−1). The excellent photocatalytic activity of MoS 2 /g-C 3 N 4 nanotube composites can be ascribed to more exposed active edges of 2D-1D structure, multiple light reflection/scattering channels of 2D nanoflake/1D hollow nanotube composite structure and better carrier transfer and separation by heterojunction interface. [ABSTRACT FROM AUTHOR]

Many kinds of mycotoxins can be found in cereals and feeds, thus increasing food safety requires effective and simultaneous detection of multitoxins. Herein, a flexible and three-dimensional (3D) film from CdS nanoparticles/MoS2 nanoflakes/reduced graphene oxide/carbon nanotubes (CMGC) nanocomposites was synthesized and pasted on various substrates including FTO, ITO, and glass carbon electrode (GCE) as the immunosensor substrate. By decorating the film electrode with different antigens, we built a modularity immuosensor using a ratiometric signal from photoelectrochemical (PEC) and cyclic voltammetric (CV) response, thus a universal standard curve was established to detect ochratoxin A (OTA), aflatoxin B1 (AFB1) and zearalenone (ZEN). In addition, such a tape-pasted electrode was removable and renewable, which can be used to detect toxins in cereals with high sensitivity and accuracy. We believe that such a detection of OTA, AFB1, and ZEN from modularity and ratiometry can offer alternative strategies of the immunosensor in multicomponent detection. [ABSTRACT FROM AUTHOR]

This communication reports the facile hydrothermal synthesis of fluorescent two-dimensional layered MoS 2 nanoflakes using a biomolecule (l -cysteine) for efficient and sensitive detection of mercury ions (Hg2+) in aqueous solution by monitoring the fluorescence quenching of MoS 2 in a ratiometric approach. This fluorescence quenching of MoS 2 was successfully utilized to detect Hg2+ ions in both normal (H9c2 cell line) and cancer (A549 cell line) cells as well via fluorescence imaging microscopy. The as-synthesized MoS 2 nanostructured sample was characterized using UV–vis absorption, steady-state fluorescence emission, X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. The strong fluorescence emission of nanostructured MoS 2 was heavily quenched by Hg2+ ions in aqueous medium as confirmed by fluorescence spectroscopic results. The binding of Hg2+ with MoS 2 nanoflakes and the resulting fluorescence quenching were also supported by Stern–Volmer analysis. The selectivity and sensitivity of the interaction of Hg2+ ions with the as-prepared MoS 2 nanoflakes among all other interfering metal ions were analyzed. The selective interaction of Hg2+ with MoS 2 was also accompanied by a distinct color change from bluish-green to flaxen or pale yellowish-gray in aqueous medium. The limit of detection of Hg2+ ions in aqueous medium was 0.63 nM. The possible interactions between Hg2+ and MoS 2 were confirmed by Fourier transform infrared spectroscopy, time-resolved fluorescence, and cyclic voltammetry studies. Density functional theoretical calculations provided useful information to correlate the electronic structure and energy band distributions with the spectroscopic results for the interaction of Hg2+ with MoS 2 nanoflakes. The MoS 2 nanoflakes showed no significant cytotoxicity during their interaction with Hg2+ ions in the intracellular medium, as confirmed by MTT assay, thereby ensuring possible future biomedical applications. [Display omitted] • Hg2+ ion sensing in solution and cells by MoS 2 nanoflakes via fluorescence quenching. • Fluorescence quenching of MoS 2 in presence of Hg2+ ions was primarily static. • Selectivity of MoS 2 /Hg2+ interaction was associated with colour change of solution. • Limit of detection (LoD) of Hg2+ ion in aqueous medium was ∼0.63 nM. • MTT assay confirmed no significant cytotoxicity of as-synthesized MoS 2 nanoflakes. [ABSTRACT FROM AUTHOR]

By using DFT method, we stitch monolayer MoS 2 nanoflakes with different manners to tune the behaviors. The stability of these structures is identified by molecular dynamics simulations. The effect of chemical modification is also given and assessed by the calculated edge adsorption energy. It is found that the electronic structures can be manipulated from semiconducting to metallic properties by different edge modifications. The prototypes can also be constructed into three-terminal FET which owns smaller value of subthreshold swing S and the considerable transconductance G comparable to that of experiments. More importantly, we utilize the spin-transport properties to achieve a kind of voltage-driven spintronic logic gates. We control the spin transport with the electric field only and find the model can function in all base 'AND', 'OR', 'NOT' logic operations under specific combinations of the gate bias. The advantages of monolayer MoS 2 nanoflakes are thus expected. • Four special MoS 2 nanostructures are proposed for the first time. • The electronic structures can be manipulated from semiconducting to metallic properties by different edge modifications. • A kind of voltage-driven spintronic logic gates made by tailed monolayer MoS 2 nanoflakes run successfully. [ABSTRACT FROM AUTHOR]

A simple, rapid, and effective colorimetric assay for the detection of uric acid (UA) has been built, using the MoS2 nanoflakes-catalyzed 3,3′,5,5′-tetramethylbenzidine (TMB)-H2O2 system. In the presence of oxygen and uricase, uric acid was oxidized specifically to produce H2O2. MoS2 nanoflakes synthesized by hydrothermal reaction could catalyze the oxidation of TMB by H2O2, and engendering the colorimetric signal. Finally, the change in the color from colorless to blue was seen with naked eye, indicating the presence or absence of UA. Under the optimized conditions, a linear relationship between the absorbance and UA concentration in the range of 0.5-100 μM (R2 = 0.996) with the limit of detection for 0.3 μM (S/N = 3). The proposed assay was successfully applied to the detection of UA in human serum with the recoveries over 94.54%. Thus, these results suggest that the UA assay-based MoS2-catalyzed TMB-H2O2 has great foreground for fast clinical diagnosis of gout without the need for advanced and costly equipment.ᅟ [ABSTRACT FROM AUTHOR]

Highlights • UCNPs-MoS 2 nanoassemblies were developed to detect reactive oxygen species (ROS) with a fast response time. • The nanoprobe had been successfully applied in the imaging of exogenous and endogenous ROS in living cells. • The nanoprobe was employed in in vivo visualization of ROS level in zebrafish. Abstract Nanoassemblies for bioimaging in living cells have attracted much attention. In this work, an efficient and sensitive turn-on fluorescent detection platform for reactive oxygen species (ROS) in living cells has been constructed using the nanoassemblies of upconversion nanoparticles (UCNPs)-MoS 2 nanoflakes. In this nanostructure, the positively charged UCNPs could assemble with negatively charged poly(acrylic acid) modified MoS 2 nanoflakes by electrostatic force, which led to the remarkable fluorescence quenching of UCNPs owing to the excellent quenching ability of MoS 2 nanoflakes. In contrast, in the presence of ROS, the fluorescence recovery of UCNPs is successfully realized owing to the decomposition of MoS 2 nanoflakes through the chemical reaction with ROS. The ROS-mediated disassembly of the nanoarchitecture display excellent fluorescent response toward ROS. Furthermore, the disassembly of UCNPs-MoS 2 nanoflakes has been successfully used for ROS bioimaging in cells and zebrafish. [ABSTRACT FROM AUTHOR]

Structure and morphology of molybdenum disulfide (MoS2) play an important role in improving its reversible lithium storage and sodium storage as anodes. In this study, a facile method is developed to prepare C/C@SnO2/MoS2 nanofibers with MoS2 nanoflakes anchoring on the core-shell C/C@SnO2 nanofibers through hydrothermal reaction. By adjusting the concentration of MoS2 precursors, the synthesized MoS2 with different slabs dimensions, size, and morphologies are obtained, constituting budding and blooming wintersweet branch-like composite structure, respectively. Owing to scattered MoS2 nanoparticles and sporadic MoS2 nanoflakes, the budding wintersweet branch-like composite nanofibers processes less slabs of staking in number and large specific surface area. Benefiting from the exposed C@SnO2 shell layer, the synergistic effect among SnO2, carbon, and MoS2 is strengthened, which maximizes the advantage of each material to exhibit stable specific capacities of 650 and 230 mAh g−1 for Li-ion batteries and Na-ion batteries after 200 cycles. [ABSTRACT FROM AUTHOR]

In this study, an LC wireless passive humidity sensor based on MoS2 nanoflakes was proposed. The LC wireless passive humidity sensor was optimized by performing HFSS simulations and fabricated via a screen-printing technique. The MoS2 nanoflakes were characterized by laser scanning confocal microcopy, scanning electron microscope, and X-ray diffraction. The measurements show the sensor can operate stably for a long time with a hysteresis of 4% RH (relative humidity) in 10⁻95% RH. At low humidity environment (10⁻60% RH), the sensitivity of the as-prepared humidity sensor is 2.79 kHz/% RH, and a sensitivity of 76.04 kHz/% RH was realized in a high humidity environment (60⁻95% RH). In this regard, the sensing mechanism was discussed in the scope of proton transfer theory. The test results also indicate that the response time and recovery time of the prepared sensor are 10 s, 15 s, respectively and between 15~40 °C the sensitivity of sensor was not temperature-dependent in the range of 10~80% RH. In addition, the sensor shows less sensitivity to temperature in the 15⁻25 °C range at 90% RH. All of these experimental results show that the prepared LC wireless passive humidity sensor can stably monitor the rapidly changing humidity in a sealed and narrow environment for a long time.

MoS2 nanoflakes were prepared by exfoliating commercial MoS2 powders with the assistance of ultrasound and graphene foam was synthesized by chemical vapor deposition using nickel foam as the template. MoS2-graphene hybrid nanosheets were developed through the combination of MoS2 nanoflakes and graphene nanosheets by ultrasonic dispersion. The hybrid nanosheets were sprayed onto the ITO coated glass, which acts as an electrode for the simultaneously electrochemical determination of levodopa and uric acid. The MoS2-graphene hybrid nanosheets were characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The results show that the hybrid nanosheets are composed of MoS2 and graphene with a sheet-like morphology. The sensitivity of the electrode for levodopa and uric acid is 0.36 μA μM−1 and 0.39 μA μM−1, respectively. The electrode also shows low limit of detection, good selectivity, reproducibility and stability. And it is potential for use in clinical research. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) Cd-MoS2 monolith was fabricated at room temperature using 2D MoS2 nanoflakes as precursor and Cd cations through an interaction between the S atoms on the surface of the MoS2 nanoflakes and the Cd cations. Then, the Cd-MoS2 was measured by various techniques. The measurement results show that, to some extent, the Cd-MoS2 structure is still amorphous like that of the MoS2 nanoflakes, and it is also a kind of mesoporous material with a mean diameter of 15.70nm and specific surface area of 22.01m2/g. The adsorption results of Rhodamine B and Cu solutions demonstrate that such material exhibits relatively strong adsorption behaviors and high adsorption capability, and also it can be reused for the adsorption after the adsorbates are taken out. 3D Cd-MoS2 porous monolith was fabricated at room temperature using 2D MoS2 nanoflakes as precursor and Cd2+ cations through an interaction between the S atoms on the surface of the MoS2 nanoflakes and the Cd2+ cations. Such material exhibits relatively strong capacities in an adsorption of Rhodamine B molecules or Cu2+ cations. [ABSTRACT FROM AUTHOR]

Among lead-free halide double perovskites, Cs 2 AgBiBr 6 is a potential alternative to substitute toxic and unstable organic-inorganic lead-based halide perovskites. However, the film forming ability and wide indirect bandgap have impeded its applications. Herein, we investigate to use MoS 2 nanoflakes as a hole transport interlayer to improve the crystallinity of Cs 2 AgBiBr 6 , tailor energy level alignments and enhance the stability of solar cells. With the addition of the MoS 2 nanoflakes, the Cs 2 AgBiBr 6 -based solar cell has a power conversion efficiency of 4.17% with an open circuit voltage of 1.10 V and short-circuit current of 6.12 mA cm−2. This work would provide a new approach for developing all inorganic lead-free Cs 2 AgBiBr 6 -based solar cells with high power conversion efficiency and good stability. • MoS 2 can tailor the energy level of Cs 2 AgBiBr 6 to enhance hole extraction. • The power conversion efficiency of the device with MoS 2 nanoflakes is up to 4.17%. • The devices with MoS 2 remain 90% efficiency up to 23 days under ambient conditions. [ABSTRACT FROM AUTHOR]

Metal oxide-based gas sensors have advantages over electrochemical sensors of small size, low cost, and longer utilization life, but their performance in detecting ppb-level NO 2 is compromised at room temperature (RT). In this work, a p-n MoS 2 -In 2 O 3 heterojunction was constructed by in situ vertically growing MoS 2 nanoflakes on the surface of In 2 O 3 microtubes. The In 2 O 3 @MoS 2 composite with a 25 % mass rate of MoS 2 presents an outstanding sensing performance with a response of 39.4 to 1 ppm NO 2 at RT. The response and recovery time are 72 s and 118 s, respectively, and the detection limit is 115.4 ppb. The enhanced NO 2 sensing performance may benefit from p-n heterojunction at the MoS 2 -In 2 O 3 interface, the increased oxygen vacancies and chemisorbed oxygen, and the unique structure. The exposed sulfur active sites and chemical bonds introduced from MoS 2 also contribute to the excellent gas sensor performance. Thus, this work proved that the In 2 O 3 @MoS 2 sensor is a promising material for detecting trace NO 2 at RT. [Display omitted] [ABSTRACT FROM AUTHOR]

A planar microbattery that enables various in situ measurements of lithiation of 2D materials on the individual‐flake scale is developed. A large conductivity increase of thick MoS2 crystallite lithiation due to the formation of a percolative Mo nanoparticle network embedded in a Li2S matrix is observed. The nanoscale study leads to the development of a novel charging strategy for batteries that largely improves the capacity and cycling performance confirmed in bulk MoS2/Li coin cells. [ABSTRACT FROM AUTHOR]

A unique UV photodetector architecture of MoS 2 /ZnO/HNPs is explored for the enhanced UV photo-response. The hybrid configuration offers greatly improved localized surface plasmon resonance (LSPR) and sufficient absorption as well as efficient transmittance of 2-D transition metal dichalcogenide MoS 2 nanoflakes. [Display omitted] • Demonstration of novel hybrid photodetector architecture of MoS 2 /ZnO/HNP for the significantly increased photocurrent. • Detailed explanation for photocurrent enhancement mechanism by the FDTD simulation. • Detailed morphological, elemental and current–voltage (I-V) study. • Systematic comparison and demonstration of the superior photoresponse. A unique ultraviolet (UV) photodetector architecture of MoS 2 /ZnO/HNP is explored and significantly increased photocurrent (I ph) of 4 × 10−3 A is demonstrated under the 385 nm illumination of 54.9 mW/mm2 at 10 V. This leads to the superior device performance factors: i.e., photoresponsivity of 21,111 mA/W, detectivity of 7.9 × 1011 jones and EQE of 6,800 %. These device performance factors confirm that the proposed photodetector configuration is superior as compared to the similar versions of ZnO-based UV photodetectors. The hybrid MoS 2 /ZnO/HNP architecture is constructed by the 2-D transition metal dichalcogenide MoS 2 nanoflakes, wide-bandgapZnO quantum dots (QDs) and plasomonic PdAg hybrid nanoparticles (HNPs). The increased I ph is related to the hot carrier injection through the strongly improved localized surface plasmon resonance (LSPR) by the PdAg HNPs and additional photo carriers from the 2-D MoS 2 nanoflakes on top of the original photo-induced carriers in the ZnO QD layer. The PdAg HNPs are fabricated by a unique two-step solid-state dewetting (SSD) technique, having the core-shelled PdAg NPs with the high-density small background Ag NPs. This HNP configuration offers very high-density hot spots and significantly improved LSPR. The photocurrent enhancement of MoS 2 /ZnO/HNP architecture is systematically studied by the finite-difference time-domain (FDTD) simulations. [ABSTRACT FROM AUTHOR]

In this study, we investigate the spin–spin correlation of two magnetic impurities in zigzag edge MoS 2 nanoflakes using a three-orbital tight-binding model. In particular, we consider the dependence of the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction on the local electric field strength for providing a degree of tunability in triangular and rectangular nanoflakes. Our results indicate that manipulating the local electric field at the zigzag edges could allow the control of all the different components of the RKKY interaction in MoS 2 nanoflakes. Interestingly, the Dzyaloshinskii–Moriya J DM oscillates but does not decay due to strong spin–orbit coupling. Moreover, the electric field induces a sizable J DM interaction as a function of the magnetic separation along zigzag edges for various Fermi energies. Our findings provide a method for enhancing the RKKY exchange interactions with magnetic arrays in these materials. • Investigation of RKKY interaction in zigzag edge MoS 2 nanoflakes. • Local electric field controlled all of the different components of the RKKY interaction. • Dzyaloshinskii–Moriya interaction oscillated but did not decay due to strong spin–orbit coupling. • Electric field induced a sizable Dzyaloshinskii–Moriya interaction. [ABSTRACT FROM AUTHOR]

In recent years, nanozymes based on two-dimensional (2D) nanomaterials have been receiving great interest for cancer photothermal therapy. 2D materials decorated with nanoparticles (NPs) on their surface are advantageous over conventional NPs and 2D material based systems because of their ability to synergistically improve the unique properties of both NPs and 2D materials. In this work, we report a nanozyme based on flower-like MoS 2 nanoflakes (NFs) by decorating their flower petals with NCeO 2 using polyethylenimine (PEI) as a linker molecule. A detailed investigation on toxicity, biocompatibility and degradation behavior of fabricated nanozymes in wild-type Drosophila melanogaster model revealed that there were no significant effects on the larval size, morphology, larval length, breadth and no time delay in changing larvae to the third instar stage at 7-10 d for MoS 2 NFs before and after NCeO 2 decoration. The muscle contraction and locomotion behavior of third instar larvae exhibited high distance coverage for NCeO 2 decorated MoS 2 NFs when compared to bare MoS 2 NFs and control groups. Notably, the MoS 2 and NCeO 2 -PEI-MoS 2 NFs treated groups at 100 μ g ml -1 covered a distance of 38.2 mm (19.4% increase when compared with control) and 49.88 mm (no change when compared with control), respectively. High-resolution transmission electron microscopy investigations on the new born fly gut showed that the NCeO 2 decoration improved the degradation rate of MoS 2 NFs. Hence, nanozymes reported here have huge potential in various fields ranging from biosensing, cancer therapy and theranostics to tissue engineering and the treatment of Alzheimer's disease and retinal therapy., (© 2022 IOP Publishing Ltd.)

Transition metal chalcogenides (TMC) have received much attention as active photocatalysts for environmental remediation. Additionally, the removal of sulfur-containing substances such as thiophene (TP) has become a requirement in fuel processing technology. Herein, we have synthesized MoS 2 nanoflakes via a sol-gel method. Subsequently, MoS 2 was loaded onto reduced graphene oxide (rGO) to produce a MoS 2 @rGO photocatalyst. The improved MoS 2 @rGO photocatalyst demonstrated total photooxidative desulfurization of TP after 75 min under visible light, and it exhibited excellent recyclability. The prepared nanocomposite exhibited enhanced visible light absorption with a decrease of the bandgap from 1.92 to 1.69 eV at 15 wt% of rGO addition. The recombination of the produced charge carriers was also diminished, as confirmed by photoluminescence and photocurrent measurements in the presence of rGO. This work will shed light on using rGO-supported TMC-based photocatalysts for fuel and related industries. Unlabelled Image • Sol-gel prepared MoS 2 nanoflakes on rGO by a simple process. • Light absorption and charge separation enhanced by adjusting the rGO amount. • Optimized MoS 2 @rGO showed 100% photooxidation of TP after 75 min irradiation. • MoS 2 @rGO can show applicability for fuel process technology. [ABSTRACT FROM AUTHOR]

• Direct growth of high-concentration MoS 2 nanoflakes on carbon nanotube sheet is realized. • Plasma treatment can induce de-bundling and activation of carbon nanotube bundles. • Plasma activation of CNT sheet is necessary to deposit high-concentration MoS 2 nanoflakes. • Interfaces of MoS 2 and CNT at the atomic scale is investigated. In this report, we demonstrate a novel two-step approach that is capable of growing uniform high-concentration MoS 2 nanoflakes on the carbon nanotube (CNT) sheet substrate. The CNT sheet is simply activated by the oxygen plasma to separate large CNT bundles and to create more active surface sites. A typical chemical vapor deposition (CVD) process is employed, enabling the direct growth of MoS 2 nanoflakes on the activated CNT substrate. Morphologies and structures of MoS 2 /CNT nanohybrid are characterized by SEM/EDS, high-resolution TEM (HRTEM) and Raman spectroscopy. Our results suggest that the plasma treatment of CNT sheet is critical to obtain well-dispersed large quantity of MoS 2 nanoflakes on CNT assemblies. [ABSTRACT FROM AUTHOR]

In this study, an LC wireless passive humidity sensor based on MoS2 nanoflakes was proposed. The LC wireless passive humidity sensor was optimized by performing HFSS simulations and fabricated via a screen-printing technique. The MoS2 nanoflakes were characterized by laser scanning confocal microcopy, scanning electron microscope, and X-ray diffraction. The measurements show the sensor can operate stably for a long time with a hysteresis of 4% RH (relative humidity) in 10–95% RH. At low humidity environment (10–60% RH), the sensitivity of the as-prepared humidity sensor is 2.79 kHz/% RH, and a sensitivity of 76.04 kHz/% RH was realized in a high humidity environment (60–95% RH). In this regard, the sensing mechanism was discussed in the scope of proton transfer theory. The test results also indicate that the response time and recovery time of the prepared sensor are 10 s, 15 s, respectively and between 15~40 °C the sensitivity of sensor was not temperature-dependent in the range of 10~80% RH. In addition, the sensor shows less sensitivity to temperature in the 15–25 °C range at 90% RH. All of these experimental results show that the prepared LC wireless passive humidity sensor can stably monitor the rapidly changing humidity in a sealed and narrow environment for a long time. [ABSTRACT FROM AUTHOR]

Recent research interest in two-dimensional (2D) materials has led to an emerging new group of materials known as transition metal dichalcogenides (TMDs), which have significant electrical, optical, and transport properties. MoS 2 is one of the well-known 2D materials in this group, which is a semiconductor with controllable band gap based on its structure. The hydrothermal process is known as one of the scalable methods to synthesize MoS 2 nanostructures. In this study, the gas sensing properties of flower-shaped MoS 2 nanoflakes, which were prepared from molybdenum trioxide (MoO 3 ) by a facile hydrothermal method, have been studied. Material characterization was performed using X-ray diffraction, Brunauer-Emmett-Teller surface area measurements, elemental analysis using energy dispersive X-ray spectroscopy, and field-emission scanning electron microscopy. The gas sensing characteristics were evaluated under exposure to various concentrations of xylene and methanol vapors. The results reveal higher sensitivity and shorter response times for methanol at temperatures below 200 °C toward 200 to 400 ppm gas concentrations. The sensing mechanisms for both gases are discussed based on simulation results using density functional theory and charge transfer.

The construction of safe and stable theranostics is beneficial to realize simultaneous cancer diagnosis and treatment. In this study, bovine serum albumin-gadolinium (BSA-Gd) complexes and MoS 2 nanoflakes (MoS 2 -Gd-BSA) were successfully married as cancer theranostics for dual-modality magnetic resonance (MR)/photoacoustic (PA) imaging and photothermal therapy (PTT). BSA-Gd complexes were prepared by the biomineralization method and then conjugated with MoS 2 nanoflakes via an amide bond. The as-prepared MoS 2 -Gd-BSA possessed a good photostability and photothermal effect. The cytotoxicity assessment and hemolysis assay suggested the excellent biocompatibility of MoS 2 -Gd-BSA. Meanwhile, MoS 2 -Gd-BSA could not only achieve in vivo MR/PA dual-modality imaging of xenograft tumors, but also effectively kill cancer cells in vitro and ablate the xenograft tumors in vivo upon 808 nm laser illumination. The biodistribution and histological evaluations indicated the negligible toxicity of MoS 2 -Gd-BSA both in vitro and in vivo. Thus, our results substantiated the potential of MoS 2 -Gd-BSA for cancer theranostics.

Developing biodegradable photothermal agent holds great significance for potential clinical translation of photothermal therapy. In the current study, one-pot hydrothermal synthesis of MoS 2 nanoflakes with desirable degradation capability was presented. The participation of poly(acrylic acid) (PAA) in hydrothermal process could not only facilitate the modification of polyethylene glycol (PEG), but also bestow degradability to the prepared MoS 2 nanoflakes. Moreover, the PEGylated hybrid nanoflakes (MoS 2 -PPEG) also exhibited excellent stability in various medium and outstanding photothermal properties. Interestingly, MoS 2 -PPEG behaved distinctly different degradation rate in diverse condition. The rapid degradation of MoS 2 -PPEG was observed in neutral pH solution, whereas much slower degradation occurred in an acidic tumor microenvironment. Furthermore, data indicated that the major degradation product of MoS 2 -PPEG was water-soluble Mo-based ion. Meanwhile, the good in vitro biocompatibility of MoS 2 -PPEG was also confirmed in terms of cytotoxicity and hemolysis. With favorable photothermal performance, MoS 2 -PPEG can efficiently killing cancer cells in vitro and suppress the tumor growth in vivo. More importantly, the gradual decreasing content of MoS 2 -PPEG in organs and detectable Mo element in urine of mice suggested that the degradability of MoS 2 -PPEG might facilitate its excretion to some degree. Hence, the degradable MoS 2 nanoflakes prepared by one-pot hydrothermal routine may provide insight for further biomedical applications of inorganic photothermal agent.

Exploitation of novel hybrid nanomaterials for combinational tumor therapy is challenging. In this work, we synthesized dendrimer-modified MoS 2 nanoflakes for combinational gene silencing and photothermal therapy (PTT) of cancer cells. Hydrothermally synthesized MoS 2 nanoflakes were modified with generation 5 (G5) poly(amidoamine) dendrimers partially functionalized with lipoic acid via disulfide bond. The formed G5-MoS 2 nanoflakes display good colloidal stability and superior photothermal conversion efficiency and photothermal stability. With the dendrimer surface amines on their surface, the G5-MoS 2 nanoflakes are capable of delivering Bcl-2 (B-cell lymphoma-2) siRNA to cancer cells (4T1 cells, a mouse breast cancer cells) with excellent transfection efficiency, inducing 47.3% of Bcl-2 protein expression inhibition. In vitro cell viability assay data show that cells treated with the G5-MoS 2 /Bcl-2 siRNA polyplexes under laser irradiation have a viability of 21.0%, which is much lower than other groups of single mode PTT treatment (45.8%) or single mode of gene therapy (68.7%). Moreover, the super efficacy of combinational therapy was further demonstrated by treating a xenografted 4T1 tumor model in vivo. These results suggest that the synthesized G5-MoS 2 nanoflakes may be employed as a potential nanoplatform for combinational gene silencing and PTT of tumors.