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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.

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]

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 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.)