Growth of High-Quality Monolayer Transition Metal Dichalcogenide Nanocrystals by Chemical Vapor Deposition and Their Photoluminescence and Electrocatalytic Properties

Development of a MoS2/Ag NP Nanopocket to Trap Target Molecules for Surface-Enhanced Raman Scattering Detection with Long-Term Stability and High Sensitivity

Surface-enhanced Raman scattering (SERS) substrates mostly achieve highly sensitive detection by designing various hot spots; however, how to guide molecules to hot spots and prevent them from leaving has not been thoroughly considered and studied. Here, a composite MoS₂/Ag NP nanopocket detector composed of MoS₂ covered with a Ag NP film was fabricated to develop a general SERS method for actively capturing target molecules into hotspots. A finite element method (FEM) simulation of the multiphysics model was used to analyze the distributions of electric field enhancements and hydrodynamic processes in solution and air of the MoS₂/Ag NP nanopocket. The results revealed that covering MoS₂ slowed the evaporation of the solution, extended the window period for SERS detection, and enhanced the electric field in comparison with the monolayer Ag NP film. Therefore, in the process of dynamic detection, the MoS₂/Ag NP nanopocket can provide an efficient and stable signal within 8 min, increasing the high sensitivity and long-term stability of the SERS method. Furthermore, a MoS₂/Ag NP nanopocket detector was applied to detect antitumor drugs and monitor hypoxanthine structural changes in serum, which demonstrated long-term stability and high sensitivity for SERS analysis. This MoS₂/Ag NP nanopocket detector paves the way for developing the SERS method in various fields.

Polyaromatic cores for the exfoliation of popular 2D materials

Two-dimensional (2D) nanomaterials have attracted interest from the scientific community due to their unique properties. The production of these materials has been carried out by diverse methodologies, the liquid phase exfoliation being the most promising one due to its simplicity and potential scalability. The use of several stabilizers allows to obtain dispersions of these 2D nanomaterials in solvents with low boiling points. Herein we describe a general exfoliation method for different 2D materials employing a biphasic water/dichloromethane system and two different (poly)aromatic hydrocarbons (PAHs). This method allows us to obtain dispersions of the exfoliated 2D materials with high concentrations in the organic solvent. Due to the low boiling point of dichloromethane, and therefore its easy removal, the obtained dispersions can be employed as additives for different composites. We corroborate that the exfoliation efficiency is improved due to the π-π and van der Waals interactions between the PAHs and the layers of the 2D materials.

Hydrazine Hydrate Intercalated 1T-Dominant MoS2 with Superior Ambient Stability for Highly Efficient Electrocatalytic Applications

Metallic 1T-phase MoS₂ exhibits superior hydrogen evolution reaction (HER) performance than natural 2H-phase MoS₂ owing to its higher electrical conductivity and abundance of active sites. However, the reported 1T-MoS₂ catalysts usually suffer from extreme instability, which results in quick phase transformation at ambient conditions. Herein, we present a facile approach to engineer the phase of MoS₂ by introducing intercalated hydrazine. Interestingly, the as-synthesized 1T-dominant MoS₂ sample demonstrates excellent ambient stability without noticeable degradation for 3 months. Additionally, the 1T-dominant MoS₂ exhibits superior electrical conductivity (∼700 times higher than that of 2H-MoS₂) and improved electrochemical catalytic performance (current density ∼12 times larger than that of 2H-MoS₂ at an overpotential of 300 mV vs the reversible hydrogen electrode, RHE). Through experimental characterizations and density functional theory (DFT) calculation, we conclude that the stabilization of the metallic phase could be attributed to the electron donation from hydrazine molecules to the adjacent Mo atoms. The phase control strategy in this work provides a guideline to develop other highly efficient and stable two-dimensional (2D) electrocatalysts.

Cost-effective synthesis of 2D molybdenum disulfide (MoS2) nanocrystals: An exploration of the influence on cellular uptake, cytotoxicity, and bio-imaging

Ultrasmall MoS2 nanocrystals have unique optoelectronic and catalytic properties that have acquired significant attraction in many areas. We propose here a simple and economical method for synthesizing the luminescent nanocrystals MoS2 using the hydrothermal technique. In addition, the synthesized MoS2 nanocrystals display photoluminescence that is tunable according to size. MoS2 nanocrystals have many advantages, such as stable dispersion, low toxicity and luminescent characteristics, offering their encouraging applicability in biomedical disciplines. In this study, human lung cancer epithelial cells (A549) are used to assess fluorescence imaging of MoS2 nanocrystals. MTT assay, trypan blue assay, flow cytometry and fluorescence imaging results have shown that MoS2 nanocrystals can selectively target and destroy lung cancer cells, especially drug-resistant cells (A549).