Transition Metal Dichalcogenides (TMDCs) Heterostructures: Synthesis, Excitons and Photoelectric Properties

Advances and Challenges in Interfacial Binding Forces for Electrocatalysts

As a practical chemical energy conversion technology, electrocatalysis could be used in fields of energy conversion and environmental protection. In recent years, significant research efforts have been devoted to the design and development of high-performance electrocatalysts because the rational design of catalysts is crucial for enhancing electrocatalytic performance. Creating electrocatalysts by forming interactions between different components at the interface is an important means of controlling and improving performance. Therefore, several common interfacial binding forces used for synthesizing electrocatalysts was systematically summarized in this review for the first time. The discussion revolves around the crucial roles these binding forces play in various electrocatalytic reaction processes. Various characterization techniques capable of proving the existence of these interfacial binding forces was also involved in the review. Finally, some prospects and challenges for designing and researching materials through the utilization of interfacial binding forces were presented.

2D material-based surface plasmon resonance biosensors for applications in different domains: an insight

The design of surface plasmon resonance (SPR) sensors has been greatly enhanced in recent years by the advancements in the production and integration of nanostructures, leading to more compact and efficient devices. There have been reports of novel SPR sensors having distinct nanostructures, either as signal amplification tags like gold nanoparticles (AuNPs) or as sensing substrate-like two-dimensional (2D) materials including graphene, transition metal dichalcogenides (TMDCs), MXene, black phosphorus (BP), metal-organic frameworks (MOFs), and antimonene. Such 2D-based SPR biosensors offer advantages over conventional sensors due to significant increases in their sensitivity with a good figure of merit and limit of detection (LOD). Due to their atomically thin structure, improved sensitivity, and sophisticated functionalization capabilities, 2D materials can open up new possibilities in the field of healthcare, particularly in point-of-care diagnostics, environmental and food monitoring, homeland security protection, clinical diagnosis and treatment, and flexible or transient bioelectronics. The present study articulates an in-depth analysis of the most recent developments in 2D material-based SPR sensor technology. Moreover, in-depth research of 2D materials, their integration with optoelectronic technology for a new sensing platform, and the predicted and experimental outcomes of various excitation approaches are highlighted, along with the principles of SPR biosensors. Furthermore, the review projects the potential prospects and future trends of these emerging materials-based SPR biosensors to advance in clinical diagnosis, healthcare biochemical, and biological applications.

First-principles study of the effect of doping on the optoelectronic properties of defective monolayers of MoSe2

CONTEXT

In this paper, the structural stability, electronic structure, and optical properties of monolayer MoSe2 doped with C, O, Si, S, and Te atoms, respectively, under defective conditions are investigated based on first principles. It is found that the system is more structurally stable when defecting a single Se atom as compared to defecting a single Mo or two Se atoms. The electronic structure analysis of the system reveals that intrinsic MoSe2 is a direct bandgap semiconductor. The bandgap value of the system decreases with a single Se atom defect and introduces two new impurity energy levels in the conduction band. The defective systems doped with C and Si atoms all exhibit P-type doping. The total density of states of intrinsic MoSe2 is mainly contributed by the Mo-d and Se-p orbitals, and new density of state peaks appears near the conduction band after the defects of Se atoms. The total density of states of the defective system doped by each atom is mainly contributed by Mo-d, Se-p, and the result of the p orbital contribution of each dopant atom. By analyzing the dielectric function of each system, it is found that the intrinsic MoSe2 has the lowest static permittivity and the C-doped defect system has the highest static permittivity, which reaches 21.42. The C- and Si-doped defect systems are the first to start absorbing the light, and the intrinsic MoSe2 absorbs the light later, with its absorption edge starting at 1.25 eV. In the visible range, the reflection peaks of the systems move toward the high-energy region and the blue-shift phenomenon occurs. It is hoped that applying modification means to modulate the physical properties of the two-dimensional materials will provide some theoretical basis for broadening the application of monolayer MoSe2 in the field of optoelectronic devices.

METHODS

This study utilizes the first principle computational software package MS8.0 (Materials studio8.0) under density functional theory (DFT). The exchange-correlation potential (GGA-PBE) is described by the Perdew-Burke-Ernzerhof correlation function in CASTEP, and the potential function adopts the ultrasoft pseudopotential in the inverse space formulation. The plane wave truncation energy Ecut is set to 400 eV, the K-point is taken as 5 × 5 × 1, and the force convergence criterion is 0.05 eV/Å. The convergence accuracy of the total energy of the system is less than 1.0 × 10-5 eV/atom, the tolerance shift is less than 0.002 Å, and the stress deviation is less than 0.1 GPa. The vacuum layer is taken as 15 Å, which is intended to minimize the interlayer force. The vacuum layer was set to 15 Å to avoid the effect of layer-to-layer interaction forces in the crystal cell.

Layer-dependent excitonic valley polarization properties in MoS2-WS2 heterostructures

In this work, we investigate the polarization of the excitonics valley in MoS₂-WS₂ heterostructures using circular polarization-resolved photoluminescence. The valley polarization is the largest (≈28.45%) in the 1L-1L MoS₂-WS₂ heterostructure and the polarizability of A_WS2 decreases as the number of WS₂ layers increases. We further observed a redshift of exciton XMoS₂- in MoS₂-WS₂ heterostructures with the increase of WS₂ layers, which is attributed to the displacement of the MoS₂ band edge, indicating the layer-sensitive optical properties of the MoS₂-WS₂ heterostructure. Our findings shed light on the understanding of exciton behavior in multilayer MoS₂-WS₂ heterostructures that may promote their potential applications in optoelectronic devices.