Bing Wang

Two-dimensional (2D) materials have received extensive attention in optoelectronics because of their unique characteristics. However, due to the extremely thin thickness of 2D materials, their optical absorption is limited. In recent years, researchers have used different effects and structures to enhance the optical absorption of 2D materials. The waveguide, as a device to guide and limit light propagation, has been integrated into photodetectors based on 2D materials, most of which have been applied in the infrared spectrum. This article reviews the development of waveguide-integrated photodetectors based on 2D materials, mainly in the infrared spectrum in recent years. Discussions mainly focus on the preparation of materials in waveguide-integrated photodetectors, the design and simulation of waveguide structures, and the summary of research results and applications of waveguide-integrated photodetectors in recent years. Finally, the challenges and prospects of waveguide-integrated photodetectors are put forward and discussed.

Ischemic stroke is still a serious threat to human life and health, but there are few therapeutic options available to treat stroke because of limited blood-brain penetration. The development of nanotechnology may overcome some of the problems related to traditional drug development. In this review, we focus on the potential applications of nanotechnology in stroke. First, we will discuss the main molecular pathological mechanisms of ischemic stroke to develop a targeted strategy. Second, considering the important role of the blood-brain barrier in stroke treatment, we also delve mechanisms by which the blood-brain barrier protects the brain, and the reasons why the therapeutics must pass through the blood-brain barrier to achieve efficacy. Lastly, we provide a comprehensive review related to the application of nanomaterials to treat stroke, including liposomes, polymers, metal nanoparticles, carbon nanotubes, graphene, black phosphorus, hydrogels and dendrimers. To conclude, we will summarize the challenges and future prospects of nanomedicine-based stroke treatments.

Due to the increasing market demand for graphene-based devices, van der Waals heterostructures based on 2D materials have increased rapidly worldwide during the last decade. Graphene-based applications are inadequate in some electronic devices such as field-effect transistors (FETs) and solar cells devices due to its intrinsic zero bandgap and complex mechanistic approach in related chemistry. Thus, it is highly desired to fill the gap and devote efforts to explore other 2D materials further, especially bi- and tri-elemental 2D materials, such as layered metal chalcogenides (LMDCs), metal oxides, and hexagonal boron nitride (hBN). During the past few years, a different research group contributed to improving the quality and performance of the mentioned 2D materials. Still, due to some deficiencies such as low conductivity and poor bandgap, there is a need to develop and investigate alternative materials. Recently, MXenes, which are compounds obtained due to the chemical delamination of quaternary or (ternary) layered nitrides or carbides, have been found as a great class of 2D elemental materials. The complex bonding in the MXene family (a mixture of metallic and covalent bonds) and other characteristics such as atomic stacking, electronic structures, surface terminal groups, and different synthetic routes are responsible for their unique properties such as hydrophilicity and metallicity, and they are predicted to have high elastic moduli in a single compound. On behalf of the rich chemistry and unique morphologies, MXene derivatives have delivered efficient sensors, energy storage materials, catalysts, and water purification materials. Although there is a great demand for MXene-based derivatives, there is further demand for their improvement such as the long-term stability, large scale production, as well as deposition and surface roughness, which create hurdles in their commercialization. Titanium-based MXene (Ti₃C₂Tx and Ti₂CTx) heterostructures with other 2D nanomaterials are highly desired to solve the surface roughness problems and long-term stability as well as an alternative to overcome the deficiency of the scalable production of MXenes. The existence of different active functionalities (–O, –OH, –F, etc.) on the surface of Ti₃C₂Tx and Ti₂CTx can be helpful for interacting with other 2D layered materials in the presence of solvents to fabricate heterostructures after using various deposition techniques such as spin coating, dip coating, and drop-casting for practical device fabrication processes. In the presence of weak interaction between the host (MXene derivatives) and guest (other nanostructures 2D materials), the intrinsic characteristics of both can be largely preserved for efficient energy storage applications. In this paper, we present a comprehensive literature library of the various strategies of 2D titanium-based MXenes such as Ti₃C₂Tx and Ti₂CTx for the fabrication of their heterostructures with 2D materials using various deposition techniques and the application of the resultant structures in the fields of optoelectronics, catalysis, and energy storage devices.

The highly efficient, 2D material‐based sensing devices are well‐suited with the advanced production technology which provide the data that can be applied effectively for the monitoring of environmental and health‐related problems. Recently, MXenes considered as new blood in the form of 2D transition metal carbides (TMC), transition metal nitride or transition metal carbonitrides that are added first time to 2D nanomaterials family MXene which are compounds obtained as a result of chemical delamination of quaternary or (ternary) layered nitrides or carbides found as an outstanding member of 2D elemental materials. On behalf of rich chemistries and unique morphologies, the MXenes derivatives delivered efficient sensors, energy storage, catalysis, and water purification. The superior volumetric surface area provides improved sensor response and greater optic, electrical, and magnetic characteristics, which are important advantages in biological and biomedical applications over macroscale materials. In this review article, different synthetics strategies of Mxene derivatives are organized and discuss their availability in terms of caste, yield, physical properties, and simplicity. To keep in mind, the facile synthetic approach and stable physical properties, the Ti₃C₂Tx Mxene is chosen as a model Mxene derivative, and its application in the field of environmental and biological sensors is discussed in detail.

The nonlinear optical (NLO) materials are playing a crucial role in almost all aspects of photonics including imaging frequency, manipulation, photon generation, transmission and detection. The nonlinear optics aims to investigate light response in NLO media, in which the NLO response is normally weak and low energy efficient. A comprehensive summary, discussion, and correlation of the light–matter interaction in the 2D nano‐platform, like graphene and TMDCs, would be inspirational and timely needed. In this contribution, a broad overview and discussion about recent experimental evolution regarding the NLO response and its corresponding applications in various 2D materials are presented. A wide material library including graphene, transition metal dichalcogenides, black phosphorus, MXenes, semimetals, polymer materials, and hybrid structures (0D, 1D, 3D) are discussed. In this review, the qualitative description of NLO is firstly illustrated, followed by various fundamental NLO processes being highlighted. Fundamental limits of nonlinear optics and some of NLO applications are prospected. It is hoped that this comprehensive review will shed a light on the development of nonlinear optics with 2D materials to be applied in the field of photonics and optoelectronics.

Cancer has been one of the major threats to the lives of human beings for centuries. Traditional therapy is more or less faced with certain defects, such as poor targeting, easy degradation, high side effects, etc. Therefore, in order to improve the treatment efficiency of drugs, an intelligent drug delivery system (DDS) is considered as a promising solution strategy. Due to their special structure and large specific surface area, 2D materials are considered to be a good platform for drug delivery. Black phosphorus (BP), as a new star of the 2D family, is recommended to have the potential to construct DDS by virtue of its outstanding photothermal therapy (PTT), photodynamic therapy (PDT), and biodegradable properties. This tutorial review is intended to provide an introduction of the current advances in BP‐based DDSs for cancer therapy, which covers topics from its construction, classified by the types of platforms, to the stimuli‐responsive controlled drug release. Moreover, their cancer therapy applications including mono‐, bi‐, and multi‐modal synergistic cancer therapy as well as the research of biocompatibility are also discussed. Finally, the current status and future prospects of BP‐based DDSs for cancer therapy are summarized.

Smart drug delivery nano-systems show significant changes in their physical or chemical properties in response to slight change in environmental physical and/or chemical signals, and further releasing drugs adjusted to the progression of the disease at the right target and rate intelligently. Two-dimensional materials possess dramatic status extend all over various scientific and technological disciplines by reason of their exceptional unique properties in application of smart drug delivery nano-systems. In this review, we summarized current progress to highlight various kinds of two-dimensional materials drug carriers which are widely explored in smart drug delivery systems as well as classification of stimuli responsive two-dimensional materials and the advantages and disadvantages of their applications. Consequently, we anticipate that this review might inspire the development of new two-dimensional materials with smart drug delivery systems, and deepen researchers’ understanding of smart nano-carries based on two-dimensional materials.

Photodetectors are optoelectronic devices with excellent photoelectric conversion abilities.