Niobium telluride (NbTe₂), a kind of few-layer two-dimensional (2D) transition metal dichalcogenides (TMDs) material, has been theoretically predicted with nonlinear absorption properties and excellent optical response. Herein, we experimentally demonstrated an Er-doped fiber (EDF) laser based NbTe₂ as saturable absorber (SA). Few-layer NbTe₂ nanosheets were successfully prepared by adopting the commonly used liquid-phase exfoliation (LPE) method. The nonlinear optical response of highly stable few-layer NbTe₂ was investigated through an open-aperture Z-scan laser measurement, the nonlinear absorption coefficient was 2.45 × 10⁻¹¹ m/W. Both Q-switched and mode-locked operation centered at 1 559 nm were recorded based on NbTe₂ SA. The pulse duration was varied from 4.88 μs to 1.75 μs, and the adjustable range of repetition frequency is changed from 44.01 kHz to 64.12 kHz in passively Q-switched operation. Furthermore, a constant repetition rate of 5.33 MHz and pulse width of 2.67 ps were observed in mode-locked operation. Our experimental results fully reveal the nonlinear optical properties of NbTe₂ used in pulsed fiber lasers and broaden its ultrafast applications in the optics field.

Van der Waals (vdW) heterojunctions, with their unique electronic and optoelectronic properties, have become promising candidates for photodetector applications. Amplifying the contribution of the depletion region in vdW heterojunction, which would enhance both of the collection efficiency and speed of the photogenerated carriers, presents an effective strategy for achieving high performance vdW heterojunction photodetectors. Herein, a fully depleted vdW heterojunction photodetector is built on two-dimensional (2D) semiconductor materials (GaTe and InSe) layered on a pattered bottom electrode in vertical structure, in which the generation and motion of carriers are exclusively achieved in the depletion region. Attributed to the intrinsic built-in electric field, the elimination of series resistance and the depletion region confinement of carriers, the as-fabricated photodetector exhibits prominent photovoltaic properties with a high open-circuit voltage of 0.465 V, as well as photoresponse characteristics with outstanding responsivity, detectivity and photoresponse speed of 63.7 A/W, 3.88 × 10¹³ Jones, and 32.7 μs respectively. The overall performance of this fully depleted GaTe/InSe vdW heterojunctions photodetectors are ranking high among the top level of 2D materials based photodetectors. It indicates the device architecture can provide new opportunities for the fabrication of high-performance photodetectors.

Although photodetection based on two-dimensional (2D) van der Waals (vdWs) P–N heterojunction has attracted extensive attention recently, their low responsivity (R) due to the lack of carrier gain mechanism in reverse bias or zero bias operation hinders their applications in advanced photodetection area. Here, a black phosphorus/rhodamine 6G/molybdenum disulfide (BP/R6G/MoS₂) photodiode with high responsivity at reverse bias or zero bias has been achieved by using interfacial charge transfer of R6G molecules assembled between heterojunction layers. The formed vdWs interface achieves high performance photoresponse by efficiently separating the additional photogenerated electrons and holes generated by R6G molecules. The devices sensitized by the dye molecule R6G exhibit enhanced photodetection performance without sacrificing the photoresponse speed. Among them, the R increased by 14.8–20.4 times, and the specific detectivity (D*) increased by 24.9–34.4 times. The strategy based on interlayer assembly of dye molecules proposed here may pave a new way for realizing high-performance photodetection based on 2D vdWs heterojunctions with high responsivity and fast response speed.

Ti₃CN, as a typical hetero-MXene, has attracted tremendous attention for its unique properties. However, its ultrafast photonics applications are still rare. Here, the few-layer Ti₃CN MXene was successfully prepared by selective etching and molecular delamination technique. The nonlinear optical response of few-layer Ti₃CN MXene at 640 nm was studied using the open-aperture Z-scan technique. The as-prepared Ti₃CN MXene sample exhibited excellent nonlinear saturable absorption characteristics, resulting in the nonlinear absorption coefficient β of −4.05 × 10^-2 cm/GW, which was one order of magnitude larger than that of black phosphorus (BP) and molybdenum disulfide (MoS₂). For the optical modulation applications of few-layer Ti₃CN MXene, passively Q-switched (PQS) solid-state visible lasers based on Ti₃CN saturable absorber (SA) at 522 nm, 607 nm, 639 nm, and 721 nm were successfully realized. Furthermore, a Ti₃CN-based stable passively mode-locked Pr:YLF red laser was also successfully achieved with a pulse duration of 30 ps, and the corresponding repetition rate was 73.1 MHz. The optical modulation device based on few-layer Ti₃CN MXene shows good performance. Our work demonstrates that the tremendous prospects of the few-layer Ti₃CN MXene as a visible optical modulation device in ultrafast photonics applications.

Successful treatment of neurodegenerative diseases (NDDs), including Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HD), remains a significant challenge for neurologists due to the undesirable curative outcomes. Apart from surgeries, most drugs are only used to relieve the patients’ symptoms without a permanent cure of the disease. The development of novel biomaterials targeting NDDs is greatly hindered by the limited understanding of underlying molecular mechanisms. Considering the difficulties in NDD drug development and clinical trials, a comprehensive and up-to-date review of disease pathogenesis and related novel therapies are needed. In the current article, the basic concepts and pathogenic characteristics of NDDs are firstly illustrated. Following the detailed description of molecular mechanisms underlying three common NDDs, recent advances of drug development based on targeting different pathogenic mechanisms are clarified. Hopefully, this review will be beneficial to address the gap between materials and targeted mechanisms while simultaneously provide suggestions for the future design of precise NDD medicine.

Two-dimensional (2D) selenium was synthesized successfully in 2017. Its advanced properties, including size-dependent bandgap, excellent environmental robustness, strong photoluminescence effect, anisotropic thermal conductivity, and high photoconductivity, render it and selenium-based composites a promising candidate for various device applications. These include batteries, modulators, photodetectors, and photothermal effects in medical applications. However, compared to other commonly used 2D materials, such as graphene, transition metal dichalcogenides, and black phosphorus, 2D Se is much less known. Motivated by the need to overcome this lack of knowledge, this article focuses on recent progress and elucidates the crystal structure, synthesis methods, physical properties, applications, challenges, and prospects of 2D Se nanoflakes.

The construction of structures with multiple interfaces and dielectric/magnetic heterostructures enables the design of materials with unique physical and chemical properties, which has aroused intensive interest in scientific and technological fields. Especially, for electromagnetic (EM) wave absorption, enhanced interface polarization and improved impedence match with high Snoek's limitation could be achieved by multiple interfaces and dielectric/magnetic heterostructures, respectively, which are benificial to high-efficiency electromagnetic wave absorption (EWA). However, by far, the principles in the design or construction of structures with multiple interfaces and dielectric/magnetic heterostructures, and the relationships between those structures or heterostructures and their EWA performance have not been fully summarized and reviewed. This article aims to provide a timely review on the research progresses of high-efficency EM wave absorbers with multiple interfaces and dielectric/magnetic heterostructures, focusing on various promising EWA materials. Particularly, EM attenuation mechanisms in those structures with multiple interfaces and dielectric/magnetic heterostructures are discussed and generalized. Furthermore, the changllenges and future developments of EM wave absorbers based on those structures are proposed.

Two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDs), black phosphorus (BP), MXene and borophene, have aroused extensive attention since the discovery of graphene in 2004. They have wide range of applications in many research fields, such as optoelectronic devices, energy storage, catalysis, owing to their striking physical and chemical properties. Among them, anisotropic 2D material is one kind of 2D materials that possess different properties along different directions caused by the intrinsic anisotropic atoms’ arrangement of the 2D materials, mainly including BP, borophene, low-symmetry TMDs (ReSe₂ and ReS₂) and group IV monochalcogenides (SnS, SnSe, GeS, and GeSe). Recently, a series of new devices has been fabricated based on these anisotropic 2D materials. In this review, we start from a brief introduction of the classifications, crystal structures, preparation techniques, stability, as well as the strategy to discriminate the anisotropic characteristics of 2D materials. Then, the recent advanced applications including electronic devices, optoelectronic devices, thermoelectric devices and nanomechanical devices based on the anisotropic 2D materials both in experiment and theory have been summarized. Finally, the current challenges and prospects in device designs, integration, mechanical analysis, and micro-/nano-fabrication techniques related to anisotropic 2D materials have been discussed. This review is aimed to give a generalized knowledge of anisotropic 2D materials and their current devices applications, and thus inspiring the exploration and development of other kinds of new anisotropic 2D materials and various novel device applications.

Photodynamic therapy (PDT) is a promising non-invasive therapy approach for various diseases including malignant tumor. The process of PDT involves three interrelated aspects, namely photosensitizer (PS), light source, and oxygen, among which PS is the decisive factor that determines its anticancer efficiency. There exist some defects in currently applied PDT, such as inadequate production of reactive oxygen species (ROS), poor penetration of exciting light, insufficient oxygen supply, and nonselective distribution of PS. With unique physicochemical and optical properties, two-dimensional nanomaterials (2DNMs) have aroused great interest in biomedical fields. 2DNMs-based PDT is promising to significantly improve antitumor efficacy compared to conventional PDT. In this review, we will firstly introduce the underlying mechanism of PDT and how 2DNMs are absorbed and distribute inside tumor cells. After that, we will not only illustrate how 2DNMs-based PDT can enhance tumor-killing efficacy and minimize side-effects through conquering the above-mentioned defects of conventional PDT and the preparation process of 2DNMs, but also elaborate recent advances about 2DNMs-based PDT. Lastly, we will summarize the challenges and future prospects of 2DNMs-based PDT.

As an excellent optical device, photodetectors have many important applications, such as communication technology, display technology, scientific measurement, fire monitoring, aerospace and biomedical research, and it’s of great significance in the research of nanotechnology and optoelectronics. Graphene, as the first two-dimensional (2D) single-element nanomaterial, has the advantages of high carrier mobility, high strength, high light transmittance and excellent thermal conductivity, and it’s widely used in various nano-optical devices. The great success of graphene has led scientists to extensive research on other 2D single-element nanomaterials. Recently, a group of novel 2D single-element nanomaterials have attracted a lot of attention from scientists because of its excellent physical, chemical, electronic, mechanical and optical properties. Furthermore, it has opened a new door for the realization of new and efficient photodetectors. The group of 2D single-element nanomaterials are called 2D-Xenes and used to make high-performance photodetectors. Currently, there are few studies on photodetectors based on 2D-Xenes, but some 2D-Xenes have been applied to photodetectors and reported. Some of these have excellent photodetection performance, such as high photoresponsivity (R), broad spectral response range, fast photoresponse speed and high specific detectivity (D^*). Based on the novel 2D-Xenes, this review explores the types and preparation methods of 2D-Xenes, and the working mechanisms of 2D-Xenes photodetectors. Finally, the challenges and development trends of 2D-Xenes in the future are discussed. The research of 2D-Xenes is of great significance for the development of high-performance photodetectors in the future, and is expected to be widely used in other nanoelectronics and optical devices.