Low dimensional materials based sensors have improved the detection strategy for sensing complex substances present in environment and human body.

Similar to graphene and black phosphorus (BP), 2D transition metal carbides and nitrides (MXenes) are of great interest in a variety of fields, such as energy storage and conversion, sensors, electromagnetic interference (EMI) shielding, and photothermal therapy due to their excellent conductivity and hydrophilicity, large specific capacitance, high photothermal effect, and superior electrochemical performance. To further broaden applicable ranges beyond their existing boundaries and fully exploit these potentials, functional 2D MXene nanostructures in recent years have been rationally designed and developed by various approaches, such as doping strategies, surface functionalization, and hybridization, for next-generation devices with the merits of low power consumption, intelligence, and high-integration chips. This review provides an overview of the synthetic routes and fundamental properties of functional 2D MXene nanostructures, including surfacemodified 2D MXenes and mixed-dimensional MXene-based heterostructures, highlights the state-of-the-art progress in the applications of functional 2D MXene nanostructures with regard to energy storage and conversion, catalysis, sensors, photodetectors, EMI shielding, degradation, and biomedical applications, and presents the challenges and perspectives in these burgeoning fields. It is hoped that this review will inspire more efforts toward fundamental research on new functional 2D MXene-based devices to satisfy the growing requirements for next-generation systems.

The effective non‐precious metal catalysts toward the oxygen evolution reaction (OER) are highly desirable for electrochemical water splitting. Herein, we prepare a novel glass‐ceramic (Ni1.5Sn@triMPO4) by embedding crystalline Ni1.5Sn nanoparticles into amorphous trimetallic phosphate (triMPO4) matrix. This unique crystalline‐amorphous nanostructure synergistically accelerates the surface reconstruction to active Ni(Fe)OOH, due to the low vacancy formation energy of Sn in glass‐ceramic and high adsorption energy of PO43− at the VO sites. Compared to the control samples, this dual‐phase glass‐ceramic exhibits a remarkably lowered overpotential and boosted OER kinetics after surface reconstruction, rivaling most of state‐of‐the‐art electrocatalysts. The residual PO43− and intrinsic VO sites induce redistribution of electron states, thus optimizing the adsorption of OH* and OOH* intermediates on metal oxyhydroxides and promoting the OER activity.

Bismuth (Bi), as a nontoxic and inexpensive diamagnetic heavy metal, has recently been utilized for the preparation of a variety of nanomaterials, such as nanoparticles, nanowires, nanotubes, nanosheets, etc., with a tunable bandgap, unique structure, excellent physicochemical properties, and compositional features for versatile properties, such as near‐infrared absorbance, high X‐ray attenuation coefficient, excellent photothermal conversion efficiency, and a long circulation half‐life. These features have endowed mono‐elemental Bi nanomaterials with desirable performances for electronics/optoelectronics, energy storage and conversion, catalysis, nonlinear photonics, sensors, biomedical applications, etc. This review summarizes the controlled synthesis of mono‐elemental Bi nanomaterials with different shapes and sizes, highlights the state‐of‐the‐art progress of the desired applications of mono‐elemental Bi nanomaterials, and presents some personal insights on the challenges and future opportunities in this research area. It is hoped that the controllable manipulation techniques of Bi nanomaterials, along with their unique properties, can shed light on the next‐generation devices based on Bi nanostructures and Bi‐related nanomaterials.

It is of great significance and importance to explore a mild, clean, and highly efficient universal approach for the synthesis of graphene quantum dots. Herein, we introduced a new green, rapid, and universal preparation approach for graphene quantum dots via the free-radical polymerization of oxygen-containing aromatic compounds under ultraviolet irradiation. This approach had a high yield (86%), and the byproducts are only HO and CO. The obtained graphene quantum dots were well-crystallized and showed remarkable optical and biological properties. The colorful, different-sized graphene quantum dots can be used in fluorescent bioimaging in vitro and in vivo. This approach is suitable not only for the preparation of graphene quantum dots but also for heteroatom-doped graphene quantum dots.

The controlled integration of plasmonic nanoparticles with metal–organic frameworks (MOFs) creates a class of multifunctional nanomaterials that are powerful for various applications, especially in the fields of photocatalysis and photoelectrocatalysis, which recently have witnessed vast interest in the exploration of the localized surface plasmon resonance of plasmonic nanoparticles (NPs) to improve the efficiency of catalysis processes. This Perspective highlights and summarizes recent significant progress in the field of catalysis, focusing on integration strategies and considerations and several possible plasmonic enhancement mechanisms involved. Brief overviews of the optical and electronics properties of plasmonic NPs are also introduced; finally, the development prospect of the field is briefly discussed.

AbstractMXene as a novel two-dimensional (2D) material exhibits a lot of advantages in nonlinear optics. However, the common MXene, Ti3C2Tx and Ti2CTx nanosheets, easily suffer from degradation under ambient conditions, greatly limiting their practical applications. Here, we demonstrated one of MXene compounds, V2CTx, which has a strong modulation depth (nearly 50%), can serve as an excellent saturable absorber (SA) in passively mode-locked (PML) fiber lasers. More importantly, 206th harmonic order has been successfully generated in Er-doped mode-locked fiber laser, exhibiting maximum repetition rate of 1.01 GHz and pulse duration of 940 fs, which to the best of our knowledge, is the highest harmonic mode-locked fiber laser from the MXene SA so far. In addition, the high harmonic order mode-locked operation can maintain at least 24 h without any noticeable change, suggesting MXene V2CTx nanosheets have excellent stability in this mode-locked fiber laser. It is anticipated that the present work can pave the way to new design for MXene-based heterostructures for high-performance harmonic mode-locked lasers.

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