Two-Dimensional Tellurium:Progress,Challenges,and Prospects

Since the successful fabrication of two-dimensional(2D)tellurium(Te)in 2017,its fascinating properties including a thickness dependence bandgap,environmental stability,piezoelectric effect,high carrier mobility,and photoresponse among others show great potential for various applications.These include photodetectors,field-effect transistors,piezoelectric devices,modulators,and energy harvesting devices.However,as a new member of the 2D material family,much less known is about 2D Te compared to other 2D materials.Motivated by this lack of knowledge,we review the recent progress of research into 2D Te nanoflakes.Firstly,we introduce the background and motivation of this review.Then,the crystal structures and synthesis methods are presented,followed by an introduction to their physical properties and applications.Finally,the challenges and further development directions are summarized.We believe that milestone investigations of 2D Te nanoflakes will emerge soon,which will bring about great industrial revelations in 2D materials-based nanodevice commercialization.

Recent Progress,Challenges,and Prospects in Two‑Dimensional Photo‑Catalyst Materials and Environmental Remediation

The successful photo-catalyst library gives significant information on feature that affects photo-catalytic performance and proposes new materials.Competency is considerably significant to form multi-functional photo-catalysts with flexible characteristics.Since recently,two-dimensional materials(2DMs)gained much attention from researchers,due to their unique thickness-dependent uses,mainly for photo-catalytic,outstanding chemical and physical properties.Photo-catalytic water splitting and hydrogen(H2)evolution by plentiful compounds as electron(e−)donors is estimated to participate in constructing clean method for solar H2-formation.Heterogeneous photocatalysis received much research attention caused by their applications to tackle numerous energy and environmental issues.This broad review explains progress regarding 2DMs,significance in structure,and catalytic results.We will discuss in detail current progresses of approaches for adjusting 2DMs-based photo-catalysts to assess their photo-activity including doping,hetero-structure scheme,and functional formation assembly.Suggested plans,e.g.,doping and sensitization of semiconducting 2DMs,increasing electrical conductance,improving catalytic active sites,strengthening interface coupling in semiconductors(SCs)2DMs,forming nano-structures,building multi-junction nano-composites,increasing photo-stability of SCs,and using combined results of adapted approaches,are summed up.Hence,to further improve 2DMs photo-catalyst properties,hetero-structure design-based 2DMs’photo-catalyst basic mechanism is also reviewed.

Low Temperature Synthesis of Nano Porous 12CaO?7Al_2O_3 Powder by Hydrothermal Method

Single-phase insulating 12CaO？7Al_2O_3（C12A7） powder was synthesized using an optimized hydrothermal method. Pure phase of C12A7 was got at a comparatively lower temperature（c.a. 300 ℃） than that has been previously reported. The crystallite size of the synthesized C12A7 powder was 7±2 nm. The surface area values calculated for all the samples at a synthesis temperature range of 250-800 ℃ for 5 h were in the range of about 19-24 m^2/g, with pore sizes of 12-20 nm. This low-temperature-based synthetic strategy along with nano porous structures and a high surface area value can facilitate catalyst application.

Tunable narrowband antireflection optical filter with a metasurface

A narrowband tunable antireflection optical filter is proposed and numerically studied. The structure is a metasurface based on plasmonic nanoparticles on an electro-optic film in a three-layer configuration of metaldielectric-metal(MDM) in the visible near-infrared range. By tuning the voltage and thus tuning the refractive index of the dielectric Li Nb O_3, one can shift the wavelength of minimum reflection as desired. The parameters of gold nanoparticles and other elements used for the filter design and refractive index of the dielectric are obtained by the finite-element method(FEM). An analytical theory is presented to explain the FEM simulation results, and they agree well with each other. It is found that the frequency of the plasmonic resonance wave on the metasurface should be equal to that of the Fabry–Perot resonator formed by the MDM to have a good filtering property. Theoretical spectra obtained by FEM simulation show that the structure has extensive potential for the design of tunable narrow-band filters for modulators, displayers, and color extraction for imaging.

Emerging monoelemental 2D materials(Xenes)for biosensor applications

Currently,numerous monoelemental two-dimensional(2D)materials,called Xenes,have been discovered,including graphyne(GD),silicene,germanene,arsenene,borophene.Their structures,fabrication methods,as well as properties have been extensively explored.Based on their single-element composition,high optical response capability,excellent electrical-optical properties,large specific surface area(SSA)and easy modification,Xenes have been widely used in photoelectric applications(detection,modulation,light processing)and biomedicine(biological sensing,drug loading,bioimaging,etc.).Especially in the field of biomedicine,Xenes are expected to induce a great breakthrough.In this review,we introduce the structural characteristics,synthesis and modification methods of several common Xenes respectively.The general properties including optical,electronic,physical and chemical properties of Xenes are summarized.Their diverse utilization as biosensors for nucleic acid sequencing,bioactive detection,cancer diagnosis,etc.are also explicitly explored.Finally,the challenges and future perspectives of Xenes in biosensor are discussed.

Two-dimensional selenium and its composites for device applications

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.