Efficient Preparation and Characterization of Functional Graphene with Versatile Applicability

Graphene,as star versatile materials having extraordinarily high electric conductivity,electron mobility,thermal conductivity,thermal stability,optical transparency,and mechanical strength,has attracted much attention from scientists and engineers in the field of materials,chemistry,physics,energy,and environment in the last decade and achieved fruitful accomplishment.This review discusses preparation strategies,functionality,characterization,and applications for two dimensional nanosheet and quasi-onedimensional nanoribbon of graphene through direct exfoliation of graphite,chemical vapor deposition of hydrocarbon,laser-induced direct synthesis of graphene,laser etched graphene oxide in the dry state without the use of toxic reducing agent hydrazine,unzipping carbon nanotube,and polycondensation of polycyclic aromatics on the basis of 178 representative references mostly in 2015.The stabilization of graphene oxide prepared in chemical preparation in " top-down" is emphasized.Several vital classic methods of characterizing molecular structure,C/O ratio,defect,morphology,single-or few-layered( 2 to 10 layers) structure,porous and hollow structures,including Raman spectroscopy,AFM,SEM,TEM,STM,electron diffraction,X-ray diffraction,and X-ray photoelectron spectroscopy are systematically introduced.Because graphene possesses novel incomparable multifunctionalities,its versatile applications as novel conducting additives,reinforcing filler,separation membrane,sensor,anticorrosive coating,catalyst,electromagnetic shield,lubricant,and flexible electrode materials in electrochemical and electronic devices,including photovoltaic cells,supercapacitors,rechargeable batteries,sensors,field effect transistors,light emitting diodes,separation membranes,adsorbents and absorbents,catalysts,electro-optic modulator,terahertz emitter and detector,and semiconductors,have been mentioned.Especially in the aspect of both high performance and cost-effectiveness,graphene is expected to be even superior to the expensive carbon nanotubes.

Morphology-controlled Tantalum Diselenide Structures as Self-optimizing Hydrogen Evolution Catalysts

Metallic layered transition metal dichalcogenides(TMDs)nanomaterials based on Group 5 transition metals are attracting substantial interests as alternative catalysts for hydrogen evolution reaction(HER).However,controllable preparation of tantalum diselenide(TaSe2)remains challenging,which has hindered the exploration on its application in HER.Herein,we develop a facile method named surface-assisted chemical vapor transport(SACVT)for controllable synthesis of TaSe2 plates and nanobelts,by regulating the molar ratio of selenium to tantalum and reaction temperature.Unique quasi-arrays and self-supported structure help TaSe2 nanobelt own more active sites and higher ability of charge transfer,so it is superior to TaSe2 plate in electrocatalytic HER.Interestingly,they both exhibit the ability to optimize their morphologies upon cycling for dramatically improved and robust electrocatalytic performance.The selfoptimized structures can increase the effective active surface by exposing more active sites on the basal-planes and edges,shorten the interlayer electron-transfer pathways at a thinned domain,and accelerate the charge transfer,which mainly derive from high basal-plane activity and weak interaction between layers of metallic TaSe2.This work provides a reliable way for controllable synthesis of different TaSe2 structures,motivating further efforts to explore new high-efficiency catalysts in the large family of metallic TMDs for electrochemical energy conversion.

Single-atom alloys prepared by two-step thermal evaporation

Single-atom alloys(SAAs)have gained significant attention due to their remarkable atomic utilization efficiency,interactions between single atoms(SAs)and metal supports,and free-atom-like electronic structure of dopant elements.In this work,we observed the formation of SAs in pre-deposited metal particles by a two-step thermal evaporation technique,thereby establishing the first instance of discovering SAAs by thermal evaporation.The discovery of SAAs by thermal evaporation extends the range of SAAs preparation methods to include this traditional synthetic technique,which offers convenience,cost-efficiency,and universality.The formation mechanism of SAAs prepared using this technique was elucidated by density functional theory calculations.It was demonstrated that thermal evaporation can be utilized to prepare SAAs with multiple SAs,further highlighting its universal applicability.

A highly efficient Fe-doped Ni_(3)S_(2) electrocatalyst for overall water splitting

The development of efficient and stable electrocatalysts with earth-abundant elements for both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)in the same electrolyte is incontrovertibly vital in water electrolysis.However,their large-scale fabrication remains a great challenge.Here,we report a self-supported electrocatalyst in the form of Fe-doped Ni_(3)S_(2) nanoparticles in-situ grown on three-dimensional(3D)conductive Fe−Ni alloy foam(Fe−Ni_(3)S_(2)/AF)by surface-assisted chemical vapor transport(SACVT)method.Homogeneous growth environment and scalability of SACVT method allow Fe−Ni3S2 nanoparticles uniformly growing on AF in large-scale.Fe−Ni_(3)S_(2)/AF exhibits high activity and durability when act as HER catalyst and OER precatalyst in alkaline media.The HER and OER overpotential at 10 mA/cm^(2) is considerably small,only 75 and 267 mV,respectively.Moreover,the electrolyzer assembled by Fe−Ni_(3)S_(2)/AF for overall water splitting exhibits a low cell voltage and high durability in long-term test.Based on experiments and theoretical calculation,the significantly enhanced activity could be originated from the incorporation of Fe,which contributed to increase the electrochemical active surface area,enhance electrical conductivity,optimize the hydrogen and H2O adsorption energy of Ni_(3)S_(2)(101)surface in HER,and form active bimetallic Ni−Fe(oxy)hydroxide in OER.The excellent durability of self-supported Fe−Ni_(3)S_(2)/AF could be benefited from the in-situ growth of Fe−Ni_(3)S_(2) nanoparticles on 3D AF,which could ensure closely mechanical adhesion between active materials and substrate,promote charge transport and increase surface area.This work provides a facile method for large-scale synthesis of electrocatalysts with high activity and long-term durability for efficient water electrolysis in alkaline media.

Hydrophobic ionic liquid-in-polymer composites for ultrafast,linear response and highly sensitive humidity sensing

Traditional ionic liquids are sensitive to humidity but with long response time and nonlinear response.Pure liquid-state ionic liquids are usually hard for dehydration which have ultralong response time for humidity sensing.The immobilization of ionic liquids provide a possible way for high performance humidity sensing.Hydrophobic materials and structures also promised faster response in humidity sensing,because of easier desorption of water.In this work,we prepared flexible humidity sensitive composites based on hydrophobic ionic liquid and polymer.The combination of hydrophobic ionic liquid with hydrophobic polymer realized linear response,high sensitivity with low hysteresis to humidity.By adjusting the ratio of ionic liquid,not only the impedance but also the hydrophobicity of composite could be modulated,which had a significant influence on the humidity sensing performance.The morphology and microstructure of the material also affected its interaction with water molecules.Due to the diverse processing methods of polymer,highly transparent film fabricated by spinning-coating and nanofibrous membrane fabricated by electrospinning could be prepared and exhibited different response time,which could be used for different application scenarios.Especially,the fibrous membrane made with electrospinning method showed an ultrafast response and could distinguish up to 120 Hz humidity change,due to its fibrous structure with high specific surface area.The humidity sensors with ultrafast,linear response and high sensitivity showed potential applications in human respiratory monitoring and flexible non-contact switch.To better show the multifunction of ionic liquid-polymer composite,as a proof of concept,we fabricated an integrated humidity sensitive color change device by utilizing lower ionic liquid content composite for sensing in the humidity sensing module and higher ionic liquid content composite as the electrolyte in the electrochromic module.

High-quality bilayer graphene grown on softened copper foils by atmospheric pressure chemical vapor deposition

Bilayer graphene(BLG)shows great application prospect and potential in next-generation electronics because of its unique electrical and mechanical properties.However,the scalable synthesis of large-area high-quality BLG films is still a great challenge,despite the maturity of chemical vapor deposition(CVD)technique.In this study,we report a robust method to grow BLGs on flat,softened Cu foils by atmospheric pressure CVD.A moderate amount of residual oxygen accelerates the growth of BLG domains while suppressing the formation of multilayers.Raising the nucleation density at low hydrogen pressure efficiently increases the film continuity.Based on the optimized CVD process,the growth of graphene films on 4×4 cm^2 Cu foils with an average BLG coverage of 76%is achieved.The morphology and structure characterizations demonstrate a high quality of the BLG.Dual gate field-effect transistors are investigated based on AB-stacked BLG,with a tunable bandgap and high carrier mobility of up to 6790 cm2 V^−1 s^−1 at room temperature.

Determining the nuclear temperature dependence on source neutron-proton asymmetry in heavy-ion reactions at intermediate energy

In this article,we investigate the dependence of nuclear temperature on emitting source neutron-proton(N/Z)asymmetry with light charged particles(LCPs)and intermediate mass fragments(IMFs)generated from intermediate-velocity sources in thirteen reaction systems with different N/Z asymmetries,^(64)Zn on^(112)Sn,and^(70)Zn,^(64)Ni on^(112,124)Sn,^(58,64)Ni,^(197)Au,and^(232)Th at 40 MeV/nucleon.The apparent temperature values of LCPs and IMFs from different systems are deduced from the measured yields using two helium-related and eight carbon-related double isotope ratio thermometers,respectively.Then,the sequential decay effect on the experimental apparent temperature deduction with the double isotope ratio thermometers is quantitatively corrected explicitly with the aid of the quantum statistical model.The present treatment is an improvement compared to our previous studies in which an indirect method was adopted to qualitatively consider the sequential decay effect.A negligible N/Z asymmetry dependence of the real temperature after the correction is quantitatively addressed in heavy-ion reactions at the present intermediate energy,where a change of o.1 units in source N/Z asymmetry corresponds to an absolute change in temperature of an order of 0.03 to 0.29 MeV on average for LCPs and IMFs.This conclusion is in close agreement with that inferred qualitatively via the indirect method in our previous studies.

β-decay study of neutron-rich nucleus ^(34)Al

The ＂island of inversion＂ has been known for over a quar- ter century, since Warburton et al. [1] proposed that nuclei with intruder ground states would constitute a 3x3 square with Z=10-12, N=20-22 in 1990. Uncovering the underlying inversion mechanism and exploring the scope of the island have attracted significant theoretical and experimental efforts in the following years. Now it is well known that the reduction of N=20 shell gap, which is likely caused by the strong nucleon-nucleon tensor interaction [2-5], allows the intrusion of neutron orbits from the pf shell into the sd shell and results in the inversion of the 2p-2h intruder and 0p-0h normal con- figurations of the nuclear ground states in this region. Mean- while, the original border of the ＂island of inversion＂ has been extended greatly [6-14].