Facile electrochemical surface-alloying and etching of Au wires to enable high-performance substrates for surface enhanced Raman scattering

Surface-enhanced Raman Spectroscopy(SERS)is a nondestructive technique for rapid detection of analytes even at the single-molecule level.However,highly sensitive and reliable SERS substrates are mostly fabricated with complex nanofabrication techniques,greatly restricting their practical applications.A convenient electrochemical method for transforming the surface of commercial gold wires/foils into silver-alloyed nanostructures is demonstrated in this report.Au substrates are treated with repetitive anodic and cathodic bias in an electrolyte of thiourea,in a one-pot one-step manner.X-rays absorption fine structure(XAFS)spectroscopy confirms that the AuAg alloy is induced at the surface.The unique AuAg alloyed surface nanostructures are particularly advantageous when served as SERS substrates,enabling a remarkably sensitive detection of Rhodamine B(a detection limit of 10^(-14)M,and uniform strong response throughout the substrates at 10^(-12)M).

Recent Advances of Graphitic Carbon Nitride-Based Structures and Applications in Catalyst, Sensing, Imaging, and LEDs

The graphitic carbon nitride(g-C_3N_4) which is a two-dimensional conjugated polymer has drawn broad interdisciplinary attention as a low-cost, metal-free, and visible-light-responsive photocatalyst in the area of environmental remediation. The g-C_3N_4-based materials have excellent electronic band structures, electron-rich properties, basic surface functionalities, high physicochemical stabilities and are ‘‘earth-abundant.'' This review summarizes the latest progress related to the design and construction of g-C_3N_4-based materials and their applications including catalysis, sensing,imaging, and white-light-emitting diodes. An outlook on possible further developments in g-C_3N_4-based research for emerging properties and applications is also included.

Study of Phase Transition Properties in Epitaxial Ferroelectric Film

Based on the transverse Ising model and using decoupling approximation to the Fermi-type Green'sfunction, we study the phase transition properties of the epitaxial ferroelectric film with one substrate.A generalrecursive equation of the ferroelectric thin film with two n-layer materials is obtained, which enables us to study thephase transition properties for any number layers for epitaxial ferroelectric thin film.With the help of this equation,we analyze the effect of the exchange interaction and the transverse field in the phase diagram, the influence to thepolarizations and Curie temperature numerically.The results show that epitaxial ferroelectric film are able to inducea strong increase or decrease of Curie temperature to different exchange interactions and transverse fields within theepitaxial film layers.The theoretical results are in reasonable accordance with experimental data of different ferroelectricthin film.

Construction of a cement-rebar nanoarchitecture for a solution-processed and flexible film of a Bi_(2)Te_(3)/CNT hybrid toward low thermal conductivity and high thermoelectric performance

Solution processability and flexibility still remain major challenges for many thermoelectric(TE)materials,including bismuth telluride(Bi_(2)Te_(3)),a typical and commercially available TE material.Here,we report a new solutionprocessed method to prepare a flexible film of a Bi_(2)Te_(3)/single-walled carbon nanotube(SWCNT)hybrid,where the dissolved Bi_(2)Te_(3) ion precursors are mixed with dispersed SWCNTs in solution and recrystallized on the SWCNT surfaces to form a“cement-rebar”-like architecture.The hybrid film shows an n-type characteristic,with a stable Seebeck coefficient of^(−1)00.00±1.69μVK^(−1) in air.Furthermore,an extremely low in-plane thermal conductivity of∼0.33Wm^(−1) K^(−1) is achieved at 300 K,and the figure of merit(ZT)reaches 0.47±0.02.In addition,the TE performance is independent of mechanical bending.The unique“cement-rebar”-like architecture is believed to be responsible for the excellent TE performances and the high flexibility.The results provide a new avenue for the fabrication of solution-processable and flexible TE hybrid films and will speed up the applications of flexible electronics and energy conversion.

Air-Stable Ultrabright Inverted Organic Light-Emitting Devices with Metal Ion-Chelated Polymer Injection Layer

Here,this work presents an air-stable ultrabright inverted organic lightemitting device(OLED)by using zinc ionchelated polyethylenimine(PEI)as electron injection layer.The zinc chelation is demonstrated to increase the conductivity of the PEI by three orders of magnitude and passivate the polar amine groups.With these physicochemical properties,the inverted OLED shows a record-high external quantum efficiency of 10.0% at a high brightness of 45,610 cd m^(-2) and can deliver a maximum brightness of 121,865 cd m^(-2).Besides,the inverted OLED is also demonstrated to possess an excellent air stability(humidity,35%)with a half-brightness operating time of 541 h@1000 cd m^(-2) without any protection nor encapsulation.

Electrochemical detection of methyl-paraoxon based on bifunctional cerium oxide nanozyme with catalytic activity and signal amplification effect

A new electrochemical sensor for organophosphate pesticide(methyl-paraoxon)detection based on bifunctional cerium oxide(CeO_(2))nanozyme is here reported for the first time.Methyl-paraoxon was degraded into p-nitrophenol by using CeO_(2) with phosphatase mimicking activity.The CeO_(2) nanozymemodified electrode was then synthesized to detect p-nitrophenol.Cyclic voltammetry was applied to investigate the electrochemical behavior of the modified electrode,which indicates that the signal enhancement effect may attribute to the coating of CeO_(2) nanozyme.The current research also studied and discussed the main parameters affecting the analytical signal,including accumulation potential,accumulation time,and pH.Under the optimum conditions,the present method provided a wider linear range from 0.1 to 100 mmol/L for methyl-paraoxon with a detection limit of 0.06 mmol/L.To validate the proof of concept,the electrochemical sensor was then successfully applied for the determination of methyl-paraoxon in three herb samples,i.e.,Coix lacryma-jobi,Adenophora stricta and Semen nelumbinis.Our findings may provide new insights into the application of bifunctional nanozyme in electrochemical detection of organophosphorus pesticide.

Tunable ultrathin dual-phase P-doped Bi_(2)MoO_(6) nanosheets for advanced lithium and sodium storage

The construction of electrode materials for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)has gradually been an appealing and attractive technology in energy storage research field.In the present work,a facile strategy of synthesizing ultrathin amorphous/nanocrystal dual-phase P-doped Bi_(2)MoO_(6)(denoted as P-BiMO)nanosheets via a one-step wet-chemical synthesis approach is explored.Quite distinct from conventional two-dimensional(2D)nanosheets,our newly developed ultrathin P-BiMO nanosheets exhibit a unique tunable amorphous/nanocrystalline dual-phase structure with several compelling advantages including fast ion exchange ability and superb volume change buffer capability.The experimental results reveal that our prepared P-BiMO-6 electrode delivers an excellent reversible capacity of 509.6 mA·g^(−1) after continuous 1,500 cycles at the current densities of 1,500 mA·g^(−1) and improved rate performance for LIBs.In the meanwhile,the P-BiMO-6 electrode also shows a reversible capacity of 300.6 mA·g^(−1) after 100 cycles at 50 mA·g^(−1) when being used as the SIBs electrodes.This present work uncovers an effective dual-phase nanosheet structure to improve the performance of batteries,providing an attractive paradigm to develop superior electrode materials.

Growth of Tellurium Nanobelts on h-BN for p-type Transistors with Ultrahigh Hole Mobility

The lack of stable p-type van der Waals(vdW)semiconductors with high hole mobility severely impedes the step of low-dimensional materials entering the industrial circle.Although p-type black phosphorus(bP)and tellurium(Te)have shown promising hole mobilities,the instability under ambient conditions of bP and relatively low hole mobility of Te remain as daunting issues.Here we report the growth of high-quality Te nanobelts on atomically flat hexagonal boron nitride(h-BN)for high-performance p-type field-effect transistors(FETs).Importantly,the Te-based FET exhibits an ultrahigh hole mobility up to 1370 cm^(2) V^(−1) s^(−1) at room temperature,that may lay the foundation for the future high-performance p-type 2D FET and metal-oxide-semiconductor(p-MOS)inverter.The vdW h-BN dielectric substrate not only provides an ultra-flat surface without dangling bonds for growth of high-quality Te nanobelts,but also reduces the scattering centers at the interface between the channel material and the dielectric layer,thus resulting in the ultrahigh hole mobility.

Recent Advances in Covalent Organic Framework Electrode Materials for Alkali Metal-Ion Batteries

Owing to the shortcomings of traditional electrode materials in alkalimetal-ion batteries(AIBs),such as limited reversible specific capacity,low power density,and poor cycling performance,it is particularly important to develop new electrode materials.Covalent organic frameworks(COFs)are crystalline porous polymers that incorporate organic building blocks into their periodic structures through dynamic covalent bonds.COFs are superior to organic materials because of their high designability,regular channels,and stable topology.Since the first report of D_(TP)-A_(NDI)-COF as a cathode material for lithium-ion batteries in 2015,research on COF electrode materials has made continuous progress and breakthroughs.This review briefly introduces the characteristics and current challenges associated with COF electrode materials.Furthermore,we summarize the basic reaction types and active sites according to the categories of covalent bonds,including B–O,C=N,C–N,and C=C.Finally,we emphasize the perspectives on basic structure and morphology design,dimension and size design,and conductivity improvement of COFs based on the latest progress in AIBs.We believe that this review provides important guidelines for the development of high-efficiency COF electrode materials and devices for AIBs.

Mechanical and thermodynamical stability of BiVO4 polymorphs using first-principles study

First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and Mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.

Ionic covalent organic frameworks with tailored anionic redox chemistry and selective ion transport for high-performance Na-ion cathodes

Employing cathode materials with multiple redox couples and electrolytes with efficient cation transport kinetics are two effective approaches to improving the electrochemical performance of batteries.In this work,for the first time,we present a design strategy of simultaneously realizing reversible cationic and anionic redox chemistries as well as selective anion/cation transport in the viologen-based COFs(BAVCOF:X,coordinated anions of X=Cl^(-),Br^(-),I^(-),and ClO_(4)^(-))for high-performance Na-ion cathodes.Besides the cationic redox of viologen segments,the different redox activities of anions effectively tune the total capacities of the COFs.Meanwhile,electrochemical analysis and ab-initial molecular dynamics(AIMD)calculation illustrate that the anion/cation transport kinetics of electrolytes caged in the COFs'channels can be selectively tuned by the coordinated anions.As a result,combining high-potential Br-/Br_(2)redox couple,cationic redox of viologen segments,and enhanced Na+transport kinetics,the BAV-COF:Brdemonstrates stable performance with energy densities of 358.7 and 145.2 Wh kg^(-1)at power densities of 116.5 and 2124.1 W kg^(-1),respectively.This study offers new insight into the fabrication of organic cathodes with anionic redox and the advantages of COFs electrode materials in anion/cation transport selectivity for energy storage applications.

An Optical Investigation of Silver Nanoclusters Composite Soda-lime Glass Formed by Electric Field Assisted Diffusion

Silver nanoclusters（NCs） embedded in soda-lime glass was synthesized by the electric fieldassisted diffusion（EFAD） and successive annealing. The samples were characterized by UV-Vis absorption spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy（XPS）, and lifetime measurements. The experimental results show that the growth of silver clusters is favored by the annealing temperature and dwell time. The as-diffused and annealed glass samples show photoluminescence around 550 nm under UV excitation, which can be associated with the presence of L-center and Ag3~＋ cluster. And the increasing of the annealing temperature and dwell time results in an appearance of the SPR peak and the decreasing of the luminescence intensities because the Ag3~＋ clusters grow up into the Ag nanoparticles.

Recent advances in two-dimensional nanomaterials for bone tissue engineering

Over the last decades,bone tissue engineering has increasingly become a research focus in the field of biomedical engineering,in which biomaterials play an important role because they can provide both biomechanical support and osteogenic microenvironment in the process of bone regeneration.Among these biomaterials,two-dimensional(2D)nanomaterials have recently attracted considerable interest owing to their fantastic physicochemical and biological properties including great biocompatibility,excellent osteogenic capability,large specific surface area,and outstanding drug loading capacity.In this review,we summarize the state-of-the-art advances in 2D nanomaterials for bone tissue engineering.Firstly,we introduce the most explored biomaterials used in bone tissue engineering and their advantages.We then highlight the advances of cutting-edge 2D nanomaterials such as graphene and its derivatives,layered double hydroxides,black phosphorus,transition metal dichalcogenides,montmorillonite,hexagonal boron nitride,graphite phase carbon nitride,and transition metal carbonitrides(MXenes)used in bone tissue engineering.Finally,the current challenges and future prospects of 2D nanomaterials for bone tissue regeneration in process of clinical translation are discussed.

Influence of High Atomic Hydrogenation on the Electronic Structure of Zigzag Carbon Nanotubes： A First-Principles Study

Using density functional theory, we study high hydrogenated zigzag single-walled carbon nanotubes from （7,0） to （11,0）. Two structure transitions are classified： type A is a metallic transition and type B is a ＂semiconductive transition＂ according to the energy band structure. The charge density transforms only at the C-C bonds without hydrogenated sites. The sp^3 hybridization is mainly enhanced for all the C-C bonds in the vertical axial direction for type-A configurations, and the sp^3 hybridization mainly increases for all C-C bonds along the axial direction for the type-B case.

Anion-hosting cathodes for current and late-stage dual-ion batteries

Anion-hosting cathodes capable of reversibly storing large-size anions play a leading role in dual-ion batteries(DIBs). The purpose of the present review is to summarize the most promising anion-hosting cathodes for current and late-stage DIBs. This review first summarizes the developments in conventional graphite cathodes, especially the latest advances in the graphiterelated research. Next, organic cathodes for the anion storage are discussed, including aromatic amine polymers, heterocyclic polymers, bipolar compounds, and all-carbon-unsaturated compounds. Then, the review focuses on the conversion-type cathodes with high theoretical specific capacities. Finally, the future research directions of the cathodes of DIBs are proposed.

Covalent organic framework containing dual redox centers as an efficient anode in Li-ion batteries

Covalent organic frameworks(COFs)with periodic channels and tunable chemical structures have been widely considered as promising electrode materials in rechargeable batteries.However,the design and construction of high-performance COFs-based electrodes still face some challenges in the introduction of multiple efficient redox centers as well as the reduction of dead mass.To address these issues,a unique COF containing double active centers(C═N and N═N)is developed as an anode in rechargeable lithium-ion batteries(LIBs).The as-prepared COF displays excellent electrochemical performance due to its remarkable structural stability and the existence of many active groups.Meanwhile,its electrochemical performance is significantly better than that of the small molecule compound or the linear polymer with the same construction units.Even at a high current density of 5 A/g,the LIBs with COF electrodes remain at a high discharge capacity of 227 mAh/g after 2000 cycles.Moreover,the distinction in electrochemical performances of these three materials is further revealed by calculation.This study illustrates the importance of molecular structure design for improving the performance of organic electrodes.

Vapor phase epitaxy of PbS single-crystal films on water-soluble substrates and application to photodetectors

Lead sulfide(PbS),a typical functional semiconductor material,has attracted serious attention due to its great potential in optoelectronics applications.However,controllable growth of PbS single-crystal film still remains a great challenge.Here,we report heteroepitaxial growth of large-scale highly crystalline PbS films on alkali salt(NaCl and KCl)substrates via chemical vapor deposition(CVD).Structural characterizations demonstrate that the as-grown PbS films exhibit an atomically sharp interface with the underlying substrates.The epitaxial relationships between the epilayers and substrates were determined to be PbS(100)//NaCl(100)or KCl(100),PbS[010]//NaCl[010]or KCl[010].Owing to the high solubility of alkali salt,the epitaxial PbS films can be rapidly released from the underlying substrates and transferred to other substrates of interest while maintaining good integrity and crystallinity,the process of which is particularly attractive in the fields of electronics and optoelectronics.Furthermore,photodetectors based on the transferred PbS films were fabricated,exhibiting a high photoresponsivity of 7.5 A/W,a detectivity of 1.44×10^(12)Jones,and a rapid response time of approximately 0.25 s.This work sheds light on the batch production,green transfer,and optoelectronic application of PbS films.

Recent advances on electrochemical methods in fabricating two-dimensional organic-ligand-containing frameworks

Organic-ligand-containing frameworks have drawn considerable attention due to their multifunctional properties as well as tunable structures for broad applications.Among numerous synthesis methods developed in the past two decades,electrochemical processing has been demonstrated as one of the most efficient,safe,and facile ways to realize the large-scale and highly controllable production of organic-ligand-containing frameworks.In this review,the progress of electrochemically induced crystallization and thin film fabrication of organic-ligand-containing frameworks is summarized in a well-rounded way.Besides,the mechanism and processing parameters are also discussed.Moreover,the main challenges are also expounded for providing some guidance on the future development of organic-ligand-containing frameworks,especially for covalent-organic frameworks and hydrogen-bonded organic frameworks.

Three-dimensional Ag/carbon nanotube-graphene foam for high performance dendrite free lithium/sodium metal anodes

Although lithium metal and sodium metal are promised as ideal anodes for lithium ion batteries(LIBs)and sodium ion batteries(SIBs),they still suffer from inevitable dendrite growth.In light of this,silver nanoparticles(Ag NPs)are sputtered onto three-dimensional carbon nanotube decorated graphene foam(3D CNT-GF)to construct superior 3D Ag/CNT-GF composite matrix for lithium metal anodes(LMAs)and sodium metal anodes(SMAs).With this design,lithiophilic/sodiophilic Ag NPs could provide favorable sites to guide Li/Na metal nucleation and growth,thus leading to low nucleation overpotentials,high Coulombic efficiency and long cycle performance.Accordingly,3D Ag/CNT-GF electrodes can stably cy-cle for 1000 and 750 cycles at 3 mA cm^(−2)with 1 mAh cm^(−2)for SMAs and LMAs,respectively.More attractively,it can also stably sustain 300 cycles(SMAs)and 500 cycles(LMAs)at a large current den-sity of 5 mA cm^(−2)with 1 mAh cm^(−2).The excellent electrochemical performance can be attributed to the lithiophilic/sodiophilic electrode surface,3D porous electrode structure and the dendrite-free mor-phology as demonstrated by ex-situ scanning electron microscopy(SEM)and in-situ optical microscopy analyses.Furthermore,full cells based on Na@3D Ag/CNT-GF||Na 3 V 2(PO 4)3@carbon(NVP@C)and Li@3D Ag/CNT-GF||LiFePO 4(LFP)could deliver highly reversible capacities of 90.1 and 106.4 mAh g^(−1),respec-tively,at 100 mA g^(−1)after 200 cycles for SIBs and LIBs,respectively.This work demonstrates a novel 3D Ag/CNT-GF matrix for boosting Li/Na deposition stability for their future applications.

Size engineering of 2D MOF nanosheets for enhanced photodynamic antimicrobial therapy

Although porphyrin-based metal-organic frameworks(MOFs)have been widely explored as photosensitizers for photodynamic therapy,how the size will affect the light-induced catalytic activity for generation of reactive oxygen species(ROS)still remain unclear.Herein,we first report the size-controlled synthesis of two-dimensional(2D)porphyrin-based PCN-134 MOF nanosheets by a two-step solvothermal method to explore the size effect on its PDT performance,thus yielding enhanced photodynamic antimicrobial therapy.By simply controlling the reaction temperature in the synthesis process,the bulk PCN-134 crystal,large PCN-134(L-PCN-134)nanosheets with a lateral size of 2–3μm and thickness of 33.2–37.5 nm and small PCN-134 nanosheets(S-PCN-134)with a lateral size of 160–180 nm and thickness of 9.1–9.7 nm were successfully prepared.Interestingly,the S-PCN-134 nanosheets exhibit much higher photodynamic activity for ROS generation than that of the bulk 3D PCN-134 crystal and L-PCN-134 nanosheets under a660 nm laser irradiation,suggesting that the photodynamic activity of PCN-134 MOF increases when the size reduces.Therefore,the S-PCN-134 nanosheets show much enhanced performance when used as a photosensitizer for photodynamic antimicrobial activity and wound healing.