Design of(GO/TiO2)N one-dimensional photonic crystal photocatalysts with improved photocatalytic activity for tetracycline degradation

(GO/TiO2)N(GO represents graphene oxide,and N represents the period number of alternate superposition of two dielectrics)onedimensional photonic crystal with different lattice constants was prepared via the sol–gel technique,and its transmission characteristics for photocatalysis were tested.The results show that the lattice constant,filling ratio,number of periodic layers,and incident angle had effects on the band gap.When the lattice constant,filling ratio,number of periodic layers,and incident angle were set to 125 nm,0.45,21,and 0°,respectively,a gap width of 53 nm appeared at the central wavelength(322 nm).The absorption peak of the photocatalyst at 357 nm overlapped the blue edge of the photonic band gap.A slow photon effect region above 96%reflectivity appeared.The degradation rate of tetracycline in(GO/TiO2)N photonic crystal was enhanced to 64%within 60 min.Meanwhile,the degradation efficiency of(GO/TiO2)N one-dimensional photonic crystal was effectively improved compared with those of the GO/TiO2 composite film and GO/TiO2 powder.

Anti-oxidation characteristics of Cr-coating on surface of Ti-45Al-8.5Nb alloy by plasma surface metallurgy technique

TiAl-based alloys have received extensive attention recently due to their excellent properties. However, the weak oxidation resistance at temperatures higher than 800℃ can limit their further high-temperature structural applications.To improve the oxidation resistance of a high-Nb-content γ-TiAl alloy(Ti-45 Al-8.5 Nb, in units of at.%), a chromium(Cr)coating is prepared by using the plasma surface alloying technique, separately, at 800℃ and 1000℃. The x-ray diffraction(XRD) patterns reveal that an oxide surface layer consisting of Cr2O3, Al2O3, and TiO2 is produced on the Cr-coated Nb containing γ-TiAl substrates during the initial oxidation. However, the Cr2O3 is dominated in the oxide surface layer after being isothermally oxidized for 300 h. The oxidation kinetic curves are composed of a parabolic law stage(≤ 90 h) and a biquadratic law stage(≥ 90 h), fit by weight–gain curves. Due to diffusion in the fabrication process and oxidation process,the Cr-coated specimens have an adhesion force after being isothermally oxidized, specifically 69 N for a specimen after oxidation for 300 h. These results demonstrate that the Cr coating enhances the oxidation resistance and adhesion of a Ti-45 Al-8.5 Nb alloy, which may provide a new feasible scheme for designing oxidation protection layers.

Structure and tribological properties of Si/a-C:H(Ag)multilayer film in stimulated body fluid

Si/a-C:H(Ag)multilayer films with different modulation periods are prepared to test their potential applications in human body.The composition,microstructure,mechanical and tribological properties in the simulated body fluid are investigated.The results show the concentration of Ag first decreases and then increases with the modulation period decreasing from 984 nm to 250 nm.Whereas the C content has an opposite variation trend.Notably,the concentration of Ag plays a more important role than the modulation period in the properties of the multilayer film.The a-C:H sublayer of the film with an appropriate Ag concentration(8.97 at.%)(modulation period of 512 nm)maintains the highest sp3/sp2 ratio,surface roughness and hardness,and excellent tribological property in the stimulated body fluid.An appropriate number of Ag atoms and size of Ag atom allow the Ag atoms to easily enter into the contact interface for load bearing and lubricating.This work proves that the Ag nanoparticles in the a-C:H sublayer plays a more important role in the tribological properties of the composite-multilayer film in stimulated body fluid condition.

Effect of metal nanoparticle doping concentration on surface morphology and field emission properties of nano-diamond films

Nano-diamond particles are co-deposited on Ti substrates with metal(Ti/Ni) nanoparticles(NPs) by the electrophoretic deposition(EPD) method combined with a furnace annealing at 800℃ under N_(2) atmosphere. Modifications of structural and electron field emission(EFE) properties of the metal-doped films are investigated with different metal NPs concentrations. Our results show that the surface characteristics and EFE performances of the samples are first enhanced and then reduced with metal NPs concentration increasing. Both the Ti-doped and Ni-doped nano-diamond composite films exhibit optimal EFE and microstructural performances when the doping quantity is 5 mg. Remarkably enhanced EFE properties with a low turn-on field of 1.38 V/μm and a high current density of 1.32 mA/cm^(2) at an applied field of 2.94 V/μm are achieved for Ni-doped nano-diamond films, and are superior to those for Ti-doped ones. The enhancement of the EFE properties for the Ti-doped films results from the formation of the TiC-network after annealing. However, the doping of electron-rich Ni NPs and formation of high conductive graphitic phase are considered to be the factor, which results in marvelous EFE properties for these Ni-doped nano-diamond films.

Intercalation mechanisms of lithium into graphitized needle cokes

A needle coke was graphitized at different heat treatment temperature (2 000℃ to 3 000℃). The electrochemical intercalation mechanism of Li into the graphitized coke has been studied in Li|1 mol·L 1 LiClO 4+ethylene carbonate/diethylene carbonate|graphite cells, using an in situ X Ray diffraction (XRD) technique.The study of Li C intercalation processes of the graphitized coke reveals that there are three major types of intercalation behavior.The first is uniformly intercalated at all Li C compounds in graphitized coke heated at 2 250℃;the second is obviously staging phenomenon during intercalation for the graphitized coke heated at 2 750℃; the third is cointercalation of solvated Li ion at high potential (>0.3V) and then lithium electrochemical intercalation at lower potential for that heated at 3 000℃, resulting in the decrease of capacity and efficiency of graphite negative electrode for lithium ion secondary battery.

Recent advances and trends of single-atom catalysts for proton exchange membrane fuel cell cathodes

Proton exchange membrane fuel cells(PEMFCs),which have the advantages of high-power density,zero emission,and low noise,are considered ideal electrochemical conversion systems for converting hydrogen(H2)and oxy-gen(O_(2))/air into electricity.However,the oxygen reduction reaction(ORR),which is accompanied by multiple electrons,results in voltage loss and low conversion efficiency of PEMFCs.Currently,PEMFCs mainly use high-load precious platinum(Pt)to promote the ORR process;however,the high cost of Pt hinders the widespread commercialization of PEMFCs.Over the past few years,metal-nitrogen-carbon single-atom catalysts(M-N-C SACs)have attracted considerable attention and have been recognized as potential Pt-based catalysts owing to their outstanding ORR activity.This review briefly introduces the components of PEMFCs.Second,we discuss the catalytic mechanisms of the M-N-C SACs for the ORR.Third,the latest advances in noble,non-noble,and heteroatom-doped M-N-C SACs used as ORR and PEMFCs cathode catalysts are systematically reviewed.In sum-mary,we have outlined the current challenges and proposed a future perspective of M-N-C SACs for PEMFCs cathodes.

Direct chemical vapor deposition growth of graphene on Ni particles using solid carbon sources

Graphene has attained a considerable amount of popularity as an attractive ultra-thin reinforcement for nickel(Ni)matrix composites in recent years.However,its excellent reinforcement efficiency is suffered from the agglomeration of graphene nanosheets in manufacturing process and the poor bonding strength of graphene with Ni matrix.To overcome these two problems,one of the efficient strategies is to in-situ grow graphene reinforcements on Ni particles for powder metallurgy.This work aims to synthesize uniform graphene@Ni composite particles by using polymethyl methacrylate(PMMA)as the solid sources for chemical vapor deposition(CVD)process.The results demonstrate that few-layer or multilayer graphene with different morphologies can be grown on the particles by controlling the PMMA content and annealed temperature,respectively.The optimum condition for the formation of high-quality few-layer graphene is 1.0 mg·ml^(-1) PMMA and 900℃.A competition mechanism rises from the growth kinetic,and the spatial confinement effect has led to the formation of graphene with different microstructures and morphologies.

Controllable construction of La_(2)Li_(0.5)Co_(0.5)O_(4)multifunctional“armor”to stabilize Li-rich layered oxide cathode for highperformance lithium-ion batteries

Lithium-rich manganese-based cathodes(LR)are valuable cathode materials for the next generation of lithium-ion batteries(LIBs)with high-energy density.However,the fast voltage/capacity decay on cycling is the major obstacle for the practical application induced by the less-than-ideal anionic redox reactions and structure distortion.Herein,in order to tackle these challenges,a perovskite-like La_(2)Li_(0.5)Co_(0.5)O_(4)(LLCO)material is selected as protective surface to stabilize the Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2)(LR)substrate through wet chemical coating method.Versatile structure/phase characterizations and electrochemical tests exhibit that the LLCO can not only minish the oxygen evolution and enhance the structure stability,but also restrain the electrolyte corrosion and increase the mechanical strength of cathode materials.Moreover,the coated LLCO with high electronic/ionic conductivity dramatically accelerates the energy storage kinetic,thereby displaying the improved rate performance.Specifically,the optimized LR@LLCO sample(1LLCO)exhibits a high capacity of 250.6 mAh·g^(-1)after 100 cycles at 0.1 C and excellent capacity retention of 82.6%after 200 cycles at 2 C.This work provides a new idea for the modification of LR cathodes toward commercial high-performance LIBs.

Cu_(2)O作为空穴提取层修饰BiVO_(4)光阳极以增强电荷分离和转移

光生电荷的分离和转移被认为是影响BiVO_(4)基光阳极光电性能的核心因素之一.本文设计了在BiVO_(4)光阳极与析氧助催化剂之间插入空穴提取层的方法.Cu_(2)O作为空穴提取层引入到助催化剂层(FeOOH/NiOOH)和BiVO_(4)之间,可以有效优化空穴的迁移路径,延长光生空穴的寿命,从而提高电极的光电化学性能.与BiVO_(4)相比,调整后的BiVO_(4)/Cu_(2)O/FeOOH/NiOOH光阳极的电荷分离效率从70.6%提高到了92.0%.此外,该光阳极在1.23 VRHE(AM 1.5G照明下)下,还显示出了3.85 mA cm^(-2)的高光电流密度,是BiVO_(4)的2.77倍.我们的研究结果表明,电沉积Cu_(2)O空穴提取层是一种简单且可扩展的方法,能够有效提高BiVO_(4)的光电活性,可用于太阳能驱动水分解领域.

Synergistic antibacterial activity of physical-chemical multi-mechanism by TiO2 nanorod arrays for safe biofilm eradication on implant

Treatment of implant-associated infection is becoming more challenging,especially when bacterial biofilms form on the surface of the implants.Developing multi-mechanism antibacterial methods to combat bacterial biofilm infections by the synergistic effects are superior to those based on single modality due to avoiding the adverse effects arising from the latter.In this work,TiO2 nanorod arrays in combination with irradiation with 808 nearinfrared(NIR)light are proven to eradicate single specie biofilms by combining photothermal therapy,photodynamic therapy,and physical killing of bacteria.The TiO2 nanorod arrays possess efficient photothermal conversion ability and produce a small amount of reactive oxygen species(ROS).Physiologically,the combined actions of hyperthermia,ROS,and puncturing by nanorods give rise to excellent antibacterial properties on titanium requiring irradiation for only 15 min as demonstrated by our experiments conducted in vitro and in vivo.More importantly,bone biofilm infection is successfully treated efficiently by the synergistic antibacterial effects and at the same time,the TiO2 nanorod arrays improve the new bone formation around implants.In this protocol,besides the biocompatible TiO2 nanorod arrays,an extra photosensitizer is not needed and no other ions would be released.Our findings reveal a rapid bacteria-killing method based on the multiple synergetic antibacterial modalities with high biosafety that can be implemented in vivo and obviate the need for a second operation.The concept and antibacterial system described here have large clinical potential in orthopedic and dental applications.

In vitro and in vivo antibacterial activity of graphene oxidemodified porous TiO_(2) coatings under 808-nm light irradiation

Bio-inertness and post-surgery infection on titanium(Ti)are the main causes of failure of biomedical implants in vivo.Near-infrared(NIR)photoactivated antibacterial therapy including photothermal and photodynamic therapies has attracted increasing attention due to the high bactericidal efficiency and little side effects.Although micro-arc oxidation(MAO)is an effective method to improve the biological activity of Ti implants,the porous TiO_(2)coatings prepared by MAO do not respond to near-infrared(NIR)light to kill bacteria by the photothermal and photodynamic effects.In this work,graphene oxide(GO)-modified TiO_(2)coatings(TiO_(2)/GO)are prepared on Ti to improve the photothermal and photodynamic ability of the MAO coatings.The TiO_(2)/GO coatings exhibit excellent antibacterial activity both in vitro and in vivo against Streptococcus mutans(S.mutans)under 808-nm NIR light irradiation due to the synergistic effects rendered by hyperthermia and reactive oxygen species(ROS).The NIR light-responsive antibacterial MAO coatings have large potential in combating implant-associated infections in clinical applications.

Improving exposure of anodically ordered Ni-Ti-O and corrosion resistance and biological properties of NiTi alloys by substrate electropolishing

Although Ni-Ti-O nanopores(NPs) can be fabricated by anodization of mechanically polished NiTi alloys, the top disordered layer is difficult to remove thus hindering the functionality of the Ni-Ti-O NPs. In this work, an electropolishing(EP) pretreatment was performed on the NiTi substrate prior to anodization to thoroughly expose the NPs. Our results show that the EP pretreatment for 5 min perfectly removes the top disordered layer on the Ni-Ti-O NPs to expose the underlying NPs and consequently, the corrosion resistance and antibacterial ability are enhanced. The exposed NPs can elongate bone marrow mesenchymal stem cells, which may be responsible for the upregulated alkaline phosphatase activity, secretion of Type I collagen, and extracellular matrix mineralization. These results suggest that EP is a desirable pretreatment before anodization of the NiTi alloys because the irregular surface layer on the Ni-Ti-O NPs can be removed to enhance the corrosion resistance and biological functions.

Selective inhibition effects on cancer cells and bacteria of Ni–Ti–O nanoporous layers grown on biomedical NiTi alloy by anodization

Stents made of nearly equiatomic NiTi alloy are used to treat malignant obstruction caused by cancer,but prevention of re-obstruction after surgery is still a challenge because the bare stents possess poor anticancer and antibacterial properties to inhibit cancer/bacteria invasion.The present work aims at endowing the NiTi alloy with anticancer and antibacterial abilities by surface modification.Ni–Ti–O nanoporous layers with different thicknesses were prepared on NiTi by anodization,and biological experiments were conducted to evaluate the effects on gram-positive Staphylococcus aureus,human lung epithelial cancer cells(A549),as well as human endothelial cells(EA.hy926).The nanoporous layer with a thickness of 10.1 lm inhibits growth of cancer cells and kill bacteria but shows little adverse effects on normal cells.Such selectivity is related to the larger amount of Ni ions leached from the sample in the acidic microenvironment of cancer cells in comparison with normal cells.The Ni–Ti–O nanoporous layers are promising as coatings on NiTi stents to prevent re-obstruction after surgery.

Corrosion behavior,antibacterial ability,and osteogenic activity of Zn-incorporated Ni-Ti-O nanopore layers on NiTi alloy

Development of bone fixation devices with excellent corrosion resistance,antibacterial ability,and osteogenic activity is critical for promoting fracture healing.In this study,Zn-incorporated nanopore(NP)layers were prepared on the NiTi alloy through anodization and hydrothermal treatment.Results show that Zn can be evenly incorporated into the NP layers in the form of ZnTiO_(2).The Zn-incorporated samples exhibit good corrosion resistance and significantly reduce Ni^(2+)release.Meanwhile,the samples can continuously release Zn^(2+),which is responsible for excellent long-term antibacterial ability.Furthermore,the synergetic effect of Zn^(2+) release and nanoporous structure of the NP layers endues the NiTi alloy excellent osteogenic activity,as verified by upregulated alkaline phosphatase activity,secretion of type I collagen,and extracellular matrix mineralization.Therefore,Zn-incorporated Ni-Ti-O NP layers have great potential as biomedical coatings of NiTi-based implant materials.

Green-emissive carbon quantum dots with high fluorescence quantum yield:Preparation and cell imaging

High fluorescence quantum yield(QY),excellent fluorescence stability,and low toxicity are essential for a good cellular imaging fluorescent probe.Green-emissive carbon quantum dots(CQDs)with many advantages,such as unique fluorescence properties,anti-photobleaching,low toxicity,fine biocompatibility and high penetration depth in tissues,have been considered as a potential candidate in cell imaging fluorescent probes.Herein,N,S-codoped green-emissive CQDs(QY=64.03%)were synthesized by the one-step hydrothermal method,with m-phenylenediamine as the carbon and nitrogen source,and L-cysteine as the nitrogen and sulfur dopant,under the optimum condition of 200℃ reaction for 2 h.Their luminescence was found to originate from the surface state.In light of the satisfactory photobleaching resistance and the low cytotoxicity,CQDs were used as a cell imaging probe for HeLa cell imaging.The results clearly indicate that cells can be labeled with CQDs,which can not only enter the cytoplasm,but also enter the nucleus through the nuclear pore,showing their broad application prospect in the field of cell imaging.

Sub-nanopores-containing N,O-codoped porous carbon from molecular-scale networked polymer hydrogel for solid-state supercapacitor

A template-free carbonization-activation route is developed to fabricate sub-nanopore-containing porous carbon by using a novel polypyrrole(PPy)hydrogel as a precursor.This design of PPy hydrogel precursor containing molecular-scale grids(diameter~2.0 nm)allows for homogeneous N,O-codoping into the porous carbon scaffold during the pyrolysis process.A subsequent activation step produces activated porous carbons(APCs)with tailored pore structures,which renders the APCs abundant subnanopores on their surface to increase the specific capacitance as extra capacitance sites.Coupled with large specific surface area and abundant heteroatoms,the optimized APC4/1 displays excellent specific capacitance of 379 F/g for liquid-state supercapacitor and 230 F/g for solid-state supercapacitor.The solid-state supercapacitor shows a high energy density of 22.99 Wh/kg at power density of 420 W/kg,which is higher than most reported porous carbon materials and satisfy the urgent requirements of elementary power source for electric vehicles.Moreover,this method can be easily modified to fabricate sub-nanopore-containing porous carbons with preferred structures and compositions for many applications.

Self-assembled nanosheets on NiTi alloy facilitate endothelial cell function and manipulate macrophage immune response

Stenting has been widely adopted for the treatment of cardiovascular diseases,but the complications such as in-stent restenosis and late stent thrombosis cannot be completely avoided,which are closely related to endothelial dysfunction and inflammatory response.In the present work,oxide nanosheets were grown on the surface of nearly equiatomic Ni Ti alloy by alkaline corrosion(AC),aiming at yielding favorable endothelial functionality and immune microenvironment.The results show nanosheets mainly composed of TiO_(2),Ni(OH)_(2),and K_(2)TiO_(3)can be grown on the alloy in KOH solution of 2.5–15 M at room temperature.The AC-treated samples significantly promote endothelial cell(EC)functionality such as proliferation,migration,NO production,VEGF secretion,and angiogenesis.In addition,the sample grown in KOH of 15 M can switch macrophages to an anti-inflammatory M2 phenotype and up-regulate the gene expression of VEGF to facilitate EC functionality.These results demonstrate that the nanosheets can directly and indirectly up-regulate EC functionality,possibly leading to rapid re-endothelialization of the stents thus addressing the stent-related complications.