Local electric field and configuration of CO molecules adsorbed on a nanostructured surface with nanocones

Based on the nanostructured surface model that the （platinum, Pt） nanocones grow out symmetrically from a plane substrate, the local electric field near the conical nanoparticle surface is computed and discussed. On the basis of these results, the adsorbed CO molecules are modelled as dipoles, and three kinds of interactions, i.e. interactions between dipoles and local electric field, between dipoles and dipoles, as well as between dipoles and nanostructured substrate, are taken into account. The spatial configuration of CO molecules adsorbed on the nanocone surface is then given by Monte-Carlo simulation. Our results show that the CO molecules adsorbed on the nanocone surface cause local agglomeration under the action of an external electric field, and this agglomeration becomes more compact with decreasing conical angle, which results in a stronger interaction among molecules. These results serve as a basis for explaining abnormal phenomena such as the abnormal infrared effect （AIRE）, which was found when CO molecules were adsorbed on the nanostructured transition-metal surface.

Self-cleaning of superhydrophobic nanostructured surfaces at low humidity enhanced by vertical electric field

Self-cleaning is the key factor that makes superhydrophobic nanostructured materials have wide applications.The self-cleaning effect,however,strongly depends on formations and movement of water droplets on superhydrophobic nanostructured surfaces,which is greatly restricted at low humidity(<7.6 g·kg^(-1)).Therefore,we propose a self-cleaning method at low humidity in which the pollution is electro-aggregated and driven in the electric field to achieve the aggregation and cleaning large areas.The cleaning efficiency of this method is much higher than that of water droplet roll-off,and will not produce"pollution bands".A simplified numerical model describing pollution movements is presented.Simulation results are consistent with experimental results.The proposed method realizes the self-cleaning of superhydrophobic nanostructured surfaces above dew point curve for the first time,which extends applications of superhydrophobic nanostructured materials in low humidity,and is expected to solve self-cleaning problems of outdoor objects in low humidity areas(<5.0 g·kg^(-1)).

Leidenfrost drops on micro/nanostructured surfaces

In the Leidenfrost state, the liquid drop is levitated above a hot solid surface by a vapor layer generated via evaporation from the drop. The vapor layer thermally insulates the drop from the heating surface, causing deteriorated heat transfer in a myriad of important engineering applications. Thus, it is highly desirable to suppress the Leidenfrost effect and elevate the Leidenfrost temperature. This paper presents a comprehensive review of recent literature concerning the Leidenfrost drops on micro/nanostructured surfaces with an emphasis on the enhancement of the Leidenfrost temperature. The basic physical processes of the Leidenfrost effect and the key characteristics of the Leidenfrost drops were first intro- duced. Then, the major findings of the influence of various micro/nanoscale surface structures on the Leidenfrost temperature were presented in detail, and the underlying enhancement mechanism for each specific surface topology was also discussed. It was concluded that multiscale hierarchical surfaces hold the best promise to significantly boost the Leidenfrost temperature by combin- ing the advantages of both micro- and nanoscale structures.

Manufacturing of Surface Nanostructured Fibers Featuring an Antibacterial Effect by Magnetic Field Transportation of Magnetite@Silver Core-Shell Nanoparticles

Magnetic core-shell nanoparticles of type Fe3O4@Ag were synthesized in gram scale following a combined co-precipitation phase-transfer method and afterwards, processed to nanoparticle polymer (polypropylene and polyamide) composites. These composites were used as sheath material for the fabrication of core-sheath fibers. During the melt spinning process, a magnetic field was applied around the roving, whereby the particles move in the still liquid sheath polymer towards the surface. The produced fiber materials were investigated by AFM showing a nanostructuring of the surface, which was indirectly confirmed by determination of a slight surface tension lowering. Nanoparticle movement was shown by cross-section SEM and EDX measurements. The antibacterial activity of the spun fibers was proven by contacting them with Escherichia coli. A long-term stability of this effect was observable by carrying out a standard washability test. In contrast to previous works this new approach uses no deposition technique to introduce surface changes. It rather applies a magnetic force to move appropriately equipped nanoparticles from the inside of the fiber to the surface. This leads in only one step to a strong superficial anchoring of the particles resulting in a unique combination of long-term stable antibacterial and improved anti-soiling effects.

Two-dimensional laser-induced periodic surface structures formed on crystalline silicon by GHz burst mode femtosecond laser pulses

Femtosecond laser pulses with GHz burst mode that consist of a series of trains of ultrashort laser pulses with a pulse interval of several hundred picoseconds offer distinct features in material processing that cannot be obtained by the conventional irradiation scheme of femtosecond laser pulses(single-pulse mode).However,most studies using the GHz burst mode femtosecond laser pulses focus on ablation of materials to achieve high-efficiency and high-quality material removal.In this study,we explore the ability of the GHz burst mode femtosecond laser processing to form laser-induced periodic surface structures(LIPSS)on silicon.It is well known that the direction of LIPSS formed by the single-pulse mode with linearly polarized laser pulses is typically perpendicular to the laser polarization direction.In contrast,we find that the GHz burst mode femtosecond laser(wavelength:1030 nm,intra-pulse duration:220 fs,intra-pulse interval time(intra-pulse repetition rate):205 ps(4.88 GHz),burst pulse repetition rate:200 kHz)creates unique two-dimensional(2D)LIPSS.We regard the formation mechanism of 2D LIPSS as the synergetic contribution of the electromagnetic mechanism and the hydrodynamic mechanism.Specifically,generation of hot spots with highly enhanced electric fields by the localized surface plasmon resonance of subsequent pulses in the bursts within the nanogrooves of one-dimensional LIPSS formed by the preceding pulses creates 2D LIPSS.Additionally,hydrodynamic instability including convection flow determines the final structure of 2D LIPSS.

Local field distribution and configuration of CO molecules adsorbed on the nanostructure platinum surface

This paper shows that the local electric field distribution near the nanostructure metallic surface is obtained by solving the Laplace equation, and furthermore, the configuration of CO molecules adsorbed on a Pt nanoparticle surface is obtained by using Monte Carlo simulation. It is found that the uneven local electric field distribution induced by the nanostructure surface can influence the configuration of carbon monoxide （CO） molecules by a force, which drags the adsorbates to the poles of the nanoparticles. This result, together with our results obtained before, may explain the experimental results that the nanostructure metallic surface can lead to abnormal phenomena such as anti-absorption infrared effects.

Hydroxyapatite-modified micro/nanostructured titania surfaces with different crystalline phases for osteoblast regulation

Surface structures and physicochemical properties critically influence osseointegration of titanium(Ti)implants.Previous studies have shown that the surface with both micro-and nanoscale roughness may provide multiple features comparable to cell dimensions and thus efficiently regulate cell-material interaction.However,less attention has been made to further optimize the physicochemical properties(e.g.,crystalline phase)and to further improve the bioactivity of micro/nanostructured surfaces.Herein,micro/nanostructured titania surfaces with different crystalline phases(amorphous,anatase and anatase/rutile)were prepared and hydroxyapatite(HA)nanorods were deposited onto the as-prepared surfaces by a spin-assisted layer-by-layer assembly method without greatly altering the initial multi-scale morphology and wettability.The effects of crystalline phase,chemical composition and wettability on osteoblast response were investigated.It is noted that all the micro/nanostructured surfaces with/without HA modification presented superamphiphilic.The activities of MC3T3-E1 cells suggested that the proliferation trend on the micro/nanostructured surfaces was greatly influenced by different crystalline phases,and the highest proliferation rate was obtained on the anatase/rutile surface,followed by the anatase;but the cell differentiation and extracellular matrix mineralization were almost the same among them.After ultrathin HA modification on the micro/nanostructured surfaces with different crystalline phases,it exhibited similar proliferation trend as the original surfaces;however,the cell differentiation and extracellular matrix mineralization were significantly improved.The results indicate that the introduction of ultrathin HA to the micro/nanostructured surfaces with optimized crystalline phase benefits cell proliferation,differentiation and maturation,which suggests a favorable biomimetic microenvironment and provides the potential for enhanced implant osseointegration in vivo.

Influence of laser peening on microstructure and fatigue lives of Ti-6Al-4V

The influence of low energy laser peening on fatigue lives of Ti-6Al-4V was investigated. Laser peening was carried out on Ti-6Al-4V samples. Laser peened samples were characterized by residual stress analysis, surface roughness measurements, X-ray diffraction, optical microscopy, nanoindentation hardness tests, scanning and transmission electron microscopy and fatigue testing. Laser peening resulted in the formation of nanocrystallites on the surface and near surface regions with associated increase in hardness and introduction of compressive residual stress. Owing to positive influence of nanostructured surface and compressive residual stress, fatigue lives of the laser peened samples were significantly increased compared to the unpeened samples.

A general, rapid and solvent-free approach to fabricating nanostructured polymer surfaces

A general, rapid and solvent-free approach is proposed to fabricate nanostructured polymer surfaces by coupling ultrasonic vi- bration and anodized aluminum oxide templating. With our approach, hollow nanorods or nanofibers with controlled diameter and length are prepared on polymer surfaces. The whole fabrication process is completed in ～30 s and equally applicable to polymers of different crystalline structures. The wettability of the as-fabricated polymer surfaces （being hydrophilic, hydro- phobic, highly hydrophobic or even superhydrophobic） is readily regulated by adjusting the welding time from 0 s to a maxi- mum of 10 s. Our approach can be a promising industrial basis for manufacturing functional nanomaterials in the fields of electronics, optics, sensors, biology, medicine, coating, or fluidic technologies.

Periodic transparent nanowires in ITO film fabricated via femtosecond laser direct writing

This paper reports the fabrication of regular large-area laser-induced periodic surface structures(LIPSSs)in indium tin oxide(ITO)films via femtosecond laser direct writing focused by a cylindrical lens.The regular LIPSSs exhibited good properties as nanowires,with a resistivity almost equal to that of the initial ITO film.By changing the laser fluence,the nanowire resistances could be tuned from 15 to 73 kΩ/mm with a consistency of±10%.Furthermore,the average transmittance of the ITO films with regular LIPSSs in the range of 1200-2000 nm was improved from 21%to 60%.The regular LIPSS is promising for transparent electrodes of nano-optoelectronic devices-particularly in the near-infrared band.

Electric potential distribution near nanocone arrays on metal substrates

Based on the nanostructured surface model,where conical nanoparticle arrays grow out symmetrically from a plane metal substrate,a theoretical model of the local electric potential near nanocones is built when a uniform external electric field is applied.In terms of this model,the electric potential distribution near the nanocone arrays is obtained and given by a curved surface using a numerical computation method.The computational results show that the electric potential distribution near the nanocone arrays exhibit an obvious geometrical symmetry.These results could serve as a basis for explaining many abnormal phenomena,such as the abnormal infrared effects（AIREs） which are found on nanostructured metal surfaces,as well as a reference for investigating the applications of nanomaterials,such as nanoelectrodes and nanosensors.

Origins of Ultrafast Pulse Laser-Induced Nano Straight Lines with Potential Applications in Detecting Subsurface Defects in Silicon Carbide Wafers

The inspection of silicon carbide(SiC)wafer quality has attracted considerable attention because internal microstructure defects are challenging to detect in production lines.Expensive and destructive methods are usually employed to detect dislocations and stacking faults inside SiC wafers.Fast optical methods to monitor internal defects are in demand.In this work,an ultrafast pulse laser was used to address this issue.The formation of surface nanostructures under the ultrafast laser processing of SiC wafers was explored systematically.This study discovered the origins of a typical surface nanostructure to the subsurface dislocation structure,called low-energy laser-induced nano straight lines(LLINSs),which forms under low-energy ultrafast pulse laser irradiation on a SiC wafer.The specific laser fluence ranges to form grooves,laser-induced periodic surface structures,LLINSs,and their hybrids were identified.The formation of LLINSs required an ultrafast laser(pulse width 280 fs)energy density less than 0.224 J/mm2,whereas that of pure LLINSs required a small range of 0.1–0.08 J/mm2 for SiC.LLINSs and their surrounding microstructures were observed using scanning transmission electron microscopy to identify their origin,which is related to the subsurface dislocation structure.Molecular dynamics analysis revealed that the subsurface defect area has a high energy level,which can facilitate amorphous transformation under the irradiation of an ultrafast laser,and the amorphous area had a tendency to evolve into LLINSs.Thus,subsurface lattice defects can be detected optically.This work opens new ways to detect the subsurface quality of semiconductor wafers in a green and sustainable manner.

A Unified Spatio-Temporal Framework of the Cuerno-Barabasi Stochastic Continuum Model of Surface Sputtering

The nonlinear continuum model proposed by Cuerno and Barabasi is the most successful and widely acceptable theoretical description of oblique incidence ion sputtered surfaces to date and is quite robust in its predictions of the time evolution and scaling of interfaces driven by ion bombardment. However, this theory has thus far predicted only ripple topographies and rough surfaces for short and large scales, respectively. As a result, its application to the interpretation and study of nanodots, predicted by Monte Carlo simulations for, and observed in experiments of, oblique incidence sputtering is still unclear and, hence, an open problem. In this paper, we provide a new insight to the theory, within the same length scale, that explains nanodot formation on off-normal incidence sputtered surfaces, among others, and propose ways of observing the predicted topographies of the MC simulations, as well as possible control of the size of the nanodots, in the framework of the Cuerno-Barabasi continuum theory.

Fatigue life improvement and grain growth of gradient nanostructured industrial zirconium during high cycle fatigue

The effect of surface gradient nanostructure on the fatigue life of commercial pure(CP)Zr was investigated.Four point bending fatigue tests indicated that the fatigue limit of CP Zr with surface gradient nanostructure was increased by about 28.3%compared with the original sample(annealed state).The microstructure evolution at different fatigue loading stages was characterized.The high strength of surface gradient nanostructure could increase the crack initiation resistance.Furthermore,electron back scattered diffraction(EBSD)analysis demonstrated that the surface nanocrystals grew and rotated gradually during the fatigue loading,which was beneficial to reducing stress concentration,inhibit fatigue crack initiation,and prolong crack initiation life.The stored distortion energy of CP Zr calculated before and after fatigue indicated that the stored distortion energy decreased dramatically during cyclic loading,which provided the driving force for grain growth.Besides,the growth of nanocrystals consumed the mechanical energy produced by the applied load to a certain extent,thus,slowing down the accumulation of fatigue damage.The coarse grains at the interior could deform plastically and reduce the crack growth rate.In addition,the compressive residual stress caused by USSP treatment reduced the local effective stress and the driving force of crack growth.

On-surface construction of low-dimensional nanostructures with terminal alkynes: Linking strategies and controlling methodologies

Bottom-up approach to constructing low-dimensional nanostructures on surfaces with terminal alkynes has drawn great interest because of its potential applications in fabricating advanced functional nanomaterials. The diversity of the achieved products manifests rich chemistry of terminal alkynes and hence careful linking strategies and proper controlling methodologies are required for selective preparations of high-quality target nanoarchitectures. This review summarizes various on-surface linking strategies for terminal alkynes, including non-bonding interactions as well as organometallic and covalent bonds, and presents examples to show effective control of surface assemblies and reactions of terminal alkynes by variations of the precursor structures, substrates and activation modes. Systematic studies of the on-surface linkage of terminal alkynes may help efficient and predictable preparations of surface nanomaterials and further understanding of surface chemistry.

Nanomaterials for treating cardiovascular diseases:A review

Nanomaterials such as nanostructured surfaces,nanoparticles,and nanocomposites represent new viable sources for future therapeutics for cardiovascular diseases.The special properties of nanomaterials such as their intrinsic physiochemical properties,surface energy and surface topographies could actively enhance desirable cellular responses within the cardiovascular system,projecting a growing potential for clinical translation.Recent progress on nanomaterials opened up new opportunities for treating cardiovascular diseases.Successful translation of nanomaterials into cardiovascular applications requires a comprehensive understanding of both nanomaterials and biomedicine,and,thus,it is critical to stress current advancements on both sides.In this review,the authors introduced crucial fabrication techniques for promising nanomaterials for cardiovascular applications.This review highlighted the key elements to consider for their fabrication,properties and applications.The important concerns relevant to cardiovascular nanomaterials,such as cellular responses to nanomaterials and the toxicity of nanomaterials,are also discussed.This review provided an overview of necessary knowledge and key concerns on nanomaterials specific for treating cardiovascular diseases,from the perspectives of both material science and biomedicine.

Exploring the Transferability of Large Supramolecular Assemblies to the Vacuum-Solid Interface

We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-functionalized rosette assembly and its building blocks on a Au(111)surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces.The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111)surface under ultra-high vacuum conditions;the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly,suggesting that the assembly itself can be transferred intact to the surface by in situ thermal sublimation.This unanticipated result will open up new perspectives for growth of complex 3-D supramolecular nanostructures at the vacuum-solid interface.