小微企业电子商务应用问题研究—基于ATM框架的沈阳地区企业调查

本研究基于技术接受理论(TAM)的模型,以辽宁沈阳地区小微企业为主要研究对象,调查他们对于电子商务及其价值的认识、电子商务应用能力(应用电子商务的困难)、外部环境的影响(政府和本行业其他企业的影响)、电子商务意愿和应用行为等特征。研究发现:小微企业都介入了某种电子商务应用了,其电子商务意愿普遍较高,但对电子商务的概念及其价值认知、电子商务应用类别和投入意愿方面处于最初级状态并且具有显著的多样性和两级分化特征,业界同行对于他们认识和参与电子商务策略影响最大,政府的倡导作用式微,对电子商务的理解、电子商务人才因素、既有信息基础是他们电子商务能力的最主要制约因素。本文基于此提出了促进小微企业电子商务发展的建议。

Minimizing electrostatic interactions from piezoresponse force microscopy via capacitive excitation

Piezoresponse force microscopy(PFM)has emerged as one of the most powerful techniques to probe ferroelectric materials at the nanoscale,yet it has been increasingly recognized that piezoresponse measured by PFM is often influenced by electrostatic interactions.In this letter,we report a capacitive excitation PFM(ce-PFM)to minimize the electrostatic interactions.The effectiveness of ce-PFM in minimizing electrostatic interactions is demonstrated by comparing the piezoresponse and the effective piezoelectric coefficient measured by ce-PFM and conventional PFM.The effectiveness is further confirmed through the ferroelectric domain pattern imaged via ce-PFM and conventional PFM in vertical modes,with the corresponding domain contrast obtained by ce-PFM is sharper than conventional PFM.These results demonstrate ce-PFM as an effective tool to minimize the interference from electrostatic interactions and to image ferroelectric domain pattern,and it can be easily implemented in conventional atomic force microscope(AFM)setup to probe true piezoelectricity at the nanoscale.

Single crystalline CH_3NH_3PbI_3 self-grown on FTO/TiO_2 substrate for high efficiency perovskite solar cells

Since its first report in 2009,CH_3NH_3PbI_3-based perovskite solar cells(PSCs)have emerged as one of the most exciting developments in the next generation photovoltaic(PV)technologies[1],with its PV conversion efficiency(PCE)rising spectacularly from3.81% to 22.1% in just 7 years.Such rapid advance is

Sol-Gel Based Soft Lithography and Piezoresponse Force Microscopy of Patterned Pb(Zr_(0.52)Ti _(0.48))O_3 Microstructures

Sol-gel based soft lithography technique has been developed to pattern a variety of ferroelectric Pb(Zr0.52Ti0.48)O3(PZT) microstructures,with feature size approaching 180 nm and good pattern transfer between the master mold and patterned films.X-ray diffraction and high-resolution transmission electron microscopy confirm the perovskite structure of the patterned PZT.Piezoresponse force microscopy(PFM) and switching spectroscopy piezoresponse force microscopy(SSPFM) confirm their piezoelectricity and ferroelectricity.Piezoresponse as high as 2.75 nm has been observed,comparable to typical PZT films.The patterned PZT microstructures are promising for a wide range of device applications.

Seeing is believing: negative capacitance captured at both nano-and macro-scales

The phenomenological theory of ferroelectrics was developed by Landau-Devonshire about 70 years ago in the 1940s [1], and the celebrated theory has been very successful in analyzing ferroelectric phase transitions [2,3], domain structures [4], as well as strain engineering [5,6]. Recently, it has been demonstrated that it is also capable of capturing emerging polarization textures such as a ferroelectric vortex [7], proving its wide applicability not only at phenomenological level, but also at the atomic scale. The idea is simple, that the internal energy density of a ferroelectric depends on polarization, the order parameter, and upon the phase transition, the energy becomes degenerate, corresponding to multiple ferroelectric variants arising from broken symmetry. Such behavior is captured well by a polynomial of polarization with temperaturedependent coefficient, as Devonshire originally demonstrated for barium titanate [1].

Bubble domain evolution in well-ordered BiFeO_(3) nanocapacitors

Ferroelectric nanocapacitors have attracted intensive research interest due to their novel functionalities and potential application in nanodevices.However,due to the lack of knowledge of domain evolution in isolated nanocapacitors,precise manipulation of topological domain switching in the nanocapacitor is still a challenge.Here,we report unique bubble and cylindrical domains in the well-ordered BiFeO_(3) nanocapacitor array.The transformation of bubble,cylindrical and mono domains in isolated ferroelectric nanocapacitor has been demonstrated via scanning probe microscopy(SPM).The bubble domain can be erased to mono domain or written to cylindrical domain and mono domain by positive and negative voltage,respectively.Additionally,the domain evolution rules,which are mainly affected by the depolarization field,have been observed in the nanocapacitors with different domain structures.This work will be helpful in understanding the domain evolution in ferroelectric nanocapacitors and providing guidance on the manipulation of nanoscale topological domains.

Organic near-infrared photodetectors with photoconductivityenhanced performance

Organic near-infrared(NIR)photodetectors with essential applications in medical diagnostics,night vision,remote sensing,and optical communications have attracted intensive research interest.Compared with most conventional inorganic counterparts,organic semiconductors usually have higher absorption coefficients,and their thin active layer could be sufficient to absorb most incident light for effective photogeneration.However,due to the relatively poor charge mobility of organic materials,it remains challenging to inhibit the photogenerated exciton recombination and effectively extract carriers to their respective electrodes.Herein,this challenge was addressed by increasing matrix conductivities of a ternary active layer(D–A–D structure NIR absorber[2TT-oC6B]:poly(N,N′-bis-4-butylphenyl-N,N′-bisphenyl)benzidin[PolyTPD]:[6,6]-phenyl-C61-butyric acid methyl ester[PCBM]=1:1:1)upon in situ incident light illumination,significantly accelerating charge transport through percolated interpenetrating paths.The greatly enhanced photoconductivity under illumination is intrinsically related to the unique donor–acceptor molecular structures of PolyTPD and 2TT-oC6B,whereas stable intermolecular interaction has been verified by systematic molecular dynamics simulation.In addition,an ultrafast charge transfer time of 0.56 ps from the NIR aggregation-induced luminogens of 2TT-oC6B absorber to PolyTPD and PCBM measured by femtosecond transient absorption spectroscopy is beneficial for effective exciton dissociation.The solution-processed organic NIR photodetector exhibits a fast response time of 83μs and a linear dynamic range value of 111 dB under illumination of 830 nm.Therefore,our work has opened up a pioneering window to enhance photoconductivity through in situ photoirradiation and benefit NIR photodetectors as well as other optoelectronic devices.

有机无机杂化钙钛矿电镜表征的虚与实

近年来,由于合成价格低廉以及光电转化效率高,基于有机无机杂化钙钛矿材料的太阳能电池得到了飞速发展.然而这些材料容易分解,这极大地限制了该技术的商业化应用.基于透射电子显微镜的表征有助于解析这些材料的降解机理.然而杂化钙钛矿材料对电子束辐照十分敏感,易引起结构失稳甚至分解,进而阻碍我们获取真实结构信息.本文利用低电子束剂量成像技术系统地研究了不同实验条件下杂化钙钛矿的结构不稳定性,揭示了最优的透射电镜表征条件.我们发现,低温(-180°C)并没有减缓束损伤,反而导致了快速的非晶化;较高的加速电压有利于降低损伤;MAPbI3(100)面比(001)面更稳定.基于这些发现,我们成功地获得了MAPbI3原始的原子结构,并确定了其表征窗口非常窄.这些发现有助于指导未来对这些电子束敏感材料的电子显微表征,也有助于寻找提高钙钛矿型太阳能电池稳定性的策略.

Insight into vitronectin structural evolution on material surface chemistries: The mediation for cell adhesion

Biomaterial surface chemistry engenders profound consequences on cell adhesion and the ultimate tissue response by adsorbing proteins from extracellular matrix,where vitronectin(Vn)is involved as one of the crucial mediator proteins.Deciphering the adsorption behaviors of Vn in molecular scale provides a useful account of how to design biomaterial surfaces.But the details of structural dynamics and consequential biological effect remain elusive.Herein,both experimental and computational approaches were applied to delineate the conformational and orientational evolution of Vn during adsorption onto self-assembled monolayers(SAMs)terminating with-COOH,-NH2,-CH3 and-OH.To unravel the interplay between cell binding and the charge and wettability of material surface,somatomedin-B(SMB)domain of Vn holding the RGD cell-binding motif was employed in molecular dynamics(MD)simulations,with orientation initialized by Monte Carlo(MC)method.Experimental evidences including protein adsorption,cell adhesion and integrin gene expressions were thoroughly investigated.The adsorption of Vn on different surface chemistries showed very complex profiles.Cell adhesion was enabled on all Vn-adsorbed surfaces but with distinct mechanisms mostly determined by conformational change induced reorientation.Higher amount of Vn was observed on negatively charged surface(COOH)and hydrophobic surface(CH3).However,advantageous orientations defined by RGD loop conditions were only obtained on the charged surfaces(COOH and NH2).Specifically,COOH surface straightened up the Vn molecules and accumulated them into a higher density,whereas CH3 surface squashed Vn and stacked them into higher density multilayer by tracking adsorption but with the RGD loops restrained.These findings may have a broad implication on the understanding of Vn functionality and would help develop new strategies for designing advanced biomaterials.

Mapping the elastic properties of two-dimensional MoS_(2) via bimodal atomic force microscopy and finite element simulation

Elasticity is a fundamental mechanical property of two-dimensional(2D)materials,and is critical for their application as well as for strain engineering.However,accurate measurement of the elastic modulus of 2D materials remains a challenge,and the conventional suspension method suffers from a number of drawbacks.In this work,we demonstrate a method to map the in-plane Young’s modulus of mono-and bi-layer MoS_(2) on a substrate with high spatial resolution.Bimodal atomic force microscopy is used to accurately map the effective spring constant between the microscope tip and sample,and a finite element method is developed to quantitatively account for the effect of substrate stiffness on deformation.Using these methods,the in-plane Young’s modulus of monolayer MoS_(2) can be decoupled from the substrate and determined as 265±13 GPa,broadly consistent with previous reports though with substantially smaller uncertainty.It is also found that the elasticity of mono-and bi-layer MoS_(2) cannot be differentiated,which is confirmed by the first principles calculations.This method provides a convenient,robust and accurate means to map the in-plane Young’s modulus of 2D materials on a substrate.

Unexpected boost of thermoelectric performance by magnetic nanoparticles

Thermoelectric materials are capable of converting heat into electricity and vice versa,and thus they are attractive in waste heat recovery and solid-state thermal management.Nevertheless,thermoelectric technologies are only limited to niche applications so far,for example in space exploration,since it is rather challenging to enhance their conversion efficiency.

Comparative tribological behavior of friction composites containing natural graphite and expanded graphite

In this study, expanded graphite and natural graphite were introduced into resin-based friction materials, and the tribological behavior of the composites was investigated. The tribo-performance of the two friction composites was evaluated using a constant speed friction tester. The results showed that the expanded graphite composite (EGC) displayed better lubricity in both the fading and the recovery processes. The wear rate of the EGC decreased by 22.43%more than that of the natural graphite composite (NGC). In the fading process, and the EGC enhanced the stability of the coefficient of friction. The recovery maintenance rate of the NGC was 4.66% higher than that of the EGC. It can be concluded that expanded graphite plays an important role in the formation of a stable contact plateau and can effectively reduce the wear.

Imaging ferroelectric domains via charge gradient microscopy enhanced by principal component analysis

Local domain structures of ferroelectrics have been studied extensively using various modes of scanning probes at the nanoscale,including piezoresponse force microscopy(PFM)and Kelvin probe force microscopy(KPFM),though none of these techniques measure the polarization directly,and the fast formation kinetics of domains and screening charges cannot be captured by these quasi-static measurements.In this study,we used charge gradient microscopy(CGM)to image ferroelectric domains of lithium niobate based on current measured during fast scanning,and applied principal component analysis(PCA)to enhance the signal-to-noise ratio of noisy raw data.We found that the CGM signal increases linearly with the scan speed while decreases with the temperature under power-law,consistent with proposed imaging mechanisms of scraping and refilling of surface charges within domains,and polarization change across domain wall.We then,based on CGM mappings,estimated the spontaneous polarization and the density of surface charges with order of magnitude agreement with literature data.The study demonstrates that PCA is a powerful method in imaging analysis of scanning probe microscopy(SPM),with which quantitative analysis of noisy raw data becomes possible.

Hollow spheres self-assembled by MoO_(2) nanocones as highly sensitive substrate for Surface-Enhanced Raman Spectroscopy

Surface-Enhanced Raman Spectroscopy attracts great interests for its ability to detect a variety of molecules at trace level.However,the commonly used noble metal substrates suffer from high cost,poor biocompatibility and inferior stability.Some oxides have the potential to substitute for noble metal and much effort has been made to improve their performance.In this paper,MoO_(2) nanocones were prepared and self-assembled into hollow spheres.The structure exhibits an enhancement factor(EF)of 3×10_(7) and a limit of detection(LOD)of 10^(-9) M for Rhodamine 6G(R6G).This performance is among the best of all the oxides and is comparable to that of Au and Ag.The morphology control of hollow MoO2 sphere was also discussed.

Muscovite mica as a universal platform for flexible electronics

During recent years,flexible electronics that are highlybendable,foldable,stretchable and twistable without sacrificing their functional performances have attracted a great number of researchers and engineers[1e5],and the rapid development of flexible electronics has promised to revolutionize the consumer electronics[6].For example,wearable devices[7],foldable displays[8],implanted systems[3]and brain-machine interfaces[9]have been emerged as innovative technologies.What is more,flexoelectricity and anomalous polarization behavior have been observed and manipulated[10,11],thanks to the flexibility rendered at the materials,structures,and devices level.