Ionic conduction and phase separation studies in P(VdF-HFP))-LiClO4-dedoped polyaniline nanofiber composite polymer electrolytes — II: Effect of incorporation of PC and DEC

In the present work, ionic transport and interfacial stability of dedoped (insulating) polyaniline (PAni) nanofibers dispersed P(VdF-HFP) based nanocomposite gel polymer electrolytes have been investigated. Samples of P(VdF-HFP)-(PC+DEC)-LiClO₄-x wt. % dedoped PAni nanofibers (x = 0, 2, 4, 6, 8, 10) are prepared by conventional solution casting technique. By analysis of SEM, XRD and impedance spectroscopy results it has been demonstrated that the incorporation of up to 6 wt. % of dedoped PAni nanofibers to P(VdF-HFP)-(PC+DEC)-LiClO₄ polymer electrolyte system significantly enhances the ionic conductivity and interfacial stability of the electrolyte system. Above that concentration phase separation of PAni nanofibers is observed leading to decrease in ionic conductivity. The aggregated phase decreases the porosity, which results in lower ionic conductivity as confirmed by SEM. Experiments on the interfacial stability reveals that the stability of polymer electrolytes containing nanofibers is better than that of nanofiber free polymer electrolytes.     

Anisotropic formation mechanism and nanomechanics for the self-assembly process of cross-β peptides

Nanostructures self-assembled by cross-β peptides with ordered structures and advantageous mechanical properties have many potential applications in biomaterials and nanotechnologies. Quantifying the intra-and inter-molecular driving forces for peptide self-assembly at the atomistic level is essential for understanding the formation mechanism and nanomechanics of various morphologies of self-assembled peptides. We investigate the thermodynamics of the intra-and inter-sheet structure formations in the self-assembly process of cross-β peptide KIIIIK by means of steered molecular dynamics simulation combined with umbrella sampling. It is found that the mechanical properties of the intra-and inter-sheet structures are highly anisotropic with their intermolecular bond stiffness at the temperature of 300 K being 5.58 N/m and0.32 N/m, respectively. This mechanical anisotropy comes from the fact that the intra-sheet structure is stabilized by enthalpy but the inter-sheet structure is stabilized by entropy. Moreover, the formation process of KIIIIK intra-sheet structure is cooperatively driven by the van der Waals(VDW) interaction between the hydrophobic side chains and the electrostatic interaction between the hydrophilic backbones, but that of the inter-sheet structure is primarily driven by the VDW interaction between the hydrophobic side chains. Although only peptide KIIIIK is studied, the qualitative conclusions on the formation mechanism should also apply to other cross-β peptides.     

阳极氧化铝模板表面自组织条纹的形成

对未经化学抛光处理的Al进行阳极氧化得到阳极氧化铝模板，发现Al表面形成了条纹与多孔阵列共存的自组织结构，用原子力显微镜对这种结构进行了研究.借助Brusselator模型对条纹的形成机理进行了讨论，认为条纹图案是Al表面氧化层/电解液界面的Al₂O₃在整个反应过程中的生成和溶解两个过程相互竞争导致的，只有在特定的反应条件才会出现高度有序的结构. 关键词： 氧化铝模板（AAO） 原子力显微镜（AFM） 自组织条纹 Brusselator模型     

Factors influencing the electronic properties of arrays of ligand-stabilized gold nanocrystals

We review our recent progress on probing the electronic properties of self-assembled arrays of ligand-stabilized gold nanocrystals via charge transport measurements on both laterally- and vertically-contacted arrays. We show that the electronic properties of these assemblies can be manipulated through experimental control of the nanocrystal diameter, the array formation conditions and the nature of the protecting ligand.     

Morphology and photoluminescence of self-assembled GeSi/Si nanoclusters grown by sublimation molecular-beam epitaxy in a GeH<Subscript>4</Subscript> ambient

The dependence of the morphology and photoluminescence spectra of GeSi/Si(001) heterostructures with self-assembled nanoclusters, obtained by sublimation molecular-beam epitaxy in a GeH₄ ambient, on the growth conditions has been analyzed. The conditions for obtaining structures with uniform nanocluster arrays exhibiting photoluminescence at room temperature have been determined.     

Novel self-assembled nanostructured alumina array with nanoscale grooves

A unique novel self-assembled nanostructured alumina array with nanoscale grooves can be induced and controlled in nanometer dimension by a general electrochemical oxidation of aluminum in sulfuric acid. Almost inter-perpendicular self-assembled alumina nanostructure arrays separated by a few tens nanometer thick interface sheet were also observed in many domains. And the formation of this nanostructured array is considered as the result of the special competition balance between electrochemical oxidation and etching. Because of similarities of aluminum anodization with semiconductor anodization, our results may be proved useful for Si or GaAs nanostructure synthesis.     

Electrostatic-field-driven alignment of organic oligomers on ZnO surfaces

We study the physisorption of organic oligomers on the strongly ionic ZnO(1010) surface by using first-principles density-functional theory and nonempirical embedding methods. It turns out that the in-plane variation of the molecule-substrate interaction energy and the bonding dipole in the vertical direction are linked up by a linear relationship originating from the electrostatic coupling of the molecule with the periodic dipolar electric field generated by the Zn-O surface dimers. Long oligomers with a highly axial π-electron system such as sexiphenyl become well oriented with alignment energies of several 100 meV along rows of a positive electric field, in full agreement with recent experiments. These findings define a new route towards the realization of highly ordered self-assembled arrays of oligomers or polymers on ZnO(1010) and similar surfaces.     

Strain relaxation and optical properties of etched In_0.19Ga_0.81 N nanorod arrays on the GaN template

InGaN/GaN epilayers,which are grown on sapphire substrates by the metal-organic chemical-vapour deposition(MOCVD) method,are formed into nanorod arrays using inductively coupled plasma etching via self-assembled Ni nanomasks.The formation of nanorod arrays eliminates the tilt of the InGaN(0002) crystallographic plane with respect to its GaN bulk layer.Photoluminescence results show an apparent S-shaped dependence on temperature.The light extraction efficiency and intensity of photoluminescence emission at low temperature of less than 30 K for the nanorod arrays are enhanced by the large surface area,which increases the quenching effect because of the high density of surface states for the temperature above 30 K.Additionally,a red-shift for the InGaN/GaN nanorod arrays is observed due to the strain relaxation,which is confirmed by reciprocal space mapping measurements.     

Strain relaxation and optical properties of etched In0.19Ga0.81N nanorod arrays on the GaN template

InGaN/GaN epilayers,which are grown on sapphire substrates by the metal-organic chemical-vapour deposition(MOCVD) method,are formed into nanorod arrays using inductively coupled plasma etching via self-assembled Ni nanomasks.The formation of nanorod arrays eliminates the tilt of the InGaN(0002) crystallographic plane with respect to its GaN bulk layer.Photoluminescence results show an apparent S-shaped dependence on temperature.The light extraction efficiency and intensity of photoluminescence emission at low temperature of less than 30 K for the nanorod arrays are enhanced by the large surface area,which increases the quenching effect because of the high density of surface states for the temperature above 30 K.Additionally,a red-shift for the InGaN/GaN nanorod arrays is observed due to the strain relaxation,which is confirmed by reciprocal space mapping measurements.     

The formation of sub-10 nm nanohole array on block copolymer thin films on gold surface using surface neutralization based on O2 plasma treatment and self-assembled monolayer

Blockcopolymer (BCP) lithography is an emerging nanolithography technique for fabrications of various nanoscale devices and materials. In this study, self-assembled BCP thin films having cylindrical nanoholes were prepared on gold by surface neutralization using self-assembled monolayer (SAM). Oxygen plasma treatment was investigated as a way to enhance the functionality of Au surface toward SAM formation. After surface neutralization, well-ordered nanoholes with 9 to 20 nm diameters were formed inside BCP thin films on Au surfaces through microphase separation. The effects of oxygen plasma treatment on the formation of BCP nanopattern were investigated using surface analysis techniques including X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. Au nanodot arrays were fabricated on gold film by utilizing the BCP nanotemplate and investigated by atomic force microscopy (AFM).     

Dopant size dependent variable range hopping conduction in polyaniline nanorods

The present work investigates the electrical transport and dielectric relaxation of polyaniline (PAni) nanorods doped with organic camphorsulfonic acid (CSA) and inorganic hydrochloric acid (HCl) synthesized by interfacial polymerization technique. High resolution transmission electron micrographs (HRTEM) depict that initially spherical nuclei directionally grow into nanorods and CSA doped PAni produces more uniform and aligned structures. The electrical transport studies reveal that the CSA doped nanorods follow 1D Mott variable-range hopping (VRH), whereas the HCl doped nanorods exhibit 2D VRH conduction mechanism. The value of interchain charge transfer integral is found to be higher for smaller size HCl doped PAni than that for larger size CSA doped PAni. The resistivity measurements exhibit semiconducting behavior for both organic and inorganic dopants and the resistivity of the CSA doped nanorods is found to be smaller than that of the HCl doped nanorods. The dielectric relaxation studies suggest Debye type relaxation with a single relaxation peak for both the dopants and the relaxation time of the carriers of the CSA doped PAni nanorods is smaller than that of the HCl doped nanorods.     

Electrical sterilization of Escherichia coli by electrostatic atomization with a photo-chemical catalyst

The inactivation of Escherichia coli (E. coli) was studied to find the optimal sterilization conditions using electrostatic atomization with a near ultraviolet light-emitting diode (near UV-LED) and TiO₂ nanofiber films. Three types of near UV-LEDs of different wavelengths (365 nm, 375 nm, 385 nm) were used in this investigation. In order to enhance the LED performances, TiO₂ nanofiber films were utilized for the production of a photo-chemical catalytic effect. In these studies, the flow rate condition of the E. coli mixture was varied from 2 ml/h to 10 ml/h for the purposes of measuring the capabilities of the proposed sterilization method. During these electrostatic atomization experiments, Each LED irradiated a TiO₂ nanofiber film and atomized E. coli mixture. The results of these experiments were compared with electrostatic atomization performed without the use of photo-chemical catalyst effects. The experimental result shows that the optimal sterilization effect of E. coli is 375 nm wavelength with a TiO₂ nanofiber employed during electrostatic atomization.     

Long range ordering in self-assembled Ni arrays on patterned Si

We have succeeded in aligning self-assembled structures by using a lithographically defined stripe. The 140 nm wide by 100 nm high SiO₂ strip is shown to guide the assembly of 500 nm latex spheres so that spheres are aligned along the strip and are in registration on either side of the strip. This method can be used to increase long-range ordering in magnetic storage systems without compromising the density. Inverse sphere Ni arrays were made by electrodeposition through the latex template. We also show that the hexagonal symmetry of the resulting inverse sphere Ni arrays can be simulated using the approach presented below.     

Self-assembled structures of 4′-([2,2′:6′,2″-terpyridine]-4′-yl)-[1,1′-phenyl]-4-carboxylic acid molecules induced by metal atoms on ag(111) surface

The self-assembled supramolecular structures of 4′-([2,2′:6′,2″-terpyridine]-4′-yl)-[1,1′-phenyl]-4-carboxylic acid (Y) molecules on Ag(111) surface induced by metal elements have been studied by scanning tunneling microscopy. After annealing, the as-deposited monolayer of Y molecules shows four kinds of well-ordered structures due to the competition between dipole interaction, hydrogen bonding and Van der Waals interaction. Introduced Cu atoms drive ordered monolayer into a self-assembled supramolecular structure with bright spots. Deposited Ag atoms cause the monolayer change to a windmill shape self-assembled supramolecular structure. Though the Cu and Ag are in the same group of the periodic table, a Cu atom connects two COOH groups and an Ag atom trends to bind to three COOH groups during the formation of metal-organic bonding within both induced structures. Such result suggests that the self-assembled structures formed by metal-organic coordination bonding can be controlled by choosing the number of metal-organic coordination bonds, which can be helpful to design metal-organic molecular architectures comprising functional building blocks.     

Theoretical and Experimental analysis of ZnPc for its local ordering and electronic structure

Zinc Phthalocyannine (ZnPc) has been investigated intensely for fabricating plastic solar cells, and there are very limited reports available relating molecular structure and its corresponding macroscopic properties linked with simulation and electronic structure. In fact, our previous reports have demonstrated a partial ordering of the ZnPc molecules [1]. As a continuation of our previous work, we report here the structural determination of atomic and electronic distribution in this material, and a detailed analysis of its involvement in interactions that produce local domains in partial periodic structures. The use of high resolution transmission electron microscopy (HRTEM) and digital processing based on the frequency selection allowed us to distinguish the contrast from local arrays of fringes with distances around 0.37 and 0.35 nm between them. From the quantum mechanical calculations and approximations for single molecules and from classical molecular mechanics for two to six molecule arrays, we identified the type of ordering and the effects on the corresponding frontier orbital (HOMO and LUMO) and the electrostatic potential. The calculated models and a simulation of the HRTEM images demonstrate that the molecular arrays observed in the samples are determined by the electrostatic interactions and the production of arrays influence significantly the optical and electronic properties of the ZnPc material. PACS 84.60.Jt; 87.64.Ee; 02.70.Ns; 03.65.2w     

Large-scale boron nanowire nanojunctions and their highly-oriented arrays

One-dimensional (1D) nanostructures, such as nanotubes and nanowires, have gen-erated worldwide interest due to their nano-scale sizes, high length-to-diameter ratios, highly anisotropic properties, various unique structures, and wide technological applica-tions. 1D nanostructures are the smallest dimension structures that can be used for effi-cient transport of electrons, vacancies, and excitations, and are thus critical building blocks in the construction of nanoscale electronic and mechanic…     

Efficient suppression of radiation damping in individual plasmonic resonators: towards high‐Q nano‐volume sensing

Recent results on radiation damping suppression in individual plasmonic resonators using conformal bending of the structure, which suppresses the electric‐dipole response in favor of magnetic dipole one, are overviewed. It is demonstrated that bending of linear plasmonic nano‐antennas increases significantly their Q factors above the electrostatic limit while preserving the nature of resonance along with its exceptional features, such as linear size‐dependent tunability and robust field enhancement. The approach, which makes use of strong lateral confinement exhibited by the slow plasmonic modes (slow‐SPPs) bound to ultra‐narrow metallic structures, turned out to be quite general, and its experimental demonstration has been attained with circularly curved nano‐rod antennas. Furthermore, this approach suggested novel configurations of plasmonic single particle nanosensing with enhanced features, allowing record‐high figures of merit along with unprecedented spatial resolution in nanofiber‐based split‐cylinder structures.     

Synthesis of bismuth nanocap arrays on quartz substrates and their surface plasmon resonance properties

Bismuth nanocap arrays have been prepared by vacuum depositing Bi films onto the surfaces of self-assembled monolayer arrays of SiO₂ nanoparticles. The surface morphologies, structures, and optical properties of the obtained samples have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), and ultraviolet–visible–near infrared (UV–vis–NIR) spectrophotometer. TEM and AFM images indicated that the SiO₂/Bi composite nanoparticles were incompletely encapsulated and their surfaces were relatively rough. UV–vis–NIR absorption spectra showed that Bi nanocap arrays had strong and tunable surface plasmon resonance peaks in the visible and near infrared regions, which were dependent dramatically on the relative ratio of the SiO₂ core diameter to the Bi cap thickness.     

Device applications of self-assembled monolayers and monolayer-protected nanoclusters

The present status of self-assembled monolayers (SAMs) on different surfaces (2D systems) as well as monolayer formation on metallic and semiconducting cluster surfaces (3D SAM) to form monolayer-protected nanoclusters (MPCs) and their assemblies is reviewed briefly. Attention is focused mainly on the potential electronic and photonic applications of SAMs, MPCs and their 2D and 3D structures fabricated using covalent and hydrophobic interactions in contrast to the usual electrostatic assemblies. These examples illustrate the rational use of organic molecules and nanoclusters using the concept of self-assembly, where subtle systems of double tunnel junctions, hetero junctions and single-electron transition devices could be developed based on the structure and chemistry of multifunctional molecules. The tailoring of cluster size and cluster–cluster spacing to reveal interesting transitions in electronic properties is also demonstrated using the low temperature behavior of the 3D network of nanoclusters as an example. These devices are believed to play an important role in the coming years as the chip functions and clock frequencies reach orders of magnitude beyond those extrapolated from Moore’s law.     

氧等离子体处理对GaAs表面单层自组装SiO2纳米球薄膜的影响

二维纳米阵列结构因其重要的光学性能被广泛应用于各类光电子器件。本文对自组装单层SiO2纳米球掩模刻蚀法制备GaAs纳米柱二维阵列结构的关键工艺技术进行了研究。采用旋涂法在GaAs表面制备自组装单层SiO2纳米球,重点研究了GaAs表面氧等离子体亲水处理工艺对纳米球排列特性的影响,获得最佳工艺条件为功率配比100 W+80 W、腔室压力4 Pa、氧气流量20 mL/min、处理时间1200 s,并最终得到排列紧密的大面积单层纳米球薄膜。以单层纳米球为掩模,采用感应耦合等离子体刻蚀技术在GaAs表面制备了纳米柱阵列并测试了其表面光反射谱。测试结果表明,GaAs纳米柱阵列在特定波段的反射率降低至5%,远低于表面无纳米结构的薄膜材料表面高达40%的光反射。分析表明纳米柱可以激发米氏散射共振效应,从而有效降低反射率并提升光吸收。