In situ STM studies of electrochemical growth of nanostructured Ni films and their anomalous IR properties

We have extended the study of anomalous IR properties, which were initially discovered on nanostructured films of platinum group metals and alloys, to nanostructured films of nickel, a member of the iron group triad, and broadened the fundamental knowledge on this subject. Nanostructured thin films of nickel supported on glassy carbon [nm-Ni/GC(n)] were prepared by electrochemical deposition under cyclic voltammetric conditions, and the thickness of films was altered systematically by varying the number (n) of potential cycling within a defined potential range for electrodeposition. Electrochemical in situ scanning tunneling microscopy (STM) was employed to monitor the electrochemical growth of nanostructured Ni films. These in situ STM images illustrated that, along the increase of the film thickness, Ni films have undergone a transformation from layer structure to island structure and finally to lumpish arris structure. Investigations by in situ FTIR spectroscopy employing adsorbed CO as the probe revealed that these nanostructures of Ni films yield abnormal IR features, Fano-like IR features, and normal IR features, respectively. The IR bands of CO adsorbed on Ni thin films of a layer structure were inverted in their direction and enhanced in their intensity up to 15.5 times on an nm-Ni/GC(4) electrode. The Fano-like IR features, which are defined as a bipolar band with its negative-going peak on the low wavenumber side and its positive-going peak on the high wavenumber side, are observed for the first time on Ni thin films of an island nanostructure, i.e., at the nm-Ni/GC(16) electrode. IR features changed to normal absorption in CO adsorbed on the nm-Ni/GC(25) electrode, i.e., that with lumpish arris nanostructured Ni film of a larger thickness.     

Hierarchical structured Ni nanoring and hollow sphere arrays by morphology inheritance based on ordered through-pore template and electrodeposition

Fabrication of micro/nano-hierarchical Ni ordered nanostructured arrays is demonstrated by electrochemical deposition on the ordered alumina through-pore template induced by solution-dipping the colloidal monolayer. The morphology of the Ni nanostructured arrays exhibits a ringlike or hollow spherical structure depending on the template geometry and appropriate deposition parameters. The skeletons of the arrays are of floc- or flakelet-like fine structure on the nanoscale. The formation of such morphologies is attributed to the preferential growth along the inner wall of the alumina pores, while the nanoflakelet fine structure originates from a morphology inheritance process or the transitional product Ni(OH)2 which leads to the final nanostructured Ni crystals. This morphology inherence could be useful in the field of nanofabrication. Such micro/nano-hierarchically structured arrays show good magnetic properties and will find applications in the fields of catalysis, magnetics, optoelectrics, surface-enhanced Raman scattering (SERS), and new nanodevices.     

A "non-sticky" superhydrophobic surface prepared by self-assembly of fluoroalkyl phosphonic acid on a hierarchically micro/nanostructured alumina gel film

A hierarchically micro/nanostructured alumina gel film was prepared by using a simple sol-gel process; upon self-assembly of fluoroalkyl phosphonic acid, a "non-sticky" superhydrophobic surface was obtained.     

Flexible Broadband Light Absorbers with a Superhydrophobic Surface Fabricated by Ultraviolet-assisted Nanoimprint Lithography

We present a simple approach to fabricate a kind of composite films with a superhydrophobic and broadband light absorbing surface by ultraviolet-assisted nanoimprinting over a gradiently deposited composite matrix. The wettability and optical property of the resultant surfaces are tunable by the deposition time before polymerization(T_s) and mold's topography. Mechanically robust and elastomeric films exhibiting high sunlight absorptivity up to 98.13% and contact angle of their surfaces up to 150° are prepared under optimized conditions, as using a mold with a small pattern size(hexagonal periodic mold with cylinder diameter of ca. 37 μm) under T_s=10 min for imprinting the crosslinked poly[di(ethylene glycol) ethyl ether acrylate] and poly(isobornyl acrylate) in the presence of polypyrrole(PPy) nanoparticles. Such dual functions are found related to the hierarchical architecture of the surface, arising from the synergetic effects of the periodical patterned polymer substrate and spontaneously assembled PPy microstructures on the patterns. The current strategy based on the combination of ultraviolet-assisted nanoimprint lithography and hierarchical assembly of gradiently deposited black nano-fillers offers a new insight into the design of robust superhydrophobic and black surfaces, which is helpful to deepen our understanding of the relationship between liquid/light manipulation and micro/nanostructured surfaces.     

Electrochemical synthesis of nanostructured ZnO films utilizing self-assembly of surfactant molecules at solid-liquid interfaces

An electrochemical synthesis strategy for the production of nanostructured films was developed by combining self-assembly of surfactant-inorganic aggregates at solid-liquid interfaces and an electrodeposition process. Through this approach high quality nanostructured ZnO films were cathodically deposited from a plating solution containing 0.1 wt % of sodium dodecyl sulfate (SDS). The resulting ZnO films possess lamellar structures with two different repeat distances, d001 = 31.7 A and d001* = 27.5 A, both of which feature well-defined long range order. Due to kinetically controlled surfactant-inorganic assembly during the deposition process, the film exhibits a wide distribution of the stacking directions of the ZnO layers, which will allow facile access of the guest molecules and analytes to the interlayers. The synthetic mechanism used here can be generalized to generate nanostructured films of other semiconducting and metallic materials with architectures that cannot be assembled by other means.     

The electrochemistry of nanostructured Ni–W alloys

This work reports on the features that Ni–W nanostructured alloys, electrodeposited on carbon steel by different current pulse programs, may present depending on their surface morphology and surface composition. The Ni–W nanostructured coating, with a cauliflower structure, lack of fragility, and high WO₃/W surface composition ratio, is a stable electrode to catalyze hydrogen evolution reaction, exceeding bulk and electrodeposited Ni catalytic activity. Also, the nanostructured alloys must have a low WO₃/W surface composition ratio for Ni and its oxides to provide protection and improve corrosion resistance in sulfate media.     

微图案化钙磷盐膜层的电化学构筑及其生物性能

基于表面分子自组装和光催化转印技术,在TiO2膜层表面获得超亲/超疏水阵列微图案模板,结合电化学沉积技术,成功制备了微图案化钙磷盐膜(CaP)层.扫描电子显微镜(SEM)和电子探针分析(EPMA)结果表明,通过超亲/超疏水阵列微图案模板可构筑高空间分辨的微图案化钙磷盐膜层.微图案化钙磷盐膜层的体外MG-63细胞培养证实,细胞对钙磷盐膜层微单元有强烈的选择性粘附作用,从而可望控制细胞在微单元中的贴壁生长,实现高通量评价细胞行为.     

Corrosion resistance and durability of superhydrophobic surface formed on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution

The corrosion resistant performance and durability of the superhydrophobic surface on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution were investigated using electrochemical and contact angle measurements. The durability of the superhydrophobic surface in corrosive 5 wt% NaCl aqueous solution was elucidated. The corrosion resistant performance of the superhydrophobic surface formed on magnesium alloy was estimated by electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements and appropriate equivalent circuit models revealed that the superhydrophobic surface considerably improved the corrosion resistant performance of magnesium alloy AZ31. American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the superhydrophobic film to the magnesium alloy surface. The corrosion formation mechanism of the superhydrophobic surface formed on the magnesium alloy was also proposed.     

Electrochemical fabrication of multiplicate palladium hierarchical architectures and their electrocatalysis toward oxidation of formic acid

Dendritic, cactoid, splintery flowers-like and spinous flowers-like micro/nano-Pd hierarchical architectures were successfully deposited on the conductive substrates without assistance of any templates. Distinct from other general electrodeposition at a constant potential or cyclic potential, we utilized pulse potentials as deposition and dissolution potential, which were controlled by a simple and convenient electrochemical method—differential pulse amperometry. It was found that the morphologies of these novel micro/nanoparticles could be regulated with different pulse potentials. The resulting nanostructures were characterized by scanning electron microscopy and X-ray diffractometry. The results show that series of Pd micro/nanoparticles were bounded on the different index facets. It means that the growth direction could be effectively controlled by regulating the pulse potentials. Moreover, the as-synthesized Pd micro/nanoparticles also exhibited strikingly difference in catalytic activity toward electrooxidation of formic acid.     

Markedly controllable adhesion of superhydrophobic spongelike nanostructure TiO2 films

A simple electrochemical and self-assembly method was adopted for the fabrication of superhydrophobic spongelike nanostructured TiO2 surfaces with markedly controllable adhesion. Water adhesion ranging from ultralow (5.0 microN) to very high (76.6 microN) can be tuned through adjusting the nitro cellulose dosage concentrations. The detailed experiments and analyses have indicated that the significant increase of adhesion by introducing nitrocellulose is ascribed to the combination of hydrogen bonding between the nitro groups and the hydroxyl groups at the solid/liquid interfaces and the disruption of the densely packed hydrophobic 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PTES) molecule. A mechanism has been proposed to explain the formation of superhydrophobic TiO2 films with distinct adhesion.     

Controlling the wettability and adhesion of nanostructured poly-(p-xylylene) films

The hydrophobic surface properties of structured poly-(p-xylylene) (PPX) films, as measured by water wettability, are studied as functions of surface chemistry, film composition, and surface roughness. We demonstrate the fabrication of very hydrophobic surfaces and control over adhesion properties via nanoscale modulation of roughness, changes in composition, and alteration of the surface chemistry of PPX films. The formation of superhydrophobic surfaces through the chemisorption of fluoroalkylsiloxane coatings to hydroxyl sites created on the nanostructured PPX surface is also illustrated. The ability to control both hydrophobicity and adhesion using nanostructured PPX films is a promising development because it may lead to a new generation of coatings with applicability ranging from self-cleaning surfaces to robotics.     

Facile method to fabricate raspberry-like particulate films for superhydrophobic surfaces

A facile method using layer-by-layer assembly of silica particles is proposed to prepare raspberry-like particulate films for the fabrication of superhydrophobic surfaces. Silica particles 0.5 microm in diameter were used to prepare a surface with a microscale roughness. Nanosized silica particles were then assembled on the particulate film to construct a finer structure on top of the coarse one. After surface modification with dodecyltrichlorosilane, the advancing and receding contact angles of water on the dual-sized structured surface were 169 and 165 degrees , respectively. The scale ratio of the micro/nano surface structure and the regularity of the particulate films on the superhydrophobic surface performance are discussed.     

Fabrication of monometallic (Co,Pd, Pt,Au) and bimetallic (Pt/Au,Au/Pt) thin films with hierarchical architectures as electrocatalysts

Co thin films with novel hierarchical structures were controllably fabricated by simple electrochemical deposition in the absence of hard and soft templates, which were used as sacrificial templates to further prepare noble metal (Pd, Pt, Au) hierarchical micro/nanostructures via metal exchange reactions. SEM characterization demonstrated that the resulting noble metal thin films displayed hierarchical architectures. The as-prepared noble metal thin films could be directly used as the anode catalysts for the electro-oxidation of formic acid. Moreover, bimetallic catalysts (Pt/Au, Au/Pt) fabricated based on the monometallic Au, Pt micro/nanostructures exhibited the higher catalytic activity compared to the previous monometallic catalysts.     

From rolling ball to complete wetting: the dynamic tuning of liquids on nanostructured surfaces

In this work, for the first time, a dynamic electrical control of the wetting behavior of liquids on nanostructured surfaces, which spans the entire possible range from the superhydrophobic behavior to nearly complete wetting, has been demonstrated. Moreover, this kind of dynamic control was obtained at voltages as low as 22 V. We have demonstrated that the liquid droplet on a nanostructured surface exhibits sharp transitions between three possible wetting states as a function of applied voltage and liquid surface tension. We have examined experimentally and theoretically the nature of these transitions. The reported results provide novel methods of manipulating liquids at the microscale.     

Biomimetic superhydrophobic UHMWPE/nanosilica films with different sticky behavior on several metals

A kind of organic–inorganic composite film with biomimetic superhydrophobic performance was prepared on several metals including steel, aluminum, and copper. The organic matrix was ultrahigh‐molecular‐weight polyethylene (UHMWPE), and the inorganic filler was nanosilica. Scanning electron microscope observation indicated addition of nanosilica greatly changed the topography of the UHMWPE film. Special convexities were formed on the surfaces of the composite films, which made the composite films rougher than that of pure UHMWPE film. The nanosilica randomly scattered on the surface of the convexities and formed hierarchical structure similar to that of some plant leaves with superhydrophobic characteristics. Interestingly, it was found that there were remarkable differences between the sliding angles (SA) of water droplet on the composite films on different metals although the contact angles (CA) of water droplet on these films were quite close. The CA on the composite films on steel was about 157°, and the SA was larger than 90°, which demonstrated obvious superhydrophobic and sticky characteristic. But to the films on aluminum and copper, the CAs on them were larger than 160° and the SAs were between 3° and 4°, which meant excellent superhydrophobic and roll‐off performance. Scanning electron microscope observation indicated that there were some micro‐orifices in the film on steel and these micro‐orifices were connected to some extent. It was believed that these micro‐orifices provided capillary force and restrained sliding of water droplet. A sticky model based on capillary mechanism was proposed. Copyright © 2017 John Wiley & Sons, Ltd.     

Fabrication of CdS films with superhydrophobicity by the microwave assisted chemical bath deposition

A simple method of microwave assisted chemical bath deposition (MA-CBD) was adopted to fabricate cadmium sulfide (CdS) thin films. The superhydrophobic surface with a water contact angle (CA) of 151 degrees was obtained. Via a scanning electron microscopy (SEM) observation, the film was proved having a porous micro/nano-binary structure which can change the property of the surface and highly enhance the hydrophobicity of the film. A possible mechanism was suggested to describe the growth of the porous structure, in which the microwave heating takes an important role in the formation of two distinct characteristic dimensions of CdS precipitates, the growth of CdS sheets in micro-scale and sphere particles in nano-scale. The superhydrophobic films may provide novel platforms for photovoltaic, sensor, microfluidic and other device applications.     

Construction and corrosion behaviors of a bilayer superhydrophobic film on copper substrate

A novel bilayer superhydrophobic film was constructed on Cu substrate by a simple multi‐step process. First, (3‐mercaptopropyl) trimethoxysilane (MPTMS) molecules were self‐assembled onto the pre‐etched Cu surface via covalent bonding followed by hydrolysis and condensation, then 1H, 1H, 2H, 2H‐perfluorodecyltrichlorosilane (PFDTS) were grafted onto the resultant hydroxyl terminated surface via the Si‐O‐Si bonding. The so‐prepared sample was defined as Cu‐MPTMS‐PFDTS. The structure and morphology of the samples were characterized by means of contact angle measurement, X‐ray photoelectron spectroscopy and scanning electron microscopy. The corrosion behaviors of the films were evaluated by Tafel plot and electrochemical impedance spectroscopy on an electrochemical work station. The results indicated that the bilayer superhydrophobic film possessed better corrosion protection as compared with the control samples. The superiority of the corrosion protection was mainly ascribed to the following two aspects: the superhydrophobicity and polysiloxane micro‐structures of the Cu‐MPTMS‐PFDTS. Copyright © 2012 John Wiley & Sons, Ltd.     

Developments in nanostructured LiMPO4 (M = Fe, Co, Ni, Mn) composites based on three dimensional carbon architecture

Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. This review describes recent developments in the synthesis and characterization of composites which consist of lithium metal phosphates (LiMPO(4), M = Fe, Co, Ni, Mn) coated on nanostructured carbon architectures (unordered and ordered carbon nanotubes, amorphous carbon, carbon foams). The major goal of this review is to highlight new progress in using different three dimensional nanostructured carbon architectures as support for the phosphate based cathode materials (e.g.: LiFePO(4), LiCoPO(4)) of high electronic conductivity to develop lithium batteries with high energy density, high rate capability and excellent cycling stability resulting from their huge surface area and short distance for mass and charge transport.     

Electrochemical synthesis of nanostructured tellurium films

Direct templating of materials via lyotropic liquid crystalline mesophases of non-ionic surfactants provides an elegant and highly versatile route to the production of a wide range of nanostructured materials with well-defined mesoporous architectures of extended spatial periodicities. This technique has now been applied in the electrochemical synthesis of adherent nanostructured tellurium films. This represents an important step towards the synthesis of II–IV semiconductor compounds such as cadmium telluride. Low angle X-ray scattering and transmission electron microscopy (TEM) studies of the resulting tellurium films indicate the presence of a system of uniform cylindrical pores organized in an hexagonal array.     

Approach to excellent superhydrophobicity and corrosion resistance of carbon-based films by graphene and cobalt synergism

A new series of carbon-based films doped with graphene oxide and cobalt (G-Co/a-C:H films) were successfully prepared on Si substrate via one-step electrochemical deposition of methanol as the carbon source and graphene oxide/cobalt as the dopant. G-Co/a-C:H films were fabricated at various graphene oxide concentration for comparative experiments. It can be found that the graphene oxide and cobalt were well embedded in amorphous carbon matrix to form superhydrophobic G-Co/a-C:H film at the doping GO concentration of 0.007 mg/mL, which was confirmed by transmission electron microscopy (TEM). It was noted that the superhydrophobicity of the resulting surface derives from its rough surface with hierarchical micro-nanostructures and the presence of the low-surface-energy GO components on it. The hierarchical micro-nanostructures are attributed to the corporate joint of GO and cobalt to form the multilevel nanoscale composite interface. Specially, the as-fabricated superhydrophobic G-Co/a-C:H film could exhibit excellent self-cleaning ability and corrosion resistance, revealed by the self-cleaning and corrosion tests.