Boron-assisted growth of silica nanowire arrays and silica microflowers for bendable capacitor application

Aligned-long silica nanowire arrays and microflowers were synthesized with boron as catalyst. Besides that parallel plate capacitors were fabricated using the silica nanowire mat as a dielectric. Their frequency response and mechanical properties were investigated.     

Solution-based II-VI core/shell nanowire heterostructures

We demonstrate the solution-phase synthesis of CdS/CdSe, CdSe/CdS, and CdSe/ZnTe core/shell nanowires (NWs). On the basis of bulk band offsets, type-I and type-II heterostructures are made, contributing to the further development of low-dimensional heteroassemblies using solution-phase chemistry. Core/shell wires are prepared by slowly introducing shell precursors into a solution of premade core NWs dispersed in a noncoordinating solvent at moderate temperatures (215-250 degrees C). Resulting heterostructures are characterized through low- and high-resolution transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray analysis. From these experiments, initial shell growth appears to occur through either Stranski-Krastanov or Volmer-Weber island growth. However, beyond a critical shell thickness, nucleation of randomly oriented nanocrystals results in a polycrystalline coat. In cases where overcoating has been achieved, corresponding elemental analyses show spatially varying compositions along the NW radial direction in agreement with expected element ratios. Electronic interactions between the core and shell were subsequently probed through optical studies involving UV-vis extinction spectroscopy, photoluminescence experiments, and transient differential absorption spectroscopy. In particular, transient differential absorption studies reveal unexpected shell-induced changes in core NW Auger kinetics at high carrier densities. Previously seen three-carrier Auger kinetics in CdS (bimolecular in CdSe) NWs were suppressed by the presence of a CdSe (CdS) shell. These observations suggest the ability to influence NW optical/electrical properties by coating them with a surrounding shell, a method which could be important for future NW optical studies as well as for NW-based applications.     

Direct synthesis of porous NiO nanowall arrays on conductive substrates for supercapacitor application

Porous NiO nanowall arrays (NWAs) grown on flexible Fe-Co-Ni alloy have been successfully synthesized by using nullaginite (Ni₂(OH)₂CO₃) as precursor and investigated as supercapacitor electrodes. In details, we adopted a simple hydrothermal method to realize Ni₂(OH)₂CO₃ NWAs and examined their robust mechanical adhesion to substrate via a long-time ultrasonication test. Porous NiO NWAs were then obtained by a post-calcination towards precursors at 500 °C in nitrogen atmosphere. Electrochemical properties of as-synthesized NiO NWAs were evaluated by cyclic voltammetry and galvanostatic charge/discharge; porous NiO NWAs electrode delivered a specific capacitance of 270 F/g (0.67 A/g); even at high current densities, the electrode could still deliver a high capacitance up to 236 F/g (13.35 A/g). Meanwhile, it exhibited excellent cycle lifetime with ∼93% specific capacitance kept after 4000 cycles. These results suggest that as-made porous NiO NWAs electrode is a promising candidate for future thin-film supercapacitors and other microelectronic systems.     

Fabrication and characterization of mesoporous Co3O4 core/mesoporous silica shell nanocomposites

A mesoporous Co(3)O(4) core/mesoporous silica shell composite with a variable shell thickness of 10-35 nm was fabricated by depositing silica on Co(3)O(4) superlatticed particles. The Brunauer-Emmett-Teller (BET) surface area of the composite with a shell thickness of ca. 2.0 nm was 238.6 m(2)/g, which varied with the shell thickness, and the most frequent pore size of the shell was ca. 2.0 nm. After the shell was eroded with hydrofluoric acid, mesoporous Co(3)O(4) particles with a pore size of ca. 8.7 nm could be obtained, whose BET surface area was 86.4 m(2)/g. It is proposed that in the formation of the composite the electropositive cetyltrimethylammonium bromide (CTAB) micelles were first adsorbed on the electronegative Co(3)O(4) particle surface, which directed the formation of the mesoporous silica on the Co(3)O(4) particle surface. Electrochemical measurements showed that the core/shell composites exhibited a higher discharge capacity compared with that of the bare Co(3)O(4) particles.     

Silver nanowires-copper sulfide core/shell nanostructure for electrochemical supercapacitors

This paper reports the synthesis of a new hybrid core (silver nanowires (AgNWs))/shell (copper sulfide (Cu₂S)) nanostructure using simple and inexpensive drop casting and successive ionic layer adsorption and reaction (SILAR) methods. The effects of the thickness of the Cu₂S shell on the Ag NW core on the electrochemical properties of the nanocomposite were studied by varying the number of SILAR cycles from one to four. The structure and microstructure of the prepared composite nanostructure electrode materials were characterized by X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The AgNW/Cu₂S exhibited a high specific capacitance of 603 Fg^?1 (stainless steel substrate) and 707 Fg^?1 (Ni foam substrate) at a scan rate of 10 mVs^?1 with an energy density of 10.01 Whkg^?1 and 25.33 Whkg^?1 at an applied current of 0.2 mA. This study provides a simple and cost-effective strategy for the fabrication of nanostructured electrodes for supercapacitor applications.     

Fabrication and characterization of single-crystalline ZnTe nanowire arrays

Semiconductor ZnTe nanowire arrays have been synthesized by the pulsed electrochemical deposition from aqueous solutions into porous anodic alumina membranes. X-ray diffraction analyses show that the as-synthesized nanowires have a highly preferential orientation. Scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy indicate that high-filling, ordered, and single-crystalline nanowire arrays have been obtained. The optical absorption spectra of the nanowire arrays show that the optical absorption band edge of the ZnTe nanowire array exhibits a blue shift compared with that of bulk ZnTe. The growth mechanism and the electrochemical deposition process are discussed together with the chemical compositions analysis.     

GaP/GaPN核壳纳米线阵列修饰的硅光阴极的光电化学制氢反应（英文）

能够大规模同时提升电极的催化效率和稳定性对光电化学分解水系统的开发具有重要意义.硅是一种地球储量丰富且成熟的工业材料,由于其合适的带隙(1.1 eV)和优异的导电性,已被广泛用于光电化学制氢反应.然而,缓慢的表面催化反应和在电解液中的不稳定性限制了其在太阳能制氢中的实际应用.III-IV族半导体材料也具有较高的载流子传输特性且被广泛用于光电器件.其中,GaP的直接带隙和间接带隙分别为2.78和2.26 eV,可与硅组成串联型光电极用于光电化学分解水.然而,GaP的光腐蚀电位位于禁带中,很容易在光电催化过程中发生光腐蚀而导致性能大幅下降.本文报道了一种新型的GaP/GaPN核/壳纳米线修饰的p型硅(p-Si)串联型光阴极,同未修饰的p-Si相比,其光电化学制氢性能更高.这可归因于以下几点:(1)p-Si和GaP纳米线之间形成的p-n结促进了电荷分离;(2)GaPN相对于GaP具有更低的导带边位置,进一步促进了光生电子向电极表面的转移;(3)纳米线结构既缩短了光生载流子的收集距离,又增加了比表面积,从而加快了表面反应动力学.此外,在GaP中引入氮元素还提高了体系的光吸收和稳定性.我们所提出的高效、简便的改进策略可应用于其他的太阳能转换体系.利用简单的化学气相沉积法制备GaP/GaPN核/壳纳米线修饰的p-Si光阴极.首先在p-Si衬底上利用Au纳米颗粒作为催化剂生长GaP纳米线;然后,去除Au催化剂,并在氨气中退火便形成了GaP/GaPN核壳纳米线.高分辨透射电子显微镜,拉曼光谱和X射线光电子谱的表征结果均证实了氨气退火使得GaP纳米线表面形成了GaPN的薄壳层,同时证明了GaP/GaPN核壳纳米线具有可调的核壳结构.在模拟太阳光下作为光阴极用于光解水制氢反应时,GaP/GaPN核壳纳米线修饰的p-Si光阴极的起始电位为~0.14 V,而未修饰的p-Si电极的起始电位大约在?0.77 V.而且,GaP/GaPN核/壳纳米线修饰的p-Si光阴极比未修饰的p-Si光阴极具有更高的光电流密度,在水的还原电位下,其光电流密度为?0.3 mA cm^-2,且饱和光电流密度在?0.76 V时达到了?8.8 mA cm^-2.此外,GaP/GaPN核/壳纳米线修饰的p-Si光阴极的光电化学活性在10 h内没有发生明显下降.由此可见GaP/GaPN核/壳纳米线可以规模化有效地提升Si光电极的催化效率和稳定性.     

Fabrication of bimodal porous silicate with silicalite-1 core/mesoporous shell structures and synthesis of nonspherical carbon and silica nanocases with hollow core/mesoporous shell structures

In this work, an attempt has been made to modify the shape and nanostructure of core-shell materials, which have been usually generated on the basis of amorphous spherical cores. Novel core-shell silicate particles, each of which consists of a silicalite-1 zeolite crystal core and mesoporous shell (ZCMS), were synthesized for the first time. The ZCMS core-shell particles are unique because they are of pseudohexagonal prismatic shape and have hierarchical porosity of both a uniform microporous core and a mesoporous shell coexisting in a particle framework. The nonspherical bimodal porous core-shell particles were then utilized as templates to fabricate a new carbon replica structure. Interestingly, the pore replication process was carried out only through the mesopores in the shell, and not through the micropores due to the narrower micropore size in the core, resulting in nonspherical carbon nanocases with a hollow core and mesoporous shell (HCMS) structure. Nonspherical silica nanocases with HCMS structure were also generated by replication using the carbon nanocases as templates, which are not possible to synthesize through other synthetic methods. Interestingly, the pseudohexagonal prismatic shape of the zeolite crystals was transferred onto the carbon and silica nanocases.     

Ni/NiO core/shell nanoparticles for selective binding and magnetic separation of histidine-tagged proteins

Ni/NiO core/shell nanoparticles having high affinity with polyhistidine were synthesized by decomposition of a Ni surfactant complex followed by air oxidation. Ni/NiO nanoparticles showed selective and efficient binding to histidine-tagged proteins and easy separation by using a magnet. These provided a more convenient way to efficient purification of histidine-tagged proteins compared with the conventional Ni-NTA complex-bound resins and microbeads.     

A hierarchical porous MnO2-based electrode for electrochemical capacitor

A hierarchical porous MnO₂-based electrode was prepared and its electrochemical performance for electrochemical capacitors was investigated. In this work, porous MnO₂ film with pore size of 2?C3?nm in diameter was deposited on a three-dimensional porous current collector by cathodic electrodeposition associated with subsequent controlled heat treatment at 200°C for 2?h. Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the heat treatment has a great effect on the formation of the porous structure of MnO₂ layer, and the disordered porous structure was caused by dehydration during the heat treatment. Cyclic voltammetry and galvanostatic charge?Cdischarge tests showed that both energy and power densities are enhanced due to the unique hierarchical porous structure. The electrode delivers a high specific capacitance of 385?F?g^?1 at a high current density of 5?A?g^?1 within a potential window of ?0.05????0.85?V, and also exhibits excellent rate capability and electrochemical stability.     

以金纳米颗粒-二氧化钛纳米线阵列为支架的电化学免疫传感的构建及其应用

首先以掺杂氟的二氧化锡导电玻璃为基片,采用水热法制备出二氧化钛纳米线阵列,然后使用电化学沉积法将金纳米颗粒修饰于二氧化钛纳米线阵列表面以增强其导电性和生物相容性.将纳米金-二氧化钛纳米线阵列用作电化学免疫传感器支架,利用纳米金与癌胚抗原抗体之间的静电吸附作用,将包被抗体负载于电极表面制得检测癌胚抗原的电流型免疫传感器.同样,水热法还被用于制备圆柱形二氧化钛纳米棒,以辛二酸双(3-磺基-N-羟基琥珀酰亚胺酯)钠盐为双氨基交联剂,将辣根过氧化物酶和信号抗体一起固定于二氧化钛纳米棒表面作为示踪标记物.扫描电子显微镜、透射电子显微镜和X射线衍射分析仪均被用于分析上述材料的结构、形貌和组成.通过夹心型免疫反应,示踪标记物上信号抗体被定量负载于免疫传感器表面.通过一个以过氧化氢为媒介体的辣根过氧化物酶催化反应,差示脉冲伏安法被用于癌胚抗原的定量测定.结果表明,该癌胚抗原免疫传感器线性范围为0.01~120μg/L,检测限为6 ng/L.     

2D self-organization of core/shell Co(hcp)/Co nanocrystals

In this paper we report the preparation of ordered hexagonal 2D arrays of core/shell Cohcp/CoO nanocrystals. A full structural investigation has been carried out using high-resolution transmission electron microscopy, electron diffraction, and electron energy-loss spectroscopy.     

Fabrication of silica nanotube arrays from vertical silicon nanowire templates

A simple thermal oxidation-etching process was developed to translate vertical silicon nanowire arrays into silica nanotube arrays. The obtained nanotubes perfectly retain the orientation of original silicon nanowire arrays. The inner tube diameter ranges from 10 to 200 nm. High-temperature oxidation produces relative thick, rigid, and pinhole-free walls that are made of condensed silica. This method could be useful for fabrication of single nanotube sensors and nanofluidic systems.     

Cagelike polymer microspheres with hollow core/porous shell structures

Submicron‐scaled cagelike polymer microspheres with hollow core/porous shell were synthesized by self‐assembling of sulfonated polystyrene (PS) latex particles at monomer droplets interface. The swelling of the PS latex particles by the oil phase provided a driving force to develop the hollow core. The latex particles also served as porogen that would disengage automatically during polymerization. Influential factors that control the morphology of the microspheres, including the reserving time of emulsions, polymerization rate, and the Hildebrand solubility parameter and polarity of the oil phase, were studied. A variety of monomers were polymerized into microspheres with hollow core/porous shell structure and microspheres with different diameters and pore sizes were obtained. The polymer microspheres were characterized by scanning electron microscopy, transmission electron microscopy, optical microscopy, and Fourier transform infrared spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 933–941, 2007     

From colloidal Co/CoO core/shell nanoparticles to arrays of metallic nanomagnets: surface modification and magnetic properties.

The magnetic properties of nanoparticles can be subject to strong variations as the chemical composition of the particle surface is modified. To study this interrelation of surface chemistry and magnetism, self-assembled layers of colloidal 9.5 nm Co/CoO core/shell nanoparticles were exposed to mild reactive hydrogen and oxygen plasmas. The consecutive oxygen/hydrogen plasma treatment transforms the particle layer into an array of metallic nanomagnets with complete reduction of the oxide and removal of the organic surfactants. The original arrangement of the particle array and the number of Co atoms per particle remains unchanged within the experimental error, and thus this is a possible route for the fabrication of ultrahigh-density magnetic bit structures from colloidal dispersions. The magnetic properties can be tuned by controlling the thickness of the surface oxide layer, which magnetically hardens the particles, as evidenced by element-specific magnetic hysteresis loops.     

Fabrication and electrochemical characterization of interdigitated nanoelectrode arrays

Interdigitated nanoelectrode arrays with controlled electrode bandwidth and gap geometries ranging from 30 nm to 1 μm were fabricated on glass substrates by a planar process involving high resolution electron beam lithography and lift-off, and their characteristic electrochemical responses to an aqueous ferrocene derivative solution were examined using fundamental electrochemical techniques. Despite the comparatively large electrode area of electrode arrays containing 10 bands to a single band electrode, quasi-steady-state currents with high current density were obtained at a slow potential sweep rate in cyclic voltammograms of ferrocene derivative since the lateral dimension of the nanoelectrode arrays was considerably less than the scale of the diffusion layer of redox species. Additionally, it was demonstrated that the electrode thickness influenced limiting currents of voltammograms in the case of nanoelectrode arrays. In generation-collection mode experiments, furthermore, a collection efficiency as high as ∼99% was attained by 100 nm wide electrode arrays with a gap dimension of 30 nm.     

Fabrication and characterization of core/shell structured TiO2/polyaniline nanocomposite

A novel core/shell structured TiO(2)/polyaniline nanocomposite was fabricated by grafting aniline on aminobenzoate monolayer that is chemically adsorbed on the TiO(2) nanocrystal surface. The formation and nanostructure of the nanocomposite were investigated by FT-IR and UV-Vis spectra, TEM, FE-SEM, and TG-DTA analysis. Adsorption of aminobenzoate on the TiO(2) surface is an effective method to obtain the uniform nanocomposite. The thickness of polyaniline layer coating on the TiO(2) nanocrystal surface can be controlled in a range of 2-5 nm by this method. A photoelectrochemical study was carried out on the TiO(2)/polyaniline nanocomposite, and found that polyaniline in the nanocomposite acted as a visible-light sensitizer in a photoelectrochemical reaction. The sensitization effect increased with increasing binding strength between polyaniline and TiO(2). A dye-sensitized solar cell with a short circuit current density of 0.19 mA/cm(2) and an open circuit voltage of 0.35 V was fabricated by using the TiO(2)/polyaniline nanocomposite film as a sensitized electrode.     

Fabrication of CdS/PMMA core/shell nanoparticles by dispersion mediated interfacial polymerization

CdS/PMMA core/shell nanoparticles were synthesized using dispersion-mediated interfacial polymerization, and the transparent PMMA shell not only maintained the optical properties of CdS core but effectively protected the CdS core from environmental perturbation.     

TiC/C core/shell nanowires arrays as advanced anode of sodium ion batteries

High-perfo rmance anodes of sodium ion batteries(SIBs)largely depends on rational architecture design and binder-free smart hybridization.Herein,we report TiC/C core/shell nanowires arrays prepared by a one-step chemical vapor deposition(CVD)method and apply it as the anode of SIBs for the first time.The conductive TiC core is intimately decorated with carbon shell.The as-obtained TiC/C nanowires are homogeneously grown on the substrate and show core/shell heterostructure and porous architecture with high electronic conductivity and reinforced stability.Owing to these merits,the TiC/C electrode displays good rate performance and outstanding cycling performance with a capacity of 135.3 mAh/g at 0.1 A/g and superior capacity retention of 90.14%after 1000 cycles at 2 A/g.The reported strategy would provide a promising way to construct binder-free arrays electrodes for sodium ion storage.