Fabrication of arrays of silver nanoparticle aggregates by microcontact printing and block copolymer nanoreactors

A combination of microcontact printing and block copolymer nanoreactors succeeded in fabricating arrays of silver nanoparticle aggregates. A complex solution of polystyrene‐block‐poly(4‐vinylpyridine) micelles and silver salt was used as an ink to form thin films or droplets on polydimethylsiloxane stamp protrusions. After these complex aggregates were printed onto silicon substrates under controlled conditions, highly ordered arrays of disklike, dishlike, and dotlike complex aggregates were obtained. A subsequent oxygen reactive ion etching treatment yielded arrays of silver nanoparticle aggregates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2737–2743, 2006     

磁性纳米线阵列的制备与应用

介绍了以多孔氧化铝(AAO)和刻蚀高聚物为模板制备磁性纳米线阵列的方法,包括溶胶-凝胶法、化学沉积法和电沉积法等.结合磁性纳米线的研究现状,展望了磁性纳米线阵列在磁记录、巨磁电阻、量子磁盘和高密度磁存储等方面的应用前景.     

Fabrication of honeycomb-structured protein arrays via one-step method

“Inverse emulsion”-“breath figures” (Ie-BF) method was introduced for fabricating porous films with protein arrays decorating the interior of the obtained polymeric pores. Compared with the traditional BF method in which only hydrophobic or amphiphilic components could be used, Ie-BF method created a system with water phase carrying water-soluble protein before solution casting, which makes it possible to obtain patterned protein arrays within the BF structure in one-step. The stability of the inverse emulsion system is an intractable problem solved by high shearing emulsification. Experimental parameters, including the concentration of the matrix polymer, water/oil ratio of the IE, amount of both emulsifier and protein in IE, were evaluated for establishing an optimal condition to prepare fine BF arrays by following the Ie-BF method. Proteins tagged with fluorescein isothiocyanate were added into the emulsion to cast films, and pores efficiently enriched by proteins were revealed by the images of fluorescence microscope, indicating the successful preparation of protein arrays. Among all the approaches of establishing patterned structures of biomacromolecules, Ie-BF shows promising potential in future applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47084.     

Fabrication of conjugated polymer arrays by spinodal dewetting

Ordered arrays of conjugated poly(9,9‐dihexylfluorene) (PF) were prepared by the spinodal dewetting of liquid thin films on mica substrates. The size of the aggregates in the arrays was controlled by the evaporation rate of the solvent. Fast solvent evaporation resulted in smaller aggregates; slower evaporation resulted in larger aggregates. The photoluminescence of the PF arrays showed a smaller red‐shift than that of the unpatterned film when compared to PF solutions, which indicated that the aggregation of PF in the arrays is smaller than that in the unpatterned films. Copyright © 2004 Society of Chemical Industry     

Fabrication of multi-level carbon nanotube arrays with adjustable patterns

Multi-level carbon nanotube (CNT) arrays with adjustable patterns were prepared by a combination of the breath figure (BF) process and chemical vapor deposition. Polystyrene-b-poly(acrylic acid)/ferrocene was dissolved in carbon disulfide and cast onto a Si substrate covered with a transmission electron microscope grid in saturated relative humidity. A two-level microporous hybrid film with a block copolymer skeleton formed on the substrate after evaporation of the organic solvent and water. One level of ordered surface features originates from the contour of the hard templates; while the other level originates from the condensation of water droplets (BF arrays). Ultraviolet irradiation effectively cross-linked the polymer matrix and endowed the hybrid film with improved thermal stability. In the subsequent pyrolysis, the incorporated ferrocene in the hybrid film was oxidized and turned the polymer skeleton into the ferrous inorganic micropatterns. Either the cross-linked hybrid film or the ferrous inorganic micropatterns could act as a template to grow the multi-level CNT patterns, e.g. isolated and honeycomb-structured CNT bundle arrays perpendicular to the substrate.     

Fabrication and electrical conductivity of suspended carbon nanofiber arrays

We demonstrate a simple, efficient and novel self-assembly based method to fabricate arrays of suspended polymeric nanofibers of polyacrylonitrile and SU-8 negative photoresist by electrospinning on micro-fabricated posts of resorcinol–formaldehyde (RF) gel. The suspended electrospun nanofibers together with the RF gel posts were subsequently pyrolyzed in an inert atmosphere to yield large area monolithic structures of suspended glassy carbon nanofibers (CNF) integrated on RF gel derived carbon posts. The electrospun nanofibers self-assemble to connect the posts owing to a stronger electric field on their tips, obviating the need for positioning and integration of carbon nanowires with the underlying microstructures and paving the way for fabricating novel carbon based micro and nanoscale devices. The fabrication technique also allowed measurements of electrical conductivity of a single suspended CNF between carbon electrodes using I–V characteristics and comparison of the carbon nanowire conductivities for the CNF derived from different polymer precursors.     

Fabrication of vertically aligned ferroelectric polyvinylidene fluoride mesoscale rod arrays

We have fabricated vertically aligned ferroelectric PVDF mesoscale rod arrays comprising β and γ phases using a 200 nm diameter anodized aluminum oxide (AAO) as the porous template. We could synthesize the ferroelectric phase in mesoscale rod forms by combining the well‐established recipe for crystallizing the β phase using dimethyl sulfoxide (DMSO) at low temperature and template‐guided infiltration processing for the rods using AAO. We measured the dimensions of the PVDF rods by scanning electron microscopy and identified the polymorph phases by X‐ray diffraction and Fourier transform infrared spectroscopy. The length of the rods varied from 3.82 μm to 1.09 μm and the diameter from 232 nm to 287 nm when the volume ratio between DMSO and acetone changed from 5 : 5 to 10 : 0. We obtained well‐defined piezoresponse hysteresis loops for all rods with remnant piezoresponse ranging from 2.12 pm/V to 5.04 pm/V and coercive voltage ranging from 2.29 V to 2.71 V using piezoresponse force microscopy. Our results serve as a processing platform for flexible electronic devices that need high capacitance and piezoelectric functionalities such as flexible memory devices or body energy harvesting devices for intelligent systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3842–3848, 2013     

Fabrication and spectroscopic investigation of branched silver nanowires and nanomeshworks

Wide wavelength ranges of light localization and scattering characteristics can be attributed to shape-dependent longitude surface plasmon resonance in complicated nanostructures. We have studied this phenomenon by spectroscopic measurement and a three-dimensional numerical simulation, for the first time, on the high-density branched silver nanowires and nanomeshworks at room temperature. These nanostructures were fabricated with simple light-induced colloidal method. In the range from the visible to the near-infrared wavelengths, light has been found effectively trapped in those trapping sites which were randomly distributed at the corners, the branches, and the junctions of the nanostructures in those nanostructures in three dimensions. The broadened bandwidth electromagnetic field enhancement property makes these branched nanostructures useful in optical processing and photovoltaic applications.     

Fabrication of Pd-Ni alloy nanowire arrays on HOPG surface by electrodeposition

Pd-Ni alloy nanowires with diameters 50-300 nm and lengths of over 250 μm have been obtained by electrochemical step edge decoration (ESED). The fabrication by ESED is accomplished on highly oriented pyrolytic graphite by applying three potential pulses in succession: an oxidizing “activation” pulse, a reducing “nucleation” pulse, and a reducing “growth” pulse. The alloy composition is controlled by adjusting the ion concentration ratio of palladium and nickel, and the deposition processes. The scanning electron microscopy (SEM) images reveal that the alloy nanowires fabricated by this procedure are separate, parallel, and continuous. The composition of alloy nanowires can be controlled in the range of 8-15 wt.% Ni when the ion concentration ratio of palladium and nickel is 7:3 in the solution containing 70 mmol dm⁻³ Pd(NH₃)₄Cl₂. The reaction mechanism involves nucleation at potential of −1.1 V_SCE to −2.0 V_SCE and growth at potential of −0.3 V_SCE to −0.5 V_SCE.     

Fabrication and characterization of carbon nanotube arrays using sandwich catalyst stacks

A novel synthesis of carbon nanotubes for field-emitter arrays with a uniform field emission current is reported. Microwave plasma chemical vapor deposition and a unique structure of a sandwich catalyst stack are used to grow vertically aligned carbon nanotubes with a high density, uniform length and diameter. After being etched in a H₂/N₂-microwave plasma, the overall field emission current density from the prepared emitter arrays is 1.2 A/cm² at an electric field of 6.5 V/μm with stable and uniform emission characteristics. The threshold field is 3.2 V/cm, defined at an emission current density of 10⁻⁶ A/cm².     

Two-dimensional ZnO-NiO macroporous arrays: Fabrication, structure and electrical properties

Colloidal templating and pulsed laser deposition were combined to fabricate arrays of ordered two-dimensional macroporous ZnO-NiO thin films. The underlying principles involved in the formation of colloidal templates were investigated using Fourier transformations and radial distribution functions. The macroporous thin film consists of hollow half-spheres of nanocrystalline wurtzite ZnO and rock salt NiO. The electrical properties of macroporous ZnO-NiO thin films were investigated by impedance and DC current-voltage measurements. The electrical properties are controlled by the interfaces between oxide grains. The potential applications such as gas sensors and optics are discussed.     

Fabrication and evaluation of 1 Ah silver/metal hydride cells

Silver/metal hydride (Ag/MH) cells of about 1 Ah capacity have been fabricated and their discharge characteristics at different rates of discharge, faradaic efficiency, cycle life and a.c. impedance have been evaluated. These cells comprise metal–hydride electrodes prepared by employing 60 m powder of an AB₂-Laves phase alloy of nominal composition Zr_0.5Ti_0.5V_0.6Cr_0.2Ni_1.2 with PTFE binder on a nickel-mesh substrate as the negative plates and commercial-grade silver electrodes as the positive plates. The cells are positive limited and exhibit two distinct voltage plateaus characteristic of two-step reduction of AgO to Ag during their low rates of discharge between C/20 and C/10. This feature is, however, absent when the cells are discharged at C/5 rate. On charging the cells to 100% of their capacity, the faradaic efficiency is found to be 100%. The impedance of the Ag/MH cell is essentially due to the impedance of the silver electrodes, since MH electrodes offer negligible impedance. The cells may be subjected to a large number of charge–discharge cycles with little deterioration.     

Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices.     

Fabrication,characterization, and thermal property evaluation of silver nanofluids

Silver nanoparticles were successfully prepared in two different solvents using a microwave heating technique, with various irradiation times. The silver nanoparticles were dispersed in polar liquids (distilled water and ethylene glycol) without any other reducing agent, in the presence of the stabilizer polyvinylpyrrolidone (PVP). The optical properties, thermal properties, and morphology of the synthesized silver particles were characterized using ultraviolet-visible spectroscopy, photopyroelectric technique, and transmission electron microscopy. It was found that for the both solvents, the effect of microwave irradiation was mainly on the particles distribution, rather than the size, which enabled to make stable and homogeneous silver nanofluids. The individual spherical nanostructure of self-assembled nanoparticles has been formed during microwave irradiation. Ethylene glycol solution, due to its special properties, such as high dielectric loss, high molecular weight, and high boiling point, can serve as a good solvent for microwave heating and is found to be a more suitable medium than the distilled water. A photopyroelectric technique was carried out to measure thermal diffusivity of the samples. The precision and accuracy of this technique was established by comparing the measured thermal diffusivity of the distilled water and ethylene glycol with values reported in the literature. The thermal diffusivity ratio of the silver nanofluids increased up to 1.15 and 1.25 for distilled water and ethylene glycol, respectively.     

Fabrication of silver nanoparticles dispersed in palm oil using laser ablation

In this study we used a laser ablation technique for preparation of silver nanoparticles. The fabrication process was carried out by ablation of a silver plate immersed in palm oil. A pulsed Nd:YAG laser at a wavelength of 1064 nm was used for ablation of the plate at different times. The palm coconut oil allowed formation of nanoparticles with very small and uniform particle size, which are dispersed very homogeneously within the solution. The obtained particle sizes for 15 and 30 minute ablation times were 2.5 and 2 nm, respectively. Stability study shows that all of the samples remained stable for a reasonable period of time.     

Fabrication of CeO2@CdS sub-micron rod arrays for enhanced photoelectrochemical performance

Two-component CeO₂@CdS sub-micron rod arrays with enhanced photoelectrochemical properties were fabricated on Ti substrates by electrodeposition. And it is demonstrated that the enhanced photoelectrochemical properties, compared to those of the pristine CeO₂, are attributed to the suitable type-II band alignment of CeO₂@CdS and the favorable absorption properties of CdS shell.     

Fabrication of patterned carbon nanotubes with adjustable arrays through controlled mesoscopic dewetting

Here, we report the synthesis of aligned carbon nanotube (CNT) bundles with adjustable arrays by a non-lithographic and low-cost strategy. A polystyrene/ferrocene patterns on silicon (Si) substrate was prepared through controlled mesoscopic dewetting of dilute polystyrene/ferrocene solution. A variety of regular patterns, including ladder, stripe and scale, were synthesized simply by changing the solution concentration. Ultraviolet (UV) irradiation effectively cross-linked polymer skeleton and made it suitable for structure-directing agent. In the sequent pyrolysis, polystyrene skeleton was decomposed and ferrocene was converted into the skeleton of inorganic patterns simultaneously. Aligned CNT bundles guided by the catalytically functionalized inorganic patterns were initiated to grow. This methodology opens up a new avenue for fabricating CNT arrays in a simple and controllable manner.     

Fabrication of chalcogenide microlens arrays by femtosecond laser writing and precision molding

In this study, convex microlens arrays (MLAs) on chalcogenide glass (ChG) surface were fabricated through femtosecond laser direct writing and precision molding. Femtosecond laser writing was first employed to induce regularly arranged damage craters on the surface of silica glass. Then, the surface of silica was etched with hydrofluoric acid to obtain a smooth concave MLA. Finally, the concave microlens of silica was replicated on the surface of ChG by precision molding to obtain ChG MLA. The resulting ChG MLA had a uniform structure, clear image, and good focusing effect. By optimising the parameters of laser direct writing and chemical etching, we produced 1600 rectangular and hexagonal microlenses from As₂Se₃.The optical performances of MLAs were demonstrated by their excellent imaging and focusing capabilities. The method applied provides an efficient way to prepare large-scale MLA masks and MLAs.     

Fabrication and characterization of silver core and porous silica shell nanocomposite particles

The nanocomposite particles of silver core and silica shell have been successfully prepared. Silver colloids are synthesized using polymer polyvinylpyrrolidone (PVP) as protecting agent and the silica shell is then coated by means of the Stöber process to fabricate Ag@SiO₂ core shell particles. The shell thickness can be easily controlled by the amount of tetraethyl orthosilicate (TEOS). TEM results indicate that the silica shell uniformly encapsulates the silver core particles. During the silica growth, PVP molecules will be trapped and dispersed in the silica shell. As a result, porous silica shell structure is obtained after burning off the PVP molecules and a positive correlation exists between the specific surface area of core shell particles and PVP quantity in the original silver colloids. The silica shell, even at a thickness of 25 nm, can maintain the original shape of Ag@SiO₂ particles up to 1000 °C, and prohibit silver from sintering effects.