Template-free Electrochemical Deposition Research Articles

Investigation into thermoelectric performance of a flexible n-type nanocomposite film from the AgxSe nanotube composited with PPy

Silver selenide (Ag2Se) has turn up as a promising n-type thermoelectric (TE) material. Especially, the Ag2Se nanotubes may be more attractive in view of their one-dimensional hollow tubular nanostructure. Regrettably, the TE application of Ag2Se nanotubes has not yet been reported so far, probably due to their hard accessibility and poor processability. In this work, we developed a simple and efficient template-free electrochemical deposition method for preparing AgxSe nanotubes, and thus investigated the TE application of the AgxSe-nanotube films electrochemically composited with polypyrrole (PPy). It was found that the incorporation of PPy into the n-type AgxSe-nanotube films not only settled the issues of their high brittleness and easy oxidation, but also significantly improved their TE performance through the synergistic effects. Consequently, the AgxSe nanotube/PPy composite film achieved a maximum power factor of 282.8 ± 16.5 μW m−1 K−2, which is nearly twice that of the pure AgxSe-nanotube film.

Template-Free Electrochemical Growth of Ni-Decorated ZnO Nanorod Array: Application to an Anode of Lithium Ion Battery.

ZnO nanorods (NRs) decorated with Ni nanoparticles were synthesized using a template-free electrochemical deposition in an ultra-dilute aqueous electrolyte and a subsequent galvanic reaction. The electrochemical properties of the ZnO NRs as an anode material for rechargeable Li-ion batteries were evaluated for different binder morphologies (film and close-packed spherical particles) of polyvinylidene fluoride (PVDF). Results showed that the close-packed spherical PVDF simultaneously improved electrochemical capacity and cyclability because the free-volume between the spherical PVDF helped to accommodate the volume change in the anode caused by the Li ions discharge and charge processes. Furthermore, the Ni nanoparticles decorated on the surface of ZnO NRs enhanced the electrical conductivity of the ZnO NR anode, which enabled faster electronic and ionic transport at the interface between the electrolyte and the electrode, resulting in improved electrochemical capacity. The free-volume formed by the close-packed spherical PVDF, and the decoration of metal nanoparticles are expected to provide insight on the simultaneous improvement of electrochemical capacity and cyclability in other metal oxide anode nanostructures.

Template-free preparation of spherical Al particles in aluminum chloride and 1-butyl-3-methylimidazolium chloride ionic liquid

A template-free electrochemical deposition method for preparation of spherical-like Al particles in the aluminum chloride and 1-butyl-3-methylimidazolium chloride (AlCl3–[Bmim]Cl) system was reported in this work. Effects of current density, electrodeposition time, and temperature on surface morphologies of Al deposits were studied. Results showed that Al particles displayed uniform spherical-like morphology with the diameter range of 5–40 μm. Al particles presented irregular pie shaped with sizes ranged from 70 to 80 μm at low current densities of 2 and 10 mAcm−2. When the current density increased from 20 to 40 mAcm−2, particles tended to be spherical-like with sizes ranged from 10 to 20 μm. The particle size of deposits decreased with increasing current density on the same total amount of electric charges of 200 C due to the more compact arrangement of particles at high current density. The highest current efficiency reached at about 94%. Al particles were prepared at the current density of 40 mAcm−2 for a period time of 1000 s, 50 °C. The results of EDS analysis showed that the contents of the deposition were oxygen 5.79 wt.% and aluminum 94.21 wt.%. Almost spherical electrodeposition products about 50 g composed with pure metallic Al were obtained successfully in an amplified experiment finally.

Tuning the morphology of Te one-dimensional nanostructures by template-free electrochemical deposition in an ionic liquid

Template-free electrodeposition of Te one-dimensional (1D) nanostructures was carried out from an ionic liquid binary mixture: 1-ethyl-1-octyl-piperidinium bis(trifluoromethylsulfonyl)imide:1-ethyl-1-octyl-piperidinium bromide (EOPipTFSI:EOPipBr 95:5 (mol%)). SAED and XRD analyses confirm the formation of Te 1D nanostructures with a hexagonal single crystalline structure following the [001] direction. A systematic study of the influence of synthesis parameters on the deposits morphology has shown that it is possible to control the shape and the dimensions of the deposited nanostructures. Specifically, the applied potential has a strong influence on the morphology of the deposits. Nanowires or hollow nanostructures can be obtained, depending on mass transport conditions, as confirmed by the use of a soluble anode.

Piezoelectric properties of template-free electrochemically grown ZnO nanorod arrays

In this work, we evaluated the piezoelectric properties of the ZnO nanorods (NRs), subsequently grown by a template-free electrochemical deposition (ECD) approach. The one-step preparation method yielded in a relatively short-time synthesis large arrays of high aspect-ratio ZnO NRs, vertically aligned to the substrate and exhibiting a well-defined hexagonal symmetry coupled with an excellent crystallinity. Piezoresponse force microscopy (PFM) was employed to extract the effective piezoelectric coefficient (d33) of the ZnO [0001]-oriented NRs. A mean effective d33 coefficient of 11.8pm/V was measured over several individual NRs. The results have shown an increased piezoelectric response of the ZnO NRs, with ∼18% in respect to the ZnO bulk material, and with a factor ranging from 28% to 167% compared to similar ZnO nanostructures prepared by other counterpart techniques. Both morphology and crystalline quality of the obtained ZnO NRs, as well as the piezoelectric investigations, ranked the ECD as a promising low-cost pathway for possibly producing high quality nanostructured ZnO-based piezoelectric devices with enhanced performance.

Controllable Synthesis of ZnO Nanostructures via Template-Free Electrochemical Deposition at Low Temperature and their Optical Properties

We report template-free electrochemical deposition method for preparing ZnO nanostructures arrays on indium tin oxides (ITO) glass substrate. Multiform ZnO nanostructures, such as nanotubes, nanorods with tower-like tips, cone-like tips and groove-like tips, are controllably synthesized at 60 °C, which is lower compared with the prepared temperatures of reported works. The results of XRD indicate the wurtzite ZnO nanostructures are single-crystalline and grow along the c-axis perpendicularly on the substrate. These findings have potential for the growth of high-quality ZnO nanostructures arrays and device applications.

One-step large-scale synthesis of micrometer-sized silver nanosheets by a template-free electrochemical method

We have synthesized micrometer-sized Ag nanosheets via a facile, one-step, template-free electrochemical deposition in an ultra-dilute silver nitrate aqueous electrolyte. The nanosheet growth was revealed to occur in three stages: (1) formation of polygonal Ag nuclei on a substrate, (2) growth of {112}-faceted nanowire from the nuclei, and (3) anisotropic growth of (111)-planar nanosheets, approximately 20 to 50 nm in thickness and 10 μm in width, in the <112>−direction. The vertical growth of the facet nanowire was induced by the strong interface anisotropy between the deposit and electrolyte due to the ultra-dilute concentration of electrolyte and high reduction potential. The thickness of Ag nanosheets was controllable by the adjustment of the reduction/oxidation potential and frequency of the reverse-pulse potentiodynamic mode.

Fabrication and photoelectrochemical properties of cone-shaped CdSe nanorod arrays

Vertically aligned, cone-shaped CdSe nanorods (NRs) have been synthesized on fluorine-doped tin oxide (FTO) glass by a simple one-step, template-free electrochemical deposition at room temperature. The preparation took advantage of the wurtzite structure characteristics and current density. The experiments had been conducted with different current densities at the zero time (j) in order to investigate the morphology dependence on j. Photoelectrochemical measurements indicated that the novel CdSe photoelectrode had a potential application in photovoltaic devices. The cone-shaped nanostructure presented here could be a model system for fabricating shape-controlled NRs of other wurtzite structural materials.

Cauliflower polyaniline/multiwalled carbon nanotube electrode and its applications to hydrogen peroxide and glucose detection*

Vertically aligned polyaniline (PANI) structures were prepared by controlling the deposition current density during a stepwise template-free electrochemical deposition process of aniline on a glassy carbon electrode (GCE). Scanning electron micrographs (SEMs) showed the formation of cauliflower PANI structures, each with a diameter of approximately 2–3 and 10 μm in length. The cauliflower-like PANI electrode was modified with multiwalled carbon nanotubes (cauliflower PANI/MWCNTs) and used as the working electrode for electrochemical detections where H2O2 and glucose were used as the models for the chemical sensor and biosensor, respectively. The sensor provided linearity in the range of 1.0 to 150 μM of H2O2 with the limit of detection (LOD) of 50 nM. This is 100-fold better than the LOD of the bare GCE. Moreover, this sensor exhibited remarkable operational stability, i.e., 50 μM H2O2 could be analyzed up to 140 times with a 2.7 % relative standard deviation (RSD). A glucose biosensor was prepared using the modified cauliflower PANI/MWCNT electrode. This had a 3.4 times higher sensitivity than an electrode modified with PANI film/MWCNTs. The regular size and high surface-to-volume ratio of the cauliflower PANI electrode will provide good opportunities for further biosensor applications.

Fabrication of CdS nanotubes assisted by the template-free electrochemical synthesis method and their photo-electrochemical application

A cadmium sulfide nanotube (CdS NT) was successfully fabricated by a two-step route consisting of the template-free electrochemical deposition of cadmium hydroxide films at 298K and their subsequent sulfurization by S2− ions. Photo-electrochemical solar cells using a combination of CdS NT, polysulfide (Sx2−/xS2−) and carbon electrode exhibited high IPCE (ca. 80%) at 510nm due to efficient light-harvesting performance.

Electrochemical Growth of ZnO Nanobelt-Like Structures at 0 °C: Synthesis, Characterization, and in-Situ Glucose Oxidase Embedment

Single-crystalline ZnO nanobelt-like structures (NBS) of length, width, and thickness in the ranges of 5–10 μm, 50–400 nm, and 20–100 nm, respectively, are synthesized by a one-step, template-free electrochemical deposition technique at 0 °C. Scanning electron microscopy and transmission electron microscopy (TEM) reveal a unique morphology of the as-synthesized NBS, with an oval-shaped cross section. High-resolution TEM and selected area electron diffraction studies further confirm that individual NBS are single-crystalline, with a growth direction of [101̅0], while the X-ray diffraction data indicate its characteristic wurtzite structure. The successful formation of ZnO NBS at 0 °C using this simple, aqueous-solution-based, bottom-up approach is further exploited to fabricate a bionanocomposite. In particular, incorporation of a biomolecule, i.e., glucose oxidase (GOx) into the ZnO NBS in situ during electrodeposition is found to be highly effective in enhancing the activity and stability. The resulting GOx-embedded ZnO NBS are found to exhibit not only a higher enzymatic activity but also remarkable stability when compared to GOx surface-immobilized ZnO NBS. The present direct biomolecular embedment approach promises a new strategy for incorporating other compatible biomolecules in situ at low temperature while preserving their bioactivity.

Optical properties of ZnO nanowire arrays electrodeposited on n- and p-type Si(111): Effects of thermal annealing

► A new template-free electrochemical deposition method for the synthesis of ZnO nanorods/nanowires directly on n - and p -type silicon (Si) substrates. ► Improved structural, electrical and optical properties of the ZnO nanowires/ p -Si (1 1 1) heterojunction have been demonstrated. ► Photodetectors have been fabricated based on the n -ZnO nanowires/ p -Si heterojunction obtained by electrodeposition. Electrodeposition is a low temperature and low cost growth method of high quality nanostructured active materials for optoelectronic devices. We report the electrochemical preparation of ZnO nanorod/nanowire arrays on n -Si(1 1 1) and p -Si(1 1 1). The effects of thermal annealing and type of substrates on the optical properties of ZnO nanowires electroplated on silicon (1 1 1) substrate are reported. We fabricated ZnO nanowires/ p -Si structure that exhibits a strong UV photoluminescence emission and a negligible visible emission. This UV photoluminescence emission proves to be strongly influenced by the thermal annealing at 150–800 °C. Photo-detectors have been fabricated based on the ZnO nanowires/ p -Si heterojunction.

Template-Free Electrochemical Deposition of Interconnected ZnSb Nanoflakes for Li-Ion Battery Anodes

A single-step fabrication of ZnSb nanostructures using template-free electrochemical deposition was developed. Results have indicated that ZnSb nanoflakes, nanowires, or nanoparticles with controlled composition could be obtained by adjusting the precursor concentration, applied voltage, and substrate type. The ZnSb nanostructures deposited on Cu foils were directly used as Li-ion battery anodes without the addition of any binder. Electrochemical analyses revealed that the interconnected ZnSb nanoflakes depicted high discharge capacities and a stable performance, which were better than that of ZnSb nanowires and nanoparticles. With an initial discharge capacity of 735 mA h/g and an initial Columbic efficiency of 85%, the ZnSb nanoflakes maintained a discharge capacity of 500 mA h/g with a Coulombic efficiency of 98% after 70 cycles at a current density of 100 mA/g (0.18 C). The ZnSb nanowires and nanoparticles showed a capacity of 190 and 40 mA h/g, respectively, after 70 cycles at the same current densit...

⟨0001⟩-Preferential Growth of CdSe Nanowires on Conducting Glass: Template-Free Electrodeposition and Application in Photovoltaics

By contrast with the rich, wurztite-related, one-dimensional nanostructure of ZnO and its wide variety of applications, there only exists a few methods for the controlled and designed synthesis of one-dimensional CdSe nanostructures. Here, we describe a low-temperature and directed preparation of CdSe nanowires in a simple one-step, template-free electrochemical deposition. The preparation takes advantage of both the wurtzite structure characteristics and current-induced preferential orientation. High-resolution transmission electron microscopy (TEM) images and selected area electron diffraction (SAED) patterns clearly verify that the prepared CdSe nanowires have a single-crystal wurtzite structure and grow along the [0001] (c-axis). With the discovery of other one-dimensional CdSe nanostructures and CdS nanowires, it is anticipated that this electrochemical synthesis method can be extended to other nanostructures of CdSe and to other II−VI semiconductors and can also be developed into a systematic synthesis for nanostructured semiconductors. The average diameter of the thus prepared CdSe nanowires is larger than those synthesized by chemical vapor deposition (CVD) and solution−liquid−solid (SLS) methods. This may be an advantage in some applications, for example, as the light-harvesting material in photovoltaic cells. Organic/inorganic hybrid photovoltaic cells fabricated with CdSe nanowires and PEDOT:PSS give a good photovoltaic performance, demonstrating the attractive potential of CdSe nanowire applications in photovoltaics.

Characteristics of the nucleation and growth of template-free polyaniline nanowires and fibrils

Template-free electrochemical deposition of large arrays of uniform and oriented conducting polymer nanowires has recently been demonstrated. In this article, we build upon the key earlier findings and report new phenomena (initial formation of a 2D film) and mechanistic insight into the growth of the nanowires. High-resolution scanning electron microscopy was used to investigate the initial nucleation and growth of polyaniline nanowires and fibrils on conducting electrodes. Nanowire formation was found to occur in three stages. First, nucleation sites are deposited onto the surface of the electrode. Second, horizontal and vertical growth occurs in combination to form a compact lateral 2D layer containing small vertical polymer nodules. Lastly, growth occurs only in the vertical direction, extending the polymer nodules to form nanowires. Larger diameter polyaniline fibrils also grew in conjunction with the nanowires. In contrast to the ordered growth of the nanowires, fibrils undergo successive and multiple branching, leading to the formation of large area spaghetti-like deposits. A series of growth studies show that nanowire and fibril formation are highly sensitive to the electrode material and polymerization current. Platinum and gold exhibited uniform and oriented nanowire growth while stainless steel and indium tin oxide had poor nanowire growth and a high incidence of fibril growth. High polymerization currents favored the formation of fibrils on all electrode materials.

Growth of ZnO Nanoneedle Arrays with Strong Ultraviolet Emissions by an Electrochemical Deposition Method

We report a soft and template-free electrochemical deposition method to prepare wafer-scale high-quality ZnO nanoneedle arrays on oriented gold-film-coated silicon substrates at temperatures as low as 70 °C. SEM, XRD, and TEM data show that the ZnO nanoneedles are of single-crystal wurtzite structure and preferentially oriented along the c-axis perpendicular to the substrates. Such ZnO nanoneedle arrays exhibit strong ultraviolet emissions at room temperature but very weak defect-related visible emissions. The blue shift of the low-temperature ultraviolet emission compared with that at room temperature further confirms its excitonic origin. The nanoneedle growth mechanism can be attributed to formation of {0001}-oriented ZnO nuclei on the oriented gold-coated silicon substrate and then faster growth along the 〈0001〉 direction in terms of minimum interface and surface energy.

A template-free electrochemical deposition route to ZnO nanoneedle arrays and theiroptical and field emission properties

We report a soft and template-free electrochemical deposition method for preparing wafer-scaleZnO nanoneedle arrays on an oriented gold film coated silicon substrate. It has been shownthat the ZnO nanoneedles possess single-crystal wurtzite structure and grow along thec-axis perpendicularly on the substrate. Raman and resonant Raman scattering studies haveconfirmed that the ZnO nanoneedles are of good crystal quality. The room temperaturephotoluminescence spectrum of such ZnO nanoneedle arrays exhibits a strong ultravioletemission but negligible visible emission. The time-resolved photoluminescencespectral analysis discloses the excitonic origin of the ultraviolet emission. Thefield electron emission study, showing notable emission current in a moderateturn-on field, demonstrates potential applications of such ZnO nanoneedle arrays infield emission display devices. The formation of such a ZnO nanoneedle array isattributed to the formation of {0001}-oriented ZnO nuclei on the oriented goldcoated silicon substrate and preferential growth along .