Nanorod Architecture Research Articles

Fabrication of 1D Nanometer Tungsten Trioxide under Different Solvent System

As a cheap and stable transition metal oxide, tungsten trioxide (WO3) has received extensive attentions due to superior physical and chemical properties that could be used in electronic devices, lithium-ion batteries, gas sensors, dye sensitized solar cells, catalysts. In this study, the well-designed 1D architecture of nanowires and nanorods was successfully synthesized via a simple and facile solvethermal method with no template or additives. It is found that both solvent type and concentration of W raw material can affect the size and morphology of WO3significantly in a regular way. Different products showed distinct photocatalytic activities during the processing of degradation methylene blue under visible light, and the underlying reasons for the different photocatalytic activities were discussed.

Cu(In,Ga)Se2 Films with Branched Nanorod Architectures Fabricated by Economic and Environmentally Friendly Pulse-Reverse Electrodeposition Route

Cu(In,Ga)Se2 (CIGS) materials are one of the most promising solar cell technologies owing to their large absorption coefficient and tunable direct bandgap, and they have gained considerable commercial maturity. The study herein puts forward the preparation of nanostructured CIGS films containing branched nanorod architectures, which is reported for the first time. The process employs an economic pulse-reverse electrodeposition technique by utilizing the fundamentals of electro-reduction and oxidation to fabricate nanostructured CIGS and completely avoids conventional energy-intensive high-temperature annealing/selenization step. Comprehensive characterization of nanoarchitectured films reveals the stoichiometric composition and chalcopyrite structure with dominant (112) orientation. Nanostructured CIGS exhibits excellent photoactivity with a photocurrent density of 4.31 mA/cm2 at −0.13 V vs RHE in a liquid junction, which is highest for a bare CIGS film and is attributable to its inherent high interface a...

Template-free growth of coral-like Ge nanorod bundles via UV-assisted ionic liquid electrodeposition

Germanium (Ge) is an important semiconductor material in optoelectronic devices and is being researched in energy storage fields. Ge nanostructure materials with different morphologies may lead to distinctly different application performances. In this work, Ge nanorod architectures were successfully template-free electrodeposited on ITO substrate from the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([Emim]Tf2N) containing dissolved GeCl4 with the assistance of UV light. The UV irradiation influences the conformation of imidazolium rings of [Emim]+ adsorbed during the deposition process. A solution template has been formed on the surface of the electrode which inhibited the lateral growth of Ge nuclei and promoted the growth of Ge nanorod structures. Consequently, the coral-like Ge nanorod bundles (NRBs) has been obtained. This method provides attractive prospects for the other semiconductor nanorod structures.

Sequential Nucleation Growth of ZnO Nanoflowers

The morphological characteristics of ZnO nanostructures were systematically studied from dense rods to flower-like shapes. The ZnO flower-like samples were prepared by direct decomposition of a Zn(OH)4 2– precursor and by the sequential nucleation and growth method consisted of a multistep synthesis of complex nanostructured films. Condition-dependent experiments systematically were compared as to reveal the formation and detailed growth process of ZnO nanosized crystallites and aggregates. X-ray diffraction, transmission and scanning electron microscopy indicated that the precursor, solution basicity, reaction temperature and pressure as well as reaction time, were responsible for the variations of the morphologies. ZnO flower-like and large nanorods of exceptional uniformity, orientation alignment, and optical properties have been produced in this work. Several synthesis steps are needed to produce oriented nanostructures that are more complex than simple nanorod architectures. These structures have potential applications in building functional electronics devices and optoelectronic properties.

Surface-Plasmon-Resonance-Enhanced Photoelectrochemical Water Splitting from Au-Nanoparticle-Decorated 3D TiO2 Nanorod Architectures

Surface plasmonic resonance (SPR) is a new paradigm in photoelectrochemical (PEC) research that realizes the persistent supply of green energy in a sustainable manner. However, typical approaches for decorating surfaces Au nanoparticles (NPs), such as the colloidal chemical method, nanolithography, and in situ photo/thermal reduction, involve multiple complex steps and often introduce unwanted surface/interface chemicals that jeopardize the SPR effect and charge transport. Herein, we report a largely enhanced PEC performance achieved by decorating Au NPs onto 3D titanium dioxide (TiO2) nanorod architectures grown by surface-reaction-limited pulsed chemical vapor deposition through a one-step sputtering process. The Au NP size and amount could be manipulated in a controlled manner. Compared to pristine TiO2, the Au–TiO2 electrodes achieved high photocurrent density enhancements of 42% and 267% under simulated sunlight and visible-light illumination, respectively. When amorphous aluminum oxide (Al2O3) films...

Improved performance of quantum dot-sensitized solar cells based on TiO2 nanoparticle/nanorod photoanodes

Herein, a TiO2 nanoparticle/nanorod composite architecture was suggested for improving performance of quantum dot sensitized solar cells (QDSSCs), which was fabricated on transparent conductive glass substrates (FTO) via hydrothermal method followed by spin-coating, and further used as photoanode of QDSSCs. Compared with the TiO2 nanorod photoanode, the power conversion efficiency (PCE) of the QDSSCs with this architecture was obviously improved. The champion efficiency of 4.42% was achieved, showing a 33.5% enhancement in PCE. The improved PCE mainly resulted from the increase of Jsc, which increased from 9.80 (nanorod architecture) to 15.48 mA/cm2 (nanoparticle/nanorod composite architecture). The advantages of the composite structure photoanode consist in the superior light scattering capability, faster electron transport and increased photogenerated electron concentration.

Advanced SERS Sensor Based on Capillarity-Assisted Preconcentration through Gold Nanoparticle-Decorated Porous Nanorods.

A preconcentrating surface-enhanced Raman scattering (SERS) sensor for the analysis of liquid-soaked tissue, tiny liquid droplets and thin liquid films without the necessity to collect the analyte is reported. The SERS sensor is based on a block-copolymer membrane containing a spongy-continuous pore system. The sensor's upper side is an array of porous nanorods having tips functionalized with Au nanoparticles. Capillarity in combination with directional evaporation drives the analyte solution in contact with the flat yet nanoporous underside of the SERS sensor through the continuous nanopore system toward the nanorod tips where non-volatile components of the analyte solution precipitate at the Au nanoparticles. The nanorod architecture increases the sensor surface in the detection volume and facilitates analyte preconcentration driven by directional solvent evaporation. The model analyte 5,5'-dithiobis(2-nitrobenzoic acid) can be detected in a 1 × 10-3 m solution ≈300 ms after the sensor is brought into contact with the solution. Moreover, a sensitivity of 0.1 ppm for the detection of the dissolved model analyte is achieved.

High-capacity cobalt-based coordination polymer nanorods and their redox chemistry triggered by delocalization of electron spins

The design and synthesis of nanoscale metal organic frameworks (MOFs) or coordination polymers (CPs) is of great significance in deepening their application for rechargeable batteries and supercapacitors. Here we present the designed fabrication of cobalt-nitrilotriacetic acid (CoHNta) CP nanoarchitectures via judiciously formulating reacting solvent and choosing cobalt precursor. The CoHNta with a nanorod structure (r-CoHNta) exhibits the most impressive lithium storage performance, delivering a high reversible capacity of 875mAhg−1 at 500mAg−1 after 300 cycles. Even at 2.4Ag−1, it still maintains a reversible capacity of ~460mAhg−1. The performance superiority of r-CoHNta over other nanostructures is attributed to its mesoporous nanorod architecture with rapid ion transport, good flexibility, large electrode-electrolyte contact area, and robust structure stability upon prolonged cycling. More importantly, the lithiation/delithiation behavior of r-CoHNta is investigated via synchrotron-based soft X-ray spectroscopy and electron paramagnetic resonance techniques. The findings suggest that localized high-spin Co2+ in pristine r-CoHNta would gradually convert to delocalized high-spin Co2+ upon discharging, accompanying by the rehybridization of O-2p and Co-3d orbitals.

Three-dimensional architecture of Ag/CeO2 nanorod composites prepared by dealloying and their electrocatalytic performance

The 3D Ag/CeO2 nanorod architectures were prepared by dealloying Al–Ag–Ce alloy, which exhibited enhanced catalytic activity for BH4− oxidation.

High quality interconnected core/shell ZnO nanorod architectures grown by pulsed laser deposition on ZnO-seeded Si substrates

We report the production of vertically aligned and interconnected ZnO core/shell nanorods using pulsed laser deposition (PLD) in a continuous two-step growth process. X-ray diffraction studies showed wurtzite structure and c-axis orientation with a high degree of verticality. Scanning electron microscopy showed a characteristic interconnection morphology between the nanorod tips uniformly present over the entire sample surface area, while transmission electron microscopy revealed crystalline core/amorphous shell architecture. Strong bands at 98.7 cm−1 and 437.2 cm−1 (wurtzite ZnO low and high non-polar E2 modes) were the main features of the nanorod Raman spectra, again showing the high sample quality. Low-temperature PL data exhibited strong I6 emission and structured green band showing high optical quality. Electrical studies indicated n-type material with ohmic behaviour. The results are discussed in the context of the advantages offered by interconnected architectures of core/shell ZnO nanostructures for various applications.

Tunable Ultra-high Aspect Ratio Nanorod Architectures grown on Porous Substrate via Electromigration.

The interplay between porosity and electromigration can be used to manipulate atoms resulting in mass fabrication of nanoscale structures. Electromigration usually results in the accumulation of atoms accompanied by protrusions at the anode and atomic depletion causing voids at the cathode. Here we show that in porous media the pattern of atomic deposition and depletion is altered such that atomic accumulation occurs over the whole surface and not just at the anode. The effect is explained by the interaction between atomic drift due to electric current and local temperature gradients resulting from intense Joule heating at constrictions between grains. Utilizing this effect, a porous silver substrate is used to mass produce free-standing silver nanorods with very high aspect ratios of more than 200 using current densities of the order of 108 A/m2. This simple method results in reproducible formation of shaped nanorods, with independent control over their density and length. Consequently, complex patterns of high quality single crystal nanorods can be formed in-situ with significant advantages over competing methods of nanorod formation for plasmonics, energy storage and sensing applications.

Hydrothermal synthesis of vanadium oxide nanorods and their electrochromic performance

Nanorod-like V2O5 was fabricated using a simple one-step hydrothermal method using NH4VO3 and oxalic acid as precursors. The morphology and structure of the as-prepared V2O5 nanocrystals were characterized by different techniques. Furthermore, based on the analyses of cyclic voltammetric curves and electrochromism test, the thin V2O5 nanorod film have been found to exhibit promising electrochromic performance, which can be attributed to their nanorod architecture. The as-prepared V2O5 nanocrystals are promising electrochromic candidate for potential application in smart window.

Annealing synthesis of coralline V2O5 nanorod architecture for multicolor energy-efficient electrochromic device

A coralline vanadium pentoxide nanorod architecture on an indium-doped tin oxide substrate for energy-efficient electrochromism has been prepared by a simple annealing treatment from an overfilled amorphous three-dimensionally ordered macroporous vanadia film. The coralline vanadium pentoxide nanorod architecture exhibited multicolor electrochromic performance (yellow, blue-green, and olive), high transmittance modulations (25% and 27% at the typical wavelengths of 460nm and 1000nm, respectively), and fast switching speeds (4.8s for coloration and 7.2s for bleaching at 890nm). In addition, the coralline vanadium pentoxide nanorod architecture exhibited desirable cycle stability. After 100 cycles, negligible transmittance modulation decreased in the visible spectrum, and a decrease of only approximately 5.6% was found in the near-infrared spectrum. Cyclic voltammetry measurements indicated that the majority of the current response of the redox reactions of the coralline V2O5 nanorod architecture was surface controlled, which resulted in desirable cycling stability and fast switching speeds. A indium-doped tin oxide substrate/vanadia/liquid electrolyte/poly(3,4-ethylenedioxythiophene)/indium-doped tin oxide substrate electrochromic device was assembled, and the device showed multicolor changes with acceptable transmittance modulation and good cycling stability.

From Amorphous Macroporous Film to 3D Crystalline Nanorod Architecture: A New Approach to Obtain High‐Performance V2O5 Electrochromism

The authors regret that the affiliations for Prof. X.-Y. Liu in this manuscript were written incorrectly. The correct affiliations now appear here:

From Amorphous Macroporous Film to 3D Crystalline Nanorod Architecture: A New Approach to Obtain High‐Performance V2O5 Electrochromism

A 3D crystalline V2O5 nanorod architecture on indium tin oxide substrates is prepared by simple annealing treatment of a colloidal crystal‐assisted electrodeposited amorphous three‐dimensionally ordered macroporous film at a low temperature of 350 °C. The crystalline nanorods exhibit a low length/diameter ratio with the typical width range of 80–180 nm, length range of 190–500 nm, and thickness of 30–50 nm. Colloidal sphere‐assisted heterogeneous nucleation during electrodeposition and the anisotropic bonding of the V2O5‐layered structure are two important factors for the morphological changes. Because of the large surface area, short lithium ion diffusion distance, and good electrolyte penetration, the 3D crystalline V2O5 nanorod architecture exhibits a highly reversible Li‐ion insertion/extraction process (columbic efficiency up to 96.9%) with a five‐color‐change electrochromic performance, good transmittance modulation, and acceptable response times (8.8 s for coloration and 9.3 s for bleaching), making it a promising film electrode for electrochromic devices.

Study on the photogenerated charge transfer and photoelectrocatalytic performance of Ag/ZnO nanorod arrays under the irradiation of simulated sun light

Ag/ZnO nanorod arrays with enhanced photoelectric response properties under simulated sun light were synthesized by a facile two-step process and characterized by x-ray powder diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis DRS) and the field emission scanning electron microscopy (FESEM). The photoelectrocatalytic (PEC) activities of the catalysts were evaluated by degrading efficiency of methylene blue (MB) dye under simulated sun light. The MB removal rate can reach 85% after the irradiation of simulated sunlight for 30 min. Surface photovoltage (SPV) measurements and transient photovoltage (TPV) spectra demonstrated that Ag loading improved the utilization of the visible spectral absorption of ZnO nanorod arrays, as well as their separation efficiency of photogenerated electron–hole pairs, which may be due to the capture effect of Ag nanoparticles for free electrons under the irradiation of simulated sunlight. The photoelectrochemical investigations indicated that the Ag/ZnO nanorod arrays showed enhanced photocurrent generation efficiency, and had a more effective interface charge transfer path. The fast PEC degradation of MB is ascribed to the highly ordered nanorod architecture, the large effective mass of the photogenerated holes on the surface of ZnO induced by Ag nanoparticles loading, as well as the effective transport of photogenerated charge carriers under the effect of external electric field.

Facile fabrication of 3D layer-by-layer graphene-gold nanorod hybrid architecture for hydrogen peroxide based electrochemical biosensor

Three-dimensional (3D) layer-by-layer graphene-gold nanorod (GNR) architecture has been constructed. The resulting hybrid nanomaterials’ architecture has been tested for detecting hydrogen peroxide (H2O2) through the electrocatalytic reaction on a three electrode disposable biosensor platform. Cyclic voltammetry and amperometry were used to characterize and assess the performance of the biosensor. The 3D layer-by-layer modified electrode exhibited the highest sensitivity compared to the active carbon, graphene-oxide, cysteine-graphene oxide and GNR coated electrodes. This research explored the feasibility of using the 3D hybrid graphene-GNR as a template for biosensor. The 3D hybrid structure exhibited higher sensitivity than GNRs alone. SEM showed the explanation that GNRs had self-aggregates reducing the contact surface area when coated on the active carbon electrode, while there were no such aggregates in the 3D structure, and TEM illustrated that GNRs dispersed well in the 3D structure. This research demonstrated a better way to prepare well-separated metal nanoparticles by using the 3D layer-by-layer structure. Consequently, other single and bi-metallic metal nanoparticles could be incorporated into such structure. As a practical example, 3D layer-by-layer nanomaterials modified active carbon electrode was used for detecting glucose showing very good sensitivity and minimum interference by ascorbic acid and uric acid in test solution, which indicated a good selectivity of the biosensor as well.

Controlled assembly of Au nanorods into 1D architectures by electric field assisted deposition

The assembly of Au nanorods of average size 14 × 42 nm was investigated by electric field assisted deposition. The nanorods displayed a rich assembly behavior with formation of one dimensional (1D) architectures under specific experimental conditions. The assembly process was found to be dependent on both the intensity of the applied electric field and the frequency, in contrast to what was expected for metallic particles. A theoretical model based on interpretation of nanorods as core–shell entities was proposed in order to explain the observed behavior. As a result the overall deposition process was represented by a contour plot, where the force acting on the nanorods was displayed as a function of both the electric field and frequency. In particular, an area of the contour plot was identified where the deposition process was driven by generation of localized “hot spots” of high E-field magnitude, leading to formation of well-aligned 1D nanorod architectures bridging the electrode gaps. Electrical characterization showed that 1D architectures displayed tunneling behavior across the inter-nanorod gap. The controlled organization of nanorods into 1D architectures presents opportunities for electronic, sensing and plasmonic applications.

3D Hyperbranched Hollow Carbon Nanorod Architectures for High‐Performance Lithium‐Sulfur Batteries

Lithium‐sulfur batteries have been plagued for a long time by low Coulombic efficiency, fast capacity loss, and poor high rate performance. Here, the synthesis of 3D hyperbranched hollow carbon nanorod encapsulated sulfur nanocomposites as cathode materials for lithium‐sulfur batteries is reported. The sulfur nanocomposite cathodes deliver a high specific capacity of 1378 mAh g‐1 at a 0.1C current rate and exhibit stable cycling performance. The as‐prepared sulfur nanocomposites also achieve excellent high rate capacities and cyclability, such as 990 mAh g‐1 at 1C, 861 mAh g‐1 at 5C, and 663 mAh g‐1 at 10C, extending to more than 500 cycles. The superior electrochemical performance are ascribed to the unique 3D hyperbranched hollow carbon nanorod architectures and high length/radius aspect ratio of the carbon nanorods, which can effectively prevent the dissolution of polysulfides, decrease self‐discharge, and confine the volume expansion on cycling. High capacity, excellent high‐rate performance, and long cycle life render the as‐developed sulfur/carbon nanorod nanocomposites a promising cathode material for lithium‐sulfur batteries.

Large Scale Solution Assembly of Quantum Dot–Gold Nanorod Architectures with Plasmon Enhanced Fluorescence

Tailoring the efficiency of fluorescent emission via plasmon-exciton coupling requires structure control on a nanometer length scale using a high-yield fabrication route not achievable with current lithographic techniques. These systems can be fabricated using a bottom-up approach if problems of colloidal stability and low yield can be addressed. We report progress on this pathway with the assembly of quantum dots (emitter) on gold nanorods (plasmonic units) with precisely controlled spacing, quantum dot/nanorod ratio, and long-term colloidal stability, which enables the purification and encapsulation of the assembled architecture in a protective silica shell. Overall, such controllability with nanometer precision allows one to synthesize stable, complex architectures at large volume in a rational and controllable manner. The assembled architectures demonstrate photoluminescent enhancement (5×) useful for applications ranging from biological sensing to advanced optical communication.