3D Hybrid Nanostructures Research Articles

Extinction Behavior and Near-Field Enhancement of 3D Hybrid Nanostructures Consisting of Ag-Coated SiO2 Nanorods

Extinction Behavior and Near-Field Enhancement of 3D Hybrid Nanostructures Consisting of Ag-Coated SiO2 Nanorods

Facile synthesis of large-scale TiO2 nanorod arrays decorated with Ag nanoparticles as sensitive 3D SERS substrates

A facile and green synthesis strategy is employed to prepare uniform three-dimensional (3D) nanostructure as surface-enhanced Raman scattering (SERS) sensors by decorating Ag nanoparticles (AgNPs) on TiO2 nanorod arrays. The results of XPS, SEM and TEM analyses indicate that AgNPs are distributed homogeneously on the surface of TiO2 nanorods. The 3D hybrid substrate presents sensitive SERS signals of rhodamine 6 G (R6G). The relative standard deviation (RSD) for the main Raman vibration modes (611, 776, 1189 and 1651 cm−1) is less than 7%. Further UV–vis absorption spectra and FDTD simulation jointly illustrate that the interaction between AgNPs with symmetrical distribution in three dimensions generated intensive hot spots, which greatly improved the performance and spatial uniformity of SERS. The substrate also exhibits excellent SERS ability in detecting adenine molecule. The results show that the two-steps synthesis is a promising strategy for preparing 3D hybrid nanostructure substrate for SERS.

Three-Dimensional Hybrid Nanostructures of Fe3O4 Nanoparticles/Vertically-Aligned Carbon Nanotubes for High-Performance Supercapacitors

A three-dimensional (3D) hybrid nanostructure of Fe3O4 nanoparticles uniformly anchored on vertically-aligned carbon nanotubes (VACNTs) was fabricated by a facile two-step method. Assisted by supercritical carbon dioxide (SCCO2), the Fe precursor was firstly absorbed on CNT surface and then transformed into Fe3O4 nanoparticles by vacuum thermal annealing. Owing to the synergetic effects of well-distributed Fe3O4 nanoparticles (~7 nm) and highly conductive VACNTs, the hybrid electrode exhibits a high specific capacitance of 364.2 F g−1 at 0.5 A g−1 within the potential range from −0.9 to +0.1 V in Na2SO3 electrolyte and an excellent cycling stability of 84.8% capacitance retention after 2000 cycles at a current density of 4 A/g. This 3D hybrid architecture consisting of aligned CNTs and pseudocapacitive metal oxide may be a promising electrode for high-performance supercapacitors.

Self-Calibration 3D Hybrid SERS Substrate and Its Application in Quantitative Analysis

Surface-enhanced Raman spectroscopy (SERS) has been widely applied in many fields as a sensitive vibrational fingerprint technique. However, SERS faces challenges in quantitative analysis due to the heterogeneity of hot spots. An internal standard (IS) strategy has been employed for correcting the variation of hot spots. However, the method suffers from limitations due to the competitive adsorption between the IS and the target analyte. In this work, we combined the IS strategy with the 3D hybrid nanostructures to develop a bifunctional SERS substrate. The substrate had two functional units. The bottom self-assembly layer consisted of Au@IS@SiO2 nanoparticles, which provided a stable reference signal and functioned as the calibration unit. The top one consisted of appropriate-sized Au octahedrons for the detection of target analytes, which was the detection unit. Within the 3D hybrid nanostructure, the calibration unit improved the SERS performance of the detection unit, which was demonstrated by the 6-fold increase of SERS intensity when compared with the 2D substrate. Meanwhile, the reproducibility of the detection was greatly improved by correcting the hot spot changes through the calibration unit. Two biomedical molecules of cotinine and creatinine in ultrapure water and artificial urine, respectively, were sensitively determined by the 3D hybrid substrate. We expect that the developed bifunctional 3D substrate will open up new ways to advance the applications of SERS.

Three dimensional integrated architecture of Sr[sbnd]Fe LDH on hierarchical NiS framework as a flexible electrode for efficient energy storage and conversion applications

It is vital to examine the abundance of non-precious transition metal di-chalcogenides (TMDs) and layered double hydroxides (LDH) with greater storage capability and excellent electrocatalytic activity. Nowadays, the robust coupling of TMDs and LDH based materials emerged as an efficient electrocatalyst for significant electrochemical applications. The binder-free, flexible, bi-functional catalysts, 3D hybrid nanostructures of coupled TMDs/LDH on the carbon cloth (CC) electrode substrate. Initially, the hierarchical NiS nanoflowers were self-assembled on a flexible CC substrate via hydrothermal approach. Herein, the SrFe LDH nanosheets are vertically anchored on high conductive and flexible NiS/CC electrodes without destroying the original architecture by the electrodeposition method. This enriched 3D hybrid NiS@ SrFe OH/CC nanostructure provides enormous nucleation active sites with interconnected layers leading to the enhancement of electrocatalytic behaviour. The outstanding structural and morphological advantages accelerate the electrochemical activities and reaction kinetics of prepared NiS/CC, SrFe OH/CC and NiS@ SrFe OH/CC flexible electrode based supercapacitor exhibits the specific capacitance of 556, 1151 and 1553 F g−1 at 1 A g−1 current density respectively. NiS@ SrFe OH/CC//AC/CC device has a favourable energy density of 53.07 Wh kg−1 at a high power density of 4.4 kW kg−1. Additionally, these 3D flexible hybrid electrodes also favour oxygen evolution reaction at an extremely lower overpotential (ƞ) of 131 mV @ 10 mA cm−2 current density with a Tafel slope of 53 mV dec−1. The electrodeposited NiS@ SrFe OH/CC electrodes exhibit a bi-functional catalyst with better performance due to their greater surface area of 76.304 m2 g−1, pore volume of 0.113 nm, fast electron transfer-kinetic, hierarchical nanostructures and function as a promising candidate for future energy storage and conversion applications.

Metal-Organic Framework-Derived Core-Shell Nanospheres Anchored on Fe-Filled Carbon Nanotube Sponge for Strong Wideband Microwave Absorption.

Metal-organic frameworks (MOFs) are booming as a promising precursor for constructing lightweight, high-efficiency microwave absorbing (MA) material. However, it is still a challenge to rationally design three-dimensional (3D), porous MOF-derived MA materials with a stable structure and strong and wideband MA performance. Herein, a 3D hybrid nanostructure (CNT/FeCoNi@C) comprising MOF-derived magnetic nanospheres and Fe-filled carbon nanotube (CNT) sponge has been controllably fabricated to enhance the absorption ability and broaden the effective absorption bandwidth (EAB). The magnetic nanospheres are uniformly anchored on the CNT skeleton, forming hybrid network structures, which enhance interface polarization, electron transportation, and impedance matching. The minimum reflection loss (RL) and EAB of the as-prepared CNT/FeCoNi@C sponges reach -51.7 dB and 6.0 GHz, respectively, outperforming most reported MOF-based wave absorbers. This work provides not only a novel design of MOF-derived 3D nanostructures but also an effective guide for the optimization of electromagnetic properties and absorbing performance in MA material.

Low-Temperature Hydrothermal Synthesis of Novel 3D Hybrid Nanostructures on Titanium Surface with Mechano-bactericidal Performance.

Titanium is extensively employed in modern medicines as orthopedic and dental implants, but implant failures frequently occur because of bacterial infections. Herein, three types of 3D nanostructured titanium surfaces with nanowire clusters (NWC), nanowire/sheet clusters (NW/SC) and nanosheet clusters (NSC), were fabricated using the low-temperature hydrothermal synthesis under normal pressure, and assessed for the sterilization against two common human pathogens. The results show that the NWC and NSC surfaces merely display good bactericidal activity against Escherichia coli, whereas the NW/SC surface represents optimal bactericidal efficiency against both Escherichia coli (98.6 ± 1.23%) and Staphylococcus aureus (69.82 ± 2.79%). That is attributed to the hybrid geometric nanostructure of NW/SC, i.e., the pyramidal structures of ∼23 nm in tip diameter formed with tall clustered wires, and the sharper sheets of ∼8 nm in thickness in-between these nanopyramids. This nanostructure displays a unique mechano-bactericidal performance via the synergistic effect of capturing the bacteria cells and penetrating the cell membrane. This study proves that the low-temperature hydrothermal synthesized hybrid mechano-bactericidal titanium surfaces provide a promising solution for the construction of bactericidal biomedical implants.

Ultra-violet nanoimprint lithography-compatible positive-tone electron beam resist for 3D hybrid nanostructures

A fabrication technique to produce a 3D hybrid structure having different scale complex patterns is studied. A fabrication method is proposed and an ultra-violet nanoimprint lithography (UV-NIL) compatible positive-tone electron beam (EB) resist is prepared. The resist can be shown to have microstructures and nanostructures on the same surface by UV-NIL and positive-tone EB lithography (EBL). The resist can behave as a positive-tone EB resist after the UV-NIL process, exhibits a high UV-NIL and EBL resolution, and a sensitivity sufficient to fabricate 3D hybrid nanopatterns with a high aspect ratio. The fabrication of a micro lens array with nano anti-reflection structure is then performed. The resist can accurately duplicate a microscale concave lens array with a diameter of 3.8 μm. Nano anti-reflection structures are then directly fabricated by EBL on the lens array. The positive-tone dot pattern, as anti-reflection structures with diameters of 220 nm, are fabricated with an EB dose of 1000 μC/cm2. UV-NIL is used to duplicate the fabricated sample. The resist products can successfully be used as the master mold for UV-NIL. A convex micro lens array, with a 200 nm anti-reflection structure, is obtained. These methods using the resist can provide complex 3D hybrid nanostructures. The usefulness of this method and resist are discussed.

Understanding the energy storage mechanisms of poly(3,4-ethylenedioxythiophene)-coated silicon nanowires by electrochemical quartz crystal microbalance

The capacitive properties of electrodes elaborated from the electrochemical deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) coatings onto chemical vapor deposition (CVD)-grown silicon nanowires (SiNWs) were investigated for supercapacitor applications. A high areal capacitance value of 17 mF cm−2 (50 F g−1) was obtained at a scan rate of 100 mV s−1 in a 3-electrode cell configuration. Furthermore, this 3D hybrid nanostructure was analyzed by electrochemical quartz crystal microbalance (EQCM) to correlate the interfacial ionic exchange mechanisms to their electrochemical performance. It was demonstrated that both anions (BF4−) and cations (TBA+) were simultaneously involved in the charge compensation during the oxidation-reduction scans of cyclic voltammetry measurements.

One-Step Chemical Vapor Deposition Synthesis of 3D N-doped Carbon Nanotube/N-doped Graphene Hybrid Material on Nickel Foam.

3D hybrid nanostructures connecting 1D carbon nanotubes (CNTs) with 2D graphene have attracted more and more attentions due to their excellent chemical, physical and electrical properties. In this study, we firstly report a novel and facile one-step process using template-directed chemical vapor deposition (CVD) to fabricate highly nitrogen doped three-dimensional (3D) N-doped carbon nanotubes/N-doped graphene architecture (N-CNTs/N-graphene). We used nickel foam as substrate, melamine as a single source for both carbon and nitrogen, respectively. The morphology and microstructure were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, isothermal analyses, X-ray photoelectron microscopy and Raman spectra. The obtained 3D N-CNTs/N-graphene exhibits high graphitization, a regular 3D structure and excellent nitrogen doping and good mesoporosity.

An enhanced optoelectronic NO2 gas sensors based on direct growth ZnO nanowalls in situ on porous rGO

ZnO nanowalls were grown in situ on the surface of porous reduced graphene oxide (PG) films using spray, thermal reduction and facile solution method in this work. The products were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy. The results showed that the highly developed interconnected 3-D ZnO nanowall networks were anchored homogeneously on the surface of PG films to construct 3D ZnO/PG hybrid nanocomposites. This 3D hybrid nanostructure provided many channels for gas diffusion. The fabricated sensor based on ZnO/PG composites showed good photo sensing response (7.4) to 365 nm UV light and an enhanced gas sensitivity (35.31) to 50 ppm NO2 with irradiation of UV light of 1.2 mW/cm2 in the air at room temperature, which was 2.24 fold higher than that of pure ZnO, and the response-recovery times were (∼37s, and 2s) when exposed to 50 ppm NO2. The optoelectronic gas sensing mechanisms of ZnO/PG composites were proposed in detail to understand the effect of UV irradiation in the NO2 detection process.

Ultrahigh methanol electro-oxidation activity from gas phase synthesized palladium nanoparticles optimized with three-dimensional carbon nanostructured supports

Pd nanoparticles with a mean diameter of 6.7nm are prepared by gas phase cluster beam deposition. The Pd nanoparticle films exhibit excellent catalytic activity and stability for methanol oxidation. 3D hybrid nanostructures combined with multi-walled carbon nanotubes and few-layer graphene sheets are used as supports to further enhance the methanol electro-oxidation activity of the Pd nanoparticle catalysts by a factor of more than 2.7. The catalytic activity towards methanol electro-oxidation is characterized with cyclic voltammetry measurements. An ultrahigh electrochemical active surface area (ECSA) as large as 311m2g−1pd and a mass specific current corresponding to methanol oxidation levels as high as 4038mAmg−1pd are realized. These results can be attributed to the high electrochemical activity of the Pd nanoparticles and the unique conductive structure of the multi-walled carbon nanotubes/few-layer graphene sheets.

Controllably Manipulating Three-Dimensional Hybrid Nanostructures for Bulk Nanocomposites with Large Energy Products.

Hybrid nanostructures that comprise two or more nanoscale functional components are fascinating for applications in electronics, energy conversion devices, and biotechnologies. Their performances are strongly dependent on the characteristics of the individual components including the size, morphology, orientation, and distribution. However, it remains challenging to simultaneously control these structural properties in a three-dimensional (3D) hybrid nanostructure. Here, we introduce a robust strategy for concurrently manipulating these characteristics in a bulk SmCo/Fe(Co) nanocomposite. This method can tune nanocrystals in size (down to sub-10 nm), morphology (sphere, rod, or disc), and crystallographic orientation (isotropic or anisotropic). We have therefore achieved the desired nanostructures: oriented hard magnetic SmCo grains and homogeneously distributed soft magnetic Fe(Co) grains with high fractions (∼26 wt %) and small sizes (∼12.5 nm). The resulting anisotropic nanocomposite exhibits an energy product that is approximately 50% greater than that of its corresponding pure SmCo magnet and 35% higher than the reported largest value in isotropic SmCo/Fe(Co) systems. Our findings pave a new way to manipulating 3D hybrid nanostructures in a controllable manner.

Fabrication of three-dimensional hybrid nanostructure-embedded ITO and its application as a transparent electrode for high-efficiency solution processable organic photovoltaic devices.

Well-aligned, high-resolution (10 nm), three-dimensional (3D) hybrid nanostructures consisting of patterned cylinders and Au islands were fabricated on ITO substrates using an ion bombardment process and a tilted deposition process. The fabricated 3D hybrid nanostructure-embedded ITO maintained its excellent electrical and optical properties after applying a surface-structuring process. The solution processable organic photovoltaic device (SP-OPV) employing a 3D hybrid nanostructure-embedded ITO as the anode displayed a 10% enhancement in the photovoltaic performance compared to the photovoltaic device prepared using a flat ITO electrode, due to the improved charge collection (extraction and transport) efficiency as well as light absorbance by the photo-active layer.

Synthesis of three-dimensional hollow SnO2@PPy nanotube arrays via template-assisted method and chemical vapor-phase polymerization as high performance anodes for lithium-ion batteries

A novel polypyrrole (PPy) coated three-dimensional (3D) SnO2 nanotube arrays (SnO2@PPy) is synthesized via a template-assisted method followed by a chemical vapor-phase polymerization process as a high performance anode for lithium-ion batteries. In this new type electrode material, the hollow interiors of SnO2 are able to provide enough spaces for the accommodation of large volume expansion during the insertion of lithium-ion, making for the improvement of the stability of electrode. Meanwhile, the addition of conductive PPy layer could facilitate the electron transport, prevent the aggregation of active materials and warrant the stability of as-formed solid electrolyte interface (SEI) films. As a result, the integration of 3D hybrid nanostructure electrode is capable of retaining a high capacity of 646mAhg−1 after 150 cycles with a coulomb efficiency above 98% and a capacity retention of 221mAhg−1 even at a high current density of 5000mAg−1, revealing better cycling and rate properties compared with bare SnO2 nanotube arrays anode. This nanoengineering strategy can provide a facile and controllable way to synthesize other anode materials for lithium-ion batteries.

Layer-controlled growth of MoS2 on self-assembled flower-like Bi2S3 for enhanced photocatalysis under visible light irradiation

Metal sulfide semiconductors, such as molybdenum disulfide (MoS2) and bismuth trisulphide (Bi2S3), are of considerable interest for their excellent applications in photocatalysis and in many other fields. However, the controllable synthesis of MoS2/Bi2S3 hybrid nanostructures remains a challenge. In this study, we report a unique sacrificial templating strategy for preparing layer-controlled MoS2 on three-dimensional (3D) Bi2S3 micro-flowers. For this approach, Bi2S3 was utilized as a sacrificial template to regulate the ion exchange, and the dosage of molybdenum was adjusted to tune the dynamic formation, thus converting the MoS2 nanosheets on the Bi2S3 micro-flowers from monolayer to multilayer. Such a 3D flower-like hybrid nanostructure enables MoS2/Bi2S3 to exhibit adsorption-promoted photocatalysis under visible light irradiation, especially for the excellent photodegradation of low-concentration organic pollutants, for example, azo dye and atrazine. The observed superiority of the 3D MoS2/Bi2S3 was mainly attributed to the increased mass transfer, robust light-harvesting capacity, improved charge separation, lower oxygen-activation barrier and enhanced active oxygen yield. Our findings are of interest for the development of novel S-based photocatalysts and provide a new opportunity to efficiently remove low-concentration refractory pollutants. Researchers have combined inorganic ‘microflowers’ and metallic nanosheets to help remove persistent organic pollutants with sunlight. Bismuth trisulphide (Bi2S3) is a promising environmental photocatalyst because of its low toxicity and direct bandgap, but suffers from lower-than-expected chemical activity due to charge recombination. To better separate photogenerated charges, Han-Qing Yu and co-workers from the University of Science and Technology of China developed a one-pot, hydrothermal synthesis that transforms bismuth precursors into three-dimensional (3D) microstructures with petal-like shapes. The Bi2S3 microflowers then act as a template, growing multilayers of MoS2 onto the hybrid framework. The large, charge-stabilizing surface area of 3D MoS2/Bi2S3 had promising photocatalytic activity. For example, concentrations of atrazine — a common weed-killer difficult to remove from water runoff streams — were 89% lower after 4 hours of exposure to light and 3D MoS2/Bi2S3. A sacrificial strategy is developed for preparing layer-controlled MoS2 on three-dimensional Bi2S3 micro-flowers using a facile method. The nanostructured hybrid enables adsorption-promoted photocatalysis under visible light irradiation for excellent degradation of low-concentration organic pollutants, because of the increased mass transfer, robust light-harvesting capacity, improved charge separation, reduced oxygen-activation barrier and enhanced active oxygen yield.

Facile synthesis of reduced graphene oxide/hexagonal WO3 nanosheets composites with enhanced H2S sensing properties

Reduced graphene oxide/hexagonal WO3 (rGO/h-WO3) nanosheets composites were synthesized through hydrothermal method and post-calcination treatment. The products were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N2 adsorption-desorption, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA). The results showed that two-dimensional (2D) h-WO3 nanosheets with porous structure were attached on rGO to construct 3D rGO/h-WO3 hybrid nanocomposites. This 3D hybrid nanostructure provided many channels for gas diffusion. The fabricated sensor based on 3.8wt% rGO/h-WO3 composites showed good gas sensing response to H2S. The sensitivity of the sensor was about 168.58 toward 40ppm H2S, which was 3.7 times higher than that of pure WO3, and the response time was 7s when exposed to 10ppm H2S. Moreover, the sensor showed low detection limit (10ppb), wide linear range and high selectivity to H2S. The improved gas sensing properties of 3.8wt% rGO/h-WO3 composites may be attributed to the formation of hetero-junctions, good accepting/transporting electrons properties of rGO and effective gas transport channels in 3D hybrid nanostructure.

Nanoengineered three-dimensional hybrid Fe2O3@PPy nanotube arrays with enhanced electrochemical performances as lithium–ion anodes

In order to optimize the electrode system of lithium–ion batteries (LIBs) for problems like lithium-ion diffusion, electron transport, and large volume change during cycling processes, a novel three-dimensional (3D) hybrid Fe2O3 nanotube array anode coated by polypyrrole (Fe2O3@PPy) is synthesized via a sacrificial template-accelerated hydrolysis method followed by a chemical vapor-phase polymerization process. In the hollow core–shell nanostructures, the conducting PPy layer could not only facilitate the electron transport, but also force the core to expand inward into the hollow space, which allows for free volume expansion of the Fe2O3 without mechanical breaking. Besides, the static outer surface is contributed to form a stable solid electrolyte interface film. As a result, the integration of 3D hybrid nanostructure electrode is capable of retaining a high capacity of 665 mA h g−1 after 150 cycles with a coulombic efficiency of above 97 %, revealing better cycling properties compared with bare Fe2O3 nanotube arrays’ anode. This nanoengineering strategy is proven to be an ideal candidate for the development of high-performance anode for LIBs.

Rational construction of three dimensional hybrid Co3O4@NiMoO4 nanosheets array for energy storage application

Electrodes with rationally designed hybrid nanostructures can offer many opportunities for the enhanced performance in electrochemical energy storage. In this work, the uniform 2D Co3O4-based building blocks have been prepared through a facile chemical etching assistant approach and a following treatment of thermal annealing. The obtained nanosheets array has been directly employed as 2D backbone for the subsequent construction of hybrid nanostructure of Co3O4@NiMoO4 by a simple hydrothermal synthesis. As a binder-free electrode, the constructed 3D hybrid nanostructures exhibit a high specific capacitance of 1526 F g−1 at a current density of 3 mA cm−2 and a capacitance retention of 72% with the increase of current density from 3 mA cm−2 to 30 mA cm−2. Moreover, an asymmetric supercapacitor based on this hybrid Co3O4@NiMoO4 and activated carbon can deliver a maximum energy density of 37.8 Wh kg−1 at a power density of 482 W kg−1. The outstanding electrochemical behaviors presented here suggest that this hybrid nanostructured material has potential applications in energy storage.

Fabrication of 3D-Hybrid Nanostructure for Surface-Enhanced Raman Scattering Substrate: Effect of Applied Voltage on Porous Size of AAO Template

Three-dimensional (3D)-hybrid surface-enhanced Raman scattering (SERS) substrates have been achieved via simultaneous assembled silver nanoparticles (AgNPs) onto the anodic aluminum oxide (AAO) templates. The AAO templates were prepared from the UHV aluminum foil in 0.3 M oxalic acid using the two-step anodization process at 0°C. The effect of applied voltage ranging from 30 to 50 V on the porous diameter and the inter-porous distance of the AAO templates was investigated and observed with filed-emission scanning electron microscope (FE-SEM). The results showed that the porous distance and the inter-porous distance were linearly increased with the increase in the voltage potentials. To investigate the pore-size effect on the SERS activities, the AgNPs were deposited on the AAO nanoporous templates. The SERS activities of these nanostructures were demonstrated with the methylene blue (MB) as the probing molecules.