3D Hierarchical Nanostructures Research Articles

Sodium niobate based hierarchical 3D perovskite nanoparticle clusters.

We report a microwave assisted synthesis of NaNbO3 perovskite mesocrystals with a hierarchical morphology formed by the self-assembly of nanoparticles in particle clusters. The synthesis method combines non-aqueous sol-gel synthesis and microwave heating in a single step process that allows us to isolate crystalline single phase NaNbO3 in few minutes. A detailed investigation of the effect of the reaction temperature on the crystallinity and morphology of the product was conducted. The synthesis stabilizes the unusual orthorhombic phase Pmma, a property that can be ascribed to the crystal size (24 nm). TEM and SAED analyses show that the hierarchical polycrystalline particles behave as single crystals, a feature related to a non-classical crystallization mechanism. Moreover, the optical bandgap of this NaNbO3 phase was estimated for the first time. The results suggest the potential of this synthetic procedure for the fast production of high quality tertiary oxide nanocrystals.

Hierarchical Zn-Co-P nanoneedle arrays supported on three-dimensional framework as efficient electrocatalysts for hydrogen evolution reaction in alkaline condition

Currently, the numerous research efforts have focused on the development of efficient non-nobble-metal electrocatalysts toward electrochemical hydrogen evolution reaction (HER) for producing high-purity hydrogen, which has been recognized as a cost-effective and eco-friendly fuel to satisfy global energy demands in the future. Herein, an active HER electrocatalyst based on Zn-Co-P nanoneedle arrays growing directly on the surface of three-dimensional (3D) nickel foam (Zn-Co-P NNs/3D-NF) was successfully synthesized via the simple and low-cost methods. The combination of desired properties for electrocatalysts such as 3D hierarchical nanostructure containing large surface area and abundant electroactive sites for fast diffusion and mass transfer of reactant/electrolyte, highly physical stability for strongly catalytic durability along with the remarkable feature of 1D porous structure of Zn-Co-P NN providing richly active sites for HER resulted in a highly electrocatalytic activity. Interesting, in the introduction of Zn, the Zn-Co-P NNs/3D-NF provides rich edge sites and defects for exposing more active sides, leading to the great enhancing in active surface area, and thereby improving HER catalytic activity. The obtained Zn-Co-P NNs/3D-NF catalyst shown high electrocatalytic efficiency toward HER with the requirement of low overpotential of 138 mV and 210 mV to reach a current density of 10 and 50 mA cm−2 in alkaline media, respectively, together with rapid kinetic at a small Tafel slope of 81.9 mV dec−1. In addition to highly electrocatalytic performance, the Zn-Co-P NNs/3D-NF catalyst also shown the superior durability at −0.138 V, this allowed the production process of H2 to continually occur at least 12 h with retaining a constant current density of 10 mA cm−2. More importantly, our research offered an attractive approach to design non-noble-metal electrocatalysts in the requirement of cost-effectiveness, high catalytic activity, and strong stability for practical HER application.

3D aluminum/silver hierarchical nanostructure with large areas of dense hot spots for surface-enhanced raman scattering.

Plasmonic nanomaterials possessing large-volume, high-density hot spots with high field enhancement are highly desirable for ultrasensitive surface-enhanced Raman scattering (SERS) sensing. However, many as-prepared plasmonic nanomaterials are limited in available dense hot spots and in sample size, which greatly hinder their wide applications in SERS devices. Here, we develop a two-step physical deposition protocol and successfully fabricate 3D hierarchical nanostructures with highly dense hot spots across a large scale (6×6 cm2 ). The nanopatterned aluminum film was first prepared by thermal evaporation process, which can provide 3Dquasi-periodic cloud-like nanostructure arrays suitable for noble metal deposition; then a large number of silver nanoparticles withcontrollable shape and size were decorated onto the alumina layer surfaces by laser molecular beam epitaxy, which can realize large-area accessible dense hot spots. The optimized 3D-structured SERS substrate exhibits high-quality detection performance with excellent reproducibility (13.1 and 17.1%), whose LOD of rhodamine 6G molecules was 10-9 M. Furthermore, the as-prepared 3D aluminum/silver SERS substrate was applied in detection of melamine with the concentration down to 10-7 M and direct detection of melamine in infant formula solution with the concentration as low 10mg/L. Such method to realize large-area hierarchical nanostructures can greatly simplify the fabrication procedure for 3D SERS platforms, and should be of technological significance in mass production of SERS-based sensors.

Wafer-scale 3D cloud-like aluminum hierarchical nanostructure for NIR SERS

Plasmonic nanomaterials with a high density of accessible hot spots over a large area are highly desirable for ultrasensitive near-infrared surface-enhanced Raman scattering (NIR SERS) sensing, especially those based on low-cost and earth-abundant noncoinage metals. Here, we report a facile thermal evaporation approach to fabricate 3D hierarchical aluminum cloud-like nanostructures decorated with nanoparticles on a wafer-sized substrate, which can provide high enhancement of Raman signals using 785 nm excitation. This enhancement is attributed to its absorption peak close to the excitation wavelength and high density of hot spots constructed by adjacent large cloud-like nanostructures and/or small nanoparticles. Systematic measurements and statistical analysis show that the obtained NIR SERS substrates exhibit high enhancement factor (1.48×105), long-term stability, and excellent reproducibility with less than 7% standard deviation over a 4-inch wafer surface. The combination of significant enhancement, long-term stability, good reproducibility, and scalable production process suggest that this type of 3D hierarchical aluminum nanostructures hold promise as a robust low-cost plasmonic material for applications in the near infrared SERS operation.

Hydrothermal synthesis of 3D hierarchical flower‐like CuGaO 2 with high surface area for dye‐sensitised solar cell

CuGaO2 has been receiving much attention due to its potential as photocathode instead of NiO for p-type dye sensitised solar cells (p-DSSCs). The improvement in the photovoltaic performance of such devices also depends on the increase of the efficient dye loading by significant enhanced specific surface areas. This work reports for the first time the fabrication of the three-dimensional (3D) hierarchical flower-like CuGaO2 nanostructures in a high uniformity by a facile one-step hydrothermal synthesis. The growth mechanism and the effects of the reaction parameters (time and reducing agent) on the formation of the 3D hierarchical flower-like CuGaO2 nanostructures were investigated in detailed. It is significantly to note that the prepared 3D hierarchical flower-like CuGaO2 nanostructures exhibit the highest specific surface areas reported (60 m2/g with ethylene glycol). Due to the efficient dye loading by high specific surface areas, the performance of p-DSSCs based on delafossite CuGaO2 is enhanced. Thereby, based on the optical investigation, electrochemical impedance measurement and Mott–Schottky plots, the improved performance can be attributed to high loading of the dye molecules, the enhanced light-scattering and the reduced interface recombination.

3D Hierarchical Gallium Oxynitride Nanostructures Decorated with Ag Nanoparticles Applied as Recyclable Substrates for Ultrasensitive SERS Sensing

AbstractDeveloping plasmon‐assisted semiconductor nanocomposites as multifunctional surface‐enhanced Raman scattering (SERS) substrate for detection as well as photodegradation of toxic organic pollutants appears to be a crucial step in upgrading the SERS technique to a quantitative analytical level. However, conventional photocatalytic semiconductor scaffolds are confined in ultraviolet‐light‐active metal oxide nanostructures (TiO2, ZnO, etc.). Herein, the scope of semiconductor scaffold is expanded to visible‐light‐active oxynitrides by developing a robust and ultrasensitive recyclable SERS substrate based on 3D hierarchical gallium oxynitrides (GaON) nanosheets loading with Ag nanoparticles (Ag NPs). Significantly, the bandgap of GaON nanosheets shrinks to 2.9 eV to enable visible‐light adsorption. The as‐fabricated SERS substrate shows a high sensitivity with enhancement factor of 5.2 × 107 in R6G detection, and yields a wide detection range of 1.0 × 10−6 –1.0 × 10−12 mol L−1. Assisted with the enhanced charge transfer by generating the Schottky contact at the metal/semiconductor interface and the electron traps played by the residue oxygen, the Ag/GaON nanocomposites show attractive recyclability at visible‐light irradiation with well‐maintained SERS activity after four cycles. This work demonstrates the superiority of taking advantage of plasmon‐assisted oxynitride semiconductors as a high‐performance SERS platform and provides new opportunities for developing robust visible‐light‐driven recyclable SERS substrates.

3D Starfish-Like FeOF on Graphene Sheets: Engineered Synthesis and Lithium Storage Performance.

To address the problems associated with poor conductivity and large volume variation in practical applications as a conversion cathode, engineering of hierarchical nanostructured FeOF coupled with conductive decoration is highly desired, yet rarely reported. Herein, 3D starfish-like FeOF on reduced graphene oxide sheets (FeOF/rGO) is successfully prepared, for the first time, through a combination of solvothermal reaction, self-assembly, and thermal reduction. Integrating the structural features of the 3D hierarchical nanostructure, which favorably shorten the path for electron/ion transport and alleviate volumetric changes, with those of graphene wrapping, which can further enhance the electrical conductivity and maintain the structural stability of the electrode, the as-prepared FeOF/rGO composite exhibits a superior lithium-storage performance, including a high reversible capacity (424.5 mA h-1 g-1 at 50 mA g-1 ), excellent stability (0.016 % capacity decay per cycle during 180 cycles), and remarkable rate capability (275.8 mA h-1 g-1 at 2000 mA g-1 ).

In‐situ growing graphitic nanotubes on carbon nanofibres as a 3D hierarchical binder‐free anode for high‐performance Li‐ion battery

By facile electrospinning and subsequent melamine-derived chemical vapour deposition strategy, a three-dimensional (3D) hierarchical binder-free carbon electrode is fabricated via in-situ growing nitrogen-rich graphitic nanotubes on carbon nanofibres. This electrode shows a 3D hierarchical nanostructure with the high specific surface. Owing to the highly conductive hierarchical structure allowing for rapid transportation of electrons and the N-doped carbon creating more Li-storage sites, the as-prepared binder-free electrode exhibits high reversible capacity, good rate capability and long cycle stability in terms of Li-ion battery.

Hierarchical nanoporous Ni(Cu) alloy anchored on amorphous NiFeP as efficient bifunctional electrocatalysts for hydrogen evolution and hydrazine oxidation

Replacing kinetically sluggish oxygen evolution reaction (OER) with hydrazine oxidation (HzOR) is an effective strategy for water electrolysis to achieve sustainable hydrogen production. Here we report triple-hierarchical nanoporous Ni(Cu)@NiFeP onto nickel foam (NM) as a bifunctional electrocatalyst for HER and HzOR. The as-prepared catalyst with a 54-fold increased electrochemical active surface area (ECSA) presents remarkable HzOR activity, requiring a potential of 6 mV to achieve 10 mA cm−2 in 1 M KOH, which is comparable to commercial Pt/C. Assembling in an electrolyzer for HER and HzOR, the Ni(Cu)@NiFeP/NM cell requires a cell voltage of 0.491 V to offer 100 mA cm−2, far lower than that of overall water splitting. The superior catalytic performance is ascribed to the synergistic effect from crystalline Ni(Cu) alloy and amorphous NiFe P-derivatives, as well as structural advantages of the unique 3D hierarchical porous nanostructures. The study also presents a strategy for accurate design and construction of multiple hierarchy of nanomaterials for energy storage and conversion devices.

Gas-phase deposited plasmonic nanoparticles supported on 3D-graphene/nickel foam for highly SERS detection

In this work, we proposed a novel three-dimensional (3D) plasmonic nanostructure based on porous graphene/nickel foam (GNF) and gas-phase deposited Ag nanoparticles (NPs). Ag NPs with high density were directly deposited on the surface of 3D GNF by performing a novel cluster beam deposition approach. In comparison with traditional Ag substrate (SiO2/Ag), such hot-spots enriched 3D nanostructure showed extremely high electromagnetic field enhancement under incident light irradiation which could be used as a sensitive chemical sensor based on surface enhanced Raman scattering (SERS). The experimental results demonstrated that the proposed nanostructure showed superior SERS performance in terms of Raman signal reproducibility and sensitivity for the probe molecules. 3D full-wave simulation showed that the enhanced SERS performance in this 3D hierarchical plasmonic nanostructure was mainly obtained from the hot-spots between Ag NPs and the near-field coupling between Ag NPs and GNF scaffolds. This work can provide a novel assembled SERS substrate as a SERS-based chemical sensor in practical applications.

Composite microsphere resulting from assembly of BiOCl nanosheets and palygorskite nanorods for enhanced photocatalytic activity

3D palygorskite (PAL)/bismuth oxychloride (BiOCl) composite microspheres were easily synthesized through a facile room temperature reaction, in which BiOCl was coupled with palygorskite (PAL) to form PAL/BiOCl nanocomposites. The employment of PAL significantly exerted great effects on the morphologies and visible-light photocatalytic performance of PAL/BiOCl nanocomposites. With gradually increasing the PAL amounts, the 3D composite microspheres were assembled with BiOCl nanosheets and palygorskite nanorods. The nanocomposites exhibited enhanced photocatalytic activities for degrading rhodamine B (RhB) under visible light irradiation, owing to its 3D hierarchical microsphere nanostructure and constructed composite with well-matched band structure and tight intercontact.

Facile Synthesis of Nanostructural High‐Performance Cu–Pb Electrocatalysts for CO2 Reduction

AbstractNanostructure and crystallinity of transition metals play an important role in catalyzing carbon dioxide electroreduction (CO2ER) where Cu is a typical electrocatalyst with a wide variety of products and Pb has a high overpotential for H2 evolution and is selective toward formic acid. In this study, 3D hierarchical nanostructures of Cu–Pb catalyst are prepared by a two‐step electrodepositing–annealing–electroreduction approach (EAE). Cu nanowires (Cu NWs) of 200–400 nm diameter are built on the surface of commercial nickel foam substrates through an EAE step. Then, Pb nanoparticles with diameter of 5–10 nm are uniformly created on the surface of Cu NWs by a second EAE step. The nanostructural Cu–Pb electrodes catalyze CO2ER at a current density of −9.35 mA cm−2 (at −0.93 V vs reversible hydrogen electrode (RHE)). The H2 evolution is suppressed by 35.6% and CO and HCOOH are enhanced by 29.6% and 9.2%, respectively, as compared with Cu NWs. The protocol proposed in this study provides a simple and straightforward approach for preparing high‐performance, hierarchical nanostructures of Cu–Pb bimetal catalyst for CO2ER.

Hierarchical Flowerlike 3D nanostructure of Co3O4@MnO2/N-doped Graphene oxide (NGO) hybrid composite for a high-performance supercapacitor

The present study investigates the fabrication of hierarchical 3D nanostructures with multi-component metal oxides in the presence of highly-porous graphene and characterized for its applications in high-performance supercapacitors. A hierarchical flowers like 3D nanostructure of Co3O4 @MnO2 on nitrogen-doped graphene oxide (NGO) hybrid composite was synthesized by thermal reduction process at 650 °C in the presence of ammonia and urea. The synthesized Co3O4@MnO2/NGO hybrid composites were studied via Raman, XRD, X-ray XPS, FE-SEM, FE-SEM with EDX, FE-TEM and BET analyses. The electrochemical analysis of Co3O4@MnO2/NGO hybrid composite electrode was investigated using cyclic voltammetry, chronopotentiometry and electrochemical impedance measurements. The hybrid composite electrode showed significant specific capacitance results of up to 347 F/g at 0.5 A/g and a corresponding energy density of 34.83 Wh kg−1 with better rate performance and excellent long-term cycling stability were achieved for 10,000 cycles. The obtained electrochemical results paved a way to utilize Co3O4@MnO2/NGO composite electrode as a promising electrode material in high performance supercapacitors.

Three-Dimensional Hierarchical Reticular Nanostructure of Fulfora candelaria Wing Decorated by Ag Nanoislands as Practical SERS-Active Substrates.

Although surface-enhanced Raman scattering (SERS) technology has been widely explored nowadays in various fields, the fabrication of practical SERS-active substrates with prominent recognition ability for various analyte molecules is still defective. Natural Fulfora candelaria wing (FCW) with three-dimensional (3D) hierarchical reticular nanostructure was selected as a new bioscaffold for rough silver (Ag) nanoislands to be assembled on to prepare a practical SERS substrate (Ag/FCW substrate). By adjusting the sputtering time of metal Ag, the morphology of the substrates could be easily tuned to control the formation and distribution of “hot spots”. Three-dimensional finite-difference time-domain (3D-FDTD) simulation indicated that the excellent SERS performance under optimal morphology was ascribed to the local enhanced electric field in rough Ag surface and effective “hot spot” areas. The SERS measurement results show that the optimal Ag/FCW substrates had high SERS performance in terms of Raman signal sensitivity, reproducibility, uniformity and recognition ability for various analyte molecules. Coupled with flexibility of the biological substrates and the cost effectiveness, the sensitive SERS detection of varied analytes based on Ag/FCW substrates offered great potential for practical applications.

Flowerlike Mesoporous FeF3·0.33H2O with 3D Hierarchical Nanostructure: Size-Controlled Green-Synthesis and Application as Cathodes for Na-Ion Batteries

A flowerlike mesoporous FeF3·0.33H2O with three-dimensional (3D) hierarchical nanostructure is successfully prepared for the first time through a facile PEG-assisted solvothermal route. By rationally regulating and controlling the amount of PEG-400 in solvent, a series of nanostructured FeF3·0.33H2O materials with various morphologies and sizes is obtained. The probable formation mechanism related to the role of the PEG is explored. Furthermore, the electrochemical performances of the as-prepared samples for Na-ion battery (NIB) are investigated and discussed. The flower-like mesoporous FeF3·0.33H2O can deliver the noticeable initial discharge capacity of 283 mAh g–1 and retain 190 mAh g–1 after 100 cycles within a potential range of 1.5–4.5 V at 0.1 C. Particularly, even at a high rate of 2.0 C, the material can still exhibit a high capacity of 155 mAh g–1. The excellent electrochemical performances can be attributed to the unique 3D hierarchical porous nanostructure and the small particle size, which ca...

Preparations of Bi-doped SnO2 hierarchical flower-shaped nanostructures with highly sensitive HCHO sensing properties

In order to improve the gas sensing performance of traditional SnO2 semiconductor nanomaterials, Bi-doped SnO2 hierarchical flower-shaped nanostructures had been synthesized by a one-step hydrothermal route. Diverse techniques characterization results collectively revealed that Bi ions have been successfully doped into SnO2 lattice and samples present numerous uniform flower-shaped nanostructures composed of many layered petal-like thin nanosheets. Benefiting from such unique 3D hierarchical flower-shaped nanostructures and Bi doping, the sensors based on Bi-doped SnO2 exhibited superior gas sensing performance concluding higher response value, faster response/recovery time, good stability and excellent selectivity to HCHO at the optimum operating temperature of 170 °C. Therefore, Bi-doped SnO2 hierarchical flower-shaped nanostructures could be used as a candidate semiconductor gas sensing materials for manufacturing highly sensitive HCHO gas sensors in the future.

Three-dimensional porous Ni-CNT composite nanocones as high performance electrocatalysts for hydrogen evolution reaction

In this study, a new 3D hierarchical Ni-CNT nanostructure was fabricated using electrodeposition method in a bath containing crystal modifier, where its electrocatalytic activity and stability for hydrogen evolution reaction (HER) were investigated. The resulting Ni-CNT nanostructures were characterized by different analysis such as XRD, SEM, EDS and AFM. The electrocatalytic activity, stability and corrosion resistance of the fabricated Ni-CNT as cathode for the HER in 1.0 M potassium hydroxide (KOH) solution were investigated by LSV curves, CV and EIS techniques. The results indicated highly active surface area as well as increased electrical conductivity owing to introduction of CNT into the Ni nanocones (NNCs) improving intrinsic catalytic activity for HER. Furthermore, due to their hierarchical structure, the Ni-CNT nanostructure facilities bubble detachment, effectively reducing the dead area resulted from bubbles phenomena. These two features are beneficial for high activity and stability during HER. This electrode able to afford current densities of 10, 20 and 100 mA/cm2 at the HER overpotentials of 82 and 116 and 207 mV, respectively. High chemical stability of CNT leads to an increase in the electrocatalytic stability and corrosion resistance of Ni-CNT hierarchical nanostructure. This research introduces the novel 3D nanocomposite structure for enhancing electrocatalytic activity for HER.

Utilization of the superior properties of highly mesoporous PVP modified NiCo2O4 with accessible 3D nanostructure and flower-like morphology towards electrochemical methanol oxidation reaction

Abstract Up to this date, researchers are still facing difficulties to expand the technology of direct methanol fuel cells (DMFCs) because of the high overpotential required to oxidize the methanol and its relatively poor performance due to CO poisoning of the leading-high cost anode catalyst. In line with this, we have successfully modified the morphological structure and composition of low cost cobalt based-metal oxides, MCo2O4 (M = Zn and Ni), with the simple and noble use of polyvinyl pyrrolidone (PVP) as growth modifier and surface stabilizer during the synthesis of nanoparticles in our previous reports, which shown high electrocatalytic activity and strong stability. Due to the good performance of our PVP modified MCo2O4 towards pseudocapacitor and oxygen evolution reaction applications, we decided to extend our research study to methanol oxidation reaction. Remarkably, PVP modified NiCo2O4 electrode directly grown on nickel foam substrate via a simple hydrothermal process exhibited better performance compared with PVP modified ZnCo2O4 and NiCo2O4 without PVP. It had obtained a remarkably low onset potential of 0.285 V and high current density of 280 mA cm−2, and shown great stability and high poison tolerance during a continuous CV cycling and Chronoamperometry test, which attained high efficiency of 86.86% and 98.52%, respectively. These positive results of PVP modified NiCo2O4 electrode towards MOR might be attributed to its hierarchical 3D nanostructures with highly mesoporous surface and large surface area which may have provided numerous electroactive sites, and the exceptional corrosion stability of NiCo2O4 electrode in alkaline solution.

Toward Tailorable Zn-Ion Textile Batteries with High Energy Density and Ultrafast Capability: Building High-Performance Textile Electrode in 3D Hierarchical Branched Design.

Rechargeable Zn-ion batteries are promising candidates for wearable energy storage devices. However, their performance is severely restricted by the low conductivity and inferior mass loading. Herein, a new type of the textile based electrodes with 3D hierarchical branched design is reported. Both Ni nanoparticles and carbon nanotubes are used to build conductive coatings on the textiles. The 3D hierarchical nanostructures, consisting of the vertical-aligned nanosheets and the fluffy-like small flakes, grow on the conductive textiles to form the self-supported electrodes. It ensures fast electron/ion transport and high mass loading, and maintains the structure stability during cycling. Two textile electrodes with the NiCo hydroxide and MnO2 self-branched nanostructures are constructed. Their faster kinetics, higher capacity and better rate capability than the solitary nanosheets based counterpart demonstrate the superiority of the hierarchical architecture. Moreover, the solid-state Zn-MnO2 and Zn-NiCo batteries are fabricated based on the textile electrodes and the polymer electrolytes. The high energy density, superior power density and good long-term cycling stability confirm their excellent energy storage ability and fast charge/discharge capability. Particularly, the high safety under various conditions enable them promising candidates for wearable electronics.

Cross-linked graphene/carbon nanotube networks with polydopamine “glue” for flexible supercapacitors

Abstract Three-dimensional (3D) graphene-based composites can possess exceptional electrochemical performance owing to their unique structure and properties. Herein, a 3D cross-linked hierarchical porous polydopamine (PDA) modified reduced graphene oxide (rGO)/amino functionalized carbon nanotube (CNT-NH 2 ) composites were synthesized via hydrothermal method . The hierarchical electrode incorporates the advantages of 1D nanotube for effective charge transport, 2D graphene nanosheet for fast ion transport and 3D cross-linked hierarchical porous substrate for mechanical stability and flexibility. Attributing to these characters, the obtained rGO/CNT-NH 2/PDA (GCP) electrode presents a high capacitance (176.2 F g-1 at 0.5 A g-1 ) in aqueous 6.0 M KOH electrolyte. Symmetric supercapacitor based on GCP-50 electrodes exhibits a high energy density of 4.22 Wh kg -1 and excellent cycling stability with 98.9% capacitance retention after 10,000 cycles. Furthermore, the supercapacitors show superior flexibility and stability. The facile synthesis, promising electrochemical results and 3D hierarchical porous nanostructure of GCPs present potential for supercapacitor and other energy storage applications.