3D Hierarchical Nanostructures Research Articles

Multifunctional applications of self - Assembled 3D CeO2: Cr3+ hierarchical structures synthesized via ultrasound assisted sonochemical route

In the present work, CeO2:Cr3+ (1–11 mol %) nanophosphors (NPs) were prepared via eco-friendly ultrasound assisted sonochemical route using Cicer arietinum (C.A.) seeds extract as a surfactant. The powder X-ray diffraction results confirms the pure cubic structure with average crystallite size of ∼6–10 nm. The optical energy band gap (Eg) were found to be ∼2.95–3.45 eV. Three-dimensional (3D) hierarchical nanostructures are considered as new probe due to their high surface areas and exhibits distinctive properties which furnish excellent performance in luminescent applications. The effect of various experimental parameters on the growth mechanism of 3D morphology of the product was extensively studied. Raman studies confirm the incorporation of Cr3+ ions into the CeO2 matrix, possible electronic states during excitation, oxygen vacancies and defect sites available will change. PL studies have shown an intense sharp peak at ∼689 nm along with vibrancies side bands at ∼706 nm and 734 nm. A ∼689 nm peak was well known as R – line and was assigned to the 2Eg → 4A2g transition of Cr3+ ions. The crystal field splitting and Racah parameters were calculated to know the inter-electrons repulsion in host lattice. The CIE chromaticity co-ordinates were located in pure red region. Further, CCT values were in the range 5342 K–7781 K. The optimal CeO2:Cr3+ (9 mol %) NPs was successfully explored as a fluorescent probe for visualization of latent fingerprints (LFPs) on both porous and non-porous surfaces. Aforementioned studies indicate that the prepared sample were quite useful for multifunctional applications namely display devices and forensic applications.

Low-temperature synthesis of δ-Bi2O3 hierarchical nanostructures composed of ultrathin nanosheets for efficient photocatalysis

Due to its highest conductivity of any oxide material, the delta phase of Bi2O3 (δ-Bi2O3) is recognized as one of the most technologically important materials for various applications, including photocatalysis. Nevertheless, the δ-Bi2O3 phase is not stable at room temperature. Herein, we demonstrate that δ-Bi2O3 can be synthesized at low temperature through a facile sol-gel route in the presence of metavanadate oxyanion (VO3−). The chemical state and local structure of V are investigated by synchrotron-based techniques, such as X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Our findings demonstrate the critical role of VO3− in stabilizing the δ-Bi2O3 phase. The crystallinity of δ-Bi2O3 is dramatically increased by the addition of VO3−. In the absence of VO3−, amorphous product is obtained. The as-synthesized δ-Bi2O3 possesses 3D hierarchical nanostructures constructed by ultrathin nanosheets with a few nanometers thick (~5nm). The nanosheets are composed of ultrasmall nanoparticles in the range of 1–2nm in size. Such a unique hierarchitecture of δ-Bi2O3 allows efficient light utilization due to multiple reflections and scattering, indicated by its excellent photocatalytic activity for the degradation and mineralization of atrazine in aqueous solution.

MnO2 Nanowire/Biomass-Derived Carbon from Hemp Stem for High-Performance Supercapacitors.

Hierarchical 3D nanostructures based on waste biomass are being offered as promising materials for energy storage due to their processabilities, multifunctionalities, environmental benignities, and low cost. Here we report a facile, inexpensive, and scalable strategy for the fabrication of hierarchical porous 3D structure as electrode materials for supercapacitors based on MnO2 nanowires and hemp-derived activated carbon (HC). Vertical MnO2 wires are uniformly deposited onto the surface of HC using a one-step hydrothermal method to produce hierarchical porous structures with conductive interconnected 3D networks. HC acts as a near-ideal 3D current collector and anchors electroactive materials, and this confers a specific capacitance of 340 F g-1 at 1 A g-1 with a high rate capability (88% retention) of the 3D MnO2/HC composite because of its open-pore system, which facilitates ion and electron transports and synergistic contribution of two energy-storage materials. Moreover, asymmetric supercapacitors fabricated using 3D HC as the anode and 3D MnO2/HC as the cathode are able to store 33.3 Wh kg-1 of energy and have a power delivery of 14.8 kW kg-1.

A novel high energy hybrid Li-ion capacitor with a three-dimensional hierarchical ternary nanostructure of hydrogen-treated TiO2 nanoparticles/conductive polymer/carbon nanotubes anode and an activated carbon cathode

Lithium ion capacitors (LICs) are considered to be high-performance energy storage devices that have stimulated intense attention to bridge the gap between lithium ion battery and supercapacitor. Currently, the major challenge for LICs has been to improve the energy density without sacrificing the high rate of power output performance. Herein, we designed a three-dimensional (3D) hierarchical porous nanostructure of hydrogen-treated TiO2 nanoparticles wrapped conducting polymer polypyrrole (PPy) framework with single-walled carbon nanotubes (SWCNTs) hybrid (denoted as, H-TiO2/PPy/SWCNTs) anode material for LICs through a conventional and green approach. Such a unique network can offer continuous electron transport and reduce the diffusion length of lithium ions. A greatly lithium storage specific capacity is achieved with reversible discharge capacity ∼213 mA h g−1 (based on the mass of TiO2) over 50 cycles (@ 0.1 A g−1), which is almostly three times compared with raw TiO2 (a commercial TiO2 nanoparticles powder). In addition, coupled with commercial activated carbon (AC) cathode, the fully assembled H-TiO2/PPy/SWCNTs//AC LICs delivers a maximum energy and power densities of 31.3 Wh kg−1 and 4 kW kg−1, a reasonably good cycling stability (∼77.8% retention after 3000 cycles) within the voltage range of 1.0–3.0 V.

Botanic chemistry enabled synthesis of 3D hollow metal oxides/carbon hybrids for ultra-high performance metal-ion batteries

Many materials found in nature have unique architectures and surface chemistries that can be exploited for nanomaterial synthesis. For instance, plants and their derivatives have been used to prepare a wide variety of nanostructures with interesting morphologies. In this work, we discovered the unique ability of moss to produce 3D hierarchical, hollow metal oxide nanostructures using a general, one-pot approach. In particular, we obtained octahedral Fe2O3 with star-shaped voids as well as spherical Co3O4 with hollow profiles. Both materials displayed outstanding electrochemical performances in lithium-ion (LIBs) and sodium-ion (NIBs) batteries, highlighting the advantages of their unique 3D hierarchical nanostructures. We demonstrated for the first time that, hollow metal oxides nanoparticles, can be prepared using low cost, renewable templates that are widely abundant in nature. Our approach presents new avenues for the synthesis of nanomaterials with novel morphologies and properties.

Architecture of 3D ZnCo2O4 marigold flowers: Influence of annealing on cold emission and photocatalytic behavior

The present work demonstrates the field emission characteristics and photocatalytic behavior of ZnCo2O4 marigold flowers synthesized via a facile hydrothermal method. The effect of annealing of these 3D porous hierarchical nanostructures on field emission and photocatalytic performances is studied. When compared with the as-synthesized sample, annealed ZnCo2O4 exhibits a ∼2-fold improvement in photocatalytic activity for methylene blue (MB) degradation under visible light irradiation. The turn-on, threshold fields and high emission current densities are also strongly influenced as a result of annealing. The turn on field required to draw an emission current density of ∼1 μA/cm2 is found to be ∼2.4 and ∼1.8 V/μm for as-synthesized and annealed ZnCo2O4 marigold flowers, respectively. Field-emission measurements demonstrate remarkably large field enhancement and better stability for annealed samples. The X-ray diffraction and Raman analysis reveal that annealing improves the crystallinity and also help to remove the structural defects in ZnCo2O4. The enhancement in the field emission and photocatalytic activity of annealed ZnCo2O4 marigold flowers is attributed to the modification of electronic properties as a result of dehydration, crystallite growth and reduced surface defects/impurity phases.

Synthesis and characterization of 3D hierarchical rutile nanostructures: Effects of synthesis temperature and reagent concentrations on the texture and morphology

Rutile nanostructures with a 3D hierarchical structure organization are synthesized via the sol-gel technique using TiCl4 as a titanium precursor and HCl to regulate the acidity. The effects the synthesis conditions—molar ratios of the reagents ([Cl–]/[Ti4+] and [H2O]/[Ti4+]) and temperature—have on the mechanism of formation of the rutile phase are established. We show that the texture and morphology of the rutile nanostructrures depend on the particle packing at all levels of the hierarchical organization and are directly related to the synthesis conditions.

Pt nanoparticles functionalized 3D SnO2 nanoflowers for gas sensor application

3D SnO2 nanoflowers (NFs) assembled by rod-like nanostructures were synthesized by a facile hydrothermal method only using simple and inexpensive SnCl4·5H2O and NaOH as the starting materials, without using any surfactants or templates. The as-synthesized 3D SnO2 NFs were further functionalized by Pt nanoparticles (NPs) by a simple ammonia precipitate method, and the derived Pt NP-functionalized 3D SnO2 NFs were further investigated for gas sensor application using ethanol as a probe gas. Obtained results showed that the Pt NP-functionalized 3D SnO2 NF sensor exhibited much higher response in comparison with pure SnO2 sensor, altogether with short response/recovery times and good reproducibility. The enhanced gas sensing performances could be attributed to spill-over effect of Pt NPs for promoting gas sensing reactions, the synergic electronic interaction between Pt NPs and SnO2 support, the high surface-to-volume ratio and good electron mobility of the 1D SnO2 nanorod units, and unique 3D hierarchical flower-like nanostructures. It is also expected that the as-prepared 3D SnO2 NFs and Pt NP-functionalized product can be used in other fields such as optoelectronic devices, Li-ion battery and dye sensitized solar cells.

ZnO/Ag composite nanoflowers as substrates for surface-enhanced Raman scattering

We used a simple two-step hydrothermal method to synthesize ZnO nanoflowers (NFs) evenly decorated with silver nanoparticles (NPs) and evaluated their efficiency as organic-molecule detectors during surface-enhanced Raman scattering (SERS). These three-dimensional (3D) hierarchically structured substrates exhibited high SERS sensitivity with respect to Rhodamine 6G (R6G), with the enhancement factor being as high as 107. And the characteristic peaks of R6G could be identified even at the concentration as low as 10−12M. SERS maps collected through a point-by-point evaluation suggested that only some parts of the substrates could yield “hot spots,” which exhibited extremely high spectral intensities even at relatively low concentrations of the analyte organic molecule. Owing to the synergistic effects of the hierarchically structured semiconductor nanocrystals and the metal NPs, the degree of increase in SERS was much higher than that in the case of Ag NPs alone. This could be ascribed to the high-intensity electromagnetic fields induced at the junction spots formed between the Ag NPs, the chemical enhancement properties of the ZnO NFs, and the ability of the 3D hierarchical nanostructures to create a large number of the adsorption sites and hot spots necessary for SERS.

Synthesis of 3D hierarchical Ag/CuO nanostructures in the presence of l-histidine and their application

We report a facile synthesis of 3D hierarchical Ag/CuO nanostructures via the l-histidine-assisted biomimetic hydrothermal method. The XRD pattern of the 3D hierarchical Ag/CuO prepared in the presence of l-histidine only indicated the peaks belonging to Ag and CuO, and thus confirmed the purity of the nanocomposite. The field emission scanning electron microscopy revealed a large surface area of the 3D hierarchical CuO and Ag nanostructures which confirmed the effect of l-histidine on the morphology of the Ag/CuO. The electrochemical properties of the Ag/CuO nanostructured electrode were investigated by cyclic voltammetry, differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy. The modified glassy carbon electrode demonstrated excellent electrochemical activity towards dopamine oxidation compared to the bare GCE. From the DPV results, the estimated limit of detection (S/N = 3) and limit of quantification (S/N = 10) in the linear segment (0.001–80 μM) of dopamine are 0.077 μM and 0.257 μM, respectively. The sensitivity of this linear segment is 4.54 μA μM−1 cm−2.

Interfacial synthesis of a three-dimensional hierarchical MoS2-NS@Ag-NP nanocomposite as a SERS nanosensor for ultrasensitive thiram detection.

Interfacial self-assembly of ordered nanostructures at oil-water interfaces towards the fabrication of nanofilms has attracted the interest of plenty of scientists, since its discovery in 2004. Herein, further developments have been achieved, and we report a new strategy for the synthesis of a three-dimensional (3D) hierarchical nanostructure, through an interfacial synthesis driven microemulsion process. Thus, the synthesis route has been simplified, with the rigorous experimental conditions of traditional compositing technology. Combined with a two-step seed-mediated growth method for preparing uniform Ag-NPs, a plasmonic 3D MoS2-NS@Ag-NP nanostructure was successfully developed as a Surface-Enhanced Raman Scattering (SERS) active substrate, with plenty of surface hot spots, leading to an enhancement factor (EF) of 1.2 × 108 derived from both electromagnetic mechanism (EM) and chemical mechanism (CM) effects. The 3D MoS2-NS@Ag-NP nanostructure can be applied to detect trace thiram in apple juice and local lake water, with a detection limit as low as 10 ppb (42 nM), which is much lower than the maximal residue limit (MRL) of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency (EPA). Furthermore, quantitative analysis was achieved in the range of 10 ppb-1 ppm with good homogeneity and selectivity.

Surfactant-Free Aqueous Synthesis of Pure Single-Crystalline SnSe Nanosheet Clusters as Anode for High Energy- and Power-Density Sodium-Ion Batteries.

SnSe with 3D hierarchical nanostructure composed of interconnected single-crystal SnSe nanosheets is synthesized via a fast and effective strategy. Unexpectedly, when used as the anode material for Na-ion batteries (NIBs), the SnSe exhibits a high capacity (738 mA h g-1 ), superior rate capability (40 A g-1 ), and high energy density in a full cell. These results provide the possibility of SnSe use as NIBs anodes.

3D hierarchical flower-like nanostructure of Bi2MoO6: Mechanochemical synthesis, the effect of synthesis parameters and photocatalytic activity

In this work, we successfully prepared 3D hierarchical flower-like nanostructure of Bi2MoO6 by a facile mechanochemical reaction followed by heat treatment at 450°C for 2h. The used all chemicals were low-cost and environmentally benign compounds. Acetamide/NH4NO3 was used as driving/oxidizer agent to direct the solid phase reaction towards producing special morphology in nanoscale. Characterization results revealed that the resulting compound has been arranged from a 3D hierarchical structure with an ornamental cabbage-like shape composed of nanoparticles. The influence of milling time on the morphology growth was studied via running mechanochemical reaction in the milling time from 30 to 120min. The photocatalytic property of this product was studied for the removal of some organic dye pollutants in water under light irradiation. The results revealed a high degree of photodegradation capability, which can be related to its special structure, more active sites and high light-harvesting capacity.

Morphology-controllable synthesis and photoluminescence properties of t-LaVO4:Ln3+ nanostructures on glass substrates

Tetragonal t-LaVO4:Ln3+ (Ln3+ = Eu3+, Dy3+, Sm3+) microrod array and 3D hierarchical nanostructures with sheaf-like, flower-like, cauliflower-like, and spherical morphologies have been successfully synthesized on glass substrate through a simple hydrothermal process assisted by ethylenediaminetetraacetic acid disodium salt (Na2H2L). The morphologies of the products varied dramatically when Na2H2L/La3+ molar ratio and reaction time were changed in system. A possible crystal growth mechanism is proposed for the self-assembly of nanorods into the observed microstructures based on detailed experiments. Due to an efficient energy transfer from VO4 3− to the Ln3+ dopants, the self-assembled t-LaVO4:Ln3+ (Ln3+ = Eu3+, Dy3+, Sm3+) superstructures showed strong characteristic dominant emissions of the Eu3+, Dy3+, Sm3+ ions at 616 nm (5D0 → 7F2, strong red), 573 nm (4F9/2 → 6H13/2, yellow), 603 nm (4G5/2 → 6H7/2, orange-red) under ultraviolet excitation, respectively. This work not only gives insight into understanding the hierarchical growth behaviour of t-LaVO4:Ln3+ nanoarchitectures in a solution-phase system, but also provides a potential route to building other superstructures assembled from one-dimensional nanoparticles.

Electrocatalysis: Wafer Scale Phase‐Engineered 1T‐ and 2H‐MoSe2/Mo Core–Shell 3D‐Hierarchical Nanostructures toward Efficient Electrocatalytic Hydrogen Evolution Reaction (Adv. Mater. 44/2016)

On page 9831, Z. M. Wang, Y.-L. Chueh and co-workers present wafer scale phase-engineered 1T- and 2H- MoSe2/Mo core-shell 3D-hierarchical nanostructures, toward efficient electrocatalytic hydrogen evolution reaction with excellent Tafel slope as low as 34.7 mV dec−1, which is close to the theoretical value of 29 mV dec−1 dominated by a Volmer-Tafel reaction.

Wafer Scale Phase-Engineered 1T- and 2H-MoSe2 /Mo Core-Shell 3D-Hierarchical Nanostructures toward Efficient Electrocatalytic Hydrogen Evolution Reaction.

The necessity for new sources for greener and cleaner energy production to replace the existing ones has been increasingly growing in recent years. Of those new sources, the hydrogen evolution reaction has a large potential. In this work, for the first time, MoSe2 /Mo core-shell 3D-hierarchical nanostructures are created, which are derived from the Mo 3D-hierarchical nanostructures through a low-temperature plasma-assisted selenization process with controlled shapes grown by a glancing angle deposition system.

A novel hierarchical 3D N-Co-CNT@NG nanocomposite electrode for non-enzymatic glucose and hydrogen peroxide sensing applications

A novel 3D nanocomposite of nitrogen doped Co-CNTs over graphene sheets (3D N-Co-CNT@NG) have been successfully fabricated via a simple, scalable and one-step thermal decomposition method. This 3D hierarchical nanostructure provides an admirable conductive network for effective charge transfer and avoids the agglomeration of NG matrices, which examine direct as well as non-enzymatic responses to glucose oxidation and H2O2 reduction at a low potential. The novel electrode showed excellent electrochemical performance towards glucose oxidation, with high sensitivity of 9.05μAcm−2mM−1, a wide linear range from 0.025 to 10.83mM, and a detection limit of 100nM with a fast response time of less than 3s. Furthermore, non-enzymatic H2O2 sensors based on the 3D N-Co-CNT@NG electrode exhibited high sensitivity (28.66μAmM−1cm−2), wide linear range (2.0–7449μM), low detection limit of 2.0μM (S/N=3), excellent selectivity, decent reproducibility and long term stability. Such outstanding electrochemical performance can be endorsed to the large electroactive surface area, unique porous architecture, highly conductive networks, and synergistic interaction between N-Co-CNTs and nitrogen doped graphene (NG) in the novel 3D nanocomposite. This facile, cost-effective, sensitive, and selective glucose as well as H2O2 sensors are also proven to be appropriate for the detection of glucose as well as H2O2 in human serum.

N-doping Ta2O5 nanoflowers with strong adsorption and visible light photocatalytic activity for efficient removal of methylene blue

Abstract Novel 3D N-doping Ta2O5 nanoflowers (NFs) photocatalysts were synthesized at different annealing temperatures ranging from 700 °C to 850 °C. The microstructure, phase composition, and chemical states of those photocatalysts were characterized in details. The adsorption kinetics as well as photocatalytic performance under visible light irradiation were also investigated. Importantly, compared to N-doping Ta2O5 NFs samples obtained at other nitriding temperatures, the Ta2O5 NFs nitrided at 750 °C displayed high surface adsorption and photocatalytic degradation activity of Methylene Blue (MB) due to the synergistic effect of large surface area, strong surface adsorption, light absorption and photosensitization. The experiment results confirmed that the adsorption of MB to these samples and photocatalytic degradation follow the pseudo-second order chemisorption mechanism and pseudo first order degradation kinetics, respectively. The main reactive species were identified through the scavenging reaction following the order of h+ > OH > O2−. Additionally, degradation product analysis was conducted using liquid chromatography tandem mass spectrometry (LC–MS) technique combined with the UV–vis absorption spectrum. The results showed that the degradation was initiated by demethylation of the dye molecule. The current work may contribute to additional applications of these 3D N-doping Ta2O5 hierarchical nanostructures such as photoelectric chemical (PEC) water splitting, surface adsorption, supercapacitors, solar cells, etc.

Hot‐Electrons Mediated Efficient Visible‐Light Photocatalysis of Hierarchical Black Au–TiO2 Nanorod Arrays on Flexible Substrate

Rational engineering hierarchical 3D nanostructures with high visible‐light photocatalysis and long‐term cycling stability are of great importance in environmental purification and energy conversion. A novel and scalable approach is demonstrated to fabricate hierarchical plasmon‐resonance‐induced black Au–TiO2 nanorod arrays (NRAs) on flexible carbon cloth (CC). With the advantages of hierarchical morphology, plasmon‐enhanced visible‐light absorption, facile charge separation enabled by single‐crystalline TiO2 and conductive substrate, the black Au–TiO2 NRAs on CC show more than 13 times higher visible‐light photocatalytic efficiency enhancement compared to that of bare TiO2 NRAs. Meanwhile, the hybrid Au–TiO2–C system shows extremely high chemical and mechanical stability. The visible‐light photocatalysis does not show any decrease after consecutive seven times test. More remarkably, after being continuously stirred in aqueous solution for 60 d, almost no decrease of photocatalytic activity is observed. The UV–vis absorption measurement, optical simulations, and the control experiment on hierarchical Au–SiO2@TiO2 NRAs reveal that the enhanced visible‐light photocatalysis is caused by the plasmon‐induced hot‐electrons transfer from Au nanoparticles to neighboring TiO2 NRAs. The high visible‐light photocatalytic performance and the excellent chemical/mechanical stabilities imply that the black Au–TiO2 NRAs on CC can serve as potential photocatalytic materials for large‐scale applications in energy conversion and pollutants purification.

Enhanced gas sensing properties of hierarchical SnO2 nanoflower assembled from nanorods via a one-pot template-free hydrothermal method

Well-defined three-dimensional (3D) hierarchical tin dioxide (SnO2) nanoflowers with the size of about 200nm were successfully synthesized by a simple template-free hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption analyses were used to characterize the structure and morphology of the products. The as-synthesized full crystalline and large specific surface area SnO2 nanoflowers were assembled by one-dimensional (1D) SnO2 nanorods with sharp tips. A possible self-assembly mechanism for the formation the SnO2 nanoflowers was speculated. Moreover, gas sensing investigation showed the sensor based on SnO2 nanoflowers to exhibit high response and fast response-recovery ability to detect acetone and ethanol at an operating temperature lower than 200°C. The enhancement of gas sensing properties was attributed to their 3D hierarchical nanostructure, large specific surface area, and small size of the secondary SnO2 nanorods.