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″Nano-metamaterials″, rationally designed novel class metamaterials with multilevel microarchitectures and both characteristic sizes and whole sizes at the nanoscale, are introduced into the area of drug delivery system (DDS), and the relationship between release profile and treatment efficacy at the single-cell level is revealed for the first time. Fe 3+ -core-shell-corona nano-metamaterials (Fe 3+ -CSCs) are synthesized using a dual-kinetic control strategy. The hierarchical structure of Fe 3+ -CSCs, with a homogeneous interior core, an onion-like shell, and a hierarchically porous corona. A novel polytonic drug release profile occurred, which consists of three sequential stages: burst release, metronomic release, and sustained release. The Fe 3+ -CSCs results in overwhelming accumulation of lipid reactive oxygen species (ROS), cytoplasm ROS, and mitochondrial ROS in tumor cells and induces unregulated cell death. This cell death modality causes cell membranes to form blebs, seriously corrupting cell membranes to significantly overcome the drug-resistance issues. It is first demonstrated that nano-metamaterials of well-defined microstructures can modulate drug release profile at the single cell level, which in turn alters the downstream biochemical reactions and subsequent cell death modalities. This concept has significant implications in the drug delivery area and can serve to assist in designing potential intelligent nanostructures for novel molecular-based diagnostics and therapeutics., (© 2023 Wiley-VCH GmbH.)

Flexible tactile sensors with high sensitivity have received considerable attention for their use in wearable electronics, human-machine interfaces, and health-monitoring devices. Although various micro/nanostructured materials are introduced for high-performance tactile sensors, simultaneously obtaining high sensitivity and a wide sensing range remains challenging. Here, a resistive tactile sensor is presented based on the hierarchical topography of carbon nanotubes (CNTs) prepared by a low-cost and straightforward manufacturing process. The 3D hierarchical structure of the CNTs over large areas is formed by transferring vertically aligned CNT bundles to a prestrained elastomer substrate and subsequently densifying them through capillary forming, providing a monotonic increase in the contact area as applied pressure. The deformable and hierarchical structure of CNTs allows the sensor to exhibit a wide sensing range (0-100 kPa), high sensitivity (141.72 kPa -1 ), and low detection limit (10 Pa). Additionally, the capillary-formed CNT structure results in increased durability of the sensor over repeated pressures. Based on these advantages, meaningful applications of tactile sensors, such as object recognition gloves and multidirectional force perceptions, are successfully realized. Given the scalable fabrication method, 3D hierarchically structured CNTs provide an essential step toward next-generation wearable devices., (© 2021 Wiley-VCH GmbH.)

Micro/nano hierarchical substrates with different micropillar spacings were designed and prepared for capture of tumor cells. The cell capture efficiency of hierarchical substrates with low-density micropillar arrays was similar to that of nanostructured substrate. Increasing the density of micopillars could significantly improve the capture efficiency. The maximum capture efficiency was achieved on the hierarchical substrate with micropillar spacings of 15 μ m, but further reducing the micropillar spacings did not increase the cell capture efficiency. It was also found that hierarchical substrates with appropriate spacing of micropillars appeared more favorable for cell attachment and spreading, and thus enhancing the cell-material interaction. These results suggested that optimizing the micropillar arrays, such as the spacing between adjacent micropillars, could give full play to the synergistic effect of hierarchical hybrid micro/nanostructures in the interaction with cells. This study may provide promising guidance to design and optimize micro/nano hierarchical structures of biointerfaces for biomedical application., (© 2021 IOP Publishing Ltd.)

Hierarchically assembled nanomaterials can find a variety of applications in medicine, energy, and electronics. Here, an automatically controlled dip-pulling method is developed and optimized to generate an unprecedented ordered nano-to-micro hierarchical nanoridge-in-microridge (NiM) structure from a bacteria-specific human-safe virus, the filamentous phage with or without genetically displaying a foreign peptide. The NiM structure is pictured as a window blind with each lath (the microridge) made of parallel phage bundles (the nanoridges). It is independent of the substrate materials supporting it. Surprisingly, it can induce the bidirectional differentiation of stem cells into neurons and astrocytes within a short timeframe (only 8 d) not seen before, which is highly desired because both neurons and astrocytes are needed simultaneously in treating neurodegenerative diseases. Since phages can direct tissue regeneration, template materials formation, sense molecules, and build electrodes, the NiM structures displaying different peptides and on varying materials hold promise in many technologically important fields., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A microorganism template approach has been explored for the fabrication of various well-defined three-dimensional (3D) structures. However, most of these templates suffer from small size (few μm), difficulty to remove the template, or low surface area, which affect their potential use in different applications or makes industrial scale-up difficult. Conversely, foraminifer's microorganisms are large (up to 200 mm), consist of CaCO 3 (easy to dissolve in mild acid), and have a relatively high surface area (≈5 m 2 g -1 ). Herein, we demonstrate the formation of hierarchical structures of inorganic materials using calcareous foraminiferal shells such as Sorites, Globigerinella siphonifera, Lox-ostomina amygdaleformis, Calcarina baculatus or hispida, and Peneroplis planatus. Several techniques, such as thermal decomposition of single-source precursors of metal oxides or sulfides, reduction of metal salts directly on the surfaces, and redox reactions, were used for coating of different shell materials and several hybrid compositions, which possess nanofeatures. Finally, we examined the role of the prepared 3D structures on the reduction of 4-nitrophenol (4-NP), ethanol electrooxidation, and water purification. A remarkable performance was achieved in each application. The hierarchical structure leads to the reduction of 4-NP within several minutes, a 27 mA cm -2 current density peak was obtained for ethanol electrooxidation, and more than 95% of the organic dye contaminants were successfully removed. These results show that using foraminiferal shells offers a new way for designing complex hierarchical structures with unique properties.

Efficient capture and rapid detection of pathogenic bacteria from body fluids lead to early diagnostics of bacterial infections and significantly enhance the survival rate. We propose a universal nano/microfluidic device integrated with a 3D nanostructured detection platform for sensitive and quantifiable detection of pathogenic bacteria. Surface characterization of the nanostructured detection platform confirms a uniform distribution of hierarchical 3D nano-/microisland (NMI) structures with spatial orientation and nanorough protrusions. The hierarchical 3D NMI is the unique characteristic of the integrated device, which enables enhanced capture and quantifiable detection of bacteria via both a probe-free and immunoaffinity detection method. As a proof of principle, we demonstrate probe-free capture of pathogenic Escherichia coli (E. coli) and immunocapture of methicillin-resistant-Staphylococcus aureus (MRSA). Our device demonstrates a linear range between 50 and 10 4 CFU mL -1 , with average efficiency of 93% and 85% for probe-free detection of E. coli and immunoaffinity detection of MRSA, respectively. It is successfully demonstrated that the spatial orientation of 3D NMIs contributes in quantifiable detection of fluorescently labeled bacteria, while the nanorough protrusions contribute in probe-free capture of bacteria. The ease of fabrication, integration, and implementation can inspire future point-of-care devices based on nanomaterial interfaces for sensitive and high-throughput optical detection., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

As macroscopic three dimensional (3D) architectures show increasing significance, much effort has been devoted to the hierarchical organization of 1D nanomaterials into serviceable macroscopic 3D assemblies. How to assemble 1D nanoscale building blocks into 3D hierarchical architectures is still a challenge. Herein we report a general strategy based on the use of ice as a template for assembling 1D nanostructures with high efficiency and good controllability. Free-standing macroscopic 3D Ag nanowire (AgNW) assemblies with hierarchical binary-network architectures are then fabricated from a 1D AgNW suspension for the first time. The microstructure of this 3D AgNW network endows it with electrical conductivity and allows it to be made into stretchable and foldable conductors with high electromechanical stability. These properties should make this kind of macroscopic 3D AgNW architecture and it composites suitable for electronic applications., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hierarchical micro/nanostructures have garnered considerable attention for their capabilities in light modulation, but the flexible fabrication of designed optical functional structures at both micro and nano scales remains challenging. Here, a polarization‐modulated patterned laser ablation method complemented by flowing liquid is proposed to fabricate hierarchical microgrooves featuring tunable cross‐sections and engraved surface nanostructures with controllable periods and orientations. The liquid‐assisted ablation counters the shielding effect of ablation debris through laser‐induced microjets, ensuring accurate control of the microgroove's shape by modulating the laser pattern in the focal plane. Simultaneously, the absence of debris also permits the consistent formation of laser‐induced periodic surface structures (LIPSS) across the microgrooves. The LIPSS's period and orientation can be finely adjusted by manipulating the pulse energy and polarization within the patterned laser spot, facilitating the adaptable creation of hierarchical micro/nanostructures for optical application needs. As a demonstration, blazed gratings featuring orientation‐customized LIPSS are fabricated, which exhibit polarization‐dependent diffraction efficiency. The laser fabrication technique offers a highly versatile solution for sculpturing shape‐controllable hierarchical gratings on hard‐to‐machine materials, paving the way for the swift production of customized optical elements. [ABSTRACT FROM AUTHOR]

Boiling is an effective energy-transfer process with substantial utility in energy applications. Boiling performance is described mainly by the heat-transfer coefficient (HTC) and critical heat flux (CHF). Recent efforts for the simultaneous enhancement of HTC and CHF have been limited by an intrinsic trade-off between them-HTC enhancement requires high nucleation-site density, which can increase bubble coalescence resulting in limited CHF enhancement. In this work, this trade-off is overcome by designing three-tier hierarchical structures. The bubble coalescence is minimized to enhance the CHF by defining nucleation sites with microcavities interspersed within hemi-wicking structures. Meanwhile, the reduced nucleation-site density is compensated for by incorporating nanostructures that promote evaporation for HTC enhancement. The hierarchical structures demonstrate the simultaneous enhancement of HTC and CHF up to 389% and 138%, respectively, compared to a smooth surface. This extreme boiling performance can lead to significant energy savings in a variety of boiling applications.

The hydrothermal synthesis of nickel oxide in the presence of triethanolamine was studied. Furthermore, the relationship between the synthesis conditions, thermal behavior, crystal structure features, phase composition and microstructure of semi-products, and the target oxide nanopowders was established. The thermal behavior of the semi-products was studied using a simultaneous thermal analysis (in particular, using one that involved thermogravimetric analysis and differential scanning calorimetry, TGA/DSC). An X-ray diffraction (XRD) analysis revealed that varying the triethanolamine and nickel chloride concentration in the reaction system can govern the formation of α- and β-Ni(OH)2-based semi-products that contain Ni(HCO3)2 or Ni2(CO3)(OH)2 as additional components. The set of functional groups in the powders was determined using a Fourier-transform infrared (FTIR) spectroscopy analysis. Using microextrusion printing, a composite NiO—(CeO2)0.80(Sm2O3)0.20 anode film was fabricated. Using XRD, scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyses, it was demonstrated that the crystal structure, dispersity, and microstructure character of the obtained material correspond to the initial nanopowders. Using Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM), the local electrophysical properties of the printed composite film were examined. The value of its conductivity was evaluated using the four-probe method on a direct current in the temperature range of 300–650 °C. The activation energy for the 500–650 °C region, which is of most interest in the context of intermediate-temperature SOFCs working temperatures, has been estimated. [ABSTRACT FROM AUTHOR]

Microsupercapacitors have picked up a remarkable reputation as prospective micropower sources for compact electronics. Unfortunately, the fabricating complexity of electrode structures and preparing sophistication of electrode materials have prevented their practical deployment. Herein, a one‐step low‐temperature precipitation method is applied to straightforwardly self‐assemble porous Ni(OH)2 nanosheets on the surface of carbon nanotubes (CNTs) surface beneath electrostatic interaction. The developed core–shell 1D CNTs@Ni(OH)2 nanosheets nanostructures exhibit high electron and ion conductivity, a sign of excellent energy storage capability. In this vein, a thermally assisted 3D printing process is intelligently regulated to enable the fabrication of 3D interdigital electrodes from as‐obtained materials. The ultimate solid‐state microsupercapacitors of CNTs@Ni(OH)2 nanosheets core–shell nanostructures in this way exhibit excellent cycle stability and offer an exceptional areal capacitance of 39.6 mF cm−2, approximately a size of or two higher than that of C‐based partners. A strong foundation for high‐quality microsupercapacitors is laid by the high specific capacity of CNTs@Ni(OH)2 nanosheets core–shell nanostructures and the ability to fabricate 3D interdigital electrodes using a thermally assisted 3D printing process. [ABSTRACT FROM AUTHOR]

[Display omitted] Here, we report a facile approach to fabricate large area ordered arrays of TiO 2 hierarchical nanostructures through space-confined seeding and growth on inverted pyramid templates. The mechanisms of space-confined seeding and growth have been systematically explored and studied. The drying TiO 2 seed precursor solution prefers to accumulate on the narrow structures including the centre and edges of the inverted pyramid structures, which facilitates to reduce the free energy of the precursor solution surface and form crystal seeds. Followed by hydrothermal treatment, selective growth of TiO 2 hierarchical nanostructures on desirable locations, such as only on the centre, only on the edges, or on the entire surface of the inverted pyramid templates, can be achieved. In addition, the growth temperature, duration and solvents affect the morphology of TiO 2 hierarchical nanostructures. This work may provide a universal approach to obtain ordered arrays of metal oxide (e.g. ZnO and MnO 2 , etc.) nanostructures for applications in optics, electrics, energy, and catalysis. [ABSTRACT FROM AUTHOR]

The industrial interest in the patterning of polymeric surfaces at the micro/nanoscale to include new functionalities has considerably increased during the last years. Hierarchical organization of micro/nanometric surface textures yields enhanced functional properties such as hydrophobicity, hydrophilicity, antibacterial activity, and optical or chromatic effects to cite some. While high accuracy methods to pattern hierarchical surfaces at the nanoscale have been developed, only some of them have been applied for high volume manufacturing with limited success, mainly because they rely on the use of expensive machinery and moulds or complicated inserts. Therefore, a method using low cost recyclable tooling and process conditions applicable to high-volume manufacturing is currently missing. In this work, a scalable and low-cost method to replicate hierarchical micro/nanostructured surfaces on plastic films is presented, which can be latter used as inlays for injection moulded parts with standard processing conditions. This method is used to demonstrate the feasibility of replicating three level hierarchical micro/nano textured surfaces using recyclable bio-based polymers (of high relevancy in the current plastic pollution context) achieving replication ratios above 90%, comparing the replication results with those obtained in polypropylene. The presence of the micro/nanotextures substantially increases the contact angle of all the polymers tested, yielding values higher than 90° in all the cases. Also, various mechanical properties of the replicated parts for all the polymers injected are characterized one and thirty days after the samples were manufactured, showing fairly constant values. This highlights the validity of the replicated surfaces, regardless of the biopolymers special crystallization characteristics. [ABSTRACT FROM AUTHOR]

Featured Application: The investigated composed particles are of interest for future applications for nanoparticle-based surface-enhanced Raman scattering (SERS) analytics and as components in plasmonic sensing, such as biomolecules. The presence of the polycationic macromolecule poly(diallyldimethylammonium chloride) (poly-DADMAC) has a strong effect on the shape and size of colloidal gold nanoparticles formed by the reduction of tetrachloroauric acid with ascorbic acid in aqueous solution. It slows down nanoparticle growth and supports the formation of nonspherical, partially highly fractal and hierarchical nanoparticle shapes. Four structural levels have been recognized from the near-spherical gold nanoparticles in the lower nanometer range over compact aggregates in the midnanometer range and flower and star-like particles in the submicron range up to larger filamentous aggregates. High-contrast scanning electron microscope (SEM) images show that single gold nanoparticles and clusters of them are connected by bundles of macromolecules in large aggregates. The investigation showed that a large spectrum of different nanoparticle shapes and sizes can be accessed by tuning the poly-DADMAC concentrations and their ratio to other reactants. The nanoassemblies with a very high specific surface area might be of interest for SERS and heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

The preparation of a hierarchically assembled Ag nanostructures based on a nanocrystalline assembly was demonstrated using an Ag(I) complex of a dipeptide (AspDap). By heating under N2 gas, a spherical assembly of a nanocrystalline dipeptide‐Ag(I) complex (diameter 4–5 μm), which has a morphology similar to the assembled structure of the dipeptide, was transformed to an assembly of Ag nanostructures, where the micrometre‐order crystalline morphology was maintained. In addition, detailed scanning electron microscopy studies revealed that Ag nanoparticles (diameter ca. 10 nm) were formed on the surface of the Ag nanostructure. When the Ag(I) ions were reduced to Ag(0), this phenomenon exhibited surface dependence due to the anisotropic two‐dimensional Ag(I) arrangement in the crystals. Thermogravimetric measurements and X‐ray photoelectron spectroscopy revealed that the reduction proceeds in a stepwise manner around 200–250 °C, together with the removal of primary and secondary carboxylic groups in the dipeptide. Comparison with the heating process of the crystalline Ag(I) complex of β‐alanine indicated that stepwise reduction is key for maintaining the original micrometre‐order morphology. A silver lining: The preparation of hierarchically assembled Ag nanostructures based on a nanocrystalline assembly was demonstrated using a Ag(I) complex of a dipeptide (AspDap). Stepwise reductions of the Ag(I) centre and protection by amino residues, which both result from the dipeptide, are key for maintaining the original crystalline morphology. [ABSTRACT FROM AUTHOR]

Abstract This review focuses on the synthesis and chemical sensing characterization of metal oxide heterostructures reported since 2012. Heterostructures exhibit strong interactions between closely packed interfaces, showing superior performances compared to single structures. Surface effects appear thanks to the magnification of nanostructures' surface leading to an enhancement of surface related properties (the base of chemical sensors working mechanism). The combination of different metal oxides to form heterostructures further improves the selectivity and/or other important sensing parameters. A very large number of different morphologies and structures have been proposed, each one exhibiting peculiar sensing properties towards specific chemical compounds. Among the different preparation methodologies, a significant number has been performed by means of hydrothermal method. However, the combination of various fabrication methods seems a very efficient strategy to obtain metal oxide-based heterostructures with different morphologies and dimensions such as core-shell nanostructures, one-dimensional heterostructures, two-dimensional layered heterojunctions, and three-dimensional hierarchical heterostructures. Despite all extraordinary advances in both material science and nanotechnology and the results achieved with heterostructured chemical sensors, there are few points that still deserve further studies and investigations, such as possible diffusion across the junctions, reproducibility of the fabrication process, synergistic or catalytic effects among the materials forming the heterostructures and influence/stability of the contacts. Moreover, perfect control over their growth is mandatory for their application in commercial devices. Only a careful understanding of the growth and the interface properties could fill the existing gap between laboratory studies and real-world exploitation of these heterostructures. Graphical abstract Image 1 Highlights • Resumes the advantages of properties of metal oxide heterojunctions. • Overviews recent studies on metal oxide heterostructure-based gas sensor. • Highlight progresses and summarizes the data on gas sensing. • Critically proposes footprints of future research and application trends in this field. [ABSTRACT FROM AUTHOR]

While bottom‐up syntheses of ordered nanostructured materials at colloidal length scales have been successful at producing close‐packed materials, it is more challenging to synthesize non‐close‐packed (ncp) structures. Here, a metal oxide nanostructure with ncp hollow sphere arrays was synthesized by combining a polymeric colloidal crystal template (CCT) with a Pechini precursor. The CCT provided defined confinement through its tetrahedral (Td) and octahedral (Oh) voids where the three‐dimensionally (3D) ordered, ncp hollow sphere arrays formed as a result of a crystallization‐induced rearrangement. This nanostructure, consisting of alternating, interconnected large and small hollow spheres, is distinct from the inverse opal structures typically generated from these CCTs. The morphology of the ncp hollow sphere arrays was retained in pseudomorphic transformations involving sulfidation and reoxidation cycling despite the segregation of zinc during these steps. Airy architecture: A new concept for the fabrication of nanostructures featuring 3D ordered, non‐close‐packed hollow sphere arrays is demonstrated through controlling dynamic changes in interfacial properties between template and precursor. The polymeric colloidal crystal provides defined confinement through its tetrahedral and octahedral voids where the arrays are formed as a result of a crystallization‐induced rearrangement. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, a simple solvothermal method is developed for the synthesis of hierarchical Co‐based metal–organic framework (H‐Co‐MOF) microflowers. These microflowers are composed of nanosheets, consisting of small nanoflakes. Upon application as an electrode material in Li‐ion batteries, H‐Co‐MOF shows ultrahigh specific capacity and long cycling performance. For instance, a remarkably superior capacity of 1345 mA h g−1 can be achieved after 100 cycles at a current density of 0.1 A g−1. Even at 2 A g−1, a large capacity of 828 mA h g−1 is maintained after 700 cycles. This excellent electrochemical performance might be ascribed to the intrinsic properties and unique hierarchical structure of the Co‐based MOF. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid solar cells have attracted tremendous research attention in recent years owing to their low fabrication cost and potentially high performance. In the present study, hierarchical structures consisting of nanostructures made over micro-textured pyramidal (MPs) silicon surface are used in PEDOT:PSS/Si heterojunction solar cells to achieve a power conversion efficiency (PCE) up to 10.26%. The combined micro-nanostructuring concept provides a superior light trapping ability (compared to only micro-textured Si), mechanical stability (compared to only Si nanowire arrays concept), increased junction area and hence improved photovoltaic (PV) characteristics including short-circuit photocurrent and PCE. Silver assisted electroless wet chemical etching is used to produce nanostructures of different length over the micro-pyramidal Si. The hierarchically structured surfaces have one-fourth reflectance in broad spectral range (300–1100 nm) as compared to micro-pyramidal Si (∼13%) arising from the enhanced light trapping properties of nanostructures owing to multiple interaction of incident light and dimensions equivalent to sub-wavelength structures. Moreover, the hierarchical structures exhibit excellent omnidirectional light trapping ability at wide range of angle of incidence of light and spectral wavelength, which is essential for practical PV applications. This has been demonstrated using solar weighted reflectance corresponding to AM 1.5G solar flux and compared with that of MPs surface. Influence of nanostructuring time on reflectance and PV performance of the solar cell has been investigated. A significant enhancement in PCE up to 0.78% (absolute) and over 8.0% (relative) could be achieved as compared to MPs-Si based hybrid solar cell (control cell) for an optimized hierarchically structured Si surfaces. It is established that an optimal trade-off between reduced reflectance of such surfaces and solar cell performance parameters is essential. Longer nano-structuring despite exhibiting a better light trapping properties results in poor cell efficiency as the nano-structuring also leads to increased surface area and non-conformal coating of the polymer. Hence, increase in photocurrent is also accompanied by a simultaneous deterioration of other cell parameters such as open circuit voltage and fill factor of the device. Nevertheless, a properly designed hierarchical-structured device paves a promising way for developing low-cost and efficient PV applications in the future. [ABSTRACT FROM AUTHOR]

Abstract: The desire to increase complexity while maintaining control over every aspect of the process itself might be used as a provocative description of the developments in block copolymer self‐assembly in solution over the last decade. The community has witnessed tremendous progress, not only with regard to the design of building blocks, but also in terms of understanding assembly pathways, interfacial properties, or kinetic obstacles. In particular, the latter can be of interest (and actually turned into an advantage) if structures that are not in thermodynamic equilibrium are targeted. Within this focus review, we aim to highlight the key developments and trends that we have identified during the last five years: the development of step‐wise and dynamic processes, different means to impart further hierarchy into solution‐borne nanostructures, and a partial shift in focus towards gradient and bottlebrush block copolymers. [ABSTRACT FROM AUTHOR]

Abstract: In energy storage materials, large surface areas and oriented structures are key architecture design features for improving performance through enhanced electrolyte access and efficient electron conduction pathways. Layered hydroxides provide a tunable materials platform with opportunities for achieving such nanostructures via bottom‐up syntheses. These nanostructures, however, can degrade in the presence of the alkaline electrolytes required for their redox‐based energy storage. A layered Co(OH)2–organic hybrid material that forms a hierarchical structure consisting of micrometer‐long, 30 nm diameter tubes with concentric curved layers of Co(OH)2 and 1‐pyrenebutyric acid is reported. The nanotubular structure offers high surface area as well as macroscopic orientation perpendicular to the substrate for efficient electron transfer. Using a comparison with flat films of the same composition, it is demonstrated that the superior performance of the nanotubular films is the result of a large accessible surface area for redox activity. It is found that the organic molecules used to template nanotubular growth also impart stability to the hybrid when present in the alkaline environments necessary for redox function. [ABSTRACT FROM AUTHOR]

In this study, a single-step combustion process for the synthesis 1-D, 2-D, and 3-D micro and nanostructures of AlN was developed. The structures were grown by combustion of Al+ k AlF 3 (or ZnF 2 )+ m NH 4 Cl reaction mixture under 4.0 MPa nitrogen atmosphere. Based on experimental data, the growth conditions, morphology, and composition, optical, and thermal properties of AlN micro and nanostructures were determined. The formation of structures was associated with the combustion temperature, liquid and gas-phase reactions, and the type of additives used in the experiments. The new insight, we gleaned from this study may help in the selective growth of AlN micro and nanostructures of different morphology, enhancing their functionality. [ABSTRACT FROM AUTHOR]

The design and assembly of innovative heterostructures comprising of multifunctional properties are technically important for the applications in efficient energy devices. Here, a novel method is reported to construct hierarchical nanostructures as functional materials for the fabrication of high-performance energy devices. Optimized conditions and extensive spectroscopic studies are performed to understand the morphology evolution. Tunable structure, richer redox active sites, enhanced mass storage, and fast electron transfer cumulatively ensure the tremendous energy storage competence. Resultant active nanomaterials of nickel cobaltite-graphene coupled with nanoporous graphene-single wall carbon nanohorns composites exhibit extraordinary energy density of 70.5 Wh kg−1. Meanwhile, this nickel cobaltite-graphene is also recognized as a prominent water oxidation catalyst, which requires low overpotential of 220 mV to afford 20 mA cm−2 current density. High performance with availability, low cost, and subtle structural distinction acknowledge that the present approach is a promising direction in pursuit of replacing precious metals in energy storage and conversion technologies. [ABSTRACT FROM AUTHOR]

Several commercial surface treatments are used to increase the adhesion between aramid fibers and the matrix material in composite structures but each of these has some limitations. The aim of this study is to address some of these limitations by developing a surface treatment method for aramid fibers that would not affect mechanical properties of the fibers negatively, could be used with any matrix material and that could withstand handling of the fibers and ageing. The method used is microwave assisted surface treatment that uses microwave radiation together with dry reactive chemicals to create hierarchical structures to the fiber surface and so makes it possible to control the adhesion properties of the fibers. SEM and AFM imaging, fiber tensile tests and modified bundle pull-out test were used to investigate the outcome of the surface treatment and measure adhesion between aramid fiber bundles and rubber. SEM and AFM imaging revealed that nanoscale deposits are formed on to the fiber surface which enable mechanical interlocking between the fiber and the matrix material. Fiber tensile tests showed that the surface treatment does not influence the tensile properties of the fiber negatively. Results from the bundle pull-out tests confirmed that this kind of method can lead up to 259% improvement in adhesion when compared to untreated aramid fibers in the rubber matrix. [ABSTRACT FROM AUTHOR]

Monodispersed hierarchically nanostructured yttrium-based materials including Y(OH)3, Y6O5F8, and H-NaYF4 were successfully synthesized from the same mesocrystal Y(OH) xF3- x precursor. It was found that there was a close crystallographic relationship between the precursor and the final products and all of the processes underwent an in situ topotactic transformation. [ABSTRACT FROM AUTHOR]

In this report, hierarchical cobalt hydroxide [Co(OH)2] hollow spheres composed of nanosheets were synthesized by fast etching of polycrystalline cuprous oxide and were then ap- plied for the nonenzymatic electrochemical detection of glucose. The fabricated hierarchical Co(OH)2 nanosheet hollow spheres were characterized by X-ray photoelectron spectro scopy, X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The electrochemical performance of the hierarchical Co(OH)2 nanosheet hollow spheres modified electrode to detect glucose was investigated by cyclic voltam metry. These sensors exhibited excellent electrocatalytic activity toward glucose, with a response time of less than 5 s. The calibration plot is linear over the wide concentration range of 1 µM to 0.13 mM, with a high sensitivity of 925.21 µA mM-1 cm-2, a correlation coefficient of 0.9942, and a detection limit of 0.93 µM (signal to noise: 3). The results demonstrate that hierarchical Co(OH)2 nanosheet hollow spheres play a vital role in the development of electrochemical sensors for nonenzymatic glucose detection. [ABSTRACT FROM AUTHOR]

This work describes a versatile hydrothermal approach to synthesize different types of hierarchical structures composed of single crystalline β-Ni(OH) 2 nanosheets. We use the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride (BmimCl) as a structure directing agent, which allows the formation of films consisting of β-Ni(OH) 2 nanosheets on the nickel foam substrate. It is found that the IL not only controls the formation of the sheet-like structure, but also promotes the growth of the nanosheets on the substrate, building an intimate contact between the active hydroxide film and the conducting metal foam. This IL agent is so effective that such a hierarchical film can also be obtained with different thickness and organization if different nickel salt precursor is used. When these film samples were applied as the electrode materials for pseudocapacitor, they exhibited promising capacitive properties with a high capacitance of about 700 F g −1 even at a high charge-discharge current rate of 5 A g −1 for prolonged cycling. [ABSTRACT FROM AUTHOR]

We developed a method to control the structure of CdTe nanowires by adopting Bi-mixed CdTe powder source to a catalyst-assisted chemical vapor deposition, which allowed us to fabricate CdTe/CdS hierarchical nanostructures. We demonstrated that diverse nanostructures can be grown depending on the combination of the Bi powder and film catalysts. As a proof of concepts, we grew CdTe/CdS branched nanowires for the fabrication of photodetectors. The hierarchical nanostructure-based photodetectors showed an improved photoresponsivity compared to the single CdTe nanowire (NW)-based photodetector. Our strategy can be a simple but powerful method for the development of advanced optoelectronic devices and other practical applications. [ABSTRACT FROM AUTHOR]

Directional driving of a droplet can be achieved on a gradient-exhibiting, nanostructured microhump (GNMH) surface at low temperature and high humidity. The GNMH surface is fabricated using a commercial carbon fiber plate with an array of microscale hump structures; nanotechniques are used to form varying nanostructures on the microhump array, producing the micro- and nanostructured surface. The different nanostructures result in a wettability gradient along the surface, enabling droplet transport with the help of vibration-even at low temperature or high humidity. In contrast, simply nanostructured surfaces or microstructured surfaces that also have a wettable gradient do not enable droplet transport at low temperature or high humidty. In a range of subzero temperatures or in a range of high-humidity conditions, the GNMH surface retains its superhydrophobicity and ability for directional droplet transport along its wettability gradient. These results may assist in the design of surfaces required for cold environments, such as microreactors, chemical analytic devices, and sensors. [ABSTRACT FROM AUTHOR]

Porous oxide ceramics are of special significance in various applications. Calcination of layered double hydroxides (LDHs) often produces very reactive mixed oxides with porous structures. In this work, we describe a biotemplate-assisted approach to fabricate hierarchically porous alumina-based ceramic composites. The porous architectures are designed by controllable growth of LDHs nanosheets on the inner and outer surfaces of morph-Al 2 O 3 in a closed hydrothermal system followed by calcination. The as-prepared alumina-based ceramics and corresponding design strategies developed herein are expected to be applicable to the synthesis of other porous oxide ceramics by utilizing biological structures. [ABSTRACT FROM AUTHOR]

Nanosheet-based ZnO hierarchical microflowers were synthesized using a facile one-pot hydrothermal approach. Analytical methods such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and high-resolution transmission electron microscopy were employed to characterize these products, and photocatalytic properties of ZnO hierarchical microflowers were also investigated. Nanosheet-based ZnO hierarchical microflowers exhibited enhanced photocatalytic properties as compared with irregular ZnO nanosheets and nanorods. Investigations confirmed that hierarchical structures had a pronounced influence upon the photocatalytic properties of ZnO. [ABSTRACT FROM PUBLISHER]

Bismuth telluride based thermoelectric materials have been commercialized for a wide range of applications in power generation and refrigeration. However, the poor machinability and susceptibility to brittle fracturing of commercial ingots often impose significant limitations on the manufacturing process and durability of thermoelectric devices. In this study, melt spinning combined with a plasma-activated sintering (MS-PAS) method is employed for commercial p-type zone-melted (ZM) ingots of Bi0.5Sb1.5Te3. This fast synthesis approach achieves hierarchical structures and in-situ nanoscale precipitates, resulting in the simultaneous improvement of the thermoelectric performance and the mechanical properties. Benefitting from a strong suppression of the lattice thermal conductivity, a peak ZT of 1.22 is achieved at 340 K in MS-PAS synthesized structures, representing about a 40% enhancement over that of ZM ingots. Moreover, MS-PAS specimens with hierarchical structures exhibit superior machinability and mechanical properties with an almost 30% enhancement in their fracture toughness, combined with an eightfold and a factor of six increase in the compressive and flexural strength, respectively. Accompanied by an excellent thermal stability up to 200 °C for the MS-PAS synthesized samples, the MS-PAS technique demonstrates great potential for mass production and large-scale applications of Bi2Te3 related thermoelectrics. [ABSTRACT FROM AUTHOR]

Zn 2 SnO 4 three-dimensional (3D) flowerlike hierarchical nanostructures have been successfully synthesized via a simple one-step hydrothermal method. Field emission scanning electron microscopic (SEM) and transmission electron microscopic (TEM) results reveal that the Zn 2 SnO 4 flowerlike structures are assembled with nanorods. To demonstrate the potential applications, gas sensor is fabricated based on the as-synthesized hierarchical Zn 2 SnO 4 . Gas sensing test results show that the hierarchical Zn 2 SnO 4 sensor exhibits significantly better sensing properties compared with the compact Zn 2 SnO 4 structures. The enhancement of sensing performance is attributed to the unique 3D hierarchical nanostructures, the increased contact surface area between Zn 2 SnO 4 and target gases, and greater number of surface active sites on the surface of as-prepared gas-sensing material. The as-prepared Zn 2 SnO 4 are significant for further exploitation of the potential applications in the future. [ABSTRACT FROM AUTHOR]

Although control over the domain orientation and long-range order of block copolymer nanostructures self-assembled in thin films has been achieved using various directed self-assembly techniques, more challenging but equally important for many lithographic applications is the ability to precisely control the shape of the interface between domains. Here, a novel layer-by-layer approach is reported for controlling the interface profile of block copolymer nanostructures and the application of an undercut sidewall profile for an enhanced metal lift-off process for pattern transfer is demonstrated. Bilayer films of lamellar-forming poly(styrene- block-methyl methacrylate) are assembled and thermally cross-linked on wafer substrates in a layer-by-layer process. The top layer, while being directed to self-assemble on the lamellae of the underlying layer, has a tunable composition and polystyrene domain width independent of that of the bottom layer. Undercut or negative sidewall profiles in the PS nanostructures are proven to provide better templates for the lift-off of Au nanowires by achieving complete and defect-free pattern transfer more than three times faster than comparable systems with vertical sidewall profiles. More broadly, the layer-by-layer approach presented here provides a pathway to achieving sophisticated interface profiles and user-defined 3D block copolymer nanostructures in thin films. [ABSTRACT FROM AUTHOR]

ZnO hierarchical structure has been synthesis by using chemical routs method. Hydra zinc nitrate, oleic acid, ethanol was used as row materials for the chemical reaction in the presence of NaOH. The Reaction took place at room temperature under stirrer. The prepared ZnO powder is collected and mixed with PVA to make a proper paste, then the paste was screen-printed in 1cm square pattern to make thick films. Afterwards, the films are annealed at 500 C˚ for an hour. The morphology, crystallinity and structural properties are studied by X-ray diffraction, the experimental pattern of the films show very fine peaks indicate a good crystallization, also the morphology of the films studied by atomic force microscope and field emission scanning electron microscope. The sensitivity of zinc oxide NRs films to 100ppm vapor methanol, ethanol and NH3 gas as a function of working temperature. As evident, the sensitivity increases with the temperature and reaches a maximum value in correspondence of T = 200-300°C. If the temperature increases again, the sensitivity decreases. [ABSTRACT FROM AUTHOR]

As macroscopic three dimensional (3D) architectures show increasing significance, much effort has been devoted to the hierarchical organization of 1D nanomaterials into serviceable macroscopic 3D assemblies. How to assemble 1D nanoscale building blocks into 3D hierarchical architectures is still a challenge. Herein we report a general strategy based on the use of ice as a template for assembling 1D nanostructures with high efficiency and good controllability. Free-standing macroscopic 3D Ag nanowire (AgNW) assemblies with hierarchical binary-network architectures are then fabricated from a 1D AgNW suspension for the first time. The microstructure of this 3D AgNW network endows it with electrical conductivity and allows it to be made into stretchable and foldable conductors with high electromechanical stability. These properties should make this kind of macroscopic 3D AgNW architecture and it composites suitable for electronic applications. [ABSTRACT FROM AUTHOR]

A form of photoelectrode architecture suitable for inorganic semiconductor solar cells is reported. The developed architecture consists of hierarchically organized TiO2 nanostructures with several tens of nanometer-sized particles that have a large surface area and open channels with several hundred-nanometer-gaps perpendicular to the substrate. These are tailored by controlling the kinetic energy of the ablated species during pulsed laser deposition (PLD). To fabricate the solar cells, CdS and CdSe inorganic sensitizers are assembled onto the architecture by successive ionic layer adsorption and reaction and polysulfide solution is used as an electrolyte with lead sulfide counter-electrodes. The inorganic semiconductor solar cells using the developed architecture (PLD-TiO2) show high energy conversion efficiencies of 5.57% compared to a conventional mesoporous TiO2 film(NP-TiO2) (3.84%) with an optical mask at 1 sun of illumination. The improved cell performance of PLD-TiO2 is attributed to greater light-harvesting ability, which results in the enhancement of the Jsc value. PLD-TiO2 absorbs more CdS/CdSe because of its larger surface area and excellent adhesion properties with fluorine-doped tin oxide (FTO) substrates. Additionally, due to its unique channel-shaped architecture, PLD-TiO2 has a longer electron lifetime compared to NP-TiO2. [ABSTRACT FROM AUTHOR]

Hollow and hierarchical nanostructures have received wide attention in new-generation, high-performance, lithium ion battery (LIB) applications. Both TiO2 and Fe2O3 are under current investigation because of their high structural stability (TiO2) and high capacity (Fe2O3), and their low cost. Here, we demonstrate a simple strategy for the fabrication of hierarchical hollow TiO2@Fe2O3 nanostructures for the application as LIB anodes. Using atomic layer deposition (ALD) and sacrificial template-assisted hydrolysis, the resulting nanostructure combines a large surface area with a hollow interior and robust structure. As a result, such rationally designed LIB anodes exhibit a high reversible capacity (initial value 840 mAh g−1), improved cycle stability (530 mAh g−1 after 200 cycles at the current density of 200 mA g−1), as well as outstanding rate capability. This ALD-assisted fabrication strategy can be extended to other hierarchical hollow metal oxide nanostructures for favorable applications in electrochemical and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Of minerals and microbes: A microbial‐mineralization‐inspired approach was used to facilitate the syntheses of iron oxides with a high specific surface area, such as 253 m2 g−1 for maghemite (γ‐Fe2O3) and 148 m2 g−1 for hematite (α‐Fe2O3). These iron oxides can be applied to electrode material of lithium‐ion batteries, adsorbents, and catalysts. [ABSTRACT FROM AUTHOR]

A general method for facile kinetics-controlled growth of aligned arrays of mesocrystalline SnO nanorods on arbitrary substrates has been developed by adjusting supersaturation in a unique ternary solvent system comprising acetic acid, ethanol, and water. The hydrolysis processes of Sn(IV) as well as the nucleation and growth of SnO crystals were carefully controlled in the mixed solvents, leading to an exclusively heterogeneous nucleation on a substrate and the subsequent growth into mesocrystalline nanorod arrays. In particular, aligned arrays of hierarchically structured, [001]-oriented mesocrystalline SnO nanorods with four {110} lateral facets can be readily grown on Ti foil, as well as many other inert substrates such as fluoride-doped tin oxide (FTO), Si, graphite, and polytetrafluoroethylene (Teflon). Due to the unique combination of the mesocrystalline structure and the one-dimensional nanoarray structure, the obtained mesocrystalline SnO nanorod arrays grown on metallic Ti substrate exhibited an excellent rate performance with a high initial Coulombic efficiency of 65.6% and a reversible capacity of 720 mA·h/g at a charge/discharge rate of 10 C (namely, 7,820 mA/g) when used as an anode material for lithium-ion batteries. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report a facile non-hydrothermal method for the large-scale production of hierarchical TiO2 nanorod spheres for the photocatalytic elimination of contaminants and killing bacteria. Crescent Ti/RF spheres were prepared by deliberately adding titanium trichloride (TiCl3) to the reaction of resorcinol (R) and formaldehyde (F) in an open reactor under heating and stirring. The hierarchical TiO2 nanorod spheres were obtained by calcining the crescent Ti/RF spheres in a furnace in air to burn off the RF spheres. This method has many merits, such as large-scale production, good crystallisation of TiO2, and good reproducibility, all of which are difficult to realise by conventional hydrothermal methods. The calcination temperature plays a significant role in influencing the morphology, crystallisation, porosity, Brunauer-Emmett-Teller (BET) specific surface area, and hierarchy of the TiO2 nanorod spheres, thus resulting in different photocatalytic performances under UV light and solar light irradiation. The experimental results have demonstrated that the hierarchical TiO2 nanorod spheres obtained after calcination of the crescent Ti/RF spheres at different temperatures displayed similar photocatalytic activities under irradiation with UV light. We attribute this to a balance of opposing effects of the investigated factors. A higher calcination temperature leads to greater light absorption capability of the TiO2 nanorod spheres, thus resulting in higher photocatalytic antibacterial activity under solar light irradiation. It is also interesting to note that the hierarchical TiO2 nanorod spheres displayed intrinsic antibacterial activity in the absence of light irradiation, apparently because their sharp outward spikes can easily pierce and penetrate the walls of bacteria. In this study, the sharpest hierarchical TiO2 nanorod spheres were obtained after calcination at 500 °C, and these exhibited the highest antibacterial activity without light irradiation. A higher calcination temperature proved detrimental to the sharpness of the TiO2 nanorods, thus reducing their intrinsic antibacterial activity. [ABSTRACT FROM AUTHOR]

Abstract: The nanosheets assembled hierarchical WO3 hollow microspheres were successfully synthesized by sintering acid-treated CaWO4 hollow microspheres precursor at 500°C. The as-obtained sample was characterized with field emission scanning electron microscopy, X-ray powder diffraction, transmission electron microscopy, and nitrogen adsorption and desorption measurements. The results indicated that the as-prepared product was monoclinic tungsten oxide and the nanosheet was single crystal and had a large amount of surface defects. The as-obtained sample had porous structures with a wide range of pore size distributions from 1nm to 170nm. The sensor based on this hierarchical structures exhibited excellent sensing properties to nitrogen dioxide (NO2) at relatively low operating temperature, and the response to 40ppb NO2 is about 16 at 75°C. The nanosheets assembled hierarchical WO3 hollow microspheres might have potential application to fabricate highly sensitive and low power consumption NO2 gas sensor. [Copyright &y& Elsevier]

A large-scale hierarchical assembly route is reported for the formation of SnO2 on the nanoscale that contains rigid and robust spheres with irregular channels for rapid access of Li ions into the hierarchically structured interiors. Large volume changes during the process of Li insertion and extraction are accommodated by the SnO2 nanoflake spheres' internal porosity. The hierarchical SnO2 nanoflake spheres exhibit good lithium storage properties with high capacity and long-lasting performance when used as lithium-ion anodes. A reversible capacity of 517 mA h g−1, still greater than the theoretical capacity of graphite (372 mA h g−1), after 50 charge-discharge cycles is attained. Meanwhile, the synthesis process is simple, inexpensive, safe, and broadly applicable, providing new avenues for the rational engineering of electrode materials with enhanced conductivity and power. [ABSTRACT FROM AUTHOR]

Electrospinning, an efficient technique to produce long fibers with micro- or nanoscale diameters, has attracted tremendous interests during past decades. By orchestrating parameters in electrospinning, diverse forms of fibrous assemblies and individual fibers with hierarchical structures can be successfully achieved. Some of these versatile micro- and nanostructures display a remarkable resemblance to the materials and objects existing in nature, such as honeycomb, spider webs, extracellular matrix, plant tendril and leaf, etc. The emerging field of biomimicry enables one to mimic biology or nature to develop novel nanomaterials as well as to improve processes for materials via electrospinning. In this review, we present a full panorama of recent studies on biomimicry via electrospinning, and highlight some of biomimicked one-dimensional nanomaterials as well as their functions and applications to date. [ABSTRACT FROM PUBLISHER]

Abstract: We report on a rapid, single-step method to produce large-area superhydrophobic surfaces via acetone-induced phase transformation of polycarbonate. Crystallization of the polymer leads to the formation of a hierarchical structure composed of microporous spherulites covered with nano-fibrils, and resulted in superhydrophobic wetting behavior. A systematic study of the dependence of surface morphology on the acetone treatment time was conducted to optimize the treatment time and to elucidate the structure formation mechanism. The resulting surfaces exhibit high contact angles, low contact angle hysteresis, and complete dewetting during droplet impact. Theoretical analysis of the wetting and anti-wetting pressures shows that the nano-scale morphology is critical for achieving droplet impact resistance. This simple phase transformation approach could be more broadly applied to other solvent–polymer systems for fabricating large-area hierarchical surface textures. [Copyright &y& Elsevier]

Various ZnO nanostructures such as porous nanorods and two hierarchical structures consisting of porous nanosheets or crystalline nanorods were prepared by the reaction of mixtures of oleic-acid-dissolved ethanol solutions and aqueous dissolved Znprecursor solutions in the presence of NaOH. All three ZnO nanostructures showed sensitive and selective detection of C2H5OH. In particular, ultra-high responses (Ra/Rg = ∼1,200, Ra: resistance in air, Rg: resistance in gas) to 100 ppm C2H5OH was attained using porous nanorods and hierarchical structures assembled from porous nanosheets, which is one of the highest values reported in the literature. The gas response and linearity of gas sensors were discussed in relation to the size, surface area, and porosity of the nanostructures. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a novel template of carbon foam is used in building hierarchical structures of TiO2, CeO2, and ZrO2. They had multiscale morphologies, from nanowalls, nanoparticles to layer nanostructures. On a hundred-micron scale, the product was a sponge-like material constructed by nanowalls. On a hundred-nanometer scale, the electron microscope images showed that the nanowalls were porous and assembled by polycrystalline nanoparticles. Meanwhile, on one nanometer scale, many nanoparticles exhibited layer nanostructures with about 1.1 nm of thickness and spacing. In mechanism section, the process analysis and characterizations suggested that the hierarchical structures were the combined result of two templates in a “one-pot” reaction. The mesoporous nanowalls were derived from carbon foams, while the layer nanostructures were the replicas of graphite sheets. The method has potential utilizations in preparation of various adsorbent and catalyst. [Copyright &y& Elsevier]

[Display omitted] • Hierarchical NiO nanosheets have been synthesized by the hydrothermal method. • Pneumatic microextrusion printing has been used for applying gas-sensitive coatings. • Obtained NiO coatings demonstrated increased sensitivity to hydrogen sulfide. • After H 2 S exposure gas-sensing properties of the NiO coating changed significantly. The formation of NiO nanosheets (average CSR size is 10.4 nm) through the hydrothermal method using a heteroligand complex of composition [Ni(C 5 H 7 O 2) 2-x (C 4 H 9 O) x ] as a precursor was studied. Using the obtained oxide nanopowder and pneumatic microextrusion printing, NiO coating was applied to the surface of a specialized Pt/Al 2 O 3 /Pt chip, and chemosensor properties were investigated in the detection of various gases. It was determined that when CO, NH 3 , H 2 , and NO 2 were detected, the conductivity of the NiO coating changed from p- to n-type with increasing temperature. Using XPS, XRD, and Raman spectroscopy, it was found that upon exposure to H 2 S, the surface of NiO coating partially undergoes irreversible chemical modification with the formation of nickel sulfide, resulting in a significant change in the sensory properties of the coating. It was shown that the formed receptor material exhibits the greatest response when detecting H 2 S, and the proposed approach, combining hydrothermal synthesis and printing technology, is promising for the creation of modern components of resistive gas sensors. [ABSTRACT FROM AUTHOR]

Forest-like ZnO hierarchical structures were synthesized on the conductive fabric substrate via a simple one-step electrochemical deposition process. By applying externally a high cathodic voltage to the samples, ZnO microrods were aligned on the seed coated layer and then ZnO branches were formed on the pillars of ZnO microrods, which was caused by the strong deposition potential between the pillars of ZnO microrods and the Zn2+ dissolved in growth solution. At the external cathodic voltage of -3 V, the optimized forest-like ZnO hierarchical structures exhibited high density, high porosity, and good crystallinity. These fabricated forest-like ZnO hierarchical structures are potentially useful for electronic and chemical sensing applications. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]