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Journal ArticleDOI

Fabrication of Macroscopically Flexible and Highly Porous 3D Semiconductor Networks from Interpenetrating Nanostructures by a Simple Flame Transport Approach

TL;DR: Flexible, electrically conducting, high temperature stable ceramics with very high porosities are fabricated from interpenetrated metal oxide nano-microstructures in a versatile manner in a novel flame transport synthesis approach.
Abstract: Flexible, electrically conducting, high temperature stable ceramics with very high porosities are fabricated from interpenetrated metal oxide nano‐microstructures in a versatile manner in a novel flame transport synthesis approach The Young's modulus of these networks can be tuned from wool type to rubber like based on the density, type and interconnections of the building blocks Semiconducting behavior allows multifunctional applications like the electrical readout of the mechanical history
Citations
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Journal ArticleDOI
TL;DR: In the last 15 years, more than 50,000 papers with zinc oxide (ZnO) in the title are listed within ISI database as mentioned in this paper, and the outstanding popularity of ZnO has many reasons; the most important one appears to be its multi-functionality resulting in applications in physics, chemistry, electrical engineering, material science, energy, textile, rubber, additive manufacturing, cosmetics, and pharmaceutical or medicine, as well as the ease to grow all kinds of nano- and microstructures.

472 citations

Journal ArticleDOI
TL;DR: Two flame-based synthesis methods are presented for fabricating ZnO-nanostructure-based UV photodetectors: burner flame transport synthesis (B-FTS) and crucible flame transporthesis (C-F TS).
Abstract: Au contacts. The B-FTS approach exhibits the unique feature of ultra-rapid growth of ZnO nanotetrapods within few milliseconds and simultaneously in situ bridging electrical contacts. These bridging nanotetrapods were directly integrated on a chip and demonstrated signifi cantly improved performances as a UV photodetector. Comparison of the UV photodetectors performances built from interpenetrating ZnO nano-microstructures fabricated by B-FTS and C-FTS techniques are presented. Fastest response/recovery time constant (≈32 ms) under 365 nm UV light irradiation of B-FTS-made photodetectors (on/off ratio ≈4.5 ◊ 10 3 at 2.4 V) is reported. Different type of nanojunctions formed between neighbor nanowires or nanotetrapods (with ‘arm’ thickness <50 nm) could be the reason for such improved characteristics. The role of nanojunctions in fast UV photodetectors from networked ZnO nanowires and nanotetrapods is discussed. On the basis of the rapid B-FTS fabrication process and fast UV photodetection capabilities, such networked ZnO nanotetrapods can be potential candidates for various nanosensor applications.

437 citations

Journal ArticleDOI
TL;DR: This work demonstrates the versatile and single-step synthesis of ZnO-T with different arm morphologies by a simple flame transport synthesis (FTS) approach, forming a network that will be of interest for various advanced applications.
Abstract: Growth of freestanding nano- and microstructures with complex morphologies is a highly desired aspect for real applications of nanoscale materials in various technologies. Zinc oxide tetrapods (ZnO-T), which exhibit three-dimensional (3D) shapes, are of major importance from a technological applications point of view, and thus efficient techniques for growth of different varieties of tetrapod-based networks are demanded. Here, we demonstrate the versatile and single-step synthesis of ZnO-T with different arm morphologies by a simple flame transport synthesis (FTS) approach, forming a network. Morphological evolutions and structural intactness of these tetrapods have been investigated in detail by scanning electron microscopy, X-ray diffraction, and micro-Raman measurements. For a deeper understanding of the crystallinity, detailed high-resolution transmission electron microscopic studies on a typical ZnO tetrapod structure are presented. The involved growth mechanism for ZnO tetrapods with various arm mor...

427 citations


Cites background from "Fabrication of Macroscopically Flex..."

  • ...structure is oriented along the [2-110] zone axis....

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Journal ArticleDOI
TL;DR: The results showed that Co doped ZnO nanodisks and nanorods exhibit highly enhanced photocatalytic activity, as compared to pure Zn O nanod risks and nanors, due to the combined effects of enhanced surface area and improved charge separation efficiency due to optimal Co doping.
Abstract: Cobalt doped ZnO nanodisks and nanorods were synthesized by a facile wet chemical method and well characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) with energy dispersive X-ray spectroscopy, photoluminescence spectroscopy, Raman spectroscopy and UV-visible absorption spectroscopy. The photocatalytic activities were evaluated for sunlight driven degradation of an aqueous methylene blue (MB) solution. The results showed that Co doped ZnO nanodisks and nanorods exhibit highly enhanced photocatalytic activity, as compared to pure ZnO nanodisks and nanorods. The enhanced photocatalytic activities of Co doped ZnO nanostructures were attributed to the combined effects of enhanced surface area of ZnO nanodisks and improved charge separation efficiency due to optimal Co doping which inhibit recombination of photogenerated charge carriers. The possible mechanism for the enhanced photocatalytic activity of Co doped ZnO nanostructures is tentatively proposed.

308 citations

Journal ArticleDOI
TL;DR: In this paper, the state-of-the-art gas-sensing nanomaterials and their future perspectives are summarized and summarized in detail such as the sensitivity, selectivity, reversibility, operating temperature, response time, and detection limit.
Abstract: The alarming rise of indoor pollution and the need to combat the associated negative effects have promoted increasing attention in modernizing the chemical sensing technologies by newly designed materials with rich and tunable functionalities at atomic or molecular levels. With the appealing physical, chemical, optical, and electronic properties for various potential applications, the state-of-art gas-sensing nanomaterials and their future perspectives are well-documented and summarized in this paper. Specifically, the key performance attributes are addressed in detail such as the sensitivity, selectivity, reversibility, operating temperature, response time, and detection limit. As such, this review provides both critical insights in exploring and understanding various gas sensing nanomaterials and points out limitations and opportunities for further developments, such as morphology control, doping and surface alteration, atomic-scale characterization, and applications in different fields. Finally, the challenges and outlooks are discussed on the basis of the current developments.

256 citations

References
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Journal ArticleDOI
TL;DR: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature.
Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

10,260 citations

Journal ArticleDOI
TL;DR: This review describes some recent developments in the discovery of nanoelectrolytes and nanoeLECTrodes for lithium batteries, fuel cells and supercapacitors and the advantages and disadvantages of the nanoscale in materials design for such devices.
Abstract: New materials hold the key to fundamental advances in energy conversion and storage, both of which are vital in order to meet the challenge of global warming and the finite nature of fossil fuels. Nanomaterials in particular offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. This review describes some recent developments in the discovery of nanoelectrolytes and nanoelectrodes for lithium batteries, fuel cells and supercapacitors. The advantages and disadvantages of the nanoscale in materials design for such devices are highlighted.

8,157 citations

Journal ArticleDOI
04 Nov 2004-Nature
TL;DR: A lead-free piezoelectric ceramic with an electric-field-induced strain comparable to typical actuator-grade PZT is reported, achieved through the combination of the discovery of a morphotropic phase boundary in an alkaline niobate-based perovskite solid solution, and the development of a processing route leading to highly textured polycrystals.
Abstract: Lead has recently been expelled from many commercial applications and materials (for example, from solder, glass and pottery glaze) owing to concerns regarding its toxicity. Lead zirconium titanate (PZT) ceramics are high-performance piezoelectric materials, which are widely used in sensors, actuators and other electronic devices; they contain more than 60 weight per cent lead. Although there has been a concerted effort to develop lead-free piezoelectric ceramics, no effective alternative to PZT has yet been found. Here we report a lead-free piezoelectric ceramic with an electric-field-induced strain comparable to typical actuator-grade PZT. We achieved this through the combination of the discovery of a morphotropic phase boundary in an alkaline niobate-based perovskite solid solution, and the development of a processing route leading to highly textured polycrystals. The ceramic exhibits a piezoelectric constant d33 (the induced charge per unit force applied in the same direction) of above 300 picocoulombs per newton (pC N(-1)), and texturing the material leads to a peak d33 of 416 pC N(-1). The textured material also exhibits temperature-independent field-induced strain characteristics.

4,689 citations

Journal ArticleDOI
12 Mar 2009-Nature
TL;DR: It is shown that batteries which obtain high energy density by storing charge in the bulk of a material can also achieve ultrahigh discharge rates, comparable to those of supercapacitors.
Abstract: The storage of electrical energy at high charge and discharge rate is an important technology in today's society, and can enable hybrid and plug-in hybrid electric vehicles and provide back-up for wind and solar energy. It is typically believed that in electrochemical systems very high power rates can only be achieved with supercapacitors, which trade high power for low energy density as they only store energy by surface adsorption reactions of charged species on an electrode material. Here we show that batteries which obtain high energy density by storing charge in the bulk of a material can also achieve ultrahigh discharge rates, comparable to those of supercapacitors. We realize this in LiFePO(4) (ref. 6), a material with high lithium bulk mobility, by creating a fast ion-conducting surface phase through controlled off-stoichiometry. A rate capability equivalent to full battery discharge in 10-20 s can be achieved.

3,187 citations

Journal ArticleDOI
TL;DR: The biomimetic process has been used to deposit nano-sized bone- like apatite on fine polymer fibers, which were textured into a three-dimensional knit framework, which is expected to ultimately lead to bioactive composites that have a bone-like structure and, hence,Bone-like mechanical properties.

1,744 citations

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