Morphology-Controlled Growth of ZnO Nanostructures Using Microwave Irradiation: from Basic to Complex Structures
25 Jul 2008-Journal of Physical Chemistry C (American Chemical Society)-Vol. 112, Iss: 33, pp 12769-12776
TL;DR: In this paper, the growth of ZnO nano-and micro-structures was achieved by microwave irradiation with low power microwave-assisted heating (about 50 W) and subsequent aging process.
Abstract: Morphology-controlled growth of ZnO nano- and microstructures was achieved by microwave irradiation. Various basic ZnO structures, including nanorods, nanocandles, nanoneedles, nanodisks, nanonuts, microstars, microUFOs, and microballs were simply synthesized at a low temperature (90 °C) with low power microwave-assisted heating (about 50 W) and a subsequent aging process. These results could be obtained by changing the precursor chemicals, the capping agents, and the aging times. Even more complex ZnO structures, including ZnO bulky stars, cakes, and jellyfishes, were constructed by microwave irradiation to a mixture of the as-prepared basic ZnO structures and the solution I, IV, or V. This is a fast, simple, and reproducible method which does not require any template, catalyst, or surfactant but can control the morphology of ZnO crystals from simple to complex. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (X...
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TL;DR: In this paper, a brief overview of synthesis methods of ZnO nanostructures, with particular focus on the growth of perpendicular arrays of nanorods/nanowires which are of interest for optoelectronic device applications.
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TL;DR: Microwave-assisted methods that have been developed to synthesize colloidal inorganic nanocrystals are illustrated and the specific roles that microwave irradiation may play in the formation of these nanomaterials are critically evaluated.
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TL;DR: In this paper, a range of different morphologies have been synthesized via a simple solvothermal method with different solvents, and the optical properties of the as-prepared ZnO materials were investigated by UV−vis absorption and room temperature photoluminescence.
Abstract: ZnO materials with a range of different morphologies have been synthesized via a simple solvothermal method with different solvents. Zinc acetylacetonate was used as the zinc source in such solvothermal syntheses for the first time. XRD data showed that single-phase ZnO with the wurtzite crystal structure was obtained for all the solvents used. FE-SEM imaging showed that ZnO with cauliflower-like, truncated hexagonal conical, tubular and rodlike, hourglass-like, nanorods, and spherical shapes were produced when THF, decane, water, toluene, ethanol, and acetone were used as the solvent, respectively. The TEM data showed that the crystalline ZnO had different growth habits in the different solvents. The optical properties of the as-prepared ZnO materials were investigated by UV−vis absorption and room temperature photoluminescence. Photodegradation of phenol was used as a model reaction to test the photocatalytic activity of the ZnO samples. ZnO samples with different morphologies and crystal growth habits ...
424 citations
TL;DR: Oxide nanotechnology of the 21st century needs a strong interplay of preparative creativity, analytical skills, and new ideas for synergistic implementations to revolutionize areas ranging from data processing to biocatalysis.
Abstract: Oxide nanomaterials are indispensable for nanotechnological innovations, because they combine an infinite variety of structural motifs and properties with manifold morphological features. Given that new oxide materials are almost reported on a daily basis, considerable synthetic and technological work remains to be done to fully exploit this ever increasing family of compounds for innovative nano-applications. This calls for reliable and scalable preparative approaches to oxide nanomaterials and their development remains a challenge for many complex nanostructured oxides. Oxide nanomaterials with special physicochemical features and unusual morphologies are still difficult to access by classic synthetic pathways. The limitless options for creating nano-oxide building blocks open up new technological perspectives with the potential to revolutionize areas ranging from data processing to biocatalysis. Oxide nanotechnology of the 21st century thus needs a strong interplay of preparative creativity, analytical skills, and new ideas for synergistic implementations.
332 citations
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TL;DR: Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated and self-organized, <0001> oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process.
Abstract: Room-temperature ultraviolet lasing in semiconductor nanowire arrays has been demonstrated The self-organized, oriented zinc oxide nanowires grown on sapphire substrates were synthesized with a simple vapor transport and condensation process These wide band-gap semiconductor nanowires form natural laser cavities with diameters varying from 20 to 150 nanometers and lengths up to 10 micrometers Under optical excitation, surface-emitting lasing action was observed at 385 nanometers, with an emission linewidth less than 03 nanometer The chemical flexibility and the one-dimensionality of the nanowires make them ideal miniaturized laser light sources These short-wavelength nanolasers could have myriad applications, including optical computing, information storage, and microanalysis
8,592 citations
TL;DR: The beltlike morphology appears to be a distinctive and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures, which could be an ideal system for fully understanding dimensionally confined transport phenomena in functional oxides.
Abstract: Ultralong beltlike (or ribbonlike) nanostructures (so-called nanobelts) were successfully synthesized for semiconducting oxides of zinc, tin, indium, cadmium, and gallium by simply evaporating the desired commercial metal oxide powders at high temperatures. The as-synthesized oxide nanobelts are pure, structurally uniform, and single crystalline, and most of them are free from defects and dislocations. They have a rectanglelike cross section with typical widths of 30 to 300 nanometers, width-to-thickness ratios of 5 to 10, and lengths of up to a few millimeters. The beltlike morphology appears to be a distinctive and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures. The nanobelts could be an ideal system for fully understanding dimensionally confined transport phenomena in functional oxides and building functional devices along individual nanobelts.
5,677 citations
TL;DR: This work introduces a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires, which features a surface area up to one-fifth as large as a nanoparticle cell.
Abstract: Excitonic solar cells1—including organic, hybrid organic–inorganic and dye-sensitized cells (DSCs)—are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient2 and stable3 excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.
5,308 citations
TL;DR: In this paper, a review of various nanostructures of ZnO grown by the solid-vapour phase technique and their corresponding growth mechanisms is presented. And the application of nanobelts as nanosensors, nanocantilevers, field effect transistors and nanoresonators is demonstrated.
Abstract: Zinc oxide is a unique material that exhibits semiconducting and piezoelectric dual properties. Using a solid–vapour phase thermal sublimation technique, nanocombs, nanorings, nanohelixes/nanosprings, nanobelts, nanowires and nanocages of ZnO have been synthesized under specific growth conditions. These unique nanostructures unambiguously demonstrate that ZnO probably has the richest family of nanostructures among all materials, both in structures and in properties. The nanostructures could have novel applications in optoelectronics, sensors, transducers and biomedical sciences. This article reviews the various nanostructures of ZnO grown by the solid–vapour phase technique and their corresponding growth mechanisms. The application of ZnO nanobelts as nanosensors, nanocantilevers, field effect transistors and nanoresonators is demonstrated.
3,361 citations
TL;DR: In this paper, the authors investigate the feasibility of achieving electrically driven lasing from individual nanowires and show that these structures can function as Fabry-Perot optical cavities with mode spacing inversely related to the nanowire length.
Abstract: Electrically driven semiconductor lasers are used in technologies ranging from telecommunications and information storage to medical diagnostics and therapeutics. The success of this class of lasers is due in part to well-developed planar semiconductor growth and processing, which enables reproducible fabrication of integrated, electrically driven devices. Yet this approach to device fabrication is also costly and difficult to integrate directly with other technologies such as silicon microelectronics. To overcome these issues for future applications, there has been considerable interest in using organic molecules, polymers, and inorganic nanostructures for lasers, because these materials can be fashioned into devices by chemical processing. Indeed, amplified stimulated emission and lasing have been reported for optically pumped organic systems and, more recently, inorganic nanocrystals and nanowires. However, electrically driven lasing, which is required in most applications, has met with several difficulties in organic systems, and has not been addressed for assembled nanocrystals or nanowires. Here we investigate the feasibility of achieving electrically driven lasing from individual nanowires. Optical and electrical measurements made on single-crystal cadmium sulphide nanowires show that these structures can function as Fabry-Perot optical cavities with mode spacing inversely related to the nanowire length. Investigations of optical and electrical pumping further indicate a threshold for lasing as characterized by optical modes with instrument-limited linewidths. Electrically driven nanowire lasers, which might be assembled in arrays capable of emitting a wide range of colours, could improve existing applications and suggest new opportunities.
2,396 citations