Photochemistry of semiconductor colloids. Preparation of extremely small ZnO particles, fluorescence phenomena and size quantization effects

Koch, Ueli; Fojtík, A.; Weller, Horst; Henglein, A.

doi:10.1016/0009-2614(85)87255-9

Cited by 445 publications

(281 citation statements)

References 9 publications

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“…[2][3][4]15 However, quantum confinement effects in the ZnO nanoparticle array were not observed, presumably because of the relatively large diameter of the nanoparticle. [5][6][7] In conclusion, we successfully demonstrated the synthesis of photoluminescent ZnO nanoparticles in an ordered array on the solid substrate conserving the dimensional order of PS-PVP diblock copolymer micelles. Thus, the array of optically active nanoparticles was directly fabricated on the substrate with a single synthetic step, instead of separated procedures for the synthesis and deposition of nanoparticles.…”

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confidence: 77%

Self-assembled arrays of zinc oxide nanoparticles from monolayer films of diblock copolymer micelles

et al. 2004

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A hexagonal array of optically active ZnO nanoparticles was synthesized in situ on the solid substrate by utilizing a singlelayered film of diblock copolymer micelles as a nanostructured template.During the last decade, research on semiconductor nanoparticles has been a wide and interdisciplinary field of science to elucidate and utilize their novel material properties. 1 Zinc oxide, a wideband-gap semiconductor oxide, is a very fascinating material due to its large exciton binding energy and bond strength, 2,3 which make it applicable for a blue or ultraviolet optical device. [2][3][4] Nanoparticles of zinc oxide can be effectively synthesized in aqueous or organic solutions. Colloidal synthetic routes for ZnO nanoparticles usually involve the reaction of Zn 21 salts in basic solutions. [5][6][7] For their applications, however, controlled deposition of ZnO nanoparticles from solutions to solid substrates is necessary. To place nanoparticles on a substrate in a specific arrangement, templates have been utilized, which can be lithographically fabricated or self-assembled. [8][9][10][11][12][13][14] In the case of self-assembled templates, a periodic nanostructure of diblock copolymers or their micelles was successfully employed to arrange nanoparticles with a considerable stability. [10][11][12][13][14] For example, the nanometre-sized micelles of diblock copolymers in a selective solvent for one of the blocks were transferred onto silicon wafers to form a hexagonally ordered monolayer film, which served as a structured template to direct the spatial location of nanoparticles. [10][11][12][13][14] In addition, an ordered array of metal or oxide nanoparticles was directly synthesized by employing plasma treatments as a successful method of oxidation or reduction of precursors of nanoparticles as well as removal of copolymer templates. Möller and coworkers demonstrated arrays of gold nanoparticles on various substrates with a combination of diblock copolymer micelles and plasma treatments. 11 Similarly, we reported an array of iron oxide nanoparticles surrounded by gold nanoparticles from a monolayer film of diblock copolymer micelles with subsequent exposure to oxygen plasma. 13 The fabricated arrays of nanoparticles from diblock copolymer micelles, however, were applied mostly to passive applications such as an etching resistant mask. As an active nanopattern, an array of cobalt nanoparticles was recently synthesized from diblock copolymer micelles although magnetic properties of the array were not reported. 12 In this communication, we demonstrate instant synthesis of optically active ZnO nanoparticles in a hexagonal order from a single-layered film of diblock copolymer micelles with oxygen plasma treatment. The near-band-edge emission was observed for the array of ZnO nanoparticles.For a monolayer film of diblock copolymer micelles, polystyrene-block-poly(4-vinylpyridine), PS-PVP (M n PS~4 7.6 kg mol 21 , M n PVP~2 0.4 kg mol 21 , polydispersity index~1.14) was dissolved in toluene and stirred for 3 h at room ...

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confidence: 77%

Self-assembled arrays of zinc oxide nanoparticles from monolayer films of diblock copolymer micelles

et al. 2004

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“…The absorption spectrum shows a well-defined exciton band at 355 nm and a significant blue shift relative to the bulk exciton absorption (373 nm) [44]. This blue shift phenomenon is mainly related to the quantum confinement effect due to the small size of ZnO [45]. The most direct way of extracting the optical bandgap is to simply determine the photon energy at which there is a sudden increase in the absorption.…”

Section: Optical Propertiesmentioning

confidence: 99%

Study of structural, morphological, optical and electroluminescent properties of undoped ZnO nanorods grown by a simple chemical precipitation

Singh¹,

Vishwakarma²

2015

Materials Science-Poland

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In this work, zinc oxide (ZnO) nanorods were obtained by a simple chemical precipitation method in the presence of capping agent: polyvinyl pyrrolidone (PVP) at room temperature. X-ray diffraction (XRD) result indicates that the synthesized undoped ZnO nanorods have hexagonal wurtzite structure without any impurities. It has been observed that the growth direction of the prepared ZnO nanorods is [1 0 1]. XRD analysis revealed that the nanorods have the crystallite size of 49 nm. Crystallite size is calculated by Debye-Scherrer formula and lattice strain is calculated by Williomson-Hall equation. Cell volume, Lorentz factor, Lorentz polarization factor, bond length, texture coefficient, lattice constants and dislocation density have also been studied. We also compared the interplanar spacings and relative peak intensities with their standard values at different angles. The scanning electron microscope (SEM) images confirmed the size and shape of these nanorods. It has been found that the diameter of the nanorods ranges from 1.52 µm to 1.61 µm and the length is about 4.89 µm. It has also been observed that at room temperature ultraviolet visible (UV-Vis) absorption band is around 355 nm (blue shifted as compared to the bulk). The average particle size has also been calculated by mathematical model of effective mass approximation equation, using UV-Vis absorption peak. Finally, the bandgap has been calculated using UV-absorption peak. Electroluminescence (EL) studies show that emission of light is possible at very small threshold voltage and it increases rapidly with increasing applied voltage. It is seen that smaller ZnO nanoparticles give higher electroluminescence brightness starting at lower threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

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“…[4][5][6] The unique properties of semiconducting nanocrystals have motivated a number of studies on ZnO nanocrystals, which were manufactured using various synthesis methods. [7][8][9] However, one of the central problems of ZnO nanocrystals is that the desired UV band-gap luminescence is weak. [10][11][12][13] One solution for enhancing the near-band-edge emission UV emission in ZnO nanocrystals is to encapsulate the nanocrystals with protective surface layers.…”

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confidence: 99%

Synthesis of ZnO nanocrystals by subsequent implantation of Zn and O species

Lee

Tewell

Schulze

et al. 2005

Applied Physics Letters

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We report the preparation of ZnO nanocrystals embedded in a SiO2 matrix formed using sequential zinc and oxygen ion implantations. The optical absorption spectra and photoemission spectra of zinc implanted and zinc/oxygen coimplanted silica show that the first zinc implantation produces zinc clusters and that the subsequent oxygen implantation following the zinc implantation rearranges the distribution of zinc and oxygen ions at an atomic level. While thermal annealing of Zn only implanted silica leads to the formation of Zn nanocrystals, thermal annealing of zinc/oxygen coimplanted silica promotes the growth of ZnO nanocrystals. The absorption and photoluminescence spectra show that ZnO nanocrystals form in an amorphous SiO2 matrix and that their systematic change as a function of annealing temperature corresponds to the typical correlation between the increase of particle size and a redshift in near-band-edge emission.

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Photochemistry of semiconductor colloids. Preparation of extremely small ZnO particles, fluorescence phenomena and size quantization effects

Cited by 445 publications

References 9 publications

Self-assembled arrays of zinc oxide nanoparticles from monolayer films of diblock copolymer micelles

Self-assembled arrays of zinc oxide nanoparticles from monolayer films of diblock copolymer micelles

Study of structural, morphological, optical and electroluminescent properties of undoped ZnO nanorods grown by a simple chemical precipitation

Synthesis of ZnO nanocrystals by subsequent implantation of Zn and O species

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