Abstract
Flower‐like bundles of ZnO nanosheets have been prepared by using preheating hydrothermal process without any surfactants. The flower‐like bundles consist of many thin and uniform hexagonal‐structured ZnO nanosheets, with a thickness of 50 nm. The selected area electronic diffraction (SAED) and high‐resolution transmission electron microscope (HRTEM) images indicate that the ZnO nanosheets are single crystal in nature. The growth mechanism of the flower‐like bundles of ZnO nanosheets is discussed based on the morphology evolution with growth times and reaction conditions. It is believed that the formation of flower‐like bundles of ZnO nanosheets is related to the shielding effect of OH− ions and the self‐assembly process, which is dominated by a preheating time. Room temperature photoluminescence spectra results show that the annealing atmosphere strongly affects the visible emission band, which is sensitive to intrinsic and surface defects, especially oxygen interstitials, in flower‐like bundles of ZnO nanosheets.
Highlights
One of the most important goals of nanoscience and nanotechnology is to develop simpler method for a largescale synthesis of nanomaterials with full control of size and morphology, because size, shape, and crystal structure are crucial factors in determining the chemical, optical, and electrical properties of nanoscale materials [1,2,3,4]
It can be seen from the low magnification top view field-emission scan electron microscopy (FESEM) image shown in Figure 1(a) that high density flower-like ZnO architectures uniformly grow and highly disperse in the substrates without any aggregation, indicating high yield and good uniformity achieved with this fabrication condition
The flower-like ZnO architectures with a diameter of 40– 50 μm, which consist of large numbers of thin and uniform hexagonal-structured ZnO nanosheets with a thickness of 40–50 nm, have been synthesized by using preheating hydrothermal method without any additives
Summary
One of the most important goals of nanoscience and nanotechnology is to develop simpler method for a largescale synthesis of nanomaterials with full control of size and morphology, because size, shape, and crystal structure are crucial factors in determining the chemical, optical, and electrical properties of nanoscale materials [1,2,3,4]. Vapor-phase process such as molecular beam epitaxy (MBE) [21], metal-organic chemical vapor deposition (MOCVD) [22], sputtering method [23], pulsed laser deposition (PLD) [24], infrared irradiation [25], thermal decomposition [26], and thermal evaporation and condensation [27] is favored for their simplicity and high quality products. These methods generally require high temperatures, high vacuums, rigorous procedures, and expensive pieces of equipment, which may limit potential applications, requiring large-scale production. Flower-like bundles of ZnO nanorods or needles or sheets have been intensively reported by using surfactant-free hydrothermal method [44,45,46,47] and ZnO flowers made up of thin nanosheets were fabricated by using organic solvent at high temperature (180∘C) [48], it is a challenge to fabricate flowerlike bundles of ZnO nanosheets by surfactant-free aqueous solution phase method at low growth temperature
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