Growth and Optical Properties of Faceted Hexagonal ZnO Nanotubes

Abstract

Well-faceted hexagonal ZnO nanotubes were synthesized by a simple hydrothermal method and the subsequent aging process without any catalysts or templates. The formation of the tubular structure is closely linked to the polarity of ZnO and the selective adsorption behavior of Zn2+ amino complexes. The surface-related optical properties were studied with use of Raman and photoluminescence spectra. It was found that the oxygen vacancy-related visible emission intensity decreased while surface defect-related visible emission intensity increased when the nanotubes were annealed in oxygen ambient. The anomalous enhancement of PL integrated intensity with the temperature shows fairly high surface state density existing in ZnO nanotubes.

Growth of ZnO Nanorod Arrays on Flexible Substrates: Effect of Precursor Solution Concentration

“…The observed peaks at about 438 and 586 cm −1 are assigned to be E (2) 2 (high-frequency E 2 mode) and Quasi-LO (QLO), respectively, [33][34][35]. The peak at 329 cm −1 results from the multiple phonon scattering processes [36]. As can be seen from Figure 5, the intensities of the ZnO Raman peak become higher as the precursor concentration increases, which indicate the increase in the crystal quality of the nanorods and/or the increase in the coverage of the nanorod arrays on the substrate.…”

One-dimensional ZnO nanostructures: Solution growth and functional properties

“…40(b) [338]. Generally as the temperature was decreased from room temperature to 4.2 K, the photoluminescence intensity increased [104], and its temperature dependence [184]. The main UV emission peak, assigned as the shallow bound exciton [338], was blue-shifted from 378 nm to 368 nm, because the band gap of ZnO increases as temperature decreases following the Varshni relationship [359].…”

“…The final morphology and dimension of the nanostructures are determined by a competition between adsorption and desorption of the precursor molecules, or in other words crystal growth and dissolution processes [56,184]. At the initial stage, the growth rate is relatively high because of the high supersaturation degree of growth nutrient.…”

Controlling the morphology of yttrium oxide through different precursors synthesized by hydrothermal method

“…Open ends is a unique feature for nanotubes grown by rolling of lamellar structures, like C [22], BN [23], WS 2 [24], and so on. The nanotubes formed through that process normally possess hollow interior [25]. In their study, the polar surfaces having the higher energy of the ZnO nanotowers were dissolved in priority to decrease the system energy in the aging process, and resulted in formation of tubular structure.…”