Growth of ZnO Nanostructures with Different Morphologies by Using Hydrothermal Technique

Abstract

ZnO nanostructures, including nanotowers, nanovolcanoes, nanorods, nanotubes, and nanoflowers, have been grown by using the hydrothermal technique. Most of the ZnO nanostructures show the perfect hexagonal cross section and well-faceted top and side surfaces. The basic chemistry and growth mechanism are discussed. By increasing the reaction time, the volcano-like and tube-like ZnO structures were formed due to the Ostwald ripening process and the selective adsorption of the complexes. By using the seed layer, the dense-arrayed, regular oriented ZnO nanorods were obtained due to the decreased nucleation barrier and the abundant interfaces as well as the increasing surface roughness.

Temperature‐Controlled Synthesis and Photocatalytic Performance of ZnO Nanoplatelets

“…[14,24] In particular, we propose that the obtained ZnO nanoplatelets were derived from the synergistic combination of a catalyst-free VS mechanism and direction-conducting growth, rather than from the traditional catalyst-assisted vapor-liquid-solid mechanism, [5] since no metal droplets are employed in the adopted preparation route. [27,30] Literature contributions have considered oxygen concentration in the reaction ambient as a key factor in governing the formation of ZnO nanostructures. [6,24] To this regard, while CVD experiments performed in the absence of water produced an isotropic growth (see above), water vapor introduction into the reaction ambient enhanced the precursor decomposition (Fig.…”

“…[9,10,14,21,[24][25][26] Up to date, 1D and 2D ZnO-based nanomaterials have been prepared by both liquid-and gas-phase techniques, including solvothermal routes, sol-gel, impregnation, laser-assisted methods, evaporation, pyrolysis, and CVD. [2][3][4][5][6][7][8][9][10][13][14][15][16]18,19,24,[26][27][28][29][30] In spite of the relevant number of studies on these topics, a thorough understanding and control of the basic growth mechanism still remains a significant challenge. [27,28] To this regard, CVD processes have received considerable attention for the synthesis of supported nanosystems with tailored properties, even on large-area substrates.…”

One-dimensional ZnO nanostructures: Solution growth and functional properties

“…With prolonged hydrothermal treatment, the reaction reaches a certain equilibrium, and the solution composition is no longer thermodynamically favorable for formation of Zn(OH) 2 that can subsequently dehydrate into ZnO [87], and the rate of ZnO dissolution is faster than the rate of formation [174]. As discussed previously, the polar surfaces will be dissolved preferentially since this decreases the system energy during the subsequent aging process, and that gradually leads to the formation of ZnO nanotubes [183,185], as illustrated in Fig. 14 [186].…”

Effect of solvents on ZnO nanostructures synthesized by solvothermal method assisted by microwave radiation: a photocatalytic study

“…The growth habit of a crystal is mainly due to the difference in the growth rates of the various crystals facets [49]. In this case, due to the difference in surface energies, the growth velocity of the (0001) planes is higher than that of the (10 10) planes [50]. For hydrothermal synthesis, it has been reported that the maximal crystal growth velocity is fixed in [0001] direction, and the relationship between velocities of crystal growth to different directions is found to be…”