Role of OH⁻ in the low temperature hydrothermal synthesis of ZnO nanorods

Abstract

BACKGROUND: ZnO nanorods, which have a wide range of applications, were grown on a Si substrate by low temperature hydrothermal synthesis. An understanding of the reaction mechanism of ZnO nanorods is crucial to control their growth kinetics. Therefore, the effect of OH − concentration in a zinc sulfate solution on the growth of ZnO nanorods was investigated in order to better understand the growth mechanism of ZnO nanorods.

Structural and Morphology of ZnO Nanorods Synthesized Using ZnO Seeded Growth Hydrothermal Method and Its Properties as UV Sensing

“…Li et al [10] and Song et al [11] deposited ZnO on silicon (Si)- substrate by using RF sputtering followed by hydrothermal reaction without any heat treatment, and they obtained columnar ZnO nanorods. These results show the importance of the heat treatment of ZnO seed layers in forming ZnO nanorods using the hydrothermal method.…”

Effect of ammonia on morphology, wettability and photoresponse of ZnO nanorods grown by hydrothermal method

“…The nanorods became thinner and sharper with higher pH, due to increased concentration of OH -ions [15]. Simultaneously, a continuous increase in pH caused the dissolution of ZnO [16]. Thus, The results were a dynamic equilibrium between ZnO formation and dissolution related to OH − ions.…”

Monitoring of ppm level humic acid in surface water using ZnO–chitosan nano-composite as fluorescence probe

“…. The solution was cooled to room temperature and its pH was adjusted to 11.0 by adding drop by drop 1.0 N NaOH solution in the presence of 100 mg NH 4 Cl (Song et al 2008). The resulting solution was continuously heated at 150°C under hydrothermal condition as before for 90 min.…”

“…Tuning of crystal growth in one direction by chemical synthesis is difficult (Wang et al 2004) unless some anisotropic force acts in the growth directions. It is reported (Song et al 2008) that the use of NH 4 Cl and Zn salt in alkaline (pH 11.0) hydrothermal synthesis leads to the formation of ZnO nanorods; we have made an attempt to perform similar synthesis of ZnO nanorod-CS composite using acid-depolymerised CS which contains primary amine groups. It is anticipated that the ZnO-CS composites should have positively charged outer surface and will interact with negatively charged HA by electrostatic attraction.…”