Chemical Bath Deposition of ZnO Nanowires at Near-Neutral pH Conditions without Hexamethylenetetramine (HMTA): Understanding the Role of HMTA in ZnO Nanowire Growth

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• 作者：Kevin M. McPeak ; Thinh P. Le ; Nathan G. Britton ; Zhorro S. Nickolov ; Yossef A. Elabd ; Jason B. Baxter
• 刊名：Langmuir
• 出版年：2011
• 出版时间：April 5, 2011
• 年：2011
• 卷：27
• 期：7
• 页码：3672-3677
• 全文大小：891K
• 年卷期：v.27,no.7(April 5, 2011)
• ISSN：1520-5827

文摘

Chemical bath deposition (CBD) is an inexpensive and reproducible method for depositing ZnO nanowire arrays over large areas. The aqueous Zn(NO₃)₂鈭抙examethylenetetramine (HMTA) chemistry is one of the most common CBD chemistries for ZnO nanowire synthesis, but some details of the reaction mechanism are still not well-understood. Here, we report the use of in situ attenuated total reflection Fourier transform infrared (ATR鈭扚TIR) spectroscopy to study HMTA adsorption from aqueous solutions onto ZnO nanoparticle films and show that HMTA does not adsorb on ZnO. This result refutes earlier claims that the anisotropic morphology arises from HMTA adsorbing onto and capping the ZnO {10 1虆 0} faces. We conclude that the role of HMTA in the CBD of ZnO nanowires is only to control the saturation index of ZnO. Furthermore, we demonstrate the first deposition of ZnO nanowire arrays at 90 掳C and near-neutral pH conditions without HMTA. Nanowires were grown using the pH buffer 2-(N-morpholino)ethanesulfonic acid (MES) and continuous titratation with KOH to maintain the same pH conditions where growth with HMTA occurs. This semi-batch synthetic method opens many new opportunities to tailor the ZnO morphology and properties by independently controlling temperature and pH.