Two-Step Grain-Growth Kinetics of Sub-7 nm SnO2 Nanocrystal under Hydrothermal Condition

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• 作者：Yuelan Zhang ; Liping Li ; Jing Zheng ; Qi Li ; Ying Zuo ; Errui Yang ; Guangshe Li
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：August 20, 2015
• 年：2015
• 卷：119
• 期：33
• 页码：19505-19512
• 全文大小：548K
• ISSN：1932-7455

文摘

In this work, the grain growth kinetics of SnO₂ quantum dots under hydrothermal conditions was investigated. By varying the reaction temperature and duration, SnO₂ particle sizes were tuned from 2 to 7 nm. It is demonstrated that the growth behavior of subnanometer-sized SnO₂ underwent two distinct processes: below the critical size of 5.5 nm, about double of Bohr radius, the grain growth kinetics obeys an Ostwald ripening mechanism, while above that, an oriented attachment process governs the particle growth. For the former cases, the activation energies were E_a1 = 61.94 kJ/mol at 200 掳C and E_a1鈥?= 62.84 kJ/mol at 160 掳C, which greatly differs from that of E_a2 = 131.32 kJ/mol for the latter case. High-resolution transmission electron microscope, X-ray diffraction as well as UV鈥搗is diffuses reflectance, photoluminescence, Fourier transmission infrared, and Raman spectra were employed to reveal the size-dependent properties. As the particle size of SnO₂ reduces, there occurred a lattice expansion, band gap broadening, and an abnormal blue shift. All these characteristics are closely related to the size changing in a narrow range from quantum dots to several nanometers. The findings reported here may shed light on further understanding the unique behaviors of quantum dots.