Revealing the Mechanisms behind SnO2 Nanoparticle Formation and Growth during Hydrothermal Synthesis: An In Situ Total Scattering Study

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• 作者：Kirsten M. 脴. Jensen ; Mogens Christensen ; Pavol Juhas ; Christoffer Tyrsted ; Espen D. B酶jesen ; Nina Lock ; Simon J. L. Billinge ; Bo B. Iversen
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：April 18, 2012
• 年：2012
• 卷：134
• 期：15
• 页码：6785-6792
• 全文大小：513K
• 年卷期：v.134,no.15(April 18, 2012)
• ISSN：1520-5126

文摘

The formation and growth mechanisms in the hydrothermal synthesis of SnO₂ nanoparticles from aqueous solutions of SnCl₄路5H₂O have been elucidated by means of in situ X-ray total scattering (PDF) measurements. The analysis of the data reveals that when the tin(IV) chloride precursor is dissolved, chloride ions and water coordinate octahedrally to tin(IV), forming aquachlorotin(IV) complexes of the form [SnCl_x(H₂O)_6鈥?i>x]^(4鈥?i>x)+ as well as hexaaquatin(IV) complexes [Sn(H₂O)_6鈥?i>y(OH)_y]^(4鈥?i>y)+. Upon heating, ellipsoidal SnO₂ nanoparticles are formed uniquely from hexaaquatin(IV). The nanoparticle size and morphology (aspect ratio) are dependent on both the reaction temperature and the precursor concentration, and particles as small as 2 nm can be synthesized. Analysis of the growth curves shows that Ostwald ripening only takes place above 200 掳C, and in general the growth is limited by diffusion of precursor species to the growing particle. The c-parameter in the tetragonal lattice is observed to expand up to 0.5% for particle sizes down to 2鈥? nm as compared to the bulk value. SnO₂ nanoparticles below 3鈥? nm do not form in the bulk rutile structure, but as an orthorhombic structural modification, which previously has only been reported at pressures above 5 GPa. Thus, adjustment of the synthesis temperature and precursor concentration not only allows control over nanoparticle size and morphology but also the structure.