Effect of Amorphous Silica Nanomatrix on Kinetics of Metalation of Encapsulated Porphyrin Molecules

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• 作者：Song Liang ; Shay Hartvickson ; Evguenii Kozliak ; Julia Xiaojun Zhao
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：November 5, 2009
• 年：2009
• 卷：113
• 期：44
• 页码：19046-19054
• 全文大小：319K
• 年卷期：v.113,no.44(November 5, 2009)
• ISSN：1932-7455

文摘

Fabrication of functional nanomaterials can be achieved by incorporating functional molecules into a nanomatrix. Amorphous silica nanoparticles are often employed as a matrix or carrier, along with a functional component, to form silica-based nanomaterials. Physical and chemical properties of the encapsulated molecules, including reaction kinetics, may be affected by the nanomatrix. In this work, the metalation of meso-tetra (4-N,N,N-trimethylanilinium) porphyrin tetrachloride (TTMAPP) with Cu(II) was selected as a model for a kinetic study. Various sized silica nanomatrixes were synthesized for investigating the size effect of the nanomatrix on the kinetics of encapsulated molecules. The results demonstrated that the encapsulated molecules retained reactivity but the reaction rate constant greatly declined in the silica nanomatrix in comparison to free TTMAPP molecules in a bulk solution. An increase of the nanomatrix size resulted in a significant and consistent decline of the reaction rate constant. On the basis of the activation energies and rate constant values, a diffusion-controlled mechanism (both simple and adsorption-based diffusion) was proposed for the reactions occurring inside the silica nanomatrix. Further support for this mechanism was obtained in the TTMAPP metalation with Zn(II).