The surface functionalization of TiO2-based materials with alkylsilanes is attractive in several cutting-edge applications, such as photovoltaics, sensors, and nanocarriers for the controlled release of bioactive molecules. (3-Aminopropyl)-triethoxysilane (APTES) is able to self-assemble to form monolayers on TiO2 surfaces, but its adsorption geometry and solar-induced photodegradation pathways are not well understood. We here employ advanced experimental (XPS, NEXAFS, AFM, HR-TEM, and FT-IR) and theoretical (plane-wave DFT) tools to investigate the preferential interaction mode of APTES on anatase TiO2. We demonstrate that monomeric APTES chemisorption should proceed through covalent Si−O−Ti bonds. Although dimerization of the silane through Si−O−Si bonds is possible, further polymerization on the surface is scarcely probable. Terminal amino groups are expected to be partially involved in strong charge-assisted hydrogen bonds with surface hydroxyl groups of TiO2, resulting in a reduced propensity to react with other species. Solar-induced mineralization proceeds through preferential cleavage of the alkyl groups, leading to the rapid loss of the terminal NH2 moieties, whereas the Si-bearing head of APTES undergoes slower oxidation and remains bound to the surface. The suitability of employing the silane as a linker with other chemical species is discussed in the context of controlled degradation of APTES monolayers for drug release and surface patterning

A Close Look at the Structure of the TiO2 ‑APTES Interface in Hybrid Nanomaterials and Its Degradation Pathway : An Experimental and Theoretical Study / D. Meroni, L. Lo Presti, G. Di Liberto, M. Ceotto, R.G. Acres, K.C. Prince, R. Bellani, G. Soliveri, S. Ardizzone. - In: JOURNAL OF PHYSICAL CHEMISTRY. C. - ISSN 1932-7447. - 2017:121(2017 Jan 12), pp. 430-440. [10.1021/acs.jpcc.6b10720]

A Close Look at the Structure of the TiO2 ‑APTES Interface in Hybrid Nanomaterials and Its Degradation Pathway : An Experimental and Theoretical Study

D. Meroni
;
L. Lo Presti
;
G. Di Liberto;M. Ceotto
;
G. Soliveri
Penultimo
;
S. Ardizzone
Ultimo
2017

Abstract

The surface functionalization of TiO2-based materials with alkylsilanes is attractive in several cutting-edge applications, such as photovoltaics, sensors, and nanocarriers for the controlled release of bioactive molecules. (3-Aminopropyl)-triethoxysilane (APTES) is able to self-assemble to form monolayers on TiO2 surfaces, but its adsorption geometry and solar-induced photodegradation pathways are not well understood. We here employ advanced experimental (XPS, NEXAFS, AFM, HR-TEM, and FT-IR) and theoretical (plane-wave DFT) tools to investigate the preferential interaction mode of APTES on anatase TiO2. We demonstrate that monomeric APTES chemisorption should proceed through covalent Si−O−Ti bonds. Although dimerization of the silane through Si−O−Si bonds is possible, further polymerization on the surface is scarcely probable. Terminal amino groups are expected to be partially involved in strong charge-assisted hydrogen bonds with surface hydroxyl groups of TiO2, resulting in a reduced propensity to react with other species. Solar-induced mineralization proceeds through preferential cleavage of the alkyl groups, leading to the rapid loss of the terminal NH2 moieties, whereas the Si-bearing head of APTES undergoes slower oxidation and remains bound to the surface. The suitability of employing the silane as a linker with other chemical species is discussed in the context of controlled degradation of APTES monolayers for drug release and surface patterning
APTES; Titania surface; NEXAFS; XPS; AFM; HR-TEM; FT-IR
Settore CHIM/02 - Chimica Fisica
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/478599
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