Simultaneous Phase Transfer and Surface Modification of TiO2 Nanoparticles Using Alkylphosphonic Acids: Optimization and Structure of the Organosols

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• 作者：C茅line Schmitt Pauly ; Anne-Caroline Genix ; Johan G. Alauzun ; Gilles Guerrero ; Marie-Sousai Appavou ; Javier P茅rez ; Julian Oberdisse ; P. Hubert Mutin
• 刊名：Langmuir
• 出版年：2015
• 出版时间：October 13, 2015
• 年：2015
• 卷：31
• 期：40
• 页码：10966-10974
• 全文大小：388K
• ISSN：1520-5827

文摘

An original protocol of simultaneous surface modification and transfer from aqueous to organic phases of anatase TiO₂ nanoparticles (NPs) using alkylphosphonic acids (PAs) is studied. The influence of the solvent, the nature and concentration of the PA, and the size, concentration, and aggregation state of the TiO₂ NPs was investigated. Complete transfer was observed for linear alkyl chains (5, 8, 12, and 18 C atoms), even at very high sol concentrations. After transfer, the grafted NPs were characterized by ³¹P solid-state MAS NMR. The dispersion state of NPs before and after phase transfer was monitored by dynamic light scattering (DLS). Small-angle neutron scattering (SANS) was used to characterize the structure of PA-grafted NPs in the organic solvent. Using a quantitative core鈥搒hell model cross-checked under different contrast conditions, it is found that the primary particles making up the NPs are homogeneously grafted with a solvated PA-layer. The nanometric thickness of the latter is shown to increase with the length of the linear carbon chain of the PA, independent of the size of the primary TiO₂ NP. Interestingly, a reversible temperature-dependent aggregation was evidenced visually for C₁₈PA, and confirmed by DLS and SANS: heating the sample induces the breakup of aggregates, which reassemble upon cooling. Finally, in the case of NPs agglomerated by playing with the pH or the salt concentration of the sols, the phase transfer with PA is capable of redispersing the agglomerates. This new and highly versatile method of NP surface modification with PAs and simultaneous transfer is thus well suited for obtaining well-dispersed grafted NPs.