Hybrid Nanoparticles Prepared by In-situ and Post-synthetic Surface Modification of Lanthanide-Based Nanoparticles with
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1007-S12-02
Hybrid Nanoparticles Prepared by In-situ and Post-synthetic Surface Modification of Lanthanide-Based Nanoparticles with Phosphonic Acid Derivatives Christoph Rill, Sorin Ivanovici, and Guido Kickelbick Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9/165, Vienna, A-1060, Austria ABSTRACT The use of various phosphonic acid derivatives – some of which contain polymerizable groups – as surface modifying agents for nanoparticles was studied both in-situ during the synthesis of lanthanide-based (Ln = Nd, Eu, Yb) nanoparticles at room temperature as well as in a separate step after the particle preparation by a hydrothermal method. In the single-pot in-situ method the phosphonic acid esters served as growth-limiting agent during particle formation leading to small nanoparticles with a size of only a few nanometers as determined by dynamic light scattering as well as transmission electron and atomic force microscopy. Free phosphonic acids as well as their silyl esters were used to modify the hydrothermally prepared neodymium hydroxide nanorods which had diameters of approx. 20 nm and a length ranging up to a few micrometers. The surface modification was confirmed by infrared spectroscopy and thermogravimetric analysis. INTRODUCTION Organic surface functionalization of nanoparticles plays an important role in fine-tuning of the nanoparticles’ properties and in the synthesis of nanocomposite materials. The modification can be used to improve the particles’ solubility by preventing agglomeration [1]. Similarly, a suitable linker can help to prevent phase separation in the preparation of inorganicorganic hybrid materials [2]. For prosthetic materials Phillips et al. used allylphosphonic acid as coupling agent between ceramics and a matrix [3]. A different aspect is the effect of the surface modification on the physical properties of the particles, especially when investigating lanthanidebased systems where luminescence plays a major role. A strong influence of surface modification on the luminescence of nanoparticles has been reported [1, 4]. Phosphonic acids generally have big potential as surface modifying agents because of their compatibility with organic or biological materials and their strong interaction with transition metal-based materials such as oxides or hydroxides [5]. The topic of the present study is the use of various phosphonic acid derivatives as surface functionalization agent for lanthanide-based nanoparticles. The role of their presence during particle preparation as well as their use in a separate post-synthetic step was investigated.
EXPERIMENTAL Phosphonic acid derivatives With the exception of phenylphosphonic acid (PhPA, Aldrich) the phosphonic acid (PA) derivatives depicted in Scheme 1 were synthesized by the well-documented Michaelis-Arbuzov reaction [6], followed by transesterification with trimethylbromosilane (TMBS) or acidic hydrolysis. Allyl phosphonic acid (APA) was prepared by heating allylbromide and an excess of tri-i-propylphosphite to ~160°C
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