Tuning Nanoparticle Properties—The X‐ray Absorption Spectroscopic Point of View

Abstract

A key requirement for the realization of nanotechnology's technological potential is the ability to produce nanoparticles with well defined, tailored properties in a cheap and reproducible way. For numerous materials, wet‐chemical approaches with scale‐up potential exist which allow to synthesize stabilized particles of a given size, but it turns out that control of these two parameters is not sufficient to control particle properties completely. This suggests that the exact way of stabilization and the course of the synthesis may exert notable influence on particle properties. This work reviews experimental evidence for such influence with a focus on the perspective of x‐ray absorption spectroscopy. The thus obtained results indicate that not only size‐dependent phase transitions, but also chemical interaction between the core of the nanoparticle and its surfactant molecules are responsible for the observed spectral changes, which can be explained when constructing detailed models of core‐surfactant interaction. Also, it is observed that the surfactant can influence the course of the synthesis of a given nanoparticle notably. All of these results suggest a possibility to refine the finetuning of particle properties by exerting influence on synthesis and surface‐matrix interaction by suitable choice of surfactant molecules.

Keywords:

• X‐ray absorption spectroscopy
• XANES
• EXAFS
• Nanoparticles
• Surface effects
• Size effects

Acknowledgments

The author thanks the DFG for funding under contract numbers Mo 940‐1 and Mo 940‐3. Also, this work could not be what it is without the excellent collaboration with numerous experimentalists from chemistry and physics, e.g., Dr. Gesa Köhl, Dr. Stephanie Bucher, Natalie Palina, Dr. Vadim Palshin, Dr. Ed Doomes, Prof. Dr. H. Bönnemann, and his research group, Dr. C. R. R. Kumar of CAMD/LSU, PD Dr. E. Hartmann, IOM Leipzig, and Dr. R. Müller, Jena.