Synthesizing, functionalizing and exploring metal nanoparticles for biophysical single molecule studies, and new materials
Zusammenfassung der Projektergebnisse
Noble metal particles with nanometer-scale dimensions exhibit interesting optical properties due to the excitation of the plasmon resonance. Taking advantage of the unique optical characteristics of metal nanoparticles – strong plasmon absorption, resonant light scattering and enhanced localized electromagnetic fields – many applications have emerged using nanoparticles as optical label or as sensitive nanosensor. Metal nanoparticles as labels in biophysical studies have advantages over commonly used fluorescence markers as they neither blink nor bleach and provide both distance and orientation information. For materials science and devices, the large field enhancement under optical illumination, the change in color upon changes in their environment, and the directed scattering will prove useful for applications ranging from fundamental research, new biosensors to decorative coloring. All applications requiring the use of metal nanoparticles rely on a reproducible, high-yield synthesis. To optimize the conditions of the wet-chemistry route of producing particles of different size, shape and composition, we continuously monitor the growth combining optical spectroscopy and time resolved small-angle X-ray scattering (SAXS) measurements. Interestingly, in the case of the formation of rodshaped particles, we find two regimes: a 1D growth in the first ten minutes, followed by a 3D growth. Varying the composition of the metallic salt, we are able to synthesize new materials, including copper-gold alloyed nanorods, hollow core-shell nanoparticles and bi-metallic nanoparticles consisting of a gold core and a silver shell. In the later case, we discover a surprising effect, termed as plasmonic focusing, corresponding to the narrowing of the ensemble plasmon line-width. Such particles are well-suitable for plasmonic applications. An important step, prior to the use of nanoparticles in biophysical studies, is the ability to functionalize them. We develop an original strategy to modify the surface chemistry of the particles by grafting a polymer, PolyEthylenGlycol (PEG). It provides anchoring points to attach different biomolecules, helps in the stabilization of the particles in buffer conditions and reduces the nanotoxicity of the particles. If anisotropic functionalization is sometimes desirable, it is also extremely difficult to achieve. We are to show that the choice of hybrid materials for anisotropic functionalization can be brought into very general use – from metal-semi-conducting to metal-oxide materials. Besides, it offers the possibility to combine both the properties of the different components. Single particle experiments are the core of our research. We have developed several experimental systems allowing us measuring several tens of particles at the time, monitoring both spectral and polarization properties of nanoparticles for instance. We demonstrate that single particle measurements can be used to provide distance and orientation information. We also report the ability to design a binding sensor based on biomembranes. Together with such an experimental approach, we acquire a strong expertise in numerical simulations. This allows us better understanding the plasmon properties of single particles as well as optimizing experimental conditions. Finally, regular particles arrangement on a substrate can give rise to new materials with surprising properties. We explore new ways to fabricate new optical devices such as using scalable lithographic techniques or orienting anisotropic nanoparticles by formation of lyotropic liquid crystals from rigid-rod objects.
Projektbezogene Publikationen (Auswahl)
- Microfluidic continuous flow synthesis of rod-shaped gold and silver nanocrystals. Phys. Chem. Chem. Phys., 8, 3824-3827 (2006)
Boleininger J., Kurz A., Reuss V. and Sönnichsen C.
- Gold nanoparticle growth monitored in situ using a novel fast optical singleparticle spectroscopy method. Nano Lett., 7, 1664-1669 (2007)
Becker J., Schubert O. and Sönnichsen C.
- Self-assembly of small gold colloids with functionalized gold nanorods. Nano Lett., 7, 259-263 (2007)
Pierrat S., Zins I., Breivogel A. and Sönnichsen C.
- Separation of nanoparticles by gel electrophoresis according to size-and shape. Nano Lett., 7, 2881-2885 (2007)
Hanauer M., Pierrat S., Zins I., Lotz A. and Sönnichsen C.
- Mapping the polarization pattern of plasmon modes reveals nanoparticle symmetry. Nano Lett., 8, 2345-2350 (2008)
Schubert O., Becker J., Carbone L., Khalavka Y., Provalska T., Zins I. and Sönnichsen C.
- Plasmonic focusing reduces ensemble linewidth of silver-coated gold nanorods. Nano Lett., 8, 1719-1723 (2008)
Becker J., Zins I., Jakab A., Khalavka Y., Schubert O. and Sönnichsen C.
- Protein-membrane interaction probed by single plasmonic nanoparticles. Nano Lett., 8, 1724-1728 (2008)
Baciu C. L., Becker J., Janshoff A. and Sönnichsen C.
- Light-Controlled One-Sided Growth of Large Plasmonic Gold Domains on Quantum Rods Observed on the Single Particle Level. Nano Lett., 9, 3710-3714 (2009)
Carbone L., Jakab A., Khalavka Y. and Sönnichsen C.
- Rotational Dynamics of Laterally Frozen Nanoparticles Specifically Attached to Biomembranes. J. Phys. Chem. C, 113, 11179-11183 (2009)
Pierrat S., Hartinger E., Faiss S., Janshoff A. and Sönnichsen C.
- Synthesis of Rod-Shaped Gold Nanorattles with Improved Plasmon Sensitivity and Catalytic Activity. J. Am. Chem. Soc., 131, 1871-1875 (2009)
Khalavka Y., Becker J. and Sönnichsen C.
