Metal nanoparticles with subnanometer core dimensions are of interest for fundamental studies and may be useful as building blocks for nanoscale devices because they are small enough to possess discrete electronic states and can exhibit semiconductor-like electronic properties. To date, such nanoparticles have not been exploited due in part to the lack of convenient access to ligand-stabilized nanoparticles possessing terminal functional groups.
University of Oregon Professor James E. Hutchison and Gerd H. Woehrle (Eugene, OR) have demonstrated the ligand exchange chemistry of phosphine-stabilized Au-11 clusters with .omega.-functionalized thiols is a powerful synthetic method that provides convenient access to a diverse family of functionalized Au-11 clusters. The general nature of the ligand exchange approach, in combination with the ease preparation, makes this approach of broad utility. The approach is general and shows the high tolerance for a wide variety of functional groups. Mechanistic studies provided conclusive evidence that the Au-11 core of the precursor particle remains intact during ligand exchange and showed that the ligand exchange of these particles follows a different pathway than for ligand exchanges of larger gold nanoparticles such as "Au101(PPh3)21Cl5." Optical studies of the products show a strong dependence on the nature of the stabilizing thiol ligands.
The ligand exchange approach developed by Hutchison and Woehrle is general and tolerates a surprisingly wide range of functional groups, using either a mono- or bi-phasic system. The approach produces functionalized Au-11 particles with technologically relevant head groups such as alcohols for biological applications, phosphonic acids and silanes for surface applications, and quaternary ammonium head groups for self-assembly on DNA templates, making this method useful for the construction of many different conjugates. In addition, the general nature of the approach, in combination with the ease of preparation and convenient purification, allows for the rapid preparation of large families of thiol-stabilized Au-11 particles, according to U.S. Patent Application 20090312565
Undecagold (Au11) is smaller than Nanogold®, with a core of 11 gold atoms only 0.8 nm in diameter. Hutchison and Woehrle developed novel undecagold nanoparticles, methods for making such particles and application of their optical properties.
The application reveals a convenient and general approach for the rapid preparation of large families of thiol-stabilized, subnanometer (dCORE.about.0.8 nm) particles. The approach permits rapid incorporation of specific functionality into the stabilizing ligand shell, is tolerant of a wide range of functional groups, and provides convenient access to new materials inaccessible by other methods.
Hutchison and Woehrle also created novel nanoparticles. The nanoparticles prepared as described have useful optical properties. The properties of the thiol-stabilized nanoparticles depend strongly on the composition of the ligand shell. The optical properties of the nanoparticles can be tuned by altering the ligand shell composition. Such tuning can be accomplished in principle by affecting the electronic structure of the particle core and/or effecting a structural change within the nanoparticle core. Typically the properties are affected via the electronic structure of the core.
Hutchison and Woehrle also created novel nanoparticles. The nanoparticles prepared as described have useful optical properties. The properties of the thiol-stabilized nanoparticles depend strongly on the composition of the ligand shell. The optical properties of the nanoparticles can be tuned by altering the ligand shell composition. Such tuning can be accomplished in principle by affecting the electronic structure of the particle core and/or effecting a structural change within the nanoparticle core. Typically the properties are affected via the electronic structure of the core.
