(28d) How Particle Geometry Controls the Properties and Assembly of Nanoobjects

While there has been significant progress in controlling the size, shape and properties of nanomaterials, their controlled assembly into nanostrucutres remains a significant challenge.  To date, many nanoparticles (NPs) of unusual shapes have been reported - but the influence of geometry on the surface chemistry of these particles remains a mystery. We recently found that the pK_a of carboxylic acids bound to the surface of NPs deviates drastically compared to the values for free ligands in solution. This deviation can be described by the coupling the acid/base chemical equilibrium taking place at the particle surface with the surrounding electrostatic environment. Interestingly, by controlling the NP geometry, one can control how charges are distributed on the surface of NPs as well as other chemical properties (such as shifts in redox potentials). The gradients in chemical properties across particle surfaces can be exploited to create higher order structures which would not be possible without the influence of externals forces (such as the use of electronic or magnetic fields). A mixture of experimental and theoretical results will be presented.