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The quest for novel quantum properties of devices has spurred a growing effort in pushing the materials¡¯ size down to nanometer scale or even use single molecules as functional components. Similar to single molecules, metal nanoparticles also have rich electronic structures because when their size reduced to a few nanometers, the quasi-continuous density of state is replaced by a discrete energy level structures. We try to manipulate the electronic structures of molecules and nanoparticles by controlling of size, doping, ordering and bond chemistry. Quantum transport properties were studied and their electronic structures were determined from the results of STM combined with the theoretical modeling. Novel effects associated with the discrete energy levels and the charging energy of ultra small tunneling junction, like negative differential resistance(NDR), rectifying and Kondo effects in single molecules, co-tunneling between nanoparticles and coupling in single electron tunneling and discrete energy level effect are reported. |