Monolayer-protected nanoclusters (MPCs) are an emerging class of inorganic nanomaterials that can be synthesized and isolated with atomic precision. Control over MPC composition results, in part, from electron filling of Superatom orbitals,  yielding colloidal metal nanoparticles of specific magic sizes. These synthetic advances overcome many limitations of inherently heterogeneous colloidal metal nanoparticle syntheses. Recently, post-synthetic electrochemical methods for manipulating the oxidation state of stable MPCs have been demonstrated. Here, femtosecond time-resolved and magneto-optical spectroscopy studies of a family of MPCs in the 1-2 nm size range will be presented. These results show that the optical, electronic and magnetic properties of MPCs are extremely sensitive to the electronic configuration of Superatom orbitals. For example, the magnetic properties of Au<sub>25</sub>(SR)<sub>18</sub>, where SR represents an alkanethiol, can be switched reversibly by oxidative opening of the eight-electron Superatom P orbital. Collective interactions between assembled MPCs also exhibit spin-dependent magnetic phenomena not present in the isolated building blocks. Magnetic Circular Dichroism and time-dependent spectroscopy on dimerized 20-atom MPCs reveal inter-particle spin-dependent dynamics not observed for the monomer. Importantly, these results indicate that the magnetic properties of gold MPCs result from the electronic configuration of metal-based Superatom orbitals.

Monolayer-protected nanoclusters: Structurally precise building blocks for spintronic applications

249th National Meeting (2015)

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