A General Theoretical Framework for Characterizing Solvated Electronic Structure via Voltammetry: Applied to Carbon Nanotubes

5 years ago

A General Theoretical Framework for Characterizing Solvated Electronic Structure via Voltammetry: Applied to Carbon Nanotubes

Md. Sazzad Hossain, Kirk H. Bevan, Bhaskaran Muralidharan

In this work, we propose a general theoretical framework for multiple electron transfer to solvated nanoparticles and their characterization via linear sweep voltammetry. A direct connection is made between the peak potentials observed in voltammograms and the electronic structure of solvated particles. Two major contributions to the voltammogram extracted electronic structure properties are established to be the quantization of electron kinetic levels (ε^T) and the single electron charging cost (U), both of which display a significant variation with nanoparticle dimensionality. The dimensional dependences of these energetics is reflected in the spacings between voltammetric current peaks. The simultaneous role played by U (typically associated with Coulomb blockade) and ε^T at all dimensions advances our understanding of their relative contributions in the so-called molecular redox charging regime and the nanoparticle charging regime. These general physical properties are investigated in a model solvated “particle-in-a-box” system, consisting of finite length armchair semiconducting carbon nanotubes. While implemented within a model system, the physics underlying these energetics are expected to be general to all solvated species. However, the scan rate dependence of the peak potentials in voltammetry under a considerable reorganization energy (λ) complicates direct correlations between redox-active energetics and peak spacing features. We argue that this scan rate dependence can be resolved by ultrafast voltammetry. Through combined ultrafast and conventional voltammetry, the solvated electronic structure contributions of reactants (including ε^T, U and λ) should be accessible (as shown in the model system). The proposed solvated electronic structure physics and voltammetric extraction technique is general in scope and should be executable on any solvated nanomaterial system participating in heterogeneous outer-sphere reactions.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b05753

DOI: 10.1021/acs.jpcc.7b05753