Localized surface plasmon resonance (LSPR) arising from free carriers in doped metal oxide nanocrystals (NCs) has attracted abundant attention in the past decade for its massive potential in applications such as electrochromics, sensing, and photothermal therapy. Other than depending upon the carrier concentration and carrier damping in NCs, surface depletion effects, which insulate free charge carriers from the surrounding environment, can also influence LSPR. While a lot is already known about LSPR of doped metal oxide NCs, there is still much to learn about the effect of dopant identity on the electronic structure of the host and, in particular, the effect on surface depletion layers. Here, using indium oxide as the host lattice, we discuss the contribution of a dopant to the electronic structure and rationalize an empirical understanding on how a particular dopant could impact the surface depletion effects, carrier concentration and, carrier damping in doped metal oxide NCs. To do this, we leverage a slow injection synthesis to incorporate four different dopants (Sn, Zr, Ti, and Ce) in indium oxide NCs. For each dopant, we synthesized NCs with different diameters but similar nominal doping level (~1 at%) and measured the optical response of a dilute dispersion. By fitting their plasmonic response to the heterogeneous ensemble Drude approximation, we extracted single NC properties such as carrier concentration, carrier damping, and surface depletion layer thickness and justified the influence of a dopant on each parameter. Furthermore, by measuring the extinction coefficients, we investigate how the efficiency of a NC to absorb radiation can be influenced by a particular dopant. This study will probably fill crucial information gaps in understanding the LSPR of doped metal oxide NCs at the fundamental level and facilitate their implementation in different applications.

Influence of dopant on surface depletion and extinction coefficients in doped metal oxide nanocrystals

ACS Spring Meeting 2021

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