Plasmon Modulation in Copper Phosphide Nanocrystals

We present the modulation of surface plasmon resonance in non-stoichiometric copper phosphide nanocrystals. This was achieved through control over the carrier concentration by an applied electrochemical potential. Application of anodic potential resulted in the blueshift of the plasmon resonance and increment in its extinction. Under cathodic potential, the plasmon redshifted and reduced the extinction. Further, these changes were reversible over multiple cycles of anodic and cathodic potential steps. We also discuss how the post synthetic ligand treatment can impact the plasmon peak and structure of Cu3−xP nanocrystals . Specifically, the treatment of thiols resulted in the decomposition of the nanocrystal. This work demonstrates how plasmon peak in Cu3−xP can be used as a probe to visualize the changes in the structure and carrier density of these nanocrystals in various applications.