Flexible tuning of hole-based localized surface plasmon resonance in roxbyite Cu1.8S nanodisks via particle size, carrier density and plasmon coupling

Semiconductor nanocrystals (NCs) heavily doped with cation/anion vacancies or foreign metal ions can support localized surface plasmon resonance (LSPR) in the near-infrared (NIR) and mid-infrared (MIR) spectral wavelengths. Typically, nonstoichiometric copper sulfide Cu2-xS NCs with different x values (0 < x <= 1) have attracted numerous attention because of hole-based, particle size, morphology, hole density and crystal phase-dependent LSPR. In spite of excited development of methodology for LSPR manipulation, systematic LSPR tuning of Cu2-xS NCs with a special crystal phase has been limited. Herein, roxbyite Cu1.8S nanodisks (NDs) were selected as a model and their LSPR was readily tuned by particle size, hole density via chemical oxidation and reduction, self-assembly and disassembly in solution and plasmon coupling in multilayer films. Particle size, hole density and plasmon coupling severely affect their LSPR peak position and absorption intensity. Therefore, the ability of flexible LSPR tuning gifts roxbyite Cu1.8S NDs great potential in plasmonic applications, including photocatalysis, photothermal agent, two-photon photochemistry and many others in NIR and MIR regions.