Computation-Motivated Design of Ternary Plasmonic Copper Chalcogenide Nanocrystals

Nanocrystals composed of copper(II) sulfide (CuS), a degenerately doped semiconductor with a direct optical bandgap, have been observed to exhibit both visible wavelength excitonic emission and strong localized surface plasmon resonances (LSPRs) in the near-infrared, making them prime candidates for exploring phenomena such as coupled light–matter interactions, quantum entanglement, and optical nonlinearity. Here, we report a computation-motivated synthetic approach for modulating the optical bandgap energy of plasmonic nanocrystals relative to their LSPR energies by tuning the composition of alloyed CuSexS1–x nanocrystals. CuSexS1–x alloys are examined by first-principles density functional theory (DFT) to understand the effects of composition tuning on the electronic and optical properties of CuSexS1–x, using high-throughput methods to probe Se occupation within a parent CuS unit cell. Results from this DFT analysis are used as input parameters for predicting the LSPR of CuSexS1–x nanostructures. To validate these DFT results against experimental observations, we synthesize CuSexS1–x using CuS nanodisks as a template for a novel anion-exchange protocol. Optical characterization reveals qualitative agreement between our experimental and predicted materials properties, and we discuss how quantitative deviations from our predicted values are likely the result of interfacial and morphological characteristics that are unaccounted for in DFT models.