Selective Cation Incorporation into Copper Sulfide Based Nanoheterostructures

Heterogeneous copper sulfide based nanostructures have attracted intense attention based on their potential to combine the plasmonic properties of copper-deficient copper sulfides with properties of other semiconductors and metals. In general, copper sulfides are versatile platforms for production of other materials by cation incorporation and exchange processes. However, the outcomes of subsequent cation exchange (CE) or incorporation processes involving nanoheterostructure (NH) templates have not been explored. In this work, we incorporate indium and tin into Cu_1.81S–ZnS NHs. We demonstrate that the outcomes of cation incorporation are strongly influenced by heterocation identity and valence and by the presence of a Cu-extracting agent. The selectivity of cation incorporation depends upon both the cation itself and the heterodomains in which CE reactions take place. The final nanocrystals (NCs) emerge in many forms including homogeneous NCs, heterodimers, core@shell NHs and NHs with three different domains. This selective cation incorporation not only facilitates the preparation of previously unavailable metal sulfide NHs but also provides insight into mechanisms of CE reactions

Room-Temperature Synthesis of Covellite Nanoplatelets with Broadly Tunable Localized Surface Plasmon Resonance

Preparation of nanomaterials with controllable sizes and shapes at ambient conditions, without heating or cooling, is extremely attractive from the perspective of cost and energy efficiency. However, highly reactive precursors must be used to obtain NCs at ambient conditions, and this can make the control of particle formation extremely challenging. Degenerately p-doped copper sulfide NCs have attracted much recent interest based on the observation of localized surface plasmon resonance (LSPR) in these materials. These earth-abundant semiconductor NCs have potential applications ranging from photovoltaics to biomedical imaging. Here, we provide the first report of ambient-temperature preparation of covellite nanoplatelets. The lateral dimensions of these are controllable over a wide range while maintaining a constant thickness of 4 nm. The crystalline phase of the NCs is shown here to be controlled by the oxidation state of the copper reagent, with a Cu­(II) precursor required to prepare phase-pure covellite NCs. The NCs exhibit LSPR absorbance that depends upon their aspect ratio (their lateral dimension, at fixed thickness) and can be tuned over a range of more than 600 nm. Their optical absorbance was modeled quantitatively to extract consistent values of free carrier concentration and background polarizability that apply over a wide range of NC sizes

Au–Cu_2–<i>x</i>Se Heterodimer Nanoparticles with Broad Localized Surface Plasmon Resonance as Contrast Agents for Deep Tissue Imaging

We report a new type of heterogeneous nanoparticles (NPs) composed of a heavily doped semiconductor domain (Cu_2–<i>x</i>Se) and a metal domain (Au), which exhibit a broad localized surface plasmon resonance (LSPR) across visible and near-infrared (NIR) wavelengths, arising from interactions between the two nanocrystal domains. We demonstrate both in vivo photoacoustic imaging and in vitro dark field imaging, using the broad LSPR in Cu_2–<i>x</i>Se–Au hybrid NPs to achieve contrast at different wavelengths. The high photoacoustic imaging depth achieved, up to 17 mm, shows that these novel contrast agents could be clinically relevant. More broadly, this work demonstrates a new strategy for tuning LSPR absorbance by engineering the density of free charge carriers in two interacting domains