Switching between Plasmonic and Fluorescent Copper Sulfide Nanocrystals

Control over the doping density in copper sulfide nanocrystals is of great importance and determines its use in optoelectronic applications such as NIR optical switches and photovoltaic devices. Here, we demonstrate that we can reversibly control the hole carrier density (varying from >10²² cm^–3 to intrinsic) in copper sulfide nanocrystals by electrochemical methods. We can control the type of charge injection, i.e., capacitive charging or ion intercalation, via the choice of the charge compensating cation (e.g., ammonium salts vs Li⁺). Further, the type of intercalating ion determines whether the charge injection is fully reversible (for Li⁺) or leads to permanent changes in doping density (for Cu⁺). Using fully reversible lithium intercalation allows us to switch between thin films of covellite CuS NCs (E_g = 2.0 eV, hole density 10²² cm^–3, strong localized surface plasmon resonance) and low-chalcocite CuLiS NCs (E_g = 1.2 eV, intrinsic, no localized surface plasmon resonance), and back. Electrochemical Cu⁺ ion intercalation leads to a permanent phase transition to intrinsic low-chalcocite Cu₂S nanocrystals that display air stable fluorescence, centered around 1050 nm (fwhm ∼145 meV, PLQY ca. 1.8%), which is the first observation of narrow near-infrared fluorescence for copper sulfide nanocrystals. The dynamic control over the hole doping density and fluorescence of copper sulfide nanocrystals presented in this work and the ability to switch between plasmonic and fluorescent semiconductor nanocrystals might lead to their successful implementation into photovoltaic devices, NIR optical switches and smart windows.

Diversified copper sulfide (Cu2-xS) micro-/nanostructures: a comprehensive review on synthesis, modifications and applications

As a significant metal chalcogenide, copper sulfide (Cu_2-xS, 0 < x < 1), with a unique semiconducting and nontoxic nature, has received significant attention over the past few decades. Extensive investigations have been employed to the various Cu_2-xS micro-/nanostructures owing to their excellent optoelectronic behavior, potential thermoelectric properties, and promising biomedical applications. As a result, micro-/nanostructured Cu_2-xS with well-controlled morphologies, sizes, crystalline phases, and compositions have been rationally synthesized and applied in the fields of photocatalysis, energy conversion, in vitro biosensing, and in vivo imaging and therapy. However, a comprehensive review on diversified Cu_2-xS micro-/nanostructures is still lacking; therefore, there is an imperative need to thoroughly highlight the new advances made in function-directed Cu_2-xS-based nanocomposites. In this review, we have summarized the important progress made in the diversified Cu_2-xS micro-/nanostructures, including that in the synthetic strategies for the preparation of 0D, 1D, 2D, and 3D micro-/nanostructures (including polyhedral, hierarchical, hollow architectures, and superlattices) and in the development of modified Cu_2-xS-based composites for enhanced performance, as well as their various applications. Furthermore, the present issues and promising research directions are briefly discussed.

Synthesis of ZnS/CuS nanospheres loaded on reduced graphene oxide as high-performance photocatalysts under simulated sunlight irradiation

Schematic descriptions for the formation of ZnS/CuS–rGO nanocomposites and their excellent photocatalytic performance.

Plasmon Enhanced Direct Bandgap Emissions in Cu7 S4 @Au2 S@Au Nanorings

Nanostructured copper sulfides, promising earth-abundant p-type semiconductors, have found applications in a wide range of fields due to their versatility, tunable low bandgap, and environmental sustainability. The synthesis of hexagonal Cu₇ S₄ @Au₂ S@Au nanorings exhibiting plasmon enhanced emissions at the direct bandgap is reported. The synthesized Cu₇ S₄ @Au₂ S@Au nanorings show greatly enhanced absorption and emission by local plasmons compared to pure copper sulfide nanoparticles.

A solid-state approach to fabricate a CdS/CuS nano-heterojunction with promoted visible-light photocatalytic H2-evolution activity

CdS/CuS nano-heterojunction composites were synthesized by the solid-state strategy and exhibited the enhanced visible-light photocatalytic H₂-evolution activity.

Facile polyol synthesis of CuS nanocrystals with a hierarchical nanoplate structure and their application for electrocatalysis and photocatalysis

The article describes a robust method for the facile polyol synthesis of high-quality CuS nanocrystals with a controlled hierarchical nanoplate structure.

Ultrafast mechanochemical synthesis of copper sulfides

Covellite, CuS and chalcocite, Cu₂S were prepared within a few seconds by ball milling of the elemental precursors.

Synthesis of porous Cu7.2S4 sub-microspheres by an ion exchange method for high-performance supercapacitors

The porous Cu_7.2S₄ sub-microspheres were synthesized by an ion exchange reaction and their electrochemical supercapacitor properties were investigated in 6 M aqueous KOH solution.