Copper sulfides represent a broad range of chemical compounds, including naturally
occurring minerals and wet-chemically synthesized nanoparticles. Tailoring the size,
shape, and chemical composition of Cu2-x S nanoparticles enables the tuning of their
optical and electronic properties allowing the switch between semiconducting and plasmonic
characteristics. While the sulfidation of metals and metal oxides can even occur spontaneously
under ambient storage conditions, the targeted synthesis of Cu2-x S nanoparticles
mostly relies on the use of inorganic sulfur compounds. Inspired by the natural sulfidation
reactions, a novel approach is developed in this paper to transform sacrificial Cu2O
nanooctahedra by a short-chain organic thiol (beta-mercaptoethanol) into spherical
Cu2S superstructures consisting of phase-pure Cu2S quantum dots. The optical and photoelectrochemical
properties are thoroughly investigated and supplemented by advanced electron microscopy
analysis to identify the phase of the superstructure building blocks. Structural and
surface analyses reveal that the superstructures are composed of small (4-5 nm) Cu2S
quantum dots spatially separated by a thin amorphous ligand layer. The results highlight
the dual role of beta-mercaptoethanol serving both as a sulfur source and as a stabilizing
ligand upon superstructure formation. To synthesize semiconductor/metal multicomponent
nanostructures, the surface of the superstructures is decorated with Au nanograins
initiated by the photoreduction of aqueous Au3+ ions. Upon the fabrication of working
electrodes from the developed superstructures, the p-type nature of the Cu2S is demonstrated
by open-circuit potentiometry. Superstructures supply negative photocurrent under
UV irradiation, which can be further enhanced by the presence of Au nanograins. Using
the developed synthetic method, phase-pure photofunctional nanomaterials can be prepared
by the sulfidation of cuprous oxide in a controlled manner.
