Enhanced Water Dispersibility of Discrete Chalcogenide Nanoclusters with a Sodalite-Net Loose-Packing Pattern in a Crystal Lattice.

Good aqueous dispersibility of metal chalcogenide nanoclusters with an atomically precise structure is desirable to achieve tiny and uniform cluster-based "quantum dots". However, there are big challenges toward this goal, especially for the large-sized nanoclusters without covalently bonded organic ligands, because the strong electrostatic interactions between closely packed negatively charged nanoclusters and protonated organic amine templates in the crystal lattice impede the dispersion of cluster-based bulk crystalline samples. Here, we report two iso-structured crystalline metal chalcogenides composed of discrete supertetrahedral T4-MInS nanoclusters with the formulas of [M4In16S35]14- (denoted ISC-16-MInS, M = Zn and Fe), which adopt a sodalite-net loose-packing pattern in the crystal lattice and display superior dispersibility in water and some organic solvents as compared to other cases composed of the same type of nanoclusters with close-packing pattern. The dispersed T4-MInS nanoclusters were unexpectedly stabilized by adsorbing a certain number of H+ ions on surface S sites and simultaneously dropping partial surface S2- ions, instead of being surrounded by protonated organic amines, which was clearly verified by electrospray ionization mass spectrometry analysis. Notably, ISC-16-ZnInS behaves with superior performance on photodegradation of rhodamine B dye to ISC-16-FeInS. This is attributed to their difference in divalent-metal-directed separation efficiency of the photogenerated electrons and holes. This work holds great promise for the potential functional applications of uniformly dispersed semiconductor nanoclusters, such as cluster-based thin film devices, photoelectrodes, and photocatalysis.