Rendering hydrophobic nanoclusters water-soluble and biocompatible

Abstract

Hydrophobic and hydrophilic nanoclusters embody complementary superiorities. The means to amalgamate these superiorities, i.e., the atomic precision of hydrophobic clusters and the water dissolvability of hydrophilic clusters, remains challenging. This work presents a versatile strategy to render hydrophobic nanoclusters water-soluble—the micellization of nanoclusters in the presence of solvent-conjoined Na⁺ cations—which overcomes the above major challenge. Specifically, although [Ag₂₉(SSR)₁₂(PPh₃)₄]³⁻ nanoclusters are absolutely hydrophobic, they show good dissolvability in aqueous solution in the presence of solvent-conjoined Na⁺ cations (Na₁(NMP)₅ or Na₃(DMF)₁₂). Such cations act as both counterions of these nanoclusters and surface cosolvent of cluster-based micelles in the aqueous phase. A combination of DLS (dynamic light scattering) and aberration-corrected HAADF-STEM (high angle annular dark field detector scanning transmission electron microscopy) measurements unambiguously shows that the phase-transfer of hydrophobic Ag₂₉ into water is triggered by the micellization of nanoclusters. Owing to the excellent water solubility and stability of [Ag₂₉(SSR)₁₂(PPh₃)₄]³⁻[Na₁(NMP)₅]₃⁺ in H₂O, its performance in cell staining has been evaluated. Furthermore, the general applicability of the micellization strategy has been verified. Overall, this work presents a convenient and efficient approach for the preparation of cluster-based, biocompatible nanomaterials.