Electrostatic\nAssembly of Gold Nanoclusters in Reverse\nEmulsion Enabling Nanoassemblies with Tunable Structure and Size for\nEnhanced NIR-II Fluorescence Imaging

The\nprecise control of the assembly structure and size of gold\nnanoclusters (AuNCs) can potentially amplify their near-infrared II\n(NIR-II) fluorescence imaging and targeting properties. However, the\nconventional electrostatic assembly of AuNCs and charged molecules\nfaces challenges in balancing the inherent electrostatic repulsions\namong charged units and regulating the diffusion of assembly units.\nThese difficulties limit precise control over assembly size and structure,\nalong with limited options for coassembled molecules, thereby restricting\nimaging properties and targeting capability. To circumvent this challenge,\nwe developed a reverse emulsion-confined electrostatic assembly method.\nThis technique efficiently constructs AuNC nanoassemblies with diverse\ncoassembled molecules, allowing for the fine-tuning of assembly size\nand structure, including both core–satellite and homogeneous\nAuNC nanoassemblies. The development of two distinct nanoassemblies\ncan be partially attributed to the varying diffusive rates of AuNCs\nor the AuNCs/polymer complex within the fused emulsion droplets. This\nvariance arises from steric hindrances encountered during the emulsion\nfusion process. Interestingly, core–satellite nanoassemblies\nexhibit the strongest NIR-II fluorescence enhancement. Finally, the\nintroduction of a hyaluronic acid coating on the surfaces of nanoassemblies\nwith varying sizes enables the nanoprobes to achieve enhanced lymph\nnode imaging through size modulation and macrophage targeting, which\nare used for surgical navigation to remove lymph node metastases.\nWe envision that this self-assembly strategy can be extended to a\nwide range of electrostatic assembly systems for the development of\nmulticomponent functional materials.