Engineering Plasmon-Enhanced Fluorescent Gold Nanoclusters Using Bovine Serum Albumin as a Novel Separation Layer for Improved Selectivity.

The combination of gold nanoclusters (AuNCs) with surface plasmonic metal nanomaterials is an effective and direct method to improve the photoluminescence efficiency of AuNCs. However, the plasmon-enhanced AuNC luminescence strategies usually utilize silica as the separation layer, which requires further functionalization because the silica layer has no functional groups for in situ bonding of AuNCs. Therefore, it appears as a crucial need to develop an appropriate separation layer for the preparation of plasmon-enhanced AuNC luminescent nanomaterials. In this work, employing bovine serum albumin (BSA) as a novel separation layer, we prepared gold nanoparticles (AuNPs)@BSA@AuNCs by a controllable and in situ synthesis method. BSA can form a BSA layer on the surface of AuNPs through Au-S bonds. Meanwhile, BSA can reduce AuCl ions to generate AuNCs. In comparison with pure BSA-AuNCs, the quantum yield of the AuNPs@BSA@AuNCs was increased by nearly 7 times as a result of plasmonic coupling, and the time of in situ synthesis of AuNCs was shortened by 8 h. More importantly, the preparation of the BSA layer was simple and time-saving without functionalization, in contrast to the previously reported silica layer. Moreover, the simulation calculation of different dimensions determined the optimal binding sites between AuNCs and BSA, confirming that BSA can be an effective spatial spacer. Finally, it was found that the BSA layer between AuNPs and AuNCs can improve the specificity of AuNCs toward HS, which is extremely difficult for pure BSA@AuNCs.