Modulating the spectroscopic signatures of gold nanoclusters: The role of hydrophobicity of bile salts

Deciphering the role of hydrophobicity of the capping ligands on the development of luminescent Metal Nanoclusters (MNCs) is a longstanding endeavor and demands more comprehensive scientific investigations. Hence, our attempts have been directed to explore this scarcely reported fact by adopting the rather non-conventional top-down approach for the development of MNCs. Herein, we are reporting the synthesis of the highly stable Cysteamine-templated gold nanoclusters (AuNCs) with different photophysical properties from the core etching of bile salts-templated Metal Nanoparticles (MNPs). Herein, we have used three different bile salts (sodium cholate, NaC; sodium taurocholate, NaTC; and sodium deoxycholate, NaDC) with varying hydrophobicity index. The role of hydrophobicity of the bile salts (NaDC > NaC > NaTC) had a profound influence on the synthesis of the AuNPs, as well as in the synthesis of AuNCs by the core etching of different AuNPs. It was observed that the core etching of these three AuNPs, templated by NaC (NP1), NaDC (NP2), and NaTC (NP3) with a common etching agent cysteamine, leads to the formation of three AuNCs (Cystm@AuNC1 derived from NP1, Cystm@AuNC2 derived from NP2, and Cystm@AuNC3 derived from NP3) characterized by different photophysical signatures.