Spectroscopic investigations of the changes in ligand conformation during the synthesis of soy protein-templated fluorescent gold nanoclusters

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2021-07, Vol.255, p.119725, Article 119725
• Main Authors: Cheng, Yuliang, Chen, Jiannan, Hu, Bin, Pi, Fuwei, Yu, Hang, Guo, Yahui, Xie, Yunfei, Yao, Weirong, Qian, He
• Format: Article
• Language: English
• Subjects: Conformational changes; Correlation analysis; Fluorescence; Gold nanoclusters; Soy protein
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2021.119725

[Display omitted] •Ligand’s conformational changes during the synthesis of SP-AuNCs were investigated.•The fluorescence intensity was dominated by the Au nucleus in early phases.•An ordered-disordered-ordered structure transition happened to the ligand.•The growth of Au core and LMCT caused the structural changes of protein ligand. In this paper, the potential relationship between fluorescence and changes in the ligand conformation observed during the synthesis of soy protein-templated fluorescent gold nanoclusters (SP-AuNCs) was studied using a series of spectroscopic techniques. The results show that the determinants of the fluorescence effect in SP-AuNCs changed with the reaction time during the synthesis process. In the early stage of the reaction (within 60 min), the fluorescence intensity was dominated by the Au nucleus, followed by the combination of the Au nucleus and protein ligand. The structure of the protein ligand also underwent a transition from ordered to disordered to ordered. At the same time, its role in the reaction also changed from providing the reducing power to protecting the Au nucleus and contributing to the transition of the fluorescence effect in the AuNCs via ligand-to-metal charge transfer (LMCT). Using two-dimensional (2D) photon spectra correlation analysis, the formation and growth of the Au nuclei and the LMCT effect observed during the synthesis of the SP-AuNCs were found to be the major causes for the changes in the conformation of the protein ligand. Our results are an important discovery and can be used to explain the mechanism of protein ligands in the synthesis of gold nanoclusters.