A multi-responsive intrinsically disordered protein (IDP)-directed green synthesis of fluorescent gold nanoclusters

Herein we demonstrate the green synthesis of fluorescent gold nanoclusters (AuNCs) using a multi-responsive intrinsically disordered protein (IDP) polymer, Rec1-resilin, as a multi-functional template. In a controlled environment, Rec1-resilin acts simultaneously as the directing agent and the reducer, and performs the role of a highly efficient stabilizer once AuNCs are formed. The evolution of the photophysical properties and the chemical states of AuNCs formed are measured using UV-Vis, fluorescence and X-ray photoelectron spectroscopy. Circular dichroism (CD) spectroscopy measures the intrinsically disordered nature of Rec1-resilin stabilizing AuNCs. High resolution transmission electron microscopy (HR-TEM) reveals the detailed structure and morphology of the generated AuNCs of <1.5 nm size. A local ordering resembling that of a face-centered cubic (FCC) structure with evidence of twinning was observed for the generated AuNCs. The AuNCs so formed exclude the use of toxic reducing agents and display excellent water dispersibility, photostability and environmental stability towards aggregation.