Lysozyme protected copper nano-cluster: A photo-switch for the selective sensing of Fe2+

Protein capped metal nanoclusters gained a lot of recent attention due to their wide range of applications. However copper nanoclusters are difficult to synthesize due to their tendency to undergo oxidation. Here we successfully synthesized a stable, biocompatible lysozyme protected Cu nanocluster (Lys-Cu NC) using an optimized green one-pot protocol under aqueous condition at room temperature. The nanocluster showed a strong photoluminescence intensity (λex = 365 nm, λem = 430 nm) which can be significantly and selectively quenched (off) by Fe2+ ions. Upon addition of NaOH the initial photoluminescence intensity can be recovered completely (on) thereby making the nanocluster a suitable candidate for a photo switch that can be reliably reused for the selective and sensitive detection of Fe2+ ions in the nanomolar (detection limit ∼ 2.5 nM) concentration range. The synthesized nanocluster further has been successfully used to rapidly estimate iron level in complex systems such as ground water and human hemoglobin samples. The photoluminescence intensity of the nanocluster is also sensitive towards temperature indicating that it can be used as a temperature sensor in different biological systems. The nanocluster further used as an excellent nanoprobe for in-vivo cell imaging studies. Thus this Lys-Cu NC can be emerged as a next generation novel nanoprobe for various interdisciplinary applications.