Polymer surface ligand and silica coating induced highly stable perovskite nanocrystals with enhanced aqueous fluorescence for efficient Hg2+ and glutathione detection

Abstract

The poor stability and aqueous-quenching of fluorescence of perovskite nanocrystals (NCs) hinder their application in bio-detection and bio-imaging. Herein, through the synergistic effects of polymer surface ligand and silica encapsulation, highly stable and enhanced aqueous fluorescent CsPbBr₃-mPEG@SiO₂ NCs were synthesized and used as a novel “on–off–on” fluorescent probe for highly sensitive and selective detection of mercury ions (Hg²⁺) and glutathione (GSH) in aqueous solutions. The effects of the methoxypolyethylene glycol amine (mPEG-NH₂) ligand and silica encapsulation on the stability and aqueous fluorescence of the CsPbBr₃ NCs were studied. It indicated that the aqueous fluorescence of perovskite NCs was increased by 2.59 times. The water stability was also greatly improved, with the NCs maintaining 73% of their original fluorescence after storage for 30 days in water. X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analyses further demonstrated that the NCs were successfully passivated by mPEG-NH₂ and silica. The fluorescence of the CsPbBr₃-mPEG@SiO₂ nanocrystals was effectively quenched by Hg²⁺ which is attributed to the electron transfer process between NCs and Hg²⁺. Then, through the interaction between Hg²⁺ and GSH, the restoration of fluorescence for CsPbBr₃-mPEG@SiO₂ was realized. The “on–off–on” fluorescent probe can be used for the detection of Hg²⁺ and GSH with a low detection limit of 0.08 nM and 0.19 μM, respectively. It also shows a fast response time and high accuracy for practical sample detection. The simple and sensitive fluorescent probe of CsPbBr₃-mPEG@SiO₂ shows great potential in environmental and biological sensing.