A novel dual-switch fluorescent probe for Cr(iii) ion based on PET–FRET processes?

Analyst Pub Date: 2014-05-02 DOI: 10.1039/C4AN00303A

Abstract

Two different strategies for photoinduced electron transfer (PET) and fluorescence resonance energy transfer (FRET) have been designed and combined into one sensing system. The novel probe NNRhB was developed based on 1,8-naphthalimide and rhodamine moieties, in which two fluorophores are sensitive to the presence of Cr3+ in different chromium ion concentration regimens. Therefore, the proposed sensing system represents dual-switch states and segmented detection behavior, with the fluorescence emission color spans from green to orange over an increasing Cr3+ concentration gradient. When excited in the visible region, the initial emission band at 537 nm was enhanced. That was attributed to the suppression of the PET process, which arose from Cr3+-coordination with a 1,8-naphthalimide derivative. At a sufficiently high concentration of Cr3+ (over 9 μM), the spirolactam rhodamine component in NNRhB converted to the opened form as a result of Cr3+ coordination, which turned the emission color from green to orange via FRET. The fluorescence phenomena of the compound 1 and compound 2 split from compound NNRhB confirm our hypothesis of the spectral response mechanisms. Moreover, compared with a single fluorescent response in compound 1 or compound 2, the dual-switch fluorescent probe NNRhB shows a more sensitive and distinct visual detection ability for Cr3+ ions. This probe affords a high selectivity and sensitivity to Cr3+ from 30 nM to 80 μM; the detection limit was 0.14 nM. The results of practical application experiments suggest that the Cr3+-selective ligand prepared here may provide an effective strategy for detection of Cr3+ in environmental and biological applications.

Graphical abstract: A novel dual-switch fluorescent probe for Cr(iii) ion based on PET–FRET processes
Recommended Literature