A dual-channel chemosensor based on rhodamine and BODIPY conjugated dyad for ratiometric detection of Hg2+ and fluorescence on-off recognition of Cu2+ in aqueous solution and living cells

A novel probe RB for discriminative detection of Hg2+ and Cu2+ constructed by rhodamine and BODIPY was designed and synthesized. Probe RB consists of three parts: BODIPY as the energy donor, rhodamine as the energy receptor, and thiosemicarbazide as the reacting site. Probe RB selectively binds with Hg2+ and Cu2+ ions in in EtOH/H2O (V/V = 1:1) among tested metal ions. Probe RB exhibited a fluorescence red shift from 513 to 593 nm for Hg2+ and a fluorescence quenching for Cu2+. The mechanism study showed that the fluorescence changes of probe RB after the addition of Hg2+ was due to oxadiazole formation when the thiosemicarbazide moiety was liberated by Hg2+-facilitated ring opening of the spirocyclic group, while Cu2+ not only opened the spirolactam ring, but also bonded to the opening product through 1:2 mode. It is worth noting that all these types of probes could only detect Hg2+ or Cu2+ through metal ions-facilitated ring opening of the spirocyclic group mechanism. To the best of our knowledge, probe RB was firstly reported to detect Hg2+ and Cu2+ discriminatively. Moreover, probe RB demonstrated excellent sensitivity toward Hg2+ (LOD 8.36 nM) and Cu2+ (LOD 0.16 mu M), fast responsive time (within 30 s) and wide pH range (6.0-10.0 for Hg2+, 6.0-11 for Cu2+). This probe was further successfully applied to Hela cells and could easily discriminate Hg2+ and Cu2+ through double-channel imaging.

Automated summary

A novel probe RB was designed and synthesized for discriminative detection of Hg2+ and Cu2+. The probe selectively binds with Hg2+ and Cu2+ ions through metal ions-facilitated ring opening of the spirocyclic group mechanism. It demonstrated excellent sensitivity and fast response time, and could easily discriminate Hg2+ and Cu2+ through double-channel imaging in cells.