Synthesis Of BODIPY-Rhodamine And Coumarin-Porphyrin Energy Transfer Cassettes And Investigation Of Their Spectral Properties

Fluorescence analysis has been widely used in various fields due to its high sensitivity and simplicity. The development of fluorescent probes has become a hot topic during these years. As well as we known, the F?rster resonance energy transfer mechanism (FRET) plays an important role in the designs of different probes. In this paper, we judiciously desgined a ratiometric fluorescent probe for Au³⁺ based on a BODIPY-Rhodamine energy transfer platform and a ratiometric fluorescent probe for transition metal ions (Ni²⁺\Co²⁺) based on a Coumarin-porphyrin energy transfer platform, respectively.Based on the BODIPY-Rhodamine energy transfer platform, we have designed and synthesized the first FRET-based ratiometric fluorescent gold probe Ratio-Au, whih was the fist reported gold probe applied to quantitative detection of AuNPs. We have preliminarily investigated and analyzed the detection mechanism, and gave a possible conclusion: the Au³⁺ may promoted the transformation of thioamide pheny substituted middle alkyne to 5-keto-thiazole under test condition, and that the FRET was switched on when the new ratiometric probe was in the presence of Au³⁺, correspondingly, the fluorescence intensity of BODIPY at around 514 nm decreased and simultaneously formed a new fluorescence intensity of Rhodamine at around 594 nm. To the best of our knowledge, such mechanism was unprecedented. The experiments of titration and selectivity demonstrated Ratio-Au showed high sensitivity and selectivity to Au³⁺. Importantly, we have demonstrated, for the first time, ratiometric detection of the Au³⁺ in Yuelu spring and AuNPs in a commercial firming eye essence, which indicated that the ratiometric fluorescent probe for Au³⁺ could be used in the quantitative detection of Au³⁺ in environment and AuNPs in living goods.Previous work in our laboratory indicated that the emission of coumarin strongly overlaped with the absorption of porphyrin, which is critical for the efficient energy transfer between the coumarin energy donor and porphyrin energy acceptor. Because of the fluorescence quenching nature of paramagnetic Ni²⁺\Co²⁺, fluorescence-enhanced or ratiometric probes reported for Ni²⁺\Co²⁺ are very scarce. Thus, it is still a challenge to design fluorescence-enhanced or tatiometric probes for Ni²⁺\Co²⁺. Here, we developed a fluorescent turn-on/ratiometric probe for transition metal ions (Ni²⁺\Co²⁺) based on the coumarin-porphyrin energy trandfer platform. The experiments of titration and selectivity demonstrated this probe could detect the transition metal ions as Co²⁺,Ni²⁺, Zn²⁺. Upon gradual addition of metal ion(Co²⁺,Ni²⁺or Zn²⁺) to probe C, the intensity of the emission band at around 458 nm, which attributed to the emission of coumarin, was almost invariable and the intensity of the emission band at around 656 nm, which attributed to the emission of porphyrin, was significanly increased. Probe C had appropriate water solubility, and could detect the Co²⁺ without further oxidation, and importantly this probe may inspire the design of fluorescence turn-on probes or ratiometric fluorescence probes for Ni²⁺ or Co²⁺ with improved sensitivity and selectivity in future.