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A novel fluorescent probe XDS based on 4-methylumbelliferone and 2-picolylamine platforms has been designed and synthesized, which behaves fast relay recognition of Fe 3+ and PO 4 3− via a fluorescence “on−off−on” response signal. Probe XDS exhibited very high sensitivity and unique selectivity for Fe 3+ over other common metal ions, and the detection limit of was 3.2 × 10 −7 M. Moreover, the addition of the PO 4 3− ions could cause the recovery of fluorescence. This relay recognition feature of probe XDS has potential applications in the determination of trace amount of Fe 3+ and PO 4 3− in environmental systems. Interestingly, fluorescence imaging experiments demonstrated that the probe XDS can also be used to monitoring the intracellular Fe 3+ in RAMOS cells. [ABSTRACT FROM AUTHOR]

A new on-off fluorescent probe 1 for Cu 2+ based on Schiff base compound was designed and synthesized by one-step reaction. The single probe 1 exhibited strong green fluorescence emission. A fluorescence quenching effect and faint color change were observed as soon as the Cu 2+ was added to the probe system in H 2 O/EtOH (v/v = 8:2, HEPES buffer, 0.05 M, pH = 7.4) solution. Other common metal cations did not cause the changes in the fluorescence and color of the probe 1. The optical properties were studied by the fluorescence emission and UV–Vis spectra. Meanwhile, the geometry optimizations of probe 1 and the [1-Cu 2+ ] coordination complexes were also carried out by DFT using the Gaussian 09 program, in which the B3LYP function was used. Based on experimental measurement and theoretical analysis, we can know that the combination ratio of the probe and Cu 2+ is 2:1 and the limit of detection (LOD) is as low as 5.3 × 10 −9 M Besides, the probe 1 was also used to analyze the Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]