Amino Acid Groups Enable Electrosynthesized Polyfluorenes to Specifically Recognize Cr₂O₇^2–

The unique “molecular wire effect” property of conjugated polymers (CPs) enables them to own signal amplification. Therefore, they are good candidates for constructing fluorescent sensors with high sensitivity. In this work, two water-soluble polyfluorene derivatives P(Fmoc-Arg-OH) and P(Fmoc-Glu-OH) were synthesized using electrochemical polymerization in boron trifluoride diethyl etherate–trifluoroacetic systems. Absorption and emission spectra showed that the two polymers were blue emitters. In order to specifically target dichromate ions (Cr2O72–), we introduced amino acid groups in the side chain of the two polymers. A series of selective and competitive experiments in a pH = 7.00 PBS solution showed that both polymers had high selectivity toward Cr2O72–. Thanks to their signal amplification effect, the limits of detection of P(Fmoc-Arg-OH) and P(Fmoc-Glu-OH) could reach 16.67 pM and 3.33 μM, respectively. All results showed that CPs are a good platform for designing fluorescent sensors with high selectivity and sensitivity.