Photoluminescent coral-like carbon-branched polymers as nanoprobe for fluorometric determination of captopril

The authors describe the synthesis of fluorescent coral-like carbon nano-branched polymers (PCNBPs) co-doped with nitrogen and phosphorus. Uric acid and phosphoric acid act as nitrogen and phosphorus sources, respectively. The PCNBPs have a coral-like branched structure, are cross-connected, and < 20 nm in skeleton diameter. Their blue fluorescence, best measured at excitation/emission wavelengths of 330/425 nm, is quenched by mercury (II) ions due to the specifically restricted rigid conformation caused by the interaction of phosphorus, nitrogen, and oxygen groups on the surface of the PCNBPs. Fluorescence is selectivity quenched by Hg(II) but restored in addition of the hypertension drug captopril (CAP) in the range 50 nM to 40 mu M concentration range. Fluorescence recovery is attributed to the effectively specific interactions between the thiol group of CAP and Hg(II). The method was applied to the determination of the concentration of Cap in pharmaceutical samples, and recoveries were between 97.6 and 105.1%.