Pyrazoloquinoline-based fluorescent sensor for the detection of Pb2+, Zn2+ and the realization of an OR-type optical logic gate

Abstract

A novel derivative of 1H-pyrazolo[3,4-b]quinoline (PQ2OH) has been synthesized and investigated by means of fluorescence and UV–vis absorption spectroscopy. The emission properties of the studied compound are characterized by low fluorescence quantum yields and short fluorescence lifetimes owing to the photoinduced electron transfer process, which is particularly efficient in highly polar solvents. We have employed this process in the optical detection of bivalent cations like Zn2+, Cd2+, Mg2+, Co2+, Ni2+, Ca2+, Pb2+, and Cu2+. The compound exhibits good selectivity towards Pb2+ and Zn2+ with limits of detection of 1.07 × 10−6 M and 1.06 × 10−6 M, respectively. The optical response is based on the recovery of native green fluorescence from pyrazoloquinoline. The sensor is able to detect Pb2+ in river water solutions with good sensitivity and can mimic an OR-type optical logic gate in cooperation with Pb2+ and Zn2+.