Polymer based ON-OFF-ON fluorescent logic gate: Synthesis, characterization and understanding

• A new three-in-one type optical sensor is synthesized for Fe 3+, F − and ascorbic acid. • A unique polymer based ON-OFF-ON fluorescent logic gate is developed. • A novel method has been designed to check the quality of Vitamin C tablets. • The multi-dimensional role as a probe is understood in the light of molecular structures. • Both theory (DFT and FMO) and experiments (CHEQ and ISC) help to understand. Polymer based fluorescent logic gates have gained considerable research interests, because of their important applications in chemical computing, bioimaging, biosensing and therapeutic technologies. A fluorescent dye functionalized polymer (FDFP) with enhanced aqueous solubility and biocompatibility has been synthesized via single step condensation reaction of 1-pyrenecarboxaldehyde (1-PA) with agar polymer. The FDFP is characterized by NMR, XRD, SEM, FTIR, absorption characteristics and emission spectra. The quantum yield of the probe (0.025) is suitable for the sequential detection of Fe 3+ and F − through ‘OFF-ON’ fluorescence response technique. This unique optical responses have been effectively utilized to construct an INHIBIT logic gate where Fe 3+ and F − act as chemical inputs and emission at 469 nm as the desired output. An attempt has been made to understand the optical behavior of the probe in the light of theoretical studies (DFT, FMO). The theoretical studies explore further that the chelation enhanced quenching (CHEQ) and the chelation breaking de-quenching (CHBD) are the chief mechanism of exhibiting unique optical properties. A new method has been designed to sense and estimate the biologically significant molecule vitamin C (ascorbic acid).