Application of stimuli-responsive FRET behavior toward cyanide detection in a photo-switchable [2]pseudorotaxane polymer containing the BODIPY donor and the merocyanine acceptor

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2021-03, Vol.9 (7), p.2321-2333
• Main Authors: Gouda, Chinmayananda, Barik, Debashis, Maitra, Chandrima, Liang, Kai-Chieh, Ho, Feng-Cheng, Srinivasadesikan, Venkatesan, Chandran, Sarala, Wu, Shu-Pao, Lin, Ming-Chang, Lin, Hong-Cheu
• Format: Article
• Language: English
• Subjects: Cyanide process; Emission; Emissivity; Energy transfer; NMR; Nuclear magnetic resonance; Polymers; Spiropyrans; Titration
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d0tc05000h

We have developed a supramolecular (close form) [2]pseudorotaxane polymer containing the green-emissive ( λ em = 523 nm) BODIPY-based pillar[5]arene host and the non-emissive spiropyran (SP)-based cyano guest (close form), which can be converted to a red-emissive ( λ em = 630 nm) merocyanine (MC)-based guest (open form) upon UV exposure as well as turned into a bi-fluorophoric host-guest polymer with ratiometric PL emission of Förster resonance energy transfer (FRET) behavior in THF/water solution (60% H 2 O, v/v). The equal host-guest molar ratio and the formation of the [2]pseudorotaxane polymer can be further verified using 1 H NMR titration, Job's plot analysis, DOSY and ITC experiments. Hence, the bi-fluorophoric host-guest (with the MC open form) polymer possessed the highest red-emission of the MC acceptor, which was also confirmed using TRPL measurements to possess the shortest lifetime of 0.37 ns and the best FRET efficiency of 83.5%. Since the MC unit could react with CN − to induce a non-emissive quenching process, the mono-fluorophoric guest would show turn-off PL behavior and detect cyanide ions with a corresponding limit of detection (LOD) value of 0.94 μM. In comparison, the optimal LOD value of 0.48 μM toward CN − anion could be achieved by our bi-fluorophoric host-guest polymer via the FRET-OFF process. Therefore, cyanide detection and cell viability tests using the open form of the [2]pseudorotaxane polymer suggest useful bio-imaging applications in living cells. The bi-fluorophoric host-guest [2]pseudorotaxane polymer containing merocyanine-based guest (open form) showed sensitive cyanide detections and useful bio-imaging applications in living cells via FRET-OFF processes to recover green donor emissions.