Ratiometric pH Sensing, Photophysics, and Cell Imaging of Nonaromatic Light-Emitting Polymers

Abstract

Here, four nontraditional fluorescent polymers (NTFPs) of varying N,N-dimethyl-2-propenamide (DMPA) and butyl prop-2-enoate (BPE) mole ratios, i.e., 2:1 (NTFP1), 4:1 (NTFP2), 8:1 (NTFP3), and 16:1 (NTFP4), are prepared via random polymerization in water. The maximum fluorescence enhancement of NTFP3 makes it suitable for ratiometric pH sensing, Cu(II) sensing, and pH-dependent cell imaging of Madin-Darby canine kidney (MDCK) cells. The oxygen donor functionalities of NTFP3 involved in binding and sensing with Cu(II) ions are studied by absorption, emission, electron paramagnetic resonance, Fourier transform infrared (FTIR), and O1s/ Cu2p X-ray photoelectron spectroscopies (XPS). The spectral responses of the ratiometric pH sensor within 1.5−11.5 confirm 22 and 44 nm red shifts in absorption and ratiometric emission, respectively. The striking color changes from blue (436 nm) to green (480 nm) via an increase in pH are thought to be the stabilization of the charged canonical form of tertiary amide, i.e., −C(O − ) N + (CH 3 ) 2 , realized from the changes in the absorption/fluorescence spectra and XPS/FTIR analyses. The through-space n−π* interactions in the NTFP3 aggregate, N-branching-associated rigidity, and nonconventional intramolecular hydrogen bondings of adjacent NTFP3 moieties in the NTFP3 aggregate contribute to aggregation-enhanced emissions (AEEs). Here, structures of NTFP3, NTFP3 aggregate, and Cu(II)-NTFP3; absorption; n−π* interactions; hydrogen bondings; AEEs; and binding with Cu(II) are ascertained by density functional theory, time-dependent density functional theory, and reduced density gradient calculations. The excellent limits of detection and Stern−Volmer constants of NTFP3 are 2.24 nM/0.14234 ppb and 4.26 × 10 3 M −1 at pH = 6.5 and 0.95 nM/0.06037 ppb and 4.90 × 10 3 M −1 at pH = 8.0, respectively. Additionally, the Stokes shift and binding energy of NTFP3 are 13,636 cm −1 /1.69 eV and −4.64 eV, respectively. The pH-dependent MDCK cell imaging ability of noncytotoxic NTFP3 is supported via fluorescence imaging and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Synthesis of Intrinsically Dual-Emissive Aliphatic Conducting Polymer and ESIPT-Associated Switching of Amide-Aggregate to Imidol-Aggregate for Sensing of Cr(III) and Fe(III)

“…Herein, the initial stability up to 150 °C was mediated by several conventional and nonconventional hydrogen bonds in FCP s (Figures a,b and S3 and Tables S4 and S5). The weight losses of FCP s within 202–352 °C were related to the degradation of −CONH/–CON through the cyclization of amides to imides . A further weight loss within 352–502 °C was ascribed to the decomposition of −COOH forming anhydrides (Figure S3).…”

“…The weight losses of FCPs within 202−352 °C were related to the degradation of −CONH/−CON through the cyclization of amides to imides. 39 A further weight loss within 352−502 °C was ascribed to the decomposition of −COOH forming anhydrides (Figure S3). 29,40 The ratios of amide/acid degradation were found to be 0.20:1, 0.19:1, 0.34:1, 0.38:1, and 0.37:1 in FCP1, FCP2, FCP3, FCP4, and FCP5, respectively (Figure S3 and Table S8).…”

Excited-State Intramolecular Proton- and Inter-Polymer Charge-Transfer of Semiconducting Redox Polymers for Fe(III), Cd(II), and Hg(II) Sensing

“…The uprising demand for multilight emissive semiconducting polymers is ascribed to their outstanding features including bright photoluminescence (PL), fast radiative rate, energy transfer amplification, large cross section for two-photon absorption, modifiable photoelectric property, and strong photostability. , Such unique features enable these polymers to be employed in LEDs and organic electronics. However, these reported materials contain aromatic building units, i.e., carbazolyl-biphenyl, pyridinyl-phenyl, phenyl-pyrimidine, pyrene, dibenzofuran, triphenylamine, and phenanthroimidazole. − Notably, aromatic polymers suffer from π – π stacking interaction assisted aggregation, nonresonant electron tunneling caused PL quenching, and reduced conductivity. , These major drawbacks can be circumvented by introducing purely aliphatic and nonconventional multi-light emitting semiconducting polymers having additional advantages, such as nonrequirements of physical doping, complex synthesis, and complicated tagging procedure; minimum background noise in low concentrated solution; higher signal-to-noise ratio; large Stokes shift; restriction of π – π stacking; and aggregation enhanced emissions (AEEs). , Notably, low band gap, flexibility of polymer chain, structural tenability, supramolecular interaction assisted rigidity, and π – π * transition among nonconventional heteroatomic subluminophores (HASs) significantly enhance the PL efficiency, sensing capacity, and conductivity. , In this context, the materials exhibiting simultaneous charge transfer (CT) and amide–imidol tautomerism mediated excited state (ES) intramolecular proton transfer (ESIPT) within polymeric chains are beneficial in enhancing their PL efficacies. − In this context, through-space, inter-polymer charge transfer (IPCT) phenomenon involves charge translocation from the HOMO (H) of the donor to the LUMO (L) of the acceptor in polymeric aggregates. Notably, appropriate spatial separation and angle of alignment between the donor and acceptor is essential to facilitate the IPCT.…”

“…7,8 Notably, low band gap, flexibility of polymer chain, structural tenability, supra- molecular interaction assisted rigidity, and π−π* transition among nonconventional heteroatomic subluminophores (HASs) significantly enhance the PL efficiency, sensing capacity, and conductivity. 9,10 In this context, the materials exhibiting simultaneous charge transfer (CT) and amide− imidol tautomerism mediated excited state (ES) intramolecular proton transfer (ESIPT) within polymeric chains are beneficial in enhancing their PL efficacies. 11−13 In this context, throughspace, inter-polymer charge transfer (IPCT) phenomenon involves charge translocation from the HOMO (H) of the donor to the LUMO (L) of the acceptor in polymeric aggregates.…”

Synthesis of Semisynthetic Dual-State Fluorescent Polymers and Roles of Starch/Pectin on AIET-Assisted Dual-Emission, Conductivity, and Metal-Ion Sensing

“…8,9 These bottlenecks of conventional aromatic luminogens have encouraged the inventions of AMLs circumventing most of the major intrinsic limitations of aromatic sensors. 5 Nonconventional emissions in AMLs originate from the physicochemical confinement of atypical heteroatomic fluorophores (AHFs), i.e., secondary/tertiary amide (−CONH−/− CON<) and carboxylic acid (−COOH) functionalities, within the polymeric framework of AMLs. 10,11 The close proximity of these AHFs imparts stiffness in polymer conformation and elevates noncovalent supramolecular interactions.…”