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

Here, four nontraditional fluorescent polymers (s) of varying ,-dimethyl-2-propenamide (DMPA) and butyl prop-2-enoate (BPE) mole ratios, i.e., 2:1 (), 4:1 (), 8:1 (), and 16:1 (), are prepared via random polymerization in water. The maximum fluorescence enhancement of 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 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), realized from the changes in the absorption/fluorescence spectra and XPS/FTIR analyses. The through-space -π* interactions in the aggregate, N-branching-associated rigidity, and nonconventional intramolecular hydrogen bondings of adjacent moieties in the aggregate contribute to aggregation-enhanced emissions (AEEs). Here, structures of , aggregate, and Cu(II)-; absorption; -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 are 2.24 nM/0.14234 ppb and 4.26 × 10 M at pH = 6.5 and 0.95 nM/0.06037 ppb and 4.90 × 10 M at pH = 8.0, respectively. Additionally, the Stokes shift and binding energy of are 13,636 cm/1.69 eV and -4.64 eV, respectively. The pH-dependent MDCK cell imaging ability of noncytotoxic is supported via fluorescence imaging and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.