Fluorescence Emission of Polyethylenimine-Derived Polymer Dots and Its Application to Detect Copper and Hypochlorite Ions

Abstract

Polymer dots with nonconjugated groups that are facile to synthesize and environmentally friendly generally attract substantial interest. However, their fluorescence-emitting mechanisms are not clear. In this paper, nonconjugated polymer dots (N-PDs) are synthesized by amidation reaction between polyethylenimine (PEI) and citric acid (CA), then self-assemble into rice-like dots in aqueous phase with a high fluorescence quantum yield. Such nitrogen-containing nonconjugated compounds N-PDs are believed to be inherently fluorescent, and the reported reasons for fluorescence-emitting are discussed. Importantly, these N-PDs can be used as an excellent fluorescent probe to detect Cu2+ and ClO– in aqueous solutions. Cu2+ could combine with the PEI moiety of the N-PDs to form a copper amine complex and then quench the fluorescence by an internal filtration effect. ClO– could oxidize the hydroxyl groups on the surface of the N-PDs to form a positive charge, blocking electron transfer between the hydroxyl groups and the chromophore groups. Finally, the sensor was successfully applied to the detection of Cu2+ and ClO– in environmental water samples.

N-alkylation briefly constructs tunable multifunctional sensor materials: Multianalyte detection and reversible adsorption

“…Using reported methods ( Geng et al., 2019 ; Zhang et al., 2019a , 2019b ; To et al., 2020 ; Fan et al., 2021 ), the crystallinity and thermal stability of each material were investigated. As depicted in Figure S12 , the PXRD pattern of PBI exhibited a broad peak at 15°–35°, indicating an amorphous state.…”

“…Importantly, the morphologies of materials were evaluated by SEM as reported methods ( Shan et al., 2019 ; Zhang et al., 2019a ; To et al., 2020 ; Fan et al., 2021 ) ( Figure 3 ). The surface of PBI was uneven and loose powder with stacked micropores was located between the layers.…”

“…SPBI-c was found to selectively detect PA, DNP, and NP by fluorescence quenching ( Figure S42 ). Using a reported method ( Jiao et al., 2019 ; Zhang et al., 2019a ), the fluorescence quenching efficiencies of three typical NACs (PA, DNP, and NP) for SPBI-c were studied ( Figure 6 and S43 ). With 160 μ M PA, a maximum quenching efficiency of 96.8% was obtained, whereas higher concentrations of DNP and NP were required to achieve similar quenching efficiencies, demonstrating the high sensitivity of SPBI-c to PA. Further-more, using a reported approach ( Gao et al., 2019 ; Nandi et al., 2020 ), the LODs of SPBI-c for PA, DNP, and NP were calculated to be 1.81 × 10 −7 , 2.29 × 10 −7 and 2.62 × 10 −7 M, respectively, which are equivalent to the LODs of some reported NAC sensors ( Gao et al., 2019 ; Nandi et al., 2020 ; Ghorai et al., 2019 ; Dutta et al., 2020 ).…”

“…According to the reported method ( Zhang et al., 2019a ; To et al., 2020 ), the morphology for SPBI and the morphology changes of SPBI combined with metal ions or nitroaromatic compounds (NACs) were determined by field emission scanning electron microscope.…”

pH and thermo responsive aliphatic tertiary amine chromophore hyperbranched poly(amino ether ester)s from oxa‐Michael addition polymerization

“…[ 8–22 ] Among of unconventional fluorescent compounds, tertiary amine chromophore polymers with intrinsic fluorescence and stimulus responsiveness, which have proved to be an effective biomedical application materials and been extensively studied. [ 23–28 ]…”