Fluorescent Polymer Carbon Dots for the Sensitive–Selective Sensing of Fe³⁺Metal Ions and Cellular Imaging

Abstract

Poly­(ether amine) (PEA)-based fluorescent polymer carbon dots (FPCDs) have been synthesized via a simple Schiff base reaction between poly­(ether amine) (PEA) and formaldehyde followed by its hydrothermal treatment. The resulting water-soluble FPCDs are 2 nm in size and show excitation-dependent emission properties. Blue-emissive FPCDs exhibit the maximum intensity of fluorescence at 440 nm under 360 nm excitation and show a high quantum yield of ∼18%. FPCDs are used for selective Fe3+ metal ion sensing in aqueous media through the fluorescence quenching of FPCDs with a limit of detection of ∼162 nM. Nontoxic FPCDs have been used for cancer cell imaging and also for intracellular Fe3+ metal ion sensing in cancer cells. FPCDs have been used for Fe3+ ion sensing in industrial effluents, and they serve as sensors even in the presence of other competing metal ions. To determine the real application potential of FPCDs as a sensor, FPCDs are used to establish the Fe3+ metal ion content in samples of spiked blood serum with remarkable specificity, sensitivity, and accuracy. Moreover, we proposed a possible sensing mechanism wherein Fe3+ metal ions interacted with the functional groups present on the surface of FPCDs, and fluorescence quenching occurred via a static quenching mechanism along with an inner filter effect (IFE).

Modification of Carbon Dots for Metal‐Ions Detection

“…Sumit Kumar Sonkar et al. reported the fluorescent polymer carbon dots (FPCDs) using poly (ether amine) (PEA) and formaldehyde through Schiff base reaction and hydrothermal treatment [100] . The hydrodynamic size of FPCDs indicated that the particles had a sphere‐like pattern with a ∼2 nm condensed core and a 16–20 nm soft shell.…”

Open system synthesis of narrow-bandwidth red-fluorescent carbon quantum dots with a function of multi-metal ion sensing

“…The sample for XPS was partly coated with Au by sputtering, and the peak of Au (4f 7/2 ) at 84.0 eV was used for charge-up correction. 1 H nuclear magnetic resonance (NMR) spectra were recorded at 500 MHz (JEOL, JNM-ECA500), and chemical shifts were referenced internally to a residual dimethyl sulfoxide (DMSO)-d 6 signal at 2.49 ppm. 1 H-NMR shifts were simulated with ChemDraw.…”

“…1 H nuclear magnetic resonance (NMR) spectra were recorded at 500 MHz (JEOL, JNM-ECA500), and chemical shifts were referenced internally to a residual dimethyl sulfoxide (DMSO)-d 6 signal at 2.49 ppm. 1 H-NMR shifts were simulated with ChemDraw. Ultraviolet-visible (UV-vis) absorption spectra of dispersions were acquired with an optical absorption spectrometer (JASCO, V-750).…”

“…Hence, they are biocompatible and environmentally friendly, with high photostability and thermal stability, and are promising alternatives to quantum dots (QDs) that contain toxic elements such as RoHS-restricted cadmium and lead. Applications include bioimaging, [1][2][3] metal-ion sensing, 1,4,5 moisture sensing in organic solvents, 6 and light-emitting diodes. [7][8][9] Various raw materials, synthesis methods, and purification methods have been used to improve CQD fluorescence properties.…”

Cellulose-Derived Carbon Dots for Inner Filter Effect-Based Selective Sensing of Ofloxacin Antibiotics

“…Fluorescence-based sensing can follow several mechanisms such as the inner filter effect (IFE), the static and dynamic mechanism in which dynamic mechanism includes Förster resonance energy transfer (FRET), photoinduced electron transfer (PET), and surface energy transfer (SET), , or can be aggregation-induced. CD are presently used in sensing several materials, including biomolecules, metal ions, antibiotics, pesticides, etc. However, reports associated with sensing of antibiotics are very limited in number and need thorough investigations.…”