Hit Multiple Targets with One Arrow: Pb²⁺ and ClO^– Detection by Edge Functionalized Graphene Quantum Dots and Their Applications in Living Cells

Abstract

Recently, multimodal detection of analytes through a single nanoprobe has become an eminent approach for researchers. Herein a fluorescent nanoprobe, functionalized-GQD (F-GQD), has been designed through edge functionalization of graphene quantum dots (GQDs) by 2,6diaminopyridine molecules. The fluorescence of F-GQD is quite sensitive to medium pH, making it a suitable pH sensor within the pH range 2−6. Interestingly, F-GQD shows dual sensing of Pb 2+ and ClO − by entirely different pathways; Pb 2+ exhibits fluorescence turn-on performance while ClO − triggers turn-off fluorescence quenching. The fluorescence enhancement may originate from the Pb 2+ -induced aggregation of the nanodots. The limit of detection (LOD) was also impressive, 1.2 μM and 12.6 nM for Pb 2+ and ClO − , respectively. The detailed mechanistic investigations reveal that both dynamic and static quenching effects operate together in the F-GQD-ClO − system. The dynamic quenching was attributed to the energy migration from F-GQD to ClO − through hydrogen bonding interaction (static quenching) between the amine group at the F-GQD surface and ClO − . The F-GQD nanodot reveals excellent sensitivity toward the detection of ClO − in real samples. Moreover, the F-GQDs also serve as multicolor fluorescent probes for cell imaging; the probe can easily penetrate the cell membrane and successfully detect intracellular ClO − .

Red-Emitting Silver Nanoclusters for Dual-Mode Detection of Cu2+ and Vitamin B12 in Living Cells

“…This observation was supported by the upward curvature nature of the F / F 0 plot (Figure b), which indicates that more than one mechanism is involved in the quenching process. The static quenching constant can be calculated using the modified Stern–Volmer equation. , where [ Q ] signifies the concentration of the quencher (Cu 2+ ) and K SV and V signify the dynamic and static quenching constants, respectively. The value of V is found to be 3.38 × 10 3 M –1 .…”

“…The static quenching constant can be calculated using the modified Stern−Volmer equation. 58,59 ) where [Q] signifies the concentration of the quencher (Cu 2+ ) and K SV and V signify the dynamic and static quenching constants, respectively. The value of V is found to be 3.38 × 10 3 M −1 .…”

Ratiometric Multimode Detection of pH and Fe3+ by Dual-Emissive Heteroatom-Doped Carbon Dots for Living Cell Applications

“…X-ray photoelectron spectroscopy (XPS) (Figure d) of D-CDs disclosed the three main elements C, N, and O, with the peaks located at 284, 399, and 530 eV, respectively, with the atomic percentages of 66.0 (C 1s), 19.2 (N 1s), and 14.8 (O 1s). The deconvoluted XPS peaks of C 1s were at 284.4, 285.2, 286, 287.9, and 289.8 eV, which were linked to C–C/CC, C–N, CN, CO, and O–CO, respectively (Figure e). , The high-resolution N 1s spectrum revealed four different kinds of N-functionalities: pyridinic-N (398.8 eV), pyrrolic-N (399.5 eV), amino-N (400.2 eV), and graphitic-N (401.7 eV) (Figure f). , Similarly, the deconvoluted O 1s XPS spectrum exhibited well-defined peaks at 530.8, 531.3, 532.1, 533, and 533.8 eV corresponding to the O–C/C–O–C, OC–N, CO, C–OH, and O–CO bonds, respectively (Figure g). , The exact percentage of contribution calculated from the XPS analysis is presented in Table S1. The Fourier transform infrared (FTIR) spectra (Figures S1, and h) showed peaks at 1612, 1512, 1434, 1364, and 1290 to 1140 cm –1 corresponding to the stretching vibrations of the amide linkage (NH–CO), CN, CC, N–H, and C–O-related functional groups. ,,, The combined XPS and FTIR analyses ascertained the chemical composition and functionalities of the D-CD surfaces.…”

Microwave-Assisted Synthesis of Red Emitting Copper Nanoclusters Using Trypsin as a Ligand for Sensing of Pb2+ And Hg2+ Ions in Water and Tobacco Samples

“…The LODs for Pb 2+ and Hg 2+ are 14.32 nM and 56.81 nM, respectively. In addition, the LODs of the proposed technique have lower values as compared to that of other reported methods for the detection of Pb 2+ and Hg 2+ ions [25][26][27][28][44][45][46][47][48][49][50][51][52][53][54] (Table I).…”