Single Non‐Blinking Graphene Quantum Dots Identified by Single‐Particle Catalysis

Abstract

Quantum dots (QDs) with non‐blinking applied in bio‐imaging is important for understanding cellular dynamics by monitoring single particles in living cells. Antibunching is once believed to be applied to identify a single QD, which shows a strong dependence on the atom or ion number. However, recent works indicate that the antibunching alone may not be sufficient to demonstrate that the fluorescence comes from a single QD. To some extent, it is neither necessary nor sufficient for a single QD, though it is absolutely right for a single atom because a single QD is composed of thousands of atoms, which in principle are favorable to the formation of multi‐excitonic states. Blinking behavior, almost unobservable in ensembles due to the averaging, is characteristic of the single QD which owns the quantum effect due to its discrete energy levels. Here, a method of transformation of a single graphene quantum dot from non‐blinking to blinking via catalytic reaction to identify a single QD is reported, which can also help with understanding the catalytic dynamics of a single QD, which is a complementary means of confirming a single QD. The reported technique paves the way to understanding a single QD and its catalytic and kinetic behaviors.

A review on synthesis, properties, and biomedical applications of graphene quantum dots (GQDs)

“…In addition, Fu et al proposed a method of converting non-blinking GQDs to blinking by single-particle catalytic reaction. This demonstrates the potential to investigate single-molecular dynamic processes through the blinking signal of GQDs [231]. Moreover, GQDs can be used in multicolor SMLM-based super-resolution imaging by combined with various dye molecules.…”

“…Selective detection of various antigens or cells through antibodies [198,199,201] GQDs@AuNP or GQDs@AgNP Detecting glucose, cholesterol, catechol, and β17-estradiol by immobilizing various enzymes [200,[203][204][205] Electrochemiluminescence sensors N-GQDs@Ru(bpy) 3 Co-reactants in combination with the conventional luminophores of ECL for detecting MMP-2 [207] GQDs@CeO 2 @AgNP or GQDs-PEI-GO@AuNP Amplifying ECL signals by synergistic effects between various nanomaterials [208,209] GQDs@MoS 2 Amplifying ECL signals by rapid charge transfer and DNA walking for detecting DNA [211] Bioimaging Fluorescence imaging Tm-GQDs or RGQDs Emitting fluorescence at 900 nm under 808 nm excitation in mice [38,214] N, B-GQDs or N-GQDs Emitting NIR-II wavelength or demonstrating two-photon properties [168,215] GQDs-antibodies Targeted imaging of surface antigen GD2 on neuroblastoma cell [217] Magnetic resonance imaging B-GQDs Demonstrating high MRI performance in vivo [178,220] GQDs-Gd-DOTA or GQDs-Gd-DTPA Significant enhancement of MRI performance with increased biocompatibility [219,222,223] Super-resolution imaging GQDs Biocompatible fluorescent probes for SMLM due to their superior blinking performance [161,230,231] GQDs with various dye molecules…”

Non‐Blinking Luminescence from Charged Single Graphene Quantum Dots

“…Therefore, non-blinking GQDs are a promising material as biomedical markers for realtime bioimaging. It is important to note that GQDs, whether synthesized by bottom-up [13] or top-down methods, [14] have been found to be non-blinking, but to the best of our knowledge, there is no explanation for this observation till now.…”

“…[29] In addition, a slight red shift on increasing the delay time from 0.5 to 100 ps indicates that the GQDs have a moleculelike structure, which we attribute to oxygen-containing functional groups, this phenomenon is consistent with our previous work. [13] All of the growth curves can be fitted with a single-exponential function, yielding the corresponding growth lifetimes (𝜏 g ) of 0.48, 0.26, and 0.17 ps at different probe wavelengths (Figure S16, Table S16, Supporting Information). The decay curves were fitted with biexponential functions, which indicates that all the GQDs with oxygen-containing functional groups exhibit two distinguishable transient behaviors, that is, an early rapid decay of several picoseconds (𝜏 1 ) for intraband relaxation through a carrier-phonon scattering route, and subsequent slow decay in the range ≈40 to ≈100 ps (𝜏 2 ) for carrier trapping to PL centers.…”