Bridge between Temperature and Light: Bottom-Up Synthetic Route to Structure-Defined Graphene Quantum Dots as a Temperature Probe In Vitro and in Cells

Abstract

Owing to their unique superiorities in chemical and photoluminescence (PL) stability, low toxicity, biocompatibility, and easy functionalization, graphene quantum dots (GQDs) are widely used in cell imaging, probes, and sensors. However, further development and deeper research of GQDs are restricted by their imprecise and complex structure and accompanying controversial PL mechanism. In this work, two kinds of structure-defined water-soluble GQDs, with different oxidation degrees, are synthesized from molecules using bottom-up syntheses methods. After being studied by a series of characterizations, their optical properties, functional groups, molecular weight, and structural information were obtained. The optical properties of GQDs could be optimized by controlling their oxidation degree. The PL mechanism of GQDs was investigated by comparing their structure and properties. Furthermore, robust, stable, and precise temperature probes were designed using the GQDs, which exhibited an excellent wide response range, covering the whole physiology temperature range, from 0 to 60 °C in water. Moreover, the GQDs were successfully applied as temperature-responsive fluorescence probes in the HeLa cell line. These works laid a solid foundation for further applications of GQDs as biological thermoprobes and selectively temperature detectors in vitro cellular and in vivo.

Outstanding Graphene Quantum Dots from Carbon Source for Biomedical and Corrosion Inhibition Applications: A Review

“…The resultant supernatant was eventually isolated as GQDs. By induction and doping, the GQDS solvents can also be synthesized [77].…”

“…The HBC molecules were folded during the pyrolysis stage into a faulty graphite structure in this process. Using a modified Hummers process, the graphite was oxidized, exfoliated, and then reduced with hydrazine hydrate to give a pure form of GQDs [77,81].…”

Shedding Light on Graphene Quantum Dots: Key Synthetic Strategies, Characterization Tools, and Cutting-Edge Applications

“…Another approach is the synthesis of graphene molecules using an organic synthetic route [ 94 ]. In the reaction between 1,3,5-triethynylbenzene (TB) and tetraphenylcyclopentadienone (TC) at 160 °C in o -xylene overnight, polycyclic aromatic hydrocarbons (PAHs) were produced.…”

Measurement of Temperature Distribution at the Nanoscale with Luminescent Probes Based on Lanthanide Nanoparticles and Quantum Dots

“…Traditional thermometers such as liquid-filled glass thermometers, thermocouples and optical sensors generally measure temperature on a macroscale . In efforts to achieve higher spatial resolutions in temperature measurement, the geometrical size of thermometer probes must be near molecular dimensions. , Several thermo-sensing technologies have been developed at a sub-micron scale. − Particularly, fluorescent thermometers based on nanoparticles, − organic dyes, and polymers − have the advantage of non-contact and non-destructive detection. Most notably, upconversion nanophosphors (UCNPs) have high photostability and chemical stability and the ability to withstand high temperatures, which are conducive to continuous measurement of temperature for a long time. , As for the Er 3+ /Yb 3+ -doped upconversion system, the change of the fluorescence intensity ratio of the 2 H 11/2 → 4 I 15/2 to 4 S 3/2 → 4 I 15/2 transitions is used for luminescent thermometry. − The thermometer only depends on the location of Er 3+ , so it can realize temperature detection with high spatial resolution.…”