Synthesis of Highly Near-Infrared Fluorescent Graphene Quantum Dots Using Biomass-Derived Materials for In Vitro Cell Imaging and Metal Ion Detection

Abstract

Graphene quantum dots (GQDs) are a subset of fluorescent nanomaterials that have gained recent interest due to their photoluminescence properties and low toxicity and biocompatibility features for bioanalysis and bioimaging. However, it is still a challenge to prepare highly near-infrared (NIR) fluorescent GQDs using a facile pathway. In this study, NIR GQDs were synthesized from the biomass-derived organic molecule ciscyclobutane-1,2-dicarboxylic acid via one-step pyrolysis. The resulting GQDs were then characterized by various analytical methods such as UV−Vis absorption spectroscopy, fluorescence spectroscopy, dynamic light scattering, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Moreover, the photostability and stability over a wide pH range were also investigated, which indicated the excellent stability of the prepared GQDs. Most importantly, two peaks were found in the fluorescence emission spectra of the GQDs, one of which was located in the NIR region of about 860 nm. Finally, the GQDs were applied for cell imaging with human breast cancer cell line, MCF-7, and cytotoxicity analysis with mouse macrophage cell line, RAW 246.7. The results showed that the GQDs entered the cells through endocytosis on the fluorescence images and were not toxic to the cells up to a concentration of 200 μg/mL. Thus, the developed GQDs could be a potential effective fluorescent bioimaging agent. Finally, the GQDs depicted fluorescence quenching when treated with mercury metal ions, indicating that the GQDs could be used for mercury detection in biological samples as well.

Diverse Applications of Biomass‐Derived 5‐Hydroxymethylfurfural and Derivatives as Renewable Starting Materials

“…For GQD formation, a solution of CBDA-2 was then autoclaved for 12 h at 200 °C. [85] These GQDs were found to be non-toxic and yielded two distinct emission peaks (440 and 850 nm) with one excitation wavelength (310 nm), which was quenched when treated with mercury metal ions. These results suggest that these particles can find utility as fluorescent bioimaging agents and for mercury detection in biological samples.…”

“…Reagen et al synthesized NIR graphene quantum dots (GQDs) from the biomass-derived organic molecule cis-cyclobutane-1,2dicarboxylic acid (CBDA-2). [85] As shown in Scheme 25, CBDA-2 can be synthesized from furfural (66) by the conversion to trans-3-(2-furyl)acrylic acid (82) using a Knoevenagel condensation with malonic acid under basic conditions. Furyl acrylic acid can then be converted to CBDA-2 stereospecifically with a solidstate [2 + 2] photocycloaddition, [86] or via a similar photocycloaddition with intermediate esterification and saponification steps, [87] ostensibly for easier purification.…”

“…These results suggest that these particles can find utility as fluorescent bioimaging agents and for mercury detection in biological samples. [85] The CBDA-2 ligand has also been utilized as a ligand for the synthesis of green metal-organic materials (GMOM), demon-strated through the synthesis of two 2D coordination polymers with Cu and Co that exhibit thermochromic behaviors. [88]…”

“…Reagen et al. synthesized NIR graphene quantum dots (GQDs) from the biomass‐derived organic molecule cis ‐cyclobutane‐1,2‐dicarboxylic acid (CBDA‐2) [85] . As shown in Scheme 25, CBDA‐2 can be synthesized from furfural ( 66 ) by the conversion to tran s‐3‐(2‐furyl)acrylic acid ( 82 ) using a Knoevenagel condensation with malonic acid under basic conditions.…”

Heavy metal ion detection using green precursor derived carbon dots

“…The crystallinity and graphitic nature of the carbon dots can be identified using X-ray diffractometer (XRD) ( Bogireddy et al., 2021a ). X-ray photoelectron (XPS) ( Reagen et al., 2021 ) and Fourier transform infrared spectroscopy (FT-IR) experiments have been performed to analyze carbon dots' chemical and structural composition ( Bogireddy et al., 2020a ). The chemical structure, phase, and molecular interactions of carbon dots have been analyzed from Raman Spectroscopy studies.…”