Fluorescent Graphene Quantum Dots Research Articles

Synergistic effects of graphene quantum dots nanocarriers and folic acid targeting agent on enhanced killing of breast cancer cells by tamoxifen

AbstractIn this study, a new targeted and controlled‐release drug delivery system based on graphene quantum dots (GQDs) was fabricated. The fluorescent GQDs were synthesized via an environmentally‐friendly chemical oxidation method, using graphene oxide (GO) as a precursor and hydrogen peroxide and ammonia solution as oxidants. Folic acid (FA), as a targeting agent, was bound to GQDs through strong amide covalent bindings, and tamoxifen (TMX), as a hydrophobic anticancer drug, was non‐covalently attached to the nanocarrier via π–π stacking bonds. The as‐prepared GQDs and TMX/FA‐GQDs were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectroscopy (UV/Vis), and photoluminescence spectroscopy (PL). The resulting TMX/GQDs demonstrated pH‐sensitive release behaviour with an overall release of 85% and 58% at pH 5.5 and 7.4, respectively, after 120 h. Also, the MTT assay test performed on MCF‐7 cells presented negligible toxicity of the nanocarriers, even at high concentrations. At the same time, the targeted nanocarrier, TMX/FA‐GQDs, showed much more toxicity towards MCF‐7 cells than the non‐targeted one and free TMX.

Open system massive synthesis of narrow-band blue and green fluorescent graphene quantum dots and their application in water sensing

PG-derived graphene quantum dots (GQDs) were obtained with 99.4% product yield and exhibited narrow-band blue fluorescence with a high quantum yield.

Fluorescence mechanism and biomedical applications of graphene quantum dots

Graphene quantum dots (GQDs) are fluorescent graphene nanoparticle that have tunable emission wavelength, high emission intensity and biocompatibility. The fluorescence mechanism is still indecisive, yet explanations exist. Surface or edge defects and quantum confinement are two major explanations and they accounted for the florescence properties observed so far. GQDs quantum confinement is applied to change the emission wavelength. Surface functional groups usually improve biocompatibility and solubility. Under several cases, surface defects are also engineered to tune emission wavelength and intensity to serve specific engineering propose. GQDs have found applications in bioimaging, biosensing, and therapy. GQDs can generate high intensity emission in the NIR-II window which is ideal in in vivo bioimaging. GQDs can be generated from folic acid in a one-step procedure. The GQDs generated this way can track folate receptor and help cancer diagnostics. High intensity emission also enables GQDs to be used in photothermal or photodynamic therapy. Future applications will be promoted by a better understanding of GQDs fluorescence mechanisms.

A fluorescent system based on graphene quantum dots-capped magnetic hydroxyapatite-MIL-100 metal-organic frameworks for pH-sensitive and controlled release of DOX

Since metal-organic frameworks (MOFs) have shown great potential as emerging candidates in biomedical applications, it is worthwhile to construct an MOF-based drug delivery system. Hence, in this work, magnetic hydroxyapatite-MIL-100 metal-organic frameworks (SiO2@Fe3O4-HA-MIL-100) with antioxidant properties were synthesized as a novel drug delivery system through in-situ self-assembly of MIL-100 MOFs around pre-synthesized magnetic hydroxyapatite nanoparticles. Then, SiO2@Fe3O4-HA-MIL-100 nanocomposites were capped with fluorescent graphene quantum dots (SiO2@Fe3O4-HA-MIL-100-GQDs) for loading and delivering of doxorubicin (DOX). The SiO2@Fe3O4-HA-MIL-100, GQDs, and SiO2@Fe3O4-HA-MIL-100-GQDs encapsulation efficiency was 80.2, 42.2, and 95.8 %, respectively. The in vitro DOX release amount after 72 h from SiO2@Fe3O4-HA-MIL-100, GQDs, and SiO2@Fe3O4-HA-MIL-100-GQDs at pH 5 was 75.8 %, 86.2 %, and 67.2 %, while at pH 7.4 was 37.3 %, 50.1 %, and 29 %, respectively. These results confirmed a pH-responsive controlled release of DOX from nanocomposites. The release mechanism of DOX from the prepared nanocomposites was also well fitted to the Korsmeyer-Peppas kinetic, Fickian diffusion, and diffusion-controlled release. In addition, the MTT assays of nanocomposites against MCF-7 breast cancer cell lines clearly illustrated that the prepared nanocomposites had no significant cytotoxicity, while DOX-loaded nanocomposites had notable toxicity to MCF-7 cells. The IC50 values of DOX, SiO2@Fe3O4-HA-MIL-100-DOX, GQDs-DOX, and SiO2@Fe3O4-HA-MIL-100-GQDs-DOX against MCF-7 cells calculated at about 4.2 μg/mL, 1.8 μg/mL, 3 μg/mL, and 1.2 μg/mL, respectively. The DPPH test results also showed that the nanocomposites have excellent antioxidant activity. In addition, the in vitro hemolysis results displayed neglectable hemolysis activity (lower than 5 %) of SiO2@Fe3O4-HA-MIL-100-GQDs even at a high dose. Therefore, these new drug delivery systems can be used safely as potential drug carriers in targeted cancer therapy.

One-step assembly of TA-FeIII supramolecular shell on AgNPs surface for regulating fluorescence intensity of quantum dots

During surface-enhanced fluorescence processes, the spatial spacing layer on the surface of noble metals plays an important role in regulating the fluorescence intensity. We propose a method for regulating fluorescence intensity using the AgNPs@TA-FeIII composite nanostructured materials as the substrate and using characteristic fluorescence of graphene quantum dots as the detection signal. Tannins-FeIII (TA-FeIII) nanofilms were prepared with a one-step assembly method, which is simple, fast, green, and safe. This work is expected to help the application of polyphenol metal nanofilm technology in the field of surface enhanced fluorescence (SEF).

Plasmon-enhanced fluorescence of gold nanoparticle/graphene quantum dots for detection of Cr3+ ions

Graphene quantum dots (GQDs), fascinating semiconductors with stable photoluminescence (PL), have important potential applications in the fields of biology, medicine, and new semiconductor devices. However, it is still challenging to overcome the weak PL intensity. Here, we report a strategy for selective resonance enhancement of GQD fluorescence using gold nanoparticles (AuNPs) as plasmas. Interestingly, the addition of low concentration AuNP makes AuNP/GQDs exhibit significant fluorescence enhancement of 2.67 times in the visible range. The addition of high concentration AuNP leads to the formation of an excitation peak at 421 nm and selectively enhances certain radiation modes. We concluded that the main reason for the selective enhancement of PL intensity in high concentration AuNP is the transfer of generous hot electrons at high energy states from AuNP to GQD and relaxation to the ground state. The electron resonance of low concentration AuNP transfers to GQD and relaxes to lower energy levels, exhibiting an overall enhancement of PL intensity. We apply it for detection of the heavy metal ion Cr3+, and verify that it has a correlation coefficient of 97.36%. We believe AuNP/GQDs can be considered excellent candidates for heavy metal detection and high fluorescence bio-imaging.

Fluorescence Sensing Mechanisms of Versatile Graphene Quantum Dots toward Commonly Encountered Heavy Metal Ions.

Graphene quantum dots (GQDs) have received tremendous attention as fluorescent probes for detection of diverse heavy metal ions (HMIs). Nevertheless, the fluorescence sensing mechanisms of versatile GQDs with respect to different HMIs remain elusive. Herein, the fluorescence sensing behaviors and mechanisms of GQDs with amino and carboxyl groups toward commonly encountered Cr6+, Fe3+, Cu2+, Cr3+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+, and Hg2+ under different pH conditions are systemically explored. The results show that the fluorescence of GQDs can be enhanced by Zn2+/Cd2+ and quenched by other HMIs at pH 5.8, while it can be enhanced by HMIs except Cr6+/Fe3+/Cu2+ at pH 2.0. Systematic studies verify that the fluorescence quenching/enhancing is mediated by the synergistic effect of the inner filter effect (IFE) and the photoinduced electron transfer (PET) or metal orbital-controlled chelation-quenched/enhanced fluorescence (CHQF/CHEF) effect. The strong and weak IFEs of Cr6+/Fe3+ and Cr3+/Cu2+, respectively, are one of the reasons for the fluorescence quenching, while other HMIs have no IFE. Moreover, the PET effect caused by the interaction of GQDs with Hg2+ at pH 5.8 and the CHQF/CHEF effect caused by the interaction of GQDs with other HMIs are also crucial for fluorescence quenching/enhancing. The findings suggest that the pH condition, the existing forms of functional groups on GQDs, and the complexation states of HMIs in aqueous systems dominate the PET and CHQF/CHEF effects. The elucidating of the fluorescence sensing mechanisms of GQDs toward different HMIs paves the way for developing versatile sensing platforms for monitoring of HMI contamination.

A Curated Graphene Quantum Dot-Porphyrin-Based Photosensitizer for Effective Singlet Oxygen Generation through Energy Transfer.

Porphyrin-based photosensitizers are proven generators of reactive oxygen species (ROS), such as singlet oxygen, and used as anti-cancer therapeutic agents. However, most of these compounds suffer from potential drawbacks due to limited photostability, hydrophobicity, aggregation propensity, and low cellular uptake. Ultrasmall fluorescent graphene quantum dots (GQDs) have emerged as the next-generation carriers for drugs and have gained reputation in the pharmaceutical domain. Considering the various limiting factors in porphyrin-based ROS generation and cellular internalization, here, we have developed a method to generate tetrakis(m-nitrophenyl) porphyrin (TNPP)-GQD exciplexes. This allows resonance energy transfer (RET) from GQDs to TNPP. The calculated overlap integrals for GQD-TNPP and AGQD-TNPP (1.001 × 1018 and 1.257 × 1017 M-1 cm-1 nm4, respectively) assured 95 and 71% energy transfer. The optimum donor-acceptor distances in these couples are 59.82 and 62.65 Å, respectively, which yielded the rate constant of RET as 4.09 and 0.56 ns-1, respectively. The efficient RET helped in subsequent generation of singlet oxygen. The singlet oxygen quantum yields (SOQY) of around 0.435 and 0.464 for GQD-TNPP and AGQD-TNPP, respectively, are comparable to those of different porphyrin derivatives where the SOQY ranges from 0.55 to 0.70 when used with Triton X-100. The data show that non-conjugated amine- and amide-functionalized GQDs (AGQDs) are better candidates in this case because of the special properties of the amine groups. The systems could be excited at 450 nm for FRET, which favors biological usage.

Sensitive determination of naftazone using carbon quantum dots nanoprobe by fluorimetry and smartphone-based techniques

A simple, fast, and direct mix-and-read spectrofluorimetric method has been developed for the sensitive determination of naftazone (NFZ) utilizing graphene quantum dots (GQDs) as a greener and highly luminescent nanosensor. NFZ effectively quenches the strong fluorescence of GQDs at λex/λem of 350/440 nm via the inner filter effect mechanism. The nanosensor exhibits excellent linearity for NFZ over the concentration range of 0.46 to 186 μM with a limit of detection of 0.04 μM. The proposed method was validated for the successful determination of NFZ in tablets and on manufacturing equipment surfaces with good % recoveries of 98.4–101.6 and 96.3 – 102.2%, respectively. Furthermore, an integrated smartphone-based reader has been implemented and successfully applied for the determination of NFZ. The smartphone-based reader consists of a 365 nm UV torch as an excitation source, a smartphone for recording images, and smartphone-powered image analysis software for signal interpretation, together with a paper-based analytical device (PAD) utilizing filter paper as a substrate and correction fluid as a barrier for creation of detection zones. This smart platform showed excellent sensitivity with a limit of detection down to 0.12 nmol/zone, and it could be used for in-site determination of NFZ, especially for the limited resources laboratories.

Highly fluorescent graphene quantum dots as “turn off–on” nanosensor for detecting toxic metal ions to organic pollutant

Highly fluorescent graphene quantum dots as “turn off–on” nanosensor for detecting toxic metal ions to organic pollutant

Graphene Quantum Dots Derived from Honey and Mangostin as Sustainable Materials to Construct Fluorescence Turn‐On Molecular Switches for Pesticide Detection

AbstractExtensive use of pesticides in agriculture can lead to environmental pollution and potentially adverse health effects. A fluorescence Turn‐On molecular switch, derived from naturally occurring α‐mangostin (MN), isolated from the pericarp of mangosteen fruit and Graphene Quantum Dots (GQDs) synthesized from honey, was developed for the detection of carbofuran‐an organic toxic carbamate pesticide. GQDs derived from honey shows a strong fluorescence emission centered at 430 nm, which was efficiently quenched by the addition of MN. The quenching of fluorescence of GQDs by the addition of MN (OFF state) and the regaining of quenched fluorescence of GQDs‐MN system (ON state) upon the addition of the pesticide carbofuran was utilized as a detection strategy for the toxic pesticide carbofuran.

Graphene Quantum Dots Incorporated UiO-66-NH 2 Based Fluorescent Nanocomposite for Highly Sensitive Detection of Quercetin

Quercetin can help with a variety of health problems. Most methods for measuring quercetin in biological fluids are characterized by low sensitivity and selectivity. The employment of metal–organic frameworks in sensor applications with carbon-based materials ushers in a new era. In this study, blue fluorescent graphene quantum dots (GQDs) embedded in a UiO-66-NH₂ metal–organic framework-based nanoprobe (GQDs@UiO-66-NH₂) were constructed for quercetin sensing. Initially, maize husk was used to produce blue fluorescent GQDs, whereas zirconium tetrachloride and 2-aminoterephthalic acid were used to synthesize extremely luminous UiO-66-NH₂. The addition of quercetin to GQDs@UiO-66-NH₂ leads to fluorescence dampening due to the adsorption potential of UiO-66-NH₂. The complexation of zirconium ions with the 3-OH and 4-C＝O functionalities of quercetin resulted in fluorescence quenching. The sensor has a linear concentration range and limit of detection for quercetin of 50–500 and 2.82 ng/mL, respectively. The nanoprobe’s usefulness for quercetin detection was then validated by a selectivity investigation in the presence of interfering chemicals. Furthermore, the percentage relative standard deviations were 4.20% and 2.90%, respectively, indicating great stability and repeatability. Fluorescence “Turn-On–Off” nanoprobes provide a simple, quick, sensitive, and selective method for monitoring quercetin.

Water-soluble graphene quantum dot‐based polymer nanoparticles with internal donor/acceptor heterojunctions for efficient and selective detection of cancer cells

We present a new, insightful donor–acceptor (D-A) energy transfer-based strategy for the preparation and development of water-soluble multifunctional pH-responsive heterojunction nanoparticles. Hydrophilic tertiary amine-grafted polythiophene (WPT) as a donor and blue fluorescent graphene quantum dots (GQD) as an acceptor spontaneously form co-assembled nanoparticles that function as a highly pH-sensitive and efficient biosensor appropriate for the detection of cancer cells. These WPT/GQD nanoparticles exhibit a number of unique physical characteristics—such as broad-range, tunable GQD-loading contents and particle sizes, extremely low cytotoxicity in normal and cancer cells, and highly sensitive pH-responsiveness and rapid acid-triggered fluorescent behavior under aqueous acidic conditions. We show these features are conferred by self-aggregation of the GQD within the nanoparticles and subsequent aggregation-induced fluorescence of GQD after disassembly of the nanoparticles and dissociation of the D-A interactions under acidic conditions. Importantly, in vitro fluorescence imaging experiments clearly demonstrated the WPT/GQD nanoparticles were gradually taken up into normal and cancer cells in vitro. Selective formation of GQD aggregates subsequently occurred in the acidic microenvironment of the cancer cells and the interior of the cancer cells exhibited strong blue fluorescence; these phenomena did not occur in normal cells. In contrast, pristine WPT and GQD did not exhibit cellular microenvironment-triggered fluorescence transitions in cancer or normal cell lines. Therefore, this newly discovered water-soluble heterojunction system may represent a strongly fluorescent highly pH-sensitive bioprobe for rapid detection of cancer cells.

Solid-Phase Pyrolysis Synthesis of Highly Fluorescent Nitrogen/Sulfur Codoped Graphene Quantum Dots for Selective and Sensitive Diversity Detection of Cr(VI).

In this study, a simple one-step solid-phase pyrolysis synthesis procedure was employed to prepare N and S codoped highly fluorescent graphene quantum dots (N/S-GQDs). The as-synthesized quantum dot showed λexcitation-dependent blue fluorescence (FL) emission with a relative quantum yield of about 22% and displayed good biocompatibility, high water dispersibility, and excellent stability under extreme conditions (i.e., ionic strength, pH, and temperature). The potential applicability of the as-synthesized quantum dot was tested by employing solution- and paper-based FL detection modes for Cr(VI) detection. The proposed solution- and paper-based FL sensors showed lower limit of detection (LOD) values of 0.01 and 0.4 μM, respectively. The as-constructed paper- and solution-based FL sensors proved the feasibility of sensitive, cost-effective, and on-site detection of Cr(VI).

Lubrication behavior of fluorescent graphene quantum dots hybrid polyethylene glycol lubricant

Graphene quantum dots (GQDs) with a lattice structure and the size of 1.8–3.4 nm were prepared by a simple hydrogen peroxide-containing hydrothermal reaction method using graphene oxide (GO) as a precursor. The hydroxyl group with the cutting effect can cut GO into GQDs with a large number of oxygen-containing functional groups. As polyethylene glycol (PEG) additives, the photoluminescence (PL) properties of well-dispersed GQDs can reflect and monitor the lubrication state between the sliding interfaces because partial GQDs contributed to low friction/wear and occurred the structural transformation. As-modulated hybrid PEG with 0.04 wt% GQDs shows excellent wear reduction ability, and the wear rate is reduced by 40.5%. The formation of a dense disordered carbon film on the sliding surfaces and iron/iron oxide debris with attached GQDs between sliding interfaces contribute to filling the pits and hindering the direct contact of friction pairs, thereby enhancing the wear resistance. This work illustrates that GQDs as a polar lubricant additive have a great application potential in lubrication regulation and monitoring.

Double-enhanced fluorescence of graphene quantum dots from cane molasses via metal and PEG modification for detecting metal ions and pigments

Lead-doped graphene quantum dots modified with polyethylene glycol (PEG-Pb-GQDs) were one-step synthesized using biomass cane molasses as a green carbon source through simple hydrothermal method. The quantum yield (QY) of the PEG-Pb-GQDs can be as high as 30.31%, which is approximately three times that of graphene quantum dots (GQDs) without any modified, indicating that the doping of lead ions and the modification of polyethylene glycol (PEG) can realize the double-sided fluorescence enhancement effect. The as-prepared PEG-Pb-GQDs also exhibit stronger fluorescence, better stability and dispersion compared with lead doped graphene quantum dots (Pb-GQDs). The quasi-spherical PEG-Pb-GQDs were characterized by Fourier transforms infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) to prove the success of lead ions (Pb2+) doping and PEG passivation modification. Multiple metal ions including Fe3+, Cu2+, Ag+, Co2+, Ni2+, Pb2+ and Mn2+ and benzene sulfonic acid pigments including lemon yellow, quinoline yellow and sunset yellow can be detected by PEG-Pb-GQDs. Among the seven responsive metal ions, Fe3+ can be selectively detected under the condition of EDTA and thiourea as masking agent with a limit of detection (LOD) of 0.29 μM for PEG-Pb-GQDs. Correspondingly, Cu2+ and Ag + can also be selectively detected by PEG-Pb-GQDs under appropriate masking agents. The benzene sulfonic acid pigments including lemon yellow, quinoline yellow and sunset yellow can also be selectively detected and the LOD were 0.067, 0.073 and 0.097 μM, respectively. The quenching mechanisms were dynamic quenching for Fe3+, static quenching for Cu2+ and Ag+ and static quenching and fluorescence resonance energy transfer (FRET) for pigments.

One-step synthesis of graphene quantum dots by laser-induced polymer

In order to achieve a low-cost, simple, fast, and green preparation method of graphene quantum dots (GQDs), a method for one-step preparation of GQDs by laser-induced polyimide powder was proposed. By controlling the laser parameters and using low-cost precursor material polyimide (PI) powder, a bright blue fluorescent GQDs solution was successfully prepared, and the whole experimental process was simulated by ReaxFF molecular reaction dynamics. The results show that the GQDs solution with blue fluorescent can be prepared by laser-induced PI power in one step. The scraped black matter contained GQDs. After the samples were tested by UV–vis, PL, TEM, and Raman, the prepared GQDs had an average particle size of 6.14 nm, a quantum yield of about 11.4%, and stable fluorescence properties. The whole process of the proposed method can be carried out at ambient temperature without any other chemical reagents or complicated subsequent processing, and has the advantages of simplicity, rapidity, environmental protection, and low cost, which not only provides a new reference for the green synthesis of quantum, but also has the potential for large-scale production.

Optical Visualization of Red-GQDs' Organelles Distribution and Localization in Living Cells.

Recently, there has been a rapidly expanding interest in a new nanomaterial, graphene quantum dots (GQDs), owing to its profound potential in various advanced applications. At present, the study of GQDs mainly focuses on the new synthesis methods and surface modification. However, revealing the intracellular distribution of GQDs is currently not available, limiting in-depth understanding of its biological regulatory mechanism. To fill up this gap, the visualization study of red fluorescent graphene quantum dots (Red-GQDs) is helpful to clarify their subcellular distribution and metabolism in living cells system. Here, in this study, two-photon laser confocal microscopy was used to deeply analyze the uptake and subcellular distribution of Red-GQDs by HeLa cells at different concentrations and times through visual observation and discussed the effect of Red-GQDs on the metabolic of HeLa cells. The results indicated that Red-GQDs could be well-absorbed by HeLa cells and further revealed the differential distribution of Red-GQDs in different organelles (lysosomes and mitochondria) in a time-dependent manner. In addition, we confirmed that Red-GQDs significantly affect cell biological functions. Low concentrations of Red-GQDs are related to the autophagy pathway of cells, and high concentrations of Red-GQDs can induce ferroptosis in cells and promote the secretion of cellular exosomes. In the present study, the distribution and metabolic pathways of Red-GQDs in the subcellular structure of cells were characterized in detail through visual analysis, which can bring positive reference for the application of Red-GQDs in the future.

Preparation of Graphene Quantum Dots by Visible-Fenton Reaction and Ultrasensitive Label-Free Immunosensor for Detecting Lipovitellin of Paralichthys Olivaceus.

The increasing levels of environmental estrogens are causing negative effects on water, soil, wildlife, and human beings; label-free immunosensors with high specificities and sensitivities are being developed to test estrogeneous chemicals in complex environmental conditions. For the first time, highly fluorescent graphene quantum dots (GQDs) were prepared using a visible-Fenton catalysis reaction with graphene oxide (GO) as a precursor. Different microscopy and spectroscopy techniques were employed to characterize the physical and chemical properties of the GQDs. Based on the fluorescence resonance energy transfer (FRET) between amino-functionalized GQDs conjugated with anti-lipovitellin monoclonal antibodies (Anti-Lv-mAb) and reduced graphene oxide (rGO), an ultrasensitive fluorescent “ON-OFF” label-free immunosensor for the detection of lipovitellin (Lv), a sensitive biomarker derived from Paralichthys olivaceus for environmental estrogen, has been established. The immunosensor has a wide linear test range (0.001–1500 ng/mL), a lower limit of detection (LOD, 0.9 pg/mL), excellent sensitivity (26,407.8 CPS/(ng/mL)), and high selectivity and reproducibility for Lv quantification. The results demonstrated that the visible-Fenton is a simple, mild, green, efficient, and general approach to fabricating GQDs, and the fluorescent “ON-OFF” immunosensor is an easy-to-use, time-saving, ultrasensitive, and accurate detection method for weak estrogenic activity.

Promising energy transfer system between fuorine and nitrogen Co-doped graphene quantum dots and Rhodamine B for ratiometric and visual detection of doxycycline in food

A novel sensor based on dual emissive fluorescent graphene quantum dots is developed for a rapid, selective, sensitive and visual detection of doxycycline (DOX). The ratiometric fluorescent probe is designed by grafting fluorescent group (Rhodamine B, RhB) on F, N-doped graphene quantum dots (FNGQDs). In the presence of DOX, the fluorescence at 466 nm is remarkably quenched due to inner filter effect and fluorescence resonance energy transfer, whereas the peak at 592 nm is attenuated slightly due to the energy transfer in the emission peaks of FNGQDs and RhB functional group. The sensor shows good linear relationship from 0.04 to 100 µM with a low detection limit of 40 nM. Furthermore, the flexible solid-state fluorescent sensing platform is used for detecting DOX in milk, pork and water samples. Therefore, this dual-emission FGQD-RhB can be used as a high-performance fluorescent and visual sensor for food safety and environmental monitoring.