Recent Advances in Functionalized Carbon Quantum Dots Integrated with Metal-Organic Frameworks: Emerging Platforms for Sensing and Food Safety Applications

Abstract

Carbon quantum dots (CQDs), with their excellent photoluminescence, tunable surface chemistry, and low toxicity, have emerged as versatile nanomaterials in sensing technologies. Meanwhile, metal-organic frameworks (MOFs) possess exceptionally porous architectures and extensive surface areas, and tunable functionalities ideal for molecular recognition and analyte enrichment. The synergistic integration of CQDs and MOFs has significantly expanded the potential of hybrid materials with enhanced selectivity, sensitivity, and multifunctionality. While several reviews have addressed QD/MOF systems broadly, this review offers a focused and updated perspective on CQDs@MOFs composites specifically tailored for food safety and environmental sensing applications. This review provides a comprehensive analysis of recent advances in the design, synthesis, and surface functionalization of these hybrids, emphasizing the mechanisms of interaction, photophysical behavior, and performance advantages over conventional sensors. Special attention is given to their use in detecting food contaminants such as heavy metals, pesticides, antibiotics, mycotoxins, pathogens, and aromatic compounds. Key strategies to enhance stability, selectivity, and detection limits are highlighted, and current challenges and future directions for practical deployment are critically discussed.

Keywords: CQDs@MOFs; antibiotics; aromatic compounds; heavy metals; mycotoxins; pathogens; pesticides.

Figure 1

Timeline of CQDs@MOFs in sensing and food detection applications.

Figure 2

(I) Synthesis of CuO/Cu₂O-CdS/HgS and PEC sensor for Hg²⁺ detection. (II) SEM images (A,B), histogram showing the statistical size distribution (C), TEM image (D), HRTEM image (E), lattice spacing images (F), and corresponding elemental mapping images of CuO/Cu₂O-CdS QDs (G). (III) Real sample analysis using the PEC sensor for Hg²⁺ detection. (IV) Proposed charge transfer mechanisms at ITO/CuO/Cu₂O-CdS and ITO/CuO/Cu₂O-CdS/HgS electrodes. Reprinted with permission from [5]. Copyright @2024 Elsevier Ltd.

Figure 3

(I) Schematic illustration of paraoxon degradation and detection by Fe-CD/MOF-808 (Route 1) and parathion by Fe-CD@MOF-808 (Route 2). (II) (a) Fluorescence spectra of Fe-CDs@MOF-808 before and after incubation with parathion in the dark and under 365 nm LED irradiation. (b) Degradation rate of parathion catalyzed by Fe-CDs@MOF-808 in the presence of different reactive oxygen species (ROS) scavengers. (c) GC-MS analysis of degradation products of parathion. (d) Fluorescence spectra of Fe-CDs@MOF-808 incubated with varying concentrations of parathion under 365 nm LED irradiation. (e) Calibration plot of (F₀-F)/F₀ at 425 nm versus parathion concentration. (f) Selectivity and anti-interference study of Fe-CDs@MOF-808 for parathion detection. (III) (a) Schematic representation of organophosphate (OP) detection in pakchoi. (b) Fluorescence images showing Fe-CDs/MOF-808 with pakchoi in the absence (left) and presence (right) of paraoxon, confirming the complete degradation of paraoxon in pakchoi. (c) Fluorescence spectra of Fe-CDs/MOF-808 with pakchoi in the presence of paraoxon at different time intervals. (d) Fluorescence spectra of Fe-CDs/MOF-808 with pakchoi after being removed from the solution for 5 min. Reproduced with permission from [11]. Copyright@ 2023 Elsevier B.V.

Figure 4

(A) Schematic representation of the preparation process for Eu/UiO-67b and CDs@Eu/UiO-67b, (B) sensing mechanism for OFL and TC detection, and (C) visual detection application using a smartphone. (D) XPS survey spectra with inset images showing corresponding photographs. (E) and (F) display the fitting curves correlating OFL concentration with the color change ratio (R + G)/2B in solution and hydrogel, respectively. Reproduced with permission from [20]. Copyright@ 2024 Elsevier B.V.

Figure 5

(I) Schematic illustration of the MP QDs@ZIF-8-based molecular imprinting ECL sensor for AFB1 detection in corn samples. (A) Synthesis process and proposed ECL reaction mechanism of MP QDs@ZIF-8 nanocomposites. (B) Signal responses of the AFB1-imprinted ECL sensor throughout the detection process. (II) (A–I) TEM and HRTEM images, size distribution, XRD patterns of simulated, XPS full spectra, and high-resolution XPS spectra of ZIF-8, MP QDs, and MP QDs@ZIF-8. (III) (A–G) Optical images of MP QDs and MP QDs@ZIF-8, along with fluorescence intensity variations over time, decay curves, and time-dependent evolution of MP QDs and MP QDs@ZIF-8 composites. Fluorescence and ECL wavelength spectra of MP QDs@ZIF-8 with optical filters, ECL-potential curve, and ECL-time responses of MP QDs@ZIF-8 and MP QDs. A schematic representation of the proposed ECL reaction mechanism is also included. (IV) (A–D) EIS plots and CV curves of MP QDs@ZIF-8/GCE and AFB1-imprinted MP QDs@ZIF-8/GCE, along with the ECL response of the proposed AFB1-imprinted sensor in PBS containing 0.01 M TPrA. Additionally, an SEM image showcasing the surface morphology of the AFB1-imprinted ECL sensor is presented. (V) (A–D) ECL signals of the eluted AFB1-imprinted sensor after rebinding in various concentrations of AFB1 solutions, along with the calibration curve for AFB1 detection. ΔI_ECL responses of the eluted AFB1-imprinted ECL sensor following incubation in blank solution, 10 ng/mL of DON, OTB, ZEN, FB1, or OTA as interferences, and 1 ng/mL AFB1 solution as a target, including a mixture of all interferences with AFB1. Additionally, the ECL response of the imprinted sensor incubated with 0.1 pg/mL AFB1 is shown after continuous CV scans for 17 cycles. Reprinted with permission from [8]. Copyright @2022 Elsevier Ltd.

Figure 6

(I) Synthesis of the GQDs/Cu-MOF nanocomposite, (II) development of a GQDs/Cu-MOF nanocomposite-based ratiometric electrochemical aptasensor for detecting S. aureus in tap water, milk, Lonicera japonica, urine, and the Zhangjiang River. (III) DPV responses for varying concentrations of E. coli O157:H7 (A), B. cereus (C), and L. monocytogenes (E): a to i represent 5.0 × 10⁰, 5.0 × 10¹, 5.0 × 10², 5.0 × 10³, 5.0 × 10⁴, 5.0 × 10⁵, 5.0 × 10⁶, 5.0 × 10⁷, and 5.0 × 10⁸ CFU·mL⁻¹. DPV responses for different concentrations of Y. enterocolitica (G): a to h represent 1.0 × 10¹, 1.0 × 10², 1.0 × 10³, 1.0 × 10⁴, 1.0 × 10⁵, 1.0 × 10⁶, 1.0 × 10⁷, and 1.0 × 10⁸ CFU·mL⁻¹. A linear correlation between I_Cu-MOF/I_S2-Fc and the logarithm of CFU·mL⁻¹ was observed for foodborne pathogens: E. coli O157:H7 (B), B. cereus (D), L. monocytogenes (F), and Y. enterocolitica (H). Reproduced with permission from [76]. Copyright@ 2024 Elsevier B.V.

Figure 7

(I) Synthesis process of the N-GQDs/Fe₃O₄@SiO₂/IRMOF-1/MIP nano-sorbent, and (II) the d-MSPE procedure for phenylurea extraction. (III) SEM images of IRMOF-1 (A,B) and N-GQDs/Fe₃O₄@SiO₂/IRMOF-1/MIP (C,D). TEM images of N-GQDs (E) and GQDs/MIP sorbent (F). Adsorption–desorption isotherms for N-GQDs/Fe₃O₄@SiO₂/IRMOF-1/MIP (G) and N-GQDs/Fe₃O₄@SiO₂/IRMOF-1/NIP (H) nano-sorbents. Reproduced with permission from [85]. Copyright@ 2023 Elsevier Inc.