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Highly Luminescent Nitrogen-Doped Carbon Dots as “Turn-On” Fluorescence Probe for Selective Detection of Melamine
摘要： In our work, a new and simple method for selective detection of melamine is established by developing a "turn-on" fluorescence probe based on nitrogen-doped carbon dots (N-CQDs). The N-CQDs have been facilely prepared by one-step simple hydrothermal reaction and it is highly luminescent that with 51% fluorescent quantum yield. In this sensor, the fluorescent intensity of N-CQDs was found to be efficient quenched by Fe3+, upon addition of melamine the fluorescent intensity of N-CQDs-Fe3+ could gradually recover, which may because of the competitive combination of Fe3+ and melamine leading to the departure of Fe3+ from the N-CQDs' surface. Under optimum conditions, the fluorescence intensity has a good liner relationship with melamine in the range of 2.0 to 290 μM. The probe displayed good sensitivity toward melamine with a lower detection limit of 0.67 μM. In addition, this fluorescence probe has been used for the analysis of milk samples, demonstrating the fluorescence probe has potential application in the detection of melamine.
关键词： selective detection,turn-on fluorescence probe,melamine,carbon quantum dot
更新于2025-09-23 15:23:52
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Off-on fluorescent switching of boron-doped carbon quantum dots for ultrasensitive sensing of catechol and glutathione
摘要： A signal-off-on probe of B-doped carbon quantum dot (B-CQD) is developed for ultrasensitive detection of catechol (CC) by fluorescence quenching and glutathione (GSH) by fluorescence recovering without any auxiliary of biomolecules or labeled materials. In this sensing system, the B-CQDs with a high quantum yield of 42% are prepared via a facile hydrothermal method with precursors of citric acid as C source and sodium tetraphenylborate as B source. The microstructure and fluorescence stability of the B-CQDs are investigated. Under the optimum conditions, the B-CQDs are highly sensitive for detecting CC with a linear range of 1-50 nM and a detection limit of 0.25 nM under a typical signal-to-noise ratio of 3 to 1 (S/N=3), and for sensing GSH with a linear range of 2-100 nM and a detection limit of 0.5 nM (S/N=3). Meanwhile, the developed B-CQDs show a good selectivity for sensing CC and GSH under high concentrations of interfering substances, such as biological thiols and amino acids. The B-CQDs are successfully applied to determination of CC in river water and GSH in human serum, where the recoveries are 103.3%-106.0% and 99.8%-106.3% for CC and GSH sensing, respectively. The signal-off-on mechanisms of the B-CQDs sensor are discussed.
关键词： Glutathione,B-doped carbon quantum dot,Sensitivity,Fluorescent sensing,Catechol
更新于2025-09-23 15:19:57
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Influence of Group Modification at the Edges of Carbon Quantum Dots on Fluorescent Emission
摘要： We present a detailed investigation on the effect of functional group modulation at the edges of carbon quantum dots (CQDs) on the fluorescence from the CQDs. The CQDs attached by N, S, and P elements are synthesized via pyrolysis of a mixture of citric acid and NH3H2O, H2SO4, and H3PO4, respectively. Thus, part of –COOH at the edges of CQDs can be converted into –C=O and functional groups such as –NH2, –SO2, –HSO3, and –H2PO4 can connect to the carbon bonds. We find that the formation of the N/S/P-CQDs can reduce the amount of –COOH that attaches to the edges of sp2-conjugated π-domains located at centers of these CQDs. This effect can result in the reduction of the non-radiative recombination for electronic transition in these CQDs. As a result, the quantum yield (QY) for fluorescence from the CQDs can be efficiently enhanced. We demonstrate experimentally that the QYs for N/S/P-CQDs can reach up to 18.7%, 29.7%, and 10.3%, respectively, in comparison to 9% for these without functional group modulation. This work can provide a practical experimental approach in improving the optical properties of fluorescent CQDs.
关键词： Functional group modulation,Carbon quantum dot,Fluorescent emission
更新于2025-09-23 15:19:57
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Synthesis and Photocatalytic Activity of Fe3O4–WO3–CQD Multifunctional System
摘要： In this work, superparamagnetic Fe3O4 nanocrystalline was prepared by using citric acid as an additive and co-precipitation method. The Fe3O4–WO3–carbon quantum dot (CQD) metal oxide porous structure was constructed, characterized and analyzed. When the amount of citric acid added was 22.7 wt%, the specific saturation magnetization of Fe3O4 nanocrystals was 52.567 emu/g, and the Fe3O4–WO3 composite structure was agglomerated into spheroids having a diameter of about 200 nm. The constructed Fe3O4–WO3–CQD metal oxide porous structure has a specific surface area of 166.78 m2/g. In the experiment of adsorption and degradation of rhodamine B solution (20 mg/L), the decolorization rate of the dye by Fe3O4–WO3–CQD system was 54.42% after 60 min of dark treatment. After 240 min of photocatalysis, the dye decolorization rate increased by 14.17% to 65.56%. This shows that the photocatalytic performance of the sample was improved after the compounding process. The results provided that Fe3O4–WO3–CQD composite structure has great application potential in the field of photo-catalytic degradation of organic pollutants.
关键词： Photocatalytic,Fe3O4 nanoparticles,Carbon quantum dot (CQD),WO3
更新于2025-09-19 17:15:36
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Development of sulfur doped carbon quantum dots for highly selective and sensitive fluorescent detection of Fe2+ and Fe3+ ions in oral ferrous gluconate samples
摘要： Sulfur-doped carbon quantum dots (S-CQDs) with stable blue fluorescence were synthesized through a facile one-step hydrothermal method by using ascorbic acid and thioglycolic acid as carbon and sulfur sources. The prepared S-CQDs exhibited a sensitive and selective response to Fe3+ ions in comparison with Fe2+ and other metal ions, In the presence of adequate H2O2, Fe2+ was completely transformed to Fe3+ that is the determinable form of iron ions, and the difference in the change of the fluorescence intensity of S-CQDs before and after adding H2O2 was used for detection of Fe2+ ions, respectively. Under the optimum experimental conditions, the fluorescence intensity of S-CQDs gradually decreased with increasing of Fe3+ concentration ranging from 0 to 200 mM. Good linearity was achieved over the range of 0-200 mM. The detection limit of the developed method was 0.050 mM for Fe3+. The recoveries of Fe2+ spiked in real samples ranged from 98.2% to 112.4%. Finally, the proposed S-CQDs integrated with Fenton system was applied to the detection of Fe2+ and Fe3+ ions in oral ferrous gluconate samples, which presents potential applications in the speciation and determination of Fe2+ and Fe3+ ions in complex samples.
关键词： Fluorescence quenching,Iron supplement,Iron,Sulfur co-doped,Carbon quantum dot
更新于2025-09-19 17:13:59
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Synthesis of Microwave-Assisted Fluorescence Carbon Quantum Dots Using Roasteda??Chickpeas and its Applications for Sensitive and Selective Detection of Fe3+ Ions
摘要： A simple method for the green synthesis of fluorescent carbon quantum dots (CQDs) has been developed by using roasted chickpea as carbon source in one-step without using any chemical. Interestingly, not only the carbon source of CQDs and the whole synthesis procedure are environmentally friendly, but also the synthesized CQDs have shown many advantageous properties such as high fluorescence intensity, excellent photostability, and good water solubility. CQDs which were firstly synthesized from roasted–chickpeas by a microwave-assisted pyrolysis have been characterized using UV-vis absorption spectroscopy, fluorescence spectroscopy, fourier transform infrared spectroscopy (FTIR) spectroscopy, X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). In addition, the details of the structure have been revealed by the electron diffraction (SAED; selected-area electron diffraction) method based on the TEM images. The synthesized CQDs emits blue fluorescence under UV light (at 365 nm). A microwave oven (350 watts) was used to prepare CQDs in 120 s. The effect of various metal ions on the fluorescence intensity of CQDs was investigated in order to determine its utality in the detection of metal ions. It was determined that 1.38 mg/L of Fe3+ ions quenched the fluorescence intensity of the CQDs by 65%. The linear range is observed between 11.25 and 37.50 μM with limit of detection (LOD) and limit of quantification (LOQ) of 2.74 μM and 8.22 μM, respectively. CQDs which are highly selective and sensitive for Fe3+ ions was used to determine Fe3+ ions in certified reference material (CRM-SA-C). Fe3+ ions concentration was determined with precision values of more than 95% as intra-day and inter-day relative standard deviation (RSD%) is 5 at room temperature.
关键词： Green-synthesis,Roasted–chickpea,Microwave,Fluorescence,Fe3+ detection,Carbon quantum dot
更新于2025-09-19 17:13:59
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Microfluidic synthesis of PLGA/carbon quantum dot microspheres for vascular endothelial growth factor delivery
摘要： In this study, vascular endothelial growth factor (VEGF) loaded poly(D,L-lactide-co-glycolide) (PLGA) – carbon quantum dot microspheres were produced using micro?uidic platforms. The microcapsules were fabricated in ?ow-focusing geometry with a biphasic ?ow to generate solid/oil/water (s–o–w) droplets. To avoid any damage to protein functional and structural stability during the encapsulation process, the VEGF was PEGylated. The produced microspheres were intact and highly monodisperse in size (CV < 5%). Furthermore, microspheres in a size range of 16–36 mm were achieved by adjusting the ?ow ratio parameter. The encapsulation e?ciency, release pro?le, and bioactivity of the produced microparticles were also studied. The loading e?ciency of PEGylated VEGF in the microparticles was varied from 51–69% and more than 90% of PEGylated VEGF was released within 28 days. Furthermore, the release of VEGF was indirectly monitored by carbon quantum dots. The present monodisperse and controllable VEGF loaded microspheres with reproducible manner could be widely used in tissue engineering and therapeutic applications.
关键词： PLGA,vascular endothelial growth factor,carbon quantum dot,drug delivery,Micro?uidic synthesis
更新于2025-09-16 10:30:52
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Bottom-Up Synthesis of Nitrogen and Oxygen Co-Decorated Carbon Quantum Dots with Enhanced DNA Plasmid Expression
摘要： In this paper, a bottom-up hydrothermal route is reported for the synthesis of oxygen and nitrogen co-decorated carbon quantum dots (CQDs) using ammonium hydrogen citrate (AHC) as a single precursor. DLS data approved the formation of 4.0 nm (average size) CQDs. XRD pattern shows the interlayer spacing (002) of 3.5 ? for CQDs, which is exactly the same as that of crystalline graphite. XPS and FTIR spectra verified the formation of oxygen and nitrogen functional groups on the CQDs surface. Co-decorated carboxyl, hydroxyl and amine groups on the CQDs surfaces make them as promising polyelectrolyte for gene delivery. Toxicity assay showed a survival rate of 70% under different incubation times and up to 500 μg/mL. The highly water-soluble, stable fluorescence and low toxic CQDs increased the gene expression of DNA plasmid in E. coli bacteria 4-fold more than the control group.
关键词： biocompatible,Gene delivery,carbon quantum dot,transformation
更新于2025-09-16 10:30:52
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Exciton Coherence Length and Dynamics in Graphene Quantum Dot Assemblies
摘要： Exciton size and dynamics were studied in assemblies of two well-defined graphene quantum dots of varying size: hexabenzocoronene (HBC), where the aromatic core consists of 42 C atoms, and carbon quantum dot (CQD) with 78 C atoms. The synthesis of HBC and CQD were achieved using bottom-up chemical methods, while their assembly was studied using steady-state UV/vis spectroscopy, X-ray scattering, and electron microscopy. While HBC forms long ordered fibers, CQD was found not to assemble well. The exciton size and dynamics were studied using time-resolved laser spectroscopy. At early times (~100 fs), the exciton was found to delocalize over ~1?2 molecular units in both assemblies, which reflects the confined nature of excitons in carbon-based materials and is consistent with the calculated value of ~2 molecular units. Exciton?exciton annihilation measurements provided the exciton diffusion lengths of 16 and 3 nm for HBC and CQD, respectively.
关键词： Time-resolved Laser Spectroscopy,Graphene Quantum Dot,Hexabenzocoronene,Exciton,Carbon Quantum Dot
更新于2025-09-12 10:27:22
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Enhanced CH4 selectivity in CO2 photocatalytic reduction over carbon quantum dots decorated and oxygen doping g-C3N4
摘要： Graphitic carbon nitride (g-C3N4, CN) exhibits inefficient charge separation, deficient CO2 adsorption and activation sites, and sluggish surface reaction kinetics, which have been recognized as the main barriers to its application in CO2 photocatalytic reduction. In this work, carbon quantum dot (CQD) decoration and oxygen atom doping were applied to CN by a facile one-step hydrothermal method. The incorporated CQDs not only facilitate charge transfer and separation, but also provide alternative CO2 adsorption and activation sites. Further, the oxygen-atom-doped CN (OCN), in which oxygen doping is accompanied by the formation of nitrogen defects, proves to be a sustainable H+ provider by facilitating the water dissociation and oxidation half-reactions. Because of the synergistic effect of the hybridized binary CQDs/OCN addressing the three challenging issues of the CN based materials, the performance of CO2 photocatalytic conversion to CH4 over CQDs/OCN-x (x represents the volume ratio of laboratory-used H2O2 (30 wt.%) in the mixed solution) is dramatically improved by 11 times at least. The hybrid photocatalyst design and mechanism proposed in this work could inspire more rational design and fabrication of effective photocatalysts for CO2 photocatalytic conversion with a high CH4 selectivity.
关键词： carbon quantum dot,photocatalytic,graphitic carbon nitride (g-C3N4),oxygen doping,CO2 reduction
更新于2025-09-12 10:27:22