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- 实验方案
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On-off-on fluorescent carbon dots from waste tea: Their properties, antioxidant and selective detection of CrO42?, Fe3+, ascorbic acid and L-cysteine in real samples
摘要： In this work, we reported an economical plant-based hydrothermal method for one-pot green synthesis of water-soluble carbon dots (Tea-CDs) by using waste tea extract as a carbon source. The synthesized Tea-CDs were characterized by UV-visible, fluorescence, FT-IR, TEM, XPS and XRD. The Tea-CDs were found to remove hydroxyl and superoxide anion radical in vitro. In addition, the Tea-CDs exhibited bright blue fluorescence under UV-light (λex=365 nm), and the fluorescence could be effectively quenched by CrO4 2- and Fe3+ ions. Meanwhile, the fluorescence of Tea-CDs-CrO4 2- and Tea-CDs-Fe3+ systems could be again easily recovered by ascorbic acid (AA) and L-cysteine (L-Cys). As an on-off-on fluorescent nano-sensor of the Tea-CDs, the sensitive detection of CrO4 2-, Fe3+, AA and L-Cys were all performed, showing that the good linear relationships between fluorescence intensity of Tea-CDs and concentration of all testing samples. Finally, the sensors successfully detected CrO4 2-, Fe3+, AA and L-Cys in commercially available real samples with satisfactory recovery ranges. The prepared sensors offer distinct advantages including low cost, simple handling, good sensitivity and high selectivity.
关键词： carbon dots,waste tea,L-cysteine,ascorbic acid,on-off-on fluorescent nano-sensor,metal ions
更新于2025-09-19 17:15:36
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Simultaneous determination of ascorbic acid, dopamine, and uric acid using graphene quantum dots/ionic liquid modified screen-printed carbon electrode
摘要： In this work, graphene quantum dots (GQDs) and ionic liquid (IL) modified screen-printed carbon electrode (GQDs/IL-SPCE) were introduced for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). GQDs were synthesized by directly pyrolyzing citric acid and then dropped onto the surface of IL-SPCE, which was prepared by screen-printing the mixture of IL and carbon ink on a portable substrate. UV-Vis spectrophotometry, fluorescence spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to characterize the synthesized GQDs and the modified electrodes. The GQDs/IL-SPCE exhibited excellent electrocatalytic activity for the oxidation of AA, DA, and UA in the mixture solution. Moreover, the anodic peak responses of these three analytes were also resolved into three well-defined peaks. Under the optimized conditions, the linear response ranges for AA, DA, and UA were 25 - 400 μM, 0.2 - 10 μM, and 0.5 - 20 μM, respectively, with low detection limits (σ/N = 3) of 6.64 μM, 0.06 μM, and 0.03 μM, respectively. The proposed sensor exhibited high sensitivity, low cost and successfully applied for the simultaneous detection of AA, DA, and UA in pharmaceutical products and biological samples.
关键词： Graphene quantum dots,Uric acid,Dopamine,Screen-printed carbon electrode,Ionic liquid,Ascorbic acid
更新于2025-09-19 17:13:59
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A portable non-enzyme photoelectrochemical ascorbic acid sensor based on BiVO4 electrode under 20?W LED light
摘要： BiOI film was electrodeposited deposited on fluorine doped tin oxide (FTO), then it was transformed into a nanoporous BiVO4 film by annealing at 420 ?C. The BiVO4/FTO electrode is used as photoelectrochemical (PEC) sensor to detect ascorbic acid (AA) for the first time. Under illumination of low power 20 W LED lamp, the current density of the sensor increases with the increase of AA concentration. The proposed PEC sensor exhibited a sensitive detection for AA in a wide range from 5 μM to 300 μM with a low detection limit of 1 μM (S/N=3) and sensitivity of 293 μA mM-1 cm-2. A portable AA detection device was constructed with a 20W LED lamp as the light source, BiVO4/FTO electrode as an anode, Pt as a cathode, and ammeter as a photoelectric signal receiver. The concentration of AA detected by this device is close to that measured by the electrochemical workstation (RSD<10%), which makes the sensor practical and portable.
关键词： Nanoporous BiVO4,Ascorbic acid,Portable device,Photoelectrochemical sensor
更新于2025-09-19 17:13:59
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EXPRESS: Fluorescence Turn-On Detection of Ascorbic Acid Using a Self-Assembled Lanthanide Polymer Nanoparticle
摘要： Ascorbic acid (AA), or vitamin C, is an important reactive biological molecule in vivo, and the abnormal level AA is associated with many diseases. Therefore, the rapid, sensitive, and selective detection of AA levels is of significance in cases of medical assay and diagnosis. Compared with other nanoparticles, lanthanide coordination polymer nanoparticles (Ln-CPs) have been demonstrated as the excellent biomolecule sensing platforms due to their unique optical properties and intrinsic porosities. In this work, the cerium coordination polymer nanoparticles ATP-Ce-Tris were synthesized in a simple and quick way. The synthesized ATP-Ce-Tris nanoparticle shows the characteristic peak of Ce3+ located at 365 nm, which is corresponding to the 4f→5d transition of Ce3+. In the presence of Fe3+, the fluorescence of ATP-Ce-Tris quenched, and the following added ascorbic acid (AA) makes it restoring effectively. Based on this, we constructed a fluorescence probe with excellent sensitivity for AA sensing in a wide linear relationship from 0.05 to 500 μM. The detection limit was as low as 18 nM (signal-to-noise ratio of three), which is one or two orders of magnitude lower than those of reported sensors. The proposed sensing systems also exhibits excellent sensitivity for AA detection in human serum sample, exploiting a valuable platform for AA analysis in clinic diagnostic and drug screening.
关键词： Lanthanide coordination polymer,ascorbic acid,fluorescence,turn-on
更新于2025-09-19 17:13:59
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A molybdenum disulfide quantum dots-based ratiometric fluorescence strategy for sensitive detection of epinephrine and ascorbic acid
摘要： In this paper, a novel and sensitive ratiometric fluorescence strategy for the detection of epinephrine (EP) and ascorbic acid (AA) was established based on the fluorescence resonance energy transfer (FRET) between the molybdenum disulfide quantum dots (MQDs) and the fluorescent oxidative polymerization product (PEP-PEI) of EP in polyethyleneimine (PEI) aqueous solution. The continuous formation of PEP-PEI can lead to the fluorescence quenching of MQDs at 414 nm while the fluorescence of PEP-PEI at 522 nm gradually increased. The introduction of AA can inhibit the oxidative polymerization process of EP due to the strong reducibility of AA, resulting in the fluorescence recovery of MQDs at 414 nm and the fluorescence decreasing of PEP-PEI at 522 nm. Therefore, EP and AA can be monitored by measuring the ratio of the fluorescence intensities at 522 nm and 414 nm. A good linear calibration of I522/I414 versus EP and AA concentrations were obtained within 0.2e40 mM and 0.5e40 mM, respectively. And the detection limit was 0.05 mM for EP and 0.2 mM for AA. Furthermore, the developed ratiometric fluorescence method with high sensitivity and selectivity was applied for EP in human urine samples and AA in human serum samples determination with satisfactory results obtained.
关键词： Epinephrine,Polyethyleneimine,Ascorbic acid,MoS2 quantum dots,Ratiometric fluorescence
更新于2025-09-19 17:13:59
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A novel periodically tapered structure-based gold nanoparticles and graphene oxide a?? Immobilized optical fiber sensor to detect ascorbic acid
摘要： This work presents a study, analysis, design, and characterization of a localized surface plasmon resonance (LSPR) based ascorbic acid (AA) sensor with improved sensitivity compared to those already reported. Various multi-tapered (four, five, and eight tapered) optical fiber sensors (OFSs) have been developed and characterized in this study. Along with these, different nanomaterials (NMs), such as gold nanoparticles (AuNPs) and graphene oxide (GO), are immobilized over the bare probe. Further, NMs immobilized probes are functionalized with ascorbate oxidase. The AuNPs are well studied in the past with the variation in size, shape and surface functionalization and have been found to be well-suited NMs for biosensing applications. On the other hand, GO-based material is equally promising in the nanostructure-based optical sensing due to their broad surface area, high electrical conductivity, good chemical stability, and excellent mechanical behavior. The performance parameters of the proposed sensor, such as sensitivity (8.3 nm/mM), correlation correlator (0.9724), and limit of detection (51.94 μM) are greatly improved over the previous designs. A wide range of characterization and validation of NMs immobilized structures are reported here. It indicates a great potential in the practical implementation of LSPR based OFSs for routine diagnostics.
关键词： Multi-tapered optical fiber sensor,Ascorbic acid,Gold nanoparticles,Ascorbate oxidase,Graphene oxide
更新于2025-09-19 17:13:59
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Laser-Induced Graphene-Based Platforms for Dual Biorecognition of Molecules
摘要： Expanding the single molecule detection, enabled by laser-induced graphene (LIG) technology, for portable and on-site analysis, a dual molecule system with a two-working electrode architecture was developed, for ascorbic acid (AA) and amoxicillin (AMOX) detection, which are currently used in aquaculture and persist as water contaminants. The biorecognition element of each target compound was a suitable molecularly-imprinted polymer (MIP). The AMOX MIP was developed herein for the first time and assembled by electropolymerization of eriochrome black T (EBT). It showed a wide linear response from 100 nM to 50 μM, with a sensitivity of -13.32 μA/decade. Calibration curves revealed good squared correlation coefficients (R2 > 0.99) with a limit of detection (LOD) of 11.98 nM. AA MIP was assembled according to previous work reported in the literature, displaying a linear response from 1.5 mM to 4 mM and a sensitivity of 1.356 μA/decade. The developed dual-LIG device was further tested in real samples and successfully applied to the analysis of binary mixtures prepared in environmental water samples from a well. Overall, the proposed device allows in-situ analysis of two different molecules, holds an exceptionally low-cost design when compared to competing architectures in the literature, and, the fabrication method here employed offers the possibility of easily adjusting the desired architecture on demand.
关键词： Amoxicillin,Ascorbic acid,Laser-induced graphene,Molecularly-imprinted polymer technology,Dual detection
更新于2025-09-19 17:13:59
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Amino Acids as the Nitrogen Source to Synthesize Boron Nitride Quantum Dots for Fluorescence Turna??offa??on Detection of Ascorbic Acid
摘要： The BNQDs are synthesized by simple one-step hydrothermal method, using amino acids as nitrogen source and boric acid as boron source. The BNQDs prepared by different amino acids emit strong blue fluorescence with the excitation wavelength from 280 to 400 nm. An “on-off-on” BNQDs fluorescent sensor is designed to detect ascorbic acid with Fe3 + as medium, extending the application in sensing. The fluorescence of BNQDs is quenched by Fe3 + on basis of the inner filter effect. With increasing of ascorbic acid, the fluorescence of BNQDs is recovered due to the oxidation-reduction between Fe3 + and ascorbic acid. The assay is capable of recognizing ascorbic acid in the concentration range of 1–100 μM with a detection limit of 0.0833 μM. In addition, the method has the potential to determine Fe3 + and ascorbic acid in real water samples and human serum.
关键词： amino acids,sensors,ascorbic acid,fluorescence,BNQDs
更新于2025-09-19 17:13:59
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Electrochemical behaviour and analytical applications of a manganese porphyrin a?? silica hybrid film prepared by pulsed laser deposition
摘要： Hybrid nanomaterials can have superior properties in comparison with individual components, sometimes greatly improving their optoelectronic activity. For this reason, modified carbon electrodes were obtained using a hybrid material composed of 5,10,15,20-tetra(4-tolyl)porphyrinato manganese (III) chloride (MnTTP) embedded in a silica matrix. The laser ablation deposition technique (PLD) has been used to immobilize the manganese porphyrin–silica hybrid on the surface of the carbon electrodes. The successful transfer of the manganese-porphyrin was evidenced by UV–Vis absorption spectroscopy. The PLD-deposited hybrid film was characterized using AFM and electrochemical methods (cyclic voltammetry and square wave voltammetry). The viability of this hybrid nanomaterial film as a redox mediator for the anodic oxidation and sensitive voltammetric determination of ascorbic acid in buffer solution (pH = 6.5) is described. The recorded anodic process is attributed to its oxidation to dehydroascorbic acid, with satisfactory catalytic current response and low non-Faradaic current.
关键词： Mn-porphyrin,Silica matrix,Hybrid nanomaterial,Pulse laser deposition,Electrocatalytic film,Ascorbic acid
更新于2025-09-19 17:13:59
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Bionanosensor based on N-doped graphene quantum dots coupled with CoOOH nanosheets and their application for in vivo analysis of ascorbic acid
摘要： Herein, we employ 3D nitrogen-doped porous graphene frameworks (3D NPG) as raw material to prepare emissive nitrogen doped graphene quantum dots (r-NGQDs) via chemical oxidation method. The as-prepared fluorescent r-NGQDs was integrated with CoOOH nanosheets to construct a sensing platform for in vivo ascorbic acid (AA) analysis. Initially, the fluorescence emission intensity of r-NGQDs was quenched by CoOOH nanosheets based on the inner filter effect (IFE). Then the quenched intensity of r-NGQDs and CoOOH nanosheets system was enlightened by the addition of AA, since AA could consume CoOOH nanosheets through redox reaction, leading to the release of r-NGQDs and fluorescence restoration. Moreover, the restored fluorescence intensity of r-NGQDs is highly dependent on the concentration of AA which endows them as a quantitative analysis of AA with a limit of detection (LOD) reach up to1.85 μM (n = 3) in aqueous solution. Finally, the as constructed bionanosensor was further employed for in vivo analysis of AA in living rat brain microdialysate with basal value up to 9.4 ± 1.4 μM (n = 3).
关键词： Nitrogen-doped porous graphene,Graphene quantum dots,Ascorbic acid,In vivo,CoOOH nanosheets
更新于2025-09-16 10:30:52