Blue Fluorescent Carbon Dots Research Articles

Fluorescence Sensing of Glutathione Based on the In-Situ Growth of Carbon Dots-Manganese Dioxide Nanosheets

Blue fluorescent carbon dots with high purity were synthesized through a one-step hydrothermal method using citric acid and ethylenediamine as raw materials and then purification by column chromatography. In-situ controllable synthesis was used to prepare carbon dots-manganese dioxide (CDs-MnO2) nanosheets, with carbon dots as the seed, potassium permanganate as the manganese source and sodium citrate as the reducing agent. The as-prepared nanosheets were characterized by transmission electron microscopy, absorption spectroscopy, and fluorescence spectroscopy. It was found that MnO2 can be degraded by Glutathione (GSH) through a redox reaction, which restores the fluorescence of CDs. A new method for determining GSH was constructed using CDs-MnO2 fluorescence sensing. The method is simple and sensitive, with linear ranges of 0.1-5 μM and 10-60 μM, respectively, and a lowest detection limit of 0.034 μM. The method was successfully used for the determination of GSH in human serum, with satisfactory recoveries in the range of 98.9-100.1%.

In situ green synthesis of Rosa sterilis-based carbon dots for Fe3+ fluorescent sensing in baijiu

Baijiu is susceptible to contamination by Fe3+ during brewing and storage, and it is crucial to select a convenient method for the detection of Fe3+. In this work, we developed a one-step hydrothermal in situ green synthesis of blue fluorescent carbon dots (RS-CDs) from Rosa sterilis. A series of characterization of RS-CDs was carried out, and it was found that RS-CDs derived from biomass materials were environmentally friendly and low toxic, with an average particle size of 2.75 nm, a graphitic structure, and a surface rich in functional groups related to C, N, and O atoms. In addition, the PL of RS-CDs exhibited excitation-dependent behavior. The emission center was redshifted from 448 nm to 530 nm at excitation wavelengths ranging from 320 nm to 460 nm. After investigating the selectivity of RS-CDs for different metal ions, we found that RS-CDs had the highest quenching efficiency for Fe3+ and exhibited a static quenching mechanism. The LOD was 0.959 μM in the linear range of 0-140 μM. In addition, RS-CDs were successfully used for the detection of Fe3+ in four kinds of basic flavor baijiu, as well as in different containers for storage of baijiu. The study demonstrated that Rosa sterilis can be used to produce green and low-cost CDs, and the prepared RS-CDs can be conveniently, rapidly and selectively detected Fe3+ in the baijiu system, which is of potential application.

Unlocking the potential of eggplant peel: Powerful peroxidase nanozyme for l-cysteine determination in pharmaceutical supplements

For the first time, eggplant peel biowaste was upcycled through a very fast one-pot microwave synthesis to produce cost-effective and environmentally friendly blue-fluorescent carbon dots (EPE-CDs). The resulting EPE-CDs emitted fluorescence at 465 nm when excited at 400 nm and exhibited enhanced peroxidase-like behavior without metal doping requirement. They were able to oxidize o-phenylenediamine (OPD) in the presence of hydrogen peroxide (H2O2) to generate 2,3-diaminophenazine (DAP) leading to a new emission peak at 560 nm. Through the inner filter effect, DAP was able to quench the fluorescence of EPE-CDs, causing a change from colourless to yellow. By leveraging the fluorescence characteristics of EPE-CDs and DAP, dual-emission platform was established. This platform could be used for the catalytic detection of H2O2 within the 10–110 μM range. The introduction of L-Cysteine, containing reductive thiols that hinder DAP production, resulted in a reduction in the fluorescence intensity of DAP. The study demonstrated that fluorescence intensities ratio 465 nm / 560 nm (I465/I560) exhibited a linear relationship with L-Cysteine concentration between 4 and 60 μM, reaching detection limit as low as 0.69 μM. Furthermore, when applying the ratiometric fluorescence platform to quantify L-Cysteine in actual samples, the average recoveries ranged from 99.50 % to 101.40 %, with a relative standard deviation (RSD) not exceeding 2 %. Through the exploration of the fluorescence properties and nanozyme-like capabilities, this research offers a novel perspective on utilizing biowaste sources for CD synthesis and utilization of these CDs as nanozymes.

Amine-Rich Carbon Dots Synthesized from Kappa-Carrageenan and l-Lysine as a Dual Probe for Detection of Folic Acid and Tumor-Targeted Delivery of Therapeutics.

Strategically designed, heteroatom-rich surface functionalized blue fluorescent carbon dots (CDs) were synthesized for high-throughput detection of folic acid (vitamin B9). The highly stable CDs could particularly detect vitamin B9 in the presence of 35 analytes, even up to 40 nM of the vitamin. The versatile CDs were found to have a high affinity for folic acid in wastewater, folic acid tablets, and food samples enriched with folic acid. The hemocompatibility of the CDs was also studied by using a hemolysis assay, confirming the CDs to be nontoxic to human blood samples up to 400 μg/mL. The CDs were then covalently conjugated to biotin, which possesses receptors that are overexpressed in tumor cells. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide dye) assay and confocal bioimaging studies proved the biotin-modified CDs (CDBT) were remarkably nontoxic in healthy cell lines (HEK-293) and highly target-specific toward tumor cells (HeLa), including triple-negative breast cancer cells (MDA-MB-231). The cytotoxicity assay of 5-fluorouracil encapsulated CDs (CDBTFu) showed the IC50 value to be 81 μM in HeLa cells and 185 μM in MDA-MB-231 cells, respectively, and significantly higher in HEK-293 cells (over 300 μM), owing to high specificity toward tumor cells.

Green synthesis of carbon dots from mature green tea leaves for label-free fluorescence sensing of chromium(VI)

Hexavalent chromium (Cr(VI)) has been established as a highly carcinogenic and mutagenic entity. Therefore, there has been a persistent demand for affordable, sensitive, and quick sensors to monitor the presence of Cr(VI) in aqueous systems. A straightforward, cost-efficient, and eco-friendly approach has been reported in this work in terms of blue-fluorescent carbon dots (CDs, 5.2 nm) being realized in a single-step hydrothermal process. For this purpose, fully grown green tea leaves as the main carbon source were deployed due to being cheap, and environmentally sustainable and readily accessible sources. These CDs exhibit good water solubility, photo-stability and photo-emission (maximal emission at 438 nm for 360 nm excitation wavelength), anti-interference, and low cytotoxicity. The article demonstrates a straightforward fluorescent test for the precise detection and determination of Cr(VI). This was realized through the construction of a non-luminous complex which led to fluorescence quenching via the inner filter effect (IFE). Accordingly, the system can be employed as a label-free nanosensor. Under optimal condition (pH 4 and 5 min reaction time), the fluorescence quenching efficiency of CDs exhibited a well-defined linear correlation in the 0.01–8 mg/L concentration range of Cr(VI). A linear equation represents the system sensor as F0/F = 0.2101x + 1.0016 (R2 = 0.99). The limit of detection (LOD) has been as minimal as 0.004 mg/L (s/k = 3). These findings infer CDs as a potential cost-effective nanosensor for Cr(VI) identification in tap water specimens.

A dual-signal optical sensing platform of CDs-MnO2 NS composites for facile detection of ascorbic acid based on a combination of Tyndall effect scattering and fluorescence.

A dual-signal optical sensing platform was successfully developed for the determination of ascorbic acid (AA) based on blue fluorescent carbon dots (CDs) and manganese dioxide nanosheets (MnO2 NSs) with strong Tyndall effect (TE) scattering and fluorescence quenching capabilities. In this nanosystem, CDs-MnO2 NS composites were employed as probes to evaluate the AA concentration. Owing to the strong reduction, the presence of the target AA could reduce the MnO2 NSs to Mn2+ and induce the degradation of the MnO2 NSs, resulting in a significant decrease in the TE scattering intensity of the MnO2 NSs and the fluorescence recovery of the CDs. Therefore, a novel optical sensor based on TE scattering and fluorescence dual detectors was developed for the sensitive determination of AA. Under optimized conditions, the limits of detection (LODs) of the two modes were 113 and 3 nM, respectively. Furthermore, the dual-signal optical sensing platform was successfully applied for the detection of AA in human serum.

Briht, blue fluorescent carbon dots for sensitive and selective detection of folic acid

Bright, blue fluorescent carbon quantum dots (N-CDs) were carried out utilizing phenylenediamine and ascorbic acid as raw precursor through the hydrothermal method. The as-designed N-CDs suggested excitation-dependent characteristic changing from 340 nm to 380 nm. Moreover, Folic acid could availably quench the fluorescence intensity of the N-CDs. According to this experimental phenomenon, the sensitivity and selectivity of N-CDs for folic acid detection were developed. Under optimal experimental conditions, the as-prepared probe displayed excellent linearity with the folic acid concentration changing from 0.5 to 200 μM, and the limit of detection was 0.079 μM. Furthermore, the as-prepared probe indicated good sensitivity towards folic acid sensing in glucose and bovine serum samples. The recoveries of 95.9–104.8 % and 98.6–106.9 % were obtained in glucose and bovine serum samples, respectively. The corresponding relative standard deviation was lower than 2.74 % and 2.91 %, respectively. With preeminent sensitivity and selectivity, this as-developed nanosensor afforded a prospective platform for measuring folic acid in real samples. Furthermore, this N-CDs could be applied for the temperature detection.

Carbon dots as multifunctional fluorescent probe for Fe3+ sensing in ubiquitous water environments and living cells as well as lysine detection via “on-off-on” mechanism

Iron and amino acids are essential nutrients for living organisms, and their deficiency or excess can cause a range of diseases. Therefore, there is considerable interest in developing sensing assays capable of detecting these nutrients with sensitivity, selectivity, and multifunctionality even in complex environments. In this report, hydrothermally synthesized blue fluorescent carbon dots (C-dots) from zinc gluconate were utilized for the detection of Fe3+ and lysine via “on-off” and “on-off-on” mechanisms, respectively. Specifically, the Fe3+ sensing assay achieved a broad linear range of 0–200 μM and a low limit of detection (LOD) of 1.9 μM. It is worth mentioning that the assay was also well adapted to natural aqueous environments (e.g., lake water), and its linear detection range could be extended to 0–1000 μM with a LOD of 3.3 μM. Furthermore, the assay was also effective for intracellular Fe3+ tracking. Most importantly, the assay could also be applied for the quantitative detection of lysine with a linear range of 0–1200 μM and LOD of 8.6 μM. Systematic mechanistic studies revealed that Fe3+ sensing was based on a static quenching process between C-dots and Fe3+, whereas a stronger complexation might have formed between Fe3+ and Lys, leading to the release of C-dots and thus the recovery of fluorescence.

A fluorescence probe based on blue luminescent carbon dots for sensing Fe3+ in plants

Blue fluorescent carbon dots were synthesized via a hydrothermal method using glutathione and sodium citrate, and a carbon dot-based sensing platform was constructed to realize in vivo sensing of Fe3+ distribution in plant species.

Carbon dots-cadmium sulfide quantum dots nanocomposite for 'on-off' fluorescence sensing of chromium(vi) ions.

This work involves fluorescent probe which is composed of carbon dots (CD) and cadmium sulfide quantum dots (CdS QD) for the sensitive and selective fluorescence detection of chromium(vi) ions. The blue fluorescent carbon dots were synthesized by hydrothermal method from natural precursor apricot. The carbon dots-cadmium sulfide quantum dots (CD-CdS QD) nanocomposite was synthesized and all as-synthesized products were characterized using different characterization techniques. It showed white fluorescence under UV light which was quenched selectively in the presence of chromium(vi) ions due to the inner filter effect (IFE). The linear decrease in the white fluorescence was observed in the concentration range 2-120 μM of chromium(vi) ions with the limit of detection 2.07 μM. This is novel probe for the sensitive, selective and rapid detection of chromium(vi) ions.

Dual modulation of blue-fluorescent carbon dots for simultaneous detection of topotecan and pantoprazole.

This study introduces a novel approach for the simultaneous determination of topotecan (TOP) and pantoprazole (PNT), two drugs whose interaction is critical in clinical applications. The significance of this study originates from the need to understand the pharmacokinetic changes of TOP after PNT administration, which can inform necessary dose adjustments of TOP. To achieve this, nitrogen blue emissive carbon dots (B@NCDs) were produced and employed due to their unique fluorescent properties. When TOP is added to B@NCDs, it exhibits strong native fluorescence at 545 nm without influencing the B@NCDs' fluorescence at 447 nm. Conversely, PNT causes quenching of B@NCDs fluorescence, a property that enables the distinct detection of both drugs. The B@NCDs were fully characterized using different techniques, including ultraviolet-visible spectrophotometry, fluorescence analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), and FTIR spectroscopy. The proposed method demonstrated excellent linearity, selectivity, and sensitivity, with low detection limits (LOD, S/N = 3); 0.0016 μg mL-1 for TOP and 0.36 μg mL-1 for PNT. Applied to spiked rabbit plasma samples, this method offers a new approach for evaluating the pharmacokinetic interaction between TOP and PNT. It enables the determination of all pharmacokinetic parameters of TOP before and after coadministration with PNT, providing essential insights into whether dose adjustments are necessary. This research not only contributes to the field of drug monitoring and interaction studies but also exemplifies the potential of B@NCDs in complex biological matrices, paving the way for further pharmacological and therapeutic applications.

Development of FRET-based optical sensors using N-doped carbon dots for detection of chromium (VI) and manganese (VII) in water for a sustainable future

Carbon dots (CDs) synthesis has received much attention due to their considerable application potential. Natural compounds are efficient CD carbon precursors, exhibiting significant physical and chemical characteristics. In the present work, the hydrothermal method has successfully derived blue fluorescent N-doped carbon dots (NCDs) from Alstonia scholaris leaves and ethylenediamine. The synthesized NCDs were characterized by Fourier transform infrared (FTIR), Transmission Electron Microscopy (TEM), fluorescence and UV–vis analysis. It exhibits better chemical and physical properties with a relatively good quantum yield of 21%. As-synthesized NCDs were applied for the FRET-based detection of Cr6+ and Mn7+ ions in water samples to investigate their suitability as fluorescent probes. The detection limit was 0.173 µM and 0.394 µM for Cr6+ and Mn7+, respectively. This study has illustrated an environmentally friendly approach for the facile synthesis of blue fluorescent NCDs with remarkable potential for further utilization in sensing devices.

Fluorescent carbon dots synthesized by waste wind turbine blade for photocatalytic degradation.

Developing novel waste recycling strategies has become a feasible solution to overcome environmental pollution. In this work, a method of using waste wind turbine blade (WTB) as a carbon source to synthesize blue fluorescent carbon dots (B-CDs) by hydrothermal treatment is proposed. B-CDs are spherical and have an average particle size of 5.2nm. The surface is rich in C-O, C=O, -CH3 , and N-H bond functional groups, containing five elements: C, O, N, Si, and Ca. The optimal emission wavelength of B-CDs is 463 nm, corresponding to an excitation wavelength of 380 nm. Notably, a relatively high quantum yield of 29.9% and a utilization rate of 40% were obtained. In addition, B-CDs can serve as a photocatalyst to degrade methylene blue dye, with a degradation efficiency of 64% under 40-min irradiation conditions. The presence of holes has a significant influence on the degradation process.

Preparation of bright blue fluorescent carbon dots and their application in highly sensitive chlorogenic acid detection

In this work, bright blue fluorescent carbon dots (CDs) were synthesized through a hydrothermal method by using l-phenylephrine as carbon source. Under exciting at 363 nm, the prepared CDs emitted bright blue fluorescence at 457 nm. The fabricated CDs showed outstanding salt tolerance, temperature stability and good resistance to photobleaching. Interestingly, the fluorescence of CDs could be distinctly quenched by chlorogenic acid (CGA). By using CDs as fluorescent probe, a novel fluorescence method for highly sensitive detection of CGA was established with a wide linear range of 0.1–220 µM and a limit of detection (LOD) as low as 33 nM. The response mechanism was also studied. The method has been successfully applied for the detection of CGA content in three samples of honeysuckle, coffee beans and Eucommia ulmoides leaves with satisfactory recoveries.

Heteroatom-Doped Carbon Quantum Dots and Polymer Composite as Dual-Mode Nanoprobe for Fluorometric and Colorimetric Determination of Picric Acid.

Oxygen- and nitrogen-heteroatom-doped, water-dispersible, and bright blue-fluorescent carbon dots (ON-CDs) were prepared for the selective and sensitive determination of 2,4,6-trinitrophenol (picric acid, PA). ON-CDs with 49.7% quantum yield were one-pot manufactured by the reflux method using citric acid, d-glucose, and ethylenediamine precursors. The surface morphology of ON-CDs was determined by scanning transmission electron microscopy, high-resolution transmission electron microscopy, dynamic light scattering, Raman, infrared, and X-ray photoelectron spectroscopy techniques, and their photophysical properties were estimated by fluorescence spectroscopy, UV-vis spectroscopy, fluorescence lifetime measurement, and 3D-fluorescence excitation-emission matrix analysis. ON-CDs at an average particle size of 3.0 nm had excitation/emission wavelengths of 355 and 455 nm, respectively. With the dominant inner-filter effect- and hydrogen-bonding interaction-based static fluorescence quenching phenomena supported by ground-state charge-transfer complexation (CTC), the fluorescence of ON-CDs was selectively quenched with PA in the presence of various types of explosives (i.e., 2,4,6-trinitrotoluene, tetryl, 1,3,5-trinitroperhydro-1,3,5-triazine, 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane, pentaerythritol tetranitrate, 3-nitro-1,2,4-triazole-5-one, and TATP-hydrolyzed H2O2). The analytical results showed that the emission intensity varied linearly with a correlation coefficient of 0.9987 over a PA concentration range from 1.0 × 10-9 to 11.0 × 10-9 M. As a result of ground-state interaction (H-bonding and CTC) of ON-CDs with PA, an orange-colored complex was formed different from the characteristic yellow color of PA in an aqueous medium, allowing naked-eye detection of PA. The detection limits for PA with ON-CDs were 12.5 × 10-12 M (12.5 pM) by emission measurement and 9.0 × 10-10 M (0.9 nM) by absorption measurement. In the presence of synthetic explosive mixtures, common soil cations/anions, and camouflage materials, PA was recovered in the range of 95.2 and 102.5%. The developed method was statistically validated against a reference liquid chromatography coupled to tandem mass spectrometry method applied to PA-contaminated soil. In addition, a poly(vinyl alcohol)-based polymer composite film {PF(ON-CDs)} was prepared by incorporating ON-CDs, enabling the smartphone-assisted fluorometric detection of PA.

Heteroatom doped carbon dots from green sources as metal ion sensor and as fluorescent ink

In this study, novel eco-friendly nitrogen-doped carbon dots (NCDs) were prepared via a green, efficient, and one-pot synthesis method from Sida cordifolia root as the carbon source and triethylene tetraamine as the nitrogen source for the detection of metal ions. The amorphous, nanosized carbon dots with 17.8 % quantum yield exhibited exceptional stability towards different experimental conditions. These NCDs acted as a nanoprobe for the sensing of Co(II) and Cu(II) via fluorescence and electrochemical techniques, respectively. These blue fluorescent carbon dots detects Co(II) with a detection limit as low as 0.11 μM and Cu(II) with 0.03 nM. The inner filter effect (IFE) acted as the primary fluorescence quenching mechanism. Also, the developed sensor could detect metal ions in different water samples. Moreover, NCDs were used as fluorescent security ink for writing and drawing. The findings of this study open up a new platform for the effective and reliable sensing of metal ions.

Synthesis of multicolor fluorescent carbon dots from zanthoxylum bungeanum and their application in fluorescent anti-counterfeiting ink

Multicolor fluorescent carbon dots (CDs) have wide application prospects in many fields. Presented herein reported a synthesis of multicolor fluorescent CDs using zanthoxylum bungeanum as a carbon precursor. By changing the nitrogen sources, blue, green, and red fluorescent carbon dots (B-CDs, G-CDs, and R-CDs) with stable optical properties and high quantum yields (QY) were synthesized. Their emission wavelengths are 492 nm, 523 nm, and 601 nm respectively and their QYs were measured to be 13.1%, 11.2%, and 9.8%, respectively. These CDs exhibit good salt resistance, photobleaching resistance, and chemical stability. These characteristics make them suitable for various applications, particularly in the field of anti-counterfeiting fluorescent ink. This study provides an economic and efficient strategy for synthesizing multicolor fluorescent CDs derived from natural products, highlighting the potential for producing multicolor CDs and enhancing their application value.

Detection of oxytetracycline in milk using a novel carbon dots-based fluorescence probe via facile pyrolysis synthesis.

Amphiphilic blue-fluorescence carbon dots (B-CDs) were synthesized via pyrolysis method with citric acid and oleamine as precursors. B-CDs are monodispersed in ethanol, toluene, and ultrapure water with the average particle sizes of 3.33nm, 2.05nm, and 4.12nm, respectively. The maximum emission wavelength of the B-CDs excitation at 370nm is located at 459nm. The B-CDs have good optical properties with excellent photostability. The fluorescence quantum yield (QY) of the as-prepared CDs is as high as 30.17%. The fluorescence of B-CDs is quenched because of static quenching by oxytetracycline. A high selective and sensitive fluorescence probe for detecting oxytetracycline was constructed with a linear range of 1.52-27.60µg/mL and the detection limit of 0.33µg/mL. The B-CDs-based fluorescence probe can be applied to analyze oxytetracycline in milk; the recoveries and relative standard are satisfactory. Furthermore, the B-CDs were exploited for imaging of SH-SY5Y cells. The results demonstrate that as-synthesized CDs can serve as a cellular imaging reagent owing to remarkable bioimaging performance. This work provides a new strategy for the detection of oxytetracycline in food.

Surface engineering of carbon dots for highly sensitive α-glucosidase assay and inhibition evaluation

Monitoring α-glucosidase (α-Glu) activity is of great significance for the early diagnosis of type II diabetes. Here the blue fluorescent carbon dots (CDs) were integrated with two different recognizing molecules, β-cyclodextrin and phenylboronic acid, for assembling a multifunctional CDs (mCDs) nanoplatform for sensitively analyzing α-Glu and its inhibitors. The hydrolyzed product of 4-nitrophenyl-α-d-glucopyranoside (α-Glu substrate), p-nitrophenol, could efficiently quench the fluorescence of mCDs due to its cooperative molecular recognition with β-cyclodextrin and phenylboronic acid. The mCDs could be utilized for the detection of α-Glu activity with the limit of detection of 0.030 U/L. Moreover, the present α-Glu detection platform revealed a high selectivity, and other natural enzymes showed scarcely any effect on the present mCDs system. The proposed method could be facilely used to screen α-Glu inhibitors with satisfying performance. The rational mCDs is expected to supplement more comprehensive biosensing platforms for highly sensitive and specific recognition of disease-relevant biomarkers with clinical importance.

Carbonized human hair derived carbon dots for detection of clozapine

Clozapine (CLZ) is known as the most effective antipsychotic medication for schizophrenia. However, low dosage or over dosage of CLZ is adverse to the treatment of Schizophrenia. Thus, it is necessary to develop effective detection method for CLZ. Recently, due to the advantages such as excellent optical properties, good photobleachability and sensitivity, carbon dots (CDs)-based fluorescent sensors for the detection of target analytes have drawn a great deal of attention. In this work, blue fluorescent CDs (Named as B-CDs) with quantum yield (QY) as high as 38% were obtained by using carbonized human hair as source material through one-step dialysis method for the first time. B-CDs showed obvious graphite-like structure with an average of 1.76 nm, containing abundant functional groups such as -C=O, amino N and C-N on the surface of carbon cores. Optical analysis showed that the B-CDs exhibited excitation-dependent emission property with maximum emission wavelength of 450 nm. Moreover, B-CDs were further applied as a fluorescence sensor to the detection of CLZ. The B-CDs based sensor exhibited a good quenching response by CLZ through the inner filter effect and static quenching mechanism with a limit of detection of 67 ng/mL, which was much lower than the minimal effective concentration in blood (0.35 μg/mL). Finally, to test the practical application value of the developed fluorescence method, the determination of the content of CLZ in tablets and the concentration in blood was carried out. Compared with the results of high-performance liquid chromatography (HPLC) method, it can be found that the constructed fluorescence detection method showed high accuracy and had great application potential in the detection of CLZ. Additionally, the results of cytotoxicity experiment showed that B-CDs had low cytotoxicity, which laid the foundation for the subsequent application of B-CDs in biological systems.