N-doped Carbon Dots Research Articles

The synthesis of N-doped carbon dots for visual differentiating and detection of tetracyclines.

N-doped carbon dots (N-CDs) were synthesized from L-glutamine and triethanolamine via one-step hydrothermal method. The N-CDs emitting blue fluorescence have selective response to tetracyclines (TCs), and can be used as a fluorescent probe to realize the quantitative detection and qualitative analysis of TCs. A method for the determination of TCs by the N-CDs in actual samples has been successfully established. The recovery rate was maintained at 97.50-105.60%, and the relative standard deviation (RSD) was below 3%. Meanwhile, TCs can be visually distinguished using filter paper by the different fluorescence colors (light green, dark blue and yellow-green) of the N-CDs/TCs system under ultraviolet (UV) light. This study provides a relatively simple method to detect and identify TCs.

N-doped carbon dots as the multifunctional fluorescent probe for mercury ion, glutathione and pH detection

Recently, carbon dots (CDs) have exhibited promising applications in the fluorescence detection of various ions and biomolecules. In this work, one kind of nitrogen-doped CDs (N-CDs) with high fluorescence intensity was synthesized, characterized by transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, Fourier-transform infrared, UV–vis absorption spectra, and fluorescence spectra. The results show that the spherical and uniform N-CDs (quantum yield: 60.2%) have remarkable fluorescence properties and photostability, which makes N-CDs can be utilized as an ‘on-off-on’ sensor for Hg2+ and glutathione (GSH). In addition, the pH-sensitive behavior of N-CDs makes it also applicable to H+ detection under acid conditions (pKa = 3.53). The linear range of the ‘turn-off’ sensor detecting Hg2+ was 0.014–50 μM, with a 0.014 μM limit of detection (LOD). GSH was detected by the fluorescence ‘turn-on’ method with a linear range of 0.125–60 μM and a LOD of 0.125 μM. The outstanding performance of N-CDs makes it potential applications in ecological pollution and biomolecule visualization monitoring.

Dual emission N-doped carbon dots as a ratiometric fluorescent and colorimetric dual-signal probe for indigo carmine detection

Novel dual-emission fluorescent nitrogen-doped carbon dots (N-CDs) were synthesized by a facile one-pot hydrothermal method using ascorbic acid and rhodamine B as precursors and melamine as nitrogen source. The obtained N-CDs exhibited dual-emitting peaks at 435 nm and 578 nm under the single excitation of 350 nm. The fluorescence at 578 nm was more effectively quenched by indigo carmine (IC) based on the internal filtration effect and aggregation-induced emission quenching. Meanwhile, the apparent color change of N-CDs from pink to blue-purple after adding various concentrations of IC could be clearly observed with the naked eye. Therefore, a ratiometric fluorescent and colorimetric dual-signal probe based on N-CDs was developed for IC detection with high selectivity and sensitivity. The addition of IC caused the ratiometric fluorescent value (F435/F578) to increase linearly within the range from 0 to100 µM with a detection limit (LOD) of 0.18 µM and the colorimetric signal presented a linear response in the range of 0–133 µM with a LOD of 57.4 nM. Furthermore, the IC in juice drink, candy, and water was successfully detected. Besides, the N-CDs were also designed as a ratiometric temperature probe, and the ratiometric fluorescence signal (F435/F578) was linearly and reversibly responsive to temperature in the range of 20–75 °C.

Light-induced hydrogen production from water using nickel(II) catalysts and N-doped carbon-dot photosensitizers: catalytic efficiency enhancement by increase of catalyst nuclearity.

Solar energy conversion to chemical energy via light-induced H2O splitting to O2 and H2 is considered to be a promising solution to meet the growing global energy demands. To make this transformation economically viable, it is necessary to develop sustainable photocatalytic systems. Herein, we present an efficient photocatalytic H2 production system which relies on components comprised of low-cost and high-abundance elements. In particular, a series of mononuclear complexes [Ni(LNS)3]- and [Ni(N^N)(LNS)2] and a hexanuclear complex [Ni(LNS)2]6 (N^N = diimine and LNS- = heterocyclic thioamidate with different group-substituents) were synthesized and utilized as catalysts, in combination with N-doped carbon dots as photosensitizer, for efficient H2 evolution from aqueous protons. Differences in H2 production efficiency were observed among the studied Ni(II) catalysts, with complexes bearing ligands with stronger electron-donating ability exhibiting higher catalytic activity. A remarkable catalytic efficiency enhancement was observed for the hexanuclear complex, with catalyst loadings lower than those of the mononuclear Ni(II) complexes, affording TONs >1550 (among the highest values reported for photocatalytic systems of similar type operating in H2O). These data provide an indication of catalytic cooperativity between the metal centers of the hexanuclear complex, and demonstrate the crucial role of atomically precise polynuclear Ni(II) catalysts in light-induced H2 production, a result that can guide future catalyst design towards the development of highly efficient, low-cost and environmentally benign photocatalytic systems.

Surfactant encapsulating N-doped carbon dots with enhanced optical properties as a selective sensor for Cr(VI) detection.

Detecting hexavalent chromium (Cr(VI)) is important for human health and environmental protection due to its high toxicity, carcinogenicity and persistence, but developing a sensor to selectively detect Cr(VI) remains challenging. Here, we proposed a selective fluorescent sensor for Cr(VI) detection using cetyltrimethylammonium chloride (CTAC) modified N-doped carbon dots (N-CDs-CTAC) synthesized via a post-modification strategy. Specifically, the introduced CTAC molecules could self-assemble into micelles for encapsulating fluorescent N-CDs, causing the aggregation of N-CD particles and then displaying enhanced fluorescence emission owing to the aggregation-induced emission effect. Moreover, the positively charged CTAC can interact with negatively charged Cr(VI) in the form of an anion (Cr2O72-), boosting the ability of the selective recognition of Cr(VI). Thus, a N-CDs-CTAC fluorescent probe was designed to selectively monitor Cr(VI) with an ultralow detection limit down to 40 nM, and was further used for Cr(VI) detection in real environmental samples. The fluorescence quenching mechanism of N-CDs-CTAC by Cr(VI) was attributed to dynamic quenching. The proposed assay opens an avenue for the selective detection of Cr(VI) in the environmental monitoring field.

Enhancing catalytic efficiency of carbon dots by modulating their Mn doping and chemical structure with metal salts.

Nanozymes are emerging materials in various fields owing to their advantages over natural enzymes, such as controllable and facile synthesis, tunability in catalytic activities, cost-effectiveness, and high stability under stringent conditions. In this study, the effect of metal salts on the formation and catalytic activity of carbon dots (CDs), a promising nanozyme, is demonstrated. By introducing Mn sources that possess different counter anions, the chemical structure and composition of the CDs produced are affected, thereby influencing their enzymatic activities. The synergistic catalytic effect of the Mn and N-doped CDs (Mn&N-CDs) is induced by effective metal doping in the carbogenic domain and a high proportion of graphitic and pyridinic N. This highly enhanced catalytic effect of Mn&N-CDs allows them to respond sensitively to the interference factors of enzymatic reactions. Consequently, ascorbic acid, which is an essential nutrient for maintaining our health and is a reactive oxygen scavenger, can be successfully monitored using color change by forming oxidized 3,3',5,5'-tetramethylbenzidine with H2O2 and Mn&N-CDs. This study provides a basic understanding of the formation of CDs and how their catalytic properties can be controlled by the addition of different metal sources, thereby providing guidelines for the development of CDs for industrial applications.

Facile hydrothermal synthesis of N-doped fluorescent carbon dots for selective detection of insecticide parathion.

Pesticides are enormously important to industry requirements and in agriculture for improving yields. Parathion is widely used to control pests in vegetables, fruits, and flowers. However, excessive use of parathion poses a threat to food safety, the environment, and human health. Due to low cost, ease to use, and high selectivity and sensitivity, a fluorescent nanoprobe is a candidate for parathion detection. Blue fluorescent carbon dots were prepared by a hydrothermal method with rutinum and o-phenylenediamine as precursors. The Rut-CDs were purified by using dialysis, thin layer chromatography, and a chromatographic column. Excellent linear ranges of 0-7.5 μg L-1 and 12.5-62.5 μg L-1 parathion were obtained with a low detection limit of 0.11 ng mL-1. In addition, the quenching mechanism of parathion to the fluorescence of Rut-CDs was illuminated. Furthermore, the nanoprobe was efficiently applied to determine the parathion content in Chinese cabbage, cantaloupe, and cowpea samples. It shows great potential to detect parathion.

Novel N-doped carbon dots derived from citric acid and urea: fluorescent sensing for determination of metronidazole and cytotoxicity studies.

Blue emitting nitrogen-doped carbon dots were synthesized using citric acid and urea through the hydrothermal method, and the fluorescence quantum yield was 35.08%. We discovered that N-CDs featured excellent robust fluorescence stability and chemical resistance. For metronidazole detection, our N-CDs exhibited quick response time, high selectivity and sensitivity, and low cytotoxicity. Specifically, our N-CDs could detect metronidazole in the linear range of 0-179 μM, and the LOD was 0.25 μM. Furthermore, metronidazole efficaciously quenches the fluorescence of N-CDs, possibly owing to the inner filter effect. Lastly, we have employed our N-CDs to detect metronidazole in commercial metronidazole tablets with high accuracy. Overall, the newly prepared fluorescence sensor, N-CDs, demonstrated a huge potential to detect metronidazole in a simple, efficient, sensitive, and rapid manner.

The fabrication of N-doped carbon dots by methionine and their utility in sensing Cu2+ in real water.

Copper ions (Cu2+) are ubiquitous in the ecosystem and cause serious environmental pollution, posing a threat to human health. Therefore, sensitive detection of Cu2+ is urgently needed. Herein, we employed a solvothermal method to prepare blue-emitting carbon dots (Met-CDs) using formamide (FA) and methionine (Met) as precursors, with a high quantum yield (QY) of 38%. Based on the good optical stability of Met-CDs and selective quenching by Cu2+, a sensitive probe using Met-CDs for the detection of Cu2+ in water was successfully designed. Within the linear range of 0.15-2 μM, the limit of detection (LOD) was determined to be as low as 47.7 nM, enabling the quantitative detection of Cu2+. Moreover, the recovery data of the spiked analysis of lake/river water samples were also satisfactory and verified the feasibility of the probe by the analysis of Cu2+ in natural conditions.

Nanosensor Composed of N-Doped Carbon Dots for Highly Selective Detection of Riboflavin

Nanosensor Composed of N-Doped Carbon Dots for Highly Selective Detection of Riboflavin

Self-crosslinked N-doped carbon dot supported Pd as an efficient catalyst for dehydrogenation of formic acid at room temperature

The optimized Pd/CDs-III catalyst shows 100% FA dehydrogenation within 21 min, with a TOF value of 256 h−1 at 298 K. This work provides a powerful guidance for the rational design of active catalysts for dehydrogenation of FA.

Bamboo Stem Cellulose Derived N-Doped Carbon Dots for Fluorescent Security Inks: Synthesis, Characterization, and Inkjet Printing

Bamboo Stem Cellulose Derived N-Doped Carbon Dots for Fluorescent Security Inks: Synthesis, Characterization, and Inkjet Printing

N-doped carbon dots modified Bi2MoO6 microspheres as anode materials for high performance aqueous rechargeable nickel//bismuth batteries

Aqueous rechargeable batteries, as one kind of new energy storage and conversion systems, have gradually drawn researchers’ concern. Herein, N-doped carbon dots (N-CDs) are used as conductive agents to prepare multidimensional Bi2MoO6@N-CDs anode materials. The synergistic effect between three-dimensional (3D) flowering spherical Bi2MoO6 and zero-dimensional (0D) carbon dots derived carbon depends on the spatial and compositional diversity. The anode performs excellent electrochemical properties owing to the introduction of N-CDs offering high density of reaction sites and quick charge transfer process. Similar to Bi2MoO6@N-CDs, N‑CDs modified Co0.5Ni0.5MoO4 was prepared as cathode materials, manifesting excellent specific capacity. A novel aqueous rechargeable nickel//bismuth battery with above materials delivers the energy density of 50.85 Wh/kg along with power density of 344.27 W/kg at 0.5 A/g. The present research would broaden the path for effectively structuring of electrode active materials for aqueous rechargeable Ni//Bi batteries.

One-step synthesis of N-doped carbon dots as sensitive “on–off-on” fluorescent sensor for tetracycline and Al3+ detection

Novel bifunctional nitrogen-doped carbon dots (N-CDs) were prepared through solid-phase thermal treatment of melamine and citric acid monohydrate (CA) as precursors. The N-CDs displayed uniform size distribution, excellent photostability and bright fluorescence emission with the fluorescence quantum yield of 24 %. The N-CD-based fluorescence “on–off-on” sensing platform exhibited rapid, selective and sensitive detection of TCs (tetracycline hydrochloride and doxycycline) and Al3+. The fluorescence at 472 nm can be quenched by TCs through the internal filtration effect (IFE) and can also be recovered with the addition of Al3+ by the stronger affinity between Al3+ and TCs than that of CDs. The fluorescent sensor exhibits excellent selectivity and high sensitivity toward TCs and Al3+ detection with low detection limits for tetracycline hydrochloride: 91.8 nM, doxycycline: 78 nM and Al3+: 163.5 nM. Moreover, the proposed sensing platform is utilized for detecting TCs and Al3+ in tap water and milk samples. In addition, the N-CD probe can be used for cell imaging based on its low toxicity and good biocompatibility, implying the potential applications in the fields of biomarkers and bioanalysis in vivo imaging studies.

Novel green synthesis of N-doped carbon dots from fruits of Opuntia ficus Indica as an effective catalyst for the photocatalytic degradation of methyl orange dye and antibacterial studies

• We have prepared Undoped and N-doped C-dots from Opuntia ficus Indica plant extract. • The synthesized Undoped and N-doped C-dots exhibit, the green fluorescence. • We found higher photocatalytic activity in N-doped C-dots than Undoped C-dots. • N-doped C-dots have utilized as photocatalytic for the degradation of Methyl orange dye. • Further we have study them anti-bacterial activity using gram negative and gram positive bacterias. A carbon dot is an attractive material for the photocatalytic degradation of organic pollutant. Moreover it’s extensively used as a material to control the growth of micro organisms. Herein we are reporting the synthesis of Undoped and N-doped carbon dots (N-CDs) derived from Opuntia Ficus Indica (O.F.Indica) fruits. Further we have well characterized by UV-Vis, FT-IR, XPS spectral, HR-TEM, Raman and XRD techniques. The synthesized Undoped and N-CDs are stable for 3 months. Finally we have found the N-CDs shows the higher photocatalytic activity then Undoped C-dots, due to presence of N-atom. We also have discussed the possible degradation mechanism of Methyl Orange (MO). Finally the N-CDs was utilized their antibacterial activities. We used Streptococcus Pyogenes, Staphylococcus Aureus , Klebsiella Pneumoniae, and Shigella Flexneri. Among them we found Streptococcus Pyogenes a bacterium was largely controlled the growth by our N-CDs.

Synthesis of Ce, N co–doped carbon dots as green and effective corrosion inhibitor for copper in acid environment

Background: A new high-effectively corrosion inhibitor was used to replace the traditional corrosion inhibitor and reduce the environment pollution.Methods: Through hydrothermal synthesis, Ce and N co-doped carbon dots (Ce@N-CDs) were generated. Before the performance characterization, the microstructure and chemical composition of Ce@N-CDs were firstly investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) techniques. The electrochemical test revealed that the IE of Ce-10% (200 mg/L) on copper was as high as 98%, presenting the best inhibition effect. According to the adsorption isotherm analysis, the Ce@N-CDs mainly adsorbed according to the Langmuir model, and the adsorption process was completed by combining physical and chemical adsorption.Significant findings: Through the morphology, energy dispersive spectrometer (EDS) and XPS analysis of copper surface after corrosion process, it was found that the Ce@N-CDs formed a dense adsorption/passivation film on the copper surface. The adsorption film mainly came from the pairing of unsaturated bonds between N-doped CDs (N-CDs) and copper surface. The passivation film mainly came from the oxide formed by the reaction between Ce and the surrounding environment. Their dense structure could effectively inhibit the infiltration and erosion of corrosive medium.

Carbon Dot@MXene Nanozymes with Triple Enzyme-Mimic Activities for Mild NIR-II Photothermal-Amplified Nanocatalytic Therapy.

Nanozymes have shown promising potential in disease treatment owing to the advantages of low-cost, facile fabrication, and high stability. However, the highly complex tumor microenvironment (TME) and inherent low catalytic activity severely restrict the clinical applications of nanozymes. Herein, a novel mild hyperthermia-enhanced nanocatalytic therapy platform based on Z-scheme heterojunction nanozymes by depositing N-doped carbon dots (CDs) onto Nb2 C nanosheets is constructed. CD@Nb2 C nanozymes not only display outstanding photothermal effects in the safe and efficient NIR-II window but also possess triple enzyme-mimic activities to obtain amplified ROS levels. The triple enzyme-mimic activities and NIR-II photothermal properties of CD nanozymes are enhanced by the construction of Z-scheme heterojunctions owing to the accelerated carrier transfer process. More importantly, the introduction of mild hyperthermia can further improve the peroxidase-mimic and catalase-mimic activities as well as the glGSH depletion abilities of CD@Nb2 C nanozymes, thereby producing more ROS to efficiently inhibit tumor growth. The combined therapy effect of CD@Nb2 C nanozymes through mild NIR-II photothermal-enhanced nanocatalytic therapy can achieve complete tumor eradication. This work highlights the efficient tumor therapy potential of heterojunction nanozymes.

Coordination-induced self-assembly based carbon dot dendrimers as efficient signal labels for electrochemiluminescent immunosensor construction

In this work, an “on-off” electrochemiluminescent immunosensor for bone alkaline phosphatase (BALP) detection was constructed based on the carbon dot dendrimers (CD DRs) as signal labels and Pt nanoparticles functionalized Ni-phenolic coordination spheres (Pt@Ni-PCS) as quenching labels. The prepared CD DRs with low cytotoxicity were synthesized via coordination-induced self-assembly of carboxyl groups-rich N-doped carbon dots and zirconium oxygen clusters, of which the ECL efficiency was 2-fold enhancement than that of discrete N-doped carbon dots. Benefiting from the efficient quenching effect of Pt@Ni-PCS toward Zr-CD DRs/triethylamine-based ECL system, the prepared immunoassay for BALP detection exhibited a broad linear range with 1 pg/mL to 50 ng/mL and a low limit of detection of 24.9 fg/mL. Importantly, this highlights coordination-induced self-assembly as a tool for carbon dots enrichment to construct efficient ECL nanocomposites, which conceptualizes a pathway to expand the application of carbon dots in clinical ECL analysis technology.

Fabrication of Copper-Terephthalate Frameworks and N-Doped Carbon Dots Composite for Boosting Photocatalytic Performance

Fabrication of Copper-Terephthalate Frameworks and N-Doped Carbon Dots Composite for Boosting Photocatalytic Performance

Nitrogen-Doped Carbon Dots with Free Radical Scavenging Abilities as Fluorescence Probes for Cr(VI) Sensing in Bio-Systems

Carbon dots (CDs) are a new class of fluorescent nanomaterials that can be used in optical devices, fluorescence sensing and bio-imaging. Recently, the preparation of CDs from biomass gained great interest because the source is plentiful and they are friendly to environment. However, there still exist some problems including low quantum yield (QY) and limited application. Although CDs have been successfully applied in detection of various ions, the sensing of Cr(VI) and the corresponding mechanism is rarely proposed. Here, a facile and effective preparation of N-doped carbon dots (N-CDs) from sweet potatoes was developed through hydrothermal synthesis, using urea as passivator. The characterization was performed to demonstrate the morphology and chemical composition of the N-CDs. In particular, it is confirmed that N element exists in NH2 group on the surface of the N-CDs. Because of doing with N element, the QY of these CDs significantly increases to 31%. In addition, the N-CDs exhibit favorable free radical scavenging activities toward DPPH, hydroxyl and superoxide anion free radicals. This antioxidant property, combined with inner filter effect, endows the N-CDs with florescence response to Cr(VI). The further study showed that linear range of Cr(VI) concentration is from 1[Formula: see text][Formula: see text]M to 80[Formula: see text][Formula: see text]M with a detection limit of 0.61[Formula: see text][Formula: see text]M. Subsequently, the N-CDs were competent to detect trace Cr(VI) both in human serum and pig liver. Based on the fact that the N-CDs are biocompatible by MTT experiment, the N-CDs were excellent in fluorescent sensing of Cr(VI) in living cells. In a word, the N-CDs are suitable to be applied for Cr(VI) detection in bio-systems, as well as in antioxidant fields.