Synthesis Of Nitrogen-doped Carbon Dots Research Articles

Facile synthesis of nitrogen-doped carbon dots for ultrasensitive detection of anticancer drug gefitinib based on IFE

Gefitinib, a highly significant antitumor drug, is now commonly employed in clinical settings as a first-line treatment for patients with advanced or metastatic non-small cell lung cancer, colon cancer, and breast cancer. Herein, a convenient, rapid, and accurate fluorescence method based on nitrogen-doped carbon dots (NCDs) was designed for ultrasensitive detection of gefitinib. The NCDs were easily synthesized through one-pot hydrothermal process using p-phenylenediamine and D-glutamic acid as the precursors. The sensing strategy relied on the fluorescence of NCDs at 345 nm, which was selectively reduced by gefitinib based on the inner filter effect (IFE). With a broad linear range of 0.025–30 μg/mL and a low limit of detection of 5.5 ng/mL, the probe was successfully applied to the detection of gefitinib in human serum samples, demonstrating strong practicality, affordability, and high accuracy. The proposed sensor is simple in design, fast in detection and cost-effective, and exhibits promising application in drug real-time analysis.

One-Pot Synthesis of Green-Emitting Nitrogen-Doped Carbon Dots from Xylose

Carbon dots (CDs) are interesting carbon nanomaterials that exhibit great photoluminescent features, low cytotoxicity, and excellent water stability and solubility. For these reasons, many fields are starting to integrate their use for a variety of purposes. The catalytic performance of VOPO4 has been evaluated in the synthesis of nitrogen-doped carbon dots (N-CDs). The synthesis reaction was carried out at 180 °C using VOPO4 as a heterogeneous catalyst for 2 to 4 h of reaction time. After reaction, the N-CDs were purified using a novel method for the protection of the functional groups over the surfaces of the N-CDs. The morphological, superficial, and photoelectronic properties of the N-CDs were thoroughly studied by means of TEM, HRTEM, XPS, and photoluminescence measurements. The conversion of the carbon precursor was followed by HPLC. After three catalytic runs, the catalyst was still active while ensuring the quality of the N-CDs obtained. After the third cycle, the catalyst was regenerated, and it recovered its full activity. The obtained N-CDs showed a great degree of oxidized groups in their surfaces that translated into high photoluminescence when irradiated under different lasers. Due to the observed photoelectronic properties, they were then assayed in the photocatalytic degradation of methyl orange.

Physicochemical properties of in situ microwave-assisted germanium oxide modified nitrogen-doped carbon dots

Preparation of carbon dots (CDs) and nitrogen-doped carbon dots (NCDs) with germanium oxide (GeO2/GeO) using a facile one-step microwave-assisted synthesis procedure is presented. Iso-ascorbic acid, urea and Ge-132 were used as carbon, nitrogen and germanium sources, respectively. Studies have shown that the CDs, NCDs and GeO2/GeO nanoparticles individually have excellent qualities for bio-imaging applications including photoluminescence, biocompatibility, good stability and low toxicity. While CDs have been thoroughly explored in literature, CDs with germanium oxide on their surface are an avenue that has scarce information. Hence the synthesis and physicochemical characterizations of CDs- /NCDs- GeO2/GeO composites were studied using different microscopic and spectroscopic techniques to explore their compatibility for bio-imaging applications. In the presence of Ge, the approximate particle sizes of both the CDs and NCDs increased from 2.5 nm to 5.8 nm and the spherical or quasi-spherical shape was maintained. The X-ray photoelectron spectroscopy survey spectrum showed that the surface of Iso-N-Ge-CDs contained nitrogen and germanium, indicating the successful synthesis of nitrogen-doped carbon dots (NCDs) with germanium oxide (GeO2/GeO). Photoluminescence emissions of longer wavelengths suitable for cell imaging were observed for Iso-N-Ge-CDs (350 nm) and Iso-Ge-CDs (430 nm) and the Iso-N-Ge-CDs are able to fluoresce under the red and blue wavelengths. The Ge-NCDs demonstrated excitation-dependent emission wavelength behaviour, pH sensitivity and Fe3+ sensitivity which may be used as a probe for Fe3+ metal ions and intracellular pH measurements.

Sustainable route for synthesis of nitrogen-doped carbon dots with high efficiency for iron(III) and copper(II) ions detection

Sustainable route for synthesis of nitrogen-doped carbon dots with high efficiency for iron(III) and copper(II) ions detection

Synthesis of nitrogen-doped carbon dots with 3-aminoquinoline and citric acid as an absorbent in full ultraviolet bands and application of transparent sunscreen umbrella

In recent years, as the global climate continues to deteriorate, the harm of ultraviolet(UV) radiation to the human body is increasing, but the development of commercial UV-blocking products has not followed the corresponding update. Carbon dots (CDs) are excellent candidates for UV absorbers because of their multi-functional groups, high stability, and low toxicity. In this study, full UV bond absorbing CDs (3A-CDs) were synthesized by a one-step hydrothermal method using anhydrous Citric acid(CA) and 3-aminoquinoline as raw materials. The 3A-CDs have super high UV absorption efficiency, light-aging resistance, and acid and alkaline resistance. Subsequently, different concentrations of 3A-CDs were doped into PVA to prepare 3A-CDs@PVA films with excellent full UV bond absorption and good mechanical properties. Finally, 3A-CDs@PVA films were sandwiched between two pieces of transparent umbrella cloth. The 0.3 wt% 3A-CDs@PVA film with transparent umbrella cloth can achieve a blocking efficiency of more than 97.2% in the full UV bands. Also, SPF is greater than 50, PFA is PA++++, and the visible light transmittance is as high as 93.8%. This study provides a new application and prospect for the development of CDs and their composite products into new, efficient, and durable UV-blocking products.

Synthesis of Nitrogen-Doped Carbon Dots from Nanocrystalline Cellulose by Pyrolysis Method as Hg2+ Detector

The synthesis of modified carbon dots (N-CDs) from nanocrystalline cellulose, as the carbon source, with the combination of urea and ethylenediamine, as nitrogen dopant agents, was successfully carried out by pyrolysis at 300°C. The N-CDs

Facile synthesis of nitrogen-doped carbon dots as sensitive fluorescence probes for selective recognition of cinnamaldehyde and l-Arginine/l-Lysine in living cells

The disorder of amino acid metabolism and the abuse of small molecule drugs pose serious threats to public health. However, due to the limitations of existing detection technologies in sensing cinnamaldehyde (CAL) and l-Arginine/l-Lysine (l-Arg/l-Lys), there is an urgent need to develop new sensing strategies to meet the severe challenges currently facing. Herein, nitrogen-doped carbon dots (N-CDs) were developed using a simple one-pot hydrothermal carbonization method. These N-CDs exhibited numerous distinctive characteristics such as excellent photoluminescence, high water dispersibility, favorable biocompatibility, and superior chemical inertness. Strikingly, the as-prepared CDs as a highly efficient fluorescent probe possessed significant sensitivity and selectivity toward CAL and l-Arg/l-Lys over other analytes with a low detection limit of 58 nM and 16 nM/18 nM, respectively. The fluorescence of N-CDs could be quenched by CAL through an electron transfer process. Then, the strong electrostatic interaction between l-Arg/l-Lys and N-CDs induced the efficient fluorescence recovery. More importantly, the outstanding biosafety and excellent analyte-responsive fluorescence characteristics of N-CDs have also been verified in living cells as well as in serum and urine. Overall, the N-CDs had a wide application prospect in the diagnosis of amino acid metabolic diseases and small molecule drug sensing.

Green Synthesis of Nitrogen-Doped Carbon Dots from Fresh Tea Leaves for Selective Fe3+ Ions Detection and Cellular Imaging.

In this research, we successfully developed a green, economical and effective one–step hydrothermal method for the synthesis of fluorescent nitrogen–doped carbon dots (N–CDs) by utilizing fresh tea leaves and urea as the carbon and nitrogen sources, respectively. The obtained N–CDs were characterized by TEM, XPS and FT–IR. We found that the N–CDs were near–spherical with an average size of about 2.32 nm, and contained abundant oxygen and nitrogen functional groups. The N–CDs exhibited bright blue fluorescence under ultraviolet illumination, with the maximum emission at 455 nm. Meanwhile, the as–prepared N–CDs could be selectively quenched by Fe3+ ions. The quenching of N–CDs is linearly correlated with the concentration of Fe3+ in the range of 0.1–400 μM with a low detection limit of 0.079 μM. Significantly, the N–CDs present excellent biocompatibility and high photostability. The results also depict that multicolor fluorescence is displayed under a fluorescence microscope and successfully applied for the detection of intracellular Fe3+. To sum up, the fluorescent N–CDs are expected to be a sensitive detection probe for Fe3+ in biological systems.

Reuse of waste Myrica rubra for green synthesis of nitrogen-doped carbon dots as an “on-off-on” fluorescent probe for Fe3+ and ascorbic acid detection

As one kind of high nutrition fruits, abandoned Myrica rubra causes great waste due to short storage period. For resource utilization, we herein fabricated the Myrica rubra-based N-doped carbon dots (MN-CDs) by a facile/green hydrothermal method. MN-CDs, fabricated from four regions of China, displayed significant differences in their corresponding fluorescence intensities (FIs). Interestingly, different batches of waxberry samples from the same region (Wenzhou, China) exhibited slight differences in their FIs, and also an excellent anti-photobleaching and anti-salt capacity. Based on Fe3+-triggered quenching effect and fluorescent recovery by redox reaction of AA and Fe3+, MN-CDs were employed to construct an “on-off-on” switch probe for sequential detection of Fe3+ and ascorbic acid (AA). Through Zeta potential, UV spectrum, Stern-Volmer equation, and valence-conduction band theory, the Fe3+-triggered quenching belonged to a static quenching process, which resulted from the synergistic contribution of inner filtering effect and photo-induced electron transfer mechanisms. The linear ranges for Fe3+ and AA detections were 1–1000 and 0.1–1000 mM. The limits of detection were 0.3 μM for Fe3+ in environmental waters, and 0.03 μM for AA in pharmaceutical tablets and fruit juice samples. Under 365-nm UV lamp, the color changes of test papers were easily observed from dark blue and bright blue in the presence of Fe3+ and AA, and thus the MN-CDs-based switch probe could be satisfactorily used for visually qualitative detection of Fe3+ and AA outdoor with our naked eyes. To sum up, MN-CDs not only realize resource reutilization of abandoned Myrica rubra, but also offer an convenient outdoor approach for qualitative detection of Fe3+ and AA in complex matrices.

One-pot synthesis of nitrogen-doped carbon dots for sensing of Co2+ and tetracycline antibiotics, biological imaging, and fluorescent inks

One-pot synthesis of nitrogen-doped carbon dots for sensing of Co2+ and tetracycline antibiotics, biological imaging, and fluorescent inks

Microwave-assisted synthesis of nitrogen-doped carbon dots using prickly pear as the carbon source and its application as a highly selective sensor for Cr(VI) and as a patterning agent.

Preparation of water-dispersible carbon dots from inexpensive natural carbon precursors and its application for purposes such as sensing, bio-imaging and patterning agents is showing growing interest in recent years. In this study, we have reported the preparation of nitrogen-doped carbon dots (N-CDs) using prickly pear as the carbon source and m-xylylenediamine as the nitrogen source using a one-step microwave-assisted synthetic process. The N-CDs prepared were characterized on the basis of elemental analysis, XPS, powder-XRD, FT-IR, Raman, TEM, UV-vis and fluorescence spectroscopy. Doping of nitrogen in the N-CDs made them highly fluorescent and the study on their ion-recognition property revealed that they detect highly toxic Cr(VI) with high selectivity and sensitivity (LOD, 0.04 μM) and without interference from the other ions used in this study. By immobilizing these N-CDs onto filter paper, sensor strips were prepared for on-site monitoring/field applications and they were successfully used for the detection of Cr(VI) in water. Detailed spectral analysis revealed that the mechanism of Cr(VI) sensing involved a phenomenon called the "inner filter effect" and analysis of the fluorescence lifetime data suggested the "static quenching" of fluorescence intensity. These N-CDs were used to prepare fluorescent carbon ink and were successfully used as patterning agents.

Synthesis, solution and solid-state fluorescence of nitrogen self-doped carbon dots derived from Chlorella pyrenoidosa

In this work, we report a simple and green approach for the synthesis of nitrogen-doped carbon dots from Chlorella pyrenoidosa, hereafter referred to as CP-CDs, via microwave-assisted hydrothermal carbonization without any additives. The effects of temperature (170–210 °C) and time (1–3 h) on the structure, functional groups, optical properties and formation route of the CP-CDs were assessed in detail. FTIR, XPS, and XRD results showed that high temperatures promoted the nitrogen doping level, resulting in good fluorescence intensity and high quantum yields (QYs). As the reaction temperature increased from 170 °C to 210 °C, the amount of nitrogen doped into the CP-CDs increased significantly from 4.1% to 11.9% and the absolute QY improved from 1.79% to 2.31%. The CP-CDs solutions exhibited excitation-dependent blue fluorescence from 360 to 527 nm with the excitation from 280 to 460 nm. The optimal preparation temperature and time for CP-CDs aqueous solution were 210 °C and 2 h, respectively. The solid-state CP-CDs without any further processing exhibited self-quenching resistant performance. The obtained CP-CDs as fluorescence inks could be used in security printing.

One Spot Microwave Synthesis and Characterization of Nitrogen-Doped Carbon Dots with High Oxygen Content for Fluorometric Determination of Banned Sudan II Dye in Spice Samples.

A simple microwave-assisted synthesis of nitrogen-doped carbon dots with high oxygen content (O-N-CDs) was carried out with citric acid as a carbon source and 2,4-diamino-6-methyl-1,3,5-triazine as a nitrogen source in triethylene glycol (TEG) media. It was determined by SEM analysis that O-N-CDs consisted of particles of different sizes and shapes. Transmission electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD) analysis confirmed that O-N-CDs have a graphitic structure. Moreover, they showed a high fluorescence property based on the excitation wavelength. Therefore, a new fluorometric method was developed for the determination of banned food dye Sudan II by using the O-N-CDs. The proposed method was used in the determination of Sudan II in spiked spice samples. The detection limit was 0.6mg L-1 and the linear range was 0-8mg L-1.

Simple and Sensitive Multi-components Detection Using Synthetic Nitrogen-doped Carbon Dots Based on Soluble Starch.

Although carbon dots (CDs) as fluorescent sensors have been widely exploited, multi-component detection using CDs without tedious surface modification is always a challenging task. Here, two kinds of nitrogen-doped CDs (NCD-m and NCD-o) based on soluble starch (SS) as carbon source were prepared through one-pot hydrothermal process using m-phenylenediamine and o-phenylenediamine as nitrogenous dopant respectively. Through fluorescence "on-off" mechanism of CDs, NCD-m and NCD-o could be used as a fluorescence sensor for detection of Fe 3+ and Ag + with LOD of 0.25 and 0.51μM, respectively. Additionally, NCD-m could be used for indirect detection of ascorbic acid (AA) with LOD of 5.02μM. Moreover, fluorescence intensity of NCD-m also exhibited the sensitivity to pH change from 2 to 13. More importantly, Both NCD-m and NCD-o had potential application for analysis of complicated real samples such as tap water, Vitamin C tablets and orange juice. Ultimately, the small size of NCD-m could contribute to reinforcing intracellular endocytosis, which allowed them to be used for bacteria imaging. Obviously, these easily obtainable nitrogen-doped CDs were able to be used for multi-components detection. Strategy for synthesis of nitrogen-doped carbon dots (NCDs) and a schematic for fabrication of as-prepared NCDs for detection of Fe 3+, Ag + and ascorbic acid (AA).

Facile synthesis of nitrogen-doped carbon dots (N-CDs) and N-CDs/NiO composite as an efficient electrocatalyst for oxygen evolution reaction

Nitrogen-doped carbon dots (N-CDs), derived from the biomass (anthocyanin), are the novel additive to the nanocarbon materials, which is expected to bring a wide spectrum of novel applications. Moreover, metallic oxides are emerging for their unique potential for electrocatalysis. Herein, we report the synthesis of N-CDs for the selective detection of Fe3+ with a limit of detection of 2.57 μM in the range of 5–60 μM using ethylenediamine and H2O2 by a hydrothermal method. The obtained N-CDs displayed a spherical morphology with a particle size range of 2–7 nm and emitted blue luminescence at 394 nm under excitation at 319 nm. Meanwhile, we have demonstrated the fabrication of cost-efficient electrocatalysts for oxygen evolution reaction (OER) in an alkaline medium, employing N-CDs. Owing to the successful incorporation of N-CDs into NiO nanospheres, the resulting N-CDs/NiO with large surface areas, fast charge transfer, and increased conductivity vastly improved the catalytic activity. Remarkably, the optimal of N-CDs/NiO composite requires the overpotential of only 380 mV at a current density of 10 mA cm−2 and a relatively low Tafel slope of 57.96 mV dec−1 compared with pure NiO. These results open up a facile route for the application of N-CDs and offer prospects for CD-metal hybrids as high OER catalysts in electrochemical energy devices.

Mimicking Peroxidase-Like Activity of Nitrogen-Doped Carbon Dots (N-CDs) Coupled with a Laminated Three-Dimensional Microfluidic Paper-Based Analytical Device (Laminated 3D-μPAD) for Smart Sensing of Total Cholesterol from Whole Blood.

This work presents a simple hydrothermal synthesis of nitrogen-doped carbon dots (N-CDs), fabrication of microfluidic paper-based analytical device (μPAD), and their joint application for colorimetric determination of total cholesterol (TC) in human blood. The N-CDs were characterized by various techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD), and the optical and electronic properties of computational models were studied using the time-dependent density functional theory (TD-DFT). The characterization results confirmed the successful doping of nitrogen on the surface of carbon dots. The N-CDs exhibited high affinity toward 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)-diammonium salt (ABTS) with the Michaelis-Menten constant (KM) of 0.018 mM in a test for their peroxidase-like activity. Particularly, since hydrogen peroxide (H2O2) is the oxidative product of cholesterol in the presence of cholesterol oxidase, a sensitive and selective method of cholesterol detection was developed. Overall, the obtained results from TD-DFT confirm the strong adsorption of H2O2 on the graphitic N positions of the N-CDs. The laminated three-dimensional (3D)-μPAD featuring a 6 mm circular detection zone was fabricated using a simple wax screen printing technique. Classification of TC according to the clinically relevant criteria (healthy, <5.2 mM; borderline, 5.2-6.2 mM; and high risk, >6.2 mM) could be determined by the naked eye within 10 min by simple comparison using a color chart. Overall, the proposed colorimetric device serves as a low-cost, rapid, simple, sensitive, and selective alternative for TC detection in whole blood samples that is friendly to unskilled end users.

One-pot synthesis of nitrogen-doped carbon dots for highly sensitive determination of cobalt ions and biological imaging

In this work, a facile, economical and green method for the preparation of nitrogen-doped carbon dots (N-CDs) was established via hydrothermal synthesis using p-phenylenediamine and asparagine. The as-prepared N-CDs were characterized by Transmission electron microscopy (TEM), X-ray diffraction patterns (XRD), Raman, Fourier transform infrared spectroscopy (FT-IR) and other methods. Furthermore, the N-CDs showed high sensitivity toward cobalt (II) ion (Co2+). Interestingly, the fluorescence of N-CDs was quenched linearly in the 0.3–65 μM Co2+ concentrations range, under the optimum conditions, displaying a fast response toward Co2+ with the detection limit as low as 22 nM. Simultaneously, this method was applied in the analysis of water samples with considerable results. Finally, the N-CDs were successfully utilized as the imaging probe of live root tip tissue of Arabidopsis thaliana, demonstrating that the N-CDs possessed significant theoretical research meaning in the fields of biological correlation analysis, environmental monitoring and disease diagnosis.

Facile synthesis of nitrogen-doped carbon dots from pork liver and its sensing of 6-thioguanine based on the inner filter effect

Nitrogen-doped carbon dots were facilely synthesized from pork liver and the fluorescence quenching determination of 6-thioguanine in human serum based on the inner filter effect was achieved with the limit of detection as low as 0.75 μM.

One-step hydrothermal synthesis of nitrogen-doped carbon dots as a super selective and sensitive probe for sensing metronidazole in multiple samples.

A reliable, super selective and sensitive nitrogen-doped carbon dots (N-CDs) nanoprobe that can quantitatively and quickly detect the concentration of metronidazole (MTZ) in multiple samples was built. We first prepared the N-CDs using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC·HCl) as the precursor via a green, facile one-step hydrothermal method. The as-synthesized N-CDs were characterized by a variety of analytical and spectroscopic techniques, which revealed excitation-dependent fluorescence behavior with the maximum excitation and emission wavelengths being 335 and 370 nm, respectively. Significantly, the fluorescence emission of N-CDs underwent initial quenching upon the addition of MTZ via the inner filter effect (IFE), indicating a prospective detection method for MTZ. The linear range for MTZ detection was 0.1-250 μM, and the corresponding limit of detection (LOD) and limit of quantification (LOQ) were calculated to be only 70 nM and 233.33 nM, respectively. Moreover, due to the negligible cytotoxicity and superior biocompatibility, the fabricated N-CDs show a promising prospect for detecting MTZ in living cells. In general, our proposed N-CDs-based fluorescence sensing platform possesses super low LOD and LOQ values, wide linear range, and satisfactory selectivity, and can be applied to the detection of MTZ in multiple real samples.

One-step hydrothermal synthesis of nitrogen-doped carbon dots for high-sensitivity visual detection of nitrite and ascorbic acid.

Ascorbic acid (AA) is an indispensable vitamin for the human body and is associated with critical processes of human metabolism. However, excessive intake of AA can also have a negative impact on human health. Nitrite is a commonly used food additive, and its overdose can increase the risk of cancer. Therefore, the detection of nitrite and vitamins is generally recognized to be meaningful. In this study, red-fluorescence and yellow-fluorescence CDs (r-CDs/y-CDs) were synthesized by a one-step hydrothermal method using o-phenylenediamine as the only carbon source. These two types of CDs exhibited good detection accuracy, detection limit and selectivity towards nitrite and AA (the detection limits are 0.47 μM and 45.1 μM, respectively). The long wavelength luminescent CDs prepared in this experiment also have high quantum yield (QY), which is of great significance to the visual detection effect. Under weak acidic conditions, the amino group on the surface of r-CDs can coordinate with nitrite and react to generate diazo groups, leading to the fluorescence quenching of CDs. The coordination between the y-CDs and the amino group on the surface of AA connects the adjacent y-CDs to form aggregates, which increases the non-radiative transition of electrons and induces the fluorescence quenching of CDs. This study proposes a new idea for the preparation of carbon dots for the determination of NO2- and AA in solutions, which expands the application of fluorescent CD detection.