As-prepared Nitrogen-doped Carbon Dots Research Articles

Highly fluorescent nitrogen-doped carbon dots derived from jengkol peels (Archindendron pauciflorum) by solvothermal synthesis for sensitive Hg2+ ions detection

A facile synthesis method involving a one-step solvothermal method is demonstrated in producing fluorescent nitrogen-doped carbon dots (N-CDs) by employing biomass waste (Jengkol peels) and ethylenediamine as a source for carbon and nitrogen. The synthesized N-CDs are spherical nanoparticles with an average size of 4.495 nm, exhibit solubility in water, emit bluish-green fluorescence and a high quantum yield of up to 42%. By using UV–Visible, FTIR, XPS, HR-TEM and Photoluminescence analysis, the as-prepared N-CDs were verified. We demonstrate that nitrogen doping increases fluorescence emission intensity to its radiative recombination of the π − π∗ transitions at CC and n − π∗ at CO or CN. an optimized excitation at 370 nm, the N-CDs exhibited strong PL emission at 522 nm. Under optimized conditions, N-CDs can be used to detect Hg2+ ions based on quenched fluorescence phenomenon. The result reveals excellent selectivity and sensitivity to Hg2+ ions with a detection range of 0.5 μM–4.5 μM. The resulting N-CDs may be used for detecting Hg2+ ions in cosmetics and tap water.

Dual photoluminescence emission carbon dots for ratiometric optical dual-mode and smartphone-integrated visual detection of mercury ion

Development of detection platforms having portable, easy-to-use, and cost-effective designs is essential for environmental monitoring as well as food safety inspection. Herein, we proposed a smartphone-based handheld sensing strategy integrated with nitrogen-doped carbon dots (NCDs) test strip by employing three-dimensional (3D) printing technology for visual detection of Hg2+. Using this handheld detection platform, the FL color of test strips varied from red to purple with the increase of Hg2+ concentration. A great linear response between the R/B value and Hg2+ concentration in the range of 0 μM− 125 μM was shown, with a detection limit of 0.024 μM. Further, the constructed platform was applied for quantitative detection of Hg2+ in real water samples. Interestingly, as-prepared NCDs allowed the monitoring of Hg2+ with the dual-signal ratiometric model. Finally, the NCDs were used to detect Hg2+ in biological systems with satisfactory results. This work will contribute to the new strategy to design easy-to-use and user-friendly devices for on-site quantitation of targets.

Solvothermal preparation of nitrogen-doped carbon dots with PET waste as precursor and their application in LEDs and water detection

Developing novel, alternative ways to recycle PET waste, which has an important influence on reduction of landfilling and CO2 emissions, has always been a research hot spot for industry and academy. In this work, PET waste was adopted as precursor for the preparation of nitrogen-doped Carbon Dots (NCDs). Firstly, PET oligomers were obtained by alcoholysis of PET waste with ethylene glycol. Then, the mixture without isolation and purification as well as pyromellitic acid dianhydride and urea were adopted as precursors for the preparation of NCDs by solvothermal method with tetrahydrofuran (THF) as solvent. The as-prepared NCDs has a spherical structure with an average particle size of 2.3 nm. What is more, NCDs exhibit excitation-independent emission properties, the largest excitation peak and emission peak of NCDs located in 360 nm and 470 nm, and the fluorescence quantum yield is 48.16 %. In term of application, NCDs are dispersed in PMMA and loaded on 365 nm and 430 nm LED chips to obtain LED devices emitting yellow light ((0.55, 0.44), 2018 K) and warm white light ((0.37, 0.31), 3783 K), respectively. In addition, NCDs could be adopted as fluorescent probe for the construction of sensor for water in organic solvents based on dynamic quenching of NCDs, and the limit of detection (LOD) is 0.00001 %.

Preparation of fluorescent nitrogen-doped carbon dots for highly selective on-off detection of Fe3+ ions in real samples

In this work, nitrogen-doped carbon dots (N-CDs) based fluorescent probes were synthesized using m-phenylenediamine and citric acid as both nitrogen and carbon source through the hydrothermal method. The structural and optical properties of synthesized N-CDs were investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV–vis spectroscopy, Zeta potential, and photoluminescence (PL). The water-soluble N-CDs showed a narrow size distribution within 6–8 nm. The emission peak with maximum intensity for N-CDs was 535 nm at the excitation wavelength of 470 nm, and the quantum yield of N-CDs was 30.2%. The as-prepared N-CDs could be selectively quenched by Fe 3+ ions with a limit of detection (LOD) of 13.8 nM in a linear range from 0.002 μM to 8 μM. Furthermore, examining the validity of the present fluorescence N-CDs probe showed that the proposed method has enough reliability and sensitivity for detecting Fe 3+ ions in an acceptable recovery range from 97 to 106.4% in the real samples. The probe indicated high stability and selectivity to be a suitable candidate for environmental applications. • N-doped CDs were used in the selective and sensitive detection of Fe 3+ ions with an excellent limit of detection. • The N-CDs have several distinct advantages: Water solubility, biocompatibility, high QY of 30.2%, and emission at 535 nm (λ ex = 470 nm). • Develop a photoluminescence probe that is reliable for detecting Fe 3+ in real samples. • The NCDs fluorescence quenching by Fe 3+ is most likely caused by a static quenching mechanism.

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.

A Cu2+-assisted fluorescence switch biosensor for detecting of coenzyme A employing nitrogen-doped carbon dots

Herein, a simple and sensitive Cu2+-assisted fluorescence switch biosensor for the detection of coenzyme A (CoA) was proposed by employing nitrogen-doped carbon dots (N-CDs). N-CDs were successfully synthesized by sodium alginate and melatonin via pyrolysis. The as-prepared N-CDs were spherical with an average diameter of 2.8 nm and exhibited blue emission (λem = 480 nm, λex = 360 nm) with a high fluorescence quantum yield of 50.2%. The intense blue emission of the N-CDs could be effectively quenched by copper ions through the formation of the N-CDs/Cu2+ complex. With the introduction of CoA, a more stable CoA/Cu2+ complex formed, leading to the fluorescence recovery of N-CDs. Based on this strategy, CoA could be sensitively and selectively detected with a good linear relationship in the range of 0.02–5.00 μM and with a detection limit of 12 nM. In addition, this sensor was applied for CoA detection in human serum samples with satisfactory recovery. The results showed great potential towards advancing applications in CoA-dependent bioresearch.

Determination of thiourea based on the reversion of fluorescence quenching of nitrogen doped carbon dots by Hg2.

Herein, a facile and quick strategy to detect thiourea was conducted based on the reversion of fluorescence quenching of nitrogen doped carbon dots (NCDs) by Hg2+. The NCDs with good water solubility and 17% of quantum yield was synthesized by one-step hydrothermal method, using ammonium citrate and dextrin as carbon source and nitrogen source, respectively. The fluorescence of NCDs was obviously quenched by Hg2+ and can be recovered, due to stronger interaction between thiourea and Hg2+. There was a good linear relationship between the recovered fluorescence and the concentration of thiourea within range of 0.90-10.0 μM and the detection limit for thiourea detection was 0.15 μM. The as-prepared NCDs can be used for determination of thiourea in tap water, lake water and rice flour products, and the spike recoveries were between 91.6 and 108%.

Highly photoluminescent and pH sensitive nitrogen doped carbon dots (NCDs) as a fluorescent sensor for the efficient detection of Cr (VI) ions in aqueous media.

Fluorescent carbon dots (CDs) are contemporary class of fluorescent materials that has emerged recently and have gathered increasing attention due to its excellent properties as compared to traditional semiconductor quantum dots. CDs have lucrative benefits of less toxicity, biocompatibility, eco friendliness, tunable fluorescence, high chemical and photostability, effortless synthesis routes and uncomplicated surface modifications and functionalization. In the present work, nitrogen-doped carbon dots (NCDs) were prepared by a facile hydrothermal process using l-ascorbic acid and ethylene diamine as precursors. The as-prepared NCDs were hydrophilic in nature and could remain stable for several weeks. NCDs displayed bright blue fluorescence under UV light irradiation and also exhibited an extensive range of emission spectra in the visible region to infra-red region based upon the excitation wavelength. NCDs possessed quasi-spherical morphology and high density growth. NCDs were further utilized as nanoprobes for the pH sensing and proficient sensitive and selective detection of chromium (VI) ions present in aqueous phase. Under augmented modifications and conditions, the photoluminescence intensity of NCDs against various micromolar concentration of chromium (VI) ions presented a linear relationship, as per Stern-Volmer equation. The calibration curve was found to be linear in the range of 0-4 μM and from the slope of the linear curve, the limit of detection (LOD) was calculated to be 2.598 nM. The Stern-Volmer calibration curve was also plotted against different temperatures, verifying static quenching mechanism. Therefore, the as synthesized NCDs can be successfully demonstrated for the efficient pH sensing and the detection of Cr (VI) ions.

Synthesis of Fluorescent Nitrogen-Doped Carbon Quantum Dots for Selective Detection of Picric Acid in Water Samples.

In this work, fluorescent nitrogen-doped carbon dots (N-CDs) were pyrolysis synthesized using edetic acid and acrylamide as precursors without further surface modication. The as-prepared N-CDs were mono-dispersed spherical nanoparticles with an average diameter of 3.25 nm. The blue fluorescence emission was dependent of the excitation wavelengths, releasing stable and strong blue fluorescence under the maximum excitation wavelength. More strikingly, after adding picric acid (PA), the fluorescence of N-CDs aqueous solution gave rise to the obviously fluorescence quenching due to the inner filter effect. Under the optimum conditions, the fluorescence probe can be used for the selective detection of PA with a wide linear relationship in the range of 0.01-32 μM and the detection as low as 0.046 μM. Depending on the fluorescence quenching phenomenon, the resultant fluorescent probe for accurate and selective monitor of PA in Fenhe river samples was explored. The recoveries fell in the range of 97.13%-106.21% and the relative standard deviation was below 3% with satisfactory results.

Facile synthesis of orange fluorescence carbon dots with excitation independent emission for pH sensing and cellular imaging

High-efficient orange fluorescence nitrogen-doped carbon dots (N-CDs) were facilely prepared from P-phenylenediamine as a precursor via hydrothermal method. The as-prepared N-CDs with an average diameter of 3.65 nm displayed excitation-independent emission at 590 nm. The N-CDs demonstrated a remarkable fluorescence enhancement behavior with the increase of pH. A sigmoidal curve was well fitted using BiDoseResp equation with pKa1 3.57 and pKa2 6.01, which can be ascribed to the unique surface properties of N-CDs. Two-segment linear ranges of 2.6–4.6 and 5.0–6.8 broaden the response range to pH of the orange-emission N-CDs to some extent. The confocal fluorescent microscopic images of SMMC7721 cells were performed successfully, which demonstrating that N-CDs possess exceptional cell membrane permeability and can implement as biosensing platform to monitor pH fluctuations in living cells.

Concentration-dependent color tunability of nitrogen-doped carbon dots and their application for iron(III) detection and multicolor bioimaging

Nitrogen doping can effectly adjust the compositions and structures of carbon dots and hence enhance their fluorescence. In this work, we report a fast and low-cost route for synthesis of nitrogen-doped carbon dots (N-CDs) by microwave pyrolysis of citric acid and ammonium within 7 min. The as-prepared N-CDs contain plentiful oxygen and nitrogen functional groups, and dispaly intense fluorescence with high quantum yield of ca. 44.3% and have an average size of 1.8 nm. The obtained N-CDs exhibit highly stable against photobleaching, ionic strengths, and can be used for selective and sensitive detection of Fe(III). It is postulated that the Fe3+-mediated fluorescence quenching is attributed to the charge transfer between N-CDs and Fe3+. In particular, the emission peaks from blue to red region can be tuned by interparticle distance of N-CDs, simply by increasing the concentration of N-CDs in aqueous solution, which indicates its potential applications as a promising optical image probe in multicolor cellular imaging.

High photoluminescent nitrogen-doped carbon dots with unique double wavelength fluorescence emission for cell imaging

High photoluminescent (PL) nitrogen-doped carbon dots (N-CDs) have been synthesized using ferric ammonium citrate (FAC) and urea as raw materials by simple one-pothydrothermalprocess. The N-CDs possess bright blue fluorescence (centred at 450 nm; 36.2% quantum yield) and green fluorescence (centred at 530 nm; 47.6% quantum yield) only by adjusting the excitation wavelength from 310 nm to 510 nm. The N-CDs exhibited high N content of 32.81 wt%, low cytotoxicity, and good PL stability at different pH values, ion strengths and temperature, respectively. As-prepared N-CDs were explored for cell imaging with great biocompatibility. The remarkable properties of N-CDs indicated their potential toward sensing and biological applications.

Subcellular fluorescence imaging for BHK cell and multiple sensing based on carbon dots with two strong emission peaks

We develop a novel kind of nitrogen-doped carbon dots (N-CDs) with unprecedented properties through hydrothermal treatment of soluble starch and ethylenediamine. Such N-CDs can emit two strong emission peaks at about 450 nm and 540 nm under a single-wavelength ultraviolet-light excitation. The intensity ratios of the two emission peaks are influenced by pH values, leading to the change of fluorescent colours, which can be utilized to detect solution pH by the change of fluorescent colours. Most importantly, N-CDs can act as fluorescence probes for labelling cell nucleus of BHK cells selectively, indicating that the as-prepared N-CDs have specific targeting towards nucleus cells. In addition, the fluorescence intensity can be quenched by Fe3+ ion and restored by ascorbic acid effectively. The detection limits for Fe3+ and AA were 84.9 nM and 62.1 nM, respectively.

Bright-green-emissive nitrogen-doped carbon dots as a nanoprobe for bifunctional sensing, its logic gate operation and cellular imaging

A fluorescent nanoprobe based on nitrogen-doped carbon dots (N-CDs) with green fluorescent emission have been fabricated through a facile one-step hydrothermal treatment using catechol and triethylene tetramine as precursors. The obtained N-CDs with excellent luminescent properties and superior biocompatibility have been applied for the development of a bifunctional sensor for the detection of Fe3+ and ascorbic acid (AA). Fe3+ that are tightly chelating the surface of N-CDs can induce fluorescence (FL) quenching of N-CDs through photo-induced electron transfer (PET). Meanwhile, the addition of AA serves to shelter the CDs effectively from being quenched by Fe3+ due to AA, as an antioxidant, enable easy-conversion of Fe3+ to reduced states (i.e. Fe3+ and Fe2+). The N-CDs are used as a facile and label-free “on-off-on” fluorescent nanoprobe for the determination of Fe3+ and AA with detection limits of 58.82nM and 0.236µM with the corresponding linear ranges of 25–200µM and 25–300µM, respectively. According to this phenomenon, an “AND” logic gate based on the novel N-CDs has been constructed. As-prepared N-CDs with negligible toxicity and perfect biocompatibility were expanded for cellular imaging and sensing Fe3+ and AA in living cell, which enlarges the application range of the N-CDs. Most importantly, the as-constructed fluorescent sensing system was successfully applied to detection of Fe3+ in tap water and the analyses of AA in fresh fruits with satisfactory results.

One-pot synthesis of fluorescent nitrogen-doped carbon dots with good biocompatibility for cell labeling.

Here we report an easy and economical hydrothermal carbonization approach to synthesize the fluorescent nitrogen-doped carbon dots (N-CDs) that was developed using citric acid and triethanolamine as the precursors. The synthesis conditions were optimized to obtain the N-CDs with superior fluorescence performances. The as-prepared N-CDs are monodispersed sphere nanoparticles with good water solubility, and exhibited strong fluorescence, favourable photostability and excitation wavelength-dependent behavior. Furthermore, the in vitro cytotoxicity and cellular labeling of N-CDs were investigated using the rat glomerular mesangial cells. The results showed the N-CDs have more inconspicuous cytotoxicity and better biosafety in comparison with ZnSe quantum dots, although both targeted the cells successfully. Considering their admirable photostability, low toxicity and good compatibility, the as-obtained N-CDs could have potential applications in biosensors, cellular imaging, and other fields.

Self-assembly of nitrogen-doped carbon dots anchored on bacterial cellulose and their application in iron ion detection

Nitrogen-doped carbon dots (N-CDs) were synthesized through a facile hydrothermal method using citric acid (CA) and ethanediamine (EDA) as precursors. A green and simple fluorescence biosensor was obtained by biosynthesis of bacterial cellulose (BC)/N-CDs. As-prepared N-CDs with rich functional groups exhibited a blue emission under the excitation wavelength of 350nm. Biosynthesis of BC/N-CDs was analyzed by Digital photos, Fourier Transform Infrared (FTIR) and Transmission Electron Microscopy (TEM). The results indicated that N-CDs were successfully anchored on BC. As-prepared BC/N-CDs were applied to the detection of Fe3+ in aqueous solution. Spectroscopic data revealed that, fluorescence materials prepared presented an sensitive response to Fe3+ in acceptable range of 0.5–600μM and ultralow detection limit of 84nM as a fluorescence sensor. Furthermore, the results also indicate that a novel BC/N-CDs composite has great potential for the detection of Fe3+ ions based on membrane fluorescence materials.

Multicolor Nitrogen-Doped Carbon Dots for Live Cell Imaging

Doping carbon dots with nitrogen atoms considerably enhances their fluorescence properties. However, the mechanism by which the carbon dots are doped is not fully understood. We developed a facile bottom-up hydrothermal carbonization (HTC) process that uses glucose and glycine as precursors for the synthesis of photoluminescent nitrogen-doped carbon dots. The as-prepared nitrogen-doped carbon dots were mono-dispersed spherical particles with a diameter of -2.8 nm. The doped nitrogen atoms assumed pyridinic type and pyrrolic type configurations to participate in the nanocrystal structure of the carbon dots. It appeared that the nitrogen doping introduces a new internal structure. The aqueous solution of nitrogen-doped carbon dots showed excitation wavelength-dependent multicolor photoluminescence. Further, these nitrogen-doped carbon dots readily entered the cytoplasm of A549 cancer cells and showed no significant cytotoxicity. The internalized nitrogen-doped carbon dots were localized to the cell membrane and cytoplasm, particularly around the nucleus. Further, the as-prepared, biocompatible, nitrogen-doped carbon dots demonstrated the potential to be used as fluorescent probes for multicolor live cell labeling, tracking, and imaging.

Enhancing the luminescence of carbon dots by doping nitrogen element and its application in the detection of Fe(III)

Carbon dots (CDs) attract great interests from scientists for their low toxicity and biocompatibility properties and their important applications in the fields of photocatalysts, batteries, bio-images and supercapacitors. Most strategies of making CDs contain several steps, which can be a time-consuming and costly procedure. In this study, nitrogen-doped CDs have been prepared by a one-step hydrothermal strategy with sodium citrate and ethylenediamine as precursors. It is found that fluorescence intensity of CDs is enhanced with the increased content of doped nitrogen, which implies that nitrogen-doped element plays an important role to improve the fluorescence intensity of CDs. Most importantly, those CDs yielded high selectivity of Fe3+, with good linearity, precision and accuracy. Hence, the as-prepared nitrogen-doped CDs could be used as probes for quantitative analysis of Fe3+ in environmental applications.

The International Agency for Research on Cancer. A brief review of its history, mission, and program.

Herein, a facile and quick strategy to detect thiourea was conducted based on the reversion of fluorescence quenching of nitrogen doped carbon dots (NCDs) by Hg2+. The NCDs with good water solubility and 17% of quantum yield was synthesized by one-step hydrothermal method, using ammonium citrate and dextrin as carbon source and nitrogen source, respectively. The fluorescence of NCDs was obviously quenched by Hg2+ and can be recovered, due to stronger interaction between thiourea and Hg2+. There was a good linear relationship between the recovered fluorescence and the concentration of thiourea within range of 0.90–10.0 μM and the detection limit for thiourea detection was 0.15 μM. The as-prepared NCDs can be used for determination of thiourea in tap water, lake water and rice flour products, and the spike recoveries were between 91.6 and 108%.