N-doped Carbon Nanodots Research Articles

Eosinophilic nitrogen-doped carbon dots derived from tribute chrysanthemum for label-free detection of Fe3+ ions and hydrazine

A facile, green and economic one-step hydrothermal synthesis route using widely available tribute chrysanthemum as the new carbon and nitrogen precursors towards N-doped carbon nanodots (N-CDs) is proposed. The obtained N-CDs can be employed as acidophilic fluorescent sensor for label-free sensitive and selective detection of Fe3+ in a strong acid environment with a detection limit as low as 0.001µM. In addition, the as-prepared N-CDs contain distinctive COOH groups and pyridyl nitrogen atoms on their surfaces. We further demonstrate that such wholly new N-CDs can serve as an effective fluorescent sensing platform for hydrazine. This environmentally friendly strategy offers a simple and efficient approach for preparing C-dots doped with heteroatoms from biomass in large-scale and lays a foundation for its further environmental applications.

Uniform luminescent carbon nanodots prepared by rapid pyrolysis of organic precursors confined within nanoporous templating structures

Although several methods on the preparation of carbon nanodots (CNDs) emitting throughout the visible have been recently reported, in most of the processes the product suffers from inhomogeneity in size and shape limiting their impact. Here, we report the synthesis of undoped and nitrogen-doped luminescent carbon nanodots by rapid pyrolysis using ordered mesoporous silica nanorods as confining templates. A rapid thermal decomposition (pyrolysis) within the confined dimensions of their pores leads to a highly uniform size distribution of CNDs with average sizes below 4 nm. These CNDs are synthesized in an extremely short time period (5 min of reaction) by immersion in a fluidized-bed reactor that provides heating homogeneity and ensures fast heat transfer. In addition, a rapid release of the homogeneous CNDs can be easily achieved by a simple ultrasonication-filtration step that prevents further chemical action on the mesoporous templates. The emission of both undoped and N-doped CNDs in colloidal and solid state (with an efficiency of 1–5%) originates from a combination of quantum confinement effects and the presence of oxidized surface states; N-doping introduces resonant absorption states which participate in emission. Furthermore, we present a simple model to describe the excitation-dependent/-independent mechanism of carbon nanodots.

Ultrahigh-yield synthesis of N-doped carbon nanodots that down-regulate ROS in zebrafish

Oxidative damage induced by accumulation of excessive reactive oxygen species (ROS) could result in increased chronic inflammation and thus ageing and age-related diseases. Carbonaceous nanodrugs hold great promise for ameliorating age-related diseases, and it is necessary to develop ultrahigh-yield synthesis of such nanodrugs. To improve the synthetic yield (less than 50%) of carbon nanodots (CNDs), the general choice is to screen precursors. However, no reliable concept for improving the yield has been explored over the past few decades. We are the first to propose the concept of using carbon-carbon double bonds to boost the synthetic yield and demonstrate record breaking ultrahigh-yield (85.9%) synthesis of N-doped CNDs. When the C[double bond, length as m-dash]C content increased from 14 to 56 mmol, the synthetic yield exhibited a 3.3-fold increase. Nitrogen elements are doped as pyridinic-like N and NH2, where conjugated π-systems as electron donors and pyridinic-like structures would benefit the potential down-regulated effect for ROS. N-doped CNDs exhibit an outstanding protective effect against oxidative stress via inhibiting exogenous and endogenous ROS generation, where the ROS in zebrafish are significantly reduced by 68%. Hence the concept of carbon-carbon double bond-boosted ultrahigh-yield synthesis of N-doped CNDs provides a promising strategy to be employed for carbonaceous nanodrugs aiming at preventing and curing ageing and age-related diseases.

Rapid microwave synthesis of N-doped carbon nanodots with high fluorescence brightness for cell imaging and sensitive detection of iron (III)

We rapidly prepared N-doped photoluminescent carbon nanodots (CNDs) with the one-step microwave irradiation method using diammonium hydrogen citrate as the carbon source. The as-prepared CNDs possessed quasispherical morphology and a high quantum yield of about 26.8%, which was higher than the CNDs obtained by most other microwave-assisted methods. Moreover, the luminescent CNDs could be efficiently uptaken by BGC-823 cells and CT26.WT cells, and exhibited low cytotoxicity and favorable biocompatibility, making them suitable candidates for cell imaging. In addition, the CNDs could be utilized for Fe3+ ions sensitive detection with a detection limit of 180 nM.

Fluorescence Determination of Nitrite in Water Using Prawn-Shell Derived Nitrogen-Doped Carbon Nanodots as Fluorophores

In this work, we report the synthesis of nitrogen (N)-doped carbon nanodots (N-CNDs) with an N doping level of 3.6 at. % by hydrothermal treatment of prawn shell and their application as fluorophores for selective and sensitive fluorescence detection of NO2– in water. The results demonstrate that NO2– detection by directly fluorescent quenching at N-CNDs fluorophores can achieve an analytical detection linear range up to 1.0 mM with a detection limit of 1.0 μM. The obtained detection limit of NO2– using N-CNDs fluorophores is dramatically lower than the maximum limit value of 3.0 mg L–1 (namely, 65 μM) for NO2– in drinking water ruled by the World Health Organization (WHO), which is very important for a practical application of the developed analytical method. The interference experiments indicate that only I– ions among all common anions and cations investigated show very adverse influence on selective detection of NO2– by this developed N-CNDs based fluorescent determination method. Further, the fluores...

Fe/Fe2O3 nanoparticles anchored on Fe-N-doped carbon nanosheets as bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

Electrocatalysts with high catalytic activity and stability play a key role in promising renewable energy technologies, such as fuel cells and metal-air batteries. Here, we report the synthesis of Fe/Fe2O3 nanoparticles anchored on Fe-N-doped carbon nanosheets (Fe/Fe2O3@Fe-N-C) using shrimp shell-derived N-doped carbon nanodots as carbon and nitrogen sources in the presence of FeCl3 by a simple pyrolysis approach. Fe/Fe2O3@Fe-N-C obtained at a pyrolysis temperature of 1,000 °C (Fe/Fe2O3@Fe-N-C-1000) possessed a mesoporous structure and high surface area of 747.3 m2·g−1. As an electrocatalyst, Fe/Fe2O3@Fe-N-C-1000 exhibited bifunctional electrocatalytic activities toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media, comparable to that of commercial Pt/C for ORR and RuO2 for OER, respectively. The Zn-air battery test demonstrated that Fe/Fe2O3@Fe-N-C-1000 had a superior rechargeable performance and cycling stability as an air cathode material with an open circuit voltage of 1.47 V (vs. Ag/AgCl) and a power density of 193 mW·cm−2 at a current density of 220 mA·cm−2. These performances were better than other commercial catalysts with an open circuit voltage of 1.36 V and a power density of 173 mW·cm−2 at a current density of 220 mA·cm−2 (a mixture of commercial Pt/C and RuO2 with a mass ratio of 1:1 was used for the rechargeable Zn-air battery measurements). This work will be helpful to design and develop low-cost and abundant bifunctional oxygen electrocatalysts for future metal-air batteries.

One-Step Synthesis and Characterization of N-Doped Carbon Nanodots for Sensing in Organic Media.

Photoluminescent nitrogen-doped carbon nanodots (N-doped CNDs) soluble in organic media are synthesized in a one-step synthesis from a single-source precursor (an amphiphilic polymer), which exhibits a very high quantum yield (QY = 78%), excitation wavelength-dependent emission, and upconversion emission properties. The evolution of N-doped CND formation is studied via ultraviolet-visible and photoluminescence spectroscopy. Their analytical application as an effective sensor for the direct determination of nitroaromatic explosives and byproducts is shown based on their selective response via a fluorescence quenching mechanism. The proposed method is validated in soil samples by directly using the sensor in organic media without any further treatment or additional functionalization, which is an interesting aspect for practical applications.

High yield luminescent N-doped carbon nanodots derived from nitrogen-containing biomass for bioimaging

High yield luminescent N-doped carbon nanodots derived from nitrogen-containing biomass for bioimaging

Biodegradable Nitrogen-Doped Carbon Nanodots for Non-Invasive Photoacoustic Imaging and Photothermal Therapy.

Multifunctional nanoparticles have been widely investigated for biomedical applications, such as imaging, therapy, and drug delivery. Especially, photoactive nanoparticles have received great attention as theranostic agents because of their heat-generating abilities after exposure to laser irradiation. However, photostability and safety issues have been the technical hurdles for further clinical applications. Here, we designed nitrogen (N)-doped carbon nanodots (N-CNDs) that have strong absorption in the near-infrared region, high photostability, and excellent biodegradability. Optimized N-CNDs can be utilized not only as a new photoacoustic (PA) imaging agent but also as a superior photothermal therapy (PTT) agent in vivo because of their strong optical absorption at a specific wavelength. We used N-CNDs to perform in vivo/ex vivo noninvasive PA imaging of sentinel lymph nodes via local delivery and performed PTT for cancer ablation therapy. Finally, biodegradation and renal clearance were confirmed by performing whole-body PA monitoring and a degradation test.

Shrimp-shell derived carbon nanodots as carbon and nitrogen sources to fabricate three-dimensional N-doped porous carbon electrocatalysts for the oxygen reduction reaction.

Development of cheap, abundant and metal-free N-doped carbon materials as high efficiency oxygen reduction electrocatalysts is crucial for their practical applications in future fuel cell devices. Here, three-dimensional (3D) N-doped porous carbon (NPC) materials have been successfully developed by a simple template-assisted (e.g., SiO2 spheres) high temperature pyrolysis approach using shrimp-shell derived N-doped carbon nanodots (N-CNs) as carbon and nitrogen sources obtained through a facile hydrothermal method. The shrimp-shell derived N-CNs with a product yield of ∼ 5% possess rich surface O- and N-containing functional groups and small nanodot sizes of 1.5-5.0 nm, which are mixed with surface acidification treated SiO2 spheres with an average diameter of ∼ 200 nm in aqueous solution to form a N-CNs@SiO2 composite subjected to a thermal evaporation treatment. The resultant N-CNs@SiO2 composite is further thermally treated in a N2 atmosphere at different pyrolysis temperatures, followed by acid etching, to obtain 3D N-doped porous carbon (NPC) materials. As electrocatalysts for oxygen reduction reaction (ORR) in alkaline media, the experimental results demonstrate that 3D NPC obtained at 800 °C (NPC-800) with a surface area of 360.2 m(2) g(-1) exhibits the best ORR catalytic activity with an onset potential of -0.06 V, a half wave potential of -0.21 V and a large limiting current density of 5.3 mA cm(-2) (at -0.4 V, vs. Ag/AgCl) among all NPC materials investigated, comparable to that of the commercial Pt/C catalyst with an onset potential of -0.03 V, a half wave potential of -0.17 V and a limiting current density of 5.5 mA cm(-2) at -0.4 V. Such a 3D porous carbon ORR electrocatalyst also displays superior durability and high methanol tolerance in alkaline media, apparently better than the commercial Pt/C catalyst. The findings of this work would be valuable for the development of low-cost and abundant N-doped carbon materials from biomass as high performance metal-free electrocatalysts.

Shrimp-shell derived carbon nanodots as precursors to fabricate Fe,N-doped porous graphitic carbon electrocatalysts for efficient oxygen reduction in zinc–air batteries

Shrimp-shell derived N-doped carbon nanodots as precursors are used to fabricate Fe, N-doped porous carbon electrocatalysts exhibiting superior ORR activity in zinc–air batteries.

Co/CoO nanoparticles immobilized on Co-N-doped carbon as trifunctional electrocatalysts for oxygen reduction, oxygen evolution and hydrogen evolution reactions.

Co/CoO nanoparticles immobilized on Co-N-doped carbon were successfully developed using shrimp-shell derived N-doped carbon nanodots as precursors by a combined approach of polymerization and pyrolysis, as electrocatalysts exhibiting trifunctional catalytic activities toward oxygen reduction, oxygen evolution and hydrogen evolution reactions and high performance in rechargeable zinc-air batteries.

High-yield synthesis of strong photoluminescent N-doped carbon nanodots derived from hydrosoluble chitosan for mercury ion sensing via smartphone APP

Photoluminescent carbon nanodots (CNDs) have offered considerable potential to be used in biomedical and environmental fields including live cell imaging and heavy metal ion detection due to their superior quantum emission efficiencies, ability to be functionalized using a variety of chemistries and apparent absence of toxicity. However, to date, synthetic yield of CNDs derived from biomass via hydrothermal carbonization is quite low. We report here the synthesis of nitrogen-doped carbon nanodots (N-doped CNDs) derived from hydrosoluble chitosan via hydrothermal carbonization. The synthetic yield could reach 38.4% which is 2.2–320 times increase compared with that from other biomass reported so far. These N-doped CNDs exhibited a high quantum yield (31.8%) as a consequence of nitrogen incorporation coincident with multiple types of functional groups (C=O, O–H, COOH, and NH2). We further demonstrate applications of N-doped CNDs as probes for live cell multicolor imaging and heavy metal ion detection. The N-doped CNDs offered potential as mercury ion sensors with detection limit of 80nM. A smartphone application (APP) based on N-doped CNDs was developed for the first time providing a portable and low cost detection platform for detection of Hg2+ and alert of heavy metal ions contamination.

A novel electrochemiluminescence sensor based on [formula omitted] carbon nanodots system for the detection of bisphenol A

A novel Ru(bpy)32+-based electrochemiluminescence (ECL) sensing platform, using N-doped carbon nanodots (N–C dots) as co-reactant, was established for the sensitive and selective detection of bisphenol A (BPA). N–C dots not only could enhance the ECL signal, but also significantly improved the reproducibility and stability of Ru(bpy)32+ ECL system. The developed ECL sensing system was sensitive to detect BPA based on its efficient quenching effect on Ru(bpy)32+/N−C dots. The N–C dots-enhanced ECL mechanism and BPA-quenched ECL mechanism were investigated. Under the optimum conditions, the inhibited ECL intensity was in good linear relationship versus the concentration of BPA in the range of 0.03–1.0 μM with the detection limit of 10 nM. The relative standard deviation (RSD) for 25 successive measurements with one sensor was 1.1% and for eight different sensors was 2.5%, respectively. The fabricated sensing platform was successfully applied for the detection of BPA in baby bottle and nipple, and relatively satisfactory recoveries were obtained.

Multifunctional Nitrogen-Doped Carbon Nanodots for Photoluminescence, Sensor, and Visible-Light-Induced H2 Production.

Herein, multifunctional N-doped carbon nanodots (NCNDs) were prepared through the one-step hydrothermal treatment of yeast. Results show that the NCNDs can be used as a new photocatalyst to drive the water-splitting reaction under UV light. Moreover, the NCNDs can efficiently catalyze the hydrogen evolution reaction. Under visible-light irradiation, Eosin Y-sensitized NCNDs exhibit excellent activity for hydrogen evolution. The hydrogen evolution rate of NCNDs (without any modification and co-catalyst) reaches 107.1 μmol h(-1) (2142 μmol g(-1) h(-1) ). When Pt is loaded on the NCNDs, the hydrogen evolution rate reaches 491.2 μmol h(-1) (9824 μmol g(-1) h(-1)) under visible-light irradiation. In addition, the NCNDs show excellent fluorescent properties and can be applied as a fluorescent probe for the sensitive and selective detection of Fe(3+) .