N-doped Carbon Nanoparticles Research Articles

Hierarchical Bi2O3 nanosheets and ZIF-8 derived porous nitrogen-doped carbon fibers as novel assembled nanocomposites for high-performance flexible supercapacitors

The unique design of the core–shell heterostructure is significant for obtaining electrode materials with excellent electrochemical properties. In this paper, porous carbon nanofibers (NPC@PPZ) embedded with N-doped porous carbon nanoparticles are used to construct flexible electrodes (NPC@PPZ@Bi2O3). Zeolite imidazole skeleton (ZIF)-8 and poly(methyl methacrylate) (PMMA) derived porous carbon fibers and Bi2O3 nanosheets, were utilized as the porous core and multilayer shell, respectively. The unique core and shell result in abundant pores and channels for fast ion transport and storage, high specific surface area, and additional electroactive sites. This perfect structural design enables the NPC@PPZ@Bi2O3 composite electrode to have excellent electrochemical performance. The results show that this electrode can obtain a high specific capacitance of 697 F g−1 at a current density of 1 A g−1 and a stable cycling performance at a high current density of 5 A g−1. The strategy developed in this study provides a new approach for the design and fabrication of flexible supercapacitors by electrostatic spinning combined with hierarchical porous structures.

Synthesis of bimetal-decorated N-doped carbon nanoparticles for enhanced oxygen evolution reaction

Electrochemical hydrogen generation from the most plausible splitting water is severely hindered by OER (oxygen evolution reaction). Hence, the Fe4Co6@NDC amorphous sheet-like lamellar potential electrocatalyst prepared through simple solvothermal synthesis towards OER with low overpotential 307 mV @ 10 mA cm−2, Tafel slope of −55 mV dec-1 and turnover frequency of 0.0396 s−1, compared to 393 mV, Tafel slope of −81 mV dec-1, and a turnover frequency of 0.0136 s−1 at an IrO2 on an inert glassy carbon electrode, under the same conditions in 1 M KOH. The iron: cobalt adjacent ratio (4:6) could give a cooperative synergistic effect for OER, further nitrogen-doped carbon substrate (NDC) offers even metal anchoring sites has provided higher ECSA of 10.202 cm2 and also provides low resistive (5.6 Ω) material. Full cell water splitting Fe4Co6@NDC/NF (anode)//PtC/NF (cathode) with cell potential 1.58 V and the same setup will be used with perennial solar energy source only consumes 1.57 V enhanced hydrogen generation. We anticipate that the developed Fe4Co6@NDC electrocatalyst will be used as a formidable OER catalyst for a clean electrochemical energy conversion process.

Microviscosity-Assisted Disaggregation of a Model Ophthalmic Drug and FRET-Controlled Singlet Oxygen Generation in Lyotropic Liquid Crystals.

Different phases of lyotropic liquid crystals (LLCs), made up of mesogen-like sodium dodecyl sulfate (SDS), mainly bestow different bulk viscosities. Along with this, the role of microviscosities of the individual LLC phases is of immense interest because a minute change in it due to guest incorporation can cause significant alteration in their property as a potential energy transfer scaffold. Recently, LLCs have been identified as plausible drug delivery agents for ocular treatments. In this direction, the present work illustrates photophysical modulations of an important laser dye as well as an ophthalmic medicine, coumarin 6 (C6), inside different LLC phases in an aqueous medium. C6 molecules spontaneously accumulate in water, leading to aggregation-caused quenching (ACQ) of fluorescence. However, the different phases of the LLCs prepared from SDS and water helped in disintegrating the C6 colonies to various extents depending upon the microviscosity. The heterogeneity in the LLC phases, in turn, could modulate the Förster resonance energy transfer (FRET) between C6 and the LLC incorporated with N-doped carbon nanoparticles (N-CNPs). The N-CNPs act as potential photosensitizers and generate singlet oxygen (1O2), a reactive oxygen species (ROS), to different extents. Microviscosities of the prepared LLCs were calculated by using fluorescence correlation spectroscopy (FCS). The different phases of the LLCs, viz., lamellar and hexagonal, with different microviscosities controlled the extent of C6 disaggregation and hence the FRET and the ROS generation. The results are encouraging since ROS generation has a significant role in the vision mechanism and PDT-based applications. LLC-based drug administration with potential FRET to control ROS generation may become handy in ophthalmology. The LLC phases used in this experiment not only served the purpose of drug delivery but also the photophysical events therein are compatible with the ocular environment.

Cooperation between holey N-doped carbon and Ni nanoparticles as an efficient electrocatalyst for the hydrogen evolution reaction.

Exploring non-noble and high-performance metal catalysts to replace platinum-based catalysts for the hydrogen evolution reaction (HER) via electrochemical water splitting significantly alleviates environmental pollution and the energy crisis. However, the synthetic approaches of such electrocatalysts are generally complex and challenging for large-scale production. Herein, a facile and green solid-state synthesis of Ni nanoparticles decorated with N-doped porous carbon is presented. These materials are derived from chitosan as carbon, nitrogen sources, and nickel acetate as a nickel source with NaCl as a template. The synthesis procedure is simple to scale up without an organic solvent. Benefiting from its porous structure, splendid conductivity, and the synergistic effect of Ni nanoparticles and holey N-doped carbon, the as-prepared Ni@CN exhibits superior HER performance in 1 M KOH with a low potential of 121 mV at 10 mA cm-2. These findings indicate that the convenient and environmentally friendly synthesis approach provides a novel method for large-scale synthesis of HER electrocatalysts for industrial electrolytic water splitting applications.

Ru-doped MoO2/Mo2C coupled with N-doped carbon as an efficient pH-universal electrocatalyst for hydrogen generation

The preparation of stable, efficient and pH-universal hydrogen evolution reaction (HER) electrocatalysts is urgent and significant for large-scale hydrogen production. Herein, a simple and efficient method was developed to fabricate Ru-doped MoO2/Mo2C onto N-doped carbon nanoparticles (Ru-MoO2/Mo2C/NC). The formed smaller nanoparticles by Ru doping can provide abundant accessible active sites and interfaces. Moreover, the synergistic effects of Ru and Mo-based compounds also played a key role in promoting the catalytic kinetics. The as-prepared Ru-MoO2/Mo2C/NC exhibited low overpotentials of 38, 61, 67 and 75 mV in alkaline, neutral, acidic electrolyte solutions and alkaline seawater at 10 mA cm−2, respectively. This work proposes a valid method for the design of efficient electrocatalysts through precise component regulation.

N-doped carbon nanotube/particle composite as highly efficient electrocatalyst towards oxygen reduction reaction

Optimizing the microstructure is crucial to design the N-doped carbon-based electrocatalysts towards oxygen reduction reaction (ORR). Herein, a 1D/0D composited catalyst (L-Fe-CN-C) is prepared by using graphitic carbon nitride, iron chloride and carbon black as the raw materials. The resultant catalyst is consisted of N-doped carbon nanotubes and nanoparticles. The nanotubes are dramatically shrunk and smaller carbon nanoparticles are simultaneously generated with the pre-addition of carbon black, both contributing to the large specific surface area, high space utilization and to construct a mesopore-dominated microstructure. Moreover, the content of active pyridinic N is increased in the resultant catalyst. Benefiting from the modulation, the catalyst exhibits an excellent ORR activity with 0.850 V of half wave potential, 6.224 mA cm−2 of limited diffusion current density and high selectivity to 4e-path of ORR in 0.1 M KOH. The zinc-air battery with the catalyst on air electrode outputs a high peak power density, high specific capacity and excellent long-term durability, being comparable to those of the benchmark Pt/C based battery. This work provides a rational strategy to controllably synthesize an N-doped carbon ORR catalyst with hierarchical structure and preferable performance.

N-Doped Carbon Nanoparticles as Antibacterial Agents on Escherichia coli: The Role of the Size and Chemical Composition of Nanoparticles

In the last years N-doped carbon nanoparticles have been shown to have improved antibacterial activity over the undoped nanomaterial, but it is difficult to find correlations between the structure of the nanoparticle and its antibacterial activity. This prevents us from proposing a clear antibacterial mechanism and makes it difficult to select materials with the best physical and chemical properties for use as antibacterial agents. With this purpose, here, we analyze the effect of, the size and the surface chemical composition of four N-doped carbon nanoparticles on the growth of Escherichia coli bacteria, used in this work as a model of Gram-negative bacteria. Our results indicated great antibacterial activity as the concentration of the carbon nanoparticles increased. The IC50 values obtained ranged between 23 and 34 μg/mL, the lowest values found in the literature for CNPs in the absence of metals. The reduction rate was analyzed using a Ligand-Substrate model based on Monod’s equation, which allows us to interpret the dependence of the nanoparticle-bacteria affinity with the nanomaterial structure. The results of the model indicate the contribution of two mechanisms, oxidative stress and the nanoknife in the antibacterial process on Escherichia coli bacteria.

A multisite strategy to improve room-temperature DMMP sensing performances on reduced graphene oxide modulated by N-doped carbon nanoparticles and copper ions

Development of room-temperature gas sensors with excellent sensing performances for detection of dimethyl methylphosphonate (DMMP, a simulant of organophosphate) has aroused considerable attention. However, the weak adsorption ability of sensing materials toward DMMP molecules causes poor sensing performances. In this work, a multisite strategy for enhancing sensitivity was proposed by introduction of both N-doped carbon nanoparticles (N-CNPs) and copper ions onto the surface of rGO (designated as GNC). Impressively, optimal GNC-3 exhibits the response value of 10.2% toward 100 ppm DMMP, which is 5.3 times higher than that of pristine rGO. This mechanism for multisite-assisted enhanced DMMP sensing performances was investigated by combined characterizations of Fourier-transform infrared spectra, UV-Vis spectra, photoluminescence spectra and Mott-Schottky curves. Besides the construction of multisite, improvement of hydrogen bonding interactions between DMMP molecules and N-CNPs in hybrids assisted by copper ions, and decrease of conduction band potential by formation of ternary hybrids also contribute to enhance the sensitivity of DMMP sensors. These findings not only provided new insights into designing high-performance room-temperature gas sensors, but also promoted the fundamental research on sensing mechanism for room-temperature gas sensors.

Bimetallic FeMn-N nanoparticles as nanocatalyst with dual enzyme-mimic activities for simultaneous colorimetric detection and degradation of hydroquinone

The transition element based N-doped carbon nanoparticles (NPs) with high catalytic activity and more active centers are regards as nanozymes with great potential for colorimetric detection and environmental degradation. Here, three-dimensional (3D) hierarchically porous of manganese-amplified Fe-N-doped carbon (Fe/Mn-N-C) catalysts with more Fe/Mn-N4 and C-N active groups was synthesized via pyrolysis of manganese(II) acetyllacetonate/ferrocene@ZIF-8 nanocomposites. Owing to its excellent peroxidase-like (POD-like) and superoxide (SOD) mimicking properties, the Fe/Mn-N-C nanozymes were selected to rapid and accurate colorimetric detection of hydroquinone (HQ), and the detection limit was determined as 0.21 μM in range of 0–100 μM. In addition, the rapid degradation of HQ via hydroxyl radical (•OH) and superoxide anion (O2•-) generated between Fe/Mn-N-C nanozymes and H2O2, and the degradation efficiency reached to over 92% under the optimum reaction conditions (pH 4.0, 100 mM H2O2). The reaction mechanisms were systematically explored. The manganese-amplified Fe-N-C single atom nanozyme with excellent enzyme-like activity and chemical stability will propose a feasible way for accurate detection and removal of pollutants in actual production.

Preparation of amorphous Ni/Co bimetallic nanoparticles to enhance the electrochemical sensing of glucose

Based on the incidence of diabetes, developing glucose sensors of superior performance with low-cost transition metals (TMs) has been the direction of many researchers, amorphous TMs with highly efficient electrocatalytic properties have attracted our interest. On this basis, amorphous nickel–cobalt bimetallic N-doped carbon nanoparticles on carbon cloth (a-Ni2/Co1-NC/CC) were fabricated from ZIF-8, which was then used to fabricate an enzyme-free glucose sensor. It was found that the a-Ni2/Co1-NC/CC had the best response to glucose in 0.4 M NaOH at 0.55 V (vs Hg/HgO). As compared to crystal Ni2/Co1 nanoparticle on carbon cloth (c-Ni2/Co1 NPs/CC), cyclic voltammetry (CV) and chronoamperometry studies revealed that the a-Ni2/Co1-NC/CC showed a significant increase in the efficient of electrochemical oxidation of glucose under optimal conditions, exhibiting a high sensitivity of 2.455 mA mM−1 cm−2 with a low detection limit of 0.15 μM (S/N = 3). Furthermore, the constructed sensor based on a-Ni2/Co1-NC/CC also has long-term stability and can be used to detect glucose accurately in beverages (pure milk, coffee drinks, tea drinks, and soda water) with reasonable recovery from 95.6 % to 105.6 %. This study provides a simple and feasible method for the construction of a highly sensitive non-enzyme glucose electrochemical sensor based on amorphous TMs.

Fe-embedded ZIF-derived N-doped carbon nanoparticles for enhanced selective reduction of p-nitrophenol

The selective catalytic reduction of nitroaromatics towards aromatic amines under mild reaction condition is an important approach to reduce the toxicity of waste effluents from industry and afterwards utilize the product as important fine organic chemical raw materials. P-nitrophenol (PNP) is chosen as the probe molecule of nitroaromatics in this study. A Fe-embedded N-doped Carbon (Fe-N-C) catalyst prepared using ZIF-8 has been identified as a highly active, selective and stable catalyst in the selective catalytic reduction of PNP. The Fe-N-C catalyst is for the first time applied in PNP reduction and found to present 100% conversion and 100% product selectivity. A mechanism investigation has been carried out to conclude that in the PNP reduction on Fe-N-C, water acts as the main hydrogen provider and sodium borohydride is the electron donator. Furthermore, the Fe-N-C catalyst works well when it is applied in PNP degradation in real water samples, which further indicates its applicability in industrial wastewater treatment. This work offers a simple and useful strategy to design robust catalysts for the selective catalytic reduction of nitroaromatics.

Controllable synthesis of N-doped carbon nanoparticles with proper electrical conductivity for excellent microwave absorption performance

Controllable synthesis of N-doped carbon nanoparticles with proper electrical conductivity for excellent microwave absorption performance

N-doped carbon nanomaterials as fluorescent pH and metal ion sensors for imaging

Herein we describe the facile synthesis of new N-doped carbon nanoparticles (CNPs) obtained from 1,10-phenanthroline by the solvothermal method. Characterization of CNPs were carried out with transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectra (FTIR), UV–vis absorption spectra, and luminescence spectra. CNPs were pH sensitive and exploited as fluorescent chemosensors and imaging agents for Al(III) and Zn(II) ions in real-life samples. Remarkably, we show that CNPs can be used for the detection of Al(III) and Zn(II) ions in water samples. Accordingly, the results indicate that CNPs are highly effective in detecting Zn(II) content of cosmetic creams. We also demonstrated that the CNPs could be used for in vitro imaging of Al(III) and Zn(II) in Human Larynx Squamous Cell Carcinoma (Hep-2). Finally, Al(III) imaging in Angelica Officinalis root tissue was also achieved successfully. The CNPs are promising as luminescent multianalyte (pH, Al(III) and Zn(II)) sensors.

Potato-derived N-doped carbon nanoparticles incorporated with FeCo species as efficiently bifunctional electrocatalyst towards oxygen reduction and oxygen evolution reactions for rechargeable zinc-air batteries

An N-doped carbon-based bifunctional catalyst (Po-FeCo-N-C) is prepared. Biomass potato is utilized a sustainable material and the OER performance of the catalyst is positively regulated. Potato is carbonized to N-doped carbon nanoparticles with the facilitation of carbon black to anchor more nitrogen, generating pyridinic N and graphitic N dominated ORR active sites. The Po-FeCo-N-C with 3:1 of Fe/Co ratio exhibits 0.830 V of ORR half wave potential and 5.19 mA cm−2 of current density in 0.1 M KOH. Meanwhile, 85 mV of improvement on OER potential is achieved with regulation of Co(OH)2, demonstrating the remarkably bifunctional catalytic activity. The rechargeable zinc-air battery of Po-FeCo-N-C outputs higher open circuit voltage, and delivers higher specific capacities, larger power densities and excellent cyclic durability. This work provides a feasible method for the preparation of nonprecious metal-based bifunctional catalyst to ORR and OER from sustainable biomass material with low cost and wide resources.

N-Doped carbon nanoparticles on highly porous carbon nanofiber electrodes for sodium ion batteries.

Nitrogen doped carbon nanoparticles on highly porous carbon nanofiber electrodes were successfully synthesized via combining centrifugal spinning, chemical polymerization of pyrrole and a two-step heat treatment. Nanoparticle-on-nanofiber morphology with highly porous carbon nanotube like channels were observed from SEM and TEM images. Nitrogen doped carbon nanoparticles on highly porous carbon nanofiber (N-PCNF) electrodes exhibited excellent cycling and C-rate performance with a high reversible capacity of around 280 mA h g-1 in sodium ion batteries. Moreover, at 1000 mA g-1, a high reversible capacity of 172 mA h g-1 was observed after 300 cycles. The superior electrochemical properties were attributed to a highly porous structure with enlarged d-spacings, enriched defects and active sites due to nitrogen doping. The electrochemical results prove that N-PCNF electrodes are promising electrode materials for high performance sodium ion batteries.

Composite Cathodes Based on Lithium-Iron Phosphate and N-Doped Carbon Materials

The effect of different nitrogen-doped carbon additives (carbon coating from polyaniline, N-doped carbon nanotubes, and N-doped carbon nanoparticles) on electrochemical performance of nanocomposites based on the olivine-type LiFePO4 was investigated. Prepared materials were characterized by XRD, SEM, TGA-MS, CHNS-analysis, IR-, Raman, and impedance spectroscopies. Polyaniline deposition on the LiFePO4 precursor with following annealing lead to the formation of a LiFePO4/C nanocomposite with a carbon coating doped with nitrogen. Due to nitrogen atoms presence in carbon coating, the LiFePO4/N-doped carbon nanocomposites showed enhanced conductivity and C-rate capability. The discharge capacities of the synthesized materials in LIBs were close to the theoretical value at 0.1 C and retained high values with increasing current density. At high C-rates, the best results were obtained for a more dispersed LiFePO4/C composite with carbon coating prepared from polyaniline previously in situ deposited on LiFePO4 precursor particles. Its discharge capacity reached 96, 84, 73, and 47 mAh g−1 at 5, 10, 20, and 60 C-rates, respectively.

Fabrication of a Heterojunction by Coupling a Metal-Organic Framework and N-Doped Carbon for the Photocatalytic Removal of Antibiotic Drugs with High Efficiency.

Norfloxacin (NOR) and tetracycline (TC), two widely used antibiotic drugs released to the aquatic environment, induce harm to ecosystems. In this study, an effective method was developed successfully to remove NOR and TC by photocatalysis with a novel heterojunction NC/NH2-MIL-53(Fe), which was fabricated by combining a metal-organic framework (MOF) material (NH2-MIL-53(Fe)) and N-doped carbon (NC) nanoparticles via a facile solvent thermal method. The prepared product exhibits outstanding photocatalytic efficiencies toward degradation of NOR and TC that are 15 and 6 times higher than those of pure NH2-MIL-53(Fe), respectively. Moreover, it is higher than those of the related materials reported previously. The greatly enhanced photocatalytic performance is assigned to the fabricated heterojunction with well-matched energy band gaps, where the NC acts as an efficient electron transfer/reservoir material to effectively promote the migration and transfer and restrain the recombination of charge carriers. In addition, the formed heterojunction increases specific surface area and light absorbance. The photocatalytic activity enhanced mechanism, degradation products, and pathway were investigated. The present study offers a novel strategy to significantly improve the photocatalytic performances of MOFs for highly efficient photocatalytic removal of antibiotic drugs in wastewater.

Phase-Controlled Synthesis of Nickel-Iron Nitride Nanocrystals Armored with Amorphous N-Doped Carbon Nanoparticles Nanocubes for Enhanced Overall Water Splitting.

Transition metal nitrides (TMNs) nanostructures possess distinctive electronic, optical, and catalytic properties, showing great promise to apply in clean energy, optoelectronics, and catalysis fields. Nonetheless, phase-regulation of NiFe-bimetallic nitrides nanocrystals or nanohybrid architectures confronts challenges and their electrocatalytic overall water splitting (OWS) performances are underexplored. Herein, novel pure-phase Ni2+ x Fe2- x N nanocrystals armored with amorphous N-doped carbon (NC) nanoparticles nanocubes (NPNCs) are obtained by controllable nitridation of NiFe-Prussian-blue analogues derived oxides/NC NPNCs under Ar/NH3 atmosphere. Such Ni2+ x Fe2- x N/NC NPNCs possess mesoporous structures and show enhanced electrocatalytic activity in 1m KOH electrolyte with the overpotential of 101 and 270mV to attain 10 and 50mAcm-2 current toward hydrogen and oxygen evolution reactions, outperforming their counterparts (mixed-phase NiFe2 O4 /Ni3 FeN/NC and NiFe oxides/NC NPNCs). Remarkably, utilizing them as bifunctional catalysts, the assembled Ni2+ x Fe2- x N/NC||Ni2+ x Fe2- x N/NC electrolyzer only needs 1.51V cell voltage for driving OWS to approach 10mAcm-2 water-splitting current, exceeding their counterparts and the-state-of-art reported bifunctional catalysts-based devices, and Pt/C||IrO2 couples. Additionally, the Ni2+ x Fe2- x N/NC||Ni2+ x Fe2- x N/NC manifests excellent durability for OWS. The findings presented here may spur the development of advanced TMNs nanostructures by combining phase, structure engineering, and hybridization strategies and stimulate their applications toward OWS or other clean energy fields.

Cd2+ ion adsorption and re-use of spent adsorbent with N-doped carbon nanoparticles coated on cerium oxide nanorods nanocomposite for fingerprint detection

This work provides a novel approach to prepare nitrogen-doped carbon nanoparticles (CNPs) coated on a cerium oxide nanorods nanocomposite (N-CNPs/CeO2NRsnC) for the uptake of cadmium (Cd2+) ions and re-using the spent adsorbent, Cd2+-CNPs/CeO2NRsnC for latent fingerprint detection (LFP). N-CNPs were prepared by a thermal method with urea and cabbage powder as precursors. N-CNPs/CeO2NRsnC was developed with N-CNPs and CeO2NRs with a hydrothermal method and characterized by various instrument methods like UV-visible, FT-IR, XRD, BET, XPS, SEM, and TEM. The N-CNPs/CeO2NRsnC had a greater surface area (9.96 m2/g) than N-CNPs (0.64 m2/g). The synthesized N-CNPs/CeO2NRsnC proved to be a good sorbent material to remove Cd2+ from water at a maximum pH 8 and dosage 10 mg/L. The adsorption was spontaneous and endothermic at 25 ºC. In addition, Cd2+-N-CNPs/CeO2NRsnC has been shown to be sensitive and selective for LFP identification on several porous substrates. It is therefore a good labeling agent for latent fingerprint identification in forensic science.

Nanoengineering of N-doped Mesoporous Carbon Nanoparticles with Adjustable Internal Cavities via Emulsion-Induced Assembly.

The preparation of mesoporous carbonaceous materials with particularly adjustable morphology is currently a hot area of research in mesoporous materials. Herein, a novel approach is reported for the construction of N-doped multicavity mesoporous carbon nanoparticles (NMMCNs) based on the “emulsion swelling–acid curing mechanism” using a nanoemulsion assembly method under a high-speed shearing force. Intriguingly, this approach adopted a novel acid (HCl) curing procedure. Impressively, the morphology evolution from an internal multicavity to a single cavity and then to a non-cavity interior structure could be accomplished by simply varying the synthesis parameters. Additionally, this synthesis approach ingeniously overcame the following problems: (i) technically, the employment of high temperatures and high pressures in traditional hydrothermal reaction curing environments is avoided; (ii) this approach removes the requirement for silicon coating, which provides a limited pyrolysis condition, to obtain a multi-chamber structure. Resveratrol (Res) is an insoluble natural medicine and was successfully loaded into NMMCNs, thereby the Res–NMMCNs delivery system was constructed. Importantly, the Res–NMMCNs delivery system could still retain the antitumor and antioxidant activity of Res in vitro.