Nitrogen-doped Holey Graphene Research Articles

Computational assessment of the use of graphene-based nanosheets as PtII chemotherapeutics delivery systems.

Graphene is the newest form of elemental carbon and it is becoming rapidly a potential candidate in the framework of nano-bio research. Many reports confirm the successful use of graphene-based materials as carriers of anticancer drugs having relatively high loading capacities compared with other nanocarriers. Here, the outcomes of a systematic study of the adsorption behavior of FDA approved PtII drugs cisplatin, oxaliplatin, and carboplatin on surface models of pristine, holey, and nitrogen-doped holey graphene are reported. DFT investigations in water solvent have been carried out considering several initial orientations of the drugs with respect to the surfaces. Adsorption free energies, calculated including basis set superposition error (BSSE) corrections, result to be significantly negative for many of the drug@carrier adducts indicating that tested layers could be used as potential carriers for the delivery of anticancer PtII drugs. The reduced density gradient (RDG) analysis allows to show that many kinds of non-covalent interactions, including canonical H-bond, are responsible for the stabilization of the formed adducts.

Single Metal Atoms Anchored on N‐Doped Holey Graphene as Efficient Dual‐Active‐Component Catalysts for Nitroarene Reduction

AbstractDeveloping efficient catalysts for facilitating organic synthesis processes is a popular but challenging topic in modern chemical industries. A combination of active metals and an active support structure is, in theory, an effective strategy for boosting catalytic activity but such combinations have been rarely explored. Herein, a strategy for fabricating highly efficient dual‐active‐component catalysts (DACCs) is presented by anchoring single‐atom metals (M1; e.g., Pd1, Ni1, Co1, and Zn1) or double‐atomic metals (e.g., Pd1‐Co1, Pd1‐Ru1, and Pd1‐Ni1) on nitrogen‐doped holey graphene (NHG). Among the resultant DACCs, Pd1/NHG, which combines atomically dispersed metal species and an active NHG carbocatalyst, has been shown to display enhanced catalytic performance toward nitroarene reduction . In particular, its catalytic efficiency in reducing 4‐nitrophenol corresponds to a turnover frequency of 2.0 min−1, which is 97 times higher than the benchmark set by commercial Pd/C catalysts (5.0 wt.%), and vastly superior to those of its counterparts (e.g., NHG carbocatalyst and NHG supported Pd clusters. Notably, four intermediates and two active components (i.e., NHG and single‐atom Pd) in the nitroarene reduction process have been identified. This study presents an effective and versatile synthetic strategy to prepare DACCs through the combination of metallic catalysts and a carbocatalyst substrate.

Probing the Activity Enhancement of Carbocatalyst with the Anchoring of Atomic Metal.

Enhanced catalysis for organic transformation is essential for the synthesis of high-value compounds. Atomic metal species recently emerged as highly effective catalysts for organic reactions with high activity and metal utilization. However, developing efficient atomic catalysts is always an attractive and challenging topic in the modern chemical industry. In this work, we report the preparation and activity enhancement of nitrogen- and sulfur-codoped holey graphene (NSHG) with the anchoring of atomic metal Pd. When employed as the catalyst for nitroarenes reduction reactions, the resultant Pd/NSHG composite exhibits remarkably high catalytic activity due to the co-existence of dual-active components (i.e., catalytically active NSHG support and homogeneous dispersion of atomic metal Pd). In the catalytic 4-nitrophenol (4-NP) reduction reaction, the efficiency (turnover frequency) is 3.99 × 10-2 mmol 4-NP/(mg cat.·min), which is better than that of metal-free nitrogen-doped holey graphene (NHG) (2.3 × 10-3 mmol 4-NP/(mg cat.·min)) and NSHG carbocatalyst (3.8 × 10-3 mmol 4-NP/(mg cat.·min)), the conventional Pd/C and other reported metal-based catalysts. This work provides a rational design strategy for the atomic metal catalysts loaded on active doped graphene support. The resultant Pd/NSHG dual-active component catalyst (DACC) is also anticipated to bring great application potentials for a broad range of organic fields, such as organic synthesis, environment treatment, energy storage and conversion.

Pt Nanoparticles Supported on Iron and Nitrogen-Doped Holey Graphene for Boosting ORR Performance

Developing low-platinum catalysts is considered a promising strategy to facilitate the commercialization of fuel cells. However, the electrochemical performance of such materials is often hindered by mass-transfer issues. In this study, platinum nanoparticles supported on iron and nitrogen-doped holey graphene (Pt/Fe, N-HG) were synthesized by a simple method and used as an oxygen reduction reaction (ORR) catalyst. The unique holey structure and the co-doping of Fe and N atoms are proved beneficial for not only the formation of Pt nanoparticles but also enhancing the electrochemical performance of the catalyst. Density functional theory calculations indicate that the co-doping of Fe and N atoms increases the ability to adsorb Pt, as well as enhances the Pt adsorption of O2 and oxygen-containing intermediates in the ORR. This study presents a novel approach for the controllable synthesis of multidoped holey graphene-based electrocatalysts, with optimized surface holey structures and electrochemical performances. These findings offer significant insights into the development of efficient catalysts for fuel cell applications.

Study on the Application of Nitrogen-Doped Holey Graphene in Supercapacitors with Organic Electrolyte.

We present a facile low-cost method to produce nitrogen-doped holey graphene (N-HGE) and its application to supercapacitors. A composite of N-HGE and activated carbon (AC) was used as the electrode active material in organic-electrolyte supercapacitors, and the performances were evaluated. Melamine was mixed into graphite oxide (GO) as the N source, and an ultra-rapid heating method was used to create numerous holes during the reduction process of GO. X-ray photoelectron spectra confirmed the successful doping with 2.9-4.5 at.% of nitrogen on all samples. Scanning electron micrographs and Raman spectra revealed that a higher heating rate resulted in more holes and defects on the reduced graphene sheets. An extra annealing step at 1000 °C for 1 h was carried out to further eliminate residual oxygen functional groups, which are undesirable in the organic electrolyte system. Compared to the low-heating-rate counterpart (N-GE-15), N-HGE boosted the specific capacity of the supercapacitor by 42 and 22% at current densities of 0.5 and 20 A/g, respectively. The effects of annealing time (0.5, 1, and 2 h) at 1000 °C were also studied. Longer annealing time resulted in higher capacitance values at all current densities due to the minimized oxygen content. Volumetric specific capacitances of 49 and 24 F/cm3 were achieved at current densities of 0.5 and 20 A/g, respectively. For the high-power-density operation at 31,000 W/kg (or 10,000 W/L), an energy density as high as 11 Wh/kg (or 3.5 Wh/L) was achieved. The results indicated that N-HGE not only improved the conductivity of the composite supercapacitors but also accelerated ion transport by way of shortened diffusion paths through the numerous holes all over the graphene sheets.

Label-free electrochemical immunosensor for highly sensitive COVID-19 spike protein detection

The ongoing coronavirus pandemic responsible for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly increased the rate of global death and infections due to variant mutations (such as Delta and Omicron). While specifically developed and approved vaccines can limit the spread of disease in a population and severity of resulting symptoms, none have been demonstrated to effectively prevent infection altogether. Thus, reliable early diagnosis of COVID-19 is critical to identify positive cases to help contain the outbreak. Herein we report a label-free electrochemical immunosensor for rapid diagnosis of COVID-19 by using nitrogen-doped holey graphene (N-HRGO) as a nanocarrier decorated with thionine (TH) molecules as electrochemical indicators. With the spike protein located on the surface of the COVID-19 particles as the model target, the as-prepared electrochemical immunosensor could detect the presence of the COVID-19 spike protein over a wide linear range (1 pg mL−1−10 ng mL−1) with a low detection limit (0.3 pg mL−1). In addition, the developed electrochemical immunosensor exhibited an excellent selectivity (with insignificant current changes towards interfering proteins comparing with COVID-19 spike protein), a good reproducibility and long-term storage stability. Importantly, the electrochemical immunosensor thus developed could successfully and reliably detect the spike protein of COVID-19 in saliva and human serum complex samples. Thus, the as-prepared label-free electrochemical immunosensor can achieve rapid and sensitive detection of the COVID-19 spike protein, as a promising clinical diagnosis tool in monitoring the progression of COVID-19.

Nitrogen-doped holey graphene additive for high-performance electric double-layer supercapacitors

A facile and cost-effective method is developed to produce nitrogen (N)-doped holey graphene nanosheets (NHGNSs) using rapid heating under an NO atmosphere. This is a single-step and residual-free process wherein the holey structure and N doping are simultaneously created. In this study, we employ three kinds of additives, namely graphene (GNSs), holey graphene (HGNSs), and NHGNSs, in activated carbon (AC) electrodes. The conventional GNS additive though improves electronic conductivity of the AC electrode greatly hinders the ionic conductivity, decreasing supercapacitive performance in propylene carbonate electrolyte. HGNSs with large accessible surface area and efficient ion transport pathways outperform the GNS electrode additive. The NHGNSs, owing to the dual benefits of the holey structure and high electronic conductivity, is the best additive for the AC electrode. The NHGNSs improve electrode wettability toward electrolyte, enhance ion diffusion, and reduce interfacial contact resistance, thereby promoting rate capability of the AC cell. In addition, the effects of electrode additives on reliability of AC cells are investigated for the first time. The NHGNSs effectively suppress the leakage current and electrode gassing under operation. An effective strategy to improve charge-discharge performance, cyclability, and reliability of electric double-layer supercapacitors is proposed.

A Sandwich-Type Electrochemical Immunosensor for Insulin Detection Based on Au-Adhered Cu5 Zn8 Hollow Porous Carbon Nanocubes and AuNP Deposited Nitrogen-Doped Holey Graphene.

Rapid, accurate, and sensitive insulin detection is crucial for managing and treating diabetes. A simple sandwich-type electrochemical immunosensor is engineered using gold nanoparticle (AuNP)-adhered metal-organic framework-derived copper-zinc hollow porous carbon nanocubes (Au@Cu5 Zn8 /HPCNC) and AuNP-deposited nitrogen-doped holey graphene (NHG) are used as a dual functional label and sensing platform. The results show that identical morphology and size of Au@Cu5 Zn8 /HPCNC enhance the electrocatalytic active sites, conductivity, and surface area to immobilize the detection antibodies (Ab2 ). In addition, AuNP/NHG has the requisite biocompatibility and electrical conductivity, which facilitates electron transport and increases the surface area of the capture antibody (Ab1 ). Significantly, Cu5 Zn8 /HPCNC exhibits necessary catalytic activity and sensitivity for the electrochemical reduction of H2 O2 using (i-t) amperometry and improves the electrochemical response in differential pulse voltammetry. Under optimal conditions, the immunosensor for insulin demonstrates a wide linear range with a low detection limit and viable specificity, stability, and reproducibility. The platform's practicality is evaluated by detecting insulin in human serum samples. All these characteristics indicate that the Cu5 Zn8 /HPCNC-based biosensing strategy may be used for the point-of-care assay of diverse biomarkers.

Hierarchical nitrogen-doped holey graphene as sensitive electrochemical sensor for methyl parathion detection

Nitrogen-doped HG featuring a hierarchical macro- and nanoporous 3-D architecture with high pyrrolic-N content is a promising candidate for the construction of sensitive graphene-based electrochemical sensors for environmental and bioanalytical applications. • N-doped HG featuring a hierarchical macro- and nanoporous 3-D architecture for determination of MP was fabricated. • Pyrrolic-N in N-HG played a key role in enhanced electrocatalysis. • First principle calculations indicated that pyrrolic-N exhibited the strongest MP adsorption. • N-HG with a high pyrrolic-N content exhibited excellent sensing performance. • Ultra-low detection and excellent recovery in case of real samples were achieved. The determination of organophosphorus pesticide (OPS) residues is of great importance in reducing environmental pollution and ensuring food safety. A high-performance nitrogen-doped holey graphene (N-HG) electrochemical sensor for determination of methyl parathion (MP; one of the most commonly used OPS) based on a hierarchical macro- and nanoporous 3-D architecture has been successfully developed. The influence of various N-configurations on electron transfer kinetics and the sensing performance of the N-HG modified electrode was investigated systematically through combined practical and theoretical studies. Three N-bonding configurations were investigated in N-HG, namely, pyridinic N, pyrrolic N, and graphitic N. It was found that N-HG with a high pyrrolic-N content exhibited the largest electron transfer rate and the best sensing performance (ultralow detection limits: 3.5 pg·ml −1 ; wide linear range: 1 ng ml −1 –150 μg·ml −1 ), indicating that pyrrolic-N in the N-HG played a critical role in the electrochemical process and in enhanced electrocatalysis, as confirmed by first-principle calculations. Furthermore, the N-HG based sensor exhibited excellent selectivity and freedom from interference, good accuracy and satisfactory recoveries for real samples, confirming N-HG based electrochemical sensors have great scope for applications in environmental analysis and bio-sensing.

Nitrogen-doped holey graphene nanoscrolls for high-energy and high-power supercapacitors

Porous structure and heteroatom doping are two key parameters for significantly boosting the capacitive performance of graphene-based materials. Herein, we report a facile approach to prepare one-dimensional (1D) nitrogen-doped holey graphene nanoscrolls (NHGNSs) through cold quenching treatment of two-dimensional graphene oxide sheets, followed by thermal annealing in the successive atmosphere of NH3 and air. Benefiting from the synergy of the unique 1D tubular morphology, abundant nanoholes and nitrogen doping, the NHGNSs exhibit a high specific capacitance of 126 F/g at 1 A/g in ionic liquid electrolyte and excellent rate capability with 81% of the capacitance retained at 20 A/g. Furthermore, the fabricated symmetric supercapacitors based on NHGNSs achieve both high energy density of 53.5 Wh/kg at 875 W/kg and high power density of 17.5 kW/kg at 43.4 Wh/kg. The simple synthetic process and superior electrochemical performance suggest the great potential of NHGNSs for supercapacitor application.

N-Doping Holey Graphene TiO2–Pt Composite as Efficient Electrocatalyst for Methanol Oxidation

The nitrogen-doped holey graphene oxide/TiO2 (TiO2–NHGO) composite is synthesized as catalyst support for the Pt catalyst. The resulting catalyst, Pt–TiO2–rNHGO, shows higher activity and stability...

Three-dimensional nitrogen-doped holey graphene and transition metal oxide composites for sodium-ion batteries

The unique macroporous architecture in combination with the presence of nanopores in graphene sheets facilitate ion transport during charge/discharge.

Sunlight-assisted oxidative degradation of cefixime antibiotic from aqueous medium using TiO2/nitrogen doped holey graphene nanocomposite as a high performance photocatalyst

Innovative, nanotechnology-based remedies for the wastewater treatment processes are gaining momentum in recent years. Of particular interest is the containment of the environmental threat due to the contamination of water bodies by antibiotics, which can eventually lead to the proliferation of antibiotic resistant bacteria, causing grave concern to humanity. Herein we report a straightforward and simple method for the sunlight-assisted oxidative degradation of the antibiotic cefixime using a nanocomposite of TiO2 and nitrogen-doped holey graphene (TiO2/NHG) as a highly effective photocatalyst. Of the various catalysts tested TiO2/NHG is found to be superior towards the oxidative degradation of cefixime. The effect of various reaction parameters and presence of H2O2 are studied. The present methodology offers good scale-up possibilities.

Substrate-Induced Synthesis of Nitrogen-Doped Holey Graphene Nanocapsules for Advanced Metal-Free Bifunctional Electrocatalysts

The development of efficient metal-free electrocatalysts for oxygen electrocatalysis is of great significance for various energy conversion devices. Herein, novel nitrogen-doped holey graphene nanocapsules (NHGNs) are reported prepared by self-assembly of graphene oxide nanosheets on the surface of amino-functionalized silica template and NH3 activation with simultaneously enhanced nitrogen doping and etching of nanopores in graphene, followed by template etching. The silica template is demonstrated to show a substrate-enhanced effect on nitrogen doping and etching of nanopores in graphene based on density functional theory calculations. Benefiting from the large surface area, unique pore distribution, and high surface functionality of nitrogen doping, the resulting NHGNs exhibit superior bifunctional electrocatalytic activity and durability for both oxygen reduction reaction and oxygen evolution reaction, which is similar to that of the commercial Pt/C and RuO2 electrocatalysts, respectively. This work presents an advance in developing new nitrogen-doped graphene species for highly efficient metal-free electrocatalysis.

Facile synthesis of porous nitrogen-doped holey graphene as an efficient metal-free catalyst for the oxygen reduction reaction

Nitrogen-doped graphene is a promising candidate for the replacement of noble metal-based electrocatalysts for oxygen reduction reactions (ORRs). The addition of pores and holes into nitrogen-doped graphene enhances the ORR activity by introducing abundant exposed edges, accelerating mass transfer, and impeding aggregation of the graphene sheets. Herein, we present a straightforward but effective strategy for generating porous holey nitrogen-doped graphene (PHNG) via the pyrolysis of urea and magnesium acetate tetrahydrate. Due to the combined effects of the in situ generated gases and MgO nanoparticles, the synthesized PHNGs featured not only numerous out-of-plane pores among the crumpled graphene sheets, but also interpenetrated nanoscale (5–15 nm) holes in the assembled graphene. Moreover, the nitrogen doping configurations of PHNG were optimized by post-thermal treatments at different temperatures. It was found that the overall content of pyridinic and quaternary nitrogen positively correlates with the ORR activity; in particular, pyridinic nitrogen generates the most desirable characteristics for the ORR. This work reveals new routes for the synthesis of PHNG-based materials and elucidates the contributions of various nitrogen species to ORRs.

Nitrogen-Doped Holey Graphene Film-Based Ultrafast Electrochemical Capacitors.

The commercialized aluminum electrolytic capacitors (AECs) currently used for alternating current (AC) line-filtering are usually the largest components in the electronic circuits because of their low specific capacitances and bulky sizes. Herein, nitrogen-doped holey graphene (NHG) films were prepared by thermal annealing the composite films of polyvinylpyrrolidone (PVP), graphene oxide (GO), and ferric oxide (Fe2O3) nanorods followed by chemical etching with hydrochloride acid. The typical electrochemical capacitor with NHG electrodes exhibited high areal and volumetric specific capacitances of 478 μF cm(-2) and 1.2 F cm(-3) at 120 Hz, ultrafast frequency response with a phase angle of -81.2° and a resistor-capacitor time constant of 203 μs at 120 Hz, as well as excellent cycling stability. Thus, it is promising to replace conventional AEC for AC line-filtering in miniaturized electronics.

Nitrogen-Doped Holey Graphene for High-Performance Rechargeable Li–O2 Batteries

Li–air batteries represent cutting edge electrochemical energy storage devices, but their practical applications have been precluded by the high cathode cost, the low discharge/charge efficiency, and/or the short battery lifetime. Here, we developed a low-cost, but very efficient, air electrode from porous nitrogen-doped holey graphene for rechargeable nonaqueous Li–O2 cells. The resultant Li–O2 cell can deliver a high round-trip efficiency (85%) and a long cycling life (>100 cycles) under controlled discharge/charge depths or a high capacity of 17 000 mAh/g under the full discharge/charge condition, superior to most other carbonaceous air cathodes. The observed superb performance for the air electrode based on the nitrogen-doped holey graphene can be attributed to its efficient metal-free catalytic activity and three-dimensional mass transport pathway. Therefore, this work represents a new approach to low-cost, efficient, metal-free, binder-free, and hierarchically porous air electrodes useful for energy...

Nitrogen-Doped Holey Graphene as an Anode for Lithium-Ion Batteries with High Volumetric Energy Density and Long Cycle Life.

Nitrogen-doped holey graphene (N-hG) as an anode material for lithium-ion batteries has delivered a maximum volumetric capacity of 384 mAh cm(-3) with an excellent long-term cycling life up to 6000 cycles, and as an electrochemical capacitor has delivered a maximum volumetric energy density of 171.2 Wh L(-1) and a volumetric capacitance of 201.6 F cm(-3) .

Nitrogen-doped holey graphene foams for high-performance lithium storage

We demonstrate a facile and scalable approach toward nitrogen-doped holey graphene foams (NHGFs) via simultaneous etching and assembling of graphene oxide and subsequent annealing treatments.

Fabrication of nitrogen-doped holey graphene hollow microspheres and their use as an active electrode material for lithium ion batteries.

Nitrogen-doped holey graphene hollow microspheres (NHGHSs), synthesized through a template sacrificing method, were utilized as an anode material for lithium ion batteries (LIBs). Because of their specific microspherical hollow structure comprising nitrogen-doped holey graphene (NHG), the NHGHSs can exhibit reversible capacities of ∼ 1563 mAh g(-1) at a low rate of 0.5 C and ∼ 254 mAh g(-1) at a high rate of 20 C, which are significantly higher than the discharge capacity of the pristine graphene and other graphene-based carbonaceous materials. These, along with their good cycling stability, clearly demonstrate the great potential of using the NHGHSs as the anode material for LIBs of both high energy and power densities. We believe that the high specific surface area, holey structure of nitrogen-doped graphene, specific microspherical hollow structure, and increased interlayer spacing between the NHG nanosheets in their hollow walls are the main origins of their high electrochemical performance.