Nitrogen-dopedgraphene (N-rGO) was successfully synthesized during the reduction of graphene oxide by the modified Hummers’ method. In contrast to the reduced graphene oxide (rGO), N-rGO presented superior morphology, structure and composition as the anode of lithium-ion batteries (LIBs) according to the examination of SEM, TEM, XRD, Raman spectrum and XPS. The doping content of nitrogen in N-rGO was about 7.98 at.%. The electrochemical performances of N-rGO as anodes of LIBs were also evaluated accordingly. Thus-prepared N-rGO showed a higher reversible specific capacity of 332 mAh g -1 during 600 cycles at 500 mAg -1 . Even at 4 Ag -1 , a reversible capacity of 208 mAhg -1
There are certain defects in the graphene prepared by redox method. These defects can cause a decrease in the electrochemical performance of the resulting grapheme. The performance of chemically prepared graphene can be improved to some extent by the doping of heteroatoms. In this paper, the electrochemical performance of graphene-based composites is improved by doping with nitrogen. The results show that the electrochemical performance of the nitrogen-dopedgraphene-based composite as electrode material is better than that of the undoped graphene-based composite as electrode material. The Nitrogendopedgraphene/Co(OH) 2 composite electrode material was prepared by one-step method.
Currently, nitrogen-dopedgraphene (NG), a novel carbonaceous-derived material, has attracted enormous attention because of its unique properties, including large surface active group to volume ratio, excellent biocompatibility, good electrical conductivity and a high density of active catalytic sites . In addition, recent reports suggested that the incorporation of N dopants in graphene not only displays high binding affinities for metals and metal oxides by means of the nitrogen–metal (N– M) bond, but also improves their catalytic activities . For example, Jiang et al.  synthesized Cu nanoparticles decorated NG (Cu/NG) via a facile thermal treatment and the obtained Cu/NG composite showed significant electrocatalytic activity to glucose oxidation. Balamurugan et al.  obtained a non-enzymatic NADH sensor based on iron nitride nanoparticles-encapsulated NG (FeN/NG). The proposed sensor showed much higher current than than of FeN and NG.
In this study, the electrochemical detection of Se(IV) on a glassy carbon electrode (GCE) modified with nitrogen-dopedgraphene (NG) is reported. NG was synthesized from graphene oxide (GO) by thermal annealing of GO in ammonia. Structural and morphological studies of the synthesized NG were conducted using field emission scanning electron microscopy (FESEM), Raman spectroscopy, high resolution-transmission electron microscopy (HR-TEM), Fourier Transform -infrared spectroscopy (FT- IR) and a CHNS analyzer. Electrochemical characterization of the unmodified GCE and the NG modified GCE (GCE-NG) was conducted using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The newly developed GCE-NG sensor demonstrated improved electrochemical properties when compared to the bare GCE. Square wave anodic stripping voltammetry (SWASV) was employed to optimize the proposed sensors’ detection parameters: 0.1 M HClO 4
There is an easily accessible and low cost approach to generating nitrogen-dopedgraphene (NG). This method is shown through the combination of high exfoliation speed and covalent metamorphose from the melamine (MA)–graphene oxide (GO) mixture. NGs processed during the temperature of 300, 600, and 900 °C featured X-ray photoelectron spectroscopy (XPS) in a systematic way. As for XPS, graphitic-N, pyridinic-N, as well as pyrrolic-N and are regarded to be three major nitrogen-doped frameworks with different proportions. NG modified GCE exerted a strengthening influence on the electrochemical oxidation process. After optimization, the anodic ultimate current of maltol react was in accordance with its concentration ranging from 0.05 μM to 70 μM, along with the detection limit of 0.02 μM, has been obtained.
A magnetic NG@CoFe 2 O 4 photocatalyst was developed via a facile hydrothermal method, and subsequently characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometry (VSM) techniques. The CoFe 2 O 4 nanoparticles were found to have a size between 100-150 nm and were uniformly dispersed on the nitrogendopedgraphene. Magnetic studies showed that the NG@CoFe 2 O 4 photocatalyst can be easily separated from the solution by a simple bar magnet. The photocatalytic degradation of methylene blue dye (MB) was studied under visible irradiation. The photocatalytic performance of NG@CoFe 2 O 4 photocatalyst was found to be influenced by structural and optical properties as well as the surface area of the samples. The NG@CoFe 2 O 4 photocatalyst exhibited improved photodegradation performance when compared with pure CoFe 2 O 4 . The synthesized NG@CoFe 2 O 4 can be a potential candidate as a visible-light active magnetically separable photocatalyst, so could be used as a potent separation tool in waste water treatment.
In this paper a solvethermal synthesized nitrogen-dopedgraphene (NG) was used as modifier on carbon ionic liquid electrode (CILE) to get a novel modified electrode, which was denoted as NG/CILE. An electrochemical hydroquinone (HQ) sensor was constructed with NG/CILE as working electrode. Electrochemical behaviors of HQ on NG/CILE were investigated by cyclic voltammetry with a pair of redox peaks observed. Compared with that of CILE, electrochemical responses of HQ were enhanced greatly with the peak-to-peak separation reduced. The result indicated good electrocatalytic ability of NG/CILE to the redox reaction of HQ. Under the optimal conditions a wider linear response between the peak current and HQ concentration was established in the concentration range from 0.2 to 800.0 μmol L -1 accompanied by a detection limit of 0.625 nmol L -1 (3σ). Furthermore, the as-proposed HQ sensor exhibited high sensitivity and good selectivity toward HQ detection, which was successful applied to the synthetic water samples analysis.
The GO suspension was diluted to 1mg/ml, and then 120ml of the solution and 1.5ml EDA were mixed in a 250ml flask, and refluxed for 6h at 95 o C. After the reaction, the obtained precipitate was freeze-dried to prepare solid FGS. Nitrogen-dopedgraphene was obtained by treating the solid FGS in an automated focused microwave system in the argon protection environment at full power for 1min.
In this paper, nitrogendopedgraphene (NG) was successfully synthesized via thermal annealing employing graphene oxide and urea as raw materials. The morphology and microstructure of NG was characterized by TEM, AFM, XRD and XPS, respectively. Due to its unique structure and properties originating from nitrogendoped in graphene frame, NG shows highly electrocatalytic activity towards the oxidation of p-phenylenediamine (PDA). A sensitive detection platform based on NG modified electrode (NG@GCE) was constructed. Moreover, a low detection limit of 0.67 μM (S/N=3) with the wide linear range of 2 to 500μM and fast response (within 3 s) are obtained. This new strategy opens a new facile and simple route to electrochemically determinate aromatic amines in environmental analysis and other electrocatalytic applications.
A novel sensor was developed based on the electrostatic layer-by-layer (LBL) self-assembly technique on a glassy carbon electrode (GCE) modified with nitrogen-dopedgraphene (NG) and polyethylenimine (PEI). Electrochemical studies exhibit that the assembled NG multilayer films have favorable electron transfer ability and electrocatalytic property, which could enhance the response signal towards dopamine (DA) in the presence of ascorbic acid (AA). In addition, the self-assembly electrode possess an excellent sensing performance for the detection of dopamine with a linear range from 1.0 × 10 -6 M to 1.3 ×10 -4 M, and the detection limit is 5× 10 -7 M (S/N=3).
important carbon nanomaterial in the graphene family. In addition, due to their unique two-dimensional (2D) nanostructural feature, high specific surface area, elec- trochemical stability, and hydrophilic oxygen-containing groups, GO have been widely used as anchored templates to synthesize nanocomposites for DSSC CEs [13, 14]. However, GO suffered relatively high oxygen-containing defects and structural defects such as vacancies and topo- logical defects on the surface. The plenty oxygen- containing defects on the GO surface brought out the low exchange current density, because the surface defects cut down the electrical conductivity . In order to over- come the disadvantages of GO, nitrogen atoms doped into GO to synthesize the nitrogen-doped GO (nGO) were demonstrated to repair the defects, which provided the improvement in the electronic structure of GO . On the other hand, the nitrogen-doped process broadens the electrochemical application area of a variety of carbon- based nanomaterials, including the nitrogen-doped CNT for glucose sensor , the nitrogen-doped re- duced graphene oxide (N-rGO) for the DSSC , the nitrogen-dopedgraphene, and the N-rGO for superca- pacitors [19, 20]. Nitrogen-doped carbon-based nano- materials not only can adjust the work function of graphene  but also can improve the electrical conductivity and the electrochemical properties of the graphene family.
The structural and remarkable properties of different derivatives of graphene have rendered them promising and potential candidates for successful exploitation in electrochemical and biosensing applications. As sensitive and selective as the graphene derivatives have proved to be for the electrochemical sensing of biomarkers such as DA and UA, a great deal of research effort has been devoted to further improving the structural and intrinsic properties of graphene in order to engineer high-performance graphene-based electrochemical sensors that stand a chance to compete with their metal or metal oxide-based counterparts. As such, a variety of surface modification approaches have been explored, including introduction of heteroatoms into the graphene lattice (48, 76, 77) or formation of composite materials of graphene with other carbon nanostructures, polymeric materials, as well as metal and metal oxides (78–85). This is because surface modification increases the surface-area- to-volume ratio of the graphene-based electrode; therefore the signal transduction can be amplified, leading to higher sensitivity compared to the conventional sensing surfaces. Thus, this section reviews the recent surface modification techniques used for the fabrication of graphene-based electrochemical sensors for DA and UA, with the focus on highlighting the design of surfactant-free graphene-based electrodes for DA and UA.
their conductivity and prevent the aggregation of metal species into larger particles . Graphene has also been widely used in hybrid materials such as metal oxides and polymers to enhance the electrochemical activities because of its unique properties such as superior electrical conductivity, excellent mechanical flexibility, and high thermochemical stability .
Nitrogendoped reduced graphene oxide (N-RGO) was prepared by a facile one-step procedure with ammonium hydroxide as the doping regent and hydrazine hydrate as the reducing regent. The obtained N-RGO was characterized by transmission electron microscope (TEM), Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy(XPS). The characterized results validated the successful nitrogen doping of 1.8 at% and the reducing of graphene oxide to RGO. N-RGO modified glassy carbon electrode (N-RGO/GC) was explored for the simultaneous determination of hydroquinone (HQ) and catechol (CC) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The potential separation of the oxidation peaks between HQ and CC were up to 110 mV, which is enough to electrochemical distinguish the dihycroxybenzene isomers. Under the optimal conditions, the oxidation peak currents of HQ and CC linearly increased with the concentrations in the ranges from 5 to 693 and 5 to 492 mol/L, respectively. The detection limits are 0.1 mol/L for HQ and 0.5 mol/L for CC. When simultaneously changing the concentration of the two isomers, the linear range was from 15 to 330 mol/L for both HQ and CC. The relative standard deviations (n=20) are 3.45% for HQ and 3.82 % for CC.
In this article, the changes of N types in graphene were investigated by using different functionalized graphene oxide precursors under varied experimental conditions. The research result shows that low temperature was fa- vorable for the generation of pyridone nitrogen, while high temperature was beneficial to the generation of pyridinic nitrogen. When GO-OOH was used as the precursor, the presence of carboxyl groups was favor- able for the both generations of pyridinic nitrogen and pyridone nitrogen. The GO-OOH-N shows the highest capacitance, and an inferior of GO-OOH-N to GO-N in rate capability at high current density convinced the instability of pseudocapacitance in the fast charge/dis- charge process. Moreover, GO-OOH-N also showed an impressive specific capacitance and cyclic stability after 500 cycles at a discharge current density 1 A/g. These observations demonstrate that the regulation of nitro- gen structures in graphene could be achieved by the well-controlled oxygen groups on graphene surface. We believe that the present way is beneficial for the super- capacitor applications or other fields.
C-N bonds . For example N-doped carbon nanotube (CNT) can fasten direct electron transfer of redox enzymes and the oxygen reduction reaction . Recently N-doped GR (NG) has also been synthesized by different methods such as CVD approach, post-synthesis treatment and solvethermal methods . Nitrogen atom can bond with GR in pyridinic N, pyrrolic N and graphitic C with different ratio. The presence of N in GR can affect the spin density and charge distribution of carbon atoms, which further induces some activation region on the nanosheet with catalytic activity .Therefore NG has also been used in the field of fuel cell, biosensor and electrode modification [8,9].
Herein, NGAs were prepared via a simple one-pot hydrothermal method using graphene oxide (GO) as carbon source and dopamine as nitrogen source. And then, a new electrochemical sensor for MD detection was designed using NGAs modified electrode. With the synergic effects of well-defined 3D porous architecture, large specific surface and highly electrical conductivity of GAs, as well as excellent electrocatalytic ability induced by nitrogen doping, the sensor displayed excellent performance for determination of MD with low detection limit, exceptional sensitivity, and satisfactory stability.
In summary, GTOs, GNOs and RGOs were chosen as graphene-based precursors with melamine by thermal annealing to synthesize three kinds of N-dopedgraphene sheets (N-GT, N-GN and N-RGN). The microstructural characterization show that the N-RGN possess highest specific surface area, largest interlayer distance and most active sites among the three N-dopedgraphene. Moreover, the order of lithium storage properties is N-RGN > N-GN > N-GT. The N-RGN exhibits a high initial reversible capacity of 1250.8 mAh g -1 and maintains in the capacity of 1095.2 mAh g -1 after 30 cycles at a current density of 100 mA g -1 . According to the comparison of microstructure and electrochemical properties, the specific surface area could be a crucial influence factor for the lithium storage capacity of N-dopedgraphene sheets. The experiments and results could be helpful for studying the lithium storage mechanism and developing the high-performance N-dopedgraphene electrode materials for LIBs.
PANI arrays on RGO. The nanocomposites showed high capacitance of 590 F g at 0.1 A g , and had no loss of capacitance after 200 cycles at 2 A g -1 . Carbon nanotube embedded in polypyrrole nanowire electrode showed a loss of 15% of capacitance after 1000 cycles at 1 A g −1 current density . PANI nano fibres were incorporated into GO layers by interfacial polymerization pathway in order to improve the supercapacitor performance of PANI. PANI–GO hybrid composite obtained in semi-crystalline form showed good conductivity (1.7 S cm -1 ) and specific capacitance (365 F g -1 ) higher than PANI (280 F g -1 ) . Synthesis of highly crystalline and conductive GO–PANI composite without using conventional oxidants by in situ polymerization of aniline in the presence of GO as oxidant was reported. The higher conductivity of doped GO–PANI composite as compared to that of GO–PANI obtained by ammonium persulfate assisted polymerization was attributed to higher crystallinity and/or chemical grafting of PANI to GO, which created common conjugated paths between GO and PANI . A potential electrode material for supercapacitor based on Nitrogen-dopedgraphene prepared by pyrolysis of the PANI/GO composite exhibited a high electrochemical performance with specific capacitance up to 206 F g −1 at a current density of 1 A g −1 . The composite also showed an excellent cyclic stability of about 92.5% of the initial value after 1000 cycles at a scan rate of 50 mV s −1 . Carbonaceous shell-coated PANI and polypyrrole electrodes showed capacitance degradations of ~5 and ~15%, respectively after 10000 cycles at a scan rate of 100 mV s −1 .
Few-layer nitrogendopedgraphene was synthesized originating from graphene oxide functionalized by selective oxygenic functional groups (hydroxyl, carbonyl, carboxyl etc.) under hydrothermal conditions, respectively. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) observation evidenced few-layer feature of the graphene oxide. X-ray diffraction (XRD) pattern confirmed phase structure of the graphene oxide and reduced graphene oxide. Nitrogen doping content and bonding configuration of the graphene was determined by X-ray photoelectron spectroscopy (XPS), which indicated that different oxygenic functional groups were evidently different in affecting the nitrogen doping process. Compared with other oxygenic groups, carboxyl group played a crucial role in the initial stage of nitrogen doping while hydroxyls exhibited more evident contribution to the doping process in the late stage of the reaction. Formation of graphitic-like nitrogen species was controlled by a synergistic effect of the involved oxygenic groups (e.g., -COOH, -OH, C-O-C, etc.). The doping mechanism of nitrogen in the graphene was scrutinized. The research in this work may not only contribute to the fundamental understandings of nitrogen doping within graphene but promote the development of producing novel graphene-based devices with designed surface functionalization.