Nitrogen doping has been an effective way to tailor the properties of graphene and render its potential use for various applications. Three common bonding configurations are normally obtained when doping nitrogen into the graphene: pyridinic N, pyrrolic N, and graphitic N. This paper reviews nitrogen-doped graphene, including various synthesis methods to introduce N doping and various characterization techniques for the examination of various N bonding configurations. Potential applications of N-graphene are also reviewed on the basis of experimental and theoretical studies.

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Review on Recent Progress in Nitrogen-Doped Graphene: Synthesis, Characterization, and Its Potential Applications

Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.

Graphene-Based Materials: Synthesis, Characterization, Properties, and Applications

The electronic and chemical properties of graphene can be modulated by chemical doping foreign atoms and functional moieties. The general approach to the synthesis of nitrogen-doped graphene (NG), such as chemical vapor deposition (CVD) performed in gas phases, requires transitional metal catalysts which could contaminate the resultant products and thus affect their properties. In this paper, we propose a facile, catalyst-free thermal annealing approach for large-scale synthesis of NG using low-cost industrial material melamine as the nitrogen source. This approach can completely avoid the contamination of transition metal catalysts, and thus the intrinsic catalytic performance of pure NGs can be investigated. Detailed X-ray photoelectron spectrum analysis of the resultant products shows that the atomic percentage of nitrogen in doped graphene samples can be adjusted up to 10.1%. Such a high doping level has not been reported previously. High-resolution N1s spectra reveal that the as-made NG mainly contai...

Catalyst-Free Synthesis of Nitrogen-Doped Graphene via Thermal Annealing Graphite Oxide with Melamine and Its Excellent Electrocatalysis

Liming Dai,*,†,‡ Yuhua Xue,†,‡ Liangti Qu,* Hyun-Jung Choi, and Jong-Beom Baek* †Center of Advanced Science and Engineering for Carbon (Case4Carbon), Department of Macromolecular Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Department of Chemistry, School of Science, Beijing Institute of Technology, Beijing 100081, People’s Republic of China School of Energy and Chemical Engineering/Center for Dimension-Controllable Covalent Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon, Ulsan, 689-798, South Korea

Metal-free catalysts for oxygen reduction reaction.

Graphene quantum dots (GQDs) represent a new class of quantum dots with unique properties. Doping GQDs with heteroatoms provides an attractive means of effectively tuning their intrinsic properties and exploiting new phenomena for advanced device applications. Herein we report a simple electrochemical approach to luminescent and electrocatalytically active nitrogen-doped GQDs (N-GQDs) with oxygen-rich functional groups. Unlike their N-free counterparts, the newly produced N-GQDs with a N/C atomic ratio of ca. 4.3% emit blue luminescence and possess an electrocatalytic activity comparable to that of a commercially available Pt/C catalyst for the oxygen reduction reaction (ORR) in an alkaline medium. In addition to their use as metal-free ORR catalysts in fuel cells, the superior luminescence characteristic of N-GQDs allows them to be used for biomedical imaging and other optoelectronic applications.

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Nitrogen-Doped Graphene Quantum Dots with Oxygen-Rich Functional Groups

Nitrogen-doped graphene (N-graphene) is obtained by exposing graphene to nitrogen plasma. N-graphene exhibits much higher electrocatalytic activity toward oxygen reduction and H2O2 reduction than graphene, and much higher durability and selectivity than the widely-used expensive Pt for oxygen reduction. The excellent electrochemical performance of N-graphene is attributed to nitrogen functional groups and the specific properties of graphene. This indicates that N-graphene is promising for applications in electrochemical energy devices (fuel cells, metal–air batteries) and biosensors.

/pdf/nitrogen-doped-graphene-and-its-electrochemical-applications-4eqzkmr550.pdf

Nitrogen-doped graphene and its electrochemical applications

We report on a novel fabrication technology for building a waveguide system with its core and cladding both formed by Polydimethylsiloxane (PDMS). The refractive index difference is realized by controlling the mixing ratio of base and curing agent. The entire process only requires regular PDMS material and is completely compatible with soft lithography process. The experimental results show a good confinement of light and the transmission loss was about 1.1 dB/cm at 460 nm.

A new fabrication method for all-PDMS waveguides

A new polydimethylsiloxane (PDMS) double casting technique is presented for the fabrication of high-aspect-ratio flexible microstructures. Experimental results showed that microstructures with aspect-ratio as high as 20 can be consistently replicated with high fidelity. Microstructures on the master mold were first replicated onto a PDMS negative mold using conventional soft lithography process. The resulting negative mold was then used to cast secondly PDMS replicas. A corona discharge treatment assisted surface modification process was developed for PDMS to PDMS casting. The whole process requires no expensive equipment and can be easily carried out in most labs. With this technique, molding replicas with same structures as the master mold can be obtained, in comparison to the conventional molding process in which an opposite of the master mold is obtained. This technique may greatly simplify the design and fabrication of master molds, provide more flexibility to widely used soft lithography process, and also reduce the damage to the master by using PDMS negative mold as the working mold.

Fabrication of elastomeric high-aspect-ratio microstructures using polydimethylsiloxane (PDMS) double casting technique

A renewable flow cell integrating a microstruc- tured pillar-array filter and a pneumatic microvalve was micro- fabricatedtotrapandreleasebeads.Abead-basedimmunoassay using this device was also developed. This microfabricated device consists of a microfluidic channel connecting to a beads chamber in which the pillar-array filter is built. Underneath the filter, there is a pneumatic microvalve built across the chamber. Such a device can trap and release beads in the chamber by "closing" or "opening" the microvalve. On the basis of the pneumatic microvalve,thedevice cantrapbeadsinthechamber before performing an assay and release the used beads after the assay. Therefore, this microfabricated device is suitable for "renewable surface analysis". A model analyte, 3,5,6-trichloropyridinol (TCP), was chosen to demonstrate the analytical performance of the device. The entire fluidic assay process, including beads trapping, immuno binding, beads washing, beads releasing, and chemiluminesence signal collection, could be completed in 10 min. The immunoassay of TCP using this microfabricated device showed a linear range of 0.20-70 ng/mL with a limit of detection of 0.080 ng/mL. The device was successfullyusedtodetectTCPspikedinhumanplasmaattheconcentrationrangeof1.0-50ng/mL,withananalyticalrecoveryof 81-110%. The results demonstrated that this device can provide a rapid, sensitive, reusable, low-cost, and automatic tool for detecting various biomarkers in biological fluids.

Microfabricated Renewable Beads-Trapping/Releasing Flow Cell for Rapid Antigen−Antibody Reaction in Chemiluminescent Immunoassay

A novel and versatile processing method was developed for the formation of gel scaffolds with in situAChE–AuNPs immobilization for biosensing of organophosphorus compounds. The biosensor designed by our new approach shows high sensitivity, selectivity and reactivation efficiency. This flow-induced immobilization technique opens up new pathways for designing a simple, fast, biocompatible, and cost-effective process for enhanced sensor performance and on-site monitoring of a variety of toxic organophosphorus compounds.

Enzyme entrapped nanoporous scaffolds formed through flow-induced gelation in a microfluidic filter device for sensitive biosensing of organophosphorus compounds

Guocheng Shao

Papers

Nitrogen-doped graphene and its electrochemical applications

A new fabrication method for all-PDMS waveguides

Fabrication of elastomeric high-aspect-ratio microstructures using polydimethylsiloxane (PDMS) double casting technique

Microfabricated Renewable Beads-Trapping/Releasing Flow Cell for Rapid Antigen−Antibody Reaction in Chemiluminescent Immunoassay

Enzyme entrapped nanoporous scaffolds formed through flow-induced gelation in a microfluidic filter device for sensitive biosensing of organophosphorus compounds