N-doped Graphene Nanoribbons Research Articles

N-Doped Hybrid Graphene and Boron Nitride Armchair Nanoribbons As Nonmagnetic Semiconductors with Widely Tunable Electronic Properties

The electronic and chemical properties of N-doped hybrid graphene and boron nitride armchair nanoribbons (N-doped a-GBNNRs) in comparison with graphene armchair nanoribbon (pristine a-GNR) and hybrid graphene and boron nitride armchair nanoribbon (C-3BN) are investigated using the density functional theory method. The results show that all the mentioned nanoribbons are nonmagnetic direct semiconductors and all the graphitic N-doped a-GBNNRs are n-type semiconductors while the rest are p-type semiconductors. The N-doped graphitic 2 and N-doped graphitic 3 structures have the lowest work function and the highest number of valence electrons (Lowdin charges) which confirms that they are effective for use in electronic device applications.

Monodisperse N-Doped Graphene Nanoribbons Reaching 7.7 Nanometers in Length.

The properties of graphene nanoribbons are highly dependent on structural variables such as width, length, edge structure, and heteroatom doping. Therefore, atomic precision over all these variables is necessary for establishing their fundamental properties and exploring their potential applications. An iterative approach is presented that assembles a small and carefully designed molecular building block into monodisperse N‐doped graphene nanoribbons with different lengths. To showcase this approach, the synthesis and characterisation of a series of nanoribbons constituted of 10, 20 and 30 conjugated linearly‐fused rings (2.9, 5.3, and 7.7 nm in length, respectively) is presented.

A sensitive sandwich-type immunosensor for the detection of galectin-3 based on N-GNRs-Fe-MOFs@AuNPs nanocomposites and a novel AuPt-methylene blue nanorod

We are presenting an electrochemical immunosensor for the determination of Galectin-3 (Gal-3), a biomarker of heart failure. A glassy carbon electrode (GCE) was modified with a film of a composite made from the N-doped graphene nanoribbons immobilized Fe-based-Metal-organic frameworks deposited with Au nanoparticles (N-GNRs-Fe-MOFs@AuNPs). Primary antibody against Gal-3 (Gal-3-Ab1) was immobilized on the Au nanoparticles on the surface of the modified GCE which then was blocked with bovine serum albumin. Signal amplification is crucial for obtaining low detection limits in biosensors. Here, a relatively simple and ultrasensitive sandwich-type electrochemical immunosensor based on novel signal generation and amplification was developed for the determination of Gal-3. A kind of novel redox-active species, AuPt-Methylene blue (MB) (AuPt-MB) nanocomposites, was synthesized by a one-pot method for the first time. Wherein, MB as a kind of the electron transfer mediators in an amperometric biosensor is responsible for electron production and signal amplification. The rod-like AuPt-MB nanohybrids displayed uniform morphology and good electrochemical activity and can combine with the second antibodies against Gal-3 (Gal-3-Ab2). And the AuPt-MB-Ab2 coupled with the N-GNRs-Fe-MOFs@AuNPs-Ab1 to form the sandwich type format that can greatly enhance the biosensor's sensitivity. Under optimal conditions, the designed immunosensor exhibited a linear concentration range from 100fgmL−1 to 50ngmL−1, with a low detection limit of 33.33fgmL−1 (S/N = 3) for Gal-3 in spiked serum. Additionally, the designed immunosensor showed acceptable selectivity, reproducibility and stability. The satisfactory results in analyzing human serum samples indicated potential application promising in monitoring biomarkers.

A dual-type responsive electrochemical immunosensor for quantitative detection of PCSK9 based on n-C60-PdPt/N-GNRs and Pt-poly (methylene blue) nanocomposites

In this study, a dual-type responsive electrochemical immunosensor was developed for the quantitative detection of proprotein convertase subtilisin/kexin type 9 (PCSK9), a potential biomarker of cardiovascular disease in serum. N-doped graphene nanoribbons (N-GNRs) with good conductivity were used as the sensing matrix modifying the glassy carbon electrode. Palladium platinum alloy (PdPt) nanoparticles with high catalytic performance toward the reduction of hydrogen peroxide (H2O2) were reduced onto amino-functionalized fullerene (n-C60-PdPt) and significantly amplified the electrochemical signal recorded by the amperometric i-t curve. Furthermore, staphylococcus protein A (SPA) with antibody orientation function was introduced to improve the immunoreaction efficiency. Accordingly, a label-free immunosensor was fabricated based on n-C60-PdPt/N-GNRs for the quick detection of PCSK9. Meanwhile, to realize ultrasensitive detection of PCSK9, Pt-poly (methylene blue) (Pt-PMB) nanocomposites synthesized by a one-pot method for the first time were used as a novel signal label, which exhibited uniform morphology as well as good conductivity and produced an electrochemical signal recorded by differential pulse voltammetry (DPV). Herein, a novel sandwich-type immunosensor was designed using n-C60-PdPt/N-GNRs as the sensing matrix and Pt-PMB as the signal label for sensitive detection of PCSK9. Under optimal conditions, the label-free immunosensor showed a linear range of 10pgmL−1 to 100ngmL −1 with a detection limit of 3.33pgmL−1 (S/N=3), and the sandwich-type immunosensor exhibited a linear range of 100 fg mL−1 to 100ngmL −1 with a detection limit of 0.033pgmL−1 (S/N=3) for PCSK9 detection, indicating its potential application in clinical bioassay analysis.

Mechanism of sodium adsorption on N-doped graphene nanoribbons for sodium ion battery applications: A density functional theory approach

Density functional theory (DFT) calculations were employed to investigate the adsorption and diffusion mechanisms of sodium on graphene nanoribbons (GNR). The calculated adsorption energy in the edge region (−1.096 eV) of pristine GNR was lower than that for the center region (−0.836 eV). In addition, the adsorption energies on GNRs with nitrogen-doped defects (4ND, 3NV, and pyrrolic: −3.794 to −1.837 eV) were lower than that for the pristine-GNR edge (−1.096 eV). The adsorption properties of sodium on GNRs were strongly affected by the introduction of nitrogen defects. Band structure analysis revealed that the 3s valance orbital of sodium is raised in energy when sodium is strongly adsorbed on the GNR. Moreover, when the sodium is adsorbed in close proximity to the nitrogen atoms, the p orbital of nitrogen is lowered in energy due to strong interactions between the sodium and adjacent nitrogen atoms. Although improved adsorption of sodium on GNRs with nitrogen-doped defects was observed, the diffusion energy barrier obtained for sodium on the pyrrolic-GNR (0.009–0.021 eV) was lower than that for the pristine-GNR (0.019–0.079 eV). Therefore, the adsorption and diffusion properties of sodium on GNRs can be beneficially affected by the introduction of nitrogen-doped defects at the GNR edge.

A new method for developing defect-rich graphene nanoribbons/onion-like carbon@Co nanoparticles hybrid materials as an excellent catalyst for oxygen reactions.

Herein, a novel material with an excellent electrocatalytic activity for the oxygen reduction reaction (ORR), composed of onion-like carbon@Co nanoparticles (NPs) incorporated on defect-rich N-doped graphene nanoribbons (C@Co-NGR), is prepared via a combination of nitric acid etching and subsequent high-temperature treatment of the as-synthesized C@Co-N doped carbon nanotubes. The as-prepared C@Co-NGR exhibits excellent electrocatalytic activity for the ORR in 0.10 M KOH with a half-wave potential of 0.830 V (vs. a reversible hydrogen electrode, RHE), which is 21 mV more positive than that of a commercial 20 wt% Pt/C catalyst. Moreover, it shows a higher stability and better methanol tolerance than the commercial Pt/C catalyst in alkaline solution, with almost no shift in the ORR polarization curve after 3000 cycles and no change of the ORR peak in the cyclic voltammogram in the presence of 1.0 M methanol. Most importantly, the C@Co-NGR also exhibits a comparable activity for the oxygen evolution reaction (OER) in 0.10 M KOH solution, in which the overpotential needed to achieve a current density of 10 mA cm-2 is 410 mV, comparable to that of the state-of-the-art commercial RuO2 catalyst (370 mV, vs. RHE). This makes the C@Co-NGR one of the best non-precious-metal catalyst for OER and ORR in alkaline solution ever reported.

Nitrogen-doped nanocarbon materials under electroreduction operating conditions and implications for electrocatalysis of CO2

We have used Kohn-Sham density functional theory with atomistic thermodynamics to identify various forms of N-doped graphene basal planes and nanoribbons that are thermodynamically relevant for CO2 electroreductions. Using our computational results, we derive phase diagrams for different nanocarbon structures, and we report which structures are suitable for hydrogen transfers to CO2 with low overpotentials. With the incorporation of N atoms, standard reduction potentials resulting in hydrogenated surfaces become less negative, and this effectively opens pathways for hydrogen atom shuttling to CO2 with reversibly hydrogenating nanocarbon catalysts. Of all morphologies considered, N-doped zigzag nanocarbon edges are most favorable for energetically efficient CO2 electroreductions.

Efficient spin-filter and negative differential resistance behaviors in FeN4 embedded graphene nanoribbon device

In this paper, we propose a new device of spintronics by embedding two FeN4 molecules into armchair graphene nanoribbon and sandwiching them between N-doped graphene nanoribbon electrodes. Our first-principle quantum transport calculations show that the device is a perfect spin filter with high spin-polarizations both in parallel configuration (PC) and antiparallel configuration (APC). Moreover, negative differential resistance phenomena are obtained for the spin-down current in PC, and the spin-up and spin-down currents in APC. These transport properties are explained by the bias-dependent evolution of molecular orbitals and the transmission spectra.

DFT-based study on the mechanisms of the oxygen reduction reaction on Co(acetylacetonate)2supported by N-doped graphene nanoribbon

The hybridization of Co(acac)2with N-doped graphene can give rise to outstanding catalytic performance for ORR in fuel cells.

Magnetism of N-doped graphene nanoribbons with zigzag edges from bottom-up fabrication

Two graphene nanoribbons with atomically precise N-doping zigzag edges from bottom-up fabrication by a condensation reaction exhibited intrinsically magnetic properties with a maximum magnetization of 0.303 emu g−1.

Bipolar spin-filtering effect in B- or N-doped zigzag graphene nanoribbons with asymmetric edge hydrogenation

The spin transport properties of zigzag graphene nanoribbon (ZGNR) hetero-junctions, in which ZGNR electrodes are doped with B or N atoms, are investigated based on spin-polarized density functional theory and non-equilibrium Green's function. ZGNRs are C–H2 bonded at one edge and C–H bonded at the other edge to form asymmetric edge hydrogenation. The spin-polarized currents of ZGNR-based nano-devices with an odd or even number of the zigzag-shaped chains show a perfect bipolar spin-filtering effect on parallel and anti-parallel magnetic configurations. This study provides insights into the design of high-performance graphene-based spin filters.

Highly sensitive electrochemical immunosensor for the detection of alpha fetoprotein based on PdNi nanoparticles and N-doped graphene nanoribbons.

An ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of alpha fetoprotein (AFP). The β-cyclodextrins functionalized graphene sheets (CD-GS) were used as the sensing matrix for immobilizing adamantine-1-carboxylic acid functionalized primary anti-AFP (ADA-Ab1) and enhanced the electron transfer. PdNi alloy nanoparticles decorated N-doped graphene nanoribbons (PdNi/N-GNRs) were used as labels of secondary anti-AFP (Ab2), and PdNi alloy nanoparticles (PdNi NPs) exhibited high catalytic performance towards the reduction of H2O2. Meanwhile, with good dispersion, large specific surface area and good catalytic performance, N-doped graphene nanoribbons (N-GNRs) significantly amplified the electrochemical signal. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.0001-16 ng/mL with a low detection limit of 0.03 pg/mL. Additionally, the proposed immunosensor showed high specificity, good reproducibility and long-term stability, which have promising application in bioassay analysis.

N-Doped Zigzag Graphene Nanoribbons on Si(001): a First-Principles Calculation**Supported by the National Natural Science Foundation of China under Grant No 11204296, and the National Basic Research Program of China under Grant No 2013CB933304.

The structural and electronic properties of N-doped zigzag graphene nanoribbons (N-ZGNRs) adsorbed on Si(001) substrates are investigated with first-principles density functional calculations. Compared with the free-standing N-ZGNRs, the energy difference between the substitutional doping at the edge and the inner sites is significantly decreased on the Si substrate. The distribution of the extra charge induced by the N substitutional dopant keeps the Friedel oscillation feature, and is a main effect that influences the C–Si bonding strength. When N is doped in regions with high C–Si bond densities, the strain induced by the dopant also plays an important role in determining the C–Si bonding interactions. Similar to the undoped case, the strong N-ZGNR/Si interaction destroys the antiferromagnetic coupling of the edge states in N-ZGNR, leading to a non-magnetic ground state for the N-ZGNR/Si heterostructures.

Graphene Nanoribbons: Nitrogen‐Doped Graphene Nanoribbons with Surface Enriched Active Sites and Enhanced Performance for Dye‐Sensitized Solar Cells (Adv. Energy Mater. 11/2015)

N-doped graphene nanoribbons (N-GNRs) with surface enriched active sites and superb electrochemical activity are reported by Chang Yu, Jieshan Qiu, and co-workers in article number 1500180. The N-GNRs, which are a type of novel functional carbon composite made of in situ built-in 1D and 2D nanocarbons, exhibit excellent stability and a remarkable efficiency of 8.57% in I3-/I-electrolyte when used as counter electrodes in dye-sensitized solar cells.

N-doped graphene nanoribbons as efficient metal-free counter electrodes for disulfide/thiolate redox mediated DSSCs.

Nitrogen-doped graphene nanoribbons (N-GNRs) were prepared by thermal treatment of the as-zipped graphene oxide nanoribbons in NH3 gas. X-ray photoelectron spectroscopy (XPS) measurements revealed a high nitrogen content up to 6.5 atom% for the as-prepared N-GNRs. This, together with the high Brunauer-Emmett-Teller (BET) surface area of about 751 cm(2) g(-1), prompted us to use the N-GNR as the first low-cost, metal-free counter electrode for disulfide/thiolate redox mediated dye-sensitized solar cells (DSSCs). Compared with the widely-used platinum electrode, the newly-developed N-GNR counter electrode showed a dramatically improved power conversion efficiency for DSSCs based on the thiolate/disulfide redox shuttle. The observed superior cell performance was attributed to the enhanced charge transfer capability and electrocatalytic activity induced by N-doping of the graphene nanoribbon.

Understanding the structure and electronic properties of N-doped graphene nanoribbons upon hydrogen saturation

Structures and electronic properties of zigzag graphene nanoribbon (ZGNR) with pyridine (3NV-ZGNR) functionalized by Scandium (Sc) at the edge were studied through quantum chemical calculations in the formalism of density-functional theory (DFT). Pyridine-like nitrogen defects is very crucial for enhancing the Sc atom binding to the defects and is thermodynamically favoured. During Sc decoration of ZGNR there is a shift from 0.35 eV small gap semiconductor regime to that of a metal which can be used for band gap tuning by controlled saturation of Sc. ZGNR decorated with Sc can attract H2. Upon saturation of multiple H2 in quasi-molecular fashion, the metallic character is converted to semiconductors of small gap of 0.10 eV, which are predicted to be interesting materials not only for hydrogen storage but also for their band gap engineered properties.

Negative differential resistance devices by using N-doped graphene nanoribbons.

Recently, extensive efforts have been devoted to the investigations of negative differential resistance (NDR) behavior in graphene. Here, by performing fully self-consistent density functional theory calculations combined with non-equilibrium Green's function technique, we investigate the transport properties of three molecules from conjugated molecule, one-dimension alkane chain, and single molecule magnet, which are sandwiched between two N-doped zigzag and armchair graphene nanoribbons (GNRs). We observe robust NDR effect in all examined molecular junctions including benzene, alkane, and planar four-coordinated Fe complex. Through the analyses of the calculated electronic structures and the bias-dependent transmission coefficients, we find that the narrow density of states of N-doped GNRs and the bias-dependent effective coupling between the discrete frontier molecular orbitals and the subbands of N-doped GNRs are responsible for the observed NDR phenomenon. These theoretical findings imply that N-doped GNRs hold great potential for building NDR devices based on various molecules.

Iron-phthalocyanine molecular junction with high spin filter efficiency and negative differential resistance

We investigate the spin transport properties of iron-phthalocyanine (FePc) molecule sandwiched between two N-doped graphene nanoribbons (GNRs) based on the density functional theory and nonequilibrium Green's function methods. Our calculated results clearly reveal that the FePc molecular junction has high spin-filter efficiency as well as negative differential resistance (NDR). The zero-bias conductance through FePc molecule is dominated by the spin-down electrons, and the observed NDR originates from the bias-dependent effective coupling between the FePc molecular orbitals and the narrow density of states of electrodes. The remarkable high spin-filter efficiency and NDR are robust regardless of the edge shape and the width of GNRs, and the N-doping site in GNRs. These predictions indicate that FePc junction holds great promise in molecular electronics and spintronics applications.

The effect of N-doping on the electronic structure of graphene nanoribbon

To analyse the effect on electronic structure of nitrogen-doped graphene nanoribbons, the parameters such as the lattice, band structure, density of states of intrinsic graphene nanoribbon, N-doped graphene nanoribbons are calculated by using first-principle method. The results demonstrate that the band gap of graphene nanoribbon mainly comes from the new surface states in the edge. The N-doping in the middle of graphene nanoribbon has less influence on the band gap performance than in the edge region, which indicates the atoms in the edge do great contribution to the band gap properties. The N-doping makes the band gap narrower; the sharp changes of the band gap also show that the N-doping is a promising candidate to make the n-type graphene structures.

Physical Insight Into Substitutional N-Doped Graphene Nanoribbons With Armchair Edges

Electronic structures of graphene nanoribbons with armchair edges (AGNRs) containing N-substitutional impurity have been investigated, using ab initio density functional theory. It is shown that the electronic structures of the doped AGNRs are different from those of doped carbon nanotubes (CNTs). N introduces an impurity level above the conduction band minimum (CBM) in the AGNRs while an impurity level introduced by N is below the CBM in the CNTs. This character can be explained as a consequence of the edge polarization effects, which ionize the impurity level so that the relevant charge carriers occupy the conduction bands, which is independent of curvature and doping site. Although the N-doped AGNR and CNT are all n-type semiconductors, an implication of the result is that edge polarization effects could make some properties of the N-doped AGNRs different from those of N-doped CNTs. It suggests the possibility to make 1-D doped structures with novel physical and device characteristics.