Functionalized Graphene Nanoribbons Research Articles

From carbon nanotubes to functional graphene nanoribbons for high performance supercapacitors

Graphene nanoribbons (GNRs) have great application potential as electrode materials for supercapacitor because of their edge-enriched active surface area, excellent conductivity and unique structure. Here, functional GNRs were prepared by the oxidation unzipping of carbon nanotubes (CNTs) with followed low-temperature heat treatment. Benefiting from the unique one-dimensional structure, a large number of oxygen functional groups (14.41 at.%), and superior specific surface area (184.44 m2 g−1), the optimized GNR-200 electrode achieves a high specific capacitance of 225.9 F g−1 at 0.5 A g−1, which is five times better than that of pure CNTs (39.6 F g−1). Most importantly, the assembled GNR-200//GNR-200 symmetric supercapacitor delivers an energy density of 15.52 Wh kg−1 and good electrochemical stability with the capacitance retention of 92.85 % after 20,000 cycles.

Mechanistic Insights into Electronic Current Flow through Quinone Devices.

Molecular switches based on functionalized graphene nanoribbons (GNRs) are of great interest in the development of nanoelectronics. In experiment, it was found that a significant difference in the conductance of an anthraquinone derivative can be achieved by altering the pH value of the environment. Building on this, in this work we investigate the underlying mechanism behind this effect and propose a general design principle for a pH based GNR-based switch. The electronic structure of the investigated systems is calculated using density functional theory and the transport properties at the quasi-stationary limit are described using nonequilibrium Green's function and the Landauer formalism. This approach enables the examination of the local and the global transport through the system. The electrons are shown to flow along the edges of the GNRs. The central carbonyl groups allow for tunable transport through control of the oxidation state via the pH environment. Finally, we also test different types of GNRs (zigzag vs. armchair) to determine which platform provides the best transport switchability.

Sensitization of TiO2 nanoarrays by a novel palladium decorated naphthalene diimide functionalized graphene nanoribbons for enhanced photoelectrochemical water splitting

As the heart of photoelectrochemical (PEC) cells, the photocatalyst plays a significant role in hydrogen production through PEC water splitting. In this study, the graphene nanoribbon (GNR) was used as a platform for enhancing the semiconductor properties. Naphthalene diimide (NDI) was covalently attached to the GNR surface to improve the light absorption and the charge carrier properties. Due to its unique chemical and electron structure, NDI is highly compatible with GNR and has led to increased electron transport from the photoelectrode surface to the semiconductor conduction band (TiO2). Then, to enhance the electrocatalytic activity of GNR, palladium was immobilized on the platform. The final composition was coated by drop-casting on TiO2 nanoarrays and used as a photoelectrode in a PEC cell. The electrochemical results showed the produced photocurrent density of 1.16 mA/cm2 at 1.1 V vs. RHE, and there was a significant increase compared to unmodified TiO2. The composition was characterized to examine the structures using FTIR, XRD, XPS, FESEM, and HRTEM analysis. Finally, due to the appropriate characteristics of GNR, we can hope for further studies to achieve higher efficiencies in PEC cells.

Applications of Pristine and Functionalized Carbon Nanotubes, Graphene, and Graphene Nanoribbons in Biomedicine.

This review is dedicated to a comprehensive description of the latest achievements in the chemical functionalization routes and applications of carbon nanomaterials (CNMs), such as carbon nanotubes, graphene, and graphene nanoribbons. The review starts from the description of noncovalent and covalent exohedral modification approaches, as well as an endohedral functionalization method. After that, the methods to improve the functionalities of CNMs are highlighted. These methods include the functionalization for improving the hydrophilicity, biocompatibility, blood circulation time and tumor accumulation, and the cellular uptake and selectivity. The main part of this review includes the description of the applications of functionalized CNMs in bioimaging, drug delivery, and biosensors. Then, the toxicity studies of CNMs are highlighted. Finally, the further directions of the development of the field are presented.

Tamoxifen-loaded functionalized graphene nanoribbons for breast cancer therapy

Breast cancer is the second most common cancers among female worldwide. The current treatment strategies includes surgery, chemo-, radio- and hormone-therapy. Nevertheless, breast cancer still accounts for more than 20% of all female cancer deaths, presumably, due to the lack of specificity to target site or the development of drug resistance. Graphene nanoribbons (GNRs) are one of the promising platforms that show efficient cellular internalization and high target specificity for cancer cells. Herein, oxidized graphene nanoribbons (OGNRs), decorated with folic acid (FA) and loaded with the selective estrogen receptor modulator, tamoxifen citrate (TC), were prepared from multi-walled carbon nanotubes using the longitudinal unzipping method. The synthesized TC-loaded OGNRs-FA showed multi-layered structure with drug loading efficiency of 56%. In vitro release studies showed a pH-dependent release of TC from OGNRs. In addition, TC loaded onto OGNRs significantly reduces cell viability and induces apoptosis in MCF-7 and MDA-MB-231 breast cancer cell lines in concentration and-time dependent manner. Most importantly, cellular uptake studies revealed that surface decoration of OGNRs with FA significantly contributed to the preferential cellular internalization of TC-loaded OGRNs-FA by breast cancer cells, compared to naked OGNRs. In vivo pharmacokinetic study suggests that drug loading onto OGNRs-FA remarkably reduced the premature drug release in systemic circulation and, consequently, could enhance the availability of drug payload at the target site. Collectively, OGNRs-FA might represent a promising platform for efficient and selective delivery of tamoxifen to breast cancer cells. However, deep understanding of the in vivo fate and long-term toxicity of OGNRs-FA is crucial for further clinical application.

Tuning flexoelectricty and electronic properties of zig-zag graphene nanoribbons by functionalization

The flexoelectric and electronic properties of zig-zag graphene nanoribbons are explored under mechanical bending using state of the art first principles calculations. A linear dependence of the bending induced out of plane polarization on the applied strain gradient is found. The inferior flexoelectric properties of graphene nanoribbons can be improved by more than two orders of magnitude by hydrogen and fluorine functionalization (CH and CF nanoribbons). A large out of plane flexoelectric effect is predicted for CF nanoribbons. The origin of this enhancement lies in the electro-negativity difference between carbon and fluorine atoms, which breaks the out of plane charge symmetry even for a small strain gradient. The flexoelectric effect can be further improved by co-functionalization with hydrogen and fluorine (CHF Janus-type nanoribbon), where a spontaneous out of plane dipole moment is formed even for flat nanoribbons. We also find that bending can control the charge localization of valence band maxima and therefore enables the tuning of the hole effective masses and band gaps. These results present an important advance towards the understanding of flexoelectric and electronic properties of hydrogen and fluorine functionalized graphene nanoribbons, which can have important implications for flexible electronic applications.

High Rate Capability of a LiNi0.84Co0.12Mn0.04O2 Cathode with a Uniform Conducting Network of Functionalized Graphene Nanoribbons for Li-Ion Batteries

LiNixCoyMnzO2 cathode materials are technologically important for high-energy-density Li-ion batteries. However, poor electronic conductivity limits their practical use compared to conventional LiCoO2 cathodes. There are efforts to the use of multiwalled carbon nanotubes (MWCNTs) as a highly conductive agent, but they have poor dispersibility in most polar solvents. Here, we report a rheological behavior of functionalized graphene nanoribbons (GNRs) and their use for a high rate capability of a LiNi0.84Co0.12Mn0.04O2 cathode. The functionalized GNRs are prepared by chemical unzipping MWCNTs, enabling good dispersion in N-methyl-2-pyrrolidone. The improved dispersibility leads to the slurry with fluid-like behavior and an electrode with a uniform conductive network of carbon black/GNRs, improved cohesion strength, and decreased charge transfer resistance. As a result, the electrode shows the highest capacity retention compared to the electrode with only carbon black or carbon black/MWCNTs at a high 4 C-rate.

CO, CO2, and SO2 detection based on functionalized graphene nanoribbons: First principles study

Abstract In this study, density functional theory (DFT) has been used to build armchair graphene nanoribbon (AGNR) gas sensor and study its capacity to detect carbon monoxide (CO), carbon dioxide (CO2), and sulfur dioxide (SO2) gases. The adsorption of these gases on AGNR was confirmed based on the adsorption energy (Eads), adsorption distance (D), charge transfer (ΔQ), density of states (DOS), and band structure. In order to improve the adsorption capacity, three different modified AGNR systems have been built. AGNR was first functionalized with epoxy (-O-) group (AGNR-O), then with hydroxyl (-OH) group (AGNR-OH), and finally with (-O-) along with (-OH) groups (AGNR-O-OH). Before modification, the adsorption energies have been found to be −0.260, −0.145, and −0.196 eV due to the adsorption of CO, CO2, and SO2, respectively. After modification, the adsorption energy increased remarkably to −0.538 and −0.767 eV for the cases of AGNR-O-OH-CO2 and AGNR-O-OH-SO2, respectively. Indicating that functionalizing the surface of AGNR can improve significantly its performance for the field of gas sensing.

Syntheses and Characterizations of Functional Polycyclic Aromatic Hydrocarbons and Graphene Nanoribbons

Abstract In contrast to zero-bandgap graphene, nanostructures of graphene, such as graphene quantum dots (GQDs) and graphene nanoribbons (GNRs) have open bandgaps due to the quantum confinement effect, and are thus highly interesting for semiconductor applications, for example in nanoelectronics and optoelectronics. While conventional methods cannot provide GQDs and GNRs with chemically precise structures, large polycyclic aromatic hydrocarbon (PAH) molecules can be regarded as atomically precise GQDs. Moreover, extension of the PAH synthesis can lead to GNRs with well-defined chemical structures. In this account, we summarize our recent achievements in our synthetic exploration of PAHs and GNRs with novel structures and properties. For example, we have developed new PAHs having zigzag edges, such as dibenzo[hi,st]ovalene derivatives with strong red luminescence and stimulated emission, which are promising for light-emitting devices and bioimaging applications. We have also accomplished a synthesis of magnetic GNRs through edge functionalization with organic radicals, which can be interesting for spintronic as well as quantum computing applications. Moreover, incorporation of zigzag edges in GNR structures, through on-surface syntheses under ultrahigh (UHV) vacuum conditions, allowed for significant modulations of the electronic structures of GNRs, leading to the emergence of topological quantum phases. On the other hand, we have also explored on-surface synthesis of GNRs without UHV, namely using a setup for chemical vapor deposition (CVD). Scalable fabrication of GNR films could thus be achieved on gold on mica substrates, which could be integrated into field-effect transistor devices. These results highlight the importance of developing novel PAHs and GNRs and their potentials for various applications, including quantum technologies, energy and optoelectronic devices, and bioimaging.

DBD plasma-tuned functionalization of edge-enriched graphene nanoribbons for high performance supercapacitors

Introducing oxygenated functionalities into carbon networks can provide additional pseudocapacitance for supercapacitors. However, excessive and unstable oxygen functional groups usually cause low electrical conductivity and rate performance. Herein, we propose a novel and simple strategy for tunable functionalization of edge-enriched graphene nanoribbons by means of dielectric barrier discharge (DBD) plasma. The functionalized graphene nanoribbons from DBD plasma exhibit high specific capacitance owing to the suitable oxygen functional groups and the intrinsic edge-enriched structure. The assembled symmetric supercapacitor device based on as-prepared graphene nanoribbons with oxygenated functionalities exhibits a superior energy density of 12.65 Wh kg−1, and 93.76% capacitance retention after 10,000 cycles in 1 M Na2SO4 aqueous electrolyte. This work may find a new way to finely control functionalities on carbon nanomaterials for high-performance energy storage devices.

Edge functionalized graphene nanoribbons with tunable band edges for carrier transport interlayers in organic-inorganic perovskite solar cells.

Organic based graphene nanoribbons (GNRs) can be good candidates as carrier extraction interlayers for organic/inorganic hybrid perovskite solar cells, owing to the possibility of tuning the band edge energy levels through varying the width and the type of edge functionalization. By using the density functional theory (DFT) method, the electronic structures of H or F edge functionalized armchair type GNRs on MAPbI3(001) are calculated. It is shown that the electronic structure of H- or F-passivated GNRs is almost undisrupted by the non-covalent interaction with the PbI2 surface layer of MAPbI3(001), thereby one can tune the width and edge chemistry of GNRs to enhance the carrier extraction or blocking. Especially all H-GNRs five to ten carbon atoms wide exhibit good matching for hole extraction, while F-GNRs require a specific width for electron extraction. Exploiting the unzipping synthesis of carbon nanotubes in the solution phase, our result provides a facile strategy for efficient carrier extraction.

Poly (triethoxyvinylsilane-co-quaternaryvinylbenzylchloride)/fGNR based anion exchange membrane and its application towards salt and acid recovery

A novel synthetic route is reported for the preparation of anion exchange membrane and its application towards desalination via electrodialysis and acid recovery via diffusion dialysis. In current study a copolymer based on triethoxyvinylsilane and quaternized vinyl benzyl chloride was synthesized by free radical polymerization using AIBN as an initiator. Further, the property of copolymer was improved by adding different concentration of functionalized graphene nano-ribbons (fGNR). Structural, chemical and morphological parameters was confirmed by FT-IR, AFM, SEM and TEM analysis. Prepared membrane shows excellent thermal, mechanical and chemical stability by the addition of fGNR. The performance of copolymer was analyzed in terms of electrochemical and physicochemical system. The PGR-5 membrane shows hydroxyl ion conductivity of 1.60 × 10−2 S/cm, which is found to be double at 90 °C. The IEC of the membranes was also improved by addition of fGNR. In summary increasing the amount of fGNR in membrane matrix, IEC, ionic conductivity, hydration number, elastic modulus, thermal stability etc. increases while swelling ratio reduces by 30% for PGR-5 membrane compared to PVSi. Prepared composite membranes shows lower power consumption 1.36 kWh/kg with high current efficiency 88.68% for salt removal by electrodialysis. For recovery of HCl, PGR-5 membrane shows its superiority with dialysis coefficient of 0.053 m/h and separation factor of 41. Results show that PGR-5 membrane is a good candidate for electro-membrane processes and diffusion dialysis.

Geminal dicationic ionic liquid functionalized graphene nanoribbon/POAP composite film: synthesis, characterization and electrochemical pseudocapacitance performance

Herein, ionic liquid functionalized graphene nanoribbons (IL-GNR) were fabricated via geminal dicationic ionic liquid, acting as not only a reducing agent but also a functionalizing one. The analyses including scanning electron microscopy (SEM) and X-ray diffraction were employed to investigate the fabricated sample structures. Through the electropolymerization of ortho aminophenol monomers, carried out in the presence of IL-GNR, poly ortho aminophenol (POAP)/(IL-GNR) composite films, functioning as an active electrode in supercapacitor application, were prepared so that the electrochemical behavior of the conducting polymer could be enhanced. For investigation of the system behavior, various electrochemical techniques including cyclic voltammetry (CV) and galvanostatic charge-discharge method as well as electrochemical impedance spectroscopy (EIS) were utilized. Not only the superior active surface area and the composite film conductivity but also the synergistic effect existing between POAP and IL-GNR resulted in the supercapacitive performance of the fabricated composite film.

Nanoconfinement effects of chemically reduced graphene oxide nanoribbons on poly(vinyl chloride).

Polymeric nanocomposites with graphene-based nanocarbons (GNCs) have been extensively studied with emphasis on the percolation of nanofillers toward electrical, rheological, and mechanical reinforcement. In this study, we report an unusual indirect reinforcing phenomenon of highly defective GNCs dispersed in the poly(vinyl chloride) (PVC) matrix via densification of the polymer packing originating from nanoscale confinement. Herein, chemically reduced graphene oxide nanoribbons (C-rGONRs) are employed as a nanofiller. The inclusion of defective and oxygen-functionalized C-rGONRs resulted in a dramatic densification of the PVC host with extremely low C-rGONR loading, largely exceeding the theoretical calculation from a rule of mixture. Along with the densification, the glass transition temperature of PVC also increased by 28.6 °C at 0.1 wt% filler loading. Remarkably, the oxygen barrier property and mechanical toughness under tension for the PVC/C-rGONR nanocomposite were the maximum when the greatest densification occurred. The structure-property relationship of the nanocomposites has been discussed with an emphasis on the nanoscale confinement phenomenon.

Diels–Alder polymerization: a versatile synthetic method toward functional polyphenylenes, ladder polymers and graphene nanoribbons

The Diels–Alder reaction has been widely used in synthetic organic chemistry since its discovery in 1928. The catalyst-free nature, functional group tolerance and high efficiency of the Diels–Alder reaction also make it promising for the fabrication of functional polymeric materials. In particular, a large variety of functional polyphenylenes (polymer structures mainly consisting of phenylenes) and ladder polymers (double-stranded polymers with periodic linkages connecting the strands) have been obtained by this method, offering potential applications such as polymer electrolyte membranes and gas separation. More recently, tailor-made polyphenylenes prepared by Diels–Alder polymerization have been used as precursors of structurally well-defined graphene nanoribbons (ribbon-shaped nanometer-wide graphene segments) with different widths, exhibiting long lengths (>600 nm) and tunable electronic bandgaps. This article provides a comprehensive review of the use of Diels–Alder polymerization to build functional polyphenylenes, ladder polymers and graphene nanoribbons. In this review, we summarize the use of Diels–Alder reaction in the synthesis of arylene-based polymers, including polyphenylenes and ladder polymers, as well as graphene nanoribbons. These polymer materials are structurally related to each other, but rarely discussed all together in a same context. The importance and versatility of the Diels–Alder polymerization is highlighted for the synthesis of such polymers with various potential applications, for example, as polymer electrolyte membrane and organic semiconductors.

Graphene Nanoribbon Based Thermoelectrics: Controllable Self- Doping and Long-Range Disorder.

Control of both the regularity of a material ensemble and nanoscale architecture provides unique opportunities to develop novel thermoelectric applications based on 2D materials. As an example, the authors explore the electronic and thermal properties of functionalized graphene nanoribbons (GNRs) in the single‐sheet and helical architectures using multiscale simulations. The results suggest that appropriate functionalization enables precise tuning of the doping density in a planar donor/acceptor GNR ensemble without the need to introduce an explicit dopant, which is critical to the optimization of power factor. In addition, the self‐interaction between turns of a GNR may induce long‐range disorder along the helical axis, which suppresses the thermal contribution from phonons with long wavelengths, leading to anomalous length independent phonon thermal transport in the quasi‐1D system.

Chemical functionalization and edge doping of zigzag graphene nanoribbon with l-(+)-leucine and group IB elements—A DFT study

First-principles based density functional theory (DFT) calculations have been carried out on the chemically functionalized pure and Cu, Ag and Au doped zigzag graphene nanoribbon (ZGNR(6,0)) with the use of the branched chain amino acid l-(+)-Leucine named as LLZGNR(6,0), LLCuZGNR(6,0), LLAgZGNR(6,0) and LLAuZGNR(6,0) respectively. The structural stability for minimum total energy was confirmed by perturbating the geometry of the relaxed structures. The physical and chemical properties, such as band gap, chemical potential, transmission spectrum, charge transfer, bonding character and Gibb’s free energy of solvation were analysed for all the four systems. It has been observed that the edge doping assisted functionalized systems (LLCuZGNR(6,0), LLAgZGNR(6,0) and LLAuZGNR(6,0)) without the inclusion of spin polarisation are semiconducting in nature. Whereas, barely functionalized system is found to be semi-metallic. An effective space charge polarisation in functionalized graphene nanoribbon has been revealed through charge transfer studies. Hence, it signifies the effective solubility of the nanoribbon in aqueous media. The results indicate the possibility of using such system as nanocarriers in targeted drug delivery applications.

Adsorption of anti-inflammatory nimesulide by graphene materials: a combined theoretical and experimental study.

Interactions of anti-inflammatory nimesulide (NM) with different graphene material species were explored employing both ab initio calculations, based on Density Functional Theory (DFT), and a batch adsorption process. The adsorption of NM onto graphene, with and without a vacancy, reduced graphene oxide (rGO) and functionalized graphene nanoribbons was simulated, providing a good understanding of the adsorption process of the NM molecule onto graphene material surfaces. The theoretical results indicate a physisorption interaction between NM and all of the evaluated adsorbents. Based on batch adsorption experiments, it was found that rGO, obtained via a modified Hummers method, is a good nanoadsorbent for the removal of the anti-inflammatory NM from aqueous solutions. The general-order kinetic equation displays the best fit to the experimental data compared with pseudo-first order and pseudo-second order kinetics. The equilibrium data fitted well into the Liu isotherm equation, and the maximum sorption capacity for the adsorption of NM by rGO was 82.4 mg g-1 at 25 °C. Our results of the first principle calculations and the batch adsorption experiments point out that graphene materials are promising nanomaterials for extracting NM from aqueous solutions.

Poly(ethylene oxide) Functionalized Graphene Nanoribbons with Excellent Solution Processability.

Structurally well-defined graphene nanoribbons (GNRs) have attracted great interest as next-generation semiconductor materials. The functionalization of GNRs with polymeric side chains, which can widely broaden GNR-related studies on physiochemical properties and potential applications, has remained unexplored. Here, we demonstrate the bottom-up solution synthesis of defect-free GNRs grafted with flexible poly(ethylene oxide) (PEO) chains. The GNR backbones possess an armchair edge structure with a width of 1.0-1.7 nm and mean lengths of 15-60 nm, enabling near-infrared absorption and a low bandgap of 1.3 eV. Remarkably, the PEO grafting renders the GNRs superb dispersibility in common organic solvents, with a record concentration of ∼1 mg mL(-1) (for GNR backbone) that is much higher than that (<0.01 mg mL(-1)) of reported GNRs. Moreover, the PEO-functionalized GNRs can be readily dispersed in water, accompanying with supramolecular helical nanowire formation. Scanning probe microscopy reveals raft-like self-assembled monolayers of uniform GNRs on graphite substrates. Thin-film-based field-effect transistors (FETs) of the GNRs exhibit a high carrier mobility of ∼0.3 cm(2) V(-1) s(-1), manifesting promising application of the polymer-functionalized GNRs in electronic devices.

Microwave Heating of Functionalized Graphene Nanoribbons in Thermoset Polymers for Wellbore Reinforcement

Here, we introduce a systematic strategy to prepare composite materials for wellbore reinforcement using graphene nanoribbons (GNRs) in a thermoset polymer irradiated by microwaves. We show that microwave absorption by GNRs functionalized with poly(propylene oxide) (PPO-GNRs) cured the composite by reaching 200 °C under 30 W of microwave power. Nanoscale PPO-GNRs diffuse deep inside porous sandstone and dramatically enhance the mechanics of the entire structure via effective reinforcement. The bulk and the local mechanical properties measured by compression and nanoindentation mechanical tests, respectively, reveal that microwave heating of PPO-GNRs and direct polymeric curing are major reasons for this significant reinforcement effect.