Graphene has been hailed as a wonderful material in electronics, and recently, it is the rising star in photonics, as well. The wonderful optical properties of graphene afford multiple functions of ...signal emitting, transmitting, modulating, and detection to be realized in one material. In this paper, the latest progress in graphene photonics, plasmonics, and broadband optoelectronic devices is reviewed. Particular emphasis is placed on the ability to integrate graphene photonics onto the silicon platform to afford broadband operation in light routing and amplification, which involves components like polarizer, modulator, and photodetector. Other functions like saturable absorber and optical limiter are also reviewed.
Covalent organic frameworks (COFs) are constructed from the precise integration of small organic blocks into an extended, porous framework
via
covalent linkages. COFs can also be viewed as an organic ...solid consisting of a periodic array of one dimensional (1-D) channels. Although a wide range of applications have been envisioned for COFs, understanding the structure-property correlation at the level of chemical linkages, topology, pore size and functionality is needed to unlock the potential of these materials. Herein, we review some emerging applications of two-dimensional (2D) COFs in solid-state photoluminescence, stimuli-responsive COFs, gas storage, ion conduction and energy storage, and discuss the intricate design principles that enable these COFs to perform better than their building blocks or polymeric counterparts. Going beyond bulk 2D-COFs, molecular thin organic layers called COFene can be derived from the exfoliation of 2D COFs, generating new properties for applications in optoelectronic devices, catalysis and separation.
This review provides guidelines for the function-oriented synthesis of 2D COFs from 3D solids to 2D sheets.
A composite made from the assembly of graphene oxide (GO) and copper‐centered metal organic framework (MOF) shows good performance as a tri‐functional catalyst in three important electrocatalysis ...reactions, namely: the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). One of the challenges in the area of electrocatalysis is to find an effective catalyst that will reduce, as well as generate, oxygen at moderate temperatures. The enhanced electrocatalytic properties and stability in acid of the GO‐MOF composite is due to the unqiue porous scaffold structure, improved charge transport and synergistic interactions between the GO and MOF. In polymer electrolyte membrane fuel cell testing, the GO‐incorporated Cu‐MOF composite delivers a power density that is 76% that of the commercial Pt catalyst.
A graphene oxide and copper‐centered metal organic framework composite shows good performance as a tri‐functional catalyst for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR).
Pyridine-functionalized graphene (reduced graphene oxide) can be used as a building block in the assembly of metal organic framework (MOF). By reacting the pyridine-functionalized graphene with ...iron–porphyrin, a graphene–metalloporphyrin MOF with enhanced catalytic activity for oxygen reduction reactions (ORR) is synthesized. The structure and electrochemical property of the hybrid MOF are investigated as a function of the weight percentage of the functionalized graphene added to the iron–porphyrin framework. The results show that the addition of pyridine-functionalized graphene changes the crystallization process of iron–porphyrin in the MOF, increases its porosity, and enhances the electrochemical charge transfer rate of iron–porphyrin. The graphene–metalloporphyrin hybrid shows facile 4-electron ORR and can be used as a promising Pt-free cathode in alkaline Direct Methanol Fuel Cell.
Graphene oxide (GO) can be considered as one of the most visible outcomes of graphene research in terms of large scale production and commercialization prospects. Although GO can be easily prepared ...by oxidation-exfoliation of graphite in agitated solutions, the size of these sheets is generally limited due to fragmentation along fault lines during chemical oxidation and exfoliation in agitated solutions. In this account, we discuss recent strategies which have been developed for the preparation of large sized graphene oxide (LGO) sheets with lateral sizes >10 μm, using chemically expanded graphite as the starting material. LGO has a much lower density of defects than GO prepared using the conventional Hummers' method and can be readily transformed into graphene by chemical reduction. In addition, the unique advantages of using LGO sheets as a performance enhancer are discussed. Finally, this review also discusses recent advances in the chemical and electrochemical reduction of graphene oxide.
Graphene oxide (GO) can be considered as one of the most visible outcomes of graphene research in terms of large scale production and commercialization prospects.
Covalent organic frameworks (COFs) are an emerging class of porous crystalline materials constructed from designer molecular building blocks that are linked and extended periodically via covalent ...bonds. Their high stability, open channels, and ease of functionalization suggest that they can function as a useful cathode material in reversible lithium batteries. Here, a COF constructed from hydrazone/hydrazide‐containing molecular units, which shows good CO2 sequestration properties, is reported. The COF is hybridized to Ru‐nanoparticle‐coated carbon nanotubes, and the composite is found to function as highly efficient cathode in a Li–CO2 battery. The robust 1D channels in the COF serve as CO2– and lithium‐ion‐diffusion channels and improve the kinetics of electrochemical reactions. The COF‐based Li–CO2 battery exhibits an ultrahigh capacity of 27 348 mAh g−1 at a current density of 200 mA g−1, and a low cut‐off overpotential of 1.24 V within a limiting capacity of 1000 mAh g−1. The rate performance of the battery is improved considerably with the use of the COF at the cathode, where the battery shows a slow decay of discharge voltage from a current density of 0.1 to 4 A g−1. The COF‐based battery runs for 200 cycles when discharged/charged at a high current density of 1 A g−1.
A covalent organic framework (COF) is deployed in a Li–CO2 battery to function as diffusion channels to improve gas/ion migration. Owing to its ability for CO2 capture/release, the COF greatly increases the battery's specific discharge capacity. Importantly, the COF also enhances the battery's rate performance and cycling life at high current density due to the presence of the 1D channels that enable fast gas/ion diffusion.
Solution-Gated Epitaxial Graphene as pH Sensor Ang, Priscilla Kailian; Chen, Wei; Wee, Andrew Thye Shen ...
Journal of the American Chemical Society,
11/2008, Letnik:
130, Številka:
44
Journal Article
Recenzirano
A solution-gate field effect transistor (SGFET) has been fabricated on few-layer graphene (FLG). The ideally polarizable graphene/aqueous electrolyte interface allows the capacitive charging of the ...surface by hydroxyl (OH−) and hydroxonium ions (H3O+). The conductivity versus gate potential curve exhibits “V” shaped ambipolar transfer characteristics of graphene, with hole and electron mobilities of 3600 cm2/Vs and 2100 cm2/Vs, respectively. The shift of the negative gate potential with pH shows a supra-Nernstian response of 99 meV/pH. Our work points to the potential application of graphene in ultrafast and ultralow noise chemical or biological sensors.
Chemically derived graphene oxide (GO) is an atomically thin sheet of graphite that has traditionally served as a precursor for graphene, but is increasingly attracting chemists for its own ...characteristics. It is covalently decorated with oxygen-containing functional groups - either on the basal plane or at the edges - so that it contains a mixture of sp(2)- and sp(3)-hybridized carbon atoms. In particular, manipulation of the size, shape and relative fraction of the sp(2)-hybridized domains of GO by reduction chemistry provides opportunities for tailoring its optoelectronic properties. For example, as-synthesized GO is insulating but controlled deoxidation leads to an electrically and optically active material that is transparent and conducting. Furthermore, in contrast to pure graphene, GO is fluorescent over a broad range of wavelengths, owing to its heterogeneous electronic structure. In this Review, we highlight the recent advances in optical properties of chemically derived GO, as well as new physical and biological applications.
An interface engineering process to deploy graphene film as the anode in poly(3‐hexylthiophene‐2,5‐diyl):6,6‐phenyl C61 butyric acid methyl ester (P3HT:PCBM)‐based polymer solar cells is ...demonstrated. By modifying the interface between the graphene anode and the photoactive layer with MoO3 and poly(3,4‐ethylenedioythiophene):poly(styrenesulfonate) (PEDOT:PSS), the power conversion efficiency of the solar cells reaches ≈83.3% of control devices that use an indium tin oxide (ITO) anode.
Transition-metal dichalcogenides like molybdenum disulphide have attracted great interest as two-dimensional materials beyond graphene due to their unique electronic and optical properties. ...Solution-phase processes can be a viable method for producing printable single-layer chalcogenides. Molybdenum disulphide can be exfoliated into monolayer flakes using organolithium reduction chemistry; unfortunately, the method is hampered by low yield, submicron flake size and long lithiation time. Here we report a high-yield exfoliation process using lithium, potassium and sodium naphthalenide where an intermediate ternary Li(x)MX(n) crystalline phase (X=selenium, sulphur, and so on) is produced. Using a two-step expansion and intercalation method, we produce high-quality single-layer molybdenum disulphide sheets with unprecedentedly large flake size, that is up to 400 μm(2). Single-layer dichalcogenide inks prepared by this method may be directly inkjet-printed on a wide range of substrates.
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