Covalent Functionalization of Strained Graphene

An enhancement of the chemical activity of graphene is evidenced by first‐principles modelling of the chemisorption of hydrogen, fluorine, oxygen and hydroxyl groups on strained graphene. For the case of negative strain or compression, chemisorption of the single hydrogen, fluorine or hydroxyl group is energetically more favourable than those of their pairs on different sublattices. This behaviour stabilizes the magnetism caused by the chemisorption being against its destruction by the pair formations. Initially flat, compressed graphene is shown to buckle spontaneously right after chemisorption of single adatoms. Unlike hydrogenation or fluorination, the oxidation process turns from the endothermic to exothermic for all types of the strain and depends on the direction of applied strains. Such properties will be useful in designing graphene devices utilizing functionalization as well as mechanical strains.     

NiS Hollow Spheres for High‐Performance Supercapacitors and Non‐Enzymatic Glucose Sensors

α‐NiS and β‐NiS hollow spheres were successfully synthesized via the Kirkendall effect under different hydrothermal conditions. The obtained α‐NiS and β‐NiS hollow spheres were evaluated as electrode materials for supercapacitors. Importantly, the α‐NiS hollow sphere electrode has a large specific capacitance (562.3 F g^?1 at 0.60 A g^?1) and good cycling property (maintaining about 97.5 % at 2.4 A g^?1 after 1000 cycles). Furthermore, the as‐prepared α‐NiS and β‐NiS hollow spheres were successfully applied to construct electrochemical glucose sensors. Especially, the α‐NiS hollow spheres exhibit a good sensitivity (155 μA mM^?1 cm^?2), low detection limit (0.125 μM ), and a wide linear range.     

Postsynthetic Functionalization of Three‐Dimensional Covalent Organic Frameworks for Selective Extraction of Lanthanide Ions

Chemical functionalization of covalent organic frameworks (COFs) is critical for tuning their properties and broadening their potential applications. However, the introduction of functional groups, especially to three‐dimensional (3D) COFs, still remains largely unexplored. Reported here is a general strategy for generating a 3D carboxy‐functionalized COF through postsynthetic modification of a hydroxy‐functionalized COF, and for the first time exploration of the 3D carboxy‐functionalized COF in the selective extraction of lanthanide ions. The obtained COF shows high crystallinity, good chemical stability, and large specific surface area. Furthermore, the carboxy‐functionalized COF displays high metal loading capacities together with excellent adsorption selectivity for Nd³⁺ over Sr²⁺ and Fe³⁺ as confirmed by the Langmuir adsorption isotherms and ideal adsorbed solution theory (IAST) calculations. This study not only provides a strategy for versatile functionalization of 3D COFs, but also opens a way to their use in environmentally related applications.     

One‐Step Double Covalent Functionalization of Reduced Graphene Oxide with Xanthates and Peroxides

Radical functionalization of reduced graphene oxide has been achieved by reaction with a xanthate in the presence of peroxide as a radical initiator. X‐ray photoelectron spectroscopy, bulk elemental analyses, and thermogravimetric analyses showed that the xanthate grafting is covalent and efficient. The synthesis and use of seven xanthates and three peroxides showed that the highest grafting yield is obtained when xanthate and peroxide are introduced in stoichiometric amounts. It also revealed that the peroxide used as radical initiator is grafted at the graphenic surface during the functionalization. The method presented in this contribution therefore allows bifunctionalized reduced graphene oxide samples to be easily obtained in one single step. This method leads to undamaged graphene sheets with higher dispersibility than the pristine sample.     

Single‐Step Exfoliation and Covalent Functionalization of MoS2 Nanosheets by an Organosulfur Reaction

A simple approach to exfoliate and functionalize MoS₂ in a single‐step is described, which combines the dispersion of MoS₂ in polybutadiene solution and ultrasonication processes. The great advantage of this process is that a colloidal stability of MoS₂ in nonpolar solvent is achieved by chemically bonding polybutadiene on the perimeter edge sites of MoS₂ sheets. In addition, elastomeric nanocomposite has been prepared with singular mechanical properties using functionalized MoS₂ as nanofiller in a polybutadiene matrix with a subsequent vulcanization reaction.     

Covalent Functionalization of Black Phosphorus with Conjugated Polymer for Information Storage

Major disadvantages of black phosphorus (BP) are its poor air‐stability and poor solubility in common organic solvents. The best way to solve this problem is to incorporate BP into a polymer backbone or a polymer matrix to form novel functional materials that can provide both challenges and opportunities for new innovation in optoelectronic and photonic applications. As a proof‐of concept application, we synthesized in situ the first highly soluble conjugated polymer‐covalently functionalized BP derivative (PDDF‐g‐BP) which was used to fabricate a resistive random access memory (RRAM) device with a configuration of Au/PDDF‐g‐BP/ITO. In contrast to PDDF without memory effect, PDDF‐g‐BP‐based device exhibits a nonvolatile rewritable memory performance, with a turn‐on and turn‐off voltages of +1.95 V and ?2.34 V, and an ON/OFF current ratio of 10⁴. The current through the device in both the ON and OFF states is still kept unchanged even at 200th switching cycle. The PDDF/BP blends show a very unstable memory performance with a very small ON/OFF current ratio.     

Highly Efficient and Reversible Covalent Patterning of Graphene: 2D‐Management of Chemical Information

Patterned graphene‐functionalization with a tunable degree of functionalization can tailor the properties of graphene. Here, we present a new reductive functionalization approach combined with lithography rendering patterned graphene‐functionalization easily accessible. Two types of covalent patterning of graphene were prepared and their structures were unambiguously characterized by statistical Raman spectroscopy together with scanning electron microscopy/energy‐dispersive X‐ray spectroscopy (SEM‐EDS). The reversible defunctionalization processes, as revealed by temperature‐dependent Raman spectroscopy, enable the possibility to accurately modulate the degree of functionalization by annealing. This allows for the management of chemical information through complete write/store/erase cycles. Based on our strategy, controllable and efficient patterning graphene‐functionalization is no longer a challenge and facilitates the development of graphene‐based devices.     

Ultrathin Cerium Orthovanadate Nanobelts for High‐Performance Flexible All‐Solid‐State Asymmetric Supercapacitors

Ultrathin CeVO₄ nanobelts were successfully synthesized by a hydrothermal method. The thickness of a single nanobelt is about 2.4 nm, which can effectively shorten the ion diffusion and fasten the charge pathway. More importantly, ultrathin CeVO₄ nanobelts and graphene are easily assembled as a flexible all‐solid‐state asymmetric device, which shows a highly flexible property and achieves a maximum energy density of 0.78 mW h cm^?3 and a high life cycle of >6000 cycles.     

Conductive Microporous Covalent Triazine‐Based Framework for High‐Performance Electrochemical Capacitive Energy Storage

Nitrogen‐enriched porous nanocarbon, graphene, and conductive polymers attract increasing attention for application in supercapacitors. However, electrode materials with a large specific surface area (SSA) and a high nitrogen doping concentration, which is needed for excellent supercapacitors, has not been achieved thus far. Herein, we developed a class of tetracyanoquinodimethane‐derived conductive microporous covalent triazine‐based frameworks (TCNQ‐CTFs) with both high nitrogen content (>8 %) and large SSA (>3600 m² g^?1). These CTFs exhibited excellent specific capacitances with the highest value exceeding 380 F g^?1, considerable energy density of 42.8 Wh kg^?1, and remarkable cycling stability without any capacitance degradation after 10 000 cycles. This class of CTFs should hold a great potential as high‐performance electrode material for electrochemical energy‐storage systems.     

A Reversible Redox Strategy for SWCNT‐Based Supercapacitors Using a High‐Performance Electrolyte

In order to achieve pesudocapacitive performance of single‐wall carbon nanotube (SWCNT) electrodes, a high‐efficient and reversible redox strategy utilizing a redox‐mediated electrolyte for SWCNT‐based supercapacitors is reported. In this novel redox‐mediated electrolyte, the single‐electrode specific capacitance of the supercapacitor is heightened four times, reaching C=162.66 F g^?1 at 1 A g^?1. The quick charge‐discharge ability of the supercapacitor is also enhanced, and the relaxation time is as low as 0.58 s. Furthermore, the supercapacitor shows an excellent cycling performance of 96.51 % retention after 4000 cycles. The remarkable results presented here illustrate that the redox strategy is a facile and straightforward approach to improve the performances of SWCNT electrodes.     

Designs,Synthesis, Characterization and Direct Electrochemistry of Zinc‐Porphyrin Bearing Pyrene Noncovalent Functionalized Graphene Oxide Sheet

We have designed and synthesis a new compound of zinc‐porphyrin bearing four pyrene groups (ZnP‐t‐P(py)₄) and prepared a new hybrid materials of ZnP‐t‐P(py)₄ with graphene oxide (GO) via non‐covalent interactions. The ZnP‐t‐P(py)₄, along with four pendant pyrene entities ZnP‐t‐P(py)₄, stacking on the (GO) surface due to π‐ π interactions, has been revealed by AFM measurements. FTIR, UV‐vis absorption confirm the non‐covalent functionalization of the GO. Raman spectral measurements revealed the electronic structure of the GO to be intact upon hybrid formation. In this donor‐acceptor nanohybrid, the fluorescence of photoexcited ZnP‐t‐P(py)₄ is effectively quenched by a possible electron‐transfer process. The fluorescence and photoelectrical response measurements also showed that this hybrid may act as an efficient photoelectric conversion material for optoelectronic applications.     

Non‐Covalent Functionalization of Carbon Nanotubes with Surfactants and Polymers

Carbon nanotubes (CNTs) possessing unique structure and properties are attractive building blocks for novel materials and devices of important practical interest. However, the insolubility or poor dispersibility of pristine CNTs in common solvents poses a serious obstacle to their further development. To effectively utilize CNTs as building blocks for nanotechnology, CNTs have been covalently and noncovalently functionalized in a number of ways to render them soluble in aqueous or organic solutions. Here, we review recent progress and advances that have been made on dispersion of carbon nanotubes in aqueous and organic media by non‐covalent functionalization with surfactants and polymers.     

Radical Covalent Organic Frameworks: A General Strategy to Immobilize Open‐Accessible Polyradicals for High‐Performance Capacitive Energy Storage

Ordered π‐columns and open nanochannels found in covalent organic frameworks (COFs) could render them able to store electric energy. However, the synthetic difficulty in achieving redox‐active skeletons has thus far restricted their potential for energy storage. A general strategy is presented for converting a conventional COF into an outstanding platform for energy storage through post‐synthetic functionalization with organic radicals. The radical frameworks with openly accessible polyradicals immobilized on the pore walls undergo rapid and reversible redox reactions, leading to capacitive energy storage with high capacitance, high‐rate kinetics, and robust cycle stability. The results suggest that channel‐wall functional engineering with redox‐active species will be a facile and versatile strategy to explore COFs for energy storage.     

Non‐covalent dimers of the lysine containing protonated peptide ions in gaseous state: electrospray ionization mass spectrometric study

Study of the non‐covalent molecular complexes in gas phase by electrospray ionization mass spectrometry (ESI‐MS) represents a promising strategy to probe the intrinsic nature of these complexes. ESI‐MS investigation of a series of synthetic octapeptides containing six alanine and two lysine residues differing only by their positions showed the formation of non‐covalent dimers, which were preserved in the gas phase. Unlike the monomers, the dimers were found to show only singly protonated state. The decrease in the solvent polarity from water to alcohol showed enhanced propensity of formation of the dimer indicating that the electrostatic interaction plays a crucial role to stabilize the dimer. Selective functionalization studies showed that ε‐NH₂ of lysine and C‐terminal amide (? CONH₂) facilitate the dimerization through intermolecular hydrogen bonding network. Copyright © 2010 John Wiley & Sons, Ltd.     

Functionalization of multi-walled carbon nanotubes and their application for selective isolation of acidic proteins

A micro-column packed with PDDA-wrapped MWNTs in sequential injection system facilitates selective sorption of acidic protein species. Proteins adsorbed onto the PDDA-MWNT composites are afterwards collected by elution with a citrate buffer as stripping reagent. With a sample loading volume of 2.0 mL and an eluent volume of 200 microL, a retention efficiency of 100% and a recovery of 90% are achieved for BSA in the range 6-120 microg, resulting in an enrichment factor of 14. A sampling frequency of 15 h(-1) is achieved, along with a precision of 4.5% at 25 microg x mL(-1) BSA. The practical applicability of this system is demonstrated by processing human whole blood for successive isolation of acidic proteins.     

High‐Throughput Kinetic Analysis for Target‐Directed Covalent Ligand Discovery

Cysteine‐reactive small molecules are used as chemical probes of biological systems and as medicines. Identifying high‐quality covalent ligands requires comprehensive kinetic analysis to distinguish selective binders from pan‐reactive compounds. Quantitative irreversible tethering (qIT), a general method for screening cysteine‐reactive small molecules based upon the maximization of kinetic selectivity, is described. This method was applied prospectively to discover covalent fragments that target the clinically important cell cycle regulator Cdk2. Crystal structures of the inhibitor complexes validate the approach and guide further optimization. The power of this technique is highlighted by the identification of a Cdk2‐selective allosteric (type IV) kinase inhibitor whose novel mode‐of‐action could be exploited therapeutically.     

Controlled Chemistry Approach to the Oxo‐Functionalization of Graphene

Graphene is the best‐studied 2D material available. However, its production is still challenging and the quality depends on the preparation procedure. Now, more than a decade after the outstanding experiments conducted on graphene, the most successful wet‐chemical approach to graphene and functionalized graphene is based on the oxidation of graphite. Graphene oxide has been known for more than a century; however, the structure bears variable large amounts of lattice defects that render the development of a controlled chemistry impossible. The controlled oxo‐functionalization of graphene avoids the formation of defects within the σ‐framework of carbon atoms, making the synthesis of specific molecular architectures possible. The scope of this review is to introduce the field of oxo‐functionalizing graphene. In particular, the differences between GO and oxo‐functionalized graphene are described in detail. Moreover analytical methods that allow determining lattice defects and functional groups are introduced followed by summarizing the current state of controlled oxo‐functionalization of graphene.     

无模板法合成具有分级结构的多孔氧化镍及其电容性能研究(英文)

应用无模板水热法制备了由超薄氧化镍纳米片组装而成的具有分级结构的多孔氧化镍,SEM观察表明经煅烧氧化镍仍保持花状球形结构.电化学测试结果表明,扫速为20 mV.s-1时,其比电容值435 F.g-1,循环1000周期之后,电容值基本没有衰减;电流密度为10 A.g-1时,其比电容值为367 F.g-1.该材料是一种有应用价值的超级电容器材料.