Supercapacitive energy storage based on ion‐conducting channels in hydrophilized organic network

Conventional electrode materials for supercapacitors are based on nanoscaled structures with large surface areas or porosities. This work presents a new electrode material, the so‐called hydrophilized polymer network. The network has two unique features: 1) it allows for high capacitance (up to 400 F/g) energy storage in a simple film configuration without the need of high‐surface‐area nanostructures; 2) it is unstable in water, but becomes extremely stable in electrolyte with high ionic strength. The above features are related to the hydrophilizing groups in the network which not only generate hydrated ionic conduction channels, but also enable the cross‐linking of the network in electrolyte. Because of its practical advantages such as easy preparation and intrinsic stability in electrolyte, the hydrophilized network may provide a new route to high‐performance supercapacitive energy storage. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1234–1240, 2011     

Identifying DNA motifs based on match and mismatch alignment information

The conventional way of identifying DNA motifs, solely based on match alignment information, is susceptible to a high number of spurious sites. A novel scoring system has been introduced by taking both match and mismatch alignment information into account. The mismatch alignment information is useful to remove spurious sites encountered in DNA motif searching. As an example, a correct TATA box site in Homo sapiens $H4/g$ gene has successfully been identified based on match and mismatch alignment information.     

Synthesis of sterically congested 1,3,4-oxadiazole derivatives from aromatic carboxylic acids, <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dicyclohexylcarbodiimide and (<Emphasis Type="Italic">N</Emphasis>-isocyanimino)triphenylphosphorane

Reactions of (N-isocyanimino)triphenylphosphorane with N,N-dicyclohexylcarbodiimide in the presence of aromatic (or heteroaromatic) carboxylic acids proceed smoothly at room temperature and in neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in high yields. The reaction proceeds smoothly and cleanly under mild conditions, and no side reactions were observed.     

Polymer brushes on graphene

A critical bottleneck for the widespread use of single layer graphene is the absence of a facile method of chemical modification which does not diminish the outstanding properties of the two-dimensional sp(2) network. Here, we report on the direct chemical modification of graphene by photopolymerization with styrene. We demonstrate that photopolymerization occurs at existing defect sites and that there is no detectable disruption of the basal plane conjugation of graphene. This method thus offers a route to define graphene functionality without degrading its electronic properties. Furthermore, we show that photopolymerization with styrene results in self-organized intercalative growth and delamination of few layer graphene. Under these reaction conditions, we find that a range of other vinyl monomers exhibits no reactivity with graphene. However, we demonstrate an alternative route by which the surface reactivity can be precisely tuned, and these monomers can be locally grafted via electron-beam-induced carbon deposition on the graphene surface.     

High-yield synthesis of few-layer graphene flakes through electrochemical expansion of graphite in propylene carbonate electrolyte

High-yield production of few-layer graphene flakes from graphite is important for the scalable synthesis and industrial application of graphene. However, high-yield exfoliation of graphite to form graphene sheets without using any oxidation process or super-strong acid is challenging. Here we demonstrate a solution route inspired by the lithium rechargeable battery for the high-yield (>70%) exfoliation of graphite into highly conductive few-layer graphene flakes (average thickness <5 layers). A negative graphite electrode can be electrochemically charged and expanded in an electrolyte of Li salts and organic solvents under high current density and exfoliated efficiently into few-layer graphene sheets with the aid of sonication. The dispersible graphene can be ink-brushed to form highly conformal coatings of conductive films (15 ohm/square at a graphene loading of <1 mg/cm(2)) on commercial paper.     

Arsenic(II) sulfide quantum dots prepared by a wet process from its bulk

Arsenic(II) sulfide nanocrystals were fabricated by a wet process from its bulk through cluster-mediate transformation. The bulk arsenic(II) sulfide can be easily dissolved in ethylenediamine to form a solution-like cluster (As4S4-NH2C2H4NH2)). The cluster can be transformed to nanocrystals assisted by consumption of ethylenediamine in protic polar solvents with mild thermal treatment. The nanocrystals show size-dependent fluorescence ranging from UV to the blue, two photon fluorescence as well as cytotoxic effects on cancer cells.     

Solution-gated epitaxial graphene as pH sensor

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.     

Studies of chemisorbed tetracene on si(111)-7x7

The chemisorption of tetracene on the Si(111)-7x7 surface was studied using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. On the basis of the STM results and dimension analysis, two types of binding configurations were proposed. One of the configurations involves the di-sigma reaction between two C atoms of an inner ring with an adatom-rest atom pair on the substrate to give rise to an unsymmetrical butterfly structure. Tetracene in another configuration possesses four C-Si bonds that are formed via di-sigma reactions between the C atoms at the terminal rings with two center adatom-rest atom pairs within one-half of the surface unit cell. Besides, two other binding modes were proposed based on the dimension compatibility between the tetracene C and the substrate Si dangling bonds even though their identifications through the STM images are nonexclusive. Structural modeling and adsorption energies calculations were carried out using the DFT method. Factors affecting the relative thermodynamic stabilities based on the calculation results and the relative populations of tetracene in the different binding configurations as observed experimentally were discussed.     

Reversible switching of substrate activity of poly-N-isopropylacrylamide peptide conjugates

The activity of smart polymer peptide conjugates towards chymotrypsin catalyzed hydrolysis was reversibly switched on and off using temperature as the trigger.