Effect of functional group (fluorine) of aromatic thiols on electron transfer at the molecule-metal interface

Electron transfer at the molecule-metal interface of self-assembled monolayers of 1,1';4',1'-terphenyl-4'-thiol (BBB) and its partially fluorinated counterpart (BFF: p-thiophenyl-nonafluorobiphenyl) on Au(111) is investigated by core-hole clock spectroscopy. Ultrafast electron transfer at the BBB/Au(111) interface in the low-femtosecond regime (on the same time scale as the C 1s core-hole lifetime, approximately 6 fs) was observed. In contrast, for BFF/Au(111), the interface electron transfer was forbidden during the core-hole decay. This strongly suggests that fluorination of phenyl rings significantly enhances the localization of the excited electrons in the LUMO.     

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.     

Noise conversion from pump to the passively mode-locked fiber lasers at 1.5 μm

We characterize the noise conversion from the pump relative intensity noise (RIN) to the RIN and phase noise of passively mode-locked lasers at 1.5 μm. Two mode locking mechanisms, nonlinear polarization rotation (NPR) and semiconductor saturable absorber mirror (SESAM), are compared for noise conversion for the first time. It is found that the RIN and the phase noise of both types of lasers are dominated by the noise converted from the pump RIN and thus, can be predicted with the measured pump RIN and noise conversion ratios. The SESAM laser is found to show an excess noise conversion from the laser RIN to the laser phase noise due to the slow saturable absorber effect.     

Regioselective hydroformylation of allylic alcohols

A highly regioselective hydroformylation of allylic alcohols is reported toward the synthesis of β-hydroxy-acid and aldehyde products. The selectivity is achieved through the use of a ligand that reversibly binds to alcohols in situ, allowing for a directed hydroformylation to occur. The application to trisubstituted olefins was also demonstrated, which yields a single diastereomer product consistent with a stereospecific addition of CO and hydrogen.     

Time- and wavelength-interleaved optical pulse train generation based on dispersion spreading and sectional compression

A method to generate time- and wavelength-interleaved optical pulse trains based on dispersion spreading and sectional compression is proposed and demonstrated. A 4×2 GHz time- and wavelength-interleaved pulse train is generated from an input 2 GHz mode-locked pulse train. The advantages of the proposed scheme are its simplicity and robustness, since no microwave component or multiwavelength laser source is required. In addition, we demonstrate supercontinuum generation of an ultraflat 18 nm bandwidth spectrum with less than 0.5 dB fluctuation over the 3.2 nm central bandwidth.     

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.