Dimensional dependence of electronic structure of fullerene polymers

Fullerene polymers made of C(60) are systematically investigated by means of a first-principles pseudopotential approach within the local density approximation of the density functional theory. We assume 10 different structures of fullerene polymers. The first three are C(60) polymer networks cross-linked by [2+2] cycloadditional four-membered rings, and the other seven are composed of peanut-shaped fused C(60) polymer chains cross-linked by either seven-membered rings or eight-membered rings. Owing to the overlap of wave functions as well as the hybrid networks of sp(2)-like (3-fold coordinated) and sp(3)-like (4-fold coordinated) carbon atoms, the electronic structure is considerably different from each other. We find that the resulting electronic structure is either semiconductor or semimetal depending on the spatial dimensionality of materials.     

Designing a Polymer Blend with Phase Separation Tunable by Visible Light for Computer‐Assisted Irradiation Experiments

Summary: A mixture of poly(vinyl methyl ether) (PVME) and a polystyrene derivative bearing cinnamate groups (PSC) was chemically designed so that its phase separation can be tunable by visible light for computer‐assisted irradiation (CAI) experiments. This PSC/PVME blend exhibits a lower critical solution temperature (LCST) and undergoes phase separation upon irradiation with 405 nm visible light. The phase separation was induced by photodimerization of the cinnamate moieties in the presence of 5‐nitroacenaphthene used as a photosensitizer. It was found that for visible light with high intensity, phase separation process was almost frozen by photodimerization of the cinnamate groups which act as a photo‐cross‐linker for the PSC component. It is demonstrated in this work that by using this PSC/PVME blend, phase separation restricted to the micrometer scales can be induced and manipulated by irradiation using a computer‐controlled digital projector. These preliminary results open a new route for spatio‐temporal manipulation of phase separation in photo‐reactive polymer blends.

Computer‐assisted irradiation method for a polymer blend with phase separation drivable by visible light.     

Selective determination of dopamine in the presence of high concentration of ascorbic acid using nano-Au self-assembly glassy carbon electrode

The cysteamine (CA) was bound onto surface of the pretreated glassy carbon electrode (GC) with cyclic voltammetry (CV). Gold nanoparticles were self-assembled to the electrode binding with cysteamine via strong AuS covalent bond to fabricate the nano-Au self-assembled modified electrode (nano-Au/CA/GC). The modified electrode was characterized with cyclic voltammetric and ac impedance methods. The electrochemical behavior of dopamine (DA) on the modified electrode was investigated with cyclic voltammetry and differential pulse voltammetry (DPV). A well-defined redox peaks of DA on the nano-Au/CA/GC electrode were obtained at E_pa = 0.175 V and E_pc = 0.146 V (vs. SCE), respectively. The peak current of DA is linear with the concentration of DA in the range of 1.0 × 10⁻⁸ mol L⁻¹ to 2.5 × 10⁻⁵ mol L⁻¹, with the correlation coefficient of 0.998. The detection limit is 4.0 × 10⁻⁹ mol L⁻¹ (S/N = 3). The modified electrode exhibited an excellent reproducibility, sensibility and stability for determination of DA in the presence of high concentration AA, and can be applied to determinate dopamine injection, with satisfied result.     

A lattice Monte Carlo simulation of the FePt alloy using a first-principles renormalized four-body interaction

Although a lattice Monte Carlo method provides an effective, simple, and fast way to study thermodynamic properties of substitutional alloys, it cannot treat by itself the off-lattice effects, such as thermal vibrations and local distortions. Therefore, even if the interaction among atoms at lattice points is calculated accurately by means of first-principles calculations, the lattice Monte Carlo simulation overestimates the order-disorder phase transition temperature. In this paper, we treat this problem in the investigation of the FePt alloy, which has recently attracted considerable interest in its magnetic properties. We apply a simple version of the potential renormalization theory to determine the interaction among atoms, including partly the off-lattice effects by means of first-principles calculations. Then, we use the interaction to perform a lattice Monte Carlo simulation of the FePt alloy on a fcc lattice. From the results, we find that the transition temperature obtained after the present renormalization procedure becomes closer to the experimental value.     

Effects of extremely low frequency magnetic field on the antioxidant defense system in mouse brain: a chemiluminescence study

Among the putative mechanisms, by which extremely low frequency (ELF) magnetic field (MF) may affect biological systems is that of increasing free radical life span in organisms. To test this hypothesis, we investigated whether ELF (60 Hz) MF can modulate antioxidant system in mouse brain by detecting chemiluminescence and measuring superoxide dismutase (SOD) activity in homogenates of the organ. Compared to sham exposed control group, lucigenin-initiated chemiluminescence in exposed group was not significantly increased. However, lucigenin-amplified t-butyl hydroperoxide (TBHP)-initiated brain homogenates chemiluminescence, was significantly increased in mouse exposed to 60 Hz, MF, 12 G for 3 h compared to sham exposed group. We also measured SOD activity, that plays a critical role of the antioxidant defensive system in brain. In the group exposed to 60 Hz, MF, 12 G for 3 h, brain SOD activity was significantly increased. These results suggest that 60 Hz, MF could deteriorate antioxidant defensive system by reactive oxygen species (ROS), other than superoxide radicals. Further studies are needed to identify the kind of ROS generated by the exposure to 60 Hz, MF and elucidate how MF can affect biological system in connection with oxidative stress.     

Particle Display: A Quantitative Screening Method for Generating High‐Affinity Aptamers

We report an aptamer discovery technology that reproducibly yields higher affinity aptamers in fewer rounds compared to conventional selection. Our method (termed particle display) transforms libraries of solution‐phase aptamers into “aptamer particles”, each displaying many copies of a single sequence on its surface. We then use fluorescence‐activated cell sorting (FACS) to individually measure the relative affinities of >10⁸ aptamer particles and sort them in a high‐throughput manner. Through mathematical analysis, we identified experimental parameters that enable optimal screening, and demonstrate enrichment performance that exceeds the theoretical maximum achievable with conventional selection by many orders of magnitude. We used particle display to obtain high‐affinity DNA aptamers for four different protein targets in three rounds, including proteins for which previous DNA aptamer selection efforts have been unsuccessful. We believe particle display offers an extraordinarily efficient mechanism for generating high‐quality aptamers in a rapid and economic manner, towards accelerated exploration of the human proteome.     

Accurate Zygote‐Specific Discrimination of Single‐Nucleotide Polymorphisms Using Microfluidic Electrochemical DNA Melting Curves

We report the first electrochemical system for the detection of single‐nucleotide polymorphisms (SNPs) that can accurately discriminate homozygous and heterozygous genotypes using microfluidics technology. To achieve this, our system performs real‐time melting‐curve analysis of surface‐immobilized hybridization probes. As an example, we used our sensor to analyze two SNPs in the apolipoprotein E (ApoE) gene, where homozygous and heterozygous mutations greatly affect the risk of late‐onset Alzheimer’s disease. Using probes specific for each SNP, we simultaneously acquired melting curves for probe–target duplexes at two different loci and thereby accurately distinguish all six possible ApoE allele combinations. Since the design of our device and probes can be readily adapted for targeting other loci, we believe that our method offers a modular platform for the diagnosis of SNP‐based diseases and personalized medicine.     

Realizing green phosphorescent light-emitting materials from rhenium(i) pyrazolato diimine complexes

Two neutral pyrazolato diimine rhenium(I) carbonyl complexes with formula [Re(CO)(3)(N-N)(btpz)] where N-N = 2,2'-bipyridine (1) and 1,10-phenanathroline (2), and btpz = 3,5-bis(trifluoromethyl) pyrazolate, were synthesized and characterized by elemental analysis, routine spectroscopic methods, and single-crystal X-ray diffraction study. Ground and excited state properties of these complexes were investigated by steady-state and time-resolved spectroscopies. Complexes 1 and 2 show photoluminescent emission in both solution and solid-state at room temperature, arising from metal to ligand charge-transfer (MLCT) transition with strong overlapping of intraligand pi --> pi transitions. The long-lived excited state lifetimes of complexes 1 and 2, which are on the order of microseconds, indicate the presence of phosphorescent emission. As these complexes hold the potential to serve as phosphors for organic light-emitting diodes (OLEDs), their electroluminescent performances were evaluated by employing them as dopants of various electron transport layer (ETL) or hole transport layer (HTL) hosts. For complex 1, a green electrophosphorescence emission centered at lambda(max) = 530 nm was observed at low turn-on voltage ( approximately 6 V) with luminous power efficiency of 0.72 lm/W, external quantum efficiency of 0.82%, and luminance of 2300 cd/m(2) at a current density of 100 mA/cm(2).