Compact optical delay line for long-range scanning

We proposed and demonstrated an optical delay line composed of all reflective components for long-range scanning without walk-off problem. The optical delay line consists of a retro-reflector, an inclined reflection mirror and a scanning mirror. The size of the optical delay line is within 2 cm × 2 cm and the scanning range can reach 2.9 mm when the beam is incident at the pivot of the scanning mirror and the vibration angle of the scanning mirror is 9.6°. The scanning range can be further increased when the pivot of the scanning mirror is laterally deviated from the incident beam. The optical delay line possesses the advantages that it is compact, easy to fabricate and can perform rapid scanning in large scanning range without walk-off problem. The optical delay line was demonstrated with a low-coherence reflectometer where the scanning rate was 400 Hz. A higher scanning rate can be achieved when a scanning component with higher scanning rate is applied.     

Mechanochemical synthesis of poly(2,5-dimethoxy aniline) nanobelts and its electrochemical performance in hybrid supercapacitors

A solvent-free mechanochemical route for the preparation of poly(2,5-dimethoxyaniline) hydrochloride nanostructures is developed and reported in the article. High conductivity, good crystallinity, and nanostructured morphology are observed for the prepared polymer. This polymeric powder is utilized as a cathode material in hybrid supercapacitor and its electrochemical performance is evaluated and discussed in this short report. The maximum specific capacitance of the poly(2,5-dimethoxyaniline) hydrochloride/activated carbon hybrid supercapacitor is found to be 125 F g⁻¹ at 1 mA cm⁻² current density. The cell delivers a specific energy as high as 50 Wh kg⁻¹ at a specific power of 97 W kg⁻¹ and also exhibits an excellent cycle performance with more than 99% coulombic efficiency and the maintenance of 85% of its initial capacitance after 1,000 cycles.     

Facile synthesis of 5,10,15-hexaaryl truxenes: structure and properties

A new synthesis of 5,10,15-hexaaryltruxene derivatives has been developed. Experimental observations and theoretical calculations confirmed that the presence of aryl substituents on the sp(3)-hybridized bridge carbon atoms had an effect on the photophysical properties of the truxene core. Interestingly, the cage compound 11 possessing a distorted truxene core was verified by X-ray diffraction analysis; the influence of the peripheral aryl substituents on the photophysical properties of the truxene core was diminished because of its molecular rigidity.     

Effect of nucleobase sequence on the proton-transfer reaction and stability of the guanine-cytosine base pair radical anion

The formation of base pair radical anions is closely related to many fascinating research fields in biology and chemistry such as radiation damage to DNA and electron transport in DNA. However, the relevant knowledge so far mainly comes from studies on isolated base pair radical anions, and their behavior in the DNA environment is less understood. In this study, we focus on how the nucleobase sequence affects the properties of the guanine-cytosine (GC) base pair radical anion. The energetic barrier and reaction energy for the proton transfer along the N(1)(G)-H···N(3)(C) hydrogen bond and the stability of GC˙(-) (i.e., electron affinity of GC) embedded in different sequences of base-pair trimer were evaluated using density functional theory. The computational results demonstrated that the presence of neighboring base pairs has an important influence on the behavior of GC˙(-) in the gas phase. The excess electron was found to be localized on the embedded GC and the charge leakage to neighboring base pairs was very minor in all of the investigated sequences. Accordingly, the sequence behavior of the proton-transfer reaction and the stability of GC˙(-) is chiefly governed by electrostatic interactions with adjacent base pairs. However, the effect of base stacking, due to its electrostatic nature, is severely screened upon hydration, and thus, the sequence dependence of the properties of GC˙(-) in aqueous environment becomes relatively weak and less than that observed in the gas phase. The effect of geometry relaxation associated with neighboring base pairs as well as the possibility of proton transfer along the N(2)(G)-H···O(2)(C) channel have also been investigated. The implications of the present findings to the electron transport and radiation damage of DNA are discussed.     

Direct synthesis of bifunctional periodic mesoporous benzene-silicas functionalized with a high loading of carboxylic acid groups

Well-ordered periodic mesoporous benzene-silicas functionalized with a high loading of pendant carboxylic acid groups (up to 60 mol% based on silica) have been successfully synthesized via co-condensation of 1,4-bis(triethoxysilyl)benzene and carboxyethylsilanetriol sodium salt using Pluronic P123 as a template and KCl as an additive.     

IR Study of Monomer–Dimer Self-association of 2,2-Dimethyl-3-ethyl-3-pentanol in n-Octane: Determination of the Molar Absorptivities of Monomer and Dimer Bands, and Dimerization Constants Using Novel Equations

The monomer–dimer self-association equilibrium of 2,2-dimethyl-3-ethyl-3-pentanol in n-octane has been studied by IR spectroscopy at four temperatures (288, 298, 308, and 318 K). The solute was chosen to restrict the self-association between solute molecules to dimerization only, owing to steric hindrance of the bulky chains in the vicinity of the OH group. Two linear equations have been derived for the treatment of the experimental data. One of these equations was used to treat the data of the concentration dependent integrated absorbance of the monomer bands for each temperature to obtain the monomer molar absorptivity, ε _m, and dimerization constant, K. The other equation was used to treat the data of concentration-dependent dimer bands to obtain the dimer molar absorptivity, ε _d, and K. Thus, the dimerization constant was determined by two methods. Since the same thermodynamic quantity K is obtained from either the monomer bands or the dimer bands, the difference between them at a given temperature can serve as an assessment of the quality of the experiment. The standard enthalpy and entropy of dimerization were also obtained from a van’t Hoff plot.     

Molecular dynamic-secondary ion mass spectrometry (D-SIMS) ionized by co-sputtering with C60+ and Ar+

Dynamic secondary ion mass spectrometry (D-SIMS) analysis of poly(ethylene terephthalate) (PET) and poly(methyl methacrylate) (PMMA) was conducted using a quadrupole mass analyzer with various combinations of continuous C(60)(+) and Ar(+) ion sputtering. Individually, the Ar(+) beam failed to generate fragments above m/z 200, and the C(60)(+) beam generated molecular fragments of m/z ~1000. By combining the two beams, the auxiliary Ar(+) beam, which is proposed to suppress carbon deposition due to C(60)(+) bombardment and/or remove graphitized polymer, the sputtering range of the C(60)(+) beam is extended. Another advantage of this technique is that the high sputtering rate and associated high molecular ion intensity of the C(60)(+) beam generate adequate high-mass fragments that mask the damage from the Ar(+) beam. As a result, fragments at m/z ~900 can be clearly observed. As a depth-profiling tool, the single C(60)(+) beam cannot reach a steady state for either PET or PMMA at high ion fluence, and the intensity of the molecular fragments produced by the beam decreases with increasing C(60)(+) fluence. As a result, the single C(60)(+) beam is suitable for profiling surface layers with limited thickness. With C(60)(+)-Ar(+) co-sputtering, although the initial drop in intensity is more significant than with single C(60)(+) ionization because of the damage introduced by the auxiliary Ar(+), the intensity levels indicate that a more steady-state process can be achieved. In addition, the secondary ion intensity at high fluence is higher with co-sputtering. As a result, the sputtered depth is enhanced with co-sputtering and the technique is suitable for profiling thick layers. Furthermore, co-sputtering yields a smoother surface than single C(60)(+) sputtering.     

Synthesis and characterization of a new chromophor with acid/base-sensitive fluorescence emission

A new two-photon absorption compound,2-{4-((dicyanomethylidene-5,5-dimethylcyclohexl)vinyl]phenyl}imidazo[4,5- f][l,10]phenanthroline(DDVPIP),was synthesized and characterized.The one-photon excited fluorescence(OPEF) and two-photon excited fluorescence(TPEF) of DDVPIP are sensitive to the acid/base of the solution,which arc enhanced in basic solution but weakened in acidic solution.Charge-transfer(CT) states of DDVPIP were calculated through theory methods to explain its acid/ base-sensitive fluorescent properties.     

The influence of different fabrication processes on characteristics of excess Bi2O3-doped 0.95 (Na0.5Bi0.5)TiO3–0.05 BaTiO3 ceramics

In this study, we will develop the influences of the excess x wt% (x=0, 1, 2, and 3) Bi₂O₃-doped and the different fabricating process on the sintering and dielectric characteristics of 0.95 (Na_0.5Bi_0.5)TiO₃–0.05 BaTiO₃ ferroelectric ceramics with the aid of SEM and X-ray diffraction patterns, and dielectric–temperature curves. The 0.95 (Na_0.5Bi_0.5)TiO₃–0.05 BaTiO₃+x wt% Bi₂O₃ ceramics are fabricated by two different processes. The first process is that (Na_0.5Bi_0.5)TiO₃ composition is calcined at 850 °C and BaTiO₃ composition is calcined at 1100 °C, then the calcined (Na_0.5Bi_0.5)TiO₃ and BaTiO₃ powders are mixed in according to 0.95 (Na_0.5Bi_0.5)TiO₃–0.05 BaTiO₃+x wt% Bi₂O₃ compositions. The second process is that the raw materials are mixed in accordance to the 0.95 (Na_0.5Bi_0.5)TiO₃–0.05 BaTiO₃+x wt% Bi₂O₃ compositions and then calcining at 900 °C. The sintering process is carried out in air for 2 h from 1120 to 1240 °C. After sintering, the effects of process parameters on the dielectric characteristics will be developed by the dielectric–temperature curves. Dielectric–temperature properties are also investigated at the temperatures of 30–350 °C and at the frequencies of 10 kHz–1 MHz.