Generation and detection of the radical cation and the dication derived from 4,9‐diethyl[1,4]dihydrodithiino[5,6‐f]benzotrithiole and its 5‐oxide

4,9‐Diethyl[1,4]dihydrodithiino[5,6‐f]benzotrithiole (DTBT) gave a radical cation, DTBT(•+), and a dication, DTBT(2+), on treatment with a single‐electron oxidizing reagent. Both compounds showed an ESR signal, whereas the dication, generated by this procedure, was silent for ¹H NMR. Hydrolysis of DTBT(2+) gave DTBT 1‐oxide (DTBT 1‐O) and 2‐oxide (DTBT 2‐O) together with DTBT and a mixture of several dioxides. A singlet‐state dication, DTBT(2+)‐S, which was generated upon treatment of DTBT 5‐oxide (DTBT 5‐O) with concentrated D₂SO₄, was detected by ¹H and ¹³C NMR. After 20 h, the NMR signals disappeared while the solution was active for ESR. The results suggest that (i) a species generated from DTBT by oxidation with the single‐electron oxidizing reagent is a triplet‐state dication, DTBT(2+)‐T, and (ii) DTBT(2+)‐S, initially generated, gradually isomerizes to DTBT(2+)‐T in the solution, and DTBT(2+)‐T forms a partial spin pair. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:394–401, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20445     

Synthesis and radical polymerization of methacrylate endowed with bicyclobis(γ‐butyrolactone) moiety through methylene linker

A series of methacrylates bearing bicyclobis(γ‐butyrolactone) (BBL) moiety were synthesized and radically polymerized to afford the corresponding poly(methacrylate)s bearing BBL moiety in the side chain, with expecting that the high polarity and rigidity of BBL would be inherited by the polymers. The resulting polymers were soluble in polar aprotic solvents such as dimethyl sulfoxide and N,N‐dimethylformamide because of the high polarity of the BBL moiety. The glass transition temperatures (T_g) of the polymers depended on the length of methylene linker that tethered the methacrylate and BBL moieties, making the use of shorter linkers lead to higher T_gs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2462–2468     

Microfluidic Study on the Two-Phase Fluid Flow in Porous Media During Repetitive Drainage-Imbibition Cycles and Implications to the CAES Operation

Transport in Porous Media - Compressed air energy storage (CAES) technology has been re-emerging as a viable energy storage option to address challenges coming from the mismatch between renewable...     

Conformational analysis of N-aryl-N-(2-azulenyl)acetamides

Aromatic amides bearing 2-azulenyl group on the amide nitrogen were synthesized and their structures were investigated. The π-electron density of the N-aryl group was found to influence the cis-trans conformational preferences of these compounds in solution. X-ray crystallography revealed that the plane of the 2-azulenyl ring has a strong tendency to lie coplanar with the amide plane when the azulene group is located on the same side as the amide oxygen atom.     

Step annealing effects on the structural and optical properties of InAs quantum dots grown on GaAs

The effects of multi-step rapid thermal annealing (RTA) for the self-assembled InAs quantum dots (QDs), which were grown by a molecular beam epitaxy (MBE), were investigated through photoluminescence (PL) and transmission electron microscopy (TEM). Postgrowth multi-step RTA was used to modify the structural and optical properties of the self-assembled InAs QDs. Postgrowth multi-step RTAs are as follows: one step (20 s at 750 °C); two step (20 s at 650 °C, 20 s at 750 °C); three step (30 s at 450 °C, 20 s at 650 °C, 20 s at 750 °C). It is found that significant narrowing of the luminescence linewidth (from 132 to 31 meV) from the InAs QDs occurs together with about 150 meV blueshift by two-step annealing, compared to as-grown InAs QDs. Observation of transmission electron microscopy (TEM) shows the existence of the dots under one- and two-step annealing but the disappearance of the dots by three-step annealing. Comparing with the samples under only one-step annealing, we demonstrate a significant enhancement of the interdiffusion in the dot layer under multi-step annealing.     

Chemodosimetric Hg2+-selective signaling by mercuration of dichlorofluorescein derivatives

The chemodosimetric behavior of dichlorofluorescein derivatives toward Hg(2+) ions was investigated. Simple chemodosimetric systems showed selective and efficient signaling behaviors toward micromolar concentrations of Hg(2+) ions over other common interfering metal ions in an aqueous environment. The signaling mechanism is selective mercuration of the 4',5'-position of the xanthene moiety, which results in efficient chromogenic and fluorogenic signaling of Hg(2+) ions in aqueous environment.     

Synthesis of new N-arylpyrimidin-2-amine derivatives using a palladium catalyst

New N-aryl-4-(pyridin-3-yl)pyrimidin-2-amine derivatives were synthesized from the corresponding amines, applying optimized Buchwald-Hartwig amination conditions using dichlorobis(triphenylphosphine)Pd(II), xantphos and sodium tertbutoxide in refluxing toluene under a nitrogen atmosphere. The target N-aryl derivatives were obtained in moderate to good yields ranging from 27% to 82%. The procedure described could be widely employed for the preparation of new heterocyclic compounds. The structures of the new compounds were confirmed by FT-NMR, FT-IR and elemental analysis.     

Open micro-fluidic system for atomic force microscopy-guided in situ electrochemical probing of a single cell

Ultra-sharp nano-probes and customized atomic force microscopy (AFM) have previously been developed in our laboratory for in situ sub-cellular probing of electrochemical phenomena in living plant cells during their photosynthesis. However, this AFM-based electrochemical probing still has numerous engineering challenges such as immobilization of the live cells, compatibility of the immobilization procedure with AFM manipulation of the probe, maintenance of biological activity of the cells for an extended time while performing the measurements, and minimization of electrochemical noise. Thus, we have developed an open micro-fluidic channel system (OMFC) in which individual cells can be immobilized in micro-traps by capillary flow. This system affords easy AFM access and allows for maintenance of the cells in a well-defined chemical environment, which sustains their biological activity. The use of micro-channels for making the electrochemical measurements significantly reduces parasitic electrical capacitances and allows for current detection in the sub-pico-ampere range at high signal bandwidths. The OMFC was further studied using simulation packages for optimal design conditions. This system was successfully used to measure light-dependent oxidation currents of a few pico-amperes from the green alga Chlamydomonas reinhardtii.