Successful demonstration of an efficient I(-)/(SeCN)2 redox mediator for dye-sensitized solar cells

A new I(-)/(SeCN)(2) redox mediator has favorable properties for dye-sensitized solar cells (DSCs) such as less visible light absorption, higher ionic conductivity, and downward shift of redox potential than I(-)/I(3)(-). It was then applied for DSCs towards increasing energy conversion efficiency, giving a new potential for improving performance.     

The paradox of an insulating contact between a chemisorbed molecule and a wide band gap semiconductor surface

Controlling the intrinsic optical and electronic properties of a single molecule adsorbed on a surface requires electronic decoupling of some molecular orbitals from the surface states. Scanning tunneling microscopy experiments and density functional theory calculations are used to study a perylene molecule derivative (DHH-PTCDI), adsorbed on the clean 3 × 3 reconstructed wide band gap silicon carbide surface (SiC(0001)-3 × 3). We find that the LUMO of the adsorbed molecule is invisible in I(V) spectra due to the absence of any surface or bulk states and that the HOMO has a very low saturation current in I(z) spectra. These results present a paradox that the molecular orbitals are electronically isolated from the surface of the wide band gap semiconductor even though strong chemical bonds are formed.     

Electrodeposition of CuInSe2 (CIS) via electrochemical atomic layer deposition (E-ALD)

The growth of stoichiometric CuInSe(2) (CIS) on Au substrates using electrochemical atomic layer deposition (E-ALD) is reported here. Parameters for a ternary E-ALD cycle were investigated and included potentials, step sequence, solution compositions and timing. CIS was also grown by combining cycles for two binary compounds, InSe and Cu(2)Se, using a superlattice sequence. The formation, composition, and crystal structure of each are discussed. Stoichiometric CIS samples were formed using the superlattice sequence by performing 25 periods, each consisting of 3 cycles of InSe and 1 cycle of Cu(2)Se. The deposits were grown using 0.14, -0.7, and -0.65 V for Cu, In, and Se precursor solutions, respectively. XRD patterns displayed peaks consistent with the chalcopyrite phase of CIS, for the as-deposited samples, with the (112) reflection as the most prominent. AFM images of deposits suggested conformal deposition, when compared with corresponding image of the Au on glass substrate.     

Synthesis and antimicrobial activities of new 4,6‐diaryl‐ 4,5‐dihydro‐3‐hydroxy‐2H‐indazoles

A series of new 4,6‐diaryl‐4,5‐dihydro‐3‐hydroxy‐2H‐indazoles 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k were synthesized by the cyclization of ethyl 2‐oxo‐4,6‐diarylcyclohex‐3‐ene carboxylates 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k . The compounds were characterized by IR, ¹H NMR, ¹³C NMR, 2D NMR, and elemental analysis. The synthesized compounds were evaluated for in vitro antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, Candida albicans, Aspergillus niger, Aspergillus flavus, and Rhizopus sp. Most of the compounds exhibited good activity against the tested organisms. J. Heterocyclic Chem.,, (2012).     

IDEAL-A fast single scan method for X pulse width calibration

In line with the recent development of the rapid single scan technique to calibrate proton flip angle, a new method that allows calibration of X-nucleus pulse width in a single scan is presented. The method involves observation of the anti-phase coherence of a proton coupled to a hetero-nuclear X-spin with nutation pulses applied at the X-spin resonance frequency in a gated decoupling experiment. The X-spin nutation causes the well-known illusions of decoupling, enabling estimation of rf amplitude level and the method is, thus, dubbed as IDEAL.     

Kinetic Evidence for the Influence of Subsurface Oxygen on Palladium Surfaces Towards CO Oxidation at High Temperatures

Transient state kinetics of the catalytic oxidation of CO with O₂ on Pd‐surfaces has been measured under isothermal conditions by using a molecular beam approach. Systematic studies were carried out as a function of reaction temperature and CO+O₂ composition. With sufficient kinetic evidence, we have demonstrated the positive influence of subsurface oxygen towards CO‐adsorption and oxidation to CO₂ at high temperatures (600–900 K) on Pd‐surfaces, and the likely electronic nature of the surface changes with oxygen in the subsurface. These studies also provide a direct proof for CO‐adsorption with a significantly reactive sticking coefficient at high temperatures on Pd‐surfaces exhibiting a significant subsurface O‐coverage.     

Measurement of thermal conductivity of fluids using 3-<Emphasis Type=Italic>ω</Emphasis> method in a suspended micro wire

A thermally controlled, compact device employing the 3-ω technique, used to measure the thermal conductivity of fluids, is designed, developed, and presented in this paper. The 3-ω method, which analyzes temperature oscillations data in the frequency domain, requires a microscopic sample and extremely low heating power. The functionality is derived from the approximate solutions of temperature oscillations of a line heater based on the infinite line-heater model over an empirically and analytically chosen range of frequencies. The method is devoid of errors related to transient measurements, fluid thermal stratification and mobility errors, which pose difficulties in other methods. A platinum (99.99% pure) wire of 50 μm diameter and a length of 30 mm, suspended in a sample volume of 25 μl of the test fluid, serves simultaneously as the heater and thermometer. Structure-wise, the device is designed to support measurements over a range of temperatures and fluid pressures providing modularity and flexibility to the instrument. The device is successfully employed to measure the thermal conductivity of de-ionized water for temperatures between 15 and 35°C with an accuracy of ±1.2% inmeasurement.     

Solvent-free protocol for amide bond formation via trapping of nascent phosphazenes with carboxylic acids

A solvent-free synthesis of amides via the coupling of phosphazenes with carboxylic acids is reported. Increasing the rate of heating either by microwave irradiation or conventional heating results in multifold increase in the rate of amide bond formation. Synthesis of a library of amides including a potent antitumour candidate has been accomplished.     

Synthesis of poly(ethylene glycol) block copolymers by a redox process and their spectral characterization

Novel block copolymers of poly(ethylene glycol) (PEG) with acrylamide (AAm) and methacrylic acid (MAA) were synthesized using a redox system consisting of ceric ions and PEG in aqueous acidic medium. The molecular weight of PEG in the redox system was varied to obtain a series of block copolymers with differing molecular weights of PEG segment. The polymerization proceeded via macroradical generation, which was substantiated by ESR spectroscopy. This macroradical acted as a redox macroinitiator for the block copolymerization of the vinyl monomers. The formation of the block copolymers was confirmed by fractional precipitation technique.