Synthesis and structure of charge transfer salts of tetrathiafulvalene (TTF) and tetramethyl-TTF with 2,4,7-trinitro and 2,4,5,7-tetranitro-9-fluorenone

Charge transfer salts of tetrathiafulvalene (TTF) and tetramethyltetrathiafulvalene (TMTTF) with the organic acceptors 2,4,7-trinitro-9-fluorenone and 2,4,5,7-tetranitro-9-fluorenone have been prepared and characterized. The compounds (TTF)[TENF] (1), (TTF)₃[TRNF]₂ (2) and (TMTTF)[TRNF] (3) contain mixed stacks of alternating TTF and nitrofluorenone units. Surprisingly, the degree of charge transfer that occurs in these salts is not controlled solely by the redox potentials of the building blocks, but apparently also by the most effective intermolecular interactions in the solid, as determined from the crystal structures obtained. These three compounds exhibit poor electron delocalization and therefore they behave as diamagnetic insulators.     

Cognitive mechanisms underlying implicit negative self concept in dysphoria.

Whereas explicit measures of the self-concept typically demonstrate a negative bias in depressed individuals, implicit measures such as the Implicit Association Test (IAT), revealed an opposite, positive bias. To address this inconsistent pattern, the authors examined, using a novel paradigm, mental set maintenance (i.e., the difficulty of maintaining active a required mental set) and set operation (the efficiency of executing the mental set while it is maintained). Dysphoric (N = 33) and nondysphoric (N = 30) participants alternated between an IAT focusing on self reference and a matched neutral task. Nondysphorics had greater difficulty in maintaining a negative self reference task compared to a neutral task. Conversely, dysphorics did not exhibit such difficulty, and they maintained a negative self-reference task more easily than nondysphorics. No group differences were evinced in smoothness of set operation. These results suggest that the shield protecting nondysphorics from maintaining negative mental sets is absent in dysphorics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Protecting equipment against electromagnetic noise in power-supply networks

The problems of how to secure the electromagnetic compatibility of technological equipment with the help of resonance transfilters (matching filter) are examined. An equivalent circuit and mathematical model for transfilters are developed. The tests results verify the adequacy of the mathematical model.     

Direct measurement of the Cu oxidation number of cuprate superconductor ceramics

The Cu oxidation number in YBa₂Cu₃O₇ has been measured directly by soft X-ray fluorescent spectroscopy both at room temperature and at liquid N₂ temperature. The measurements are based on a calibration curve from different Ba-O compounds. The effect of changes in oxidation number above and below the transition temperature and its role in highT _c superconductivity are discussed.     

Micropower active-RC channel filter for a zero-IF Bluetooth receiver

A fourth-order low-pass channel filter for a zero-IF Bluetooth receiver is presented. It employs two cascaded multiple feedback biquads and active resistors made by quasi-floating gate MOS transistors in triode region for highly linear continuous tuning. Power consumption is strongly reduced using a gain-enhanced class-AB single-stage opamp together with a filter topology that only requires a single opamp for each biquad. The filter has been fabricated in a 0.18 μm CMOS technology and consumes 290 μW from a 1.2 V supply.     

DC offset control with application in a zero-IF 0.18 μm CMOS Bluetooth receiver chain

A compact DC offset correction circuit based on the intrinsic properties of quasi-floating gate (QFG) transistors is presented. The proposed scheme uses a tuning mechanism to make its initial response faster improving the traditional large settling time of these circuits. A zero-IF baseband receiver chain suitable for Bluetooth that includes the proposed dc offset correction has been designed in a 0.18 μm CMOS technology at 1.2 V supply voltage.     

Synthesis and properties of an ionic polyacetylene with norbornene moieties

New conjugated ionic polymer with the pendent norborene moieties was prepared by the activated polymerization of 2-ethynylpyridine by using 5-[(5-bromopenthoxy)methyl]-2-norborene without any additional initiator or catalyst. This polymerization proceeded well in the mild reaction condition to give a high yield of polymer (polymer yield: 90%). The chemical structure of poly{2-ethynyl-N-[(5-norborenylmethoxy)pentyl]pyridinium bromide} (PENPPB) was characterized by such instrumental methods as NMR (¹H and ¹³C), IR, UV–vis spectroscopies, and elemental analysis to have the conjugated polymer backbone bearing norbornyl moieties. The photoluminescence maximum peak of polymer was located at 519 nm, which corresponds to the photon energy of 2.39 eV. The norbornyl substituents within the polyacetylene-based polymers shifted PL maximum values because substituent size affects the molecule arrangement. The cyclovoltammograms of polymer exhibited the electrochemically stable window at ?1.6 to 2.3 V region. It was found that the kinetics of the redox process of polymer might be mainly controlled by the electron transfer process based on the experiment of the oxidation current density of polymer versus the scan rate.     

Boron and Sodium Doping of Polymeric Carbon Nitride Photoanodes for Photoelectrochemical Water Splitting

Polymeric carbon nitride is a promising photoanode material for water-splitting and organic transformation-based photochemical cells. Despite achieving significant progress in performance, these materials still exhibit low photoactivity compared to inorganic photoanodic materials because of a moderate visible light response, poor charge separation, and slow oxidation kinetics. Here, the synthesis of a sodium- and boron-doped carbon nitride layer with excellent activity as a photoanode in a water-splitting photoelectrochemical cell is reported. The new synthesis consists of the direct growth of carbon nitride (CN) monomers from a hot precursor solution, enabling control over the monomer-to-dopant ratio, thus determining the final CN properties. The introduction of Na and B as dopants results in a dense CN layer with a packed morphology, better charge separation thanks to the in situ formation of an electron density gradient, and an extended visible light response up to 550 nm. The optimized photoanode exhibits state-of-the-art performance: photocurrent densities with and without a hole scavenger of about 1.5 and 0.9 mA cm⁻² at 1.23 V versus reversible hydrogen electrode (RHE), and maximal external quantum efficiencies of 56% and 24%, respectively, alongside an onset potential of 0.3 V.