A mild, copper catalyzed route to conducting polyaniline

The aniline dimer, N-(4-aminophenyl)aniline has been polymerized cleanly under mild conditions to obtain an emeraldine base form of polyaniline using [MeB(3-(Mes)Pz)3]CuCl as the catalyst and H2O2 as the oxidant, while the subsequent acidification of the emeraldine base gives the conducting emeraldine salt form of polyaniline.     

Rationalization of nanowire synthesis using low-melting point metals

In this paper, we provide a theoretical basis using thermodynamic stability analysis for explaining the spontaneous nucleation and growth of a high density of 1-D structures of a variety of materials from low-melting metals such as Ga, In, or Sn. The thermodynamic stability analysis provides a theoretical estimate of the extent of supersaturation of solute species in molten metal solvent. Using the extent of maximum supersaturation, the size and density of critical nucleus were estimated and compared with experimental results using nucleation and growth of Ge nanowires using Ga droplets. The consistency of the proposed model is validated with the size and density of the resulting nanowires as a function of the synthesis temperature and droplet size. Both the experimental evidence and the theoretical model predictions point that the diameters of the resulting nanowires decrease with the lowering of synthesis temperatures and that the nucleation density decreases with the size of metal droplet diameter and increasing synthesis temperature.     

Experimental observations of redistributed energy in wave interference

Attempts to explain the redistribution of energy in interference has been done from time to time, under two of the most accepted theories, wave and quantum; however its mechanism still lacks clear interpretation. In this study, a new experiment has been designed and conducted to observe the redistributed energy in wave interference. Experimental observations on the redistributed energy that occurs in two interfering coherent waves are presented. Re-distributed energy at a certain region, (single bright fringe) in space due to interference of two waves was isolated at a plane and measured at a distant plane away from the isolated plane. The measured energy distribution of the isolated interference pattern was compared with the resultant calculated from the two individual interfering components based on wave theory. The calculated resultant due to the two individual components does not tally with the experimental observed pattern. Hence, the outcome of this experiment is in disagreement with the expected predictions as per the wave theory.     

Dual-band pixelless upconversion imaging devices

We have proposed a type of mid-infrared (MIR) and far-infrared (FIR) dual-band imaging device, which employs the photon frequency upconversion concept in a GaN/AlGaN MIR and FIR dual-band detector integrated with a GaN/AlGaN violet light emitting diode. On the basis of the photoresponse of single-period GaN/AlGaN dual-band detectors, we present the detailed optimization of multiperiod GaN emitter/AlGaN barrier detectors and their applications to dual-band pixelless upconversion imaging. Satisfying images have been received through the analysis of the modulation transfer function and the upconversion efficiency in the GaN/AlGaN dual-band pixelless upconverters, which exhibit good image resolution, high quantum efficiency, and negligible cross talk.     

Analysis of N‐acetylaminosugars by CE: A comparative derivatization study

N‐linked or O‐linked glycans derived from glycoprotein processing carry, an N‐acetylglucosamine or an N‐acetylgalactosamine respectively, at their reducing termini. The presence of the N‐acetylamino group on C‐2 of reducing sugar residues has been reported to hamper the derivatization reaction with a chromophore at the anomeric centre. In this paper N‐acetyllactosamine, N‐acetylglucosamine, N‐acetylgalactosamine and several other neutral monosaccharides are coupled to three different dyes (4‐aminobenzonitrile, 2‐aminopyridine, 2‐aminobenzoic acid (2‐AA)) by reductive amination and analysed by CE with UV detection. The 2‐AA derivatives showed the lowest concentration detection limits, varying approximately in the 2–3 μM range for the saccharides tested including the N‐acetamido ones. The possibility to separate and detect with the same sensitivity ten 2‐AA‐labelled monosaccharides mainly found in mammalian or plant glycoproteins in a single CE run is highlighted. The analysis has been carried out in less than 25 min using the borate‐complexation method in CZE mode. The influence of the strength of the acid used as catalyst in the chemical modification of the sugars with 2‐AA is also shortly addressed.     

Molar Volumes and Heat Capacities of Electrolytes and Ions in Nonaqueous Solvents: 1. Formamide

Apparent molar volumes and heat capacities of 27 electrolytes have been measured as a function of concentration in formamide at 25°C using a series-connected flow densimeter and Picker calorimeter system. These data were extrapolated to infinite dilution using the appropriate Debye–Hückel limiting slopes to give the corresponding standard partial molar quantities. Ionic volumes and heat capacities at infinite dilution were obtained by an appropriate assumption based on the reference electrolyte Ph₄PBPh₄ (TPTB). The ionic volumes, but not the heat capacities, agree reasonably well with previously published statistically based predictions. The values obtained are discussed in terms of simple models of electrolyte solution behavior and a number of interesting features are noted, including, possible dependencies of ionic volumes on solvent isothermal compressibility and of ionic heat capacities on solvent electron acceptor abilities.     

The synthesis and reactions of a monocyclic β-lactam tripeptide, 1-[(1R)-carboxy-2-methylpropyl]- (3R -[(5S-5-amino- 5-carboxypentanamido]-(4R)-mercaptoazetidin-2-one,a putative intermediate in penicillin biosynthesis

The disulphide corresponding to the above thiol has been synthesised, but all attempts to reduce this substance to the thiol were unsuccessful, although an alternative procedure via a thiomercury intermediate, enabled the thiol to be generated in situ, the properties of this thiol, however, are not in accord with those previously described for a putative free intermediate in penicillin biosynthesis.¹     

A surface adsorption/reaction mechanism for gold oxidation by copper(II) in ammoniacal thiosulfate solutions

Literature data for gold dissolution in ammoniacal copper(II) thiosulfate solutions is reinterpreted on the basis of adsorption and mixed potential theory. The dissolution reaction appears to take place via the adsorption of copper(II)-ammonia-thiosulfate onto the gold surface, forming the adsorbed species perpendicular to Au(S2O3)nCu(NH3)-(2n-2)p. Equilibrium constants for the formation of these species from Cu(NH3)(2+)m are in the range Kads=172-510 (molar units) for m=4, n=1 or 2, and p=2 or 3. These complexes decompose with a rate constant of kAu=1.7 x 10(-4)molm(-2)s(-1), to produce Au(S2O3)(3-)2 and Cu(NH3)+(3) or Cu(NH3)+(2), where the copper(I) complexes in solution are re-equilibrated to the more stable species Cu(S2O3)3-(2) and Cu(S2O2)5-(3).     

The ammine, thiosulfato, and mixed ammine/thiosulfato complexes of silver(I) and gold(I)

The M(I)-NH(3), M(I)-S(2)O(3)(2)(-), and M(I)-S(2)O(3)(2)(-)-NH(3) systems (M = Ag, Au) were studied at 25 degrees C and at I = 0.1 M (NaClO(4)) using a variety of analytical techniques. For the Ag(I)-NH(3)-S(2)O(3)(2)(-) system, AgS(2)O(3)NH(3)(-) was detected with formation constant log beta(111) (for the reaction Ag(+) + S(2)O(3)(2)(-) + NH(3) <--> AgS(2)O(3)NH(3)(-)) of 11.2, 10.4, and 10.8 on the basis of silver potentiometry, UV-vis spectrophotometry, and hydrodynamic voltammetry, respectively. Also, the values of log beta(101)(AgNH(3)(+)), log beta(102)(Ag(NH(3))(2)(+)), log beta(110)(AgS(2)O(3)(-)), and log beta(120)(Ag(S(2)O(3))(2)(3)(-)), obtained from silver potentiometry, were 3.59, 7.0, 8.97, 13.1, respectively. In the case of the ammine complexes, the log beta(101)(AgNH(3)(+)) and log beta(102)(Ag(NH(3))(2)(+)) values were found to be 3.5 and 7.1, respectively, from the UV-vis spectrophotometric experiments. The mixed species AuS(2)O(3)NH(3)(-) was detected in UV-vis spectrophotometric, hydrodynamic voltammetric, and potentiometric experiments with the stepwise formation constants (log K(111)) of -4.0, -3.5, -3.8, respectively, for the reaction Au(S(2)O(3))(2)(3)(-) + NH(3) <--> AuS(2)O(3)NH(3)(-) + S(2)O(3)(2)(-). At higher [NH(3)]/[S(2)O(3)(2)(-)] ratios (>10(5)), the formation of Au(NH(3))(2)(+) was also detected in spectrophotometric and potentiometric experiments with stepwise formation constants (log K(102)) of -5.4 and -5.3, respectively, according to the reaction AuS(2)O(3)NH(3)(-) + NH(3) <--> Au(NH(3))(2)(+) + S(2)O(3)(2)(-).