Synthesis of pure colloidal silver nanoparticles with high electroconductivity for printed electronic circuits: the effect of amines on their formation in aqueous media

This paper describes a practical and convenient method to prepare stable colloidal silver nanoparticles for use in printed electronic circuits. The method uses a dispersant and two kinds of reducing agents including 2-(dimethylamino) ethanol (DMAE), which play important roles in the reduction of silver ions in an aqueous medium. The effect of DMAE and dispersant, as well as the factors affecting particle size and morphology are investigated. In the formation of the silver nanoparticles, reduction occurs rapidly at room temperature and the silver particles can be separated easily from the mixture in a short time. In addition, organic solvents are not used. Pure, small and relatively uniform particles with a diameter less than 10 nm can be obtained that exhibit high electroconductivity. The silver nanoparticles are stable, and can be isolated as a dried powder that can be fully redispersed in deionized water. This method of producing colloidal silver nanoparticles will find practical use in electronics applications.     

Functionalization of ‘kite’ shaped styryl end-capped benzodithiophene with ketone groups: synthesis, characterization and properties

We report the synthesis of a new bridged end-capped distyryldithiophene with ketone groups on the bridge: E,E-2,7′-bis((2-phenyl)-ethenyl)-benzo[2,1-b:3,4-b′]dithiophene-4,5-dione 1. Optical and electrochemical properties of 1 in solution were investigated by UV-vis absorption and cyclic voltammetry and compared to the unsubstituted parent molecule (KDS2T). Morphology of 1-based thin films was investigated by scanning electron microscopy (SEM) and the crystalline structure characterization by X-ray diffraction (XRD). Thin films were implemented as active layers into organic thin-film transistors (OTFT) in top contact configuration to evaluate the charge transport properties.     

Super flexibility of a 2D Cu-based porous coordination framework on gas adsorption in comparison with a 3D framework of identical composition: framework dimensionality-dependent gas adsorptivities

Selective synthetic routes to coordination polymers [Cu(bpy)(2)(OTf)(2)](n) (bpy = 4,4'-bipyridine, OTf = trifluoromethanesulfonate) with 2- and 3-dimensionalities of the frameworks were established by properly choosing each different solvent-solution system. They show a quite similar local coordination environment around the Cu(II) centers, but these assemble in a different way leading to the 2D and 3D building-up structures. Although the two kinds of porous coordination polymers (PCPs) both have flexible frameworks, the 2D shows more marked flexibility than the 3D, giving rise to different flexibility-associated gas adsorption behaviors. All adsorption isotherms for N(2), CO(2), and Ar on the 3D PCP are of type I, whereas the 2D PCP has stepwise gas adsorption isotherms, also for CH(4) and water, in addition to these gases. The 3D structure, having hydrophilic and hydrophobic pores, shows the size-selective and quadrupole-surface electrical field interaction dependent adsorption. Remarkably, the 2D structure can accommodate greater amounts of gas molecules than that corresponding to the inherent crystallographic void volume through framework structural changes. In alcohol adsorption isotherms, however, the 2D PCP changes its framework structure through the guest accommodation, leading to no stepwise adsorption isotherms. The structural diversity of the 2D PCP stems from the breathing phenomenon and expansion/shrinkage modulation.     

Energy transfer dynamics in wire-type dendrimers having oligophenylene peripheries

Energy transfer and shielding effect are studied in wire-type dendrimers (GnPPV: nth generation dendrimer with poly-(p-phenylenevinylene) backbone; n=1, 2) having oligophenylene light-harvesting (LH) antenna. Following the excitation of the LH-antennae, backbone-polymers in GnPPV give rise to intense photoluminescence (PL) bands. This is due to the presence of highly efficient energy transfer from the LH-antennae to the backbone-polymers. The intensity of backbone-PL increases faster than the decay of the antenna-PL. This result indicates that rapid energy transfer from antenna to backbone takes place utilizing the overlap of wavefunctions in the excited states. In G2PPV having larger LH-antenna, shielding effect against inter-backbone interactions is recognized more effectively than G1PPV. In solid films of GnPPV, red shifts of the backbone-PL bands are observed. This is caused by inter-backbone interactions of the wire-type dendrimers due to aggregation. The extent of the red shift in G2PPV is smaller than that of G1PPV. This result suggests that the larger LH-antenna in G2PPV substantially wraps its backbone-polymer and shields the inter-backbone interactions.