Metal ion reactive thin films using spray electrostatic LbL assembly

By using the spray-layer-by-layer (Spray-LbL) technique, the number of metal counterions trapped within LbL coatings is significantly increased by kinetically freezing the film short of equilibrium, potentially limiting interchain penetration and forcing chains to remain extrinsically compensated to a much greater degree than observed in the traditional dipped LbL technique. The basis for the enhanced entrapment of metal ions such as Cu2+, Fe2+, and Ag+ is addressed, including the equilibrium driving force for extrinsic compensation by soft versus hard metal ions and the impact of Spray-LbL on the kinetics of polymer-ion complexation. These polymer-bound metal-ion coatings are also demonstrated to be effective treatments for air filtration, functionalizing existing filters with the ability to strongly bind toxic industrial compounds such as ammonia or cyanide gases, as well as chemical warfare agent simulants such as chloroethyl ethyl sulfide. On the basis of results reported here, future work could extend this method to include other toxic soft-base ligands such as carbon monoxide, benzene, or organophosphate nerve agents.     

Photophysical characterization of a highly conjugated bipyridyl-based dye synthesized by a unique two-step approach

In this article, we present a new and simple, yet efficient, two-step approach to synthesize 4,4'-bis(dibutylaminostyrylstyryl)-2,2'-bipyridine with high yield, as well as its linear and nonlinear optical characterizations in THF and toluene solutions. We show that its one- and two-photon absorption spectra are similar in both solvents. Nevertheless, the relaxation processes of this compound exhibit dependence on the solvent polarity. The one- and two-photon induced fluorescence signal of this molecule in solution reveals that its excited state is highly stabilized in THF solution rather than in toluene. Analysis of the fluorescence quantum yield, lifetime, and radiative and nonradiative decay rates are in agreement with Lippert's model for solute-solvent interactions. The optical measurements demonstrate that this dye is a promising candidate for multiphoton fluorescence imaging, optical limiting, and dye lasers.     

Nanochannels in SU-8 with floor and ceiling metal electrodes and integrated microchannels

Sacrificially etched 2-D nanofluidic channels and nanospaces with integrated floor and ceiling electrodes and arbitrary channel geometries have been demonstrated with channel heights from 20 nm to 400 nm, widths from 800 nm to 40 microm, and lengths up to 3 mm, using SU-8 as the channel structural material.     

New structural types and different oxidation levels in the family of Mn6-oxime single-molecule magnets

The synthesis and magnetic properties of three new members of a family of salicyaldoxime based [Mn6] single-molecule magnets possessing new structural types, core topologies and Mn oxidation state distributions are reported. The isostructural complexes [MnIII6O2(R-sao)6(X)2(EtOH)6] (R = Et, X = Br (1); R = Me, X = I (2)) exhibit single-molecule magnet behaviour with spin Hamiltonian parameters S = 12, g = 1.98 and D = -0.36 cm(-1) in both cases. The hexametallic cluster [MnIII4MnIV2O2(OMe)(4-)(Et-sao)6(MeOH)2].MeOH (3.MeOH) possesses a planar rod-like topology and a mixed valent [MnIV4MnIII2] core, which is unprecedented in this family of [Mn6] SMMs.     

Synthesis of hyperbranched poly(aryl amine)s via a carbene insertion approach

A novel diazirine functionalised aniline derivative, 3-(3-aminophenyl)-3-methyldiazirine 1, was prepared and employed as an AB(2)-type monomer in the synthesis of hyperbranched polymers; thus providing the first instance in which polyamines have been prepared via carbene insertion polymerisation. Photolysis of the monomer 1 in bulk and in solution resulted in the formation of hyperbranched poly(aryl amine)s with degrees of polymerisation (DP) varying from 9 to 26 as determined by gel permeation chromatography (GPC). In solution, an increase in the initial monomer concentration was generally found to result in a decrease in the molecular weight characteristics of the resulting poly(aryl amine)s. Subsequent thermal treatment of the poly(aryl amine)s caused a further increase in the DP values up to a maximum of 31. Nuclear magnetic resonance (NMR) spectroscopic analysis revealed that the increase in molecular weight upon thermal treatment resulted from hydroamination of styrenic species formed in the initial photopolymerisation or activation of diazirine moieties.