Cooperativity of Catechols and Amines in High‐Performance Dry/Wet Adhesives

The outstanding adhesive performance of mussel byssal threads has inspired materials scientists over the past few decades. Exploiting the amino‐catechol synergy, polymeric pressure‐sensitive adhesives (PSAs) have now been synthesized by copolymerizing traditional PSA monomers, butyl acrylate and acrylic acid, with mussel‐inspired lysine‐ and aromatic‐rich monomers. The consequences of decoupling amino and catechol moieties from each other were compared (that is, incorporated as separate monomers) against a monomer architecture in which the catechol and amine were coupled together in a fixed orientation in the monomer side chain. Adhesion assays were used to probe performance at the molecular, microscopic, and macroscopic levels by a combination of AFM‐assisted force spectroscopy, peel and static shear adhesion. Coupling of catechols and amines in the same monomer side chain produced optimal cooperative effects in improving the macroscopic adhesion performance.     

Pt coated Cr2O3 thin films for resistive gas sensors

The resistive response of atomic layer deposited thin epitaxial α-Cr₂O₃(0 0 1) films, to H₂ and CO in air, was studied. The films were covered with Pt nanoislands formed by electron-beam evaporation of a sub-monolayer amount of the material. The gas measurements were performed at 250°C and 450°C. These temperatures led to different proportion of chemical states, Pt²⁺ and Pt⁴⁺, to which the Pt oxidized. The modification was ascertained by the X-ray photoelectron spectroscopy method. As a result of the modification, the response was fast at 250°C, but slowed at 450°C. A disadvantageous abundance of Pt⁴⁺ arising at 450°C in air could be diminished by high-vacuum annealing thus restoring the response properties of the system at 250°C.      

Effect of pressure on the properties of DH diode lasers in AlxGa1-xAsySb1-y/GaSb system

Abstract

A helium pressure appparatus for diode laser studies up to 1.4 GPa at 77–300 K has been developed. DH lasers with Al_xGa_1-xAs_ySb_1-y active layers (x=0-0.05) lattice-matched to GaSb substrates have been investigated. It has been shown that in lasers with x,y=0 pressure dependences of the threshold current density (J_th) and the average electron lifetime at the threshold (τ) measured at 80 K depend strongly on the quadratic recombination of L^c ₆ electrons, the characteristic coefficient being 1.5×10^?11 cm³s^?1. The pressure-composition equivalence coefficient dx/dP=2.2×10^?10 Pa^?1 has been obtained for the lowest temperatures used.     

Investigation of the effects of the local environment on the surface-enhanced Raman spectra of striped gold/silver nanorod arrays

The effects of the local environment on surface-enhanced Raman scattering (SERS) spectra utilizing gold, silver, and gold/silver striped nanorod array substrates was investigated. The arrays were fabricated using an electrochemical metal deposition into an anodic aluminum oxide template. The analyte chosen for this study was p-nitroso-N,N-dimethylaniline (p-NDMA), which has an electronic structure that is highly sensitive to its surrounding environment. Changes in the peak positions and peak ratios were used to probe the influence of water and the striping pattern on the SERS signal of p-NDMA. We present the results of the fabrication and characterization of the nanorod array substrates, as well as SERS spectra of p-NDMA in both polar and nonpolar environments and SERS spectra on a variety of striped nanorod arrays. The Raman data suggests that the p-NDMA molecule exists in a more polarized state when bound to the gold as compared to the silver rods. We have attempted to use these differences to determine whether the SERS signal predominantly arises from the tips of the rods or from the interior of the array.     

Cooperativity of Catechols and Amines in High-Performance Dry/Wet Adhesives

The outstanding adhesive performance of mussel byssal threads has inspired materials scientists over the past few decades. Exploiting the amino-catechol synergy, polymeric pressure-sensitive adhesives (PSAs) have now been synthesized by copolymerizing traditional PSA monomers, butyl acrylate and acrylic acid, with mussel-inspired lysine- and aromatic-rich monomers. The consequences of decoupling amino and catechol moieties from each other were compared (that is, incorporated as separate monomers) against a monomer architecture in which the catechol and amine were coupled together in a fixed orientation in the monomer side chain. Adhesion assays were used to probe performance at the molecular, microscopic, and macroscopic levels by a combination of AFM-assisted force spectroscopy, peel and static shear adhesion. Coupling of catechols and amines in the same monomer side chain produced optimal cooperative effects in improving the macroscopic adhesion performance.     

Lebensdauermessungen am 341,2keV-Zustand und am 404,8 keV-Zustand in131Xe

Lifetime measurements of two excited states in¹³¹Xe populated by the decay of¹³¹I have been carried out. Analysis of data, delivered from a delayed γ-γ-coincidence experiment with a Ge(Li)-Plasticdetector combination, resulted in the following values:T _1/2 of 341.2 keV level in¹³¹Xe: (2.15 ± 0.07) nsT _1/2 of 404.8 keV level in¹³¹Xe: <0.5 ns.     

A Constructive theory of triple and quintuple product identities of the second degree

The groundwork for a theory of quadratic identities involving the classical triple and quintuple products is layed. The approach is through the study and use of affine maps that act on indexing lattices associated with the terms (double sums) in the given identity. The terms of the identity are found to be connected by the invariant of a ternary quadratic form.