Electrochemically synthesized polymers in molecular imprinting for chemical sensing

This critical review describes a class of polymers prepared by electrochemical polymerization that employs the concept of molecular imprinting for chemical sensing. The principal focus is on both conducting and nonconducting polymers prepared by electropolymerization of electroactive functional monomers, such as pristine and derivatized pyrrole, aminophenylboronic acid, thiophene, porphyrin, aniline, phenylenediamine, phenol, and thiophenol. A critical evaluation of the literature on electrosynthesized molecularly imprinted polymers (MIPs) applied as recognition elements of chemical sensors is presented. The aim of this review is to highlight recent achievements in analytical applications of these MIPs, including present strategies of determination of different analytes as well as identification and solutions for problems encountered

Binding and release of glutamate from overoxidized polypyrrole via an applied potential for application as a molecular switch

The controlled binding and release of glutamate from overoxidized polypyrrole (PPy) films via a variable potential was investigated. Glutamate-doped PPy films were electrochemically deposited from aqueous sodium glutamate electrolytes containing the pyrrole monomer. The resulting polymer films were found to have a high degree of roughness, which increased with increasing film thickness. This was also found to correspond to an increase in the glutamate content on the PPy film surface. The glutamate content on the film was in the order of 10-8 m/cm2 depending on the film deposition time. Glutamate was then released from the film into the electrolyte through overoxidization of the PPy layer and an applied potential. The amount of glutamate released from the film was greater than that on the surface of the film indicating that glutamate can be released from the PPy film via an applied potential. The switching behaviour of the polymer electrode, i. e. the repeated binding and release of glutamate to/from the polymer film via a variable potential, was investigated. The glutamate content in the samples was detected via liquid scintillation counting techniques performed on samples prepared with tritium (3H)-marked glutamate

Identifying interfacial failure mode in aerospace adhesive bonds by broadband dielectric spectroscopy

The most widely accepted test for bond durability analysis in aerospace metal-bonded structures is the bondline corrosion test introduced in the late 90s. Little progress has been made however on non-destructive testing methods that allow determining the bond quality after years of use. Here, a non-destructive method based on dielectric spectroscopy is introduced to evaluate the state of a metal-adhesive-metal bond exposed to salt fog spray up to 180 days. Several samples were evaluated with broadband dielectric spectroscopy (BDS), floating roller peel (FRP) tests and bondline corrosion (BLC) after exposure to salt fog spray test for different times. Relaxation processes and conductivity phenomena extracted from the BDS data (e.g. apparent conductivity relaxation time (τmax) using electric modulus) are found to correlate well with the bond strength measured in peel test and BLC progression. The BDS-based protocol was able to identify the local interfacial degradation stages in a non-destructive mode and with high resolution. The protocol has the potential to be further developed into a test method for durability on coupon level.Facility Aerospace Structures & Materials Laboratory(OLD) MSE-1Novel Aerospace Material

Slag Treatment Followed by Acid Leaching as a Route to Solar-Grade Silicon

Refining of metallurgical-grade silicon was studied using a process sequence of slag treatment, controlled cooling, and acid leaching. A slag of the Na2O-CaO-SiO2 system was used. The microstructure of grain boundaries in the treated silicon showed enhanced segregation of impurities, and the formation of CaSi2 and other Ca-rich phases. Boron and phosphorus were found in the grain boundary phases of silicon after the slag treatment and were successfully removed together with most of the metallic impurities by acid leaching. The interaction between silicon and slag and the distribution of impurities are discussed. A novel mechanism of the refining approach is proposed, based on the microstructure of silicon and the analysis of impurities at each refining step. Parallel processes of slag refining, segregation, and solvent refining were observed, which explains the relatively high efficiency of the proposed refining technology. The investigated combination of refining processes followed by acid leaching has great potential as an efficient and cost-saving route for upgrading metallurgical-grade to solar-grade silicon.Materials Innovation InstituteMechanical, Maritime and Materials Engineerin