Interpretation of reactivity in radical polymerization—Radicals,monomers, and transfer agents: Beyond the Q‐e scheme

50 years ago, Alfrey and Price advanced the Q‐e scheme for the interpretation of radical and monomer reactivity and the prediction of monomer reactivity ratios in radical copolymerization. Despite the early criticism of the scheme by Mayo and Walling, and its obvious fundamental shortcomings, it continues to be essentially the only such scheme in use today. However, the more soundly based Patterns of Reactivity Scheme, originally proposed in 1959, has recently been revised in such a way that it provides, in a simple way, far more accurate predictions of monomer reactivity ratios than does the Q‐e scheme. Moreover, it is equally applicable to the forecasting of chain‐transfer constants and to the understanding of the reactivity of initiator radicals. The history of investigations of radical, monomer, and transfer agent reactivity is reviewed here, including a summary of the Revised Patterns Scheme and its applications. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 113–126, 1999     

Immunoassay as an analytical tool in agricultural biotechnology

Immunoassays for biotechnology engineered proteins are used by AgBiotech companies at numerous points in product development and by feed and food suppliers for compliance and contractual purposes. Although AgBiotech companies use the technology during product development and seed production, other stakeholders from the food and feed supply chains, such as commodity, food, and feed companies, as well as third-party diagnostic testing companies, also rely on immunoassays for a number of purposes. The primary use of immunoassays is to verify the presence or absence of genetically modified (GM) material in a product or to quantify the amount of GM material present in a product. This article describes the fundamental elements of GM analysis using immunoassays and especially its application to the testing of grains. The 2 most commonly used formats are lateral flow devices (LFD) and plate-based enzyme-linked immunosorbent assays (ELISA). The main applications of both formats are discussed in general, and the benefits and drawbacks are discussed in detail. The document highlights the many areas to which attention must be paid in order to produce reliable test results. These include sample preparation, method validation, choice of appropriate reference materials, and biological and instrumental sources of error. The article also discusses issues related to the analysis of different matrixes and the effects they may have on the accuracy of the immunoassays.     

Total dissolved solids estimation with a fiber optic sensor of surface plasmon resonance

In this paper, surface plasmon spectra of ion influence was investigated by using a fabricated fiber optic sensors, then spectrum subtraction of ion and non-ionic solutions were developed for field applications of total dissolved solids (TDS) estimation. We confirmed the SPR spectral difference between seven ionic and three non-ionic liquid samples, that for the same refractive index, resonance wavelength in SPR spectrum is much higher for ionic samples than that in the case of non-ionic ones due to the ions influence. The positive correlation of ion content and extra resonance wavelength shift has been established for TDS estimation in water. With three groups of water samples investigation and field testing, the proposed SPR technique showed a good performance comparable to the conductivity method.     

The interaction of iron pyrite with oxygen, nitrogen and nitrogen oxides: a first-principles study

Sulphide materials, in particular MoS(2), have recently received great attention from the surface science community due to their extraordinary catalytic properties. Interestingly, the chemical activity of iron pyrite (FeS(2)) (the most common sulphide mineral on Earth), and in particular its potential for catalytic applications, has not been investigated so thoroughly. In this study, we use density functional theory (DFT) to investigate the surface interactions of fundamental atmospheric components such as oxygen and nitrogen, and we have explored the adsorption and dissociation of nitrogen monoxide (NO) and nitrogen dioxide (NO(2)) on the FeS(2)(100) surface. Our results show that both those environmentally important NO(x) species chemisorb on the surface Fe sites, while the S sites are basically unreactive for all the molecular species considered in this study and even prevent NO(2) adsorption onto one of the non-equivalent Fe-Fe bridge sites of the (1 × 1)-FeS(2)(100) surface. From the calculated high barrier for NO and NO(2) direct dissociation on this surface, we can deduce that both nitrogen oxides species are adsorbed molecularly on pyrite surfaces.     

Cyclometalated platinum(II) diimine complexes: synthetically tuning the photophysical and electrochemical properties

Presented is the synthesis of an array of 16 heteroleptic phosphorescent diimine complexes of platinum(II) with electronically diverse ligand spheres and their full spectroscopic, photophysical, and electrochemical characterization. The complexes were found to exhibit luminescence (480-500 nm) in deaerated solutions at room temperature from a long-lived (3)LC state (τ = 2-3 μs) that exhibits significant metal character perturbed by a low-lying (1)MLCT state. Interestingly, emission from a (3)MLCT state was not observed as is the case with many other polypyridine-based d-block complexes. Electrochemical intermediates proved stable as multiple reversible reductions between -1 and -2 V vs. SCE were noted during cyclic voltammetry experiments unveiling the potential of these luminophores for use in a variety of optoelectronic and solar energy conversion applications.     

Rigid NON- and NSN-ligand complexes of tetravalent and trivalent uranium: comparison of U-OAr2 and U-SAr2 bonding

A rigid NSN-donor proligand, 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylthioxanthene (H(2)[TXA(2)], 1) was prepared by palladium-catalyzed coupling of 2,6-diisopropylaniline with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylthioxanthene. Deprotonation of 1 using (n)BuLi provided Li(2)(DME)(2)[TXA(2)] (2), and subsequent reaction with UCl(4) afforded [Li(DME)(3)][(TXA(2))UCl(3)] (4). The analogous NON-donor ligated complex [(XA(2))UCl(3)K(DME)(3)] [3; XA(2) = 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene] was prepared by the reaction of K(2)(DME)(x)[XA(2)] with UCl(4). A cyclic voltammogram (CV) of 3 in THF/[NBu(4)][B(C(6)F(5))(4)] at 200 mV s(-1) showed an irreversible reduction to uranium(III) at E(pc) = -2.46 V versus FeCp(2)(0/+1), followed by a product wave at E(1/2) = -1.83 V. Complex 4 also underwent irreversible reduction to uranium(iii) [E(pc) = -2.56 V], resulting in an irreversible product peak at E(pa) = -1.83 V. One-electron reduction of complexes 3 and 4 using K(naphthalenide) under an argon atmosphere in DME yielded 6-coordinate [(XA(2))UCl(DME)] (5) and the thermally unstable 7-coordinate [(TXA(2))U(DME)Cl(2)Li(DME)(2)] (6), respectively. The U-S distances in 4 and 6 are uncommonly short, the C-S-U angles are unusually acute, and the thioxanthene backbone of the TXA(2) ligand is significantly bent. By contrast, the xanthene backbone in XA(2) complexes 3 and 5 is planar. However, κ(3)-coordination and an approximately meridional arrangement of the ancillary ligand donor atoms is maintained in all complexes. DFT and Atoms in Molecules (AIM) calculations were carried out on 3, 4, 5, 6, [(XA(2))UCl(3)](-) (3B), [(TXA(2))UCl(2)(DME)](-) (6B) and [(TXA(2))UCl(DME)] (6C) to probe the extent of covalency in U-SAr(2) bonding relative to U-OAr(2) bonding.     

Surface-initiated synthesis of poly(3-methylthiophene) from indium tin oxide and its electrochemical properties

Poly(3-methylthiophene) (P3MT) was synthesized directly from indium tin oxide (ITO) electrodes modified with a phosphonic acid initiator, using Kumada catalyst transfer polymerization (KCTP). This work represents the first time that polymer thickness has been controlled in a surface initiated KCTP reaction, highlighting the utility of KCTP in achieving controlled polymerizations. Polymer film thicknesses were regulated by the variation of the solution monomer concentration and ranged from 30 to 265 nm. Electrochemical oxidative doping of these films was used to manipulate their near surface composition and effective work function. Doped states of the P3MT film are maintained even after the sample is removed from solution and potential control confirming the robustness of the films. Such materials with controllable thicknesses and electronic properties have the potential to be useful as interlayer materials for organic electronic applications.