Effects of Thermal Annealing Upon the Nanomorphology of Poly(3‐hexylselenophene)‐PCBM Blends

Grazing incidence X‐ray diffraction (GI‐XRD) is used to characterize the crystallographic dynamics of low molecular weight (LMW) and high molecular weight (HMW) poly(3‐hexylselenophene) (P3HS) films and blend films of P3HS with [6‐6‐]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) as a function of ‘step‐by‐step’ thermal annealing, from room temperature to 250 °C. The temperature‐dependent GIXRD data show how the melting point of P3HS crystallites is decreased by the presence of PCBM. P3HS crystallite domain sizes dramatically increase upon annealing to the P3HS melting temperature. The formation of well‐oriented HMW P3HS crystallites with the (100) plane parallel to the substrate (edge‐on orientation), when cooled from melt, are observed. We compare the behaviour of P3HS pure and blend films with that of poly(3‐hexyl)thiophene (P3HT) pure and PCBM blended films and suggest that the similar temperature dependent behaviour we observe may be a common to polythiophene and related polymers and their blends.

     

Development of forensic analytical chemistry method for examination of Merla by thermal analysis and high resolution gas chromatography

The objective of this work is the TG and DSC analysis of “Merla” samples as well as the separation and identification of organic compounds by Ultra Fast GC method. The obtained results showed the grouping and the establishment of the degree of the sample’s similarity based in the Euclidean Distance. The cluster was a useful tool to determine if the samples, confiscated from different users by police, were manufactured in the same or different laboratories. Consequently one can conclude if in any city operates one or more drug manufacturing laboratories.     

Semisynthesis of a Homogeneous Glycoprotein Enzyme: Ribonuclease C: Part 1

Seven in one blow : The efficient formation of mixed disulfides on the thiol‐rich fusion protein A followed by subsequent intein cleavage gave the fragment B with all seven cysteines protected against oxidation. The native chemical ligation of B with synthetic glycopeptide thioesters provides glycoproteins.

     

Liquid–liquid microextraction methods based on ultrasound-assisted emulsification and single-drop coupled to gas chromatography–mass spectrometry for determining strobilurin and oxazole fungicides in juices and fruits

Two procedures are proposed based on ultrasound-assisted emulsification and single-drop liquid–liquid microextraction for the sensitive determination of seven strobilurin and six oxazole fungicides in fruits and juice samples. Both miniaturized techniques are coupled to gas chromatography with mass spectrometry in the selected ion monitoring mode, GC–MS(SIM). The procedures use low density organic solvents, and several factors influencing the emulsification, extraction and collection efficiency are optimized. The detection limits obtained at a signal-to-noise ratio of 3 are below the MRLs set by the European Commission. Enrichment factors are between 140–1140 for the first technique used and 80–1600 for the latter. The recoveries obtained for spiked samples are satisfactory for all compounds. The methods are validated according to the Commission Decision 2002/657/EC. Different fruit and juices are analyzed by the proposed method and none of the samples contained fungicide residues above the detection limits.     

Self-assembled films from WO3: Electrochromism and lithium ion diffusion

WO₃/chitosan and WO₃/chitosan/poly(ethylene oxide) (PEO) films were prepared by the layer-by-layer method. The presence of chitosan enabled PEO to be carried into the self-assembled structure, contributing to an increase in the Li⁺ diffusion rate. On the basis of the galvanostatic intermittent titration technique (GITT) and the quadratic logistic equation (QLE), a spectroelectrochemical method was used for determination of the “optical” diffusion coefficient (D_op), enabling analysis of the Li⁺ diffusion rate and, consequently, the coloration front rate in these host matrices. The D_op values within the WO₃/chitosan/PEO film were significantly higher than those within the WO₃/chitosan film, mainly for higher values of injected charge. The presence of PEO also ensured larger accessibility to the electroactive sites, in accordance with the method employed here. Hence, this spectroelectrochemical method allowed us to separate the contribution of the diffusion process from the number of accessible electroactive sites in the materials, thereby aiding a better understanding of the useful electrochemical and electrochromic properties of these films for use in electrochromic devices.     

Data-dependent neutral gain MS<Superscript>3</Superscript>: Toward automated identification of the N-Oxide functional group in drug metabolites

We report here an automated method for the identification of N-oxide functional groups in drug metabolites by using the combination of liquid chromatography/tandem mass spectrometry (LC/MS ⁿ ) based on ion-molecule reactions and collision-activated dissociation (CAD). Data-dependent acquisition, which has been readily utilized for metabolite characterization using CAD-based methods, is adapted for use with ion-molecule reaction-based tandem mass spectrometry by careful choice of select experimental parameters. Two different experiments utilizing ion-molecule reactions are demonstrated, data-dependent neutral gain MS³ and data-dependent neutral gain pseudo-MS³, both of which generate functional group selective mass spectral data in a single experiment and facilitate increased throughput in structural elucidation of unknown mixture components. Initial results have been generated by using an LC/MS ⁿ method based on ion-molecule reactions developed earlier for the identification of the N-oxide functional group in pharmaceutical samples, a notoriously difficult functional group to identify via CAD alone. Since commercial software and straightforward, external instrument modification are used, these experiments are readily adaptable to the industrial pharmaceutical laboratory.     

A simple and efficient synthesis of functionalized cyclic carbonate monomers using a versatile pentafluorophenyl ester intermediate

An improved two-step synthetic route to functionalized cyclic carbonate monomers that features a novel cyclic carbonate intermediate with an active pentafluorophenyl ester group (MTC-OPhF(5)) has been developed. The versatile pentafluorophenyl ester intermediate can be synthesized on the gram to kilogram scale in one high-yielding step and is easy to store and handle on the benchtop. The active pentafluorophenyl ester of MTC-OPhF(5) is amenable to further substitution with suitable nucleophiles such as alcohols and amines to generate functionalized cyclic carbonates in high yields. The substitution reaction is tolerant of a wide variety of functionalities, including various hydrophobic and hydrophilic groups, reactive functionalities (via thiol-ene click chemistry or alkyl halides), and protected acids, alcohols, thiols, and amines. In view of the ever-increasing need for biodegradable and biocompatible polymers, this new methodology provides a simple and versatile platform for the synthesis of new and innovative materials.     

Compatibility of quantum dots with immunobuffers, and its effect on signal/background of quantum dot-based immunoassay

In this work, the compatibility of quantum dots (QDs) with immunobuffers was studied by investigating the fluorescence stability of QDs in immunobuffers (in this research immunobuffers were defined as buffers for immunoaffinity binding or separation). Experimentally, the fluorescence signals of QDs with different surface chemistries (amine-terminated, streptavidin-coated, or antibody-conjugated) in commonly used immunobuffers were monitored versus time. The effect of some buffer composition on the compatibility of QDs with these buffers was also explored. Based on experimental data, the QD compatibility with these buffers is summarized, and it is found that a trace amount of bovine serum albumin added to most of these buffers helps QDs to achieve compatibility with them. Moreover, with QD as fluorescence label and C-reactive protein as a model analyte, a magnetic bead-based assay was performed using compatible and incompatible QD–immunobuffer systems. It is shown that compatible QD–immunobuffer systems can be used to achieve a higher assay signal/background ratio.      

Recent advances and applications of iridium-catalysed asymmetric allylic substitution

Since their discovery in 1997, iridium-catalysed asymmetric allylic substitutions have been developed into a broadly applicable tool for the synthesis of chiral building blocks via C-C and C-heteroatom bond formation. The remarkable generality of these reactions and the high levels of regio- and enantioselectivity that are usually obtained in favour of the branched products have been made possible by a thorough investigation of the catalyst system and its mode of action. Therefore, today the Ir-catalysed asymmetric allylic substitution is a powerful reaction in the organic chemist's repertoire and has been used extensively for several applications. This article aims to provide an overview of the development of iridium catalysts derived from an Ir salt and a chiral phosphoramidite and their application to the enantioselective synthesis of natural products and biologically relevant compounds.