Size-dependent charge collection in junctions containing single-size and multi-size arrays of colloidal CdSe quantum dots

This paper describes the electrical characteristics of junctions composed of three-dimensional arrays of colloidal CdSe quantum dots (QDs) with tin-doped indium oxide (ITO)/poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) and eutectic Ga-In (EGaIn) electrodes. It focuses on a comparison of junctions containing QDs of one size to those of arrays containing QDs of multiple sizes. This comparison makes it possible to estimate the relative contributions of transport across various interfaces (e.g., between the QDs and between the QDs and the electrodes) to the observed electrical characteristics of the junction and to evaluate the dependence of these contributions on the locations of various sizes of QDs within the junction. The junctions were diodes, and their turn-on voltage depended on the size of the QDs next to the PEDOT:PSS. We describe this dependence using a Marcus model to estimate the barrier for charge transfer induced by the difference in energies between the orbitals of the QDs and the valence band of PEDOT:PSS.     

Safe, facile radical-based reduction and hydrosilylation reactions in a microreactor using tris(trimethylsilyl)silane

A highly efficient system for tris(trimethylsilyl)silane (TTMSS) mediated deoxygenation, dehalogenation and hydrosilylation reactions is described in a microstructured device; this convenient platform enables the scale up of radical-based processes.     

Application of asymmetric flow field-flow fractionation (AsFlFFF) coupled to inductively coupled plasma mass spectrometry (ICPMS) to the quantitative characterization of natural colloids and synthetic nanoparticles

A straightforward quantification method is presented for the application of asymmetric flow field-flow fractionation (AsFlFFF) combined with inductively coupled plasma mass spectrometry (ICPMS) to the characterization of colloid-borne metal ions and nanoparticles. Reproducibility of the size calibration and recovery of elements are examined. Channel flow fluctuations are observed notably after initiation of the fractionation procedure. Their impact on quantification is considered by using (103)Rh as internal reference. Intensity ratios measured for various elements and Rh are calculated for each data point. These ratios turned out to be independent of the metal concentration and total sample solution flow introduced into the nebulizer within a range of 0.4-1.2 mL min(-1). The method is applied to study the interaction of Eu, U(VI) and Th with a mixture of humic acid and clay colloids and to the characterization of synthetic nanoparticles, namely CdSe/ZnS-MAA (mercaptoacetic acid) core/shell-coated quantum dots (QDs). Information is given not only on inorganic element composition but also on the effective hydrodynamic size under relevant conditions. Detection limits (DLs) are estimated for Ca, Al, Fe, the lanthanide Ce and the natural actinides Th and U in colloid-containing groundwater. For standard crossflow nebulizer, estimated values are 7 x 10(3), 20, 3 x 10(2), 0.1, 0.1 and 7 x 10(-2) microg L(-1), respectively. DLs for Zn and Cd in QD characterization are 28 and 11 microg L(-1), respectively.     

Validated hemoglobin-depletion approach for red blood cell lysate proteome analysis by means of 2D PAGE and Orbitrap MS

The analysis of the cytosolic red blood cell (RBC) proteome is negatively affected by the high intracellular amount of hemoglobin complicating the detection of low-abundant cytosolic proteins. In this study, an alternative approach for the preparation of hemoglobin-depleted RBC lysates is presented, which was established in combination with downstream 2D PAGE analysis and Orbitrap MS. Hemoglobin removal was accomplished by using HemoVoid(TM) depletion reagent, which enabled a very efficient enrichment of low-abundant proteins by simultaneously reducing the hemoglobin concentration of the sample. After defining selected sample preparation protocol characteristics including specificity/selectivity, precision and linearity, a 2D reference map (pH 4-7) of the cytosolic RBC proteome was generated and a total of 189 different proteins were identified. Thus, the presented approach proved to be highly suitable to prepare reproducible high-resolution 2D protein maps of the RBC cytosol and provides a helpful tool for future studies investigating disease- or storage-induced changes of the cytosolic RBC proteome.     

Determination of Synacthen in human plasma using immunoaffinity purification and liquid chromatography/tandem mass spectrometry

Synacthen is a synthetic analogue to human adrenocorticotropin, which plays an important physiological role by stimulating production of cortisol. In sports, corticosteroids as well as releasing factors (corticotropins) are prohibited according to the regulations of the World Anti-Doping Agency, and the misuse of Synacthen has been reported several times. Hence, an assay enabling the detection of Synacthen in doping control samples has been developed using immunoaffinity chromatographic isolation of Synacthen from human plasma combined with a concentration of collected fractions using solid-phase extraction. Unambiguous determination of the target analyte was accomplished using microbore liquid chromatography/electrospray ionization tandem mass spectrometry. Diagnostic product ions such as m/z 223 were characterized using high-resolution/high-accuracy Orbitrap mass spectrometry and employed for triple quadrupole MS/MS analysis. The established assay requiring 2 mL of plasma allowed a lower limit of detection (LLOD) at 100 fmol/mL, a recovery of 97% and a precision at the LLOD < 20%. Authentic plasma samples obtained from a patient undergoing a standard short Synacthen test were used to prove the applicability of the developed procedure.