Oxygen reduction reaction features in neutral media on glassy carbon electrode functionalized by chemically prepared gold nanoparticles

Gold nanoparticles (AuNPs) were prepared by chemical route using four different protocols by varying reducer, stabilizing agent, and solvent mixture. The obtained AuNPs were characterized by transmission electronic microscopy (TEM), UV-visible, and zeta potential measurements. From these latter, surface charge densities σ were calculated to evidence the effect of the solvent mixture on AuNP stability. The AuNPs were then deposited onto glassy carbon (GC) electrodes by drop casting, and the resulting deposits were characterized by cyclic voltammetry (CV) in H₂SO₄ and field emission gun scanning electron microscopy (FEG-SEM). The electrochemical kinetic parameters of the four different modified electrodes toward oxygen reduction reaction (ORR) in neutral NaCl-NaHCO₃ media (0.15 M/0.028 M, pH 7.4) were evaluated by rotating disk electrode voltammetry and subsequent Koutecky-Levich treatment. Contrary to what we previously obtained with electrodeposited AuNPs [Gotti et al., Electrochim. Acta 2014], the highest cathodic transfer coefficients β were not obtained on the smallest particles, highlighting the influence of the stabilizing ligand together with the deposit morphology on the ORR kinetics.     

The strange-quark distribution

We discuss the latest CCFR determination of the strange sea density of the proton. We comment on the differences with a previous, leading-order, result and point out the relevance of quark mass effects and current non-conservation effects. By taking them into account it is possible to solve the residual discrepancy with another determination of the strange-quark distribution. Two important sources of uncertainties are also analysed.     

Rapid and high-performance analysis of thyreostatic drug residues in urine using gas chromatography-mass spectrometry

A more sensitive method was developed using the hyphenated technique of gas chromatography-mass spectrometry (GC-MS) supplementary to the official high-performance thin-layer chromatography (HPTLC) method. Even combined with less efficient extraction and clean-up methods, GC-MS is able to lower the detection limit to less than 50 ppb. The powerful technique of GC-MS-MS is tried out to reduce the detection limit even more, in combination with simplified extraction methods. This time-saving approach combined with the increase in sensitivity is of great importance for a routine technique.     

On the Conclusive Tests of Local Realism and Pseudoscalar Mesons

Many beautiful experiments have been addressed to test standard quantum mechanics against local realistic models. Even if a strong evidence favouring standard quantum mechanics is emerged, a conclusive experiment is still lacking, because of low detection efficiencies. Recently, experiments based on pseudoscalar mesons have been proposed as a way for obtaining a conclusive experiment. In this paper, we investigate if this result can effectively be obtained. Our conclusions, based on a careful analysis of the proposed set ups, are that this will not be possible due to intrinsic limitations of these kind of experiments.     

Using multidimensional projection techniques for reaching a high distinguishing ability in biosensing

Recent advances in the control of molecular engineering architectures have allowed unprecedented ability of molecular recognition in biosensing, with a promising impact for clinical diagnosis and environment control. The availability of large amounts of data from electrical, optical, or electrochemical measurements requires, however, sophisticated data treatment in order to optimize sensing performance. In this study, we show how an information visualization system based on projections, referred to as Projection Explorer (PEx), can be used to achieve high performance for biosensors made with nanostructured films containing immobilized antigens. As a proof of concept, various visualizations were obtained with impedance spectroscopy data from an array of sensors whose electrical response could be specific toward a given antibody (analyte) owing to molecular recognition processes. In addition to discussing the distinct methods for projection and normalization of the data, we demonstrate that an excellent distinction can be made between real samples tested positive for Chagas disease and Leishmaniasis, which could not be achieved with conventional statistical methods. Such high performance probably arose from the possibility of treating the data in the whole frequency range. Through a systematic analysis, it was inferred that Sammon's mapping with standardization to normalize the data gives the best results, where distinction could be made of blood serum samples containing 10(-7) mg/mL of the antibody. The method inherent in PEx and the procedures for analyzing the impedance data are entirely generic and can be extended to optimize any type of sensor or biosensor.     

Deprotonative metalation of chloro- and bromopyridines using amido-based bimetallic species and regioselectivity-computed CH acidity relationships

A series of chloro- and bromopyridines have been deprotometalated by using a range of 2,2,6,6-tetramethylpiperidino-based mixed lithium-metal combinations. Whereas lithium-zinc and lithium-cadmium bases afforded different mono- and diiodides after subsequent interception with iodine, complete regioselectivities were observed with the corresponding lithium-copper combination, as demonstrated by subsequent trapping with benzoyl chlorides. The obtained selectivities have been discussed in light of the CH acidities of the substrates, determined both in the gas phase and as a solution in THF by using the DFT B3LYP method.     

Spatial solitons in chi(2) planar photonic crystals

We analyze light self-confinement induced by multiple nonlinear resonances in a two-dimensional chi(2) photonic crystal. With reference to second-harmonic generation in a hexagonal lattice, we show that the system can not only support two-color (1+1)D solitary waves with enhanced confinement and steering capabilities but also enable novel features such as wavelength-dependent soliton routing.     

The photophysical determination of the minimum hydrotrope concentration of aromatic hydrotropes

A method based on the aggregate to monomol emission ratio, I(aggr)/I(monomol), was used to determine the minimal hydrotropic concentration (MHC) of aromatic hydrotropes. The main advantage of this method is that it does not require the use of probes or other additives, which might disrupt the aggregation process. Also, it relies on spectrophotometric measurements, which are more sensitive and less arduous than others, like conductivity, light scattering and surface tension.