The application of scanning electrochemical microscopy to the discovery of Pd–W electrocatalysts for the oxygen reduction reaction that demonstrate high activity, stability, and methanol tolerance

An array of Pd–W alloys was fabricated, and the electrocatalytic activity of the alloys for the oxygen reduction reaction (ORR) in acidic media was screened by scanning electrochemical microscopy. The Pd_0.7W_0.3 showed the highest activity for the ORR, close to that for Pd_0.8Co_0.2 and Pt. A Pd–W electrocatalyst loaded on carbon black was formed by the NaBH₄-reduction method, exhibiting high activity and stability, suggesting that it is a good candidate for the proton exchange membrane fuel cell cathode.     

Simultaneous Detection of Single Attoliter Droplet Collisions by Electrochemical and Electrogenerated Chemiluminescent Responses

We provide evidence of single attoliter oil droplet collisions at the surface of an ultra‐microelectrode (UME) by the observation of simultaneous electrochemical current transients (i–t curves) and electrogenerated chemiluminescent (ECL) transients in an oil/water emulsion. An emulsion system based on droplets of toluene and tri‐n‐propylamine (2:1 v/v) emulsified with an ionic liquid and suspended in an aqueous continuous phase was formed by ultrasonification. When an ECL luminophore, such as rubrene, is added to the emulsion droplet, stochastic events can be tracked by observing both the current blips from oxidation at the electrode surface and the ECL blips from the follow‐up ECL reaction, which produces light. This report provides a means of studying fundamental aspects of electrochemistry using the attoliter oil droplet and offers complementary analytical techniques for analyzing discrete collision events, size distribution of emulsion systems, and individual droplet electroactivity.     

From workplace air measurement results toward estimates of exposure? Development of a strategy to assess exposure to manufactured nano-objects

In the past few years, an increasing number of studies on workplace air measurements on manufactured nano-materials and -objects have been published. Most of the studies had a more explorative character, so a direct interpretation to workers” exposure for a given exposure situation, activity, or process is not a straight-forward process. In general, the studies use a quite similar package of devices for near real-time monitoring of particle number- and mass concentration in size ranges <100 nm up to 10 μm, and the collection of samples for off-line characterization of air samples. Various approaches for addressing background concentrations and its use to indicate the potential for exposure to nano-objects could be observed. Within the EU-sponsored NANOSH project, a harmonized approach for measurement strategy, data analysis and reporting was developed. In addition to time/activity–concentration profiles as reported by most studies, this approach enables a first step to estimate the potential for exposure to manufactured nano-objects, more quantitatively. The NANOSH data will be collated into a base, which may form the starting point for a harmonized database facilitating overall analysis in near future, to derive estimates for exposure for several exposure situations.     

Electrochemistry and electrogenerated chemiluminescence of organic nanoparticles

This review discusses briefly the preparation, electrochemistry, and electrogenerated chemiluminescence (ECL) as well as spectroscopic properties of organic nanoparticles. Organic nanoparticles, ranging from several tens of nanometers to hundreds of nanometers in diameter, were successfully prepared by various methods. Using a simple reprecipitation method, organic nanoparticles of a very small size can be prepared and show unique electrochemical and ECL characteristics. As with inorganic nanoparticles, organic nanoparticles suggest possible applications, like labels for the analysis of biological materials with ECL.     

An analysis of a rail car unloading area for a consumer products manufacturer

This paper reports on the results of an effort to design and analyse the rail car unloading area of Procter & Gamble's principal laundry detergent (soap powder) plant. In the first part of the study the design team established daily requirements for the number of raw material rail cars unloaded per day. The related combinatorial optimisation problem of assigning rail cars to positions on the platform and unloading equipment to rail cars was modelled as a mixed-integer nonlinear program. The inability of two standard commercial codes to find optimal solutions led to the development of a greedy randomised adaptive search procedure (GRASP). Accounting for the operational and physical limitations of the system, GRASP was used to determine the maximum performance that could be achieved under normal conditions. In the second part of the study alternative designs were proposed for meeting an expected 14% increase in demand over the next few years. The analytic hierarchy process in conjunction with a standard scoring model was used to rank the evaluation criteria and to select the preferred alternative. A worst-case analysis of the top candidate confirmed its performance capabilities.     

High-performance affinity chromatography of messenger RNA.

A 50-mer of thymidylic acid, (dT)50, was coupled to silica inside prepacked columns using the N-hydroxysuccinimide chemistry. The resulting (dT)50-silica columns were used to resolve oligomers of adenylic acid, (dA)19-24, and to separate poly(A) mRNA (messenger RNA) from Saccharomyces. Oligomers which differed in length by a single nucleotide base were readily resolved. Using either (dT)50- or (dT)18-silica, poly(A) mRNA could be purified in as little as 8 min. The poly(A) mRNA isolated appeared to be full length and could be used directly for T4 RNA ligase and RNAse A and T1 enzymatic reactions. The (dT)50-silica column was used to fractionate total poly(A) mRNA by tail length. While the separation was primarily due to poly(A) tail length, most fractions appeared to contain multiple tail lengths. Whether this represents an intrinsic feature of the RNA or a limitation of the method is discussed. These studies show that polynucleotides in the kilobase size range can be separated rapidly and with good resolution on DNA-silica.     

Some properties of the bilevel programming problem

The purpose of this paper is to elaborate on the difficulties accompanying the development of efficient algorithms for solving the bilevel programming problem (BLPP). We begin with a pair of examples showing that, even under the best of circumstances, solutions may not exist. This is followed by a proof that the BLPP is NP-hard.This work was partially supported by a grant from the Advanced Research Program of the Texas Higher Education Coordinating Board.     

Chemical and electrochemical dimerization of BODIPY compounds: electrogenerated chemiluminescent detection of dimer formation

The electrochemistry of several difluoroboradiaza-s-indacene (BODIPY) compounds lacking substituent groups in the meso (8)- and/or 3 (α)-positions was investigated. Chemical and electrochemical dimerization was demonstrated, and the dimerization depended on the character of substitution. The chemical dimerization was achieved by oxidative coupling using FeCl(3) in CH(2)Cl(2) at 0 °C. The electrochemical dimerization proceeded via anodic oxidation to the radical cation and monitored by both cyclic voltammetry (CV) and electrogenerated chemiluminescence (ECL). An available open 3-position was important for the formation of the dimer. The resulting 3,3'-dimer produced a second peak in the CV oxidation and also the appearance of a longer wavelength ECL peak at 656 nm, which is considerably shifted from the parent peak at 532 nm. No dimerization was seen for BODIPY molecules in which only the meso 8-position was unsubstituted, either by chemical or electrochemical means, demonstrating that dimerization occurs at position 3.     

Coulometric titration of copper(II) with electro-generated chromium(II)

The current efficiency for the electrogeneration of chromium(II) for use as a coulometric titrant was studied for several supporting electrolytes. With a mercury cathode and a 0.1 M chromic sulfate-0.1 M potassium chloride medium, 0.8 to 2.8 mg of copper (II) in 110 ml of solution can be titrated using potentiometric end-point detection.