CdS-Enhanced Ethanol Selectivity in Electrocatalytic CO Reduction at Sulfide-Derived Cu-Cd.

The development of Cu-based catalysts for the electrochemical CO reduction reaction (eCO RR) is of major interest for generating commercially important C liquid products such as ethanol. Cu is exclusive among the eCO RR metallic catalysts in that it facilitates the formation of a range of highly reduced C products, with a reasonable total faradaic efficiency but poor product selectivity. Here, a series of new sulfide-derived copper-cadmium catalysts (SD-Cu Cd ) was developed.

Role of Electrochemistry in Desorption Ionization Mass Spectrometry (LS DESI MS) of Aqueous Samples Containing Electrolyte Salts.

The ionization of LS samples in desorption ionization mass spectrometry (LS DESI MS), supplied continuously through a LS interface separated in space from the spray emitter, was investigated in this work. The role of electrochemistry (EC) in the ionization process was addressed. The visual (observation) of the operation of the LS DESI MS system showed a thick spray plume generated by the electrosonic spray ionization (ESSI), forming a liquid cone at the LS interface.

Merits of online electrochemistry liquid sample desorption electrospray ionization mass spectrometry (EC/LS DESI MS).

A new online electrochemistry/liquid sample desorption electrospray ionization mass spectrometry (EC/LS DESI MS) system with a simple electrochemical thin-layer flow-through cell was developed and tested using N,N-dimethyl-p-phenylenediamine (DMPA) as a model probe. Although oxidation of DMPA is observed as a result of ionization of LS in positive ion mode LS DESI, application of voltage to the online electrochemical (EC) cell in EC/LS DESI MS increases yields of oxidation products. An advantage of LS DESI MS is its sensitivity in aqueous electrolyte solutions, which improves efficiency of electrochemical reactions in EC/LS DESI MS.

Nanomolar detection of p-nitrophenol via in situ generation of p-aminophenol at nanostructured microelectrodes.

A new method and a new buffer medium, expected to be practical for miniaturized electrochemical immunoassays, were developed for rapid detection of nanomolar levels of p-nitrophenol (p-NP). The method exploits rapid reduction of p-NP to p-aminophenol (p-AP) by fast scan cyclic voltammetry at 500 V s(-1) at nanostructured carbon fiber microdisk electrodes (~7 μm dia.) fabricated from polyacrylonitrile (PAN) fibers.

Structural characterization by infrared multiple photon dissociation spectroscopy of protonated gas-phase ions obtained by electrospray ionization of cysteine and dopamine.

Structural characterization of protonated gas-phase ions of cysteine and dopamine by infrared multiple photon dissociation (IRMPD) spectroscopy using a free electron laser in combination with theory based on DFT calculations reveals the presence of two types of protonated dimer ions in the electrospray mass spectra of the metabolites. In addition to the proton-bound dimer of each species, the covalently bound dimer of cysteine (bound by a disulfide linkage) has been identified. The dimer ion of m/z 241 observed in the electrospray mass spectra of cysteine has been identified as protonated cystine by comparison of the experimental IRMPD spectrum to the IR absorption spectra predicted by theory and the IRMPD spectrum of a standard.

Rapid measurements of 2,8-dihydroxyadenine (2,8-DHA) with a nanostructured electrochemical sensor in 5-fold diluted supernatants of endothelial cells exposed to oxidative stress.

Fast scan cyclic voltammetry (FSV) with a nanostructured carbon fiber sensor (N-CFS) was developed for direct measurements of the purine metabolite 2,8-dihydroxyadenine (2,8-DHA; i.e. 6-amino-1H-purine-2,8-dione) in endothelial cell supernatants as a marker of cell stress.

HPLC-UV measurements of metabolites in the supernatant of endothelial cells exposed to oxidative stress.

2,8-Dihydroxyadenine (2,8-DHA) was identified by high-performance liquid chromatography with ultraviolet detection as a major metabolite in the supernatant of endothelial cells of the pulmonary artery (PAECs) and aorta (AECs), in addition to hypoxanthine, xanthine, uric acid, and uracil. Under normoxic, hypoxic, and hyperoxic conditions, the concentrations of all the identified metabolites change with time, marking the response of endothelial cells to stress, as a result of changes in cellular metabolism. Thus, the metabolites can serve as stress markers, and their concentrations can indicate the type and the level of cell stress.

Direct measurements of xanthine in 2000-fold diluted xanthinuric urine with a nanoporous carbon fiber sensor.

High selectivity and sensitivity is reported in the measurements of xanthine in urine by fast scan cyclic voltammetry (FSV) with a nanostructured carbon fiber sensor of 3.5 +/- 0.4 mum radius.

Higher harmonic large-amplitude Fourier transformed alternating current voltammetry: analytical attributes derived from studies of the oxidation of ferrocenemethanol and uric acid at a glassy carbon electrode.

An analytical evaluation of the higher ac harmonic components derived from large amplitude Fourier transformed voltammetry is provided for the reversible oxidation of ferrocenemethanol (FcMeOH) and oxidation of uric acid by an EEC mechanism in a pH 7.4 phosphate buffer at a glassy carbon (GC) electrode. The small background current in the analytically optimal fifth harmonic is predominantly attributed to faradaic current associated with the presence of electroactive functional groups on the GC electrode surface, rather than to capacitive current which dominates the background in the dc, and the initial three ac harmonics.

Development of adenosine sensor: effect of physiological buffers on activity and sensitivity in adenosine determinations by fast scan voltammetry.

A new fast scan voltammetry (FSV) method was tested in the determinations of adenosine in physiological buffers at pH 7.4. The buffers can be used in the determinations of adenosine in vivo and include 7 x 10(-2) M phosphate, Krebs-Henseleit (K-H) and Hanks' Balanced Salts (HBSS).

Enhancement of ionization efficiency by electrochemical reaction products in on-line electrochemistry/electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

A miniaturized two-electrode electrochemical (EC) cell was developed and was coupled on-line with an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI-FTICR MS). Electrochemistry on-line with mass spectrometry, EC/ESI-FTICR MS, of triphenylamine (TPA), which undergoes one-electron oxidation to form a radical cation (TPA*+), demonstrates a significant sensitivity enhancement compared to ESI-FTICR MS. The on-line EC cell configuration with a stainless steel ES needle as the working electrode produces the highest sensitivity in EC/ESI-MS.