Current commercial fuel cells operate in acidic media where Pt-containing compositions have been shown to be the best oxygen reduction reaction (ORR) electrocatalysts, due to their facile reaction kinetics and long-term stability under operating conditions. However, with the development of alkaline membranes, alkaline fuel cells have become a potentially viable alternative that offers the possibility of using Pt-free (precious metal-free) electrocatalysts. However, the search for better electrocatalysts can be very effort-consuming, if we intend to test every potential bi- or tri-metallic combination. In this work, we have explored the application of physical vapor deposition using a custom-built getter co-sputtering chamber to prepare catalyst thin films on glassy carbon electrodes, enabling catalyst compositions to be screened in a combinatorial fashion. The activity of combinations containing Au, Cu, Ag, Rh, and Pd as binary metal catalysts, in alkaline media, was studied using rotating disk electrode (RDE) voltammetry with an exchangeable disk electrode holder. Subsequently, we investigated a composition gradient of Pd-Cu, the best performing bimetallic catalyst thin film identified in the initial screening tests. Our results show the viability of using metal getter co-sputtering as a rapid and effective tool for preliminary testing of ORR fuel cell electrocatalysts.
Electromanipulation and electrical characterization of cancerous cells is becoming a topic of higher interest as the results reported to date demonstrate a good differentiation among various types of cells from electrical viewpoint. Dielectrophoresis (DEP) and broadband dielectric spectroscopy (BDS) are complimentary tools for sorting, identification and characterization of malignant cells and were successfully used on both primary tumor cells and culture cells as well. However, the literature is presenting a plethora of studies in respect to electrical evaluation of this type of cells and this paper is reporting a collection of information regarding the functioning principles of different types of dielectrophoresis set-ups, theory of cancer cells polarization and electrical investigation (including here the polarization mechanisms). The interpretation of electrical characteristic against frequency is discussed in respect to interfacial/Maxwell Wagner polarization and the parasitic influence of electrode polarization. Moreover, the electrical equivalent circuits specific to biological cells polarizations are discussed for a good understanding of cells' morphology influence. The paper also focuses on advantages of specific low-conductivity buffers employed currently for improving the efficiency of dielectrophoresis and provides a set of synthesized data from literature highlighting clear differentiation between the crossover frequencies of different cancerous cells.
We investigated the yield and distribution of macrocyclic products formed in combinatorial libraries (CLs) obtained via double-amidation reactions of methyl diesters with α,ω-diamines. The application of the static combinatorial chemistry (SCC) approach allowed us to generate a large number of macrocyclic diamides and tetraamides in single experiments. We show that high-pressure conditions accelerate the macrocyclization process but also have a great impact on the distribution of macrocyclic products in the presented libraries, promoting the formation of macrocyclic compounds and eliminating the linear ones. The distribution of macrocyclic products was also found to be strongly dependent on the structural features of the substrates employed. Furthermore, in three- and four-substrate CLs we observed the formation of a new type of hybrid tetraamides consisting of three different components.
Herein, we describe the development of a practical catch-and release methodology utilizing a cationic, amphiphilic PEG-based polymer to perform chemical transformations on immobilized DNA conjugates under anhydrous conditions. We demonstrate the usefulness of our APTAC (amphiphilic polymer-facilitated transformations under anhydrous conditions) approach by performing several challenging transformations on DNA-conjugated small molecules in pure organic solvents: the addition of a carbanion equivalent to a DNA-conjugated ketone in tetrahydrofuran, the synthesis of saturated heterocycles using the tin (Sn) amine protocol (SnAP) in dichloromethane and the dual-catalytic (Ir/Ni) metallaphotoredox decarboxylative cross-coupling of carboxylic acids to DNA-conjugated aryl halides in DMSO. In addition, we demonstrate the feasibility of the latter in multititer-plate format.
Adleman's illustration of molecular computing using DNA paved the way toward an entirely new direction of computing (Adleman, L. M. Science 1994, 266, 1021). The exponential time complex combinatorial problem on a traditional computer turns out to be a separation problem involving a polynomial number of steps in DNA computing experiments. Despite being a promising concept, the implementations of existing DNA computing procedures were restricted only to the smaller size formulations. In this work, we demonstrate a structure assisted DNA computing procedure on a bigger size Hamiltonian cycle problem involving 18 vertices. The developed model involves the formation and digestion of circular structure DNA, iteratively over multiple stages to eliminate the incorrect solutions to the given combinatorial problem. A high accuracy is obtained compared to other structure assisted models, which enable one to solve the bigger size problems.
