Electrochemical sensing based on DNA nanotechnology

Electrochemical sensing is one of the major areas in analytical chemistry, since it is easy, reliable, and cheap compared to other analytical techniques. In this way, using DNA to develop novel electrochemical sensing devices bring many advantages compared to other biomolecules. However, the electrochemical properties of DNA are still under discovery. Herein we show three different properties of DNA, which were already studied by electrochemistry, and that can be further explored: (1) the DNA conductivity, derived from the base pair stacking enabling DNA to be a molecular wire; (2) DNA computing, derived from the interaction between different DNA sequences enabling the performance of logic to perform analytical operations; and (3) DNA self-assembly, due to base pairing, DNA can form nanostructures that can provide better electrochemical control. Finally, some perspectives for the topic will be discussed, focusing mainly in the interdisciplinary use of DNA nanostructures in electrochemistry118597605CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP306029/2014-6; 465389/2014-72014/50867-3; 2013/22127-2; 016/14507-8; 2018/178316; 2017/05213-

In situ X-ray diffraction investigation of hydrogen storage alloys during charge and discharge

Metal hydride electrodes have shown to be useful both in secondary batteries, e.g. the Ni/metal hydride system, and more recently in fuel cells, especially for direct borohydride fuel cells. This work provides in situ X-ray diffraction (XRD) results aiming at characterizing the phase transitions of the LaNi4.7Sn0.2Cu0.1 metal hydride alloy with and without Pt in the particle surface when charged electrochemically and chemically by exposition to a borohydride solution. Results have shown that the method of alloy charging leads to different phase predominance and different site occupancies, but both methods lead to almost the same discharge capacity. In the electrolysis process, ?-? phase transitions are predominant during the charge/discharge, while in the chemical charging by exposure to a borohydride solution the ?-? phase transition is more important, indicating occurrence of smaller localized stress in the alloy, with benefit on the material lifetime. Essentially the same phenomena were observed for the alloy with Pt, either with respect to the alloy structure and the electrochemical characteristics

Emerging considerations for the future development of electrochemical paper-based analytical devices

Meeting the current needs for easier, more precise and faster analyses that also follow the principles of green analytical chemistry requires novel analytical chemistry strategies. Since the appearance in this century of the first device based on a paper platform, many studies have been presented in the literature, providing a wide range of designs and possibilities for the application of paper platforms to electroanalytical systems. This Review gives an overview of the field and can pave the way for the future development of electrochemical paper-based analytical devices. We also present a critical point of view regarding what has been investigated and developed and what is still missing. This Review discusses the efforts made in the field related to important topics such as the choice of the paper substrate, the device construction process, the characterization of the device, and applications in different areas. In this way, we indicate some steps necessary for optimizing the design of the devices, with a focus on multidisciplinary collaborations that could move entire systems from the bench of the laboratory to the field611030CNPQ - Conselho Nacional de Desenvolvimento Científico e TecnológicoFAPESP – Fundação de Amparo à Pesquisa Do Estado De São Paulo434303/2016-02014/50867-3; 2013/22127-2; 2016/08166-3; 2016/14507-8; 2017/05213-

Pd–M/C (M = Pd, Cu, Pt) Electrocatalysts for Oxygen Reduction Reaction in Alkaline Medium: Correlating the Electronic Structure with Activity

The increasing global needs for clean and renewable energy have fostered the design of new and highly efficient materials for fuel cells applications. In this work, Pd–M (M = Pd, Cu, Pt) and Pt nanoparticles were prepared by a green synthesis method. The carbon-supported nanoparticles were evaluated as electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium. A comprehensive electronic and structural characterization of these materials was achieved using X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Their electrochemical properties were investigated by cyclic voltammetry, while their activities for the ORR were characterized using steady-state polarization experiments. The results revealed that the bimetallic nanoparticles consist of highly crystalline nanoalloys with size around 5 nm, in which the charge transfer involving Pd and M atoms affects the activity of the electrocatalysts. Additionally, the samples with higher ORR activity are those whose d-band center is closer to the Fermi level