Juliano Alves Bonacin

Exploring the electrical wiring of screen-printed configurations utilised in electroanalysis

In this technical note the often overlooked issue of electrically connecting screen-printed electrode sensors is considered. The electrical connection of screen-printed electrodes to the potentiostat/electronics can be a main issue when a true electrochemical response is trying to be obtained and if one does not have a stable electrical connection, the results that are obtained may lack reproducibility and therefore maybe discredited as “another failed electrochemical probe/analyte”. This paper considers the case of electrically connecting screen-printed with crocodile clips and compares that to the use of edge-connectors demonstrating the precise connection of an electrode setup when utilising crocodile clips can result in extremely reproducible electrochemical outputs when applied correctly.

Rice Husk Reuse in the Preparation of SnO2/SiO2 Nanocomposite

In this study, biogenic SiO2 of high purity and high surface area obtained from rice husk was used for prepare a nanostructured SnO2/SiO2composite. The predominantly amorphous silica was extracted in an acidic route and then the nanocomposite was done via sol-gel route using ethylene glycol and citric acid followed by heat treatment. SiO2 content of the rice husk was determined by X-ray fluorescence (XRF) and its specific surface area determined by nitrogen adsorption. The composite nanostructured SnO2/SiO2 was structurally characterized by the techniques of X-ray diffraction (XRD), Raman and Fourier transform infrared (FT-IR) spectroscopy. The morphological characteristics were revealed by scanning electron microscope (SEM).

Unravelling the Chemical Morphology of a Mesoporous Titanium Dioxide Interface by Confocal Raman Microscopy: New Clues for Improving the Efficiency of Dye Solar Cells and Photocatalysts

The presence of anatase and rutile domains on nanocrystalline films of P25 TiO2, as well as the distinct coordination modes of carboxylates on those phases, were revealed by confocal Raman microscopy, a technique that showed to be suitable for imaging the chemical morphology down to submicrometric size.

Structural and morphological investigations of β-cyclodextrin-coated silver nanoparticles.

This paper describes the synthesis of silver nanoparticles using an aqueous silver nitrate solution in the presence of glucose as a reducing agent, sodium hydroxide as a reaction catalyst and β-CD as a stabilizer. The structure and the morphology associated to the stabilizing layer around the silver nanoparticles were investigated. Raman spectroscopy confirmed the nanoparticle surface modification by β-CD, demonstrating the interaction between the β-CD rim hydroxyl groups and the AgNP surface. Transmission electron microscopy images showed an average 28.0nm diameter pseudo-spherical nanoparticles. Apart from this, a novel characterization of the β-CD layer surrounding the nanoparticles was carried out by using complementary analytical electron microscopy based on electron spectroscopy imaging in the transmission microscope. Mapping images revealed the presence of carbon and oxygen, demonstrating the existence of a uniform and interacting β-CD layer covering the nanoparticles. The antibacterial activity was also investigated and the β-CD-coated silver nanoparticles showed a promising bactericidal activity against the microorganism Escherichia coli.

Stabilization of meso-tetraferrocenyl-porphyrin films by formation of composite with Prussian blue

Supramolecular systems based on porphyrin-ferrocene have attracted the attention to inorganic electrochemistry due to unique electronic properties and synergic behavior between porphyrin ring and peripheral ferrocene group. In order to improve the stability of the films of ferrocenyl-porphyrin on electrode’s surface, we used a combination of tetraferrocenylporphyrin and Prussian blue. The new structure formed was very stable and could be used in dopamine sensing, showing satisfactory analytical response comparable to other chemically modified electrodes the described in the literature.

Visible-Light-Driven Epoxyacylation and Hydroacylation of Olefins Using Methylene Blue/Persulfate System in Water

A visible-light-driven strategy for hydroacylation and epoxyacylation of olefins in water using methylene blue as photoredox catalyst and persulfate as oxidant is reported. In this unprecedented unified approach, two different transformations are accomplished using only one set of reagents. The method has a broad scope spanning a range of aromatic and aliphatic aldehydes as well as conjugated and nonconjugated olefins to deliver ketones and epoxyketones from abundant and inexpensive chemical feedstocks.

Utilização de processos fotoquímicos em óxido de grafeno para obtenção de hidrogênio

Resumo O gás hidrogênio é uma das mais importantes apostas para a produção de energia limpa no futuro. Ele pode ser obtido a partir da água pelo processo de water splitting, o qual consiste na irradiação de luz na presença de fotocatalisadores que provome a decomposição de água em hidrogênio e oxigênio. A redução fotoquímica de óxido de grafeno leva a produção de hidrogênio durante o processo de irradiação e, considerando o custo dos catalisadores empregados nesse processo, o óxido de grafeno (GO) pode ser uma alternativa economicamente viável. Nesse trabalho, estudamos a influência do comprimento de onda, da fonte de luz, do pH e do tempo de irradiação na fotoreduação do GO.

Electrocatalytic activity in sensing of nitrite by films produced by electropolymerization of [Fe(Br-ph-tpy)2]2+

Abstract Nitrite is a preservative agent broadly used in the food industry. Its excessive consumption can cause several diseases including cancer. Thus, the development of sensors for nitrite is indispensable for strict nitrite level control in industrialized products and consequently for human welfare. Herein, is presented a study of the modification of electrodes by electropolymerization of [Fe(Br-ph-tpy)2](PF6)2 and its use as electroactive films in sensing of nitrite. The films were characterized by cyclic voltammetry, electrochemical quartz crystal microbalance, atomic-force microscopy and they were employed in electroanalytical experiments. The film obtained by electropolymerization exhibited some fibers dispersed on the substrate, reflecting the formation polymers on the surface of the electrode. The electrodes were further improved by drop casting a film of the complex on a glass carbon electrode, and then performing the electropolymerization of the complex. An increase in stability and a 41% enhancement of the electrocatalytical response for nitrite ions have been observed, in comparison with the bare electrode.

Non-innocent behavior of 1-(2′-pyridylazo)-2-naphtholate coordinated to polypyridine ruthenium(II) complexes

The study of non-innocent redox behavior of ligands is important for the development of new catalysts and to comprehend the function of bioinorganic molecules in biochemical processes. In this work, we present a description of the non-innocent behavior of 1-(2′-pyridylazo)-2-naphtholate (pan) coordinated to ruthenium complexes. The synthesis and characterization of a series of [Ru(pan)(PPh3)(L)]PF6 complexes [where L = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (dmbpy), and 1,10-phenanthroline (phen)] are presented. UV–vis analyses of the studied ruthenium complexes show intense absorptions from intraligand π–π* and metal-to-ligand charge-transfer transitions bands in the visible region. This observation shows a significant contribution of the pan ligand in all electronic transitions and is the indicative of non-innocent behavior. Theoretical calculations were carried out to support the UV–vis spectral assignments. Non-innocent behavior of pan was observed and confirmed using the electrochemical parameter EL(L) and by electrochemical studies. The pan ligand is non-innocent and can be modulated by donor and acceptor character of the other ligands present in the coordination sphere of the complex. Graphical Abstract