In this paper a novel supramolecular strategy to improve the efficiency of a voltammetric sensor to determine two biologically relevant molecules (epinephrine (EP) and uric acid (UA)) is presented. The strategy is based on the use of a glassy carbon electrode modified with a copper(II) complex ([Cu(H2dimpy)Cl]PF6) adsorbed on multi-walled carbon nanotubes (MWCNTs). The [Cu(H2dimpy)Cl]PF6/MWCNT composite-supported electrode was characterized by electrochemical impedance spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The electrocatalytic oxidation of EP and UA using the sensor was investigated by cyclic voltammetry and square wave voltammetry. Under optimized conditions, voltammetric peak currents showed a linear response for the EP and UA concentrations in the ranges 0.5-159.2 and 0.2-58.5 µmol L−1, whereas the limits of detection were 0.2 and 0.05 µmol L−1, respectively. The sensor was successfully applied in the selective and simultaneous determination of EP and UA in human urine samples. Thus, our results showed that the supramolecular strategy was successful to build an efficient sensor for simultaneous detection of these molecules in biological samples.

The water oxidation is the limiting step in the water-splitting process. Given this scenario, the development of new catalysts is essential in this field. The emergent demand is the use of Earth-abundant elements and catalysts with high performance under mild conditions. Because of this, catalysts such as Prussian Blue analogues (PBA) have been receiving a lot of attention in recent years. In addition, working under neutral conditions allows us to take advantage of the modification of conductive polymeric 3D printed electrodes (3DPE) with Prussian Blue. Thus, we described in this work the development of the polymeric 3D printed electrodes modified by cobalt-Prussian Blue and their performance in the water oxidation process. The 3D printed electrodes modified with Co3[Co(CN)6]2 (Co-Co PBA) have a Tafel slope of 343 mV dec−1 while those modified with Co3[Fe(CN)6]2 (Co-Fe PBA) have a Tafel slope of 378 mV dec−1. This means that both catalysts have the same mechanism for the water oxidation process. On the other hand, the overpotential of Co-Co PBA in 3DPE is lower than the value observed by Co-Fe PBA in 3DPE suggesting the best electrocatalytic activity for Co-Co PBA catalyst.

The increase in demand for both fast and inexpensive prototyping of objects, with a certain degree of resilience and durability, is the main reason why 3D printing has become part of the concept of industry 4.0 and it is omnipresent in research facilities and industries around the world. In this work, we describe step-by-step the construction process of a filament winder that can be adapted for many commercially available bench-size polymer extruders. The electronic circuit used to regulate the winding rate, and therefore the thickness of the filament, is completely based on simple open-code microcontrollers such as Arduino Uno. Finally, it is showed that using this system it is possible to obtain printable ABS filaments with a wide range of thicknesses and a margin of error of around 5%.

Poly(4-vinylpyridine) (P4VP) and P4VP/pentacyanoferrate(II) metallopolymer were used to suspend up to 1 mg mL-1 of multi-walled carbon nanotubes (MWCNT) in ethanol/water mixtures, providing noncolavent decoration of MWCNT with electroactive iron complex. The major interaction between polymer side chains and nanotubes is via π-π stacking, rather than charge-transfer interaction reported for many nitrogenated interacting molecules. Preservation of structural integrity of the nanotubes after functionalization was attested by Raman, which was reflected in the semiconducting character of the dried nanocomposites. Proximity of pentacyanoferrate(II) to MWCNT walls was suggested by its solvatochromic shift of metal-to-ligand charge transfer band attributed to [Fe(CN)5]3− bound to P4VP pyridyl moieties. Electronic microscopy revealed smooth films and good adhesion between MWCNT bundles and the matrix. The procedure described herein can be used to combine unique properties of transition metal compounds able to coordinate to pyridyl groups, with the film-forming ability of P4VP and conductivity provided by MWCNT.

Polímero híbrido derivado de siloxano e b-ciclodextrina (β-CD) foi obtido pela reação de β-CD com g-isocianatopropiltrietoxissilano (IPTS), seguido por reação de hidrólise/condensação, gerando uma resina de polissilsesquioxano modificada por β-CD (PSS-β-CD). PSS-β-CD foi caracterizado por espectroscopia infravermelho e ressonância magnética nuclear de 13C e 29Si. Este híbrido é amorfo e termicamente estável até 180 ºC. PSS-β-CD pode ser obtido também como filme e sua morfologia foi avaliada por microscopia eletrônica de varredura. A capacidade da β-CD ligada ao polímero em formar complexos de inclusão foi avaliada pela formação de um complexo de β-CD-fenolftaleína, utilizando espectroscopia UV-Vis. Mesmo sem mudanças no pH, a forma vermelha da fenolftaleína se converte na forma incolor quando PSS-β-CD é imerso na solução. Cálculos teóricos (métodos AM1 e DFT) mostram que o complexo é formado pela inclusão do anel fenolato na cavidade da β-CD favorecendo a forma incolor da fenolftaleína por mais de 15 kcal mol-1.

A hybrid polymer derived from siloxane and β-cyclodextrin (β-CD) was obtained by reaction of β-CD with g-isocyanatopropyltriethoxysilane (IPTS), followed by hydrolysis/condensation reactions, generating a β-CD-modified polysilsesquioxane resin (PSS-β-CD). PSS-β-CD hybrid was characterized by infrared spectroscopy and 13C and 29Si nuclear magnetic resonance. This hybrid was typically amorphous and thermally stable up to 180 ºC. PSS-β-CD was able to form films and its morphology was evaluated by scanning electron microscopy. The capability of β-CD grafted in the hybrid polymer to form inclusion complex was evaluated by the formation of a β-CD-phenolphthalein complex using UV-Vis spectroscopy. Even without changes in pH, the red form of phenolphthalein converts to the colorless one when PSS-β-CD is immersed in the solution. Theoretical calculations (AM1 and DFT methods) show that the complex is formed through the inclusion of the phenolate ring into β-CD cavity, favoring the colorless form of phenolphthalein by more than 15 kcal mol-1.