Paulo Roberto Martins

Herein, binary coordination compounds based on Ni-Gly/ZIF-67 and Ni-Gly/CoFe-ZIF-67 were employed as electrode materials for energy storage and water-splitting applications, respectively. The structure and morphology of the binary electrodes were characterized by XRD, XPS, and SEM. Electrochemical studies (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that the binary materials exhibited distinct electrochemical behavior for energy storage and water splitting. In fact, whereas Ni-Gly/ZIF-67 was used as an electrode material for energy storage, Ni-Gly/CoFe-ZIF-67 was used as an electrocatalyst for water splitting. The Ni-Gly/ZIF-67 electrode material achieved a high specific capacity of 106.9 mA h g–1 at 1.0 A g–1 and retained 71.6% of its capacity after 5000 cycles, combining pseudocapacitive/battery-type behavior. Furthermore, a symmetric supercapacitor device was assembled, achieving maximum energy and power densities of 0.765 W h kg–1 and 6076 W kg–1, respectively. The Ni-Gly/CoFe-ZIF-67 electrode material exhibited excellent oxygen evolution reaction (OER) activity, with an overpotential of 430 mV at 10 mA cm–2, a Tafel slope of 108 mV dec–1, and stable operation for 10 h. These results demonstrate a synergism between MOF- and Ni-Gly-derived frameworks, providing valuable insights for the rational design of sustainable multifunctional electrodes for integrated energy storage and conversion systems.

Despite being little explored for petroporphyrins recovery from oils and bituminous shales, adsorption and desorption processes can be feasible alternatives to obtain a similar synthetic material, and to characterize their original organic materials. Experimental designs were used to analyze the effects of qualitative (e.g., type of adsorbent, solvent, and diluent) and quantitative (e.g., temperature and solid/liquid ratio) variables on the adsorptive and desorptive performance regarding nickel octaethylporphyrin (Ni-OEP) removal using carbon-based adsorbents. The evaluation variables, adsorption capacity (q_e ) and desorption percentage (%_desorption ) were optimized by means of the Differential Evolution algorithm. The most efficient adsorbent for removing/recovery Ni-OEP was activated-carbon coconut shell, in which dispersive π-π type and acid-base interactions were likely formed. The highest values of q_e and %_desorption were obtained using toluene as solvent, chloroform as diluent, 293 K as temperature, and 0.5 mg.mL^-1 as solid/liquid ratio for adsorption, and a higher temperature (323 K) and lower solid/liquid ratio (0.2 mg.mL^-1) for desorption. The optimization process resulted in q_e of 6.91 mg.g^-1 and %_desorption of 35.2%. In the adsorption-desorption cycles, approximately 77% of the adsorbed porphyrins were recovered. The results demonstrated the potential of carbon-based materials as adsorbent materials for obtaining porphyrin compounds from oils and bituminous shales.

In this work, alpha-cobalt hydroxide (Co(OH)₂) and cobalt/manganese layered double hydroxide (CoMn-75-LDH) were synthesized using the Tower method. The alpha phase was confirmed for Co(OH)₂ through XRD analysis. Furthermore, the TEM images showed that the materials are formed by nanoparticles with an average size of ~5 nm. Cyclic voltammetry and galvanostatic charge/discharge measurements were carried out and the CoMn-75-LDH presented a superior electrochemical behavior to Co(OH)₂. The presence of Mn^2+/3+ ions in the crystal structure of CoMn-75-LDH, verified by XPS analysis, enhanced the electrical conductivity of the material, providing more electroactive sites, as a result, the electrochemical performance of the material was improved. Electrochemical studies showed that CoMn-75-LDH has a specific capacitance of 677 F g^-1 at current density of 0.5 A g^-1 compared to Co(OH)₂, whose specific capacitance value was 268.7 F g^-1 at the same current density. In addition, the electrochemical signature of Co(OH)₂ revealed that the electrode material exhibits an extrinsic pseudocapacitive behavior instead of the typical behavior of battery-type materials due to its nanostructured morphology. Also, electrochemical studies showed that the charge storage mechanism for CoMn-75-LDH is controlled by both the capacitive and diffusion process.

In this work, electrode materials based on ZnCo₂O₄for the HER/OER/ORR and energy storage devices were reviewed considering their key multifunctional role in the way to a more sustainable society.

Considering the demand for highly sensitive and selective electrochemical sensors, MOF-derived materials and their composites have demonstrated relevant advances in electrochemical sensing, as summarized in this review article.

Background: Breast cancer is one of the most common types among women. Its incidence progressively increases with age, especially after age 50. Platinum compounds are not efficient in the treatment of breast cancer, highlighting the use of other metals for the development of new chemotherapeutic agents. Objective: This paper aims to obtain three new ruthenium compounds that incorporate sulfur amino acids in their structures and to investigate their cytotoxic activity in breast tumor cell lines. Methods: Complexes with general formula [Ru(AA)(dppb)(bipy)] (complexes 1 and 2) or [Ru(AA)(dppb) (bipy)]PF6 (complex 3), where AA = L-cysteinate (1), D-penicillaminate (2), and L-deoxyalliinate (3), dppb = 1,4-bis(diphenylphosphino)butane and 2,2´-bipyridine, were obtained from the cis-[RuCl₂(dppb)(bipy)] precursor. The cytotoxicity of the complexes on MDA-MB-231 (triple negative human breast cancer); MCF-7 (double positive human breast cancer) and V79 (hamster lung fibroblast) was performed by the MTT (4,5- dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide) method. The control agent was the cisplatin, which is a commercially available drug for cancer treatment. Results: In complexes (1) and (2), the ligands are coordinated to the metal center by nitrogen and sulfur atoms, while in complex (3) coordination is through the oxygen and nitrogen atoms. These suggestions are based on the infrared and 31P1H NMR data. For complexes (1) and (2), their X-ray structures were determined confirming this suggestion. The three complexes are stable in a mixture of DMSO (80 %) and biological medium (20 %) for at least 48 h and presented cytotoxicity against the MDA-MB-231 and MCF-7 tumor cells with reasonable selectivity indexes. Conclusion: Our work demonstrated that ruthenium complexes containing sulfur amino acids, bipyridines and bisphosphines showed cytotoxicity against the MDA-MB-231 and MCF-7 cancer cell lines, in vitro, and that they interact weakly with the DNA (Deoxyribonucleic Acid) and the HSA (Human Serum Albumin) biomolecules.

Electrochemical and gas sensors based on MCo ₂ O ₄ (M = Ni, Fe, Mn, Cu and Zn) materials and their composites have demonstrated relevant advances on the electrochemical sensing, as summarized in this review article.