Exploiting Micrometer-Scale Replication of Fungal Biotemplates for Multifunctional Uses in Electrochemistry and SERS Substrates Verônica B. Maciel, Adriana M. Fontes, Regina Geris, Zênis N. da Rocha, Jéssica G. S. Ramalho, et al. ACS Omega, 2024 In this paper, filamentous fungi have been used as biotemplates to integrate gold nanoparticles (Au-NPs) into the cell wall. A new chemical mechanism has been proposed to elucidate the assimilation of Au-NPs by fungi, considering the ionic current that arises in the function of fungal metabolism. After biological components were eliminated, mycelium-like gold microtubes have been obtained using different fungal species as precursors. Mycelium-like gold microtubes replicate the biological shape of fungi, presenting inherent multifunctionality. This work presents two promising applications for this material: high surface area electrodes for electrochemical experiments and substrates for SERS detection of organic molecules such as Rhodamine 6G.
Supported metallocenes produced by a non-hydrolytic sol-gel process: Application in ethylene polymerization Arthur A. Bernardes, Guilherme L. Scheffler, Claudio Radtke, Dirce Pozebon, João H.Z. dos Santos, et al. Colloids and Surfaces A Physicochemical and Engineering Aspects, 2020 The immobilization of Cp2ZrCl2 was performed by entrapment within the binary oxides SiO2-CrO3, SiO2-MoO3 and SiO2-WO3 using a non-hydrolytic sol-gel route. Catalyst performance was evaluated in ethylene polymerization. The highest catalyst activity was found with a lower metal chloride:Si ratio and catalyst bearing W moieties. The catalyst and oxide matrices were characterized by complementary techniques (nitrogen porosimetry, small angle X-ray scattering, Fourier Transform infrared spectroscopy, X-ray photoelectron spectroscopy, and differential pulse voltammetry). The interaction between the binary oxide support and the immobilized metallocene reduced the electron density on the Zr centers, enabling the activation reaction to occur with lower concentrations of the methylaluminoxane (MAO) co-catalyst (Al/Zr = 500). The catalytic activity showed a direct relationship with the size and shape of the mass fractal. The results demonstrate that the entrapping method allows for the generation of a catalyst system in which part of the activation process may be attributed to the support.
Solvent-free synthesis of modified zeolites using hybrid silicas as raw material Alan dos Santos da Silva, Zenis Novais da Rocha, Marcelo Luis Mignoni, João Henrique Z. dos Santos Microporous and Mesoporous Materials, 2019 The use of hybrid silicas as the silica source in solvent-free zeolite synthesis was investigated as an alternative approach to obtain hybrid aluminosilicates without postsynthetic modification. Hybrid silicas bearing alkyl, amino and mercapto groups were produced by acid catalysis, base catalysis, two-step and silicate sol-gel routes. The influence of the structure and chemical nature of the hybrid silica source on zeolite formation under solvent-free conditions was evaluated. Zeolites based on the silicas synthesized by acid catalysis, base catalysis, two-step, and silicate sol-gel routes showed 51, 100, 18 and zero percent crystallinity, respectively. Furthermore, increasing the alkyl chain from a methyl to an octyl or octadecyl loaded onto the hybrid silica increased the time needed to obtain a crystalline structure from 24 h to 48 or 72 h, respectively. For all the systems, a zeolite sodalite was obtained. Thus, the results show the influence of the structural and chemical nature of the silica source on the crystallization process while keeping the sodalite arrangement for all of the conditions.
Chemically modified silica-based sensors: Effect of the nature of organosilane Larissa Brentano Capeletti, Cristiane dos Santos, Zenis Novais da Rocha, Mateus Borba Cardoso, João Henrique Zimnoch dos Santos Sensors and Actuators B Chemical, 2019 The use of organosilanes to produce hybrid materials, also known as ORMOSILs (organically modified silicas) can be a good strategy to tune a material’s properties, enabling, for example, the optimization of important features of chemical sensors such as specificity, sensitivity and response time. Thus, different hybrid silicas were prepared by the sol-gel method to be employed as a colorimetric sensor. The investigated organic groups for producing hybrid materials included methyl, octyl, octadecyl, vinyl, phenyl, aminopropyl, isocyanatopropyl, mercaptopropyl, chloropropyl, iodopropyl and glycidoxypropyl groups, and the pH indicator alizarin red was used as the encapsulated receptor element. The sensors were characterized using a set of complementary techniques such as UV–vis spectroscopy, cyclic and differential pulse voltammetry, nuclear magnetic resonance, nitrogen porosimetry, small-angle X-ray scattering and transmission electronic microscopy. The performance was evaluated according to the color change (ΔE*ab) by conducting a colorimetric analysis and measuring the response time after ammonia exposure, with results varying from 48 to 95 s. Additionally, other characteristics of the hybrid materials, such as their surface area, reticulation degree, texture and morphologic properties, were altered depending on the organic modification present in the silica network. The potentiality for material optimization, to achieve better sensor performance, depends on the employed organosilane.
Dibrominated camphoric acid derived salen complexes: Synthesis, characterization and cytotoxic activity M. Elisa Silva Serra, Dina Murtinho, Zênis N. da Rocha, Ana Salomé Pires, João Gabriel Baptista, et al. Polyhedron, 2017 Novel brominated salen metal complexes from (1R,3S)-N,N′-bis[5-bromosalicylidene]-1,3-diamino-1,2,2-trimethylcyclopentane and Cu(II), Fe(III) and Mn(III) were synthesized and screened for their in vitro cytotoxic activity against two breast cancer cell lines, HCC1806 and MCF7, and two colon cancer cells lines, LS1034 and WiDr. Results show that the copper complex exhibits the highest cytotoxic activity towards all cell lines studied, presenting IC50 values of 0.95–2.32 μM. The anti-proliferative effect observed with the copper complex constitutes a marked improvement relative to current conventional chemotherapy. A relationship between the biological activity of the most efficient Cu(II) complex and its structure is established using theoretical calculations and electrochemical studies.
Electrochemical and Catalytic Studies of a Supported Photocatalyst Produced from Petrochemical Residue in the Photocatalytic Degradation of Dexamethasone and Guaifenesin Drugs William Leonardo da Silva, Marla Azário Lansarin, João Henrique Z. dos Santos, Zenis N. Da Rocha, Iuri Muniz Pepe Water Air and Soil Pollution, 2016 Dexamethasone and guaifenesin were comparatively degraded under UV and visible radiation in the presence of a supported photocatalyst generated from petrochemical residue. For comparative reasons, photochemical tests were also conducted in the presence of commercial titania (P25). The photoelectrochemical behavior of the supported photocatalyst was examined using cyclic voltammetry and differential pulse voltammetry in the dark and under LED irradiation. This photodegradation study indicates the highest drug degradation values were observed for guaifenesin under UV (48.6 %) and visible (45.2 %) radiation with the synthesized photocatalyst. Under the same conditions, the commercial P25 catalyst achieved 66.3 and 50.2 % of the degradation under UV and visible radiation, respectively. Exploratory tests with tap water samples revealed that the system may be sensitive to other analytes present in these environmental samples.
The versatile ruthenium(II/III) tetraazamacrocycle complexes and their nitrosyl derivatives Fabio Gorzoni Doro, Kleber Queiroz Ferreira, Zênis Novais da Rocha, Giovanni Finoto Caramori, Anderson Jesus Gomes, et al. Coordination Chemistry Reviews, 2016 Macrocyclic ligands are relevant because of the properties they impart to transition metal complexes, such as enhanced thermodynamic stability and slowed substitution kinetic behavior. Here, we address issues not previously reviewed, revisit others, present new results, and review and discuss the results obtained in the last decade for ruthenium(II/III) complexes with tetraazamacrocycles (mac) such as cyclam (1,4,8,11-tetraazacyclotetradecane), [RuL1L2(mac)]q+ with emphasis on nitrosyls. Topics include synthesis, macrocycle functionalization, structure, spectroscopy, photochemistry, reactivity, density functional theory calculations, and biological properties. [RuL1L2(mac)]q+ complexes exhibit a rich chemistry, sometimes unusual, which depends on macrocycle ring size, the presence of N- or C-pendant groups, metal oxidation state, electronic structure, and the nature of L1 and L2. These same features can be used to tune the properties of the complexes leading to potential applications in diverse fields.
Polyethylene-polyaniline nanofiber composites: Evaluation of experimental conditions of in situ polymerization Ana Paula Graebin, Leila Bonnaud, Olivier Persenaire, Oltea Murariu, Philippe Dubois, et al. Materials Research, 2015 The difficult processability of polyaniline (PAni) can be overcome by preparing composites with high density polyethylene (HDPE), resulting in a conducting material with improved mechanical properties. PAni nanofibers were synthesized in this research using a rapid mixing method, while HDPE/PAni composites were prepared by in situ polymerization using Cp2ZrCl2/MAO as a catalyst system. Different experimental conditions for polymerization and an electrochemical study were performed. The findings confirmed that the addition of small amounts of Pani (up to 7%) and longer impregnation (120 min) with methylaluminoxane (MAO) before polymerization are important factors contributing to increased catalytic activity. Analysis by cyclic and differential pulse voltammetry indicates that MAO reacts with the PAni in the ethylene polymerization process, and forms active species in the presence of the catalyst. Changes in catalytic activity may be due to the kinetic consumption of the active species, which become less important in the presence of PAni.
