IQ - Artigos publicados em periódicos

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Seasonal changes of fructans in dimorphic roots of Ichthyothere terminalis (Spreng.) Blake (Asteraceae) growing in Cerrado
(2017) Almeida, Lorrayne Veloso de; Ferri, Pedro Henrique; Seraphin, Jose Carlos; Moraes, Moemy Gomes de
Cerrado is a floristically rich savanna in Brazil, whose vegetation consists of a physiognomic mosaic, influenced by rainfall seasonality. In the dry season rainfall is substantially lower and reduces soil water supply, mainly for herbs and subshrubs. Climatic seasonal variations may well define phenological shifts and induce fluctuations of plant reserve pools. Some Cerrado native species have thickened underground organs that bear buds and store reserves, as adaptive features to enable plant survival following environmental stresses. Asteraceae species accumulate fructans in storage organs, which are not only reserve, but also protecting compounds against the effects of cold and drought. Ichthyothere terminalis is one Asteraceae species abundant in cerrado rupestre, with underground organs consisting of thickened orthogravitropic and diagravitropic roots. The objectives of this study were to analyze how abiotic environmental factors and plant phenology influence fructan dynamics in field grown plants, and verify if fructan metabolism differs in both root types for one year. I. terminalis accumulates inulin-type fructans in 10–40% of the dry mass in both root types. Fructan dynamics have similar patterns described for other Asteraceae species, exhibiting a proportional increase of polysaccharides with the senescence of the aerial organs. Multivariate analyzes showed that, as rainfall decreased, environmental factors had a stronger influence on metabolite levels than phenological shifts in both root types. Only slight differences were found in fructan dynamics between orthogravitropic and diagravitropic roots, suggesting they may have similar fructan metabolism regulation. However, these small differences may reflect distinct microclimatic conditions in both root types and also represent the influence of sink strength.
Bioactive compounds of fruit parts of three Eugenia uniflora biotypes in four ripening stages
(2021) Santos, Suzana da Costa; Pereira, Marx Osório Araújo; Santos, Karoline Batista dos; Ferri, Pedro Henrique
Variability of secondary metabolites in edible (peel and pulp) and inedible (seeds) parts of three pitanga varieties, red, red-orange and purple, was investigated during the maturation process. Hydrolysable tannins, anthocyanins, and flavonoids were quantified by HPLC/DAD and carotenoids by absorbance. Peel/pulp showed greater complexity of constituents (carotenoids, anthocyanins, flavonoids, and hydrolysable tannins), while only tannins were identified in seeds, but in quantities of 10 to 100 times greater. The red-orange variety showed the highest levels of phenolic compounds in seeds and peel/pulp, except anthocyanins. The analysis of the principal response curves showed that the pitanga biotype has greater influence on metabolite variation than ripening stages. During peel/pulp maturation, a reduction in the levels of flavonoids and tannins contrasted with an increase in carotenoids and cyanidin-3-O-glucoside in all varieties, whereas in the seeds oenothein B, the major tannin, increased up to 1.32 g/100 g fresh weight. Such marked differences between fruit parts demonstrate that the seeds in stages E3 and E4 are a source of hydrolysable tannins, compounds known for their antitumor activity, while peel/pulp of all varieties in the ripe stage provide natural antioxidants, such as carotenoids and flavonoids. Lastly, the purple biotype can be a rich source of the cyanidin-3-O-glucoside pigment a potent bioactive compound.
Polyphenol and ellagitannin constituents of jabuticaba (Myrciaria cauliflora) and chemical variability at different stages of fruit development
(2017-02-07) Pereira, Luciane Dias; Barbosa, João Marcos Gonçalves; Silva, Antonio Jorge Ribeiro da; Ferri, Pedro Henrique; Santos, Suzana da Costa
A new ellagitannin named cauliflorin (1), seven known hydrolyzable tannins (2–8), and six known phenolics (9–14) were isolated from jabuticaba. Compounds 2–8 had not been previously isolated from M. cauliflora fruits. The jabuticaba fruit was analyzed at four developmental stages for ellagitannins 1, 3, 7, and 8, phenolic acids 11 and 12, anthocyanins, organic acids, and sugars via HPLC-UV-DAD and NMRq. The content of ellagitannins and organic acids declined during fruit development, whereas at full ripeness sugar and anthocyanin levels underwent a sharp increase and were mainly constituted by fructose and cyanidin-3-O-glucose, respectively. Ellagitannins’ profile varied considerably among fruit tissues, with pedunculagin (3), castalagin (7), and vescalagin (8) mostly concentrated in jabuticaba seeds, whereas cauliflorin (1) and anthocyanins accumulated in the peels. Changes in jabuticaba’s phenolic compound contents were mostly influenced by fruit part (peel, pulp, and seed) rather than by degree of ripeness.
Chemical composition and seasonal variation of the volatile oils from Trembleya phlogiformis leaves
(2017-04-30) Fernandes, Sarah Rodrigues; Ferreira, Heleno Dias; Sá, Stone de; Borges, Leonardo Luiz; Tresvenzol, Leonice Manrique Faustino; Ferri, Pedro Henrique; Santos, Pierre Alexandre dos; Paula, José Realino de; Fiuza, Tatiana de Sousa
Trembleya phlogiformis DC., Melastomataceae, is a shrub whose leaves are used as a dye for dyeing wool and cotton. The present article aimed to carry out the morphological description of the species, to study the chemical composition of volatile oils from the leaves and flowers and the seasonal variability from the leaves during a year. Macroscopic characterization was carried out with the naked eye and with a stereoscopic microscope. Volatile oils were isolated by hydrodistillation in Clevenger apparatus and analyzed by gas chromatography/mass spectrometry. The major components of the volatile oil of T. phlogiformis flowers were: n-heneicosane (33.5%), phytol (12.3%), n-tricosane (8.4%) and linoleic acid (6.1%). It was verified the existence of a large chemical variability of the volatile oils from the leaves of T. phlogiformis over the months, with the majority compound (oleic alcohol, ranging from 5.7 to 26.8%) present in all samples. A combination of Cluster Analysis and Principal Component Analysis showed the existence of three main clusters, probably related to the seasons. The results suggested that the volatile oils of T. phlogiformis leaves possess high chemical variability, probably related to variation associated with rainfall and the variation in the behavior of specimens throughout the year. This research provides insights for future studies on the volatile oils obtained from the T. phlogiformis leaves and flowers, mainly related to biological markers of applications monitored in the leaves and flowers of this species.
Viscosity of the oil-resins and chemical composition of the essential oils from oils-resins of Copaifera multijuga Hayne growing in the National Forest Saracá-Taquera Brazil
(2017-12-20) Silva, Marcos Tulio da; Borges, Leonardo Luiz; Fiuza, Tatiana de Sousa; Tresvenzol, Leonice Manrique Faustino; Conceição, Edemilson Cardoso da; Brandão, Celyane Batista; Matos, Caio Barros; Veiga Junior, Valdir Florencio da; Mourão, Rosa Helena Veras; Ferri, Pedro Henrique; Paula, José Realino de
Copaifera multijuga Hayne, Fabaceae, is a tree species Amazonian known as “mari mari” or “copaíba roxa”. Its oil-resins are popularly used for various medicinal purposes, especially as anti-inflammatory. The aims of this study were: determine the viscosity of the oil-resins and analyze the chemical composition of the essential oils from oils-resins of eleven specimens of C. multijuga. The essential oils were obtained by hydrodistillation using a Clevenger type apparatus and analyzed by GC/MS. The viscosity ranges from 9.46 to 92.62 mPa.s. for 11 samples of oil-resin. The compounds found in all samples were: β-caryophyllene (36.20 to 85.4%), α-humulene (4.15 to 11.26 %), δ-elemene (0.08 to 8.52 %), β-elemene (0.68 to 2.86 %), and ciprene (0.22 to 1.11 %). The compound trans-4-muurola (1,4), 5-diene was found only in higher amounts in samples 2, 6 and 7, ranging from 14.36 to 36.96 %. It was found that the higher levels of the viscosity are associated with lower contents of the β-caryophyllene. The β-caryophyllene was the major compound found in all samples, thus it can be used as the chemical marker of essential oil these specimens.
Chemovariations in Hypenia essential oils under infrageneric and phenological influences
(2022) Jesus, Camila Fernandes de; Faria, Maria Tereza; Ferreira, Heleno Dias; Ferri, Pedro Henrique
The essential oils (EOs) of six Hypenia species that are endemic in the central Brazilian Cerrado were assessed by GC/MS and chemometric analysis. EO variations according to two taxonomic sections, combined with two phenophases (vegetative and reproductive), showed that 23.2% of total variance was explained by such predictors. Variation partitioning showed that the largest pure contribution was attributed to section (43.7%), followed by phenophase (39.3%), with 17% of joint influence. A multivariate regression tree (MRT) indicated that 13 EO constituents may be potential chemomarkers for distinguishing sections and two developmental stages in the genus.
Review-Tetraruthenated porphyrins and composites as catalysts and sensor materials: a short review
(2020-07-20) Gonçalves, Josué Martins; Matias, Tiago Araújo; Angnes, Lucio; Martins, Paulo Roberto; Araki, Koiti
Electrocatalytic and photocatalytic materials for energy and sensor applications are among the most relevant ones to overcome the challenges for a sustainable society. In this context, metalloporphyrins and transition metal complexes are known to exhibit interesting complimentary properties that can be combined to provide synergic effects, which was achieved in what so called tetraruthenated porphyrins and derivatives. The properties of these supramolecular species can be tuned based on the transition metal ion coordinated to the porphyrin, the ruthenium complex and especially the electronic coupling between those species conferring enhanced photoelectrochemical activity for conversion of carbon dioxide in valuable reduced species, or nitrite/nitrate to less harmful species. Another major application was shown to be as sensor materials for several substrates, generating more sensitive and robust devices. However, such a coordination chemistry strategy is evolving leading to new composite, polymeric and hybrids materials based on carbon nanomaterials, as well as 2D and 3D porous materials, opening new perspectives on supramolecular porphyrin chemistry powered by the versatile coordination chemistry of transition metal ions and clusters. This short review revisits the interesting spectroelectrochemistry and applications of tetraruthenated porphyrins, expanding to the most recent works pointing towards auspicious new outcomes in near future.
Influence of cobalt content on nanostructured alpha-phase-nickel hydroxide modified electrodes for electrocatalytic oxidation of isoniazid
(2014) Martins, Paulo Roberto; Ferreira, Luís Marcos Cerdeira; Araki, Koiti; Angnes, Lucio
Fluorine doped tin oxide electrodes modified with nanostructured alpha nickel hydroxide, cobalt oxi-hydroxide and mixed alpha nickel/cobalt hydroxide electrodes were evaluated for determining isoniazid concentration by cyclic voltammetry (CV) and batch injection analyses (BIA) associated with amperometric detection. The different cobalt contents showed distinct features regarding isoniazid oxidation potential and current magnitude. The modified electrodes containing 25% cobalt presented about 3- and 7.5-fold greater sensitivity as amperometric isoniazid sensors than pure Ni(OH)2 electrodes, respectively for CV and BIA assays. This characteristic associated with high stability and reproducibility ensured BIA detection limits as low as 1.37 × 10−7, 5.19 × 10−8 and 4.94 × 10−8 mol L−1 for Ni-100, Ni-75 and Ni-50 electrodes respectively, as well as a high analyses throughput (about 400 h−1). The resulting electrodes are promising for other applications, once presents elevated sensitivity and the additional advantage of allow the researcher choose the best working potential, just varying the constitution of the modifier film.
Recent progress in ZnCo2O4 and its composites for energy storage and conversion: a review
(2022-10-03) Gonçalves, Josué Martins; Silva, Matheus Ireno da; Silva, Murillo Neia Thomaz da; Martins, Paulo Roberto; Nossol, Edson; Toma, Henrique Eisi; Angnes, Lucio
Transition metal oxides have attracted growing attention for application in energy storage and conversion technologies. In particular, spinel-based materials, such as ZnCo2O4, exhibit structures suitable for performing as multifunctional electrodes in energy devices. In fact, great efforts have been dedicated to the design of micro- and nanomaterials based on ZnCo2O4, using different synthesis approaches and controlled conditions. Consequently, interesting morphologies and structures have been recently obtained, exhibiting outstanding electrochemical performance. Hence, in this review we report a comprehensive survey of the progress of multifunctional ZnCo2O4-based materials, focusing on the development of supercapacitor devices and batteries. The top 10 electrode materials for each application are highlighted, including key findings in the development of slurry-cast or binder-free electrodes. In addition, the main strategies in the design of ZnCo2O4-based electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are reviewed, including electrocatalysts capable of performing tetra-electron oxygen reduction reactions (ORRs).
Antioxidant effects of polyphenolic compounds and structure-activity relationship predicted by multivariate regression tree
(2021) Santos, Suzana da Costa; Fortes, Gilmara Aparecida Corrêa; Camargo, Lilian Tatiane Ferreira de Melo; Camargo, Ademir João; Ferri, Pedro Henrique
Phenolic antioxidants form a class of compounds which inhibit the oxidation of materials of biological importance, playing a preventive role in a number of degenerative diseases. Polyphenol activity depends on their chemical structure, which is influenced by factors such as number and position of phenolic hydroxyl groups, steric effects, and molecular properties. In this research study, 18 polyphenol structures (13 hydrolysable tannins, 4 flavonoids and ellagic acid) were modelled and their molecular properties (volume, area, dipole moment, polarisability, LogP, EHOMO, ELUMO, and ELUMO–EHOMO gap) calculated by density functional theory (DFT), using the M062X/6-311 + G (d,p) level of theory. Multivariate regression tree (MRT) and canonical redundancy analysis (RDA) were applied to correlate the experimental antioxidant activities obtained by ORAC and DPPH assays and molecular and lipophilic parameters. MRT/RDA split all 18 polyphenols into four clusters with increasing antioxidant capacity. Flavonoids and galloyl esters belong to clusters C1–C3, while cluster C4 is composed mainly of monomeric and dimeric ellagitannins. The RDA1 axis shows a positive correlation between antioxidant activity and parameters polarisability, EHOMO, and LogP. These molecular properties proved to be the most suitable for predicting the relationship between chemical structure and antioxidant capacity for this group of phenolic compounds.
Multifunctional spinel MnCo2O4 based materials for energy storage and conversion: a review on emerging trends, recent developments and future perspectives
(2021) Gonçalves, Josué Martins; Silva, Murillo Neia Thomaz da; Naik, Kusha Kumar; Martins, Paulo Roberto; Rocha, Diego Pessoa; Nossol, Edson; Munoz, Rodrigo Alejandro Abarza; Angnes, Lucio; Rout, Chandra Sekhar
The energy requirement of modern society increases every day. The depletion of the reserves of fossil fuel combined with the deleterious effects of CO2 in the atmosphere is forcing all the world to search for alternative ways of generation and storing energy. Many scientists around the world are pursuing different forms to produce and store energy. Solar and wind sources are a reality for production of electricity, but are not continuous and require storage devices. The development of batteries and hybrid supercapacitors of high energy and power density is of great importance to complement this requirement of energy storage. Rechargeable metal–air batteries which utilize oxygen electrocatalysis seem to be an ideal choice, once the source of energy is not intermittent as solar and wind energy and is based on oxygen bifunctional electrocatalysis of both oxygen reduction and O2 evolution reactions. In addition, water splitting allows the conversion and storage of solar/wind energy into chemical energy, generating fuels with high energy content. From this perspective, spinel MnCo2O4-based materials are promising structures for energy storage and conversion of energy. In this review, the use of low cost and abundant multifunctional materials for the development of supercapacitor devices and batteries was summarized. Completely, the design of electrocatalysts for water splitting and their capability to proportionate the tetra-electronic process of the oxygen reduction reaction are reviewed, including the main strategies in the preparation of these materials and considering their key multifunctional role in the way to a more sustainable society.
Principal Response Curves analysis of polyphenol variation in resistant and susceptible cotton after infection by a root-knot nematode (RKN)
(2016) Alves, Gleina Costa Silva; Ferri, Pedro Henrique; Seraphin, José Carlos; Fortes, Gilmara Aparecida Corrêa; Rocha, Mara Rúbia da; Santos, Suzana da Costa
The root-knot nematode (RKN), Meloidogyne incognita, attacks cotton root system. This study aimed to compare the induction of phenolic compounds over time in two cotton genotypes, resistant (TX-25) and susceptible (FM966), by RKN. Chemical profiles of cotton roots were obtained by HPLC, NMR, and colorimetric methods at four different time intervals. The Principal Response Curves analysis, a time-dependent, multivariate method, showed consistent variability over time in the profile of phenolic compounds between treatments for both genotypes. The variables that most contributed to the divergence between damaged and undamaged cotton roots were dimethoxylated and non-methoxylated gossypols, total flavonoids, and total phenols.
A percepção do software educativo químico pelo professor da educação básica
(2017) Barreto, Gislane Silvério Neto; Xavier, Janaína Lopes; Santos, José Divino dos; Porto, Marcelo Duarte; Mesquita, Nyuara Araújo da Silva
Currently there several educational software with pedagogical goals available on the internet, all of which explore specific content to be worked on. These software can be used to make a class dynamic. This study is part of a much larger project geared towards software designers for the teaching of chemistry. In this manner, the objective of this work is to learn about how educational software geared towards teaching chemistry is perceived by basic education professors, and thus we completed a theoretical analysis of certain selected software, considering the content methodology and the adequateness of its use as a didactic resource in the classroom.
Verificação da condução da prática como componente curricular e dos estágios supervisionados do curso de licenciatura em química do IFG-Câmpus Itumbiara
(2017) Fields, Karla Amâncio Pinto; Graciano, Marlene Ribeiro da Silva; Andrade, Jordana Américo Zei; Mesquita, Nyuara Araújo da Silva; Bernardes, Giselle Carvalho; Alves, Blyeny Hatalita Pereira
The objective of this work was to identify how the practice implements itself as a curricular component and as supervised practice of the Chemistry Graduation Course of IFG Câmpus Itumbiara, as well as to compare the formative proposal presented in the Pedagogical Project Course (PPC) and the effectiveness of these activities. The Brazilian legislation provides 400 hours of Practice as a Curricular Component (PCC) and 400 hours of Supervised Practice as compulsory formative elements in teacher training courses. However, the resolutions that establish these hours are not specific in the sense of how these workloads should be structured. This research is qualitative because it considers that knowledge is a human construction and, therefore, it’s contextualized in a period and a space. The data were collected by means of the Pedagogical Project of the Chemistry Graduation Course of IFG - Câmpus Itumbiara was built based on the legal regulations regarding PCC, but as these regulations do not define how these CCPs can be effected in the development of the curriculum of the course, it is up to the teachers to interpret and carry out these activities. The teachers' narratives show that they agree that the workloads of the PCC can be distributed in the existing subjects according what is in the PPC, but that there is the necessity of discussion of which strategies can effectively contribute to the graduates' training model, based on critical rationality, in other words, the transformation of education and society. Graduation Course of the IFG - Câmpus Itumbiara, documents provided by the course coordination regarding the development of the PCC in 2015/2 and the questions opened to the teachers of this course who taught classes in the period 2015/2, as well as documents completed by trainee teachers in the period 2016/2. These data were analyzed using the Discursive Textual Analysis technique. The results show that the PPC of the Chemistry Graduation Course of IFG - Câmpus Itumbiara was built based on the legal regulations regarding PCC, but as these regulations do not define how these CCPs can be effected in the development of the curriculum of the course, it is up to the teachers to interpret and carry out these activities. The teachers' narratives show that they agree that the workloads of the PCC can be distributed in the existing subjects according what is in the PPC, but that there is the necessity of discussion of which strategies can effectively contribute to the graduates' training model, based on critical rationality, in other words, the transformation of education and society.
Recent advances in electroanalytical drug detection by porphyrin/phthalocyanine macrocycles: developments and future perspectives
(2021) Gonçalves, Josué Martins; Iglesias, Bernardo Almeida; Martins, Paulo Roberto; Angnes, Lucio
Porphyrins and phthalocyanines are promising π-conjugated compounds with fantastic photochemical and electrochemical properties which are present in nature in more systems than we are generally aware. The electrochemical properties of these large aromatic molecules are also unique, endowing them with the ability to catalyze a wide range of redox reactions. The macrocycle core of these molecules is extremely favorable for the complexation of several metal ions, resulting in molecules with tunable properties. Porphyrins and phthalocyanines are able to form highly organized films, with high conductivity and great robustness and their use was explored to build a great number of electrochemical and photoelectrochemical sensors for many varied applications, one among them being drug analysis. This review will focus on the potential of the electrodes modified with attractive porphyrins and phthalocyanines for this application. The papers published in the last 3 years were closely evaluated.
Recent progress in water splitting and hybrid supercapacitors based on nickel-vanadium layered double hydroxides
(2021) Gonçalves, Josué Martins; Martins, Paulo Roberto; Araki, Koiti; Angnes, Lucio
Environmentally friendly energy sources alternatives to fossil fuels such as solar and wind are strategic for meeting the needs of an increasingly energy demanding society, despite their periodic/intermittent nature. Thus, urge the development of clean and renewable energy sources such as based on solar energy and water in a cyclic way, by photoinduced water-splitting and regeneration in fuel cells. In this context, energy storage devices such as hybrid supercapacitors become fundamental for realization of a sustainable society. In this review, the early discovery and recent advances concerning synthetic strategies, hierarchical structures, and oxygen evolution reaction (OER)/hydrogen evolution reactions (HER) catalytic performances of nickel-vanadium double hydroxides (NiV-LDHs) based nanomaterials are summarized. A discussion about the role of vanadium ions in HER/OER was also included, highlighting the recent progress in theoretical calculations in this field. Finally, some hybrid supercapacitor electrode materials based on NiV-LDHs are described, including the strategies to circumvent the parasitic oxygen evolution reaction during charge-discharge of those energy storage devices. In short, catalysts for HER/OER and hybrid supercapacitor electrode materials based on NiV-LDHs were reviewed considering their key multifunctional role in the way to a more sustainable society.
Zirconia-supported cobalt catalysts: activity and selectivity in NO reduction by CO
(2017-12-13) Lima, Thiago de Melo; Pereira, Cristiane Alves; Nova Castelblanco, William; Silva, Sebastiao William da; Santos, Camila Messias Barbosa; Santana, Ricardo Costa de; Urquieta Gonzalez, Ernesto Antonio; Sartoratto, Patrícia Pommé Confessori
Cobalt catalysts supported on tetragonal and monoclinic zirconia were prepared using a one-pot procedure through the incorporation of a Co3O4 colloidal suspension during the support synthesis and evaluated in the reaction of NO reduction by CO. A better dispersion of the active phase was obtained by this method when compared to the conventional impregnation one. Furthermore, the crystalline phase of zirconia in the supports had a crucial effect in the dispersion of the cobalt species, being that the pure tetragonal phase led to a higher dispersion of the active phase. The one-pot prepared tetragonal zirconia led to cobalt active species that consisted in well-dispersed small agglomerates of Co3O4 and Co2+ species as oxo-ions which displayed the best catalytic performance among the studied catalysts, with the highest NO conversion (75%) and high selectivity to N2 (85%) at 300 °C. These results show that the one-pot methodology employed in this work has a strong potential to produce suitable catalysts for the abatement of NOx emissions.
Enhancement of stability and specific charge capacity of alpha-Ni(OH)2 by Mn(II) isomorphic substitution
(2019) Gomes, Allan Pablo; Gonçalves, Josué Martins; Araki, Koiti; Martins, Paulo Roberto
Mixed hydroxide materials with a large specific charge capacity (417 C g−1) and charge retention capacity (86%) even after 5000 galvanostatic charge–discharge processes at 25 A g−1, promising as electrode materials of energy storage devices such as hybrid batteries, are realized by isomorphic substitution of Ni(II) by Mn(II) ions in the turbostratic alpha-nickel hydroxide lattice, generating for the first time double hydroxide salt types (Ni-95 and Ni-75) instead of layered double hydroxide type materials, significantly enhancing the electrochemical properties and stability of nickel hydroxide nanoparticles (Ni-100). The presence of Mn(II) ions in the alpha-Ni(OH)2 structure is confirmed by flame atomic absorption spectrometry (FAAS), X-ray photoelectron spectroscopy (XPS), and X-ray diffractometry (XRD) of the mixed nickel–manganese hydroxide materials.
Unveiling the structure of polytetraruthenated nickel porphyrin by raman spectroelectrochemistry
(2015-03-26) Ferreira, Luís Marcos Cerdeira; Grasseschi, Daniel; Santos, Mauro Sérgio Ferreira; Martins, Paulo Roberto; Ferreira, Luís Marcos Cerdeira; Gutz, Ivano Gebhardt Rolf; Ferreira, Ana Maria da Costa; Araki, Koiti; Toma, Henrique Eisi; Angnes, Lucio
The structure of polytetraruthenated nickel porphyrin was unveiled for the first time by electrochemistry, Raman spectroelectrochemistry, and a hydroxyl radical trapping assay. The electrocatalytic active material, precipitated on the electrode surface after successive cycling of [NiTPyP{Ru(bipy)2Cl}4]4+ species in strong aqueous alkaline solution (pH 13), was found to be a peroxo-bridged coordination polymer. The electropolymerization process involves hydroxyl radicals (as confirmed by the characteristic set of DMPO/•OH adduct EPR peaks) as reaction intermediates, electrocatalytically generated in the 0.80–1.10 V range, that induce the formation of Ni–O–O–Ni coordination polymers, as evidenced by Raman spectroelectrochemistry and molecular modeling studies. The film growth is halted above 1.10 V due to the formation of oxygen gas bubbles.
Recent trends and perspectives in electrochemical sensors based on MOF-derived materials
(2021) Gonçalves, Josué Martins; Martins, Paulo Roberto; Rocha, Diego Pessoa; Matias, Tiago Araújo; Julião, Murilo Sérgio da Silva; Munoz, Rodrigo Alejandro Abarza; Angnes, Lucio
Metal organic frameworks (MOFs) are hybrid materials built with both organic and inorganic components. The potential of these structures was highlighted in the 1990s and since then, over 90 000 articles dealing with MOFs have been published (still growing rapidly), demonstrating a wide variety of applications. However, an improvement in the electrochemical properties of MOFs is still required to enhance the attributes to satisfy the real and strategic applications of MOF-electrode materials in energy conversion and storage (batteries, supercapacitors, and as catalysts for fuel cells and water splitting), especially in the development of electrochemical sensors. In this sense, being the focus of this review, the great potential of MOF-derived structures for the construction of electrochemical sensors is presented, highlighting the recent advances and strategies on MOF-derived materials, such as metals, metal oxide/hydroxide, metal sulfides, metal phosphides, carbons, or their composites and their potential as electrode materials. In fact, MOF-derived materials exhibit exceptional conductivity, electrochemical activity, and stability, which surpass the relative low conductivity and lack chemical/structural robustness of pristine MOFs, inheriting only the essential structural and compositional properties from their MOF precursors.

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