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1.
Chem Commun (Camb) ; 58(36): 5482-5485, 2022 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-35416211

RESUMO

A chiral N,N'-dioxide/cobalt(II) complex catalytic system is developed to promote the multistep cascade reaction of α,ß-unsaturated-N-aryl nitrones with allenes, giving a variety of chiral dihydropyridoindoles in moderate to good yields with excellent dr and ee values. Mechanistic studies support a [3+2] cycloaddition/[3,3]-rearrangement/retro-Mannich process.


Assuntos
Cobalto , Alcadienos , Catálise , Óxidos de Nitrogênio , Estereoisomerismo
2.
Mikrochim Acta ; 189(5): 200, 2022 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-35474402

RESUMO

Three-dimensional (3D) cobalt molybdate (CoMoO4) hierarchical nanoflake arrays on pencil graphite electrode (PGE) (CoMoO4/PGE) are actualized via one-pot hydrothermal technique. The morphological features comprehend that the CoMoO4 nanoflake arrays expose the 3D, open, porous, and interconnected network architectures on PGE. The formation and growth mechanisms of CoMoO4 nanostructures on PGE are supported with different structural and morphological characterizations. The constructed CoMoO4/PGE is operated as an electrocatalytic probe in enzyme-less electrochemical glucose sensor (ELEGS), confronting the impairments of cost- and time-obsessed conventional electrode polishing and catalyst amendment progressions and obliged the employment of a non-conducting binder. The wide-opened interior and exterior architectures of CoMoO4 nanoflake arrays escalate the glucose utilization efficacy, whilst the intertwined nanoflakes and graphitic carbon layers, respectively, of CoMoO4 and PGE articulate the continual electron mobility and catalytically active channels of CoMoO4/PGE. It jointly escalates the ELEGS concerts of CoMoO4/PGE including high sensitivity (1613 µA mM-1 cm-2), wide linear glucose range (0.0003-10 mM), and low detection limit (0.12 µM) at a working potential of 0.65 V (vs. Ag/AgCl) together with the good recovery in human serum. Thus, the fabricated CoMoO4/PGE extends exclusive virtues of modest electrode production, virtuous affinity, swift response, and excellent sensitivity and selectivity, exposing innovative prospects to reconnoitring the economically viable ELEGSs with binder-free, affordable cost, and expansible 3D electrocatalytic probes.


Assuntos
Grafite , Cobalto , Eletrodos , Glucose , Grafite/química , Humanos , Prostaglandinas E
3.
J Chem Theory Comput ; 18(5): 3099-3110, 2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35404607

RESUMO

Cationic cobaltocenium derivatives are promising components of the anion exchange membranes because of their excellent thermal and alkaline stability under the operating conditions of a fuel cell. Here, we present an efficient modeling approach to assessing the chemical stability of substituted cobaltocenium CoCp2+, based on the computed electronic structure enhanced by machine learning techniques. Within the aqueous environment, the positive charge of the metal cation is balanced by the hydroxide anion through formation of the CoCp2+OH- complexes, whose dissociation is studied within the implicit solvent employing the density functional theory. The data set of about 118 the CoCp2+OH- complexes based on 42 substituent groups characterized by a range of electron-donating (ED) and electron-withdrawing (EW) properties is constructed and analyzed. Given 12 carefully chosen chemistry-informed descriptors of the complexes and relevant fragments, the stability of the complexes is found to strongly correlate with the energies of the highest occupied and lowest unoccupied molecular orbitals, modulated by a switching function of the Hirshfeld charge. The latter is used as a measure of the electron-withdrawing-donating character of the substituents. On the basis of this observation from the conventional regression analysis, two fully connected, feed-forward neural network (FNN) models with different unit structures, called the chemistry-informed (CINN) and the quadratic (QNN) neural networks, together with a support vector regression (SVR) model are developed. Both deep neural network models predict the bond dissociation energies of the cobaltocenium complexes with mean relative errors less than 10.56% and average absolute errors less than 1.63 kcal/mol, superior to the conventional regression and the SVR model prediction. The results show the potential of QNN to efficiently capture more complex relationships. The concept of incorporating the domain (chemical) knowledge/insight into the neural network structure paves the way to applications of machine learning techniques with small data sets, ultimately leading to better predictive models compared to the classical machine learning method SVR and conventional regression analysis.


Assuntos
Cobalto , Anticoncepcionais Orais Combinados , Elétrons , Feminino , Humanos , Aprendizado de Máquina , Redes Neurais de Computação
4.
J Colloid Interface Sci ; 620: 454-464, 2022 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-35447574

RESUMO

The increasingly electromagnetic wave (EMW) pollution has rendered the study and development of new, high-efficiency EMW absorbers a sought-after topic. In this study, graphite carbon nitride nanotubes/cobalt@carbon (GCNNs/Co@C) composites were fabricated using an in-situ synthesis method, which included facile grinding and carbonization pyrolysis. The synthesized GCNNs/Co@C composites exhibited a unique castor-fruit-like structure, that is, GCNNs formed an entwined three-dimensional (3D) network structure on the surface of cobalt@carbon (Co@C), which improved the EMW absorption properties of composites. The obtained GCNNs/Co@C composites exhibited excellent EMW absorption performance. For the fabricated GCNNs/Co@C composites, the minimum reflection loss (RLmin) value reached -63.90 dB at a thickness of 1.96 mm, and the effective absorption bandwidth (EAB, RL ≤  -10 dB) achieved 4.44 GHz at an ultra-thin thickness of 1.51 mm. The EAB covered the entire X and Ku bands (6.96-18.00 GHz) through thickness adjustment from 1.51 to 2.50 mm. Underlying EMW absorption mechanisms were briefly discussed. This study presents a novel design method to prepare light-weight and highly-efficient EMW absorbing absorbers.


Assuntos
Grafite , Nanotubos , Carbono , Cobalto , Radiação Eletromagnética , Frutas , Nitrilas
5.
Inorg Chem ; 61(18): 6837-6851, 2022 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-35471858

RESUMO

Cobalt(III) complexes [Co(TPA)(L1)](ClO4)2 (1), [Co(4-COOH-TPA)(L1)](ClO4)2 (2), [Co(TPA)(L2)]Cl2 (3), and [Co(4-COOH-TPA)(L2)]Cl2 (4) having acetylacetonate-linked boron-dipyrromethene ligands (L1, acac-BODIPY; L2, acac-diiodo-BODIPY) were prepared and characterized, and their utility as bioimaging and phototherapeutic agents was evaluated (TPA, tris-(2-pyridylmethyl)amine; 4-COOH-TPA, 2-((bis-(2-pyridylmethyl)amino)methyl)isonicotinic acid). HL1, HL2, and complex 1 were structurally characterized by X-ray crystallography. Complexes 1 and 2 on photoactivation or in a reducing environment (excess GSH, ascorbic acid, and 3-mercaptopropionic acid) released the acac-BODIPY ligand. They exhibited strong absorbance near 501 nm (ε ∼ (5.2-5.8) × 104 M-1 cm-1) and emission bands near 513 nm (ΦF ∼ 0.13, λex = 490 nm) in dimethyl sulfoxide (DMSO). Complexes 3 and 4 with absorption maxima at ∼536 and ∼538 nm (ε ∼ (1.2-1.8) × 104 M-1 cm-1), respectively, afforded high singlet oxygen quantum yield (ΦΔ âˆ¼ 0.79) in DMSO. Complexes 1-4 showed Co(III)-Co(II) redox responses near -0.2 V versus saturated calomel electrode (SCE) in dimethylformamide (DMF)-0.1 M tetrabutylammonium perchlorate (TBAP). The photocleavage of pUC19 DNA by complex 4 revealed the formation of both singlet oxygen and superoxide anion radicals as the reactive oxygen species (ROS). Confocal fluorescence microscopy showed the selective accumulation of complex 1 in the endoplasmic reticulum (ER) in A-549 cells. Complex 4 exhibited a high phototherapeutic index value (PI > 7000) in HeLa cancer cells (IC50 ∼ 0.007 µM in visible light of 400-700 nm, total dose ∼5 J cm-2). The ancillary ligands in the complexes demonstrated a structure-activity relationship and modulated the Co(III)-Co(II) redox potential, the complex solubility, acac-BODIPY ligand release kinetics, and phototherapeutic efficacy.


Assuntos
Antineoplásicos , Fotoquimioterapia , Antineoplásicos/química , Compostos de Boro , Cobalto/farmacologia , Dimetil Sulfóxido , Hidroxibutiratos , Ligantes , Pentanonas , Fármacos Fotossensibilizantes/química , Fármacos Fotossensibilizantes/farmacologia , Oxigênio Singlete
6.
J Environ Manage ; 313: 114930, 2022 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-35367671

RESUMO

The recycling of lithium batteries should be prioritized, and the use of discarded alkali metal battery electrode materials as photocatalysts merits research attention. This study synthesized alkali metal cobalt oxide (MCoO2, M = Li or Na) as a photocatalyst for the photoreduction of CO2 and degradation of toxic organic substances. The optimized NaCoO2 and LiCoO2 photocatalysts increased the photocatalytic CO2-CH4 conversion rate to 21.0 and 13.4 µmol g-1 h-1 under ultraviolet light irradiation and to 16.2 and 5.3 µmol g-1 h-1 under visible light irradiation, which is 17 times higher than that achieved by TiO2 P25. The rate constants of the optimized reactions of crystal violet (CV) with LiCoO2 and NaCoO2 were 2.29 × 10-2 and 4.35 × 10-2 h-1, respectively. The quenching effect of the scavengers and electron paramagnetic resonance in CV degradation indicated that active O2•-, 1O2, and h+ play the main role, whereas •OH plays a minor role for LiCoO2. The hyperfine splitting of the DMPO-•OH and DMPO-•CH3 adducts was aN = 1.508 mT, aHß = 1.478 mT and aN = 1.558 mT, aHß = 2.267 mT, respectively, whereas the hyperfine splitting of DMPO+• was aN = 1.475 mT. The quenching effect also indicated that active O2•- and h+ play the main role and that •OH and 1O2 play a minor role for NaCoO2. The hyperfine splitting of the DMPO-•OH and DMPO+• adducts was aN = 1.517 mT, aHß = 1.489 mT and aN = 1.496 mT, respectively. Discarded alkali metal battery electrode materials can be reused as photocatalysts to address environmental pollution.


Assuntos
Dióxido de Carbono , Poluentes Ambientais , Álcalis , Cobalto , Lítio , Óxidos/química , Fotólise
7.
J Environ Manage ; 313: 114855, 2022 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-35390662

RESUMO

A magnetic FeCo2O4/Co3O4 nanocomposite was successfully synthesized by a facile hydrothermal method as an efficient activator for persulfate (PS) activation to degrade tetracycline (TC) in an aqueous solution. TC removal and mineralization efficiencies reached up to 91.63% and 43.57% in 120 min in the FCC-3/PS system, respectively. The mixed-valence of Fe/Co in the nanocomposite catalyst was beneficial for electrons transfer between Co and Fe elements and enhanced the redox circulation of Fe and Co in between divalent and trivalent. Surficial analysis and phosphate adsorption test confirmed the existence of -OH groups on the surfaces of FeCo2O4/Co3O4 nanocomposite. Fe/Co redox and surficial hydroxyl in the catalyst played significant roles in the TC potentiation degradation, which was contributed by the plenty of adsorbed -OH groups and excellent dispersity of FeCo2O4 in the FeCo2O4/Co3O4 composite. The sulfate radicals were major species followed by the hydroxyl radicals, and the surficial adsorbed hydroxyl made great contributions to radical generation. The cycling test and intermediate toxicity analysis indicated that the nanocomposite was considered stable and practicable in water treatment. This work demonstrated that the FeCo2O4/Co3O4 nanocomposite was an effective and environ-friendly catalyst towards PS activation for removing organic pollutants from water.


Assuntos
Tetraciclina , Poluentes Químicos da Água , Antibacterianos , Cobalto , Radical Hidroxila , Oxirredução , Óxidos , Poluentes Químicos da Água/análise
8.
J Colloid Interface Sci ; 619: 267-279, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35397460

RESUMO

The directional regulation of oxidation capacity in the carbon-based peroxymonosulfate (PMS) activation system is a promising strategy for wastewater purification. In this work, a novel iron cobalt and nitrogen co-doped carbonized wood sponge (FeCoNCWS) was developed. A superb catalytic performance for sulfamethoxazole (SMX) degradation (∼100.0%) was obtained within 30 min in FeCoNCWS800/PMS system at 60 °C. Besides, the reactive oxygen species (ROS) contribution was verified at different reaction temperatures. Specifically, the primary roles of sulfate and hydroxyl radicals (SO4- and OH) in SMX removal weakened, while the secondary role of singlet oxygen (1O2) in SMX degradation was enhanced with the rise of reaction temperature in FeCoNCWS800/PMS system. Interestingly, defects, graphitic N and carbonyl (CO) groups were vital active sites for PMS activation to produce 1O2, which was facilitated at higher reaction temperature. Besides, the metal sites were identified as PMS activators for SO4- and OH generation, which was promoted under lower reaction temperature. The findings revealed a novel internal temperature-dependent PMS activation mechanism, which can help to regulate the oxidation capacity of PMS activation system rationally for pollutant degradation.


Assuntos
Cobalto , Nitrogênio , Ferro , Peróxidos/química , Sulfametoxazol , Temperatura , Madeira
9.
Mikrochim Acta ; 189(5): 205, 2022 04 29.
Artigo em Inglês | MEDLINE | ID: mdl-35488133

RESUMO

Novel cube-like transition metal oxide embedded on graphitic carbon nitride (MCO@GCN) formed a hybrid composite via hydrothermal assisted sonochemical synthesis. The synthesized composite was examined with various physical characterizations such as morphological SEM, EDX, XRD, and FT-IR spectroscopy. The electrocatalytic activity of MCO@GCN composite was further investigated when used  to modify a glassy carbon electrode (GCE). The electrochemical sensor was investigated using modified MCO@GCN/GCE towards environmental pollutant 2,4,6-trichlorophenol (2,4,6-TCP) detection with at a potential of (+ 0.654 V vs Ag/AgCl) in pH-7. The structural features have favored a high charge transfer ratio with excellent conductivity which showed a low detection limit (LOD) of 0.0068 µM and sensitivity of 23.57 µA·µM-1·cm-2 comprising a wide linear working range of 0.01-1720 µM by using differential pulse voltammetry. Besides, the MCO@GCN/GCE displayed excellent selectivity , repeatability, reproducibility, storage, and operational stability. Notably, the proposed MCO@GCN/GCE was validated with different environmental samples (tap, river, and industrial water) with RSD 0.62-2.86% and 96.51-99.66% (n = 3) recovery.


Assuntos
Carbono , Manganês , Carbono/química , Cobalto , Eletrodos , Grafite , Limite de Detecção , Compostos de Nitrogênio , Óxidos/química , Reprodutibilidade dos Testes , Espectroscopia de Infravermelho com Transformada de Fourier
10.
Environ Sci Technol ; 56(9): 5611-5619, 2022 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-35442647

RESUMO

Rapid generation of high-valent cobalt-oxo species (Co(IV)═O) for the removal of organic contaminants has been challenging because of the low conversion efficiency of Co(III)/Co(II) and the high activation energy barrier of the Co(II)-oxidant complex. Herein, we introduced nitrogen (N) vacancies into graphite carbon nitride imbedded with cobalt carbonate (CCH/CN-Vn) in a peroxymonosulfate (PMS)/visible light system to break the limitations of a conventional two-electron transfer path. These N vacancies enhanced the electron distribution of the Co 3d orbital and lowered the energy barrier to cleave the O-O bond of PMS in the Co(II)-PMS complex, achieving the modulation of major active species from 1O2 to Co(IV)═O. The developed synergistic system that exhibited adsorption and oxidation showed remarkable selectivity and contaminant removal performance in inorganic (Cl-, NO3-, HCO3-, and HPO4-) organic (HA) and even practical aqueous matrices (tap water and secondary effluent). This study provides a novel mechanistic perspective to modulate the nonradical path for refractory contaminant treatment via defect engineering.


Assuntos
Cobalto , Nitrogênio , Oxidantes , Peróxidos
11.
Inorg Chem ; 61(17): 6438-6450, 2022 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-35438990

RESUMO

It was recently discovered that (Ph2PPrPDI)Mn (PDI = pyridine diimine) exists as a superposition of low-spin Mn(II) that is supported by a PDI dianion and intermediate-spin Mn(II) that is antiferromagnetically coupled to a triplet PDI dianion, a finding that encouraged the synthesis and electronic structure evaluation of late first row metal variants that feature the same chelate. The addition of Ph2PPrPDI to FeBr2 resulted in bromide dissociation and the formation of [(Ph2PPrPDI)FeBr][Br]. Reduction of this precursor using excess sodium amalgam afforded (Ph2PPrPDI)Fe, which possesses an Fe(II) center that is supported by a dianionic PDI ligand. Similarly, reduction of a premixed solution of Ph2PPrPDI and CoCl2 yielded the cobalt analog, (Ph2PPrPDI)Co. EPR spectroscopy and density functional theory calculations revealed that this compound features a high-spin Co(I) center that is antiferromagnetically coupled to a PDI radical anion. The addition of Ph2PPrPDI to Ni(COD)2 resulted in ligand displacement and the formation of (Ph2PPrPDI)Ni, which was found to possess a pendent phosphine group. Single-crystal X-ray diffraction, CASSCF calculations, and EPR spectroscopy indicate that (Ph2PPrPDI)Ni is best described as having a Ni(II)-PDI2- configuration. The electronic differences between these compounds are highlighted, and a computational analysis of Ph2PPrPDI denticity has revealed the thermodynamic penalties associated with phosphine dissociation from 5-coordinate (Ph2PPrPDI)Mn, (Ph2PPrPDI)Fe, and (Ph2PPrPDI)Co.


Assuntos
Cobalto , Ferro , Cobalto/química , Eletrônica , Ferro/química , Ligantes , Níquel , Oxirredução , Fosfinas , Piridinas/química
12.
Int J Mol Sci ; 23(8)2022 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-35457167

RESUMO

In this paper, we present a study by computer simulation on superparamagnetic hyperthermia with CoFe2O4 ferrimagnetic nanoparticles coated with biocompatible gamma-cyclodextrins (γ-CDs) to be used in alternative cancer therapy with increased efficacy and non-toxicity. The specific loss power that leads to the heating of nanoparticles in superparamagnetic hyperthermia using CoFe2O4-γ-CDs was analyzed in detail depending on the size of the nanoparticles, the thickness of the γ-CDs layer on the nanoparticle surface, the amplitude and frequency of the alternating magnetic field, and the packing fraction of nanoparticles, in order to find the proper conditions in which the specific loss power is maximal. We found that the maximum specific loss power was determined by the Brown magnetic relaxation processes, and the maximum power obtained was significantly higher than that which would be obtained by the Néel relaxation processes under the same conditions. Moreover, increasing the amplitude of the magnetic field led to a significant decrease in the optimal diameter at which the maximum specific loss power is obtained (e.g., for 500 kHz frequency the optimal diameter decreased from 13.6 nm to 9.8 nm when the field increased from 10 kA/m to 50 kA/m), constituting a major advantage in magnetic hyperthermia for its optimization, in contrast to the known results in the absence of cyclodextrins from the surface of immobilized nanoparticles of CoFe2O4, where the optimal diameter remained practically unchanged at ~6.2 nm.


Assuntos
Hipertermia Induzida , Nanopartículas de Magnetita , Nanopartículas , Neoplasias , gama-Ciclodextrinas , Cobalto , Simulação por Computador , Compostos Férricos , Humanos , Hipertermia , Hipertermia Induzida/métodos , Nanopartículas Magnéticas de Óxido de Ferro , Nanopartículas de Magnetita/uso terapêutico , Neoplasias/terapia
13.
Sensors (Basel) ; 22(7)2022 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-35408102

RESUMO

In this study, nitrogen and sulfur co-doped carbon dots (NS-CDs) were investigated for the detection of heavy metals in water through absorption-based colorimetric response. NS-CDs were synthesized by a simple one-pot hydrothermal method and characterized by TEM, STEM-coupled with energy dispersive X-ray analysis, NMR, and IR spectroscopy. Addition of Cu(II) ions to NS-CD aqueous solutions gave origin to a distinct absorption band at 660 nm which was attributed to the formation of cuprammonium complexes through coordination with amino functional groups of NS-CDs. Absorbance increased linearly with Cu(II) concentration in the range 1-100 µM and enabled a limit of detection of 200 nM. No response was observed with the other tested metals, including Fe(III) which, however, appreciably decreased sensitivity to copper. Increase of pH of the NS-CD solution up to 9.5 greatly reduced this interference effect and enhanced the response to Cu(II), thus confirming the different nature of the two interactions. In addition, a concurrent response to Co(II) appeared in a different spectral region, thus suggesting the possibility of dual-species multiple sensitivity. The present method neither requires any other reagents nor any previous assay treatment and thus can be a promising candidate for low-cost monitoring of copper onsite and by unskilled personnel.


Assuntos
Carbono , Pontos Quânticos , Carbono/química , Cobalto , Colorimetria/métodos , Cobre/análise , Compostos Férricos , Nitrogênio/química , Pontos Quânticos/química , Enxofre , Água
14.
Phys Chem Chem Phys ; 24(17): 10451-10464, 2022 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-35441635

RESUMO

The rapid development of applications relying on magnetism at the nanoscale has put a spotlight on nanoparticles with novel morphologies that are associated with enhanced electronic and magnetic properties. In this quest, nanoalloys combining highly magnetic cobalt and weakly reactive gold could offer many application-specific advantages, such as strong magnetic anisotropy. In the present study, we have employed density functional theory (DFT) calculations to provide a systematic overview of the size- and morphology-dependence of the energetic order and magnetic properties of AuCo nanoparticles up to 2.5 nm in diameter. The core-shell icosahedron was captured as the most favourable morphology, showing a small preference over the core-shell decahedron. However, the magnetic properties (total magnetic moments and magnetic anisotropy) were found to be significantly improved within the L10 ordered structures, even in comparison to monometallic Co nanoparticles. Atom-resolved charges and orbital moments accessed through the DFT analysis of the electronic level properties permitted insight into the close interrelation between the AuCo nanoparticle morphology and their magnetism. These results are expected to assist in the design of tailored magnetic AuCo nanoalloys for specific applications.


Assuntos
Ouro , Nanopartículas Metálicas , Anisotropia , Cobalto/química , Ouro/química , Magnetismo , Nanopartículas Metálicas/química
15.
J Phys Chem B ; 126(17): 3257-3268, 2022 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-35446582

RESUMO

All contemporary oxygenic phototrophs─from primitive cyanobacteria to complex multicellular plants─split water using a single invariant cluster comprising Mn4CaO5 (the water oxidation catalyst) as the catalyst within photosystem II, the universal oxygenic reaction center of natural photosynthesis. This cluster is unstable outside of PSII and can be reconstituted, both in vivo and in vitro, using elemental aqueous ions and light, via photoassembly. Here, we demonstrate the first functional substitution of manganese in any oxygenic reaction center by in vitro photoassembly. Following complete removal of inorganic cofactors from cyanobacterial photosystem II microcrystal (PSIIX), photoassembly with free cobalt (Co2+), calcium (Ca2+), and water (OH-) restores O2 evolution activity. Photoassembly occurs at least threefold faster using Co2+ versus Mn2+ due to a higher quantum yield for PSIIX-mediated charge separation (P*): Co2+ → P* → Co3+QA-. However, this kinetic preference for Co2+ over native Mn2+ during photoassembly is offset by significantly poorer catalytic activity (∼25% of the activity with Mn2+) and ∼3- to 30-fold faster photoinactivation rate. The resulting reconstituted Co-PSIIX oxidizes water by the standard four-flash photocycle, although they produce 4-fold less O2 per PSII, suggested to arise from faster charge recombination (Co3+QA ← Co4+QA-) in the catalytic cycle. The faster photoinactivation of reconstituted Co-PSIIX occurs under anaerobic conditions during the catalytic cycle, suggesting direct photodamage without the involvement of O2. Manganese offers two advantages for oxygenic phototrophs, which may explain its exclusive retention throughout Darwinian evolution: significantly slower charge recombination (Mn3+QA ← Mn4+QA-) permits more water oxidation at low and fluctuating solar irradiation (greater net energy conversion) and much greater tolerance to photodamage at high light intensities (Mn4+ is less oxidizing than Co4+). Future work to identify the chemical nature of the intermediates will be needed for further interpretation.


Assuntos
Cianobactérias , Complexo de Proteína do Fotossistema II , Cobalto , Cianobactérias/metabolismo , Manganês/química , Oxirredução , Oxigênio/química , Complexo de Proteína do Fotossistema II/química , Água/química
16.
J Am Chem Soc ; 144(14): 6465-6474, 2022 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-35369695

RESUMO

Cobalt precatalysts for the meta-selective borylation of fluorinated arenes are described. Initial screening and stoichiometric reactivity studies culminated in the preparation of a cobalt alkyl precatalyst supported by the sterically protected terpyridine (5,5″-Me2ArTpy = 4'-(4-N,N'-dimethylaminophenyl)-5,5″-dimethyl-2,2':6',2″-terpyridine). Under the optimized conditions, borylation with this precatalyst afforded up to 16 turnovers and near-exclusive meta regioselectivity with a range of substituted fluoroarenes in cyclopentyl methyl ether solvent at room temperature. Deuterium kinetic isotope effects of 2.9(2) at 23 °C support a turnover-limiting and selectivity-determining C(sp2)-H activation step, and stoichiometric C-H activation experiments provided insights into the identity of the C-H activating intermediate in catalysis. Analysis of the relevant Co-C and C-H bond thermodynamics support that the thermodynamics of C-H activation favor ortho-to-fluorine selectivity, providing additional, indirect support for kinetic control of C-H activation as the origin of meta selectivity.


Assuntos
Cobalto , Flúor , Catálise , Cobalto/química , Flúor/química , Cinética , Termodinâmica
17.
Int J Mol Sci ; 23(7)2022 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-35409224

RESUMO

In nature, solar energy is captured by different types of light harvesting protein-pigment complexes. Two of these photoactivatable proteins are bacteriorhodopsin (bR), which utilizes a retinal moiety to function as a proton pump, and photosystem I (PSI), which uses a chlorophyll antenna to catalyze unidirectional electron transfer. Both PSI and bR are well characterized biochemically and have been integrated into solar photovoltaic (PV) devices built from sustainable materials. Both PSI and bR are some of the best performing photosensitizers in the bio-sensitized PV field, yet relatively little attention has been devoted to the development of more sustainable, biocompatible alternative counter electrodes and electrolytes for bio-sensitized solar cells. Careful selection of the electrolyte and counter electrode components is critical to designing bio-sensitized solar cells with more sustainable materials and improved device performance. This work explores the use of poly (3,4-ethylenedioxythiophene) (PEDOT) modified with multi-walled carbon nanotubes (PEDOT/CNT) as counter electrodes and aqueous-soluble bipyridine cobaltII/III complexes as direct redox mediators for both PSI and bR devices. We report a unique counter electrode and redox mediator system that can perform remarkably well for both bio-photosensitizers that have independently evolved over millions of years. The compatibility of disparate proteins with common mediators and counter electrodes may further the improvement of bio-sensitized PV design in a way that is more universally biocompatible for device outputs and longevity.


Assuntos
Bacteriorodopsinas , Nanotubos de Carbono , Compostos Bicíclicos Heterocíclicos com Pontes , Cobalto , Eletrodos , Eletrólitos , Nanotubos de Carbono/química , Fármacos Fotossensibilizantes , Complexo de Proteína do Fotossistema I , Polímeros
18.
Anal Chem ; 94(18): 6711-6718, 2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35486137

RESUMO

Alkaline phosphatase (ALP), an essential hydrolase with crucial roles in living organisms, has widely been regarded as a biomarker for various human diseases in clinical diagnoses. Herein, taking advantage of cobalt oxyhydroxide (CoOOH) nanoflakes and nonenzymatic cascade recycling amplification (CRA), a highly sensitive and label-free fluorescence biosensing strategy for the determination of ALP activity is introduced. In our design, ALP can promote the dephosphorylation of l-ascorbic acid 2-phosphate (AAP) to reduce ascorbic acid (AA), which is then able to decompose CoOOH in a nucleic acids@CoOOH nanocomplex into Co2+ cofactors. Further, enzyme-free CRA was rapidly initiated by integrating DNAzyme recycling amplification and catalytic hairpin assembly, resulting in the generation of an abundance of G-quadruplex structure-contained DNA duplexes. In the presence of thioflavin T (ThT), analytical target ALP was converted in an amplified and activatable fluorescence signal. The experimental results show that this method can be applied for the quantitative analysis of ALP activity with a low detection limit of 0.027 mU/mL. Moreover, this developed biosensing approach exhibits excellent specificity, and the evaluation of ALP activity in the complex human serum samples was successfully realized, indicating that it can afford a reliable, robust, and cost-effective nanoplatform for an ALP-based clinical diagnosis and for biomedical research.


Assuntos
Técnicas Biossensoriais , DNA Catalítico , Fosfatase Alcalina/análise , Técnicas Biossensoriais/métodos , Cobalto , Corantes Fluorescentes , Humanos , Limite de Detecção , Oxirredução , Óxidos
19.
Anal Chem ; 94(18): 6866-6873, 2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35486468

RESUMO

Tris(bipyridine) ruthenium(II)-based luminophores have been well developed in the area of electrochemiluminescence, while their applications in chemiluminescence (CL) are rarely studied due to the poor luminous efficiency and complicated CL reaction. Herein, a novel tris(bipyridine) ruthenium(II)-based ternary CL system is proposed by introducing cobalt single atoms integrated with graphene-encapsulated cobalt nanoparticles (Co SAs/Co@C) and peroxymonosulfate (PMS) as advanced coreaction accelerator and promising coreactant, respectively. On the basis of the experimental results and density functional theory calculations, it is concluded that Co@C can synergistically modulate the adsorption behavior of PMS on Co SAs and then efficiently activate PMS to produce massive singlet oxygen for remarkable CL emission. Under the optimum conditions, the as-prepared CL biosensor exhibits a good linear range, excellent sensitivity, and selectivity, holding great potential for the practical detection of prostate-specific antigen in human serum.


Assuntos
Compostos Heterocíclicos , Rutênio , Cobalto , Humanos , Luminescência , Medições Luminescentes/métodos , Peróxidos
20.
Acta Orthop ; 93: 444-450, 2022 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-35438184

RESUMO

BACKGROUND AND PURPOSE: We have previously reported that the whole blood (WB) chromium (Cr) and cobalt (Co) ion levels decrease in the short term after ReCap-M2a-Magnum large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA). This study reports long-term metal ion levels and clinical outcomes after ReCap-Magnum THA. PATIENTS AND METHODS: ReCap-M2a-Magnum LDH THA was used in 1,450 patients in our hospital district from 2005 to 2012. Median follow-up time was 10 years. 991 patients had 2 or more metal ion measurements. The median measurement interval was 4 years. Individual metal ion change was assessed using logarithmic metal ion values in a random coefficient model. Kaplan-Meier survival estimates were calculated for revision surgery for any reason for revision, and separately for metal-related adverse events (metal ions above safe upper limit [SUL], revision due to ARMD, or pseudotumor). RESULTS: Geometric mean of Cr decreased from 1.8 ppb (geometric standard deviation [GSD] 1.8) to 1.0 ppb (GSD 2.8, p < 0.001). The Co levels decreased from 1.7 ppb (GSD 2.4) to 1.4 ppb (GSD 2.8, p < 0.001). The hip-specific survival was 85% for revision due to any reason at 14 years and the hip-specific survival for any metal-related adverse event was 69% at 14 years. INTERPRETATION: WB Cr and Co levels continued to decrease in the long-term follow-up of ReCap-M2a-Magnum THA patients. The amount of metal-related adverse events was rather high, but revision surgery was seldom required. We suggest that after 10 years from the implantation a 5-year measurement interval may be sufficient for asymptomatic ReCap-M2a-Magnum patients.


Assuntos
Artroplastia de Quadril , Prótese de Quadril , Próteses Articulares Metal-Metal , Artroplastia de Quadril/efeitos adversos , Cromo , Cobalto , Prótese de Quadril/efeitos adversos , Humanos , Íons , Próteses Articulares Metal-Metal/efeitos adversos , Metais , Desenho de Prótese , Falha de Prótese , Reoperação
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