Incorporation Of Co Research Articles

Mono, dual and tri-doped TiO2: Sunlight photocatalytic, room temperature ferromagnetic and dielectric constant properties

In this study, the optical, magnetic and electrical properties of nanostructured TiO2 semiconductor have been investigated for multi-functional applications. Herein, different compositions composed of TiO2, Ti0.985Co0.015O2, Ti0.97Co0.015Mn0.015O2, Ti0.97Co0.015Fe0.015O2 and Ti0.97Co0.01Mn0.01Fe0.01O2 were synthesized by coprecipitation method. The XRD and Rietveld refinement analysis confirmed that TiO2, Ti0.985Co0.015O2, Ti0.97Co0.015Mn0.015O2 and Ti0.97Co0.01Mn0.01Fe0.01O2 powders have mixed phases of rutile and anatase TiO2 structure while Ti0.97Co0.015Fe0.015O2 powder has anatase structure. The incorporation of Co, (Co, Mn), (Co, Fe) and (Co, Mn, Fe) ions into TiO2 lattice decreases the band gap energy from 3.13 eV to 3.05, 2.7, 3.08 and 2.88 eV, respectively. Ti0.985Co0.015O2 and Ti0.97Co0.015Fe0.015O2 samples exhibit high sunlight efficiencies of 73% and 72% for Congo red (CR) dye degradation in 80 min, respectively. The dielectric constant and electrical conductivity of TiO2 were enhanced due to insertion of Co2+, Mn2+ and Fe2+/3+ ions. Among all samples, Ti0.97Co0.015Mn0.015O2 composition reveals the highest dielectric constant value of 5004. On the other hand, notable room temperature ferromagnetism with found in Ti0.97Co0.015Fe0.015O2 composition with magnetization value of 0.056 emu/g and coercivity of 86 Oe. The obtained results confirmed that the incorporation of Co2+, Mn2+ and Fe2+/3+ ions into TiO2 enhances the electrical, magnetic and photocatalytic properties.

Revisiting Reduction of CO2 to Oxalate with First-Row Transition Metals: Irreproducibility, Ambiguous Analysis, and Conflicting Reactivity.

Construction of higher C≥2 compounds from CO2 constitutes an attractive transformation inspired by nature’s strategy to build carbohydrates. However, controlled C–C bond formation from carbon dioxide using environmentally benign reductants remains a major challenge. In this respect, reductive dimerization of CO2 to oxalate represents an important model reaction enabling investigations on the mechanism of this simplest CO2 coupling reaction. Herein, we present common pitfalls encountered in CO2 reduction, especially its reductive coupling, based on established protocols for the conversion of CO2 into oxalate. Moreover, we provide an example to systematically assess these reactions. Based on our work, we highlight the importance of utilizing suitable orthogonal analytical methods and raise awareness of oxidative reactions that can likewise result in the formation of oxalate without incorporation of CO2. These results allow for the determination of key parameters, which can be used for tailoring of prospective catalytic systems and will promote the advancement of the entire field.

Incorporation of Co2+, Cu2+, and Zn2+ ions into nickel oxide thin films and their enhanced electrochemical and electrochromic performances

Incorporation of Co2+, Cu2+, and Zn2+ ions into nickel oxide thin films and their enhanced electrochemical and electrochromic performances

Impact of gas ultrafine bubbles on the potency of chlorine solutions against Listeria monocytogenes biofilms

AbstractUltrafine bubble technology is a novel concept in food safety that can improve the potency of antimicrobials against biofilms. This study was conducted to evaluate the impact of gas (air, CO2, or N2) ultrafine bubbles incorporation in 100 and 200 ppm chlorine (Cl2) solutions to inactivate fresh Listeria monocytogenes biofilms on stainless steel. Listeria monocytogenes biofilms were grown on stainless steel coupons through static incubation at 37°C for 72 hr by immersing in L. monocytogenes inoculated brain heart infusion (BHI) broth. The coupons were treated by dipping in water or Cl2 solutions with or without ultrafine bubbles for 1 min. Random pre‐determined areas on coupons were swabbed into Dey–Engley neutralizing broth before and after treatments and enumerated using BHI agar. Air and CO2 nanobubbles in 100 ppm Cl2 resulted in greater log reductions (5.0 and 4.9 log CFU/cm2, respectively) in L. monocytogenes biofilms compared with 100 ppm Cl2 without gas ultrafine bubbles (3.7 log CFU/cm2). Incorporation of air, CO2, and N2 ultrafine bubbles in water and 200 ppm Cl2 did not have any impact on the efficacy of biofilm inactivation.

Accessing Divergent Main-Chain-Functionalized Polyethylenes via Copolymerization of Ethylene with a CO2/Butadiene-Derived Lactone.

Carbon dioxide (CO2) has been used as a sustainable comonomer in the synthesis of different functional polymers including polycarbonates, polyurea, and polyurethane. Until today, despite the great interest, little success has been made for incorporating CO2 into the most widely used polyethylene materials. Herein, we report the incorporation of CO2 to polyethylenes through the copolymerization of ethylene with a CO2/butadiene-derived lactone, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVP). Two-types of main-chain-functionalized polyethylenes can be synthesized through different copolymerization strategies. Palladium-catalyzed coordination/insertion copolymerization furnished polyethylenes bearing unsaturated lactones, while radical copolymerization afforded polyethylenes bearing bicyclic lactones. Modification of the polyethylene chains was successfully accomplished through Michael addition or aminolysis. This highly versatile copolymerization protocol provides access to a diverse range of polyethylene materials made from ethylene, CO2, and 1,3-butadiene.

Core-Doped [(Cd1-xCox)10S4(SPh)16]4- Clusters from a Self-Assembly Route.

The incorporation of substitutional Co2+ impurities in [Cd10S4(SPh)16]4- (Cd10) molecular clusters prepared by the self-assembly method where Na2S is the sulfur precursor and a redox method where elemental S is the sulfur precursor is studied. The Co2+ ions provide unique spectroscopic and chemical handles to monitor dopant speciation during cluster formation and determine what role, if any, other cluster species play during Cd10 cluster formation. In contrast to the redox method that produces exclusively surface-exchanged Co2+-doped Cd10 (Co:Cd10), the preparation of Cd10 by the self-assembly method in the presence of Co2+ ions results in Co2+ incorporation at both the surface and core sites of the Cd10 cluster. Electrospray ionization mass spectrometry (ESI-MS) analysis of the dopant distribution for the self-assembly synthesis of Co:Cd10 is consistent with a near-Poissonian distribution for all nominal dopant concentrations albeit with reduced actual Co2+ incorporation. At a nominal Co2+ concentration of 50%, we observe incorporation of up to seven Co2+ ions within the Cd10 self-assembled cluster compared to a maximum of only four Co2+ dopants in the Cd10 redox clusters. The observation of up to seven Co2+ dopants must involve substitution of at least three core sites within the Cd10 cluster. Electronic absorption spectra of the Co2+ ligand field transition in the heavily doped Co:Cd10 clusters display clear deviation with the surface-doped Co2+-doped Cd10 clusters prepared by the redox method. We hypothesize that the coordination of Co2+ and S2- ions in solution prior to cluster formation, which is possible only with the self-assembly method, is critical to the doping of Co2+ ions within the Cd10 cores.

Ag(I)-Catalyzed C–H Carboxylation of Thiophene Derivatives

CO2 utilization is an attractive aspect as it allows the direct conversion of CO2 into valuable chemicals. In this regard, direct incorporation of CO2 into the C–H bond of heteroaromatic compounds is important due to the ubiquitous structural motifs of the heteroaromatic carboxylic acids. Herein, we report the Ag-catalyzed C–H carboxylation of thiophene derivatives. This new catalytic system involving a phosphine ligand and lithium tert-butoxide enables the direct carboxylation of thiophenes under mild reaction conditions. Experimental studies revealed that the use of tert-butyl alkoxide is critical for the exergonic formation of an arylsilver intermediate, and the results were further supported by density functional theory calculations.

Enhanced orange emission of Zn0.98–XMn0.02CoxS (x = 0[formula omitted]0.02) quantum dots

Mn 2+, Co2+ ions double doped ZnS was obtained via co-precipitation technique under room temperature. The doping concentration of Mn2+ was fixed as 2 at. wt% and Co2+ was varied from 0 to 3%. The synthesized products were analyzed using XRD, SEM, EDX, UV–vis optical study, FT-IR spectra and PL spectra. The synthesized nanostructures size was determined from XRD results and they were in the range of 2.9 to 3.7 nm and the size was increased for Co2+ 1 at. wt% doping. All the samples had a cubic structure without a trace of any secondary phases. The optical band gap values are red-shifted due to the increase of Co2+ concentration. A higher UV–vis optical transmittance was offered by 1 at. wt% Co2+ doped Mn:ZnS nanostructures. PL emissions noticed at 472 and 592 nm. These blue and orange emissions were addressed by the creation of trap states due to the incorporation of Co2+ ions and the emission intensity was increased at higher composition of dopant. The creation of more charge carriers and the generation of defects are responsible for the improved catalytic behavior in Co = 2% doped Zn0.98Mn0.02S which established superior efficiency after sex re-cycling progression.

Optical, electrochemical and photocatalytic properties of cobalt doped CsPbCl3 nanostructures: a one-pot synthesis approach

The present manuscript aims at the synthesis of cesium based halide perovskite nanostructures and the effect of cobalt doping on the structural, optical, lumnisent, charge storage and photocatalytic properties. In a very first attempt, we report the solvothermal synthesis of Co doped CsPbCl3 nanostructures under subcritical conditions. The structural features were demonstrated by X-ray diffraction (XRD) Surface morphology determined cubic shape of the synthesized particles. Doping is an excellent way to modify the properties of host material in particular to the electronic structure or optical properties. Incorporation of Co2+ ions in the perovskite structure tunes the optical properties of the nanostructures making this perovskite a visible light active material (Eg = 1.6 eV). This modification in the optical behaviour is the result of size effect, the crystallite size of the doped nanostructures increases with cobalt doping concentration. Photolumniscance (PL) study indicated that CsPbCl3 exhibited Blue emission. Thermogravametric analysis (TGA) revealed that the nanostructures are quite stable at elavated temperatures. The electrochemical performance depicts the pseudocapacative nature of the synthesized nanostructures and can used for charge storage devices. The charge storage capability showed direct proportionality with cobalt ion concentration. And Finally the photocatalytic performance of synthesized material shows superior catalytic ability degrading 90% of methylene blue (MB) dye in 180 min under visible light conditions.

Cover Picture: Bioelectrocatalytic Cofactor Regeneration Coupled to CO2 Fixation in a Redox‐Active Hydrogel for Stereoselective C−C Bond Formation (Angew. Chem. Int. Ed. 38/2021)

Redox-active polymers for wiring NADPH recycling and CO2-fixating enzymes create a bioelectrocatalytic volume on electrodes for the regio- and stereoselective incorporation of CO2 into complex molecules via C−C bond formation at high current densities. Details of the study are presented in the Research Article by Michael Richter, Nicolas Plumeré et al. on page 21056.

Insights to the hydrothermal synthesis of highly crystalline aluminum-free Na[Co]ZSM-5 zeolites and their CO2 adsorption performance

In this work, MFI-type cobaltosilicates as inorganic polymers consisting of tetrahedral TO4 (T = Si and Co) building units were synthesized by utilization of a novel pretreatment method aimed for the silicon precursor activation. Crystallization of zeolites was carried out using a conventional hydrothermal method. The effect of various parameters such as Co/Si molar ratio, crystallization time and pH of initial gel on the crystallization process was studied to provide the optimal conditions for crystallization. The prepared zeolites were characterized using XRD, FT-IR, UV–vis, SEM, TEM, N2 adsorption, and TGA techniques. The XRD patterns confirmed the formation of pure crystalline ZSM-5 zeolites without any cobalt oxide impurities. A small shift towards lower diffraction angles in the XRD patterns of the samples was detected by increasing cobalt content in the initial gel, which validated the incorporation of Co2+ ions into the zeolites’ framework. The presence of Co2+ ions in the tetrahedral positions of zeolites’ framework was also proved by FT-IR and UV–vis spectra. EDX-mapping images exhibited a more uniform dispersion of Co2+ ions in the structure of ZSM-5 zeolite synthesized at pH = 9.5 compared to its analogous counterpart synthesized at higher pH. The results of N2 adsorption analysis revealed that the specific surface area of Na[Co]ZSM-5 zeolites was comparable to aluminosilicate ZSM-5 zeolites. The synthesized zeolites were examined for CO2 adsorption. The adsorption capacities measured at 298 K and 1 bar were approximately 2.19 and 5.33 mmol g−1 for samples prepared at pH = 9.5 and 10.5, respectively.

Bioelectrocatalytic Cofactor Regeneration Coupled to CO2 Fixation in a Redox-Active Hydrogel for Stereoselective C-C Bond Formation.

The sustainable capture and conversion of carbon dioxide (CO2) is key to achieving a circular carbon economy. Bioelectrocatalysis, which aims at using renewable energies to power the highly specific, direct transformation of CO2 into value added products, holds promise to achieve this goal. However, the functional integration of CO2‐fixing enzymes onto electrode materials for the electrosynthesis of stereochemically complex molecules remains to be demonstrated. Here, we show the electricity‐driven regio‐ and stereoselective incorporation of CO2 into crotonyl‐CoA by an NADPH‐dependent enzymatic reductive carboxylation. Co‐immobilization of a ferredoxin NADP+ reductase and crotonyl‐CoA carboxylase/reductase within a 2,2′‐viologen‐modified hydrogel enabled iterative NADPH recycling and stereoselective formation of (2S)‐ethylmalonyl‐CoA, a prospective intermediate towards multi‐carbon products from CO2, with 92±6 % faradaic efficiency and at a rate of 1.6±0.4 μmol cm−2 h−1. This approach paves the way for realizing even more complex bioelectrocatalyic cascades in the future.

Immobilization of cobalt‐loaded laponite/carboxymethyl chitosan on polycaprolactone nanofiber for improving osteogenesis and angiogenesis activities

AbstractDesigning scaffolds with therapeutic potential to stimulate angiogenesis and osteogenesis is considered a promising strategy in the regeneration of large skeletal defects. In this study, the cobalt ions (Co2+) were incorporated in laponite (LAP) nanodiscs (0.65, 1.3, and 2.6 g/L) and, in combination with carboxymethyl chitosan (CMC), were immobilized on the electrospun polycaprolactone (PCL) nanofiber to fabricate scaffolds for simultaneous enhancing osteogenesis and angiogenesis inductions to human bone marrow mesenchymal stem cells. The Fourier transform infrared, energy dispersive X‐ray, and inductively coupled plasma atomic emission spectrometries confirmed the Co2+‐loading on the LAP nanodiscs and the chemical immobilization on the surface of PCL nanofibers. The result of MTT assay, scanning electron microscopy, and fluorescence staining displayed that Co2+‐loaded scaffolds were biocompatible. Furthermore, the incorporation of Co2+ ions into LAP nanodiscs had significant effects on the calcium deposition and expression of osteogenic markers, alkaline phosphatase and osteonectin, as well as, the expression of angiogenic markers, hypoxia‐inducible factor‐1α and vascular endothelial growth factor of the cells seeded on the scaffolds (p ≤ 0.05). These results suggested that the combination of Co2+ ions with CMC/LAP could result in a synergetic effect on the osteogenesis and angiogenesis stimulations.

The effect of annealing time and gas flow rate on optical and magnetic properties of (Al,Co) co-doped ZnO nanoparticles by varying Al concentration

The effect of Al, a trivalent substitution was investigated in Co doped ZnO with regards to the role of additional carriers in n-type magnetic semiconductors. Nanoparticle samples of Zn1?xCo0.04AlxO with different Al compositions (x = 0, 0.005, 0.010, 0.015 and 0.020) were annealed at 600 oC for different time (5 hours and 8 hours) and different gas flow rates (25 sccm and 50 sccm). All nanoparticles attained Wurtzite hexagonal structure in a stable form after annealing in forming gas. The effect of annealing time and gas pressure were investigated. Magnetization measurements revealed that air annealed samples displayed paramagnetic properties. Nevertheless, after annealing in forming gas, magnetic moments are stabilized and follow a monotonic trend. Diffuse reflectivity measurements revealed the incorporation of Co2+ ions into the Wurtzite hexagonal lattice. The optical band-gap was found to be increasing with increasing Al concentration of up to 0.01, followed by a decrease with further increase in Al concentration

Estimation of the CO2 flux index in the San Andrés Island using fuzzy logic

When applying diffuse inference systems through the GeoFIS tool in a database of the coral complex of the island of San Andrés, a CO2 flux index was estimated that allows us to know the effect of the flux on the sea and the influence of the variables involved. It was found that six of the studied areas had a state of acidification of the sea due to CO2, while all the other areas had a slight incorporation of the gas. Likewise, it was evident that the variables that have a significant influence on the incorporation of CO2 into the marine environment are the sea surface temperature and the chemical nature of this gas, according to the component analysis. Therefore, the diffuse methods for the determination of acidification of coral ecosystems, allows establishing an approach to the effects that the gradual incorporation of CO2 would have into the marine environment, in addition to providing excellent advantages in terms of its determination based on satellite information.

A preliminary study into the use of tree-ring and foliar geochemistry as bio-indicators for vehicular NOx pollution in Malta

ABSTRACT Emissions from traffic over the past few decades have become a significant source of air pollution. Among the pollutants emitted are nitrogen oxides (NOx), exposure to which can be detrimental to public health. Recent studies have shown that nitrogen (N) stable isotope ratios in tree-rings and foliage express a fingerprint of their major N source, making them appropriate for bio-monitoring purposes. In this study, we have applied this proxy to Aleppo pines (Pinus halepensis) at three distances from one of the busiest roads in Malta, a country known to suffer from intense traffic pollution. Our results showed that N and organic carbon (C) stable isotope ratios in tree-rings do not vary over the period 1980–2018 at any of the investigated sites; however, statistically significant spatial trends were apparent in both tree-rings and foliage. The roadside and transitional sites exhibited more positive δ 15N and more negative δ 13C values compared to those at a rural control site. This is likely due to the incorporation of 15N-enriched NOx and 13C-depleted CO2 from traffic pollution. Sampled top-soil also exhibited the δ 15N trend. Our results constitute the first known application of dendrogeochemistry to atmospheric pollution monitoring in Malta.

Kinetic investigation of aerobic epoxidation of limonene over cobalt substituted mesoporous SBA-16

Incorporation of low coordination Co2+ within the structure of mesoporous silica SBA-16 has been accomplished through a facile and green “pH adjusting” method.

New Insights on a µm-Scale into the Transformation Process of CH4 Hydrates to CO2-Rich Mixed Hydrates

The global occurrences of natural gas hydrates lead to the conclusion that tremendous amounts of hydrocarbons are bonded in these hydrate-bearing sediments, serving as a potential energy resource. For the release of the hydrate-bonded CH4 from these reservoirs, different production methods have been developed during the last decades. Among them, the chemical stimulation via injection of CO2 is considered as carbon neutral on the basis of the assumption that the hydrate-bonded CH4 is replaced by CO2. For the investigation of the replacement process of hydrate-bonded CH4 with CO2 on a µm-scale, we performed time-resolved in situ Raman spectroscopic measurements combined with microscopic observations, exposing the CH4 hydrates to a CO2 gas phase at 3.2 MPa and 274 K. Single-point Raman measurements, line scans and Raman maps were taken from the hydrate phase. Measurements were performed continuously at defined depths from the surface into the core of several hydrate crystals. Additionally, the changes in composition in the gas phase were recorded. The results clearly indicated the incorporation of CO2 into the hydrate phase with a concentration gradient from the surface to the core of the hydrate particle, supporting the shrinking core model. Microscopic observations, however, indicated that all the crystals changed their surface morphology when exposed to the CO2 gas. Some crystals of the initial CH4 hydrate phase grew or were maintained while at the same time other crystals decreased in sizes and even disappeared over time. This observation suggested a reformation process similar to Ostwald ripening rather than an exchange of molecules in already existing hydrate structures. The experimental results from this work are presented and discussed in consideration of the existing models, providing new insights on a µm-scale into the transformation process of CH4 hydrates to CO2-rich mixed hydrates.

Impact of gas micro-nano-bubbles on the efficacy of commonly used antimicrobials in the food industry.

To study the impact of incorporating micro-nano-bubbles (MNBs) in commonly used food antimicrobials (AMs) against Escherichia coli O157:H7 (EC) and Listeria monocytogenes (LM). Air, carbon dioxide (CO2 ) and nitrogen (N2 ) were used to incorporate MNBs in city water. AM solution (with or without MNBs) of 9ml was individually taken into sterile test tubes and mixed with 1ml of inoculum grown in brain heart infusion (BHI) broth to get the net AM concentrations of 28·4ppm peracetic acid (PAA), 200ppm chlorine (Cl2 ), 5·4% citric acid (CA) and 4·5% lactic acid (LA). After treatment time of 1·5 and 3·0min, 1ml of sample was neutralized using Dey-Engley neutralizing broth and plated on BHI agar. For EC, Cl2 -CO2 solutions resulted in significantly greater log reductions (5·2 logs) compared to that of Cl2 solutions without MNBs (3·8 logs). For LM, PAA-CO2 solutions resulted in significantly greater log reductions (4·4 logs) compared to that of PAA solutions without MNBs (1·7 logs). This study demonstrated that the efficacy of Cl2 and PAA AM solutions could be increased by incorporating CO2 -MNBs against EC and LM in microbiological growth medium. Incorporation of CO2 -MNBs in AM solutions could increase the efficacy of AMs against pathogens on/in food matrices, which should be tested in future research.

DMC-Mediated Copolymerization of CO2 and PO—Mechanistic Aspects Derived from Feed and Polymer Composition

The influence of composition of liquid phase on composition of poly(propylene ether carbonates) in the copolymerization of CO2 with propylene oxide (PO), mediated by a zinc chloride cobalt double metal cyanide, was monitored by FT-IR/CO2 uptake/size exclusion chromatography in batch and semi-batch mode. The ratio of mol fractions of carbonate to ether linkages F (~0.15) was found virtually independent on the feed between 60 and 120 °C. The presence of CO2 lowers the catalytic activity but yields more narrowly distributed poly(propylene ether carbonates). Hints on diffusion and chemistry-related restrictions were found underlying, broadening the distribution. The incorporation of CO2 seems to proceed in a metal-based insertion chain process, ether linkages are generated stepwise after external nucleophilic attack. The presence of amines resulted in lower activities and no change in F. An exchange of chloride for nitrate in the catalyst led to a higher F of max. 0.45. The observations are interpreted in a mechanistic scheme, comprising surface-base-assisted nucleophilic attack of external weak nucleophiles and of mobile surface-bound carboxylato entities on activated PO in competition to protonation of surface-bound alkoxide intermediates by poly(propylene ether carbonate) glycols or by surface-bound protons. Basic entities on the catalyst may promote CO2 incorporation.