Nanoparticles Of Co Research Articles

Change of composition and surface plasmon resonance of Pd/Au core/shell nanoparticles triggered by CO adsorption.

Controlling composition and plasmonic response of bimetallic nanoparticles (NPs) is of great relevance to tune their catalytic activity. Herein, we demonstrate reversible composition and plasmonic response transitions from a core/shell to a bimetallic alloyed palladium/gold NP triggered by CO adsorption and sample temperature. The use of self-organized growth on alumina template film allows scrutinizing the impact of core size and shell thickness onto NP geometry and plasmonic response. Topography, molecular adsorption, and plasmonic response are addressed by scanning tunneling microscopy, vibrational sum frequency generation (SFG) spectroscopy, and surface differential reflectance spectroscopy, respectively. Modeling CO dipolar interaction and optical reflectivity corroborate the experimental findings. We demonstrate that probing CO adsorption sites by SFG is a remarkably sensitive and relevant method to investigate shell composition and follow in real-time Pd atom migration between the core and the shell. Pd-Au alloying is limited to the first two monolayers of the shell and no plasmonic response is found, while for a thicker shell, a plasmonic response is observed, concomitant with a lower Pd concentration in the shell. Above 10-4mbar, at room temperature, CO adsorption triggers the shell restructuration, forming a Pd-Au alloy that weakens the plasmonic response via Pd migration from the core to the shell. NP annealing at 550K, after pumping CO, leads to the desorption of remaining CO and gives enough mobility for Pd to migrate back inside the core and recover a pure gold shell with its original plasmonic response. This work demonstrates that surface stoichiometry and plasmonic response can be tuned by using CO adsorption and NP annealing.

Exchange of CO2 with CO as Reactant Switches Selectivity in Photoreduction on Co–ZrO2 from C1–3 Paraffin to Small Olefins

Photocatalytic reduction of CO2 into C2,3 hydrocarbons completes a C‐neutral cycle. The reaction pathways of photocatalytic generation of C2,3 paraffin and C2H4 from CO2 are mostly unclear. Herein, a Co0–ZrO2 photocatalyst converted CO2 into C1–3 paraffin, while selectively converting CO into C2H4 and C3H6 (6.0 ± 0.6 μmol h−1 gcat−1, 70 mol%) only under UV–visible light. The photocatalytic cycle was conducted under 13CO and H2, with subsequent evacuation and flushing with CO. This iterative process led to an increase in the population of C2H4 and C3H6 increased up to 61–87 mol%, attributed to the accumulation of CH2 species at the interface between Co0 nanoparticles and the ZrO2 surface. CO2 adsorbed onto the O vacancies of the ZrO2 surface, with resulting COH species undergoing hydrogenation on the Co0 surface to yield C1–3 paraffin using either H2 or H2O (g, l) as the reductant. In contrast, CO adsorbed on the Co0 surface, converted to HCOH species, and then split into CH and OH species at the Co and O vacancy sites on ZrO2, respectively. This comprehensive study elucidates intricate photocatalytic pathways governing the transformation of CO2 into paraffin and CO to olefins.

Exchange of CO2 with CO as Reactant Switches Selectivity in Photoreduction on Co-ZrO2 from C1-3 Paraffin to Small Olefins.

Photocatalytic reduction of CO2 into C2,3 hydrocarbons completes a C-neutral cycle. The reaction pathways of photocatalytic generation of C2,3 paraffin and C2H4 from CO2 are mostly unclear. Herein, a Co0-ZrO2 photocatalyst converted CO2 into C1-3 paraffin, while selectively converting CO into C2H4 and C3H6 (6.0±0.6 μmol h-1 gcat -1, 70 mol %) only under UV/Visible light. The photocatalytic cycle was conducted under 13CO and H2, with subsequent evacuation and flushing with CO. This iterative process led to an increase in the population of C2H4 and C3H6 up to 61-87 mol %, attributed to the accumulation of CH2 species at the interface between Co0 nanoparticles and the ZrO2 surface. CO2 adsorbed onto the O vacancies of the ZrO2 surface, with resulting COH species undergoing hydrogenation on the Co0 surface to yield C1-3 paraffin using either H2 or H2O (g, l) as the reductant. In contrast, CO adsorbed on the Co0 surface, converted to HCOH species, and then split into CH and OH species at the Co and O vacancy sites on ZrO2, respectively. This comprehensive study elucidates intricate photocatalytic pathways governing the transformation of CO2 into paraffin and CO to olefins.

Propane dehydrogenation performance of titanosilicate-1 supported CoOx catalysts by adjusting the acidity and reducibility

The development of low-cost and toxicity-free cobalt oxide-based catalysts for propane dehydrogenation to propylene (PDH) has gained momentum. In this paper, titanosilicate-1 (TS-1) supported CoOx catalysts doped with different alkali and alkaline earth metal ions (M = Na, K, Mg, Ca and Ba) were prepared by adjusting the acidity, reducibility and oxidation state to increase the activity and stability during the PDH reaction. It was found that the decrease in the number of Lewis acid sites and lack of Co2+Ox species with the addition of K ions led to an almost complete loss of the activity of the Co-K catalyst. However, Co-Ca catalyst exhibited moderate acidity, more Lewis acid sites, a larger amount of the in-situ formed highly-dispersed metallic Co0 nanoparticles (∼5 nm) and Co2+Ox species strongly interacting with the support, all of which were responsible for its highest space-time yield (STY) of propylene formation (0.88 kg h−1 kgcat.−1). Though Co3O4 particles were more active for the side reactions, they could be readily reduced to metallic Co0 nanoparticles during the PDH process, and increased the selectivity to propylene with time on stream. Specifically, it was demonstrated that the highly-dispersed metallic Co0 nanoparticles were also active for the PDH activity, but was lower than Co2+Ox species that were strongly interacted with TS-1 support. The deposited coke on the catalysts was related to the catalyst deactivation. The Co0 species could not completely return to the oxidation states after burning off the deposited coke, which seemed to be related to the incomplete recovery of catalytic activity after regeneration.

Dual interfacing with metallic cobalt boosts the electron shuttle of CdS-carbide nanoassemblies

Harnessing accelerated interfacial redox, thus boosting charge separation, is of great importance in photocatalytic solar hydrogen generation. In effect, nanoassembling non-noble metallic phases in CdS-based systems and elucidating their role in photocatalysis hold the key to eventually boosting electron shuttle in the field. Here we combine an efficient in-situ exsoluted metallic Co0 nanoparticles on a carbides matrix (CMG) with CdS (CdS@CoCMG) for photogeneration of hydrogen. The metallic cobalt phase exhibits strong binding at the CdS-carbide dual interfaces, forming the accelerated “electron converter” mechanism validated by charge transfer kinetics and achieving two orders of magnitude faster hydrogen production (44.42 mmol g−1 h−1) relative to CdS (0.43 mmol g−1 h−1). We propose that the unique catalyst configuration enable the directional electron-relay photocatalysis via harnessing interfaces between Co0 phase, carbides, and CdS clusters, which eventually boosts the redox process and charge separation of the integrated system, leading to high H2 production rates in the suspension.

CO-Driven Au Recovery and Nanoparticle Synthesis By in-Situ CO2 Reduction on Gas-Diffusion Electrodes

Effective synthesis methods for gold nanoparticles (NPs) have been extensively researched due to their wide-ranging applications in biomedicine, bioanalytical processes, and electrochemistry. Chemical reduction is the most common technique for producing precious metals nanoparticles, with the synthesis method greatly influencing the morphology of the resulting product. In most instances, the formation of polydisperse nanoparticles (NPs) is obtained (Reverberi, Kuznetsov et al. 2016). CO is a known reducing agent for and , offering fast reduction rates (Pretzer, Nguyen et al. 2010) and easy removal, resulting in fewer purification steps.We recently reported a synthesis method called Gas-Diffusion Electrocrystallization (GDEx), which can be applied to the platinum group metals (PGMs). The precipitation of the water-soluble PGM precursors is accomplished by the in situ production of H2 and CO, issued from the electrochemical reduction of CO2 and water electrolysis, respectively. This is typically accomplished using gas diffusion electrodes (Martinez Mora, Pozo et al. 2023). H2 acts as a reducing agent and CO as a size-controlling agent. In this work, we propose the synthesis of Au0 NPs driven by the GDEx process fed by CO2 in aqueous media.Different current densities (i.e., 10 and 40 mA cm-2) and two gas-flow regimes were tested –flow-by (FB) and flow-through (FT). Under FB, excess gas was fed into the gas chamber of the electrochemical set-up (i.e., 200 mL min-1), while under FT, the gas chamber overpressure was increased to force the gas through the GDE in convective regime, (i.e., the outlet of the gas chamber was closed and the flow rate was set to 5 mL min-1).In the first instance, the CO-driven Au(III) reduction process was modeled, including the CO(g)-CO(l) mass transport and equilibrium. It was discovered that the CO mass transport is the bottleneck in the reduction rate.In the GDEx electrochemical set-up, lower current densities and FT conditions achieved smaller particle size (i.e., 46 nm at -10 mA cm-2 and FT, table 1) and higher current efficiencies for CO production (~19 %, where the competing reaction was H2 evolution, table 1). Conversely, higher current densities led to faster reduction kinetics, yet lower current efficiencies (see Fig. 1).The GDEx process enables Au recovery and nanoparticle synthesis from Au(III)-containing synthetic streams, and can be applied to industrial leachates from end-of-life products. Conditions favoring CO mass transport and availability in the electrolyte improved the reduction kinetics. Furthermore, GDEx allows controlled CO production, mitigating the risk associated with using pure CO.Table 1. Summary of CO yield, current efficiencies and NP size for the different operating conditions j / mA cm-2 FB/FT CO generation / mmol min-1 CECO / % CEAu / % NP Size / nm Crystallite size / nm -10 FB 0.0023 7.3 4.2 70 ± 32 29 ± 7 FT 0.0081 18.6 6.6 46 ± 17 29 ± 6 -40 FB 0.0046 3.3 2.0 91 ± 36 31 ± 6 FT 0.0081 5.5 2.1 72 ± 20 27 ± 6 This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 958302 (PEACOC project). Martinez Mora, O., G. Pozo, L. F. Leon-Fernandez, J. Fransaer and X. Dominguez-Benetton (2023). "Synthesis of platinum group metal nanoparticles assisted by CO2 reduction and H2 cogeneration at gas-diffusion electrodes." RSC Sustainability.Pretzer, L., Q. Nguyen and M. Wong (2010). "Controlled Growth of Sub-10 nm Gold Nanoparticles Using Carbon Monoxide Reductant." The Journal of Physical Chemistry C 114.Reverberi, A. P., N. T. Kuznetsov, V. P. Meshalkin, M. Salerno and B. Fabiano (2016). "Systematical analysis of chemical methods in metal nanoparticles synthesis." Theoretical Foundations of Chemical Engineering 50: 59-66. Figure 1

Investigation of Static Shear Stress in a Suspension of Co0.2Ni0.8Fe2O4 Nanoparticles in Sesame Oil

Spinel ferrite nanoparticles of Co0.2Ni0.8Fe2O4 composition are utilized as filler magnetic particles in the carrier fluid of sesame oil to prepare a magnetorheological fluid. The hydrothermal method is adopted to prepare CoNi ferrite nanoparticles. X-ray diffraction analysis is used to check the crystalline phase, and transmission electron microscopy is used to image the particles to find the size and shape of particles. The average size is about 18 nm. The magnetic properties are determined by measuring the hysteresis loop by the superconducting quantum interference device technique. The saturation magnetization is 59.4 emu/g, and the coercivity is 30 Oe. The Langevin fitting is applied to the hysteresis loop to show that the particle moment is about 16 × 103 μB. The viscosity and shear stress are measured against the shear rate, where the latter parameters are extracted from the viscosity and the viscometer spindle speed. The viscosity behavior showed the shear thinning against the shear rate. The viscosity increases with the magnetic field. The shear stress increases with the shear rate and has a very good matching with the Bingham model, rather than with the Herschel–Bulkley model, while describing the measured data. We observed a clear high static shear stress at low shear rates that are growing with the magnetic field. The yield stress was increased linearly with magnetic field strength.

Identifying the Structure of Supported Metal Catalysts Using Vibrational Fingerprints from Ab Initio Nanoscale Models.

Identifying active sites of supported noble metal nanocatalysts remains challenging, since their size and shape undergo changes depending on the support, temperature, and gas mixture composition. Herein, the anharmonic infrared spectrum of adsorbed CO is simulated using density functional theory (DFT) to gain insight into the nature of Pd nanoparticles (NPs) supported on ceria. The authors systematically determine how the simulated infrared spectra are affected by CO coverage, NP size (0.5-1.5nm), NP morphology (octahedral, icosahedral), and metal-support contact angle, by exploring a diversity of realistic models inspired by ab initio molecular dynamics. The simulated spectra are then used as a spectroscopic fingerprint to characterize nanoparticles in a real catalyst, by comparison with in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments. Truncated octahedral NPs with an acute Pd-ceria angle reproduce most of the measurements. In particular, the authors isolate features characteristic of CO adsorbed at the metal-support interface appearing at low frequencies, both seen in simulation and experiment. This work illustrates the strong need for realistic models to provide a robust description of the active sites, especially at the interface of supported metal nanocatalysts, which can be highly dynamic and evolve considerably during reaction.

A"Catalysis-Immobilization-Deposition" Stepwise Strategy toward Dynamic Equilibrium of Polysulfides Conversion and Diffusion in Lithium-Sulfur Batteries.

Stepwise electrocatalysis can remarkably accelerate the kinetics of two consecutive reactions in sulfur electrochemistry. However, the significant difference between the catalysis and diffusion rates of polysulfides results in persistent shuttling in the stepwise electrocatalysts. Here, a stepwise electrocatalytic strategy of catalysis-immobilization-deposition is proposed for achieving the consistency of diffusion and catalysis of polysulfides. Accordingly, a sandwich-like stepwise electrocatalyst is designed, which is composed of Co nanoparticles (Co-NP), mesoporous SiO2 , and iron single atom (Fe-SA) (denoted as Co-NP@SiO2 @Fe-SA), serving as catalysis core, immobilization interlayer, and deposition shell, respectively. Benefitting from the dynamic equilibrium between production and consumption of polysulfides achieved by the spatial synergistic effect of the triple sites, the S/Co-NP@SiO2 @Fe-SA cathode delivers a high reversible capacity of 731mAhg-1 over 500 cycles at 1C with a small capacity decay of 0.039% per cycle. Moreover, a high areal capacity of 3.8mAhcm-2 at a sulfur loading of 4.5mgcm-2 is achieved with a low electrolyte/sulfur ratio of 5.9. This work sheds light on a new host design concept with high catalytic activity, stability, and selectivity to enable high performance lithium-sulfur batteries.

Ultrafine Co nanoparticles confined in nitrogen-doped carbon toward two-electron oxygen reduction reaction for H2O2 electrosynthesis in acidic media

Electrocatalytic production of hydrogen peroxide (H2O2) by two-electron oxygen reduction reaction (2e– ORR) under acidic condition has been considered to have great application value. Co nanoparticles (CoNPs) coupled with N-doped carbon are a class of potential electrocatalysts. The effective strategies to further enhance their performances are to improve the active sites and stability. Herein, the material containing ultrafine CoNPs confined in a nitrogen-doped carbon matrix (NC@CoNPs) was synthesized by pyrolyzing corresponding precursors, which was obtained through regulating the topological structure of ZIF-67/ZIF-8 with dopamine (DA). The DA self-polymerization process induced the formation of CoNPs with smaller sizes and formed polydopamine film decreased the detachment of CoNPs from the catalyst. High density of Co-Nx active sites and defective sites could be identified on NC@CoNPs, leading to high activity and H2O2 selectivity, with an onset potential of 0.57 V (vs. RHE) and ∼90% selectivity in a wide potential range. An on-site electrochemical removal of organic pollutant was achieved rapidly through an electro-Fenton process, demonstrating its great promise for on-site water treatment application.

Synergistic effect between Co single atoms and nanoparticles enables selective synthesis of bio-based benzimidazoles

Finite size effect is closely correlated with heterogeneous catalytic activity and selectivity as reducing the metal to a few nanometers, but may suffer from deficient active sites for cascade reactions. Here, a type of dual-size heterogeneous N-doped cobalt catalysts (CoSAs-NPs/NC(n)) with the coexistence of Co single-atoms (Co-SAs) and Co nanoparticles (Co-NPs) were prepared for efficient synthesis of benzimidazoles (up to 91% yield) from 2-nitroanilines and bio-based alcohols via cascade hydrogen transfer-dehydrogenative cyclization. Experimental results and density functional theory calculations suggested that the bio-alcohol dehydrogenation mainly occurs at Co-SAs sites, while Co-NPs sites remarkably facilitate the subsequent reduction of nitro species, indicating the synergistic effect between Co-SAs and Co-NPs in the coupled hydrogen transfer process. The CoSAs-NPs/NC(0.25) catalyst can be recycled and applied to a wide range of substrates (28 examples). This catalytic approach based on the metal size effect opens a new route for the direct upgrading of biomass feedstocks involving multiple reactions.

Cobalt nanoparticles decorated bamboo-like N-doped carbon nanotube as nanozyme sensor for efficient biosensing

• Bamboo-like N doped carbon nanotubes encapsulated with cobalt nanoparticles (Co-BNCNTs) was designed by one-step pyrolysis. • The bamboo-like structure could prevent the self-aggregation of the CoNPs, improve the stability of the CoNPs, and enhance the catalytic activity of the CoNPs. • The hollow tubular structure could shorten the distance for the reactants to reach the electrode surface and accelerate the mass transfer process. In this work, Co nanoparticles decorated bamboo-like N-doped carbon nanotubes (Co-BNCNTs) were design, which exhibited excellent oxidase-mimicking activity and could be served as a novel signal amplification platform for dopamine (DA) sensing. Co nanoparticles (CoNPs) encapsulated in bamboo-like N-doped carbon nanotubes (BNCNTs) could prevent their self-aggregation and expose more active sites. Besides, the N-doping in carbon materials could adjust the charge density and increase active sites. Moreover, the synergistic effect between CoNPs and BNCNTs also could contribute to enhance catalytic activity. In a word, excellent electrical conductivity, large electrochemically active area, multiple catalytically active sites are beneficial for DA detection. The Co-BNCNTs/GCE biosensor showed good stability and selectivity, a wide detection range of 0.5-150 μM, and a lower detection limit of 0.0342 μM. The Co-BNCNTs sensor was employed to detect the DA in the actual sample, which displayed a potential application in clinical diagnosis. Furthermore, our study presented an effective way to the synthesis of metal nanoparticles encapsulated into CNTs catalysts as nanozymes for the application in biosensing.

Testing the validity of the core-shell-surface layer model on the size dependence of effective magnetic anisotropy in magnetic nanoparticles

The stability of the stored information in magnetic recording media depends on the anisotropy energy Ea (=KeffV) of nanoparticles (NPs) of volume V or diameter D. Therefore, it is important to know how the effective anisotropy constant Keff varies with size D of the NPs. In a recent paper [Appl. Phys. Lett. 110, 222409 (2017)], the observed Keff versus D variation in NPs of maghemite (γ-Fe2O3) was explained on the basis of the core-shell-surface layer (CSSL) model given by Eq.: Keff = Kb + (6KS/D) +Ksh{[1-(2d/D)]−3–1}, where Kb,KS, and Ksh are the anisotropy constants of spins in the core, surface layer, and a shell of thickness d, respectively. This CSSL model is an extension of an earlier core-surface layer (CSL) model described by Keff = Kb + (6KS/D) [Phys. Rev. Lett. 72, 282 (1994)] proposed to explain the Keff versus D variation in Fe NPs. For the NPs of γ-Fe2O3, the additional term of the CSSL model involving Ksh was found to be necessary to fit the data for sizes D < 5 nm. In this paper, we report the validity of the CSSL model for NPs of several other systems viz. Co, Ni, NiO, and Fe3O4 using the available data from literature. In selecting the data, care was taken to consider data only for non-interacting NPs since the interparticle interactions generally overshadow the actual value of Keff in NPs. It is shown that the new CSSL model describes very well the Keff vs. D variation for all particle sizes whereas the CSL model fails for smaller particles with the notable exception of Fe NPs. This validation of the CSSL model for the NPs of Co, Ni, NiO, Fe3O4, and γ-Fe2O3 suggests its general validity for magnetic NPs. Discussion is also presented on the comparative magnitudes of the parameters Kb, KS, and Ksh obtained from the fits to the CSSL model.

Cobalt nanoparticles cause allergic contact dermatitis inhumans.

Cobalt (Co) causes allergic contact dermatitis (ACD) and the emerging use of Co nanoparticles (CoNPs) warrants gaining further insight into its potential to elicit ACD in sensitized individuals. The aims of the study were to clarify to what extent CoNPs may elicit ACD responses in participants with Co contact allergy, and to evaluate whether the nanoparticles cause a distinct immune response compared with cobalt chloride (CoCl2) in the skin reactions. Fourteen individuals with Co contact allergy were exposed to CoNPs, CoCl2, a Co-containing hard-metal disc (positive control), and an empty test chamber (negative control) by patch testing. Allergic responses were evaluated clinically by a dermatologist at Days 2, 4 and 7. At Day 2, patch-test chambers were removed, and remaining test-substance and skin-wipe samples were collected for inductive-coupled plasma mass spectrometry (ICP-MS) analysis. Additionally, skin biopsies were taken from patch-test reactions at Day 4 for quantitative real-time polymerase chain reaction analysis, histopathology and ICP-MS analysis of Co skin penetration. Patch testing with CoNPs elicited allergic reactions in Co-sensitized individuals. At all timepoints, clinical assessment revealed significantly lower frequencies of positive patch-test reactions to CoNPs compared with CoCl2 or to the positive control. CoNPs elicited comparable immune responses to CoCl2. Chemical analysis of Co residues in patch-test filters, and on skin, shows lower doses for CoNPs compared with CoCl2. CoNPs potently elicit immune responses in Co-sensitized individuals. Even though patch testing with CoNPs resulted in a lower skin dose than CoCl2, identical immunological profiles were present. Further research is needed to identify the potential harm of CoNPs to human health.

2D Microporous Covalent Organic Frameworks as Cobalt Nanoparticle Supports for Electrocatalytic Hydrogen Evolution Reaction

Covalent organic frameworks (COFs) are a new class of porous crystalline polymers, which are considered to be excellent supports for metal nanoparticles (MNPs) due to their highly ordered structure, chemical tunability, and porosity. In this work, two novel ultra-microporous COFs, JUC−624 and JUC−625, with narrow pore size distribution have been synthesized and used for the confined growth of ultrafine Co nanoparticles (CoNPs) with high loading. In an alkaline environment, the produced materials were investigated as electrocatalysts for the hydrogen evolution reaction (HER). Electrochemical test results show that CoNPs@COFs have a Tafel slope of 84 mV·dec−1, an onset overpotential of 105 mV, and ideal stability. Remarkably, CoNPs@JUC−625 required only 146 mV of overpotential to afford a current density of 10 mA cm−2. This research will open up new avenues for making COF-supported ultrafine MNPs with good dispersity and stability for extensive applications.

Efficient ORR catalysts for zinc-air battery: Biomass-derived ultra-stable Co nanoparticles wrapped with graphitic layers via optimizing electron transfer

The poor stability of non-noble metal catalysts in oxygen reduction reaction (ORR) is a main bottleneck that limits their big-scale application in metal-air batteries. Herein, we construct a chainmail catalyst (Co-NC-AD) with outstanding stability, via the competitive complexation and post absorption strategy, consisting of highly graphitic layers wrapped uniform-size Co nanoparticles (Co-NPs). Experiments combined with density functional theory (DFT) calculations jointly confirmed that the electron transfer occurred from the inner Co-NPs to the external graphitic layers. It facilitated the adsorption process of oxygen molecules and the hybridization of the O-2p and C-1p orbitals, which accelerated the ORR reaction kinetics. Consequently, our prepared Co-NC-AD shows excellent ORR activity, offered with a more positive initial potential (Eonset = 0.95 V) and half-wave potential (E1/2 = 0.86 V). The remarkable stability and resistance of methanol poisoning are merited from the protection effect of stable graphitic layers. In addition, the high electrochemical performance of Co-NC-AD-based zinc-air battery demonstrates their potential for practical applications. Therefore, our work provides new ideas for the design of nano-confined catalysts with high stability and activity.

Eco-friendly and acid-resistant magnetic porous carbon derived from ZIF-67 and corn stalk waste for effective removal of imidacloprid and thiamethoxam from water

Neonicotinoids, extensively present in water environment, can adversely affect the ecological safety and human health. Herein, a low-cost magnetic porous carbon ZIF-67/CS@C derived from ZIF-67 and agricultural waste corn stalk (CS) is designed and applied for adsorptive removal of imidacloprid and thiamethoxam from water. The adsorbent is fabricated by carbonizing ZIF-67/CS hybrid pre-prepared through an in-situ decoration of ZIF-67 on the surface of CS, and then acid picking to elute the unstable constituents. In the carbonization, Co2+ ions are reduced to magnetic Co0 nanoparticles, with the result that ZIF-67/CS@C shows a strong magnetic response (saturation magnetization intensity is 12.25 emu‧g−1) and can be easily magnetically separated. Meanwhile, Co nanoparticles are protectively encapsulated in well-developed graphitized wall, which endows ZIF-67/CS@C with good acid resistance (only 0.23% of Co is leached out at pH 1.0). More importantly, reasonable pore size distribution (most pore sizes match or are 3–6 times that of imidacloprid and thiamethoxam) and high external surface area (280 m2‧g−1) are obtained, which makes ZIF-67/CS@C super adsorbent. The adsorption capacities for imidacloprid and thiamethoxam can reach as high as 189 and 133 mg‧g−1, respectively. Moreover, after six consecutive recycling processes, the adsorption efficiencies are still above 95%, which reveals excellent reusability of ZIF-67/CS@C. Mechanism analysis affirms that pore-filling, H-bond, and π-π EDA interaction are mainly responsible for driving imidacloprid and thiamethoxam adsorption. Finally, ZIF-67/CS@C with a great security towards Daphnia carinata survival and wheat growth is eco-friendly. This study can be easily adapted to different biomass wastes and MOFs, thus potentially enabling the preparation of more novel adsorbents.

In situ photodeposition of cobalt nanoparticles onto ZnIn2S4 enhancing H2 production under visible light

Hydrogen production via semiconductor photocatalysis has been the subject of extensive research over the past four decades. Recently, much work has focused on ZnIn2S4 (ZIS), due to its ability to initiate water splitting under visible light. In this work, we report a 11-fold increase of H2 production via Co2+ addition (equivalent to 4 wt% Co on ZIS). Reaction was conducted under a 420 nm LED lamp in presence of triethanolamine. During the photocatalytic reaction, Co2+ ions were quickly reduced into metallic Co. A five-repeat test showed that the in situ Co0 nanoparticles was relatively stable. By contrast, 4 wt% Co0ex situ deposited ZIS via a (photo)chemical or physical route had a low activity, due to partial oxidation of Co0 into less active CoOx in air. Impressively, all Co-deposited ZIS samples were at least 5 times more active than 0.5 wt% Pt-loaded g-C3N4, CdS, ZnS, and In2S3, respectively. Through photoluminescence and (photo)electrochemical measurement, a plausible mechanism is proposed, involving electron transfer from ZIS to Co species, followed by proton reduction. This work shows that cobalt nanoparticles are excellent cocatalysts for H2 production on ZIS under visible light, but they are better produced in situ without involvement of O2.

Novel nanoformulated diethyldithiocarbamate complexes with biosynthesized or green chemosynthesized copper oxide nanoparticles: An in vitro comparative anticancer study

Developing more soluble and stable nanoformulation for the potent anticancer complex of copper diethyldithiocarbamate (CD) is extremely desired. Herein, for the first time, CD nanoparticles (NPs) were formulated by chelating diethyldithiocarbamate to bacterially and green chemically prepared copper oxide NPs (Bio CO NPs and Chemo CO NPs, respectively). Chemo CO NPs were produced in simpler and less time-consuming manner with higher NPs homogeneity. These CO NPs were identified, by X-ray diffractometer, as CuO and Cu2O, respectively. The nanoformulated CD complexes (Bio CD NPs and Chemo CD NPs) which have nanosizes (215.7 nm and 148.1 nm, respectively) with negative zeta potentials (∼−20 mv), exhibited not only high serum stability and solubility but also a potent anticancer effect. More importantly, Chemo CD NPs outperformed Bio CD NPs in the terms of synergistic anticancer index, apoptosis induction (>81% and <54%, respectively) and anti-migration efficacy (≥80% and <71%, respectively). This could be attributed to smaller nanosize and Cu2O of Chemo CD NPs causing higher cellular uptake with stronger inhibition of aldehyde dehydrogenase 1A1 and more free radical generation in Chemo CD NPs-treated cancer cells than Bio CD NPs. This distinct anticancer efficacy of novel Chemo CD NPs deserves further investigation using animal models.

Catalytic degradation of antibiotic by Co nanoparticles encapsulated in nitrogen-doped nanocarbon derived from Co-MOF for promoted peroxymonosulfate activation

Simultaneously rational optimization and design of the structure and composition are extremely significant approaches to further improve the performances of catalysts. Herein, a novel magnetic material (C-Co-TN) of Co nanoparticles encapsulated in nitrogen-doped nanocarbon was successfully fabricated as a peroxymonosulfate (PMS) activation catalyst. The derivative C-Co-TN was obtained from one new MOFs of Co-TN (Co(TTPA)(4-Nba)(H2O)2]·4-Nba·0.5DMF, TTPA = tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine) as a precursor for the first time, in which the Co ions and N-ligands of Co-TN were respectively transformed to Co nanoparticles and nitrogen-doped carbon layer via a one-step pyrolysis. The C-Co-TN with a large specific surface area (258.40 m2 g−1) displayed excellent PMS activation for tetracycline hydrochloride (TCH) degradation with 93.3% efficiency within 30 min superior to the pure Co-TN, in which the obtained kinetic constant for TCH removal in the C-Co-TN/PMS system was 3 times greater than Co-TN/PMS system. The final degradation rate of TCH was maintained above 94% in a wide pH range of 4–9, and 47% of TOC could be eliminated. The higher TCH removal efficiency was attributed to Co0 nanoparticles, Co-Nx/pyridinic N and graphitic N in C-Co-TN as catalytic active sites. The SO4·−, ·OH, O2·− and 1O2 were coexisted in C-Co-TN/PMS system. The work not only provides a possibility for converting MOFs into magnetic catalyst with excellent catalytic performance for water remediation, but also gives underlying insight in non-free radical pathways of heterogeneous catalysis induced by nitrogen-doped porous carbon.