Correlation between biomedical and structural properties of Zn/Sr modified calcium phosphates.

This study investigates the correlation between the biomedical and structural properties of Zn/Sr-modified Calcium Phosphates (ZnSr-CaPs) synthesized via the sol-gel combustion method. X-ray diffraction (XRD) analysis revealed the presence of Ca10(PO4)6(OH)2 (HAp), CaCO3, and Ca(OH)2 phases in the undoped sample, while the additional phase, Ca3(PO4)2 (ß-TCP) was formed in modified samples. X-ray absorption near-edge structure (XANES) analysis demonstrated the incorporation of Sr into the lattice, with a preference for occupying the Ca1 sites in the HAp matrix. The introduction of Zn, furthermore, led to the formation of ZnO and CaZnO2 species. The ZnSr-CaPs exhibited significant antibacterial activity attributed to the generation of reactive oxygen species by ZnO, the oxidation reaction of CaZnO2, and the presence of Sr ions. Cytotoxicity tests revealed a correlation between the variation in ZnO content and cellular viability, with lower ZnO concentrations corresponding to higher cell viability. Additionally, the cooperative effects of Zn and Sr ions were found to enhance the bioactivity of CaPs, despite ZnO hindering the apatite formation process. These findings contribute to the deep understanding of the diverse role in modulating the antibacterial, cytotoxic, and bioactive properties of ZnSr-CaPs, offering potential applications in the field of biomaterials.

Unraveling the Electrocatalytic Activity in HMF Oxidation to FDCA by Fine-Tuning the Degree of NiOOH Phase Over Ni Nanoparticles Supported on Graphene Oxide.

The development of an efficient electrocatalyst for HMF oxidation to FDCA has been in the early stages. Herein, the NiNPs/GO-Ni-foam is fabricated as an electrocatalyst for FDCA production. However, the electrocatalytic performance of the untreated NiNPs/GO-Ni-foam is observed with moderate Faradaic efficiency (FE) (73.0%) and FDCA yield (80.2%). By electrochemically treating the NiNPs/GO-Ni-foam in an alkaline solution with positive potential at different treatment durations, the degree of NiOOH on metal surfaces is changed. The distinctive electrocatalytic activity obtained when using the different NiOOH degrees allows to understand the crucial impact of NiOOH species in HMF electrooxidation. Enhancing the portion of the NiOOH phase on the electrocatalyst surface improves electrocatalytic activity in terms of FE and FDCA yield up to 94.8±4.8% and 86.9±4.1%, respectively. Interestingly, as long as the NiOOH portion on the electrocatalyst surface is preserved or regenerated, the electrocatalyst performance can be intact even after several catalytic cycles. The theoretical study via density functional theory (DFT) also agrees with the experimental observations and confirms that the NiOOH phase facilitates the electrochemical transformation of HMF to FDCA through the HMFCA pathway, and the potential limiting step of the overall reaction is the oxidation of FFCA to FDCA.

Unraveling Structural and Acidic Properties of Al-SBA-15-supported Metal Phosphates: Assessment for Glucose Dehydration.

5-Hydroxymethylfurfural (5-HMF) synthesized through glucose conversion requires Lewis acid (L) site for isomerization and Brønsted acid (B) site for dehydration. The objective of this work is to investigate the influence of the metal type of Al-SBA-15-supported phosphates of Cr, Zr, Nb, Sr, and Sn on glucose conversion to 5-HMF in a NaCl-H2 O/n-butanol biphasic solvent system. The structural and acid property of all supported metal phosphate samples were fully verified by several spectroscopic methods. Among those catalysts, CrPO/Al-SBA-15 provided the best performance with the highest glucose conversion and 5-HMF yield, corresponding to the highest total acidity of 0.65 mmol/g and optimal L/B ratio of 1.88. For CrPO/Al-SBA-15, another critical parameter is the phosphate-to-chromium ratio. Moreover, DFT simulation of glucose conversion to 5-HMF on the surface of the optimized chromium phosphate structure reveals three steps of fructose dehydration on the Brønsted acid site. Finally, the optimum reaction condition, reusability, and leaching test of the best catalyst were determined. CrPO/Al-SBA-15 is a promising catalyst for glucose conversion to high-value-added chemicals in future biorefinery production.

Interfacial Reconstruction for Regulating Zn2+ Deposition toward Ultrastable Zn Metal Anodes.

Rechargeable aqueous zinc-ion batteries (AZIBs) are attracting much attention as high-density energy storage systems owing to their fascinating features with low cost, high safety, and simple manufacturing process. However, the commercialization of Zn anodes is hindered by uncontrollable dendrite growth and water-induced side reactions. Herein, a spontaneous reconstruction of a honeycomb-structural hopeite layer (ZPO) on a Zn metal anode (Zn@ZPO) is rationally developed as a functional protection interface by the liquid-phase deposition strategy. The formed ZPO layer not only promotes ion/charge transport and restrains Zn corrosion but also modulates the preferred deposition orientation of the Zn(002) nanosheet for the dendrite-free Zn anode. Accordingly, the Zn@ZPO symmetric cell exhibits satisfactory cycle lifespans of 1500 h at 1 mA·cm-2/1 mAh·cm-2 and 1400 h at 5 mA m-2/1 mAh·cm-2. When assembled with the (NH4)2V10O25·8H2O (NVO) cathode, the Zn@ZPO||NVO full cell delivers an ultrastable cycling lifespan for 25 000 cycles with a discharge capacity retention of 86.6% at 5 A·g-1. Therefore, this work will pave a novel avenue for constructing dendrite-free AZIBs.

Stable Immobilization of Nickel Ions on Covalent Organic Frameworks for Panchromatic Photocatalytic Hydrogen Evolution.

Post-coordination design on covalent organic frameworks (COFs) is an efficient strategy for elevating the photocatalytic activity of organic moiety. However, the rigid skeletons and densely layered stacking of two-dimensional (2D) COFs cannot be flexibly adapted for specific conformations of metal complexes, thereby impairing the metal-COF cooperation. Here, we adopt a solvothermal method to immobilize nickel(II) ions into a 2,2'-bipyridine-containing 2D COF, forming a stable coordination motif. Such the complex remarkably enhances the photocatalytic performance, giving an optimized H2 evolution rate of as high as 51 300 µmol h-1 g-1 , 2.5 times higher than the pristine COF. The evolved hydrogen gas can also be detected upon 700-nm light irradiation, while its analog synthesized by the traditional coordination method is photo-catalytically inert. This work provides a strategy for optimizing the metal-COF coordination system and strengthening a synergy for electronic regulation in photocatalysis.

Coordination Chemistry of Large-Sized Yttrium Single-Atom Catalysts for Oxygen Reduction Reaction.

Although being transition metals, the Fenton-inactive group 3-4 elements (Sc, Y, La, Ti, Zr, and Hf) can easily lose all the outermost s and d electrons, leaving behind ionic sites with nearly empty outermost orbitals that are stable but inactive for oxygen involved catalysis. Here, it is demonstrated that the dynamic coordination network can turn these commonly inactive ionic sites into platinum-like catalytic centers for the oxygen reduction reaction (ORR). Using density functional theory calculations, a macrocyclic ligand coordinated yttrium single-atom (YN4 ) moiety is identified, which is originally ORR inactive because of the too strong binding of hydroxyl intermediate, while it can be activated by an axial ligand X through the covalency competition between YX and YOH bonds. Strikingly, it is also found that the binding force of the axially coordinated ligand is an effective descriptor, and the chlorine ligand is screened out with an optimal binding force that behaves self-adaptively to facilitate each ORR intermediate steps by dynamically changing its YCl covalency. These experiments validate that the as-designed YN4 -Cl moieties embedded within the carbon framework exhibit a high half-wave potential (E1/2 = 0.85 V) in alkaline media, the same as that of the commercial Pt/C catalyst .

Structural elucidation of hexavalent Cr adsorbed on surfaces and bulks of Fe3O4 and α-FeOOH.

Magnetite (Fe3O4) and goethite (α-FeOOH) were synthesized via a hydrothermal approach and utilized as adsorbents for Cr6+ removal in an aqueous medium. The typical crystal structures of the synthesized Fe3O4 and α-FeOOH were confirmed by XRD and TEM. Fe3O4 in a spherical shape with a surface area of 32 m2 g-1 was established. While α-FeOOH had a rod-like form with a larger surface area of 84 m2 g-1. Cr6+ removal in an aqueous solution was studied in various conditions to evaluate thermodynamic and kinetic parameters. The adsorption isotherms on both adsorbents fit the Langmuir model indicating monolayer adsorption. Fe3O4 showed a better adsorption ability than α-FeOOH even though it had a lower surface area. XAS and XPS analysis strongly evidenced the production of stable Cr3+ species of Fe(1-x)Cr x OOH and Fe(3-x)Cr x O4 by Cr6+ reduction and migration processes into the bulk structure. Thus, the existence of stable Cr-species in Fe3O4 structure strongly affected Cr-adsorption ability rather than the surface area of the adsorbent. However, the precipitated Cr2O3 and HCrO4 - molecules electrostatically adsorbed on the outer surface of α-FeOOH without bulk transformation. The presence of physisorbed FeO-HCrO4 species on α-FeOOH led to low reducibility and adsorption capability of Cr6+.

Enhancement of V2O5 Li-ion cathode stability by Ni/Co doped Li-borate-based glass.

In this research, we investigate the stability of a Li-ion cathode created by mixing a borate based glass which has been doped with Ni/Co and vanadium pentoxide (V2O5). V2O5 has a high specific capacity in battery systems because of its layered structure and variety of oxidation states. However, due to the flimsy structure, the capacity stability of V2O5 is fairly low. In this case, we seek to overcome the problem by mixing Ni/Co-doped borate based glass. The voltage-capacity graph demonstrates that the form of the glass mix was changed from a stairway shape to a straight line while the capacity was not much decreased. The crystallography study using X-ray diffractograms looked at whether the cycling test had changed the crystal structure of V2O5. The X-ray Absorption Near Edge Structure (XANES) results also reveal that V2O5's oxidation state changed from V5+ to V4+. The glass mix can retain more of the V5+ state, indicating that glass mixture helps to release the Li-ions trapped in the structure. The findings of this study might contribute to the rapid advancement of renewable energy and electric vehicle technology.

Correlating the effect of preparation methods on the structural and magnetic properties, and reducibility of CuFe2O4 catalysts.

CuFe2O4 spinel oxide has attracted research interest because of its versatile practical applications, especially for catalysis. In this study, nanometre-sized CuFe2O4 particles were prepared by three different methods, including nanospace confinement in SBA-15, hard template removal, and sol-gel combustion. The relationship between structure, size, magnetic behaviour, and reducibility of the catalysts was further investigated by various advanced techniques. Samples prepared by impregnation and hard template removal show high surface area and small crystallite size with superparamagnetic behaviour. In contrast, the sol-gel sample exhibits ferromagnetic properties with a large crystallite size and low surface area. Although all samples present a tetragonal crystal structure, the distributions of Fe and Cu cations in tetrahedral and octahedral sites in the spinel structure are different. The reducibility results demonstrate that the supported CuFe2O4/SBA-15 shows the lowest reduction profile. These results could suggest that the synthesis method strongly affects the crystal properties and cation distribution in the spinel structure, microstructure, surface area and reducibility, which are among the most relevant physicochemical properties for the catalytic activity.

Metalloid-Cluster Ligands Enabling Stable and Active FeN4 -Ten Motifs for the Oxygen Reduction Reaction.

In nature, the oxygen reduction reaction (ORR) is catalyzed by cytochrome P450 (CYP) enzymes containing heme iron centers with an axial thiolate ligand (FeN4 -S), which are among the most finely developed catalysts by natural selection. However, the exceptional ORR activity and selectivity of CYP enzymes originate from their non-rigid and self-adaptive coordination network with molecular ligands, which sacrifices the stability of the active motifs under electrochemical reaction conditions. Here, a design strategy to circumvent this dilemma by incorporating Fe-N4 motifs into carbon matrices instead of the protein scaffold and replacing the axial molecular thiolate ligand with a stable tellurium cluster (Ten ) is demonstrated. Theoretical calculations indicate a moderate interaction between Fe 3d and Te 5p orbitals once n > 2, allowing the FeTe bond to dynamically change its strength to adaptively facilitate the intermediate steps during the ORR process, which renders FeN4 -Ten active sites with superior ORR activity. This adaptive behavior mimics the conformational dynamics of an enzyme during the reaction, but retains the stability nature as a heterogeneous catalyst. The experiments validate that the as-designed catalyst with a characterized FeN4 -Ten structure outperforms the commercial Pt/C catalyst both on activity and stability.

An Operando X-ray Absorption Spectroscopy Study on Sensing Characteristics of Vertically Aligned ZnO Thin Film for Methane Gas Sensors.

In this work, a simple, facile growth approach for a vertically aligned ZnO thin film is fabricated and its application towards methane gas sensors is demonstrated. ZnO thin film was prepared by a combination of hydrothermal and sputtering methods. First, a ZnO seed layer was prepared on the substrate through a sputtering technique, then a ZnO nanorod was fabricated using a hydrothermal method. The surface morphology of the ZnO film was observed by scanning electron microscopy (SEM). A ZnO nanorod coated on the dense seed layer is clearly visible in the SEM image. The average size of the hexagonal-shaped ZnO rod was around 50 nm in diameter, with a thickness of about 1 mm. X-ray absorption near-edge structures (XANES) were recorded to characterize the structural properties of the prepared film. The obtained normalized Zn K-edge XANES of the film showed the characteristic features of ZnO, which agreed well with the standard ZnO sample. The measurement of Zn K-edge XANES was performed simultaneously with the sensing response. The results showed a good correlation between sensor response and ZnO structure under optimal conditions.

Proton/Electron Donors Enhancing Electrocatalytic Activity of Supported Conjugated Microporous Polymers for CO2 Reduction.

Metal phthalocyanines (MePc) hold great promise in electrochemical reduction of CO2 to value-added chemicals, whereas the catalytic activity of MePc-containing polymers often suffers from a limited molecular modulation strategy. Herein, we synthesize an ultrathin conjugated microporous polymer sheath around carbon nanotubes by an ionothermal copolymerization of CoPc and H2 Pc via the Scholl reaction. Given the H2 Pc-mediated regulation in the synthesis, CoII metal is well preserved in the form of single atoms on the polymer sheath of the carbon nanotubes. With the synergistic effect of H2 Pc moieties as proton/electron donors, the composites can selectively reduce CO2 to CO with a high Faradaic efficiency (max. 97 % at -0.9 V) in broad potential windows, exceptional turnover frequency (97 592 h-1 at -0.65 V) and large current density (>200 mA cm-2 ). It is thus desirable to develop a family of heterogeneous polymerized MePc with molecularly regulating electrocatalytic activity.

Modulation of Single Atomic Co and Fe Sites on Hollow Carbon Nanospheres as Oxygen Electrodes for Rechargeable Zn-Air Batteries.

Efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are required for metal air batteries, to replace costly metals, such as Pt and Ir/Ru based compounds, which are typically used as benchmarks for ORR and OER, respectively. Isolated single atomic sites coordinated with nitrogen on carbon supports (M-N-C) have promising performance for replacement of precious metal catalysts. However, most of monometallic M-N-C catalysts demonstrate unsatisfactory bifunctional performance. Herein, a facile way of preparing bimetallic Fe and Co sites entrapped in nitrogen-doped hollow carbon nanospheres (Fe,Co-SA/CS) is explored, drawing on the unique structure and pore characteristics of Zeolitic imidazole frameworks and molecular size of Ferrocene, an Fe containing species. Fe,Co-SA/CS showed an ORR onset potential and half wave potential of 0.96 and 0.86 V, respectively. For OER, (Fe,Co)-SA/CS attained its anodic current density of 10 mA cm-2 at an overpotential of 360 mV. Interestingly, the oxygen electrode activity (ΔE) for (Fe,Co)-SA/CS and commercial Pt/C-RuO2 is calculated to be 0.73 V, exhibiting the bifunctional catalytic activity of (Fe,Co)-SA/CS. (Fe,Co)-SA/CS evidenced desirable specific capacity and cyclic stability than Pt/C-RuO2 mixture when utilized as an air cathode in a homemade Zinc-air battery.

Molecular grafting towards high-fraction active nanodots implanted in N-doped carbon for sodium dual-ion batteries.

Sodium-based dual-ion batteries (Na-DIBs) show a promising potential for large-scale energy storage applications due to the merits of environmental friendliness and low cost. However, Na-DIBs are generally subject to poor rate capability and cycling stability for the lack of suitable anodes to accommodate large Na+ ions. Herein, we propose a molecular grafting strategy to in situ synthesize tin pyrophosphate nanodots implanted in N-doped carbon matrix (SnP2O7@N-C), which exhibits a high fraction of active SnP2O7 up to 95.6 wt% and a low content of N-doped carbon (4.4 wt%) as the conductive framework. As a result, this anode delivers a high specific capacity ∼400 mAh g-1 at 0.1 A g-1, excellent rate capability up to 5.0 A g-1 and excellent cycling stability with a capacity retention of 92% after 1200 cycles under a current density of 1.5 A g-1. Further, pairing this anode with an environmentally friendly KS6 graphite cathode yields a SnP2O7@N-C||KS6 Na-DIB, exhibiting an excellent rate capability up to 30 C, good fast-charge/slow-discharge performance and long-term cycling life with a capacity retention of ∼96% after 1000 cycles at 20 C. This study provides a feasible strategy to develop high-performance anodes with high-fraction active materials for Na-based energy storage applications.

Roles of Mo dopant in Bi2WO6 for enhancing photocatalytic activities.

We present the investigation of the roles of molybdenum (Mo) dopant with a concentration of 0.0625% to 1.0% Mo into bismuth tungstate (Bi2WO6) by a one-step hydrothermal method for the enhancement of photocatalytic activities. The obtained materials and doping effects were characterized by the morphology, crystal structure, chemical states, and optical properties. By combining XRD, XANES, and EXAFS studies, the distortion of the local structure with substitutional doping was revealed as doping with Mo ions was located at the lattice sites of the tungsten ions. Photocatalytic reactions of Mo-doped Bi2WO6 were studied by the degradation of methyl orange dye under visible light irradiation. The results show that the optimal concentration of Mo dopant is 0.25%, with the highest photocatalytic activity up to ∼2-fold compared to the bare Bi2WO6. From our investigation, we propose that the impurity level is located below the conduction band edge of Bi2WO6 after doping with Mo6+ ions. This impurity level acts as an electron trapping site to prevent the transition of excited electrons from the conduction band to the valence band. By trapping experiments, the superoxide anion radicals (O2˙-) as the main active species to enhance photocatalytic efficiency was established.

Atomic layer deposition triggered Fe-In-S cluster and gradient energy band in ZnInS photoanode for improved oxygen evolution reaction.

Vast bulk recombination of photo-generated carriers and sluggish surface oxygen evolution reaction (OER) kinetics severely hinder the development of photoelectrochemical water splitting. Herein, through constructing a vertically ordered ZnInS nanosheet array with an interior gradient energy band as photoanode, the bulk recombination of photogenerated carriers decreases greatly. We use the atomic layer deposition technology to introduce Fe-In-S clusters into the surface of photoanode. First-principles calculations and comprehensive characterizations indicate that these clusters effectively lower the electrochemical reaction barrier on the photoanode surface and promote the surface OER reaction kinetics through precisely affecting the second and third steps (forming processes of O* and OOH*) of the four-electron reaction. As a result, the optimal photoanode exhibits the high performance with a significantly enhanced photocurrent of 5.35 mA cm-2 at 1.23 VRHE and onset potential of 0.09 VRHE. Present results demonstrate a robust platform for controllable surface modification, nanofabrication, and carrier transport.

Photoenhanced Water Electrolysis in Separate O2 and H2 Cells Using Pseudocapacitive Electrodes.

Water electrolysis has received much attention in recent years as a means of sustainable H2 production. However, many challenges remain in obtaining high-purity H2 and making large-scale production cost-effective. This study provides a strategy for integrating a two-cell water electrolysis system with solar energy storage. In our proposed system, CuO-Cu(OH)2/Cu2O was used as a redox mediator between oxygen and hydrogen evolution components. The system not only overcame the gas-mixing issue but also showed high gas generation performance. The redox reaction (charge/discharge) of CuO-Cu(OH)2/Cu2O led to a significant increase (51%) in the initial rate of H2 production from 111.7 µmol h-1 cm-2 in the dark to 168.9 µmol h-1 cm-2 under solar irradiation. The effects of light on the redox reaction of CuO-Cu(OH)2/Cu2O during water electrolysis were investigated by in situ X-ray absorption and photoemission spectroscopy. These results suggest that surface oxygen vacancies are created under irradiation and play an important role in increased capacitance and gas generation. These findings provide a new path to direct storage of abundant solar energy and low-cost sustainable hydrogen production.

A Redox Cu(II)-Graphene Oxide Modified Screen Printed Carbon Electrode as a Cost-Effective and Versatile Sensing Platform for Electrochemical Label-Free Immunosensor and Non-enzymatic Glucose Sensor.

A novel copper (II) ions [Cu(II)]-graphene oxide (GO) nanocomplex-modified screen-printed carbon electrode (SPCE) is successfully developed as a versatile electrochemical platform for construction of sensors without an additionally external redox probe. A simple strategy to prepare the redox GO-modified SPCE is described. Such redox GO based on adsorbed Cu(II) is prepared by incubation of GO-modified SPCE in the Cu(II) solution. This work demonstrates the fabrications of two kinds of electrochemical sensors, i.e., a new label-free electrochemical immunosensor and non-enzymatic sensor for detections of immunoglobulin G (IgG) and glucose, respectively. Our immunosensor based on square-wave voltammetry (SWV) of the redox GO-modified electrode shows the linearity in a dynamic range of 1.0-500 pg.mL-1 with a limit of detection (LOD) of 0.20 pg.mL-1 for the detection of IgG while non-enzymatic sensor reveals two dynamic ranges of 0.10-1.00 mM (sensitivity = 36.31 µA.mM-1.cm-2) and 1.00-12.50 mM (sensitivity = 3.85 µA.mM-1.cm-2) with a LOD value of 0.12 mM. The novel redox Cu(II)-GO composite electrode is a promising candidate for clinical research and diagnosis.

K-Ion Battery Cathode Design Utilizing Trigonal Prismatic Ligand Field.

The intrinsic physical and chemical properties of materials are largely governed by the bonding and electronic structures of their fundamental building units. The majority of cathode materials contain octahedral TMO6 (TM = transition metal), which dominates the redox chemistry during electrochemical operation. As a less symmetric form of TMO6 , the trigonal prismatic geometry is not a traditionally favored coordination configuration as it tends to lose the crystal-field stabilization energy and thus generate large ligand repulsion. Herein, a K-ion battery cathode design, K2 Fe(C2 O4 )2 , is shown​, where the TMO6 trigonal prism (TP) is not only electrochemically active but stable enough to allow for excellent cycling stability. Detailed synchrotron X-ray absorption spectroscopy measurements reveal the evolution of localized fine structure, evidencing the electrochemical activity, reversibility, and stability of the TP motif. The findings are expected to expand the toolbox for the rational design of electrode materials by taking advantage of TP as a structural gene.

Copper/reduced graphene oxide film modified electrode for non-enzymatic glucose sensing application.

Numerous studies suggest that modification with functional nanomaterials can enhance the electrode electrocatalytic activity, sensitivity, and selectivity of the electrochemical sensors. Here, a highly sensitive and cost-effective disposable non-enzymatic glucose sensor based on copper(II)/reduced graphene oxide modified screen-printed carbon electrode is demonstrated. Facile fabrication of the developed sensing electrodes is carried out by the adsorption of copper(II) onto graphene oxide modified electrode, then following the electrochemical reduction. The proposed sensor illustrates good electrocatalytic activity toward glucose oxidation with a wide linear detection range from 0.10 mM to 12.5 mM, low detection limit of 65 µM, and high sensitivity of 172 µA mM-1 cm-2 along with satisfactory anti-interference ability, reproducibility, stability, and the acceptable recoveries for the detection of glucose in a human serum sample (95.6-106.4%). The copper(II)/reduced graphene oxide based sensor with the superior performances is a great potential for the quantitation of glucose in real samples.