Efficient Adsorbent Derived from Phytolith-Rich Ore for Removal of Tetracycline in Wastewater.

In recent decades, the tetracycline (TC) concentration in aquatic ecosystems has gradually increased, leading to water pollution problems. Various mineral adsorbents for the removal of tetracyclines have garnered considerable attention. However, efficient adsorbents suitable for use in a wide pH range environment have rarely been reported. Herein, a phytolith-rich adsorbent (PRADS) was prepared by a simple one-step alkali-activated pyrolysis treatment using phytolith as a raw material for effectively removing TC. PRADS, benefiting from its porous structure, which consists of acid- and alkali-resistant, fast-adsorbing macroporous silica and mesoporous carbon, is highly desirable for efficient TC removal from wastewater. The results indicate that PRADS exhibited excellent adsorption performance and stability for TC over a wide pH range of 2.0-12.0 under the coexistence of competing ions, which could be attributed to the fact that PRADS has a porous structure and contains abundant oxygen-containing functional groups and a large number of bonding sites. The adsorption mechanisms of PRADS for TC were mainly attributed to pore filling, hydrogen bonding, π-π electron-donor-acceptor, and electrostatic interactions. This work could offer a novel preparation strategy for the effective adsorption of pollutants by new functionalized phytolith adsorbents.

Multifunctional Nanoclay-Based Hemostatic Materials for Wound Healing: A Review.

Bleeding to death accounts for around 30-40% of all trauma-related fatalities. Current hemostatic materials are mainly mono-functional or have insufficient hemostatic capacity. Nanoclay has been recently shown to accelerate hemostasis, improve wound healing, and provide the resulting multifunctional hemostatic materials antibacterial, anti-inflammatory, and healing-promoting due to its distinctive morphological structure and physicochemical properties. Herein, the chemical design and action mechanism of nanoclay-based hemostatic, antibacterial, and pro-wound healing materials in the context of wound healing are discussed. The physiological processes of hemostasis and wound healing to elucidate the significance of nanoclay for functional wound hemostatic dressing design are outlined. A summary of the features of various nanoclay and product types used in wound hemostatic dressings is provided. Nanoclay can be antimicrobial due to the slow release of metal ions and has an abundant surface charge allowing for high affinity for proteins and cells, which can activate the coagulation reaction or facilitate tissue repair. Nanoclay with a microporous structure can be used as drug carriers to create composites critical for inhibiting bacterial growth on wounds or promoting the regeneration of vascular, muscle, and skin tissues. Directions for further research and innovation of nanoclay-based multifunctional materials for hemostasis and tissue regeneration are explored.

Palygorskite-Derived Ternary Fluoride with 2D Ion Transport Channels for Ampere Hour-Scale Li-S Pouch Cell with High Energy Density.

Although various excellent electrocatalysts/adsorbents have made notable progress as sulfur cathode hosts on the lithium-sulfur (Li-S) coin-cell level, high energy density (WG ) of the practical Li-S pouch cells is still limited by inefficient Li-ion transport in the thick sulfur cathode under low electrolyte/sulfur (E/S) and negative/positive (N/P) ratios, which aggravates the shuttle effect and sluggish redox kinetics. Here a new ternary fluoride MgAlF5 ·2H2 O with ultrafast ion conduction-strong polysulfides capture integration is developed. MgAlF5 ·2H2 O has an inverse Weberite-type crystal framework, in which the corner-sharing [AlF6 ]-[MgF4 (H2 O)2 ] octahedra units extend to form two-dimensional Li-ion transport channels along the [100] and [010] directions, respectively. Applied as the cathode sulfur host, the MgAlF5 ·2H2 O lithiated by LiTFSI (lithium salt in Li-S electrolyte) acts as a fast ionic conductor to ensure efficient Li-ion transport to accelerate the redox kinetics under high S loadings and low E/S and N/P. Meanwhile, the strong polar MgAlF5 ·2H2 O captures polysulfides by chemisorption to suppress the shuttle effect. Therefore, a 1.97 A h-level Li-S pouch cell achieves a high WG of 386 Wh kg-1 . This work develops a new-type ionic conductor, and provides unique insights and new hosts for designing practical Li-S pouch cells.

Mineral-Enhanced Manganese Ferrite with Multiple Enzyme-Mimicking Activities for Visual Detection of Disease Markers.

Local geometric configurations of metal cations in inorganic enzyme mimics determine their catalytic behaviors, while their optimization remains challenging. Herein, kaolinite, a naturally layered clay mineral, achieves the optimization of cationic geometric configuration in manganese ferrite. We demonstrate that the exfoliated kaolinite induces the formation of defective manganese ferrite and makes more iron cations fill into the octahedral sites, significantly enhancing the multiple enzyme-mimicking activities. The steady-state kinetic assay results show that the catalytic constant of composites toward 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 are more than 7.4- and 5.7-fold higher than manganese ferrite, respectively. Furthermore, density functional theory (DFT) calculations reveal that the outstanding enzyme-mimicking activity of composites is attributed to the optimized iron cation geometry configuration, which has a higher affinity and activation ability toward H2O2 and lowers the energy barrier of key intermediate formation. As a proof of concept, the novel structure with multiple enzyme-mimicking activities amplifies the colorimetric signal, realizing the ultrasensitive visual detection of disease marker acid phosphatase (ACP), with a detection limit of 0.25 mU/mL. Our findings provide a novel strategy for the rational design of enzyme mimics and an in-depth investigation of their enzyme-mimicking properties.

Nanoclay-Modulated Interfacial Chemical Bond and Internal Electric Field at the Co3 O4 /TiO2 p-n Junction for Efficient Charge Separation.

To achieve a high separation efficiency of photogenerated carriers in semiconductors, constructing high-quality heterogeneous interfaces as charge flow highways is critical and challenging. This study successfully demonstrates an interfacial chemical bond and internal electric field (IEF) simultaneously modulated 0D/0D/1D-Co3 O4 /TiO2 /sepiolite composite catalyst by exploiting sepiolite surface-interfacial interactions to adjust the Co2+ /Co3+ ratio at the Co3 O4 /TiO2 heterointerface. In situ irradiation X-ray photoelectron spectroscopy and density functional theory (DFT) calculations reveal that the interfacial Co2+ OTi bond (compared to the Co3+ OTi bond) plays a major role as an atomic-level charge transport channel at the p-n junction. Co2+ /Co3+ ratio increase also enhances the IEF intensity. Therefore, the enhanced IEF cooperates with the interfacial Co2+ OTi bond to enhance the photoelectron separation and migration efficiency. A coupled photocatalysis-peroxymonosulfate activation system is used to evaluate the catalytic activity of Co3 O4 /TiO2 /sepiolite. Furthermore, this work demonstrates how efficiently separated photoelectrons facilitate the synergy between photocatalysis and peroxymonosulfate activation to achieve deep pollutant degradation and reduce its ecotoxicity. This study presents a new strategy for constructing high-quality heterogeneous interfaces by consciously modulating interfacial chemical bonds and IEF, and the strategy is expected to extend to this class of spinel-structured semiconductors.

Electrochemical sensing mechanism of ammonium ions over an Ag/TiO2 composite electrode modified by hematite.

Here, we demonstrate a new electrochemical sensing mechanism of ammonium ions (NH4+) involving a two-electron oxygen reduction reaction (ORR) and a hydrazine reaction. The NH4+ are electrooxidized to hydrazine by H2O2 derived from the ORR over a self-supporting Ag/TiO2 nanotube array composite electrode modified by hematite (Ag/Fe2O3/TNTs). The Ag/Fe2O3/TNT sensor exhibits a high sensitivity of 1876 µA mM-1 cm-2 with a detection limit of 0.18 µM under non-alkaline conditions, a short response time of 3 s, good reproducibility, and fine selectivity among various interferents, and is also successfully used in real water bodies to display high accuracy. Furthermore, this new mechanism has a certain universality in a range of Ag (main catalyst)/transition metal oxide (cocatalyst)/TNT sensing systems. This work offers a new design basis for the urgently needed electrochemical ammonia nitrogen sensors.

Interfacial Chemical Bond Modulation of Co3(PO4)2-MoO3-x Heterostructures for Alkaline Water/Seawater Splitting.

The development of a high current density with high energy conversion efficiency electrocatalyst is vital for large-scale industrial application of alkaline water splitting, particularly seawater splitting. Herein, we design a self-supporting Co3(PO4)2-MoO3-x/CoMoO4/NF superaerophobic electrode with a three-dimensional structure for high-performance hydrogen evolution reaction (HER) by a reasonable devise of possible "Co-O-Mo hybridization" on the interface. The "Co-O-Mo hybridization" interfaces induce charge transfer and generation of fresh oxygen vacancy active sites. Consequently, the unique heterostructures greatly facilitate the dissociation process of H2O molecules and enable efficient hydrogen spillover, leading to excellent HER performance with ultralow overpotentials (76 and 130 mV at 100 and 500 mA cm-2) and long-term durability of 100 h in an alkaline electrolyte. Theoretical calculations reveal that the Co3(PO4)2-MoO3-x/CoMoO4/NF promotes the adsorption/dissociation process of H2O molecules to play a crucial role in improving the stability and activity of HER. Our results exhibit that the HER activity of non-noble metal electrocatalysts can be greatly enhanced by rational interfacial chemical bonding to modulate the heterostructures.

Nanoscale Interactions of Humic Acid and Minerals Reveal Mechanisms of Carbon Protection in Soil.

The concentrations of terrestrially sourced dissolved organic matter (DOM) have expanded throughout aquatic ecosystems in recent decades. Although sorption to minerals in soils is one major pathway to sequestrate soil organic matter, the mechanisms of organic matter-mineral interactions are not thoroughly understood. Here, we investigated the effect of calcium phosphate mineralization on humic acid (HA) fixation in simulated soil solutions, either with or without clay mineral montmorillonite (Mt). We found that Mt in solution promoted nucleation and crystallization of calcium phosphate (CaP) due to amorphous calcium phosphate clustering and coalescence on Mt surface, which contributed to the long-term persistence and accumulation of HA. Organic ligands with specific chemical groups on HA have higher binding energies to CaP-Mt than to CaP/Mt, according to dynamic force spectroscopy observations. Moreover, CaP-Mt formed in solution showed a great capacity for HA adsorption with a maximum adsorption quantity of 156.89 mg/g. Our findings directly support that Mt is crucial for DOM sequestration by facilitating CaP precipitation/transformation. This has an impact on how effectively we understand the long-term turnover of DOM and highlights knowledge gaps that might assist in resolving essential soil C sequestration issues.

Nanoclay Modulates Cation Occupancy in Manganese Ferrite for Catalytic Antibacterial Treatment.

Controllable preparation is the current frontier in the field of inorganic nanomaterial-based artificial enzymes (nanozymes). For ferrites, the factors affecting cation occupancy are very complex, making the modulation of cation occupancy extremely challenging. Herein, we report a new strategy to modulate the cation occupancy of manganese ferrite (MFO) based on the structural properties of nanoclay (i.e., montmorillonite K10). It demonstrates that montmorillonite K10 mainly changes the valence state and occupancy of manganese ions in manganese ferrite and not iron ions. K10 increases the proportion of Mn (II) in manganese ferrite and causes more manganese ions to migrate to the tetrahedral sites. As expected, the prepared new inorganic compound possesses excellent enzyme-like catalytic activities and antibacterial functional properties, which are attributed to Mn (II) accelerating Fe (III) reduction and hydroxyl radical formation. Furthermore, steady-state kinetic assays are used to study the reaction mechanism in detail. In vitro and in vivo antibacterial experiments show that the synthesized inorganic compounds exhibit satisfactory disinfection and wound skin recovery efficiencies. This work emphasizes the controllable preparation of new inorganic compounds with biomimetic activity and provides novel insight into the biological effects of inorganic nanomaterials.

Surface acidity modulates the peroxidase-like activity of nanoclay.

A novel surface acidity modulation strategy allows us to obtain modified nanoclay with specific peroxidase (POD)-like catalytic activity. Fe3+ exchange could increase the surface acidity of modified montmorillonite (MMT), resulting in a significant enhancement of its POD-like activity. We proposed that the POD-like catalytic reaction followed the electron transfer pathway and ping-pong mechanism. Correspondingly the constructed colorimetric sensor for H2O2 exhibited high sensitivity and specificity.