Doping Regulation Stabilizing δ-MnO2 Cathode for High-Performance Aqueous Aluminium-ion Batteries.

δ-MnO2 is a promising cathode material for aqueous aluminium-ion batteries (AAIBs) for its layered crystalline structure with large interlayer spacing. However, the excellent Al ion storage performance of δ-MnO2 cathode remains elusive due to the frustrating structural collapse during the intercalation of high ionic potential Al ion species. Here, it is discovered that introducing heterogeneous metal dopants with high bond dissociation energy when bonded to oxygen can significantly reinforce the structural stability of δ-MnO2 frameworks. This reinforcement translates to stable cycling properties and high specific capacity in AAIBs. Vanadium-doped δ-MnO2 (V-δ-MnO2 ) can deliver a high specific capacity of 518 mAh g-1 at 200 mA g-1 with remarkable cycling stability for 400 cycles and improved rate capabilities (468, 339, and 285 mAh g-1 at 0.5, 1, and 2 A g-1 , respectively), outperforming other doped δ-MnO2 materials and the reported AAIB cathodes. Theoretical and experimental studies indicate that V doping can substantially improve the cohesive energy of δ-MnO2 lattices, enhance their interaction with Al ion species, and increase electrical conductivity, collectively contributing to high ion storage performance. These findings provide inspiration for the development of high-performance cathodes for battery applications.

Steam activation of porous concave polymer nanospheres for high-efficient chromium and cadmium removal.

The issue of heavy metal contamination in water is a global concern, and the development of highly efficient adsorbent materials is crucial for the removal and detoxification of heavy metals. Polymer-based materials have emerged as a promising class of adsorbents due to their ability to capture heavy metal pollutants and reduce them to less toxic forms. The limited surface area of conventional polymer adsorbents makes them less effective for high-capacity adsorption. Herein, we present a low-temperature steam activation approach to address this challenge. This activation approach leads to a remarkable increase of over 20 times in the surface area of concave aminophenol-formaldehyde (APF) polymer nanospheres (from 45 to 961 m2/g) while preserving their reductive functional groups. The activated concave APF nanospheres were evaluated for their adsorption capabilities towards two typical heavy metal ions (i.e., Cr(VI) and Cd(II)) in aqueous solutions. The maximum adsorption capacities achieved were 1054 mg g-1 for Cr(VI) and 342 mg g-1 for Cd(II), which are among the highest performances reported in the literature and are much higher than the capacities of the non-activated APF nanospheres. Additionally, approximately 71.5 % of Cr(VI) was simultaneously reduced to Cr(III) through the benzenoid amine pathway during adsorption, highlighting the crucial role of the steam activation strategy in enhancing the capability of polymer adsorbents.

Confined growth of ZIF-8 in dendritic mesoporous organosilica nanoparticles as bioregulators for enhanced mRNA delivery in vivo.

Zeolitic imidazolate framework-8 (ZIF-8) and its composites have diverse applications. However, ZIF-8-based nanocomposites are mainly used as carriers in biomolecular delivery, with the functions of metal ions and ligands rarely used to modulate the biofunctions. In this work, dendritic mesoporous organosilica nanoparticles (DMONs) with tetrasulfide bond were used to confine ZIF-8 growth partially inside mesopores as a novel nanocomposite for mRNA delivery. Each component in the resultant DMONs-ZIF-8 contributed to mRNA delivery applications, including high loading benefitting from positively charged ZIF-8 and large mesopores of DMONs, endosomal escape promoted by the imidazole ring of ZIF-8, and long-term glutathione depletion mediated by both zinc ions and tetrasulfide bond. Combined together, DMONs-ZIF-8 demonstrated enhanced mRNA translation and better transfection efficiency than commercial products and toxic polymer-modified DMONs in vitro and in vivo.

Rational Design of Dendritic Mesoporous Silica Nanoparticles' Surface Chemistry for Quantum Dot Enrichment and an Ultrasensitive Lateral Flow Immunoassay.

Lateral flow immunoassays (LFIAs) have drawn much attention in point-of-care diagnostic applications, and the development of high-performance label materials is the key. In this study, the impact of the surface chemistry of dendritic mesoporous silica nanoparticles (DMSNs) on their enrichment performance toward quantum dots (QDs) and signal amplification of the resultant DMSNs-QDs as label materials have been investigated. A series of DMSNs with controllable amino/thiol group densities have been synthesized. It is demonstrated that the amino groups are beneficial for QD fluorescence preservation, owing to the amino-based surface passivation, while the thiol groups are responsible for increasing the loading capacity of QDs due to the thiol-metal coordination. The optimized DMSNs-QDs labels with an amino density of 153 µmol g-1 and a thiol density of 218 µmol g-1 displayed sufficient QD fluorescence preservation (89.4%) and high QD loading capacity (1.55 g g-1). Ultrasensitive detection of serum amyloid A (SAA) with a detection limit of 10 pg mL-1 with the naked eye was achieved, which is 1 order of magnitude higher than that reported in the literature. This study provides insights into the development of advanced label materials and an ultrasensitive LFIA for future bioassay applications.

Nitrogen-Doped Mesoporous Carbon Microspheres by Spray Drying-Vapor Deposition for High-Performance Supercapacitor.

Nitrogen-doped mesoporous carbon microspheres have been successfully synthesized via a spray drying-vapor deposition method for the first time, using commercial Ludox silica nanoparticles as hard templates. Compared to freeze-drying and air-drying methods, mesoporous carbon with a higher packing density can be achieved through the spray drying method. Vapor deposition of polypyrrole followed by carbonization and etching is beneficial for the generation of ultra-thin carbon network. The mesoporous carbon microspheres possess a mesopore-dominate (95%) high surface area of 1528 m2 g-1, a wall thickness of 1.8 nm, and a nitrogen content of 8 at% in the framework. Benefiting from the increased apparent density, high mesopore surface area, and considerable nitrogen doping, the resultant mesoporous carbon microspheres show superior gravimetric/volumetric capacitance of 533.6 F g-1 and 208.1 F cm-3, good rate performance and excellent cycling stability in electric double-layer capacitors.

Shaping Nanoparticles for Interface Catalysis: Concave Hollow Spheres via Deflation-Inflation Asymmetric Growth.

Hollow spheres are charming objects in nature. In this work, an unexpected deflation-inflation asymmetric growth (DIAG) strategy is reported, generating hollow nanoparticles with tailored concave geometry for interface catalysis. Starting from aminophenol-formaldehyde (APF) nanospheres where the interior crosslinking degree is low, fully deflated nanobowls are obtained after etching by acetone. Due to APF etching and repolymerization reactions occuring asymmetrically within a single particle, an autonomous inflation process is observed similar to a deflated basketball that inflates back to a "normal" ball, which is rare at the nanoscale. A nucleophilic addition reaction between acetone and APF is elucidated to explain the chemistry origin of the DIAG process. Interestingly, the deflated APF hollow spheres enable preferential immobilization of lipase in the concave domain, which facilitates the stabilization of Pickering emulsion droplets for enhanced enzymatic catalysis at the oil-water interface. The study provides new understandings in the designable synthesis of hollow nanoparticles and paves the way toward a wide range of applications of asymmetric architectures.

Lyophilization enabled disentanglement of polyethylenimine on rambutan-like silica nanoparticles for enhanced plasmid DNA delivery.

Polyethylenimine (PEI) functionalization onto nanoparticles is a widely used strategy for constructing particulate vectors for gene delivery. However, how to control the conformation of PEI chains and the resultant impact on gene transfection efficiency remains largely unexplored. Herein, we report that drying methods dramatically affect the conformation of PEI chains modified on the surface of silica nanoparticles and consequently the plasmid DNA transfection performance. Specifically, lyophilization renders less entangled PEI compared to commonly used vacuum drying as evidenced by an elevated glass transition temperature. The lyophilization induced disentangled conformation is likely associated with the solid-to-gas phase transition drying mechanism, which removes the bound crystal water content and thus reduces hydrogen bonding between amines. Moreover, we find that the stretched PEI chains on the surface of rambutan-like silica nanoparticles promote their binding capacity towards plasmid DNA molecules and thereby enhanced gene delivery and transfection efficiency. Our findings have provided new understanding about amine based polymers modified on nanoparticles, and have significant implications on the design of efficient particulate vectors for gene delivery.

Modulating Ion Diffusivity and Electrode Conductivity of Carbon Nanotube@Mesoporous Carbon Fibers for High Performance Aluminum-Selenium Batteries.

Selenium (Se)-based rechargeable aluminum batteries (RABs), known as aluminum-selenium (Al-Se) batteries, are an appealing new battery design that holds great promise for addressing the low-capacity problem of current RAB technology. However, their applications are hindered by mediocre high-rate capacity (≈100 mAh g-1 at 0.5 A g-1 ) and insufficient cycling life (50 cycles). Herein, the synthesis of mesoporous carbon fibers (MCFs) by coating mesoporous carbon with short-length mesopores and tunable mesopore sizes (2.7 to 8.9 nm) coaxially on carbon nanotubes (CNT) is reported. When compositing MCFs with Se for Al-Se batteries, a positive correlation between mesopore size and electrolyte ion diffusivity is observed, however when pore size is increased to 8.9 nm, large voids are created at the interface of CNT core and mesoporous carbon shell, leading to decreased electrode conductivity. The trade-off between ion diffusivity and interfacial connectivity/conductivity determines MCF with pore size of 7.1 nm as the best host material for Al-Se batteries. The composite cathode delivers high specific capacities (366 and 230 mAh g-1 at 0.5 and 1 A g-1 ), good rate performance, and excellent cycling stability (152 mAh g-1 after 500 cycles at 2 A g-1 ), superior over previously reported Se cathodes and other cathodes for RABs.

Fast Capture of Fluoride by Anion-Exchange Zirconium-Graphene Hybrid Adsorbent.

Fluoride contamination is a severe problem affecting the safety of drinking water around the world. High-rate adsorbent materials are particularly desirable for potable water defluoridation. Current research on fluoride adsorbent materials is primarily focused on metal-based adsorbents with high capacities. However, they generally suffer from slow adsorption kinetics due to the adsorption mechanism of a sluggish exchange between coordinated hydroxyl groups and fluoride ions. Designing metal-based adsorbents to mimic the rapid ion-exchange behavior of anion-exchange resins is a promising approach to integrate fast adsorption and high capacity for fluoride removal. Herein, a ZrO(OH)1.33Cl0.66-reduced graphene oxide (rGO) hybrid adsorbent containing exchangeable chloride ions was synthesized with the assistance of cation-π interactions. Unlike most adsorbents requiring a high surface area, this composite has a negligible surface area (1.45 m2 g-1), but can deliver a fast fluoride capture performance (reaching equilibrium in 5 min) with high adsorption rate constants of 1.05 min-1 and 0.171 mg g-1 min-1, around 10 times faster than the best result reported in the literature. Besides, ZrO(OH)1.33Cl0.66-rGO can also demonstrate a high fluoride uptake (44.14 mg g-1) and high removal efficiency (94.4%) in 35 mg L-1 fluoride solution, both among the highest performances for fluoride adsorption.