Unraveling the Structural Evolution of Aluminum Polyoxocations in Solution.

The primary objective within the realm of aluminum solution chemistry is to elucidate the structural changes in aluminum polyoxocations under the influence of altered solution conditions. Notably, previous reports are primarily focused on specific types, such as aluminum monomers, species from the Keggin series, and the planar Flat-Al1315+ (F-Al13) cluster. As a result, there is a lack of comprehensive understanding of the remaining aluminum polyoxocations and their respective transformation pathways. In response to this lack, we adopt a combined experimental and theoretical approach to explore the spectral properties of aluminum polyoxocations. Specifically, we analyze infrared spectra, Raman spectra, and aluminum-27 nuclear magnetic resonance (27Al NMR) spectra. Notably, the changes in the spectral features originate from varying solution basicity levels. Through our findings, we can categorize the Al-O clusters into three primary groups: Al(H2O)63+ (Al1), ε-Keggin-[AlO4Al12(OH)24(H2O)12]7+ (ε-Al13), and 6-coordinated aluminum species. Notably, the Raman spectra exhibit prominent peak shifts at 559 and 595 cm-1, indicating the existence of Al3(1) intermediates during the transition from the Al monomer to the ε-Al13 cluster. Overall, this paper presents a comprehensive summary of the possible mechanisms that govern the formation of ε-Al13 from Al3(1), offering a clearer picture of the aluminum polyoxocation landscape and its dynamics under various solution conditions.

Cations Induced Fluorescence Enhancement in Keggin-Al13 for Quantitative Detection.

The Keggin-Al13 hydroxide clusters serve as pivotal models for elucidating molecular pathways in geochemical reactions. In this study, we presented a strategy aiming at the quantitative detection of ε-Al13 Keggin clusters using photoluminescent spectra. Specifically, we manipulate the electronic structure of ε-Al13 by introducing Na ions onto the ε-Al13 surface, encapsulated within a Na-O3 motif. The Na-ion-modified ε-Al13 (Na-ε-Al13) cluster demonstrates incredible photoluminescent qualities, with fluorescence excitation and emission peaks centered at 365 and 436 nm, respectively. In addition, the fluorescence intensities display a linear dependence on the concentrations of Na-ε-Al13, with a detection limit of 15.4 µM. This correlation facilitates the quantitative and precise determination of Na-ε-Al13 concentrations via fluorescence. Both experimental characterizations and theoretical calculations underscore the importance of decorated Na ions in regulating the electronic structure of the ε-Al13 cluster. Lastly, the influence of external anions/cations on the photoluminescent properties of ε-Al13 primarily mirrors modifications to the nonradiative decay process, which is regulated via electrostatic interactions. This work demonstrates an effective strategy for quantitative detection of the ε-Al13 Keggin clusters through photoluminescent spectra.

Unexpected Photoinduced Room Temperature Magnetization in Bi2 WO6 Nanosheets.

The current investigation in magnetism in 2D materials offers new opportunities for studying spintronics at low dimensions. Here, reversible photoinduced room temperature magnetization in 2D Bi2 WO6 nanosheets is reported for the first time. Compared with the original state, the ultraviolet (UV)-illuminated Bi2 WO6 nanosheets show a yellow-green color change and significantly enhanced magnetic signals (saturated magnetization (Ms ) increased from 0.002 to 0.12 emu g-1 ). X-ray photoelectron spectroscopy (XPS) results show unexpected W reduction (W6+ to W5+ /W4+) and Bi oxidation (Bi3+ to Bi5+ ) upon UV illumination for the Bi2 WO6 nanosheets, indicating a photoexcited Bi to W charge transfer. Density functional theory (DFT) calculations indicate spontaneous spin polarization of the Bi2 WO6 nanosheets in the excited metastable state. Meanwhile, thicker Bi2 WO6 nanoplates or nanoparticles show no enhanced magnetic signals upon UV illumination. UV illumination of the thin Bi2 WO6 nanosheets can induce the formation of internal electric field (polarization), leading to structural deformation/lattice distortion (photostriction). The photoexcited electrons are trapped in the WO6 layers while the photogenerated holes are trapped in the Bi2 O2 layers, leading to spin polarization and enhance the magnetization. The research may bring some new insights in tuning the magnetic properties of 2D nanostructures.

Enhanced Catalytic Activity in Liquid-Exfoliated FeOCl Nanosheets as a Fenton-Like Catalyst.

A facile liquid-phase exfoliation method to prepare few-layer FeOCl nanosheets in acetonitrile by ultrasonication is reported. The detailed exfoliation mechanism and generated products were investigated by combining first-principle calculations and experimental approaches. The similar cleavage energies of FeOCl (340 mJ m(-2) ) and graphite (320 mJ m(-2) ) confirm the experimental exfoliation feasibility. As a Fenton reagent, FeOCl nanosheets showed outstanding properties in the catalytic degradation of phenol in water at room temperature, under neutral pH conditions, and with sunlight irradiation. Apart from the increased surface area of the nanosheets, the surface state change of the nanosheets also plays a key role in improving the catalytic performance. The changes of charge density, density of states (DOS), and valence state of Fe atoms in the exfoliated FeOCl nanosheets versus plates illustrated that surface atomistic relationships made the few-layer nanosheets higher activity, indicating the exfoliation process of the FeOCl nanosheets also brought about surface state changes.

Effects of inorganic acids and divalent hydrated metal cations (Mg(2+), Ca(2+), Co(2+), Ni(2+)) on γ-AlOOH sol-gel process.

In-depth understanding of the sol-gel process plays an essential role in guiding the preparation of new materials. Herein, the effects of different inorganic acids (HCl, HNO3 and H2SO4) and divalent hydrated metal cations (Mg(2+), Ca(2+), Co(2+), Ni(2+)) on γ-AlOOH sol-gel process were studied based on experiments and density functional theory (DFT) calculations. In these experiments, the sol originating from the γ-AlOOH suspension was formed only with the addition of HCl and HNO3, but not with H2SO4. Furthermore, the DFT calculations showed that the strong adsorption of HSO4(-) on the surface of the γ-AlOOH particles, and the hydrogen in HSO4(-) pointing towards the solvent lead to an unstable configuration of electric double layer (EDL). In the experiment, the gelation time sequence of γ-AlOOH sol obtained by adding metal ions changed when the ionic strength was equal to or greater than 0.198 mol kg(-1). The DFT calculations demonstrated that the adsorption energy of hydrated metal ions on the γ-AlOOH surface can actually make a difference in the sol-gel process.

Large-scale synthesis and formation mechanism study of basic aluminium sulfate microcubic crystals.

Cube-like basic aluminium sulfate crystals were prepared by a facile template-free hydrothermal strategy. The microstructures, morphologies and textural properties of as-synthesized material were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy. X-ray crystallography reveals that cubic basic aluminium sulfate possesses a single crystal nature. Chemical formation mechanism studies of sulfuric acid with γ-AlOOH were performed using a combined experimental and computational approach. Time dependent experiments reveal that formation of basic aluminium sulfate is based on the dissolution-recrystallization process, and the source of Al(3+) is from the dissolution of γ-AlOOH at high H(+) concentration. Moreover, the quantum mechanical calculations reveal that dramatic structural changes occurred in the (100) plane at high H(+) concentration, which is inferred to be the initiation of the source of Al(3+). Meanwhile, surface energy calculations can well explain the exposed plane of basic aluminium sulfate microcubes, which are consistent with the XRD results. Besides, equations to quantitatively describe the relationship between the molar amount of H(+) and the final phase are proposed, which has been confirmed by experimental results.

Field-Effect Enhancement of Non-Faradaic Processes at Interfaces Governs Electrocatalytic Water Splitting Activity.

Recognizing the essential factor governing interfacial hydrogen/oxygen evolution reactions (HER/OER) is central to electrocatalytic water-splitting. Traditional strategies aiming at enhancing electrocatalytic activities have mainly focused on manipulating active site valencies or coordination environments. Herein, the role of interfacial adsorption is probed and modulated by the topological construct of the electrocatalyst, a frequently underestimated non-Faradaic mechanism in the dynamics of electrocatalysis. The engineered Co0.75Fe0.25P nanorods, anchored with FeOx clusters, manifest a marked amplification of the surface electric field, thus delivering a substantially improved bifunctional electrocatalytic performance. In alkaline water splitting anion exchange membrane (AEM) electrolyzer, the current density of 1.0 A cm-2 can be achieved at a cell voltage of only 1.73 V for the FeOx@Co0.75Fe0.25P|| FeOx@Co0.75Fe0.25P pairs for 120 h of continuous operation at 1.0 A cm-2. Detailed investigations of electronic structures, combined with valence state and coordination geometry assessments, reveal that the enhancement of catalytic behavior in FeOx@Co0.75Fe0.25P is chiefly attributed to the strengthened adsorptive interactions prompted by the intensified electric field at the surface. The congruent effects observed in FeOx-cluster-decorated Co0.75Fe0.25P nanosheets underscore the ubiquity of this effect. The results put forth a compelling proposition for leveraging interfacial charge densification via deliberate cluster supplementation.

Functional Electrospun Nanofibrous Hybrid Materials for Colorimetric Sensors: A Review.

Electrospun nanofibrous hybrid materials have several advantageous characteristics, including easy preparation, high porosity, and a large specific surface area. Meanwhile, they can be more suitable for colorimetric detection in environmental and food areas than organic materials due to the advantages of inorganic nanomaterials, i.e., stability, low toxicity, and durability. In addition to being able to immobilize nanomaterials to avoid particle aggregation, electrospinning hybrid materials also have the advantages of high specific surface area and high porosity, which is beneficial for constructing colorimetric sensors. This review mainly summarizes the fabrication methods of electrospun nanofibrous hybrid materials and the application of electrospun nanofibrous hybrid material based colorimetric sensors. First, the preparation strategies of electrospun nanofibrous hybrid materials were discussed. Then, the applications of the obtained electrospun nanofibrous hybrid materials in the colorimetric sensors for environmental molecules in the gas and liquid phase were further investigated. Finally, this review looks forward to the development prospects and challenges of electrospun hybrid materials in practical applications of colorimetric sensors in order to support the application of colorimetric sensors in practical detection.

Synthesis of γ-AlOOH nanocrystals with different morphologies due to the effect of sulfate ions and the corresponding formation mechanism study.

The investigation of the metal oxide/inorganic ion interface at the atomic level represents a fundamental issue for the understanding of chemical and physical processes involved in several fields such as catalysis, adsorption, directed synthesis and the mechanistic study of crystal growth. In this paper, a combined hydrothermal synthesis and computational approach based on DFT theory is adopted to investigate the effects of sulfate ions on the final morphology of γ-AlOOH. The quantum mechanical calculations reveal that the sulfate ions interact with γ-AlOOH facets through surface hydroxyls and act as a morphology-directing agent. The adsorption type and chemical bonds between the sulfate ion and γ-AlOOH are discussed. The formation of nanosheets and nanorods of γ-AlOOH is controlled by thermodynamic factors. Moreover, the HR-TEM images reveal the growth directions and exposed planes of boehmite, indicating an oriented-aggregation process which is consistent with the DFT calculations. Overall, all the morphologies of boehmite suggested by the calculations are confirmed by experimental results.

Ab Initio Molecular Dynamics Study of the Proton Transfer in Hydroxyl Ion-Induced Hydrolysis of Aluminum Monomers.

The hydrolysis process of Al(H2O)63+ induced by hydroxyl ions (OH-) is significant to aluminum solution chemistry. Previous investigations of hydrolysis reactions have primarily relied on static calculations in an implicit solvent environment. Herein, we employ ab initio molecular dynamics (AIMD) to investigate the evolution process of Al(H2O)63+ under various local alkaline conditions in an explicit solvent environment. Our work demonstrates the effect of solvent water in hydrolysis reactions. Specifically, the stepwise hydrolysis reaction induced by hydroxyl ions involves water wire compression and concerted proton transfers. Dehydration reactions occur when the number of hydroxyl ligands attached to the aluminum ion (Al3+) equals or exceeds three. Moreover, the Al(H2O)n(OH)3 species exhibit unique hydrolysis and dehydration reaction characteristics compared to other species. The geometrically stable aluminum monomers determined by AIMD are Al(H2O)5(OH)12+, Al(H2O)4(OH)2+, Al(H2O)1(OH)3, and Al(OH)4-. In addition, the topological analysis analyzes the interaction between Al3+ and coordinated H2O in different configurations, indicating the weakest interaction appearing in Al(H2O)n(OH)3 species.

Alpha Al2O3 Nanosheet-Based Biphasic Aerogels with High-Temperature Resistance up to 1600 °C.

Alumina aerogels are desirable for lightweight and highly efficient thermal insulation. However, they are typically constrained by brittleness and structural collapse at high temperatures. The manufacture of alumina aerogels with ultralow thermal conductivity and excellent thermal stability at high temperatures beyond 1300 °C is still challenging. Herein, alumina aerogels with superior ultrahigh-temperature-resistant and thermal insulation were successfully prepared by assembling the α-Al2O3 nanosheets with silica sols as the high-temperature binders. Benefiting from the generation of the mullite-covered alumina biphasic structure, the α-Al2O3 nanosheet-based aerogels (ANSAs) exhibit excellent thermal and chemical stabilities even after calcination at as high as 1600 °C. The ANSAs had a low thermal conductivity (0.029 W·m-1·K-1 at room temperature), structural stability with a measured compressive strength of 0.6 MPa, and good thermal shock resistance. Furthermore, the 2D α-alumina@mullite core-shell sheets were also prepared as assembly units to construct aerogels (AMSAs). This core-shell structure can improve temperature resistance through inter-lattice suppression under continuous energy input at high temperatures. The AMSAs have a linear shrinkage of only 2.7% after calcination at 1600 °C for 30 min, further improving the temperature resistance, making them an ideal super-insulating material for applications at extremely high temperatures.

Self-Assembled MOF-on-MOF Nanofabrics for Synergistic Detoxification of Chemical Warfare Agent Simulants.

The development of protective fabrics that are capable of capturing and detoxifying a wide range of lethal chemical warfare agents (CWAs) in an efficient way is of great importance for individual protection gears/clothing. In this work, unique metal-organic framework (MOF)-on-MOF nanofabrics were fabricated through facile self-assembly of UiO-66-NH2 and MIL-101(Cr) crystals on electrospun polyacrylonitrile (PAN) nanofabrics and exhibited intriguing synergistic effects between the MOF composites on the detoxification of both nerve agent and blistering agent simulants. MIL-101(Cr), although not catalytic, facilitates the enrichment of CWA simulants from solution or air, thereby delivering a high concentration of reactants to catalytic UiO-66-NH2 coated on its surface and providing an enlarged contact area for CWA simulants with the Zr6 nodes and aminocarboxylate linkers compared to solid substrates. Consequently, the as-prepared MOF-on-MOF nanofabrics showed a fast hydrolysis rate (t1/2 = 2.8 min) for dimethyl 4-nitrophenylphosphate (DMNP) in alkaline solutions and a high removal rate (90% within 4 h) of 2-(ethylthio)-chloroethane (CEES) under environmental conditions, considerably surpassing their single-MOF counterparts and the mixture of two MOF nanofabrics. This work demonstrates synergistic detoxification of CWA simulants using MOF-on-MOF composites for the first time and has the potential to be extended to other MOF/MOF pairs, which provides new ideas for the development of highly efficient toxic gas-protective materials.

Dual-Function Detoxifying Nanofabrics against Nerve Agent and Blistering Agent Simulants.

The development of functional materials that can detoxify multiple chemical warfare agents (CWAs) at the same time is of great significance to cope with the uncertainty of CWA use in real-world situations. Although many catalysts capable of detoxifying CWAs have been reported, there is still a lack of effective means to integrate these catalytic-active materials on practical fibers/fabrics to achieve effective protection against coexistence of a variety of CWAs. In this work, by a combination of electrospinning and in situ solvothermal reaction, PAN@Zr(OH)4@MOF-808 nanofiber membranes were prepared for detoxification of both nerve agent and blistering agent simulants dimethyl 4-nitrophenyl phosphate (DMNP) and 2-chloroethyl ethyl sulfide (CEES). Under the catalytic effect of the MOF-808 component, DMNP hydrolysis with a half-life as short as 1.19 min was achieved. Meanwhile, an 89.3% CEES removal rate was obtained within 12 h by adsorption and catalysis of MOF-808 and Zr(OH)4 components at ambient conditions, respectively. PAN@Zr(OH)4@MOF-808 nanofiber membranes also showed a superior blocking effect on CEES compared to bare PAN and PAN@Zr(OH)4 nanofiber membranes. Simultaneous protection against DMNP and CEES showed effective inhibition of both simulants for at least 2 h. The preparation method also imparted intrinsically good interfacial adhesion between the components, contributing to the excellent recycling stability of PAN@Zr(OH)4@MOF-808 nanofiber membranes. Therefore, the prepared composite nanofabrics have great application potential, which provides a new idea for the construction of broad-spectrum protective detoxification materials.

Ultrasensitive electrochemical immunosensor for CA 15-3 using thionine-nanoporous gold-graphene as a platform and horseradish peroxidase-encapsulated liposomes as signal amplification.

This paper describes a novel electrochemical immunosensor using a nanoporous gold (NPG)/graphene (GN) hybrid platform combined with horseradish peroxidase (HRP)-encapsulated liposomes as labels for the sensitive detection of cancer antigen 15-3 (CA 15-3). The electrochemical detection was based on the released HRP from HRP-encapsulated liposomes toward the reduction of H(2)O(2) with the help of the thionine (TH) electron mediator. In the presence of CA 15-3, HRP@liposomes and TH-NPG-GN formed a sandwich-type immunocomplex, and the immunocomplex increased with the increment of the CA 15-3 concentration in the sample. The more CA 15-3 antigen in the sample there was, the more HRP@liposomes/anti-CA 15-3 in the immunocomplex there were. Thus, the catalytic current increased. Under optimized conditions, the linear range of the immunoassay is 2 × 10(-5) to 40 U mL(-1) with a detection limit of 5 × 10(-6) U mL(-1) CA 15-3. The CA 15-3 concentrations of the clinical serum specimens assayed by the developed immunoassay showed consistent results in comparison with those obtained by a commercially available electrochemiluminescence assay. This proposed immunoassay system had many desirable merits including sensitivity, accuracy, and minimal instrumentation required. Significantly, the new protocol may be quite promising, with potentially broad applications for clinical immunoassays.

A Solar Water-Heating Smart Window by Integration of the Water Flow System and the Electrochromic Window Based on Reversible Metal Electrodeposition.

Various smart windows with dynamic modulation of the light transmittance have been developed rapidly in recent years. However, current design of the smart windows can only modulate the indoor solar irradiation instead of effectively utilize them. Here, a solar water-heating (SWH) smart window is proposed by the integration of the traditional electrochromic window and the water flow system, which can not only provide dynamic daylight modulation but also harvest the solar energy and store them by heating water. In the SWH window, the reversible metal electrodeposition (RME) not only provides daylight modulation but also provides metal layer working as a flat-plate solar collector for energy harvesting. Compared with traditional electrochromic windows, the SWH window with a water flow system can more effectively modulate the indoor temperature, owing to the significantly enhanced tunability of the thermal irradiation from the window. Compared with water-flow windows, the RME provide a metallic layer for efficient light harvesting, up to 42% solar energy can be effectively harvested and stored as hot water. Such an SWH smart window is promising to reduce the heating, lighting, and air conditioning energy consumption, which may bring new insights in the design of the next-generation green buildings.

Integrating a Self-Floating Janus TPC@CB Sponge for Efficient Solar-Driven Interfacial Water Evaporation.

Solar-driven photothermal interfacial evaporation is considered as one of the most promising strategies in seawater desalination and wastewater treatment. In desalination, evaporation efficiency and salt resistance are regarded as two inter-constraint measures. Thus, it is still challenging to fabricate solar evaporators with both high evaporation efficiency and excellent salt resistance. In the present work, a self-floating Janus sponge composed of hydrophobic carbon black (CB) coating and hydrophilic porous thermoplastic polyurethane-carbon nanotube (TPC) nanofibrous substrate (TPC@CB) is fabricated via a simple electrospinning and gas templating expansion method. Attributing to the unique trilaminar functional architecture: the upper superhydrophobic solar-absorption coating, the intermediate ultrathin heat localization layer, and the lower cellular thermal insulation layer, the Janus TPC@CB sponge exhibits high evaporation efficiency (1.80 kg m-2 h-1 with an energy efficiency of 97.2% under 1.0 solar irradiation) and outstanding salt resistance ability. Moreover, zero liquid discharge in salt-containing wastewater treatment is realized using the Janus TPC@CB sponge as a solar-driven photothermal medium. This work provides a promising approach to seawater desalination and wastewater treatment.

Large-Scale Synthesis of Spinel Nix Mn3-x O4 Solid Solution Immobilized with Iridium Single Atoms for Efficient Alkaline Seawater Electrolysis.

Seawater electrolysis not only affords a promising approach to produce clean hydrogen fuel but also alleviates the bottleneck of freshwater feeds. Here, a novel strategy for large-scale preparing spinel Nix Mn3-x O4 solid solution immobilized with iridium single-atoms (Ir-SAs) is developed by the sol-gel method. Benefitting from the surface-exposed Ir-SAs, Ir1 /Ni1.6 Mn1.4 O4 reveals boosted oxygen evolution reaction (OER) performance, achieving overpotentials of 330 and 350 mV at current densities of 100 and 200 mA cm-2 in alkaline seawater. Moreover, only a cell voltage of 1.50 V is required to reach 500 mA cm-2 with assembled Ir1 /Ni1.6 Mn1.4 O4 ‖Pt/C electrode pair under the industrial operating condition. The experimental characterizations and theoretical calculations highlight the effect of Ir-SAs on improving the intrinsic OER activity and facilitating surface charge transfer kinetics, and evidence the energetically stabilized *OOH and the destabilized chloride ion adsorption in Ir1 /Ni1.6 Mn1.4 O4 . This work demonstrates an effective method to produce efficient alkaline seawater electrocatalyst massively.

Etching-induced highly porous polymeric carbon nitride with enhanced photocatalytic hydrogen evolution.

Photocatalytic catalysts with a large specific surface area generally can not only supply more active sites but also facilitate the surface charge separation process. Here, we present a facile method to synthesize highly porous polymeric carbon nitride by an acid etching process. Benefitting from the porous structure and enlarged specific surface area, CN-0.25H reveals an enhanced photocatalytic hydrogen evolution rate. Experimental and computational results suggest that the improved surface charge separation process mainly accounts for the enhanced photocatalytic activity, illustrating the importance of the surface area for a CN photocatalyst.

Fabrication of crystalline mesoporous metal oxides and sulfides.

Mesoporous metal oxides and sulfides were prepared by a simple solvothermal method using inorganic salts as metal sources and diethylene glycol (DEG) as solvent; they are formed by the aggregation of metal compound nanoparticles. The generality of this route to the mesoporous materials was proved by the fabrication of a series of mesoporous materials (TiO(2), ZrO(2), ZnO, In(2)O(3), ZnS, and In(2)S(3)). Due to the different morphologies of nanoparticle subunits, the as-prepared mesoporous materials had different types of mesopores, which could be revealed by the N(2) adsorption-desorption isotherms and transmission electron microscopy (TEM) images.

Bio-Inspired Polydopamine-Mediated Zr-MOF Fabrics for Solar Photothermal-Driven Instantaneous Detoxification of Chemical Warfare Agent Simulants.

Self-detoxifying fabrics are desirable forms for protection against chemical warfare agents (CWAs). Zirconium-based metal-organic frameworks (Zr-MOFs) have emerged as one of the fastest catalysts for nerve-agent hydrolysis, but there is still a lack of reliable methods to integrate them onto fibrous supports, and instantaneous detoxification remains challenging for MOF/fiber composites. Herein, we report a bio-inspired polydopamine (PDA)-mediated strategy for the preparation of Zr-MOF (UiO-66-NH2)-coated nanofiber membranes, which are capable of photothermally catalyzing the degradation of CWA simulants. UiO-66-NH2 nanocrystalline coating with high mass loading, perfect coverage, and good adhesion is readily formed on polyamide (PA)-6 nanofibers with the precoated PDA layer. The prepared PA-6@PDA@UiO-66-NH2 nanofibers display almost an order of magnitude higher turnover frequency (TOF) for the hydrolysis of the nerve agent simulant dimethyl 4-nitrophenylphosphate (DMNP) when irradiated under simulated solar light, with a half-life of only 0.5 min. Such a hydrolysis rate is significantly higher compared to that of the corresponding UiO-66-NH2 powder and UiO-66-NH2/fiber composites reported so far. This strategy may be easily generalized to other MOF/fiber pairs to achieve even higher performance and opens up new opportunities for solar photothermal catalysis in CWA protection.