Molecular Nature of Structured Water in the Light-Induced Interfacial Capacitance Changes at the Bioelectric Interface

Uncovering the function of structured water in the interfacial capacitance at the molecular level is the basis for the development of the concept and model of the electric double layer; however, the limitation of the available technology makes this task difficult. Herein, using surface-enhanced infrared absorption spectroscopy combined with electrochemistry, we revealed the contribution of the cleavage of loosely bonded tetrahedral water to the enhancement of model membrane capacitance. Upon further combination with ionic perturbation, we found that the interface hydrogen bonding environment in the stern layer was greatly significant for the light-induced cleavage of tetrahedral water and thus the conversion of optical signals into electrical signals. Our work has taken an important step toward gaining experimental insight into the relationship between water structure and capacitance at the bioelectric interface

Atomically Dispersed FeN₂ at Silica Interfaces Coupled with Rich Nitrogen Doping-Hollow Carbon Nanospheres as Excellent Oxygen Reduction Reaction Catalysts

A SiO2-assisted strategy is a promising approach to prepare high-performance oxygen reduction reaction (ORR) catalysts. In this work, atomically dispersed FeN2 on rich nitrogen doping-hollow carbon nanosphere catalysts were prepared by silica interface assists. The Fe–N/C@SiO2 catalysts with an ultrathin SiO2 layer (∼3 nm) were derived from ZIF-8@Fe/SiO2 composites. A porous SiO2 thin layer was wrapped on a ZIF-8 surface while loading Fe atoms inside silica by one-step synthesis. Different from the conventional synthetic strategy, no additional post-treatments such as etching of SiO2 coatings and second pyrolysis are required. The ORR activity and stability are highly dependent on the thickness of the SiO2 layer. The rigid SiO2 layer not only traps the volatile nitrogen species on the surface to achieve a high nitrogen doping (11.14%) but also prevents the ZIF framework from collapse, forming hierarchical porous structures. Also more importantly, single Fe atoms are anchored in situ on the outer surface of the catalysts in the form of FeN2 configuration, thus greatly boosting the ORR activities. Remarkable stability (only 1% activity attenuation after 14 h of operation) is achieved in alkaline media due to the assist of inactive silica layers

Rational Design of Yolk–Shell CuO/Silicalite-1@mSiO₂ Composites for a High-Performance Nonenzymatic Glucose Biosensor

In this study, an interface coassembly strategy is employed to rationally synthesize a yolk–shell CuO/silicalite-1@void@mSiO₂ composite consisting of silicalite-1 supported CuO nanoparticles confined in the hollow space of mesoporous silica, and the obtained composite materials were used as a novel nonenzymatic biosensor for highly sensitive and selective detecting glucose with excellent anti-interference ability. The synthesis of CuO/silicalite-1@mSiO₂ includes four steps: coating silicalite-1 particles with resorcinol-formaldehyde polymer (RF), immobilization of copper species, interface deposition of a mesoporous silica layer, and final calcination in air to decompose RF and form CuO nanoparticles. The unique hierarchical porous structure with mesopores and micropores is beneficial to selectively enrich glucose for fast oxidation into gluconic acid. Besides, the mesopores in the silica shell can effectively inhibit the large interfering substances or biomacromolecules diffusing into the void as well as the loss of CuO nanoparticles. The hollow chamber inside serves as a nanoreactor for glucose oxidation catalyzed by the active CuO nanoparticles, which are spatially accessible for glucose molecules. The nonenzymatic glucose biosensors based on CuO/silicalite-1@mSiO₂ materials show excellent electrocatalytic sensing performance with a wide linear range (5–500 μM), high sensitivity (5.5 μA·mM^–1·cm^–2), low detection limit (0.17 μM), and high selectivity against interfering species. Furthermore, the unique sensors even display a good capability in the determination of glucose in real blood serum samples

Cementing Mesoporous ZnO with Silica for Controllable and Switchable Gas Sensing Selectivity

Nanostructured ZnO semiconductors as gas sensing materials have attracted great attention due to their high sensitivities, especially to reducing gases. However, ZnO based gas sensors lack controllable sensing selectivity. Herein, for the first time novel silica-cemented mesoporous ZnO materials with different contents of silica, high surface areas, and well-interconnected pores (∼29 nm) are synthesized through the evaporation-induced co-assembly (EICA) approach, and these amorphous ZnO materials exhibit controlled selectivity to ethanol or acetone. Strikingly, pure ZnO is found to exhibit better sensitivity to ethanol than that of acetone, while 2 wt % silica cemented mesoporous ZnO exhibits oppositely a selectively higher response to acetone than that of ethanol. In situ gas chromatograph–mass spectrum (GC-MS) analysis during the sensing process, in combination with intelligent gravimetric analyzer (IGA) measurement, reveals that such a preferential enhancement of acetone sensitivity by silica modification is mainly attributed to the dramatically improved adsorption of polar acetone molecules with a larger dipole moment of 2.88 D on the silica-cemented ZnO materials with higher surface polarity imparted by rich Zn–O–Si–OH bonds, and the acetone sensing process on pure ZnO and silica-cemented ZnO is found to experience a different reaction pathway

Polymerization-Induced Colloid Assembly Route to Iron Oxide-Based Mesoporous Microspheres for Gas Sensing and Fenton Catalysis

Iron oxide materials have wide applications due to their special physicochemical properties; however, it is a great challenge to synthesize mesoporous iron oxide-based microspheres conveniently and controllably with high surface area, large pore volume, and interconnected porous structures. Herein, mesoporous α-Fe₂O₃-based microspheres with high porosity are synthesized via a facile polymerization induced colloid assembly method through polymerization of urea–formaldehyde resin (UF resin) and its simultaneously cooperative assembly with Fe­(OH)₃ colloids in an aqueous solution, followed by subsequent thermal treatment. Remarkably, by controlling the cross-linking degree of UF, pure mesoporous α-Fe₂O₃ and α-Fe₂O₃/carbon hybrid microspheres can be synthesized controllably, respectively. They exhibit a uniform spherical morphology with a particle size of around 1.0 μm, well-interconnected mesopores (24.5 and 8.9 nm, respectively), and surface area of 54.4 m²/g (pure mFe₂O₃ microspheres) and 144.7 m²/g (hybrids), respectively. As a result, mesoporous pure α-Fe₂O₃ microspheres exhibited excellent H₂S sensing performance with a good selectivity, high response to low concentration H₂S at 100 °C, and quick response (4 s)/recovery (5 s) dynamics owing to the high surface area, open mesopores, and crystalline structure of the n-type α-Fe₂O₃ semiconductor. Moreover, mesoporous α-Fe₂O₃/carbon hybrid microspheres were used as a novel Fenton-like catalyst for the decomposition of methylene blue in a mild condition and exhibit quick degradation rate, high removal efficiency (∼93% within 35 min), and stable recycling performance owing to the synergetic effect of a high surface area and the carbon-protected α-Fe₂O₃

Understanding the Role of Water in Different Solid Forms of Avibactam Sodium and Its Affecting Mechanism

Hydrates are common in pharmaceutical development, and the formation of hydrates affects the performance of the final product. However, the role that water plays in crystal packing remains unclear. In this study, Avibactam sodium, which has one dihydrate (Form E), one monohydrate (Form A), and two anhydrous forms (Form B and D), was chosen as the model compound to understand this subject. Single crystal structures of four solid forms were obtained and characterized by single X-ray diffraction. The dynamic vapor sorption experiments revealed the moisture-dependent stability increased in the order: Form B < Form D < Form A < Form E. It can be envisaged that the integration of water molecules could noticeably compensate the potential intermolecular interactions, thereby significantly improving the crystal stabilities of hydrates. Furthermore, the hydration of Form B was investigated to understand the integration of water molecules by measuring the critical hydration water activities (aw). The results indicated that both water activities and temperature are vital factors to determine the amount of water molecules existing in crystal lattice. Moreover, to probe the disintegration of water molecules, the dehydration of dihydrate was investigated in detail by solid-state transformation and solvent-mediated transformation experiments. Finally, two-step dehydration and one-step dehydration + recrystallization mechanisms of these different pathways were proposed by analyzing the transformation experiment results and the crystal structure of various solid forms

Amphiphilic Block Copolymer Templated Synthesis of Mesoporous Indium Oxides with Nanosheet-Assembled Pore Walls

A solvent evaporation induced coassembly approach combined with a comburent CaO₂-assisted calcination strategy was employed for the synthesis of ordered mesoporous indium oxides by using lab-made high-molcular weight amphiphilic diblock copolymer poly­(ethylene oxide)-<i>b</i>-polystyrene (PEO-<i>b</i>-PS) as a template, indium chloride as an indium source, and THF/ethanol as the solvent. The obtained mesoporous indium oxide materials exhibit a large pore size of ∼14.5 nm, a surface area of 48 m² g^–1, and a highly crystalline In₂O₃ nanosheets framework, which can facilitate the diffusion and transport of gas molecules. By using an integrated microheater as the chemresistance sensing platform, the obtained mesoporous indium oxides were used as sensing materials and showed an excellent performance toward NO₂ at a low working temperature (150 °C) due to their high porosity and unique crystalline framework. The limit of detection (LOD) of the microsensor based on mesoporous indium oxides can reach a concentration as low as 50 ppb of NO₂. Moreover, the microsensor shows a fast response-recovery dynamics upon contacting NO₂ gas and fresh air due to the highly open mesoporous structure and the large mesopores of the crystalline mesoporous In₂O₃

Controlled Synthesis of Ordered Mesoporous Carbon-Cobalt Oxide Nanocomposites with Large Mesopores and Graphitic Walls

Ordered mesoporous carbon (OMC)-metal oxide composites have attracted great interest due to their combination of high surface area, uniform pores, good conductivity of mesoporous carbon, and excellent photo-, electro- and chemical sensing properties of metal oxides. Herein, OMC-metal oxide composites with large mesopores and monodispersed CoO_<i>x</i> nanoparticles were synthesized via a controllable multicomponent cooperative coassembly of ultrahigh-molecular-weight poly­(ethylene oxide)-<i>block</i>-polystyrene (PEO-<i>b</i>-PS) copolymers, resol (soluble phenoic resin carbon precursor), and cobalt nitrate (cobalt oxide precursor). The obtained nanocomposites possess a face-centered cubic (fcc) mesoporous structure, large pore size (13.4–16.0 nm), high surface area (394–483 m²/g), large pore volume (0.41–0.48 cm³/g), and uniform CoO_<i>x</i> nanoparticles with tunable diameters (6.4–16.7 nm). The long chain length of amphiphilic PEO-<i>b</i>-PS template molecules contributes to large mesopores and thick pore walls that allow a controllable nucleation of metal oxides and the formation of CoO_<i>x</i> nanoparticles that are partially embedded and stabilized in the graphitic carbon walls and semiexposed in the mesopore channels, avoiding pore blockage and facilitating the mass transportation of guest molecules. The <i>in situ</i> loaded highly dispersed CoO_<i>x</i> nanoparticles promote the graphitization of carbon frameworks during the pyrolysis procedure at relative lower temperatures (∼700 °C). Due to the strong synergistic effect between the graphitic OMC with large pores and uniform active p-type CoO_<i>x</i> nanoparticles, the obtained mesoporous nanocomposite exhibit superior performance in hydrogen sensing