3D NiCo-Layered double Hydroxide@Ni nanotube networks as integrated free-standing electrodes for nonenzymatic glucose sensing

Nickel cobalt layered double hydroxide (NiCo-LDH)-based materials have recently emerged as catalysts for important electrochemical applications. However, they frequently suffer from low electrical conductivity and agglomeration, which in turn impairs their performance. Herein, we present a catalyst design based on integrated, self-supported nickel nanotube networks (Ni-NTNWs) loaded with NiCo-LDH nanosheets, which represents a binder-free, hierarchically nanostructured electrode architecture combining continuous conduction paths and openly accessible macropores of low tortuosity with an ultrahigh density of active sites. Similar to macroscale metallic foams, the NTNWs serve as three-dimensionally interconnected, robust frameworks for the deposition of active material, but are structured in the submicron range. Our synthesis is solely based on scalable approaches, namely templating with commercial track-etched membranes, electroless plating, and electrodeposition. Morphological and compositional characterization proved the successful decoration of the inner and outer nanotube surfaces with a conformal NiCo-LDH layer. Ni-NTNW electrodes and hydroxide-decorated variants showed excellent performance in glucose sensing. The highest activity was achieved for the catalyst augmented with NiCo-LDH nanosheets, which surpassed the modification with pure Ni(OH)₂. Despite its low thickness of 20 µm, the optimized catalyst layer provided an outstanding sensitivity of 4.6 mA mM^-1 cm^-2, a low detection limit of 0.2 µM, a fast response time of 5.3 s, high selectivity and stability, and two linear ranges covering four orders of magnitude, up to 2.5 mM analyte. As such, derivatized interconnected metal nano-networks represent a promising design paradigm for highly miniaturized yet effective catalyst electrodes and electrochemical sensors.

A facile synthesis of novel ε-Fe2O3 grafted 2D h-BN nanostructures for enhanced visible active photocatalytic applications

Solvothermally synthesized h-BN/ε-Fe₂O₃ nanocomposite catalyst exhibited enhanced photocatalytic activity compared to bare h-BN and c-BN catalysts.

Materials Nanoarchitectonics Using 2D Layered Materials: Recent Developments in the Intercalation Process

Layered inorganic solids as an attractive classification of 2D materials offer material diversity and a wide range of interesting properties. Layered inorganic solids provide an expandable 2D nanospace between each individual layer, the so called interlayer space, to accommodate/arrange guest species such as molecules, nanoparticles, and polymer chains and design unique nanoarchitectures, resulting in the production of intercalation compounds showing different properties in comparison to those of virgin layered materials and guest species. Layered inorganic solids can also be exfoliated to result in nanosheet production. Further ordering of exfoliated nanosheets is also possible via different methods and normally leads to creating soft materials presenting properties and applications different from that of relatively rigid intercalation compounds. Here, the latest studies and up-to-date developments on the possible techniques of designing novel types of materials using layered inorganic solids are specifically highlighted.

Templated synthesis of atomically-thin Ag nanocrystal catalysts in the interstitial space of a layered silicate

Enclosing functional nanoparticles in stable inorganic supports is important for generating ultra-stable catalytic active sites with good performance and material utilization efficiency. Here we describe a simple method to synthesize ultra-thin Ag nanocrystals with dimensions that are defined by the ∼1.4 nm 2D interlayer separating a layered silicate nanostructure. We call the particles "nanoplates" because they are <1.4 nm thick in one direction and their in-plane dimensions are defined by reaction time. The layered silicate is pillared with dialkylurea, which serves both as a reducing agent for the Ag precursor and immobilizes the Ag nanoplates in the interstitial nanospace. The supported Ag nanoplates showed catalytic activity for hydrolysis of NH3BH3 and generation of H2 at room temperature. These supported Ag nanocatalysts had performance much higher than spherical Ag nanoparticles. They, moreover, had performance and stability comparable to costly supported Pt nanoparticles.

A novel liquid template corrosion approach for layered silica with various morphologies and different nanolayer thicknesses

A novel liquid template corrosion (LTC) method has been developed for the synthesis of layered silica materials with a variety of morphologies, including hollow nanospheres, trilobite-like nanoparticles, spherical particles and a film resembling the van Gogh painting 'Starry Night'. Lamellar micelles and microemulsion droplets are first formed in an oil-water (O/W) mixture of ethyl acetate (EA), cetyltrimethylammonium bromide (CTAB) and water. After adding aqueous ammonia the EA becomes hydrolyzed, which results in corrosion of microemulsion droplets. These droplets subsequently act as templates for the synthesis of silica formed by hydrolysis of tetraethyl orthosilicate. The morphological evolution of silica can be tuned by varying the concentration of aqueous ammonia which controls the degree of corrosion of the microemulsion droplet templates. A possible mechanism is proposed to explain why the LTC approach affords layered silica nanostructured materials with various morphologies and nanolayer thickness (2.6-4.5 nm), rather than the usual ordered mesostructures formed in the absence of EA. Our method provides a simple way to fabricate a variety of building blocks for assembling nanomaterials with novel structures and functionality, which are not available using conventional template methods.

Size dependence of the magnetic properties of Ni nanoparticles prepared by thermal decomposition method

By means of thermal decomposition, we prepared single-phase spherical Ni nanoparticles (23 to 114 nm in diameter) that are face-centered cubic in structure. The magnetic properties of the Ni nanoparticles were experimentally as well as theoretically investigated as a function of particle size. By means of thermogravimetric/differential thermal analysis, the Curie temperature TC of the 23-, 45-, 80-, and 114-nm Ni particles was found to be 335°C, 346°C, 351°C, and 354°C, respectively. Based on the size-and-shape dependence model of cohesive energy, a theoretical model is proposed to explain the size dependence of TC. The measurement of magnetic hysteresis loop reveals that the saturation magnetization MS and remanent magnetization increase and the coercivity decreases monotonously with increasing particle size, indicating a distinct size effect. By adopting a simplified theoretical model, we obtained MS values that are in good agreement with the experimental ones. Furthermore, with increase of surface-to-volume ratio of Ni nanoparticles due to decrease of particle size, there is increase of the percentage of magnetically inactive layer.