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The interaction of water with confining surfaces is primarily governed by the wetting properties of the wall material—in particular, whether it is hydrophobic or hydrophilic. The hydrophobicity or hydrophilicity itself is determined primarily by the atomic structure and polarity of the surface groups. In the present work, we used molecular dynamics to study the structure and properties of nanoscale water layers confined between layered metal hydroxide surfaces with a brucite-like structure. The influence of the surface polarity of the confining material on the properties of nanoconfined water was studied in the pressure range of 0.1–10 GPa. This pressure range is relevant for many geodynamic phenomena, hydrocarbon recovery, contact spots of tribological systems, and heterogeneous materials under extreme mechanical loading. Two phase transitions were identified in water confined within 2 nm wide slit-shaped nanopores: (1) at p1 = 3.3–3.4 GPa, the liquid transforms to a solid phase with a hexagonal close-packed (HCP) crystal structure, and (2) at p2 = 6.7–7.1 GPa, a further transformation to face-centered cubic (FCC) crystals occurs. It was found that the behavior of the confined water radically changes when the partial charges (and, therefore, the surface polarity) are reduced. In this case, water transforms directly from the liquid phase to an FCC-like phase at 3.2–3.3 GPa. Numerical simulations enabled determination of the amount of hydrogen bonding and diffusivity of nanoconfined water, as well as the relationship between pressure and volumetric strain. [ABSTRACT FROM AUTHOR]

An electrochemical chemical sensor for determination of uric acid (UA) with highly sensitive and widely working range was fabricated using zinc layered hydroxide-sodium dodecyl sulphate-propoxur (ZLH-SDS-PRO) nanocomposites modified with multiwall carbon nanotubes (MWCNT). Introduction of the ZLH-SDS-PRO as a conducting matrix has enhanced the conductivity of MWCNT. The ZLH-SDS-PRO/MWCNT morphology was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), meanwhile the electrochemical behaviour of UA and K3[Fe(CN)6] at ZLH-SDS-PRO/MWCNT paste electrode was studied by square wave voltammetry (SWV) and cyclic voltammetry (CV), respectively. Under the optimized experimental conditions, the electrode established linear plot for UA from 7.0 µmol/L to 0.7 mmol/L (R2 = 0.9920) and the LOD was calculated to be 4.28 µmol/L (S/N = 3). The fabricated electrochemical electrode was successfully applied to urine samples and exhibit excellent stability and reproducibility, which made it worthwhile to be explored for analytical applications.

Layered metal hydroxides (LMHs) are regarded as a novel and important class of inorganic functional materials. They have unique layered structure and variable chemical compositions that can be readily tuned. In this review, summarized are the recent advances of synthetic routes to the LMHs with designed morphology, composition, and function for electrocatalysis. Versatile products can be readily derived by hybridization, anion‐exchange, surface modification, self‐assembly, etc. More importantly, LMHs can be artificially exfoliated into unilamellar nanosheets with a molecular‐level thickness of about 1 nm versus 2D lateral size in submicrometer or micrometer scale. Molecular‐scale assembly can be then applied to fabricate superlattice‐like composites and functional nanofilms with high quality. The hydroxides can be transformed into oxides, nitrides, or other compounds via different preparation procedures, which can further extend their application prospects. In this regard, the most promising electrocatalysis‐related applications of LMHs and their derivatives are reviewed, such as oxygen evolution reaction, oxygen reduction reaction, hydrogen evolution reaction, CO2 reduction reaction, alcohol or urea electrooxidation, etc. At last, future challenges are also discussed from the aspect of synthesis and application, as well as encouraging advancements are anticipated. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) have emerged as highly competitive catalysts. However, the precise regulation of intrinsic structural parameters that account for the activity of AuNPs remains a challenge in designing high-performance electrocatalysts. Herein, the layered yttrium hydroxide (LYH) nanosheets supported AuNPs are prepared via a facile electrochemical deposition method. The tunability of morphology in LYH support and their utilization in controlling the growth of small AuNPs with uniform dispersion are emphasized. Finally, a novel sensor is constructed using flower-like AuNPs/LYH modified electrodes, which allows for simultaneous determination of the dihydroxybenzene isomers hydroquinone and catechol with good sensitivity, reproducibility and stability. The excellent performance can be attributed to the synergistic effects between AuNPs and LYHs. The strategy of depositing gold onto LYH nanosheets and the resulting high performance provide new approaches for further developing highly efficient composite electrodes across a wide range of applications. [Display omitted] • The AuNPs/LYH composites are fabricated by a facile electrochemical method. • The morphology of LYH substrate can effectively modulate both the size and distribution of AuNPs growth. • The electrode modified with flower-like AuNPs/LYH composite exhibits excellent electrochemical performance. • The novel sensor is successfully used in water samples for simultaneous determination of hydroquinone and catechol. [ABSTRACT FROM AUTHOR]

It is crucial to develop low cost, highly efficient catalysts for oxygen evolution and methanol oxidation to replace precious metal catalysts. Herein, a novel strategy for preparation of exfoliated carbon nanostructures (CNS)/metal layered double hydroxide (LDH) nanocomposites is developed via a facile electrochemical deposition. The as-prepared NiFe-LDH/CNS nanocomposite has excellent electrocatalytic activity with respect to the oxygen evolution reaction for which an overpotential of 236 mV is achieved to obtain a current density of 10 mA cm −2 on a glassy carbon electrode. Furthermore, the as-prepared NiFe-LDH/CNS and NiCo LDH/CNS nanocomposites also exhibit excellent electrocatalytic activity with respect to methanol oxidation in alkaline electrolyte and thus have multifunctional catalytic activities. [ABSTRACT FROM AUTHOR]

Bonding of two-dimensional layered metal hydroxides (LMHs) to silicone rubber (SR) is not yet common, mainly due to the hydrophilic surface and limited layer spacing of LMHs, which make it difficult to achieve uniform distribution. In this work, we modified Fe-Mg-Al LMH nanoparticles by incorporating silsesquioxane nanocages bearing anionic benzoate groups and polyethylene glycol chains (SQ–COOH) using a co-precipitation procedure. The modification step leads to an enlarged interlayer spacing for LMHs and simultaneously transforms their intrinsic hydrophilic surfaces into hydrophobic ones, originating from the rigid and bulky nature and also the intercalation capacity of the modifiers. When melt-blended with SR, this SQ–COOH-incorporating strategy allowed an enhanced LMH dispersion via an interfacial compatibilization between the elastomer matrix and the modified nanoparticles. The resulting SR/LMH@SQ–COOH composites showed the expected improvement in mechanical properties while demonstrating outstanding thermal stability and flame retardancy performance. Most importantly, the synergistic effect of Fe-Mg-Al LMH with SQ–COOH endows this SR composite with significant surface charring ability resulting in a compact and strengthened ceramic-like layer to inhibit progressive combustion, which will find application in packing and other utility. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Many researches have shown that anionic clays can be used as delivery carriers for drug or gene molecules due to their efficient cellular uptake in vitro, and enhanced permeability and retention effect in vivo. It is, therefore, highly required to establish a guideline on their potential toxicity for practical applications. The toxicity of anionic clay, layered metal hydroxide nanoparticle, was evaluated in two human lung epithelial cells, carcinoma A549 cells and normal L-132 cells, and compared with that in other human cancer cell lines such as cervical adenocarcinoma cells (HeLa) and osteosarcoma cells (HOS). The present nanoparticles showed little cytotoxic effects on the proliferation and viability of four cell lines tested at the concentrations used (<250μg/ml) within 48h. However, exposing cancer cells to high concentrations (250–500μg/ml) for 72h resulted in an inflammatory response with oxidative stress and membrane damage, which varied with the cell type (A549>HOS>HeLa). On the other hand, the toxicity mechanism seems to be different from that of other inorganic nanoparticles frequently studied for biological and medicinal applications such as iron oxide, silica, and single walled carbon nanotubes. Iron oxide caused cell death associated with membrane damage, while single walled carbon nanotube induced oxidative stress followed by apoptosis. Silica triggered an inflammation response without causing considerable cell death for both cancer cells and normal cells, whereas layered metal hydroxide nanoparticle did not show any cytotoxic effects on normal L-132 cells in terms of inflammation response, oxidative stress, and membrane damage at the concentration of less than 250μg/ml. It is , therefore, highly expected that the present nanoparticle can be used as a efficient vehicle for drug delivery and cancer cell targeting as well. [Copyright &y& Elsevier]

Ambipolar doping of metal oxides is critical toward broadening the functionality of semiconducting oxides in electronic devices. Most metal oxides, however, show a strong preference for a single doping polarity due to the intrinsic stability of particular defects in an oxide lattice. In this work, we demonstrate that layered metal hydroxide nanomaterials of Co and Ni, which are intrinsically p-doped in their anhydrous rock salt form, can be n-doped using n -BuLi as a strong electron donor. A combination of X-ray characterization techniques reveal that hydroxide vacancy formation, Li + adsorption, and varying degrees of electron delocalization are responsible for the stability of injected electrons. The doped electrons induce conductivity increases of 4-6 orders of magnitude relative to the undoped M(OH) 2 . We anticipate that chemical electron doping of layered metal hydroxides may be a general strategy to increase carrier concentration and stability for n-doping of intrinsically p-type metal oxides.