A novel 2-dimensional catalytic system was developed in which platinum nanoparticles (Pt NPs) were immobilized on exfoliated MgAl-layered double hydroxide (LDH) nanosheets through an electrostatic self-assembly between negatively charged Pt NPs and positively charged LDH nanosheets. The LDH nanosheets effectively provided the large double sides of hydroxide functionality to absorb the Pt NPs, as well as fast diffusion rates of the incoming reactants into catalyst surfaces. This new nanostructure improved the rate of reaction, turnover frequency and reaction durability of Pt NPs on LDH nanosheet without significant loss in conversion efficiencies for the reduction of p-nitrophenol into p-aminophenol by NaBH 4 , maintaining more than 97% of catalytic conversions compared to free Pt NPs as well as commercial Pt/C catalyst.Owing to thermodynamically unstable surface atoms and high surface-to-volume ratio of nanomaterials, transition-metal nanoparticles (NPs) have been used in the field of the heterogeneous catalysts over the past several decades.[1] The unique characteristics of nanomaterials have consistently required developments in the surface stabilization of the individual NPs with organic molecules.[2] However, organic stabilizers could hinder most active surface sites of the metal NPs to block their catalytic functions. Immobilizations of the metal NPs on desired solid supports such as metal oxides, [1c] graphitic carbons, [3] and porous silica [4] prevent agglomeration of the metal NPs, which has led to the poisoning of catalytic activities. [5] Metal NPs on supports function in repeated recycles without organic stabilizers, maintaining high performance as heterogeneous catalysts. Nevertheless, the following common problems still exist in the development of new catalysts: (1) the use of covalent chemical linkers to bind metal NPs on the surface of solid supports, (2) loading of the metal NPs by impregnation onto the limited areas of mesoscopic supports, which produced irregular-size NPs, and (3) low dispersion capability of solid supports in solution that can restrict the practical applications of the metal NPs. Thus, the development of new types of solid supports needs a large open surface and reactive surface functionalities, which could bind to metal NPs, such as layered double hydroxides (LDH).[6] In previous reports, we demonstrated the useful application of surface potentials for the charged particles, such as zeolite crystals, proteins, polymer beads, and surface-modified LDHs, which drove their electrostatic assemblies on the as-prepared or chemically modified LDH surface to produce complex nanostructures. [7] To date, powdery LDHs as catalyst supports have been widely reported with polyoxometalates [8] and transition-metal NPs.[9] Metal NPs (e.g., Pt, Pd) impregnated into the LDHs by in situ chemical reduction of intercalated metal chlorides [9a,b] were formed on the edge surfaces of the LDH particles with an irregular size distribution, which is attributed to restricted interlayer galleries....

limitation, many studies have sought to develop bioadhesives as tissue adhesives, hemostatic agents, and wound sealants. [1] Such bioadhesives would utilize less invasive approaches for stable tissue conformability, even under undesired mechanical stresses. [2] This approach was first demonstrated using chemical-based adhesives (i.e., cyanoacrylate derivatives and fibrin glues). [1b] However, potential concerns that have been noted include loss of wet adhesion and clinical risk regarding the chemical residues (e.g., hydroxyl, amine, or carboxyl group). [3] To overcome these issues, catechol chemistry has been proposed to enable strong attachment to the target organ without losing biocompatibility. Unfortunately, potential drawbacks, such as water absorption and swelling, remain challenging because they induce mechanical weakening and adverse medical complications. [4] Recently, tough hydrogel bioadhesives based on chitosan, polyallylamine, and poly(acrylic acid) with N-hydroxysuccinimide ester bridging polymers demonstrated remarkable attachment to various human-like organs for use as hemostatic sealants, tissue repair materials, or bioelectrical interfaces. [1a,5] Although they feature high adherence and tissue conformability, their sustainability requires further study in terms of chemical contamination and/or damage during removal surgeries. [6] Recent studies on soft adhesives have sought to deeply understand how their chemical or mechanical structures interact strongly with living tissues. The aim is to optimally address the unmet needs of patients with acute or chronic diseases. Synergistic adhesion involving both electrostatic (hydrogen bonds) and mechanical interactions (capillarity-assisted suction stress) seems to be effective in overcoming the challenges associated with long-term unstable coupling to tissues. Here, an electrostatically and mechanically synergistic mechanism of residue-free, sustainable, in situ tissue adhesion by implementing hybrid multiscale architectonics. To deduce the mechanism, a thermodynamic model based on a tailored multiscale combinatory adhesive is proposed. The model supports the experimental results that the thermodynamically controlled swelling of the nanoporous hydrogel embedded in the hierarchical elastomeric structure enhances biofluid-insensitive, sustainable, in situ adhesion to diverse soft, slippery, and wet organ surfaces, as well as clean detachment in the peeling direction. Based on the robust tissue adhesion capability, universal reliable measurements of electrophysiological signals generated by various tissues, ranging from rodent sciatic nerve, the muscle, brain, and human skin, are successfully demonstrated.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202105338.

No abstract

The deintercalation of carbonate (CO32–) ions from MgAl‐layered double hydroxides (LDHs) (Mg/Al = 2) both in monolayer films and powdered samples under atmospheric conditions in ethanol was investigated. A selenous acid precursor was incorporated into the interlayer gallery. Treatment with 0.5 M selenous acid (H2SeO3) for 30 min with powdered LDHs or with 0.1 M H2SeO3 for 5 min with the thin film LDHs resulted in carbonate ions being exchanged with biselenite (HSeO3–) ions. Electron microscopy showed that the morphologies of the original LDH particles remained after the reaction, despite the ultrasound being continuously applied for up to 2 h. XRD, FTIR and Raman spectroscopic scattering results strongly suggested that cyclic dimers of biselenite ions were incorporated into the gallery spaces of the LDHs, vertically arranged to the horizontal axes of the MgAl‐LDH layers.

No abstract