RESUMEN
Transparent and flexible gas-barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh-gas-barrier films with a brick-mortar-sand structure fabricated by layer-by-layer (LBL) assembly of XAl-layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO2 infilling, denoted as (XAl-LDH/PAA)n-CO2. The near-perfectly parallel orientation of the LDH "brick" creates a long diffusion length to hinder the transmission of gas molecules in the PAA "mortar". Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO2 acts like "sand" to fill the free volume at the organic-inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl-LDH/PAA)n-CO2 film is among the best gas barrier films ever reported.
Asunto(s)
Resinas Acrílicas/química , Dióxido de Carbono/química , Gases/química , Hidróxidos/química , Nanoestructuras/química , Adsorción , Cobalto/química , Difusión , Magnesio/química , Modelos Moleculares , Nanoestructuras/ultraestructura , Níquel/química , Zinc/químicaRESUMEN
A CoAl-layered double hydroxide (LDH)@poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanoplatelet array (NPA) is grown on a flexible Ni foil substrate as a high-performance pseudocapacitor. The LDH@PEDOT core/shell NPA shows a maximum specific capacitance of 649 F/g (based on the total mass) by cyclic voltammetry (scan rate: 2 mV/s) and 672 F/g by galvanostatic discharge (current density: 1 A/g). Furthermore, the hybrid NPA electrode also exhibits excellent rate capability with a specific energy of 39.4 Wh/kg at a current density of 40 A/g, as well as good long-term cycling stability (92.5% of its original capacitance is retained after 5000 cycles). These performances are superior to those of conventional supercapacitors and LDH NPA without the PEDOT coating. The largely enhanced pseudocapacitor behavior of the LDH@PEDOT NPA electrode is related to the synergistic effect of its individual components: the LDH nanoplatelet core provides abundant energy-storage capacity, while the highly conductive PEDOT shell and porous architecture facilitate the electron/mass transport in the redox reaction.
Asunto(s)
Compuestos Bicíclicos Heterocíclicos con Puentes/química , Nanopartículas/química , Nanotecnología/métodos , Polímeros/química , Aluminio/química , Cobalto/química , Análisis Costo-Beneficio , Difusión , Electroquímica/métodos , Electrodos , Electrones , Hidróxidos/química , Microscopía Electrónica de Rastreo/métodos , Modelos Químicos , Modelos Estadísticos , Níquel/química , Oxidación-Reducción , Óxidos/químicaRESUMEN
In this paper we report the fabrication of layered double hydroxide (LDH) nanoparticles/poly(N-isopropylacrylamide) (pNIPAM) ultrathin films (UTFs) via the layer-by-layer assembly technique, and their switchable electrocatalytic performance in response to temperature stimuli was demonstrated. X-ray diffraction and UV-vis absorption spectroscopy indicate a periodic layered structure with uniform and regular growth of the (LDH/pNIPAM)(n) UTFs; an interaction based on hydrogen bonding between LDH nanoparticles and pNIPAM was confirmed by X-ray-photoelectron spectroscopy and Fourier transform infrared spectroscopy. Temperature-triggered cyclic voltammetry and electrochemical impedance spectroscopy switch for the UTFs was obtained between 20 and 40 °C, accompanied by reversible changes in surface topography and film thickness revealed by atomic force microscopy and ellipsometry, respectively. The electrochemical on-off property of the temperature-controlled (LDH/pNIPAM)(n) UTFs originates from the contraction-expansion configuration of pNIPAM with low-high electrochemical impedance. In addition, a switchable electrocatalytic behavior of the (LDH/pNIPAM)(n) UTFs toward the oxidation of glucose was observed, resulting from the temperature-controlled charge transfer rate. Therefore, this work provides a facile approach for the design and fabrication of a well-ordered command interface with a temperature-sensitive property, which can be potentially applied in electrochemical sensors and switching.
Asunto(s)
Acrilamidas/química , Electroquímica/métodos , Hidróxidos/química , Polímeros/química , Temperatura , Resinas Acrílicas , Catálisis , Electrodos , Enlace de Hidrógeno , Modelos Moleculares , Conformación Molecular , Compuestos de Estaño/químicaRESUMEN
Inorganic nanoplatelet reinforced polymer films were fabricated via alternate layer-by-layer assembly of layered double hydroxide (LDH) nanoplatelets with poly(vinyl alcohol) (PVA), which showed largely enhanced strength and good ductility simultaneously.