Partial Exchange between Inorganic and Organic Anions in MgAl Layered Double Hydroxide Nanosheets for Humidity Sensing

Abstract

Layered double hydroxides (LDHs) are a class of layered materials that show intercalant-dependent properties. Precise control over the type and concentration of intercalants in LDHs is important to tailor their properties and functions. Herein, through an anion exchange process, we partially replaced the NO3 2– ions in MgAl-LDH nanosheets with terephthalic acid (BDC) ions and systematically studied their ionic conduction and humidity sensing properties at different NO3 2–/BDC ratios. Our results show that moderate BDC intercalation boosted the humid sensing response to 3 orders of magnitude compared to the original MgAl-LDH intercalated with NO3 2– ions. This is because the BDC molecules could help improve the hydrophilicity of the LDH and thus the ability to absorb water molecules. However, too high a BDC concentration resulted in a considerable reduction in the ionic conduction of the LDH because this might block ionic conductive paths. As a demonstration, the MgAl-LDH-NO3 2–-BDC hybrid was fabricated into a flexible humidity sensor, which showed potential as a wearable breath sensor.

Efficient Adsorption of Methylene Blue Using a Hierarchically Structured Metal–Organic Framework Derived from Layered Double Hydroxide

“…A discernible band at 3394 cm –1 indicated the presence of hydrogen-bonded O–H groups from LDH in the composite. Vibrations corresponding to the (C–O) bond in COO – and the (N–O) bond in NO 3 – are responsible for the peaks at 1558 and 1398 cm –1 , respectively . Moreover, the characteristic benzene ring (phenyl mode) of the H 2 BDC ligand possesses CC bond bands at 1558 cm –1 .…”

Heterointerface engineering of layered double hydroxide/MAPbBr3 heterostructures enabling tunable synapse behaviors in a two-terminal optoelectronic device

“…They are typical ionic conductors that transport OH À ions 24,25 supported by the polarized hydrogen-bond network on their surfaces under a wide range of humid conditions (e.g., from 11% RH to 97% RH). 26 We therefore proposed to combine LDH with MHPs to realize synaptic behaviors through the interfacial charge trapping effect under humidity modulation. In this contribution, we show that MAPbBr 3 nanocrystals could self-assemble on MgAl-LDH nanoplates epitaxially.…”

3D “House of Cards” Structured Composites of Zn/Ga Layered Double Hydroxide/Molybdenum Disulfide with Potential Application for Impedance Respiratory Frequency Sensor

“…. Due to the better ionic conductivity of LDH materials, functionalized or anion-exchange LDHs, such as CoAl-LDH-NO 3 – , ZnAl-LDH-CO 3 2– , and MgAl-LDH-NO 3 – -BDC, have recently been applied to humidity sensing. The layered hydrophilic structure of LDH nanoparticles allows more water molecules to penetrate into the material, improving its water absorption.…”

“…In this case, special attention has been paid to layered double hydroxides (LDHs) due to their layered structures, large specific surface area, and large number of hydrophilic ions (hydroxyl, carbonate, nitrate, etc.). 23 Due to the better ionic conductivity of LDH materials, functionalized or anionexchange LDHs, such as CoAl-LDH-NO 3 − , 24 ZnAl-LDH-CO 3 2− , 25 and MgAl-LDH-NO 3 − -BDC, 26 have recently been applied to humidity sensing. The layered hydrophilic structure of LDH nanoparticles allows more water molecules to penetrate into the material, improving its water absorption.…”