Abstract
Layered double hydroxides (LDHs) have attracted considerable attention as promising materials for electrochemical and optical sensors owing to their excellent catalytic properties, facile synthesis strategies, highly tunable morphology, and versatile hosting ability. LDH-based electrochemical sensors are affordable alternatives to traditional precious-metal-based sensors, as LDHs can be synthesized from abundant inorganic precursors. LDH-modified probes can directly catalyze or host catalytic compounds that facilitate analyte redox reactions, detected as changes in the probe’s current, voltage, or resistance. The porous and lamellar structure of LDHs allows rapid analyte diffusion and abundant active sites for enhanced sensor sensitivity. LDHs can be composed of conductive materials such as reduced graphene oxide (rGO) or metal nanoparticles for improved catalytic activity and analyte selectivity. As optical sensors, LDHs provide a spacious, stable structure for synergistic guest–host interactions. LDHs can immobilize fluorophores, chemiluminescence reactants, and other spectroscopically active materials to reduce the aggregation and dissolution of the embedded sensor molecules, yielding enhanced optical responses and increased probe reusability. This review discusses standard LDH synthesis methods and overviews the different electrochemical and optical analysis techniques. Furthermore, the designs and modifications of exemplary LDHs and LDH composite materials are analyzed, focusing on the analytical performance of LDH-based sensors for key biomarkers and pollutants, including glucose, dopamine (DA), H2O2, metal ions, nitrogen-based toxins, and other organic compounds.
Highlights
Affordable, accurate, and rapid sensing technology is essential for monitoring the environment, controlling water quality, and diagnosing medical conditions
High-resolution transmission electron microscopy (TEM) (HRTEM) determined a lattice spacing of 0.231 nm for the NiFe-Layered double hydroxides (LDHs), which are characteristic of NiFe–CO3-intercalated LDHs, but found a larger 0.260 nm spacing for the NiFe–Sodium dodecyl sulfate (SDS)-LDHs
Fewer ion exchange steps are recommended for higher yields
Summary
Affordable, accurate, and rapid sensing technology is essential for monitoring the environment, controlling water quality, and diagnosing medical conditions. LDH-based sensors have shown impressive analytical performances for electrochemical and optical detection methods because of their outstanding catalytic and hosting abilities. Ni2Co-LDHs with a thickness of 4–6 nm (5–8 layers) prepared by a simple exfoliation method in a low boiling point solvent with carbonate ion (CO32−) intercalants showed excellent sensing properties towards dopamine (DA) due to its low oxidation potential [41]. The surface area of the electrode’s LDH layer increased, likely due to the intercalation of the long-chain PANI This resulted in improved contact between the analyte and active materials. The NiCo-LDHs grown on CCCH showed better efficiency in sensing glucose due to the higher conductivity of copper foam and the higher surface area of active material. LDHs are promising 2D materials that have yet to be fully understood and optimized for sensor applications
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