Progress in pre-treatment and extraction of organic and inorganic pollutants by layered double hydroxide for trace-level analysis

Continuous release of pollutants into the environment poses serious threats to environmental sustainability and human health. For trace-level analysis of pollutants, layered double hydroxide (LDH) is an attractive option to impart enhanced sorption capability and sensitivity toward pollutants because of its unique layered structure, tunable interior architecture, high anion-exchange capacities, and high porosity (e.g., Zn/Cr LDH/DABCO-IL, Ni/Al LDH, CS-Ni/Fe LDH, SDS-Fe₃O₄@SiO₂@Mg-Al LDH, Boeh/Mg/Al LDH/pC, and Fe@NiAl LDH). In concert with the well-defined analytical methodologies (e.g., HPLC and GC), the LDH materials can be employed to detect trace-level targets (e.g., as low as ∼ 20 fg/L for phenols) in aqueous environments. This review highlights LDH as a promising material for pre-treatment of a variety of organic and inorganic target pollutants in complex real matrices. Challenges and future requirements for research into LDH-based analytical methods are also discussed.

A review on optical sensors based on layered double hydroxides nanoplatforms

In recent years, significant efforts have been devoted towards the fabrication and application of layered double hydroxides (LDHs) due to their tremendous features such as excellent biocompatibility with negligible toxicity, large surface area, high conductivity, excellent solubility, and ion exchange properties. Most impressive, LDHs offer a favorable environment to attach several substances such as quantum dots, fluorescein dyes, proteins, and enzymes, which leads to strengthening the catalytic properties or increasing the sensing selectivity and sensitivity of the resulted hybrids. With the extensive ongoing research on the application of nanomaterials, many studies have led to remarkable achievements in exploring LDHs as sensing nanoplatforms. In optical sensors, for instance, many sensing strategies were tailored based on the enzyme-mimicking properties of LDHs, including colorimetric and chemiluminescence procedures. Meanwhile, others were designed based on intercalating some fluorogenic substrates on the LDHs, whereby the sensing signal can be acquired by quenching or enhancing their fluorescence after the addition of analytes. In this review, we aim to summarize the recent advances in optical sensors that use layered double hydroxides as sensing platforms for the determination of various analytes. By outlining some representative examples, we accentuate the change of spectral absorbance, chemiluminescence, and photoluminescence phenomena triggered by the interaction of LDH or functionalized-LDH with the indicators and analytes in the system. And finally, current limitations and possible future orientation in designing further LDHs-based optical sensors are presented. It is hoped that this review will be helpful in assisting the establishment of more improved sensors based on LDHs features. Optical sensors based on layered double hydroxides (LDHs) nanoplatforms were reviewed. The sensing system and detection approaches were rationally reviewed. Possible future orientations were highlighted.

Recent Materials Developed for Dispersive Solid Phase Extraction

Solid phase extraction (SPE) is an analytical procedure developed with the purpose of separating a target analyte from a complex sample matrix prior to quantitative or qualitative determination. The purpose of such treatment is twofold: elimination of matrix constituents that could interfere with the detection process or even damage analytical equipment as well as enriching the analyte in the sample so that it is readily available for detection. Dispersive solid phase extraction (dSPE) is a recent development of the standard SPE technique that is attracting growing attention due to its remarkable simplicity, short extraction time and low requirement for solvent expenditure, accompanied by high effectiveness and wide applicability. This review aims to thoroughly survey recently conducted analytical studies focusing on methods utilizing novel, interesting nanomaterials as dSPE sorbents, as well as known materials that have been only recently successfully applied in dSPE techniques, and evaluate their performance and suitability based on comparison with previously reported analytical procedures.

A dispersive solid phase extraction-based method for chromium(vi) analysis using a Zn–Al layered double hydroxide intercalated with l-aspartic acid as a dissolvable adsorbent

An analytical method for extraction and preconcentration of Cr(vi) in water with DSPE using a Zn–Al LDH intercalated with l-aspartic acid as a dissolvable adsorbent.

Recent advances in the application of layered double hydroxides in analytical chemistry: A review

In recent years, layered double hydroxides (LDHs) have garnered a lot of attention in analytical chemistry, due to their advantages such as relatively simple synthesis, low cost, possession of large specific surface area and high catalytic activity, and biocompatibility. The most common applications of LDH in analytical chemistry such as sorbents in sample extraction, electrode materials in electrochemical sensing and color indicators in colorimetric detection have been well reported. Generally, the LDHs are prepared as composites with nanomaterials, or constructed with specific three-dimensional structures, befitting the applications desired for them. However, the applications of LDHs (as extraction sorbents, color indicators and in electrochemical sensing) are usually limited in these scenarios. To help address these challenges, future trends and developmental prospects of LDHs materials in analytical chemistry are discussed in this article. Besides, the strategies associated with the design of LDHs, including the structural aspects, for potential analytical applications are presented and reviewed.