Separation and indirect ultraviolet detection of ferrous and trivalent iron ions by using ionic liquids in ion chromatography

Colorimetric and visual sensing of ferrous ion by Fenton reaction-stimulated etching of triangular gold nanoplates

In this study, a method for ultrasensitive sensing of Fe²⁺ based on Fenton reaction mediated etching of triangular gold nanoplates (Au NPLs) was developed. In this assay, the etching of Au NPLs by H₂O₂ was accelerated in the presence of Fe²⁺ due to the generation of superoxide free radical (O₂^·-) via Fenton reaction. With the concentration of Fe²⁺ increased, the shape of Au NPLs changed from triangular to sphere with the blue shifted localized surface plasmon resonance, accompanying a series of consecutive color changes from blue, bluish purple, purple, reddish purple and finally to pink. The rich color variations enable rapid visual quantitative determination of Fe²⁺ within 10 min. A good linear relationship between the peak shifts and the concentration of Fe²⁺ was obtained in the range of 0.035 to 1.5 μM (R² = 0.996). Favorable sensitivity and selectivity in the presence of other tested metal ions were achieved in the proposed colorimetric assay. The detection limits (3ơ/k) for Fe²⁺ was 26 nM by UV-vis spectroscopy, and the clearly discernible concentration of Fe²⁺ was as low as 0.07 μM by naked eyes. The recoveries of fortified samples in pond water and serum samples ranged from 96% to 106% with interday relative standard deviations <3.6% in all cases, demonstrating the applicability of the assay for measuring Fe²⁺ in real samples.

Luminescent Guests Encapsulated in Metal-Organic Frameworks for Portable Fluorescence Sensor and Visual Detection Applications: A Review

Metal-organic frameworks (MOFs) have excellent applicability in several fields and have significant structural advantages, due to their open pore structure, high porosity, large specific surface area, and easily modifiable and functionalized porous surface. In addition, a variety of luminescent guest (LG) species can be encapsulated in the pores of MOFs, giving MOFs a broader luminescent capability. The applications of a variety of LG@MOF sensors, constructed by doping MOFs with LGs such as lanthanide ions, carbon quantum dots, luminescent complexes, organic dyes, and metal nanoclusters, for fluorescence detection of various target analyses such as ions, biomarkers, pesticides, and preservatives are systematically introduced in this review. The development of these sensors for portable visual fluorescence sensing applications is then covered. Finally, the challenges that these sectors currently face, as well as the potential for future growth, are briefly discussed.

Preparative purification of corilagin from Phyllanthus by combining ionic liquid extraction, prep-HPLC, and precipitation

In this study, a green extraction and purification process for the rapid preparation of corilagin from Phyllanthus has been designed using an aqueous ionic liquid coupled with preparative high-performance liquid chromatography (prep-HPLC) and precipitation. The results showed that the optimum extraction process for corilagin involved mixing Phyllanthus tenellus Roxb. with 0.4 M [BMIm]Br at a liquid-solid ratio of 10 : 1 and dispersing the mixture by ultrasonication at 50 °C for 15 min. Macroporous resin D101 and prep-HPLC were employed for [BMIm]Br removal and corilagin separation to yield corilagin of 86.49% purity. Subsequently, corilagin was further purified by water precipitation to achieve 99.12% purity. The results indicated the successful development of a new rapid and green process to prepare corilagin on a large scale from plants using [BMIm]Br. This promising process can be applied for the preparative separation and purification of other active compounds from complex plant systems.