Ho3+ carbon paste sensor based on multi-walled carbon nanotubes: Applied for determination of holmium content in biological and environmental samples

Synthetic ratiometric fluorescent probes for detection of ions

Metal cations and anions are essential for versatile physiological processes. Dysregulation of specific ion levels in living organisms is known to have an adverse effect on normal biological events. Owing to the pathophysiological significance of ions, sensitive and selective methods to detect these species in biological systems are in high demand. Because they can be used in methods for precise and quantitative analysis of ions, organic dye-based ratiometric fluorescent probes have been extensively explored in recent years. In this review, recent advances (2015-2019) made in the development and biological applications of synthetic ratiometric fluorescent probes are described. Particular emphasis is given to organic dye-based ratiometric fluorescent probes that are designed to detect biologically important and relevant ions in cells and living organisms. Also, the fundamental principles associated with the design of ratiometric fluorescent probes and perspectives about how to expand their biological applications are discussed.

A novel ratiometric fluorescent probe based on 1, 8-naphthalimide for the detection of Ho3+ and its bioimaging

A ratiometric fluorescent probe for the detection of Ho³⁺ in DMSO-aqueous medium was designed and synthesized based on 1, 8-naphthalimide. The probe displayed response to Ho³⁺ with a fluorescence decrease at 512nm and enhancement at 480nm, accompanying with a distinct fluorescence change from bright yellow-green to cyan. Besides, the probe exhibited a lower detection limit (6×10^-8M) and could be used in intracellular fluorescence imaging. To the best of the knowledge, it was the first ratiometric fluorescent probe for Ho³⁺ detection. This probe was expected to be a useful tool for further elucidating the roles of Ho³⁺ in materials, biology and environment.

A highly selective and sensitive turn-on fluorescent probe for the detection of holmium ion and its bioimaging

The phenolphthalein aldehyde was synthesized and used to a turn-on fluorescent probe for the detection of holmium ion (Ho³⁺) in HEPES : DMF = 1 : 1 (v/v pH = 7.4) solution with an excellent selectivity and sensitivity for Ho³⁺over other metal ions.

Silver ion imprinted polymer nanobeads based on a aza-thioether crown containing a 1,10-phenanthroline subunit for solid phase extraction and for voltammetric and potentiometric silver sensors

A new nano-sized silver(I) ion-imprinted polymer (IIP) was prepared via precipitation copolymerization using ethyleneglycol dimethacrylate, as a cross-linking agent in the presence of Ag(+) and an aza-thioether crown containing a 1,10-phenanthroline subunit as a highly selective complexing agent. The imprint silver(I) ion was removed from the polymeric matrix using a 1.0M HNO3 solution. The resulting powder material was characterized using IR spectroscopy and scanning electron microscopy. The SEM micrographs showed colloidal nanoparticles of about 52 nm and 75 nm in diameter and slightly irregular in shape for leached and unleached IIPs, respectively. The optimal pH for quantitative enrichment was 6.0 and maximum sorbent capacity of the prepared IIP for Ag(+) was 18.08 μmol g(-1). The relative standard deviation and limit of detection (LOD=3Sb/m) for flame atomic absorption spectrometric determination of silver(I) ion, after its selective extraction by the prepared IIP nanobeads, were evaluated as 2.42% and 2.2×10(-8) M, respectively. The new Ag(+)-IIP was also applied as a suitable sensing element to the preparation of highly selective and sensitive voltammetric and potentiometric sensors for ultra trace detection of silver(I) ion in water samples, with limits of detection of 9.0×10(-10) and 1.2×10(-9) M, respectively.