Advances in electrospun nanofibrous membrane sensors for ion detection

Harmful metal ions and toxic anions produced in industrial processes cause serious damage to the environment and human health. Chemical sensors are used as an efficient and convenient detection method for harmful ions. Electrospun fiber membranes are widely used in the field of solid-state chemical sensors due to high specific surface area, high porosity, and strong adsorption. This paper reviews the solid-state chemical sensors based on electrospinning technology for the detection of harmful heavy metal ions and toxic anions in water over the past decade. These electrospun fiber sensors have different preparation methods, sensing mechanisms, and sensing properties. The preparation method can be completed by physical doping, chemical modification, copolymerization, surface adsorption and self-assembly combined with electrospinning, and the material can also be combined with organic fluorescent molecules, biological matrix materials and precious metal materials. Sensing performance aspects can also be manifested as changes in color and fluorescence. By comparing the literature, we summarize the advantages and disadvantages of electrospinning technology in the field of ion sensing, and discuss the opportunities and challenges of electrospun fiber sensor research. We hope that this review can provide inspiration for the development of electrospun fiber sensors.

A stimuli responsive triplet-triplet annihilation upconversion system and its application as a ratiometric sensor for Fe3+ ions

A ratiometric fluorescent sensor for the detection of Fe3+ ions is achieved based on triplet-triplet annihilation upconversion (TTA-UC) luminescence. A new anthracene derivative (named as DHTPA) is designed and synthesized and reveals similar optical properties to 9,10-diphenylanthracene (DPA) and is used as a stimuli responsive annihilator in a TTA-UC system due to its complexation ability. As a result, the UC emission can be significantly quenched by Fe3+ ions, while the phosphorescence (PL) emission of sensitizer palladium(ii) octaetylporphyrin (PdOEP) remains nearly constant, which makes the PL signal an appropriate internal reference for the UC signal. The UC and ratio signals (I UC/I PL) both reveal a good linear relationship with Fe3+ ion concentration, which for the first time makes the TTA-UC system a perfect ratiometric sensor for Fe3+ ion detection. This sensing method will open a novel avenue to achieve ratiometric sensors in chemical and biological fields.

Terpyridine-based complex nanofibers with Eu3+ as a highly selective chemical probes for UO22

Uranyl is a radioactive, toxic pollutant commonly found in the waste remaining after nuclear fuel reprocessing, and it poses several types of risks to human health; therefore, developing absorbents and chemical probes for this compound is crucial to overcoming these issues. This study examined the sensing abilities of terpyridine-appended benzenetricarboxyamide (T-BTA) as a chromogenic probe for detecting uranyl ions (UO₂²⁺). The complex with Eu³⁺ (1-Eu) spontaneously formed nanostructured fibers in H₂O owing to the triamide groups of T-BTA, which induced intermolecular hydrogen-bonding interactions. The strong blue emission of these nanofibers in H₂O was quenched upon adding UO₂²⁺ but not upon adding any other metal ion. This high selectivity was probably because of the interactions between the nitrigen atoms of the terpyridine moieties of 1 and UO₂²⁺. Furthermore, the 1-Eu nanofibers assumed spherical morphologies when UO₂²⁺ was added. To develop a convenient UO₂²⁺ sensor, an electrospun film incorporating 1-Eu (ESF-1-Eu) was manufactured, and it exhibited high selectivity for UO₂²⁺ over a variety of rival metal ions. The plot for luminescence change of ESF-1-Eu vs UO₂²⁺ concentrations in seawater samples showed a good linearty. Thus, the ESF-1-Eu shows potential as a useful sensor for detecting and removing UO₂²⁺ in H₂O.

Dual-binding pyridine and rhodamine B conjugate derivatives as fluorescent chemosensors for ferric ions in aqueous media and living cells

Two new pyridine-type rhodamine B chemosensors (RBPO and RBPF) used to detect Fe3+ have been designed and synthesized, and the sensing behavior towards various metal ions was evaluated via UV-vis and fluorescence spectroscopic techniques. Both RBPO and RBPF not only have good spectral responses to Fe3+ in an EtOH/H2O solution (3 : 1, v/v, HEPES, 0.5 mM, pH = 7.33) with low detection limits and high binding constants, but also suffer from less interference from common metal cations. The two chemosensors are further proven to be practical in sensitively monitoring trace Fe3+ in real water specimens. Intracellular imaging applications demonstrated that RBPO and RBPF can be used as two fluorescent chemosensors for the detection of Fe3+ in living human breast adenocarcinoma (MCF-7) cells.

Lysosomal tracking with a cationic naphthalimide using multiphoton fluorescence lifetime imaging microscopy

A naphthalimide-based chemosensing motif capable of turning on the fluorescence emission in solution and in vitro is reported.