Highly Electrochemiluminescent Cs4PbBr6@CsPbBr3 Perovskite Nanoacanthospheres and Their Application for Sensing Bisphenol A

Perovskite quantum dots (PQDs) as recently emerging electrochemiluminescence (ECL) luminophores have been paid much attention due to their good ECL activity, narrow ECL spectra, and easy preparation. However, the PQDs used for ECL sensing were mainly inherited from those PQDs prepared as strong fluorescence (FL) luminophores, which would limit the finding of highly ECL PQDs for sensing due to the very different mechanisms in generating excited-state luminophores between ECL and FL. In order to obtain highly electrochemiluminescent PQDs, for the first time we proposed to synthesize PQDs for ECL sensing rather than for FL-based analysis by optimizing the synthesis conditions. It was revealed that the volume of the precursor solution, the concentrations of CsBr and PbBr₂, the amount of capping reagents, and the synthesis reaction temperature all significantly affect the ECL activity of PQDs. On the basis of the optimization of the synthesis conditions, we obtained a new type of PQDs with high ECL activity. The new PQDs were characterized by several technologies, such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy dispersive X-ray spectrum, to be the hybrids of 3D PQDs (CsPbBr₃) and 0D PQDs (Cs₄PbBr₆) with unique morphologies, i.e., Cs₄PbBr₆@CsPbBr₃ PQD nanoacanthospheres (PNAs), in which Cs₄PbBr₆ was as the core and CsPbBr₃ served as the shell. The obtained Cs₄PbBr₆@CsPbBr₃ PNAs had much higher (>4 times) ECL activity than the prevailing 3D (CsPbBr₃) PQDs. Finally, the novel Cs₄PbBr₆@CsPbBr₃ PNAs have been applied for the ECL sensing of bisphenol A (BPA), showing a promising application of the highly electrochemiluminescent PQDs in analytical chemistry.

Metal-Organic Framework-Assisted Construction of TiO2/Co3O4 Highly Ordered Necklace-like Heterostructures for Enhanced Ethanol Vapor Sensing Performance

In this work, we report a metal-organic framework (MOF)-assisted strategy to synthesize necklace-like TiO₂/Co₃O₄ nanofibers with highly ordered heterostructures via a facile approach including electrospinning and subsequent calcination. Polycrystalline TiO₂ nanofibers and Co₃O₄ nanocages are consummately interconnected to form a highly ordered heterogeneous nanostructure, which can be of benefit for precisely accommodating the interface resistance of the p-n heterojunctions and the future realization of improved material performance. The ethanol-gas-sensing investigation showed that TiO₂/Co₃O₄ nanofiber sensors exhibited a strong ethanol response ( R_air/ R_gas -1 = 16.7 @ 150 ppm) and a low operating temperature of 150 °C. The sensing enhancement mechanism of the TiO₂/Co₃O₄ nanofibers is related to the formation of heterojunctions at interfaces and the high catalytic activity of MOF-derived Co₃O₄. Furthermore, this versatile method is a promising approach to constructing ordered heterostructures and extending the MOF-based heterogeneous materials toward wide applications.

Redox Recycling Amplification Using an Interdigitated Microelectrode Array for Ionic Liquid-Based Oxygen Sensors

A new design for a membrane-free gas sensor modified with a thin layer of ionic liquid is described. The new approach uses miniaturized interdigitated microelectrodes for detecting gases having reversible electrochemistry, for example, dioxygen. Analyte molecules are reduced on the first working electrode, creating an intermediate species (e.g., superoxide, O₂^•-, from dioxygen) that can be reoxidized back to the original molecule at the second working electrode. The loop of redox reactions enhances the measured current, leading to high sensitivity (3.29 ± 0.06 nA cm^-2 ppm^-1) and low detection limit (LOD = 174 ppm). The gas sensor design was demonstrated to monitor typical concentrations of oxygen with good accuracy and precision. The enhancement in the current is characteristic only of gas molecules with reversible electrochemistry, which indicates that the proposed gas sensor can analyze these molecules with greater sensitivity over those with irreversible electrochemistry.

One-Step Synthesis of Co-Doped In2O3 Nanorods for High Response of Formaldehyde Sensor at Low Temperature

Uniform and monodisperse Co-doped In₂O₃ nanorods were fabricated by a facile and environmentally friendly hydrothermal strategy that combined the subsequent annealing process, and their morphology, structure, and formaldehyde (HCHO) gas sensing performance were investigated systematically. Both pure and Co-doped In₂O₃ nanorods had a high specific surface area, which could offer abundant reaction sites to gas molecular diffusion and improve the response of the gas sensor. Results revealed that the In₂O₃/1%Co nanorods exhibited a higher response of 23.2 for 10 ppm of HCHO than that of the pure In₂O₃ nanorods by 4.5 times at 130 °C. More importantly, the In₂O₃/1%Co nanorods also presented outstanding selectivity and long-term stability. The superior gas sensing properties were mainly attributed to the incorporation of Co, which suggested the important role of the amount of oxygen vacancies and adsorbed oxygen in enhancing HCHO sensing performance of In₂O₃ sensors.

Detection of gaseous amines with a fluorescent film based on a perylene bisimide-functionalized copolymer

A fluorescent copolymer containing PBI units and hydroxyl-ethyl structures was developed for the fast and sensitive detection of gaseous amines

Ammonia capture from the gas phase by encapsulated ionic liquids (ENILs)

Encapsulated ionic liquids (ENILs) based on carbonaceous submicrocapsules were designed, synthesized and applied to the sorption of NH₃ from gas streams.

Label-free and highly sensitive electrochemiluminescence biosensing using quantum dots/carbon nanotubes in ionic liquid

A universal and label-free electrochemiluminescence biosensing platform with high sensitivity was developed based on quantum dots/carbon nanotubes in ionic liquid.