Macroporous perovskite nanocrystal composites for ultrasensitive copper ion detection

Accumulation of heavy metal ions, including copper ions (Cu²⁺), presents a serious threat to human health and to the environment. A substantial amount of research has focused on detecting such species in aqueous solutions. However, progress towards ultrasensitive and easy-to-use sensors for non-aqueous solutions is still limited. Here, we focus on the detection of copper species in hexane, realising ultra-sensitive detection through a fluorescence-based approach. To achieve this, a novel macroporous composite material has been developed featuring luminescent CsPbBr₃ nanocrystals (NCs) chemically adhered to a polymerized high internal phase emulsion (polyHIPE) substrate through surface thiol groups. Due to this thiol functionality, sub-monolayer NC formation is realised, which also renders outstanding stability of the composite in the ambient environment. Copper detection is achieved through a direct solution based immersion of the CsPbBr₃-(SH)polyHIPE composite, which results in concentration-dependent quenching of the NC photoluminescence. This newly developed sensor has a limit of detection (LOD) for copper as low as 1 × 10^-16 M, and a wide operating window spanning 10^-2 to 10^-16 M. Moreover, the composite exhibits excellent selectivity among different transition metals.

Methyl viologen induced fluorescence quenching of CdTe quantum dots for highly sensitive and selective "off-on" sensing of ascorbic acid through redox reaction

A turn-on fluorescent sensor based on CdTe quantum dots (QDs) is designed for highly sensitive and selective ascorbic acid (AA) detection. CdTe shows a strong emission centered at 578 nm. When assembled with poly(sodium 4-styrenesulfonate) (PSS) and methyl viologen (Mv²⁺) through electrostatic interaction, the emission is found to be effectively quenched. In the presence of AA, Mv²⁺ is reduced to Mv⁺, making the fluorescence of CdTe QDs restored. Under the optimal conditions, the proposed AA sensing method shows a linear proportional response from 0.8 µM to 20 µM, with the detecting limit as low as 50 nM. The developed method was successfully applied in the analysis of AA in human serum samples and cell lysates with satisfactory results.