Rapid analysis of mercury ion in real samples via ion-imprinted nanoparticle-based test strips

Mercury ion (Hg²⁺) contamination poses severe threats to ecological systems and human health, necessitating the development of facile and rapid monitoring methodologies. Herein, a fluorescence sensing system integrating ion-imprinted polymer (IIP) nanoparticle (NP)-based test strips with a miniaturized fluorimeter was fabricated for rapid quantitative analysis of Hg²⁺ in complicated matrix samples. First, CdTe quantum dot (QD)-coated silica (CdTe@SiO₂) NPs and Hg²⁺-imprinted polymer-functionalized CdTe@SiO₂ (Hg-IIPs@CdTe@SiO₂) NPs were synthesized via an ion-imprinting strategy using Hg²⁺ as the template ion via ion-imprinting technology. Critical synthetic parameters, including the feed ratios of functional monomer, cross-linker, and catalyst, as well as the loading volume of QDs, were systematically optimized. Characterizations verified that the as-prepared Hg-IIPs@CdTe@SiO₂ NPs displayed regular spherical morphology, desirable component distribution, and favorable fluorescence performance. Further mechanistic investigation revealed that Hg²⁺ effectively quenched the intrinsic fluorescence of Hg-IIPs@CdTe@SiO₂ NPs via a combination of dynamic quenching and Förster resonance energy transfer (FRET). Benefiting from the good fluorescence properties of specific recognition of the system, the constructed sensing platform achieved high sensitivity with a limit of detection (LOD) of 9.1 ng/L, superior anti-interference selectivity, and satisfactory reproducibility and storage stability (relative standard deviation, RSD < 5%). Green Analytical Procedure Index (GAPI) assessment confirmed the eco-friendly feature of the proposed detection strategy. Finally, the developed sensing system was successfully applied for Hg²⁺ quantification in real samples, highlighting its promising application prospect for environmental supervision, food safety, and pharmaceutical inspection.