Quadruple analyte responsive platform: Point-of-care testing and multi-coding logic computation based on metal ions...

Area of Science:

• Nanomaterials for chemical sensing
• Point-of-care diagnostics
• Environmental monitoring technologies

Background:

• Traditional heavy metal ion monitoring lacks on-site, user-friendly, and cost-effective solutions, especially in resource-limited settings.
• Existing laboratory instrumentation is not suitable for convenient, quantitative sensing platforms required for point-of-care testing (POCT).

Purpose of the Study:

• To develop an affordable and user-friendly colorimetric POCT sensing system for selective monitoring of four key metal ions: iron (Fe3+), cobalt (Co2+), lead (Pb2+), and cadmium (Cd2+).
• To demonstrate the system's capability for quantitative analysis using digital colorimetric readings from smartphone images.
• To engineer the platform for advanced molecular computation through integrated logic operations.

Main Methods:

• Utilized sulfur quantum dots (S dots) as the core sensing material, reacting selectively with target metal ions.
• Developed paper-based analytical devices (PADs) displaying distinct visual color changes (green, brown, precipitation, bright yellow) for each metal ion.
• Employed smartphone imaging and a dedicated app to convert visual signals into HSV values for quantitative analysis.
• Integrated multi-responsive blocks into S dots to enable multiple logic operations (YES, NOT, AND, INHIBIT, NOR).

Main Results:

• Achieved selective detection of Fe3+, Co2+, Pb2+, and Cd2+ with distinct visual signals on PADs.
• Established quantitative analysis with low limits of detection: 0.59 μM (Fe3+), 0.47 μM (Co2+), 0.82 μM (Cd2+), and 0.53 μM (Pb2+).
• Demonstrated the platform's capacity for sophisticated molecular computation through engineered logic operations.

Conclusions:

• The proposed colorimetric POCT system offers a practical, affordable, and user-friendly approach for on-site heavy metal ion monitoring.
• The integration of digital colorimetric analysis via smartphones enhances quantitative capabilities for resource-constrained environments.
• The platform's ability to perform logic operations signifies its potential for advanced environmental testing and molecular computation.