A colorimetric assay for measuring iodide using Au@Ag core-shell nanoparticles coupled with Cu(2+)

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Materials Science

Background:

• Metallic core-shell nanoparticles exhibit optical properties sensitive to their composition and structure.
• Iodide ions are important analytes in various environmental and biological samples.
• Developing rapid and selective detection methods for iodide is crucial.

Purpose of the Study:

• To develop a novel colorimetric sensing platform for iodide ions (I(-)) using Au@Ag core-shell nanoparticles (NPs) and copper ions (Cu(2+)).
• To investigate the mechanism of color change upon iodide detection.
• To evaluate the performance and portability of the developed sensing system.

Main Methods:

• Synthesis of Au@Ag core-shell nanoparticles.
• Coupling of Au@Ag NPs with copper ions (Cu(2+)) to form a sensing system.
• Colorimetric detection of iodide ions based on the oxidation of iodide and subsequent formation of silver iodide (AgI).
• Development of portable test strips by embedding the sensing system in agarose gels.

Main Results:

• The assay demonstrated a distinct color change from yellow to purple upon addition of iodide, attributed to the formation of Au@AgI core-shell NPs.
• A low detectable concentration of 0.5 μM iodide was achieved within a 10-minute reaction time.
• The sensing system exhibited excellent selectivity for iodide over other common anions.
• The agarose gel-based test strips were successfully applied for the semi-quantitation of iodide in dried kelp samples.

Conclusions:

• Au@Ag core-shell NPs coupled with Cu(2+) provide an effective platform for the colorimetric sensing of iodide ions.
• The developed assay is rapid, selective, and sensitive, with potential for field applications.
• The integration into portable test strips offers a cost-effective and convenient method for iodide detection in real-world samples.