A Highly Sensitive and Selective Colorimetric Hg²⁺ Ion Probe Using Gold Nanoparticles Functionalized with...

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Environmental Science

Background:

• Mercury ions (Hg2+) pose significant environmental and health risks.
• Developing sensitive and selective detection methods for Hg2+ is crucial for monitoring and safety.
• Gold nanoparticles (AuNPs) offer unique optical properties suitable for developing colorimetric sensors.

Purpose of the Study:

• To develop a highly sensitive and selective colorimetric assay for the detection of Hg2+ ions.
• To utilize gold nanoparticles (AuNPs) conjugated with polyethyleneimine (PEI) as a probe for Hg2+ detection.
• To establish a facile method for Hg2+ determination in various real-world samples.

Main Methods:

• Conjugation of gold nanoparticles (AuNPs) with polyethyleneimine (PEI) to create a sensing probe.
• Induction of AuNP aggregation upon coordination of Hg2+ ions with PEI, leading to a color change.
• Characterization of Hg2+-PEI binding using time-of-flight secondary ion mass spectrometry (ToF-SIMS).
• Optimization of assay conditions including pH, temperature, and salt concentration.
• Spectrophotometric analysis to correlate absorption intensity ratio with Hg2+ concentration.

Main Results:

• The PEI-AuNP probe exhibited a significant color change from light red to violet upon Hg2+ binding, indicative of aggregation.
• Time-of-flight secondary ion mass spectrometry confirmed bidentate coordination (N-Hg2+-N) of Hg2+ to PEI.
• The assay showed a linear correlation between the absorption intensity ratio (A700/A514) and Hg2+ concentration in the range of 0.003–5.0 μM.
• Optimized conditions (pH 7.0, 50°C, 300 mM NaCl) enhanced the assay's performance.
• Low limits of detection (1.72–2.00 nM) were achieved for various sample matrices, including tap water, pond water, tuna fish, and bovine serum.

Conclusions:

• A facile, sensitive, and selective colorimetric assay for Hg2+ detection was successfully developed using PEI-functionalized AuNPs.
• The assay is suitable for naked-eye and spectrophotometric determination of Hg2+.
• The method demonstrates potential for practical application in the analysis of Hg2+ in environmental and biological samples.