Fluorescence sensitization of gold-glutathione nanoclusters by aqueous solutions of sodium and potassium ions

Microencapsulated Photoluminescent Gold for ppb-Level Chromium(VI) Sensing

Luminescent gold nanoclusters (Au NCs) are a promising probe material for selective chemical sensing. However, low luminescent intensity and an incomplete understanding of the mechanistic origin of the luminescence limit their practical implementation. We induced glutathione-capped Au NCs to aggregate within silica-coated microcapsular structures using polymer-salt aggregate self-assembly chemistry. The encapsulated NCs have a 5× luminescence enhancement compared to free Au NCs and can detect Cr(VI) at concentrations as low as 6 ppb (=0.12 μM CrO₄^2-) through luminescence quenching, compared to free Au NCs, which have a limit of detection (LOD) of 52 ppb (=1 μM CrO₄^2-). The LOD is 16× lower than the United States Environmental Protection Agency maximum contaminant level for total chromium (Cr(III) + Cr(VI), 100 ppb) in drinking water. No pH adjustment is needed using the encapsulated Au NCs, unlike the case for free Au NCs. The luminescent microcapsule material can sense Cr(VI) in simulated drinking water with a ∼20-30 ppb LOD, serving as a possible basis for a practical Cr(VI) sensor.

Selective and colorimetric detection of Ba2+ ions in aqueous solutions using 11-mercaptoundecylphosphonic acid functionalized gold nanoparticles

In this paper we describe a simple colorimetric method for the sensitive and selective detection of Ba²⁺ ions, using 11-mercaptoundecylphosphonic acid functionalized gold nanoparticles (AuNPs–MPA) in aqueous solution.