Aqueous synthesis of human serum albumin-stabilized fluorescent Au/Ag core/shell nanocrystals for highly sensitive and selective sensing of copper(II).

Utilizing human serum albumin as a reducing plus stabilizing agent, fluorescent Au/Ag core/shell nanocrystals (NCs) were prepared in water at pH 9.0 and at physiological temperature (37 °C). The preparation of Au/Ag NCs did not involve any external reducing or stabilizing agents, and thus was eco-friendly. Moreover, the as-prepared Au/Ag NCs exhibited excellent photoluminescence (PL) properties that were utilized in the development of a PL sensor for the detection of Cu(2+). Experimental results showed that the PL of Au/Ag NCs was almost linearly quenched by each increment of Cu(2+) concentration in the range of 0-200 nM, and the corresponding linear equation had a good correlation coefficient of 0.9959. The limit of detection for this sensor method was calculated to be 5 nM. In the presence of Cu(2+), the PL quenching of Au/Ag NCs was highly selective and sensitive in comparison to other metal ions and anions determined under the same conditions. In addition, the detection mechanism of this PL sensor was investigated. To further evaluate the analytical performance of this sensor, the concentrations of Cu(2+) were determined in real samples, including tap water, river water, gastric juice, urine and mixed solutions.