pH-Controlled Gold Nanoclusters with Tunable Fluorescence Prepared via Reduction with Ascorbic Acid in the Presence of Adenosine-5′-monophosphate

Preparation of gold nanoclusters via reduction of HAuCl4 with ascorbic acid in the presence of adenosine-5′-monophosphate has been investigated. It has been demonstrated that the reduction in a weakly acidic medium results in gold nanoclusters exhibiting blue fluorescence, whereas the reduction in neutral or weakly alkaline medium affords a mixture of blue- and red-emitting gold nanoclusters. The yield of the nanoclusters and the ratio between the blue and red emitters is determined by the process duration, on top of the reaction mixture acidity. A possible mechanism leading to the formation of red-emitting gold nanoclusters has been suggested. The blue-emitting clusters has exhibited reversible sensitivity to the solution pH, much stronger than in the case of the red-emitting nanoclusters.