A facile synthesis of thermo-responsive copolymer stabilized fluorescent silver nanoclusters and their application in pH sensing

Luminescent silver nanoclusters (NCs) decorated with temperature-responsive copolymer P(NIPAm-co-MQ) have been fabricated in aqueous solution as a new fluorescent pH stimuli-responsive functional materials. P(NIPAm-co-MQ) was prepared by a conventional free-radical copolymerization of isopropylacrylamide (NIPAm) as thermo-responsive units and 5-(2-methacryloylethyloxymethyl)-8-quinolinol (MQ) as coordinating groups. The obtained fluorescent Ag NCs with various sizes showed different morphologies from single sphere to chain structure induced by the copolymer ligand. Upon changing the temperature, the fluorescence intensity of the Ag NCs exhibited temperature triggered response simultaneously. The copolymer stabilized Ag NCs as a pH probe exhibited reversible pH-dependent PL properties over the pH range of 3.04–5.25. With the pH decreased, the fluorescence intensity of Ag NCs under a UV lamp decreased and it was almost completely quenched after pH 3.04. Also, the properties of this fluorescence change with pH are reversible.