Ag2Te quantum dots with compact surface coatings of multivalent polymers: Ambient one-pot aqueous synthesis and the second near-infrared bioimaging

In this study, we described a facile ambient one-pot aqueous synthesis of fluorescent Ag2Te quantum dots (QDs) adopting multivalent polymers (poly(maleic anhydride) homopolymers) as stabilizers. In experiments, Ag2Te QDs were synthesized via a stepwise addition of the stabilizers, precursors (AgNO3/Na2TeO3) and promoters (NaBH4/N2H4·H2O) in ambient one-pot aqueous solution. By regulating the compositions of raw materials, water-dispersed Ag2Te QDs (3.8–4.7 nm) were achieved and exhibited tunable photoluminescence (PL) emission (995–1068 nm) in the second near-infrared (NIR-II) region, accompanying with the minimized surface coating thickness (1.5–1.9 nm). Such compact coating of multivalent polymers promoted PL emission of Ag2Te QDs, so showing high PL quantum yields (PLQYs: 13.1–15.2%). In addition to compact sizes and high PLQYs, experimental results testified that the Ag2Te QDs demonstrated high photo-/colloidal stability and ultralow cytotoxicity, which implied their promising applications, especially serving as an effective nanoprobe for bioimaging in the NIR-II biological window.