Revealing the energy transfer between NIR-II PEGylated quantum dots and water†

Abstract

Hydrophilic semiconductor quantum dots (QDs) with photoluminescence (PL) located in the second near-infrared window (NIR-II) have shown great promise for in vivo bioimaging applications. However, their performance can be affected by the strong water absorption in this spectral region, which results in severely reduced NIR-II PL intensity. Herein, we use a PEG polymer modified with a hydrophobic alkyl chain (–C₁₁H₂₂–) to decorate non-toxic NIR-II Ag₂S (Ag₂S–C₁₁–PEG) QDs. The incorporation of the alkyl chain minimizes the energy transfer process from QDs to water molecules. As a result, the Ag₂S–C₁₁–PEG QDs exhibit superior PL intensity with approximately three-fold enhancement compared to the Ag₂S QDs coated with PEG without modification (Ag₂S–PEG). Furthermore, the PEG tail in the QDs ensures the biocompatibility of the probe. Ultimately, the Ag₂S–C₁₁–PEG QDs have been demonstrated to have potential as high-performance probes for in vivo bioimaging, exhibiting excellent brightness and metabolizable ability. This work showcases a valid strategy for advancing NIR-II QDs in high-performance bioimaging applications.