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 demonstrated 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 used a polyethyleneglycol (PEG) 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 to the Ag2S QDs coated by PEG without alkyl chain modification (Ag2S-PEG). In addition, the PEG skeleton ensures the stealth effect from macrophages resident in tissue and filtration organs (MPS system) and decent biocompatibility of the probe. Ultimately, the Ag2S-C11-PEG QDs have been demonstrated their 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.