Short-Wave Infrared Quantum Dots with Compact Sizes as Molecular Probes for Fluorescence Microscopy

Materials with short-wave infrared (SWIR) emission are promising contrast agents for in vivo animal imaging, providing high-contrast and high-resolution images of blood vessels in deep tissues. However, SWIR emitters have not been developed as molecular labels for microscopy applications in the biosciences, which require optimized probes that are bright, stable, and small. Here we design and synthesize semiconductor quantum dots (QDs) with SWIR emission based on HgxCd1-xSe alloy cores red-shifted to the SWIR by epitaxial deposition of thin HgxCd1-xS shells with low bandgap. By tuning alloy composition alone, the emission can be shifted across the visible-to-SWIR (VIR) spectra while maintaining a small and equal size, allowing direct comparisons of molecular labeling performance across broad wavelength ranges. After coating with click-functional multidentate polymers, the VIR-QD spectral series has high quantum yield in the SWIR (14-33%), compact size (<13 nm hydrodynamic diameter), and long-term stability...