Colloidal PbS quantum dot-AlPO4 nanoporous glass composites: Controllable emission and nonlinear absorption

In recent years, near-infrared (NIR) materials beyond the visible region (700-2500 nm) has emerged as a promising research field with applications toward telecommunications, photovoltaic, in-vivo imaging, etc. Such technologies will benefit greatly from the advantageous properties of NIR materials including broadband tunable emission, nonlinear optical properties, photostability, and simple chemical processing. Here, we report a facile approach to fabricate high stable and controllable luminescent NIR-emitting composites by confining PbS colloidal quantum dots (CQDs) in sol-gel nanoporous AlPO4 glasses. The transmission electron microscopy images combined with X-ray photoelectron spectra in different depth of PbS-AlPO4 composites (PACs) reveal the successful solidification of CQDs in nanoporous structure of glasses. The controllable luminescence of PACs is dependent on the size of PbS CQDs in solution and glass pore size. We show that the broadband (270 nm) and bimodal emission of PACs are tailored by designing different composited strategies on the incorporation of colloidal quantum dots in AlPO4 nanoporous glasses. Ultrafast nonlinear optical properties of PACs were investigated using an open-aperture Z-scan technique with 515 nm 340 fs pulses. The PACs exhibited obvious reverse saturable absorption in our experiments, with a nonlinear absorption coefficient of 7.17 × 10−2 cm/GW. Furthermore, the stability of PACs is investigated by emission spectra from a few days to 180 days. The results imply PACs has a better stability than other regular PbS-solid materials such as PbS-Al2O3 films and close-packed PbS-filter paper systems.