Photoluminescent neodymium-doped ZnO nanocrystals prepared by laser ablation in solution for NIR-II fluorescence bioimaging

The work reports on the use of laser ablation and post-ablation irradiation techniques for the preparation Nd3+ doped ZnO nanoparticles (NPs). The focus has been made on photoluminescence of Nd-doped ZnO NPs in the second near infrared (NIR-II) spectral window (1000-1700 nm) of the biological transparency. Morphology, phase composition and optical properties of the synthesized NPs were studied by absorption and photoluminescence spectroscopy, X-Ray diffraction (XRD) and transmission (TEM) electron microscopy. Near-infrared luminescence of Nd3+ doped ZnO nanocrystals in the region of 1000-1400 nm was detected both upon excitation from the ground state (800 nm) and upon UV excitation. The latter proves the incorporation of the Nd3+ into ZnO lattice as photoluminescence occurs through the transfer of excitation energy from the ZnO matrix to the Nd3+ ion. The possibility of control over the luminescence properties by a variation of solvent composition and by additional laser irradiation was demonstrated.