Preparation of LaB ₆ nanoparticles as a novel and effective near-infrared photothermal conversion material

LaB ₆ nanoparticles have been prepared successfully by a stirred bead milling process. The anionic surfactant dodecylbenzenesulfonic acid was found to be suitable for the grinding and dispersion of LaB ₆ powders, but cationic surfactant polyethyleneimine and nonionic surfactant polyethylene glycol could not yield a stable dispersion. Three kinds of grinding beads with the diameters of 50, 100, and 200μm all could reduce the mean hydrodynamic diameter of LaB ₆ powders to about 100nm. However, although the grinding rate was slower, using the smaller grinding beads with a diameter of 50μm could yield a dispersion of LaB ₆ nanoparticles with more uniform size. The resulting LaB ₆ nanoparticles were confirmed to remain a cubic structure and the contaminant from ZrO ₂ beads was below 5wt%. Furthermore, the LaB ₆ nanoparticles exhibited a characteristic absorption around 1000nm and possessed an excellent near infrared (NIR) photothermal conversion property better than Au nanoshells. Because they were relatively cheap and easy-to-preparation than Au nanorods or nanoshells, the LaB ₆ nanoparticles could be used as a novel and effective NIR photothermal conversion material and might find great potential in the biomedical application.