From spherical to bone-shaped gold nanoparticles—Time factor in the formation of Au NPs, their optical and photothermal properties

Using the same synthesis method, which was stopped at different time intervals, gold nanoparticles (Au NPs) with different shapes, from spherical to bone-shaped, were obtained. The physical properties of the synthesized Au NPs were investigated using transmission electron microscopy (TEM) combined with selected area electron diffraction patterns (SAED) and ultraviolet-visible spectroscopy (UV–vis). The TEM images showed, that stopping the synthesis after one minute lead to the formation of small spherical Au NPs, which evolved to the cubic shape, rods and bone-shaped Au NPs after 15 min, 30 min, 2 h, respectively. SAED patterns showed, that all the obtained Au NPs were crystalline. UV–vis spectra revealed, that the light absorbance depends on the shape of the Au NPs. Moreover, the effects of the time factor in the formation of Au NPs on the effective conversion of electromagnetic energy into thermal energy, was studied. Furthermore, simulated photothermal therapy (PTT) in combination with the obtained NPs, was done for two cancer cell lines SW480 and SW620. The mortality of cells after using the differently shaped Au NPs as photosensitizers is between 18 % and 52 % and increases with the decrease of the synthesis time.