Facile Synthesis and Photothermal Stability of Silica‐Coated Gold Nanoworms

Abstract Silica‐coated Au nanoparticles (NPs) have attracted significant attention due to their unique plasmon properties and biocompatibility. This is especially significant for NPs with their plasmon peaks in the near‐infrared (NIR) and within the therapeutic window. In this study, we have synthesized worm‐shaped Au NPs, called nanoworms (NWs) with an intense surface plasmon absorbance peak in the NIR, which were subsequently coated with silica. These NPs were then exposed to a nanosecond pulsed laser with varying fluences at a wavelength of 1064 nm and their UV–visible (vis) spectra were recorded to analyze the effects. Upon laser exposure, the longitudinal plasmon peaks exhibited a blue shift, which was more pronounced in the unmodified NWs. The silica‐coated NWs retained their optical properties even at higher laser fluences. However, for both bare and silica‐coated NWs, the required fluences to induce the shape modification were significantly higher than those previously reported for Au nanorods. These experiments highlight that the silica‐coated NWs are highly promising for biomedical applications, e.g., for various therapeutic and diagnostic uses, where maintaining performance under higher laser fluences is crucial.