Controlled synthesis of gold nanorods and integrated with titanium dioxide for enhancing visible light‐driven antioxidant activity

Abstract In this work, gold nanorods (AuNRs) with well‐controlled aspect ratios were prepared using a modified seed‐growth method and covered by TiO 2 layers through the hydrothermal reaction to improve stability. Integrating TiO 2 with plasmonic rod‐like gold nanoparticles could enhance their photo activity by the local surface plasmon resonance (LSPR) effect. AuNRs aspect ratios were controlled by varying the amount of seed solution, reducing agents, surfactant (CTAB), and titanium (IV) but oxide. The optical properties of formed AuNRs can be tuned in the spectral range from 400 to 900 nm by adjusting the ratio between seed solution and reducing agent concentration. Besides, the absorption of the UV‐light function of TiO 2 and the antioxidant properties of gold nanoparticles were also integrated to prepare a kind of multifunctional material. The obtained AuNRs/TiO 2 were then determined by ultraviolet‐visible spectroscopy (UV‐Vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high‐resolution transmission electron microscopy (HR‐TEM), selected area electron diffraction (SAED), and energy‐dispersive X‐ray spectroscopy (EDS). Microscopic images (TEM, SEM) revealed that the average particle size of the AuNRs decorated in the titanium dioxide ranged from 20 to 60 nm, depending on the experimental parameters. Furthermore, HRTEM, EDS, and SAED results provided more precise information insight into the formed gold nanocrystals. The AuNRs/TiO 2 exhibited superior antioxidant activity by reducing free 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radicals at different concentrations. The results indicated that AuNRs/TiO 2 improves antioxidant and optical absorption activities. The antioxidation effect was proved more excellent than solely used of spherical, rod‐liked gold nanoparticles or TiO 2 nanoparticles. This novel design of AuNRs/TiO 2 may open a new avenue for facilitating multifunctional nanoparticles in cosmetic applications.