Nanodiamond/gold nanorod nanocomposites with tunable light-absorptive and local plasmonic properties

Nanodiamonds (NDs) have potential as platform materials for biological and biomedical applications depending on the combinatorial complex designs. Bimetallic nanocomposites with ND and gold nanorods (AuNRs) were synthesized and obtained at tunable UV absorption wavelengths by controlling the aspect ratio of AuNR. The nanodiamond/AuNR nanocomposites (NDAuNR) with fine tuning ultraviolet/visible/near-infrared (UV–vis-NIR) extinction were prepared using a cetyltrimethylammonium bromide (CTAB)-surfactant-based seedless growth method. NDAuNRs varied with UV absorption wavelengths and aspect ratios, providing the surface-enhanced Raman scattering (SERS) effect. Compared to AuNR/800 nm with the same UV absorption wavelength, NDAuNR/800 nm showed 12.1% and 9.8% higher SERS intensity ratios of I₁₆₂₀/I₅₂₀ and I₄₂₀/I₅₂₀, respectively, for methylene blue of concentration 10⁻⁵ M. The enhanced SERS intensity of NDAuNR/800 nm indicates that electron mobility was facilitated at the interface between ND and AuNRs, and a larger contact area owing to a larger aspect ratio resulted in a higher SERS effect. The study demonstrated that NDAuNR nanocomposites enhanced the photo-responsive reactivity in SERS, resulting in potentially promising biomedical applications in sensor, imaging, and photothermal therapy. NDs provide platform substances to magnify gold resonance.