Surface enhanced Raman scattering (SERS) substrate based on fabricated Ag@Au core-shell dendrite was achieved. Ag dendrites were grown on Si wafer by the hydrothermal corrosion method and Au nanofilm on the surface of Ag dendritic nanostructure was then fabricated by chemical reduction. With the help of sodium borohydride in water, Au surface absorbates such as thiophene, adenine, rhodamine, small anions (Br– and I–), and a polymer (PVP, poly(N-vinylpyrrolidone)) can be completely and rapidly removed. After four repeatable experiments, the substrate SERS function did not decrease at all, indicating that the Ag@Au dendrite should be of great significance to SERS application because it can save much resource. Six-month-duration stability tests showed that the Ag@Au core-shell dendrite substrate is much more stable than the Ag dendrite substrates. We have also experimented on fast detection of Cd2+ at 10−8  M concentration by decorating single-stranded DNA containing adenine and guanine bases on the surface of this Ag@Au dendrite. Finite-difference time-domain simulations were carried out to investigate the influence of Au nanolayer on Ag dendrites, which showed that the local electric fields and enhancement factor are hardly affected when a 4 nm Au nanolayer is coated on Ag dendrite surface.

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Quantitative research on the localized surface plasmon resonance of metallic nanostructures has received tremendous interest. However, most current studies have concentrated on theoretical calculation because it is difficult to obtain monodisperse metallic nanostructures with high purity experimentally. In this work, gold nanodimers (GNDs) with high uniformity are fabricated through DNA-directed self-assembly of gold nanoparticles and then used as substrates for surface-enhanced Raman scattering (SERS). The dependence of the SERS properties of the substrates on the size of the gold particles and the position of Rhodamine B (RB) molecules is systematically studied using the DNA-directed self-assembled GNDs with Raman-active RB molecules immobilized in different positions between pairs of gold nanoparticles as a model system. Theoretical simulations conducted using the finite difference time domain (FDTD) method confirm the structure-dependent SERS characteristics of the GNDs, with good agreement between the FDTD simulation data and experimental results.