Abstract
In this paper, we reported a simple one-step synthesis of highly-branched gold nanostructures (HGNs) in high yields. The reduction of HAuCl4 was accomplished by dopamine hydrochloride in the reaction system. By varying the amount of dopamine hydrochloride, HAuCl4 and the reaction temperature, we managed to tune the size of the HGNs from 200 to 600 nm. Systematic analysis revealed that the optical properties and surface-enhanced Raman scattering (SERS) activities of the HGNs were highly dependent on their morphology and size. In terms of their SERS activities, it was found that the HGNs synthesized at 60 °C with 2.0 mL dopamine hydrochloride (53 mM), 0.4 mL HAuCl4 (50 mM) exhibited the largest SERS enhancement. When the HGNs were assembled onto the silicon wafers, outstanding SERS efficiency was obtained with a detection limit of 5×10-10 M of 4-mercaptobenzoic acid (4-MBA) and the analytical enhancement factor (AEF) was calculated to be 7×107. Besides, the 3-aminopropyltriethoxysilane (APTES)-functionalized substrates with the HGNs displayed remarkable signal reproducibility with relative standard deviation (RSD) of 3.57%. All these results demonstrated that the SERS-active substrates held great promise to be applied in trace-level molecule detection in the future.
Highlights
INTRODUCTIONSimilar regions were found to be close to the sharp tip of the droplet-shaped particles, which could be ascribed to the increasing surface charge density at the tip.[6] Thanks to hot spots at the tips, the sphere with a tip displayed a much larger surface-enhanced Raman scattering (SERS) enhancement as compared with the sphere with the same size.[7] To fabricate SERS-active substrates with plenty of hot spots, different nanostructures have been investigated, including nanostars, porous nanosheet and polyvinylpyrrolidone (PVP)-Ag nanocubes films.[8,9,10] the controllable fabrication of a reproducible SERS substrate still limits the application of SERS in single molecules’ quantitative analysis
surface-enhanced Raman scattering (SERS) has been attracting attention as a promising technique in identifying single molecule characterized by molecular fingerprint specificity and high sensitivity
The crystalline structure of the highly-branched gold nanostructures (HGNs) was characteristic by high-resolution TEM images (HRTEM) (Fig. 1(D)), which showed that the interplanar spacing of the tips was measured to be 0.240 nm, indicating the HGNs grew preferentially on {111} planes
Summary
Similar regions were found to be close to the sharp tip of the droplet-shaped particles, which could be ascribed to the increasing surface charge density at the tip.[6] Thanks to hot spots at the tips, the sphere with a tip displayed a much larger SERS enhancement as compared with the sphere with the same size.[7] To fabricate SERS-active substrates with plenty of hot spots, different nanostructures have been investigated, including nanostars, porous nanosheet and polyvinylpyrrolidone (PVP)-Ag nanocubes films.[8,9,10] the controllable fabrication of a reproducible SERS substrate still limits the application of SERS in single molecules’ quantitative analysis.
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