Gold nanoparticles have attracted many scientists because of their unique optical characteristics. In this work, we are going to introduce gold nanoparticles with a novel “confeito-like” structure synthesized by a green-chemistry method. The size of nanoparticle was controlled in the range from 20 to 100 nm in diameter by changing the concentration of protecting agent, citric acid, in the reaction solution.
The confeito-like gold nanoparticles were expected to provide dominant optical properties because of their unique surface morphology which concentrates the surface plasmon on the tips. Thus, several spectroscopies were performed to characterize the optical properties of confeito-like gold nanoparticles. UV-Vis-NIR spectra of their dispersions demonstrated the large red-shift of plasmon absorption bands toward 600 nm, while the conventional spherical gold nanoparticles have the band at 530 nm. Although the spherical gold nanoparticles significantly regulated the fluorescence of uranine, the confeito-like gold nanoparticles had less quenching effects. Raman scattering of rhodamine 6G was strongly intensified in the dispersions and on the films of confeito-like gold nanoparticles, although the spherical gold nanoparticles have less enhancing effects. Infrared absorption of eicosanoid acid was also enhanced by the films of confeito-like gold nanoparticles; however the enhancing factor was not high. These characteristics of the confeito-like gold nanoparticles suggest that the confeito-like gold nanoparticles are useful to design plasmonic devices and can be applicable for bio-probes and ultrahigh-sensitive sensors.

Gold nanoparticles have attracted many scientists because of their unique optical characteristics. In this work, we are going to introduce gold nanoparticles with a novel “confeito-like” structure synthesized by a green-chemistry method. The size of nanoparticle was controlled in the range from 20 to 100 nm in diameter by changing the concentration of protecting agent, citric acid, in the reaction solution.
The confeito-like gold nanoparticles were expected to provide dominant optical properties because of their unique surface morphology which concentrates the surface plasmon on the tips. Thus, several spectroscopies were performed to characterize the optical properties of confeito-like gold nanoparticles. UV-Vis-NIR spectra of their dispersions demonstrated the large red-shift of plasmon absorption bands toward 600 nm, while the conventional spherical gold nanoparticles have the band at 530 nm. Although the spherical gold nanoparticles significantly regulated the fluorescence of uranine, the confeito-like gold nanoparticles had less quenching effects. Raman scattering of rhodamine 6G was strongly intensified in the dispersions and on the films of confeito-like gold nanoparticles, although the spherical gold nanoparticles have less enhancing effects. Infrared absorption of eicosanoid acid was also enhanced by the films of confeito-like gold nanoparticles; however the enhancing factor was not high. These characteristics of the confeito-like gold nanoparticles suggest that the confeito-like gold nanoparticles are useful to design plasmonic devices and can be applicable for bio-probes and ultrahigh-sensitive sensors.

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