A new tactic that using Ag nanorice trimer as surface-enhanced hyper Raman scattering substrate is proposed for realizing maximum signal enhancement. In this paper, we numerically simulate and theoretically analyze the optical properties of the nanorice trimer consisting of two short nanorices and a long nanorice. The Ag nanorice trimer can excite Fano resonance at optical frequencies based on the strong interaction between the bright and the dark mode. The bright mode is attributed to the first longitudinal resonance of the short nanorice pair, while the dark mode originates from the third longitudinal mode resonance of the long nanorice. The electric field distributions demonstrate that the two resonances with the largest field strength correspond to the first-order resonance of the long nanorice and the Fano resonance of the trimer, respectively. Two plasmon resonances with maximum electromagnetic field enhancements and same spatial hot spot regions can match spectrally with the pump and second-order Stokes beams of hyper Raman scattering, respectively, through reasonable design of the trimer structure parameters. The estimated enhancement factor of surface-enhanced hyper Raman scattering can achieve as high as 5.32 × 1013.

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The development of new surface-enhanced Raman scattering (SERS) substrates is primarily motivated by designing synthetic substrates to obtain the significant signal enhancement. In this paper, a large-scale carnation-shaped Ag meso-flowers monolayer with sufficient “hot spots” has been synthesized on copper foil without using any capping agent. In dimethyl sulfoxide, AgNO3 is reduced by Cu for 60 min at 35 °C through the galvanic displacement reaction, and carnation-shaped Ag meso-flowers with good crystallinity and high purity are obtained. The as-fabricated carnation-shaped Ag meso-flowers monolayer is used as novel SERS substrates. Non-fluorescent 4-mercaptobenzoic acid is selected as the probe molecule to test the SERS activity, uniformity and enhancement factors (EF) of the monolayer. Experimental results show that the EF of the carnation-shaped Ag meso-flowers monolayer is up to 7.06×108 and the limit of detection is 10-11 M. Meanwhile, the biocompatibility of the carnation-shaped silver meso-flowers monolayer is tested for red blood cells detection. SERS measurements demonstrate that the carnation-shaped silver meso-flowers monolayer has good activity, uniformity and biocompatibility, and can be used as an outstanding SERS substrate, which has a broad application prospect in numerous chemical and biochemical sensing applications.

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