Nanoplasmonics and surface enhanced spectroscopy 

Laser-induced periodic Ag surface structure with Au nanorods plasmonic nanocavity metasurface for strong enhancement of adenosine nucleotide label-free photoluminescence imaging 
Yeshchenko O.A.1, Golovynskyi S.2, Kudrya V.Yu.1, Tomchuk A.V.1, Dmitruk I.M.1, Berezovska N.I.1, Teselko P.O.1, Zhou T.2, Xue B.2, Golovynska Iu.2, Lin D.2, Qu J.2
1 Physics Department, Taras Shevchenko National University of Kyiv, Volodymyrska Street 64/13, Kyiv 01601, Ukraine.
E-mail: nastiona30@gmail.com
2 Center for Biomedical Photonics, Shenzhen University, 1068 Xueyuan Avenue, Shenzhen University Town, Shenzhen 518060, China

In this study, the effect of a strong enhancement of photoluminescence of 5′-deoxyadenosinemonophosphate (dAMP) by the plasmonic nanocavity metasurface composed of the silver femtosecond laser-induced periodic surface structure (LIPSS) and gold nanorods or nanospheres has been realized at room temperature. The highest value of 1220 for dAMP on the Ag-LIPSS/Au nanorod metasurface has been explained to be a result of the synergetic effect of the generation of hot spots near the sharp edges of LIPSS and Au nanorod tips together with the excitation of collective gap mode of the cavity due to strong near-field plasmonic coupling. A stronger plasmonic enhancement of the phosphorescence compared to the fluorescence is achieved due to a greater overlap of the phosphorescence spectrum with the surface plasmon spectral region. The comparison of Ag-LIPSS/Au nanorod and Ag-LIPSS/Au-nanosphere metasurfaces shows a considerably higher enhancement for the metasurface containing Au nanorods. 
Thus, the hybrid cavity metasurfaces containing metal LIPSS and nonspherical metal nanoparticles with sharp edges are promising for high-sensitive label-free detection and imaging of biomolecules at room temperature.

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