Nanophotonic Crescent Moon Structures with Sharp Edge for Ultrasensitive Biomolecular Detection by Local Electromagnetic Field Enhancement Effect

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Abstract
We present novel gold nanophotonic crescent moon structures with a sub-10 nm sharp edge, which can enhance local electromagnetic field at the edge area. The formation of unconventional nanophotonic crescent moon structure is accomplished by using a sacrificial nanosphere template and conventional thin film deposition method, which allows an effective batch nanofabrication and precise controls of nanostructure shapes. Unique multiple scattering peaks are observed in a single gold nanocrescent moon with dark-field white light illumination. A 785 nm near-infrared (NIR) diode laser was used as the excitation source to induce the amplified scattering field on the sharp edge of the single gold nanocrescent moon. The Raman scattering spectrum of Rhodamine 6G molecules adsorbed on the single gold nanocrescent moon are characterized, and the Raman enhancement factor of single gold nanocrescent moon is estimated larger than 1010, which suggests the potential applications of gold nanocrescent moons in ultrasensitive biomolecular detection and cellular imaging using surface enhanced Raman spectroscopy.