文摘

Gold (Au) nanoshells are known to exhibit many attractive optical properties caused by the excitation of localized surface plasmon resonances (LSPRs). Reducing the symmetry of these nanoshells has a number of interesting consequences, such as exciting different plasmon modes, making the optical response angle-dependent, and enhancing the local electric field intensity. In this paper, a versatile procedure involving ion milling has been developed to fabricate reduced-symmetrical Au semishells. This allows us to precisely control the reduced-symmetrical geometry and, particularly, the upward orientation of the created nanoaperture. These features, along with a combination of finite different time domain (FDTD) calculations, suggest Au semishell monolayer structures for a potential application in surface-enhanced Raman spectroscopy (SERS)-based biomolecule detection. Au semishells, additionally, exhibit advantageous features over Au nanoshells, for example, a more pronounced red shift of LSPR bands by tuning the aspect ratio, a larger tuning range of optical properties, increased optical absorption at higher wavelengths, and an enhanced local electromagnetic field.