Colorimetric Plasmon Resonance Imaging Using Nano Lycurgus Cup Arrays

Lycurgus cup [ 1 ] created by ancient Romans 2000 years ago can appear different colors depending on the direction of light illumination in which it is viewed due to metal nanoparticle optical scattering. It has inspired nanoplasmonics research over the past decade. [ 2–5 ] Here we present a nanoscale Lycurgus cup arrays (nanoLCA) device that has the property of appearing green when light is shone on to it and changing the color to red without direct light illumination (see Supporting movie). The above colorimetric device fabricated on transparent plastic substrate consists of about one billion nano Lycurgus cups in an array with subwavelength opening and decorated with metal nanoparticles on side walls. Strikingly different from metallic nanohole arrays [ 6 ] or quasi-3D plasmonic crystals [ 7 ] with extraordinary optical transmission which usually give rise to multiple transmission spectral features, nanoLCA exhibits metal nanoparticle-like single transmission wavelength peak in the whole visible ranges. Electromagnetic simulation revealed the plasmon resonance scattering modes of the metal nanoparticles on the cup side walls and the corresponding single peak wavelength scattering light selectively transmitted by the nanoLCA. The huge transmission and refl ection wavelength shifts upon binding of molecules on our fl exible, high-throughput, large area nanoLCA device are up to 200 nm (with maximum sensitivity of 46000 nm per refractive-index unit (RIU) and fi gure of merit (FOM) of 1022), much greater than the typical nano particle plasmon resonance wavelength shift and large enough to detect the color differences directly by naked eyes and conventional bright fi eld microscopes. This enables to eliminate the need for precision spectrometer or fl uorescence labeling. We demonstrated the