Plasmonic Metaparticles on a Blackbody Create Vivid Reflective Colors for Naked‐Eye Environmental and Clinical Biodetection

Abstract

Plasmonic dipoles are famous for their strong absorptivity rather than their reflectivity. Here, the as-yet unknown specular reflection and the Brewster effect of ultrafine plasmonic dipoles, metaparticles, are introduced and exploited as the basis of new design rules for advanced applications. A configuration of "Plasmonic metaparticles on a blackbody" is demonstrated and utilized for the design of a tailored perfect-colored absorber and for visual detection of environmental dielectrics that is not readily done by extinction plasmonics. Moreover, the Plasmonic Brewster Wavelength (PBW) effect is introduced as a new platform for the naked-eye and bulk biodetection of analytes. The technique operates based on slight changes of molecular polarizability which is not detectable via conventional plasmon resonance techniques. As a specific highlight, the clinical applicability of the PBW method is demonstrated while addressing the transduction plasmonic techniques' challenge in detection of bulk refractive index changes of the healthy and diseased human serum exosomes. Finally, the sputtering-based fabrication method used here is simple, inexpensive, and scalable, and does not require the sophisticated patterning approach of lithography or precise alignment of light coupling for the biodetection.

Solar Aluminum Kitchen Foils with Omnidirectional Vivid Polarizonic Colors

“…It has been thought that the shiny and vivid colors are solely achievable by the optically symmetric and periodically structured materials, which is “not quite right,” based on our recent progresses in the field. Several disordered structures consisting of nanoparticles and molecules that are able to show coherent and cooperative specular reflection “polarizonic” responses have been recently introduced by us and implemented for creation of vivid colors. Despite various merits with respect to structural polarizonic coloration, this mode of specular reflected color is angular and polarization dependent thus inefficient for different applications such as optical measurement systems, colored display devices, and solar absorbers.…”

“…Accordingly, as described by the Lorentz classical harmonic oscillators, a localized state is assigned at the longitudinal plasma frequency. In the simplest localized plasmonic case, the alternating surface charges form an oscillating dipole that radiates electromagnetic waves to the far field . This simple model for the dipole is evocative of an optical antenna and well known as the electronic polarization occurring at the optical frequencies that causes a local reflection what we call “polarizonic.” Accordingly, the metal behaves as a series of classical free electrons and classical harmonic oscillators with a characteristic broad reflection of the free electron “continuous” and a localized reflection “discontinuous” at the plasma frequency .…”

“…Most interestingly, the Brewster wavelength is red shifted relative to the one appearing at the Brewster angle under the p‐polarized light. The Brewster wavelength effect, we introduced recently as a means for sensing the net polarity of a plasmonic composite, acts through the dipolar interaction between the excited dipoles and the host matrix. Such an interaction governs a net dipole moment at the interface based on the interfacial polarizability effect …”

“…As a prototype for this concept, here, we design an inexpensive, color tailored solar foil via coating of a kitchen Al foil with an ultrathin layer of Au nanocomposites containing different Au nanoparticle filling factors and various dielectric hosts. Au was implemented for the design of such a perfect‐colored absorber based on our previous studies on both well‐known absorbing metals of Au and Ag . Given the optical constants (including RI ( n ) and extinction coefficient ( k )) of both the metals in the visible range, the intrinsic absorption of gold is much higher than that of silver, and for this reason it was selected for the construction of the solar absorber.…”

Printing of Highly Vivid Structural Colors on Metal Substrates with a Metal‐Dielectric Double Layer

“…Structural colors arise from the interaction of light with surface structures . Fundamental optical phenomena such as interference, diffraction, scattering, and resonance are the origins of structural colors.…”