We present the concept of a solar thermo-photovoltaic (STPV) collection system based on
a large-area, nanoimprint-patterned film of plasmonic structures acting as an integrated
solar absorber/narrow-band thermal emitter (SANTE). The SANTE film concept is based
on integrating broad-band solar radiation absorption with selective narrow-band thermal
IR radiation which can be efficiently coupled to a photovoltaic (PV) cell for power
generation. By employing a low reflectivity refractory metal (e.g., tungsten) as a plasmonic
material, we demonstrate that the absorption spectrum of the SANTE film can be
designed to be broad-band in the visible range and narrow-band in the infrared
range. A detailed balance calculation demonstrates that the total STPV system
efficiency exceeds the Shockley–Queisser limit for emitter temperatures above
Te = 1200 K, and achieves an efficiency as high as 41% for
Te = 2300 K. Emitter temperatures in this range are shown to be achievable under modest sun
concentrations (less than 1000 suns) due to the thermal insulation provided by the SANTE
film. An experimental demonstration of the wide-angle, frequency-selective absorptivity is
presented.
A simple metamaterial-based wide-angle plasmonic absorber is introduced, fabricated, and experimentally characterized using angle-resolved infrared spectroscopy. The metamaterials are prepared by nano-imprint lithography, an attractive low-cost technology for making large-area samples. The matching of the metamaterial's impedance to that of vacuum is responsible for the observed spectrally selective "perfect" absorption of infrared light. The impedance is theoretically calculated in the single-resonance approximation, and the responsible resonance is identified as a short-range surface plasmon. The spectral position of the absorption peak (which is as high as 95%) is experimentally shown to be controlled by the metamaterial's dimensions. The persistence of "perfect" absorption with variable metamaterial parameters is theoretically explained. The wide-angle nature of the absorber can be utilized for sub-diffraction-scale infrared pixels exhibiting spectrally selective absorption/emissivity.
Rapid and portable detection of saxitoxin (STX) and its many congeners is highly desirable to prevent paralytic shellfish poisoning due to red tide or harmful algal blooms. In this work, we describe successful preliminary efforts to develop a very sensitive general STX family test strip
employing highly fluorescent red quantum dots (Qdot 655) to detect as little as 0.5 to 1 part per billion (ppb or ng/ml) of STX with a dynamic range extending to 20,000 ppb after the prototype dipstick assay was optimized. A competitive format was necessitated by the small molecule nature
of STXs having only one epitope, but the decrease in Qdot fluorescence was clearly visible to the naked eye as a function of increasing STX concentration in aqueous buffer. The competitive displacement assay format required conjugation of a primary amine in STX to carboxyl-Qdot 655 via a covalent
carbodiimide coupling reaction which was validated by an electrophoretic mobility band shift assay.
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