Plasmonic gold islands enhanced photobioreactors

The field of plasmonics provides control of light at the nanometer scale, well below the wavelength of light in free space. Recently, it has been shown that suspensions of plasmonic nanoparticles can be exploited to improve light absorption by micro-algae and that propagating surface plasmons can be used to transfer light to biofilms of photosynthetic bacteria. Here we present our recent work with localized surface plasmons (LSP) excited on gold island films to provide an enhanced physical and optical environment for photosynthetic bacterial cultivation and opportunities for improved photobioreactor design. I. INTRODUCTION Plasmonics is an emerging field interested in understanding and applying the unique optical properties of nanoscale metals when they interact with light. At specific wavelengths the free electrons of the metal oscillate in resonance in what is referred to as a plasmon, which can have a dramatic impact on both near and far electromagnetic fields. This phenomenon has been exploited in bio-sensing (1), (2), refractive index sensing (3), negative index materials (4), nanolithography (5), and photovoltaics (6). Recently, investigations have been conducted into using the optical effects of plasmon resonances to capture and confine light in photobioreactors used to cultivate photosynthetic microorganisms in order to increase their efficiency (7), (8). Efficient cultivation of these organisms is of interest due to their increasing importance in products as varied as nutritional supplements to bio-fuel production. Traditional closed system cultivation approaches however, suffer from low efficiencies largely driven by poor light distribution in the reactor volume. In this work we demonstrate how plasmonic nanostructures can be used to confine light to surfaces, providing enhanced illumination with which to grow photosynthetic bacteria efficiently.