Light manipulation in a marine diatom
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Manfred Sumper Lehrstuhl Biochemie I, Universität Regensburg, 93053 Regensburg, Germany
Pete Vukusica) School of Physics, University of Exeter, Exeter EX4 4QL, United Kingdom (Received 30 April 2008; accepted 8 July 2008)
Diatoms are well known for the intricately patterned nanostructure of their silica-based cell walls. To date, the optical properties of diatom cell-wall ultrastructures have largely gone uncharacterized experimentally. Here we report the results of a detailed experimental investigation of the way in which light interacts with the ultrastructure of a representative centric diatom species, Coscinodiscus wailesii. Light interaction both with individual valves and whole bivalves of the diatom C. wailesii was measured. Significant sixfold symmetric diffraction through the valve ultrastructure was observed in transmission and quantified to efficiencies that were found to be strongly wavelength dependent; approximately 80% for red, 30% for green, and 20% for blue light. While these results may potentially offer insight into the role of periodic nanostructure in diatom selection, they are also important for consideration in the design of biomimetic optics-based diatom applications. I. INTRODUCTION
As biological entities, diatoms are ubiquitously present in nearly all aquatic environments on earth. They are eukaryotic algal organisms that comprise only one cell, that are photosynthetic, and that have a long scientific history of study, partly because of the astonishingly intricate design and architecture of their silica-based cell walls.1 Recently there has been increasing interest surrounding the exploitation of marine phytoplankta, principally diatoms, for use in a range of technological applications.1–3 There are three principle reasons for this. The first is their species-related range of shapes, sizes, and cell-wall nanopatterning.3 For given specimens, this potentially offers a large range of available internal volume, of mechanical and optical properties, and of diffusion of material through the pores in their cell walls.4 The second reason is the way in which diatoms may be influenced to biomineralize a range of materials5,6 or to be used as templates for the fabrication of nanopatterned structures made of other materials such as silicon.7 Thirdly, the chemistry of their surfaces may be modified so that they may be appended with biologically active components.8 In one or more of these ways, processes of biofunctionalization may transform collections of ordinary diatoms into finely tuned potential microdevices and technological components.1,2,4 The fabrication of designer diatom morphologies and a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0381 J. Mater. Res., Vol. 23, No. 12, Dec 2008
surface biochemistries that are appropriate for use in a range of applications is a fascinating research goal. The manufacturing techniques for this endeavor have been progressing rapidly.9 They include: cell-culture and genetic engineering mediated biofunctionali
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