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Slab photonic crystals (PhCs) are photonic structures used in many modern optical technologies. Fabrication of these components is costly and usually involves eco-unfriendly methods, requiring modern nanofabrication techniques and cleanroom facilities. This work describes that diatom microalgae evolved elaborate and highly reproducible slab PhCs in the girdle, a part of their silicon dioxide exoskeletons. Under natural conditions in water, the girdle of the centric diatom Coscinodiscus granii shows a well-defined optical pseudogap for modes in the near-infrared (NIR). This pseudogap shows dispersion toward the visible spectral range when light is incident at larger angles, eventually facilitating in-plane propagation for modes in the green spectral range. The optical features can be modulated with refractive index contrast. The unit cell period, a critical factor controlling the pseudogap, is highly preserved within individuals of a long-term cultivated inbred line and between at least four different C. granii cell culture strains tested in this study. Other diatoms present similar unit cell morphologies with various periods. Diatoms thereby offer a wide range of PhC structures, reproducible and equipped with well-defined properties, possibly covering the entire UV-vis-NIR spectral range. Diatoms therefore offer an alternative as cost-effective and environmentally friendly produced photonic materials.

For a long time silicon has been forgotten about its involvement in the biosphere, however, this chemical element is very important for some organisms such as plants and animals. Silicon is dragged into the sea by rivers, where is absorbed by diatoms, which settle when they die, leaving less bioavailable silicon for other organisms. Settled silicon returns to the biosphere with subduction and mountain building. Other organisms that require silicon in metabolism are sponges and radiolarians, also it is a component of the blood and bones of animals. In plants silicon plays a protective role against biotic and abiotic stresses and in some countries silicon is used in the fertilization of some crops. The aim of this work is to raise awareness of the importance of silicon and the scopes of its study and application., Durante mucho tiempo se olvidó u obvió la participación del silicio en la biósfera; sin embargo, este elemento químico es de gran importancia para algunos organismos como plantas y animales. Es arrastrado al mar por los ríos, donde es absorbido por las diatomeas, que al morir se sedimentan, quedando menos silicio biodisponible para otros organismos. El silicio sedimentado retorna a la biósfera con la subducción y formación de montañas. Otros organismos que requieren silicio en su metabolismo son las esponjas y los radiolarios; también forma parte de los componentes de la sangre y de los huesos de los animales. En las plantas juega un papel protector contra estrés biótico y abiótico y en algunos países lo emplean en la fertilización de algunos cultivos. El presente trabajo es con la finalidad de dar a conocer la importancia del silicio y los alcances que puede tener su estudio y aplicación.

For a long time silicon has been forgotten about its involvement in the biosphere, however, this chemical element is very important for some organisms such as plants and animals. Silicon is dragged into the sea by rivers, where is absorbed by diatoms, which settle when they die, leaving less bioavailable silicon for other organisms. Settled silicon returns to the biosphere with subduction and mountain building. Other organisms that require silicon in metabolism are sponges and radiolarians, also it is a component of the blood and bones of animals. In plants silicon plays a protective role against biotic and abiotic stresses and in some countries silicon is used in the fertilization of some crops. The aim of this work is to raise awareness of the importance of silicon and the scopes of its study and application., Durante mucho tiempo se olvidó u obvió la participación del silicio en la biósfera; sin embargo, este elemento químico es de gran importancia para algunos organismos como plantas y animales. Es arrastrado al mar por los ríos, donde es absorbido por las diatomeas, que al morir se sedimentan, quedando menos silicio biodisponible para otros organismos. El silicio sedimentado retorna a la biósfera con la subducción y formación de montañas. Otros organismos que requieren silicio en su metabolismo son las esponjas y los radiolarios; también forma parte de los componentes de la sangre y de los huesos de los animales. En las plantas juega un papel protector contra estrés biótico y abiótico y en algunos países lo emplean en la fertilización de algunos cultivos. El presente trabajo es con la finalidad de dar a conocer la importancia del silicio y los alcances que puede tener su estudio y aplicación.

This project has been aimed at: 1) identifying gas/solid reaction conditions for converting biologically-derived micro/nanotemplates into other oxides without a loss of the starting 3-D shape and fine features, and 2) evaluating the nanochemical/nanostructural evolution during such reactive conversion. The most significant accomplishments have been: 1) Development of an oxidation-reduction reaction process for converting biosilica-based micro/nanoassemblies into MgO nanoparticle structures with a preservation of the starting 3-D shape and fine features at temperatures as low as 700 deg C; 2) Development of a two-Step oxidation-reduction reaction process for converting biosilica-based micro/nanoassemblies into CaO nanoparticle structures with a preservation of the starting 3-D shape and fine features at temperatures as low as 1000 deg C; 3) Development of a two-step metathetic reaction process for converting biosilica-based micro/nanoassemblies into TiO2 nanoparticle structures with a preservation of the starting 3-D shape and fine features at temperatures as low as 350 deg C; 4) Identification of novel reaction paths accessed during conversion of biosilica structures into magnesia (via formation of forsterite as an intermediate product) and titania (via formation of the intermediate compound, titanium oxyfluoride); 5) Identification of peptides that promote room-temperature formation of germania nanoparticle networks., The original document contains color images. All DTIC reproductions will be in black and white. Prepared in cooperation with Ohio State University, Columbus, OH.