Charms for E-Learning: A Case Study

Frontiers of light manipulation in natural, metallic, and dielectric nanostructures

“…This could represent a mechanism by which diatoms are able to efficiently collect photosynthetic active radiation and, simultaneously, protect themselves from harmful ultraviolet radiation [93]. Other mechanisms potentially involved in UV-shielding are absorption by frustule silica and UV-visible wavelength conversion induced by nanostructured silica photoluminescence [72]. The confinement of optical radiation happens even closer to the valve, thus inside the cell, when considering water as the environment in which the valve is immersed, as numerically demonstrated in Ref.…”

“…from harmful agents (e.g. bacteria and viruses) [69,70]; reduction of sinking speed [71]; finally, optimization of coupling with sunlight [72]. Several optical properties of frustules were known since the early 1970s [73]: if observed in the proper azimuth and in a dark background, diatom frustules present brilliant colors due to diffraction induced by their ornamentations; the frustule nm; D = 745±43 nm.…”

“…This process, typical of several forms of nanostructured silica such as silica nanoparticles, oxidized porous silicon, sol gels, silicon-oxide thin films, and silica-based mesoporous materials, is to be ascribed mainly to a variety of surface defects, including non-bridging oxygen hole centers, neutral oxygen vacancies, silanol groups, and to the recombination of selftrapped excitons localized by self-induced lattice distortions in presence of strong electron-phonon interactions [125][126][127]. Furthermore, in the case of diatoms, also organic residuals incorporated in the frustule silica matrix contribute to visible photoluminescence [72,128]. De Stefano et al [129] firstly observed that green emission from Thalassiosira rotula frustules is sensitive to the chemical composition of the environment, both in terms of emission wavelength and peak intensity.…”

“…from harmful agents (e.g. bacteria and viruses) [69,70]; reduction of sinking speed [71]; finally, optimization of coupling with sunlight [72]. Several optical properties of frustules were known since the early 1970s [73]: if observed in the proper azimuth and in a dark background, diatom frustules present brilliant colors due to diffraction induced by their ornamentations; the frustule [78] of several diatom species presents optical activity, being able to change the state of polarization of the incident radiation; some diatoms of the genus Actinocyclus switch from one color distribution to the complementary one as the mode of illumination changes from bright field to dark field.…”

Photonic Crystal Enhanced SERS Detection of Analytes Separated by Ultrathin Layer Chromatography Using a Diatom Frustule Monolayer

“…The ordered pore arrays of diatom frustule biosilica resemble a 2D photonic crystal and possess photonic properties [ 7 ] that enable their future use as optical waveguides, optical transducers, [ 8 ] and ultraviolet filters. [ 9 ] The addition of optically active materials to the diatom frustule imparts optoelectronic properties to the diatom photonic crystal.…”