Controlled Nanoporous Structures of a Marine Diatom

Abstract

We demonstrated chemical etching of a marine diatom shell with 1 N NaOH for controlling the pore size of nanoporous structures of the shell under various conditions. Scanning electron microscopy (SEM) images clearly revealed that the pore size of the diatom shells was regulated in the case of etching at 25 degrees C. In contrast, fluctuations in the etched structures was relatively high even during short periods degradation at 40, 60, and 90 degrees C; therefore, controlled nanoporous structures could not be fabricated. This is the first example of artificial modification of natural diatom shells at the nanoscale although diatom shells have been widely used in industry. In addition, a backbone-like structure was observed during the etching process. The structure was similar to the intermediate structure observed during the primitive stage of the diatom cell growth. Probably, this information is valuable for studying the mechanism of nanoporous structures of diatoms.

Importance of observation interval in two-dimensional video analysis of individual diatom cells

“…frustule. The dimensions of the frustule along the major and minor axes were nearly 15 and 3 microns, respectively, as previously reported (Umemura et al 2007b). …”

Morphology and Physical-Chemical Properties of Baked Nanoporous Frustules

“…[6][7][8][9] Recently, by applying nanotechnology, the use of diatom frustules as nanobiomaterials has been intensively proposed by several pioneer researchers. [10][11][12][13][14][15][16][17] To obtain excellent results, purified frustules are used instead of diatomite, because a detailed characterization of the structures and physical-chemical properties of the frustules is necessary. Anderson et al 10 made pioneering efforts in this field; they functionalized frustule surfaces by annealing the frustules with zeolite nanoparticles at 175 C. In 2007, Bao et al 16 proposed a new NO x sensor using a single frustule; in these experiments, they annealed purified frustules at 650 C in the presence of magnesium in order to convert SiO 2 into Si.…”

“…In the past, we proposed new methods for nanoscopic characterization of diatoms. [17][18][19] For example, we proposed a method for culturing adhesive diatoms on self-assembled monolayers (SAMs) prepared on a mica or glass surface. 18 Cells of Navicula sp.…”

Diatom Cells Grown and Baked on a Functionalized Mica Surface

“…Recently, several research groups have focused on combining frustules and nanotechnology [12][13][14][15][16][17][18][19]. A typical example of diatom nanotechnology is the preparation of replicas of the nanoporous structures of frustules.…”