Biological Fabrication of Photoluminescent Nanocomb Structures by Metabolic Incorporation of Germanium into the Biosilica of the Diatom Nitzschia frustulum

Abstract

Diatoms are single-celled algae that make microscale silica shells or "frustules" with intricate nanoscale features such as two-dimensional pore arrays. In this study, the metabolic insertion of low levels of germanium into the frustule biosilica of the pennate diatom Nitzschia frustulum by a two-stage cultivation process induced the formation of frustules which strongly resembled double-sided nanocomb structures. The final product from the two-stage cultivation process contained 0.41 wt % Ge in biosilica and consisted of an equal mixture of parent frustule valves possessing a normal two-dimensional array of 200 nm pores and daughter valves possessing the nanocomb structure. The nanocomb structures had overall length of 8 mum, rib width of 200 nm, rib length of 500 nm, and slit width of 100 nm. Each slit of the nanocomb was most likely formed by a directed morphology change of a row of 200 nm pores to a single open slit following Ge incorporation into the developing frustule during the final cell division. The frustules possessed blue photoluminescence at peak wavelengths between 450 and 480 nm, which was attributed to contributions from nanostructured biosilica in both the parent valves and in the nanocomb daughter valves. This is the first reported study of using a cell culture system to biologically fabricate a photoluminescent nanocomb structure.

Diatomaceous Lessons in Nanotechnology and Advanced Materials

“…For example, including germanic acid in the culture medium allowed the biosynthesis of silicon-germanium oxide nanocomposites in the frustules of the marine diatom Nitzschia frustlulum. [62,63] Germanium is of particular interest, since nanostructured silicon-germanium composite materials exhibit characteristic semiconducting and optoelectronic properties The introduction of metal ions, such as nickel, during diatom culture imparts control over pore morphology. [31,64a] The ability to control pore size and morphology in addition to chemical composition within a given species bestows the potential to tailor structural, photonic, absorptive, diffusive, and mechanical properties of diatom frustules to suit particular applications.…”

“…Recent results indicate that the electroluminescence and photoluminiscence of diatom biosilica can be fine-tuned by metabolically incorporating germanium, which may allow researchers to tailor the luminescence properties to the desired sensor applications. [63,66] Diatoms converted into semiconducting ceramics of TiO 2 , GeO 2 , ZrO 2 , or SnO 2 by BaSIC, sol-gel chemistry, hydrothermal conversion, or bioengineering show promise for gas-sensing applications, but paths for manipulation and connection of electronics did not exist. However, a microporous silicon structure produced from diatom biosilica was recently connected to platinum wires into an impedance-based sensor for nitric oxide detection with 1 ppm sensitivity.…”

Photoluminescence Detection of Biomolecules by Antibody‐Functionalized Diatom Biosilica

“…Furthermore, nanostructured diatom biosilica exhibits blue PL, which can be controlled through cell cultivation. [21][22][23] The intrinsic PL properties of bare diatom biosilica have already been harnessed for gas sensing applications, [24][25][26][27] but not for biosensing.…”

Hierarchical Assembly

“…In this issue, several articles and features touch on this topic from different points of view. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] In our Conversation, Prof. Ned Seeman discusses structural DNA nanotechnology, a field that he has developed by working out the associations between strands of DNA, exploiting some naturally occurring features and inventing related others. 1 You will see how the creative process outstripped our ability to measure these structures and has led to long incubation times and much frustration along the way.…”

“…16 Several papers this month use clever techniques for the proximal placement of dyes and chromophores to sculpted semiconducting materials in order to couple light in or out. [6][7][8] Prof. Steven Buratto and his group take this to the single-and few-molecule level in using the controllable properties of porous Si 17 and sensitive optical methods to probe the interactions of chromophores placed within the pores. 9 Such clever optical techniques give us glimpses into sites thus far inaccessible to imaging methods.…”