Biomimetic Synthesis of Nacrelike Faceted Mesocrystals of ZnO−Gelatin Composite

Abstract

A fabrication of ZnO hierarchical mesocrystal was achieved by a biomimetic method using gelatin as structure-directing agent. It was found that the ZnO−gelatin microcrystal with well-defined hexagonal twin plate shape is built by the stacking of nanoplates. The irregularly edged nanoplates can adjust themselves to each other throughout the microcrystal, resulting in a roughly hexagonal edge. Selected area electron diffraction (SAED) analysis of the ZnO−gelatin microcrystal demonstrates that all the stacked nanoplates are aligned and oriented to form a single-crystal structure with hexagonal symmetry. The hierarchical structure of ZnO was found to resemble that of naturally occurring nacre. Similar to nacreous architecture, the nanoplate of ZnO was constructed from the oriented attachment of ZnO nanoparticles. More importantly, the lattices of the stacked nanoplates are aligned through mineral bridges between neighboring plates. A mechanism scheme is proposed for the formation of the gelatin−ZnO hybrid hierarchical structure. The preserved hexagonal shape of the mesocrystal structure consequently results in a whispering gallery mode (WGM) of optical emission where light was confined in the hexagons by total internal reflection. The observation of WGM mode emission in the ZnO hexagon structure shows promises for nanoscale fabrication of optoelectronic devices.

Poriferan Chitin as a Versatile Template for Extreme Biomimetics

“…These biomacromolecules play an important role in nucleation, thermodynamic and kinetic control of crystal growth, and also can be used as soft templates for inorganic structures [143]. However, traditionally, approaches related to the in vitro biomimetic mineralization of organic templates are carried out at temperatures between 20 and 37 °C and at near-neutral pH [149][150][151][152][153][154][155][156][157][158]. It is assumed that biological materials, especially protein-based ones, are not stable at temperatures higher than 40 °C.…”

Reversed Crystal Growth of Calcite in Naturally Occurring Travertine Crust

“…For example, crystals of CaCO 3 [18][19][20][21][22][23][24], ZnO [25][26][27][28], and fluorapatite [29,30] have been grown in gel matrices or in the presence of polymers such as gelatin, chitosan, gum arabic and agarose. During the preparation process, these structure directing agents may play the role of a template and a surfactant.…”

Direct evidence of ZnO morphology modification via the selective adsorption of ZnO-binding peptides

“…The most commonly used approach is that involving SDAs ranging from simple molecules, such as amines [13][14][15][16] and anionic species, [17][18][19][20][21] to polymers (DBCP, [22][23][24][25][26][27][28][29] PVP, [30][31][32][33][34][35][36][37][38][39][40][41][42] PAM, 29 and PAH 43 ) and biomolecules. [44][45][46][47][48][49][50][51][52] The SDAs have been shown to affect the morphology of ZnO by imposition of effects on nucleation and/or growth of the crystals. Among these SDAs, biomolecules have received little attention in ZnO synthesis because of their complexity, high cost, and sensitivity to reaction conditions.…”

“…The first is the potential of biomolecules to direct ZnO formation under mild reaction conditions. 53,54 Secondly, some biomoleculedirected syntheses have been shown to impose exquisite control on ZnO morphology/structure; [44][45][46]48,50,51,55 improve ZnO crystallinity; 50 template ZnO formation; 47,49,52,56 catalyze ZnO formation; 57,58 and also suppress ZnO formation. 44,45 These diverse effects can possibly be used to tune the morphology/ structure-related properties of ZnO and thus its applications.…”