Morphology‐controlled Synthesis of SiO₂ Hierarchical Structures Using Pollen Grains as Templates

Abstract

Rape-, sweet potato-and camellia-pollen-templated SiO 2 hierarchical structures with species-specific surface morphologies were prepared through a facile surface sol-gel and succedent calcination process. Various-morphology SiO 2 replicas with complex structures, such as about 50-µm-length and 20-µm-width high-fidelity ellipsoidal replicas with about 5-µm uniform meshes, about 40-µm spheres with 2-µm taper-like protuberances and 15-µm spheres with troughs, were obtained from using rape-, sweet potato-and camellia pollen grains as templates, respectively. The results of N 2 adsorption-desorption isotherms indicate that both rape-and camellia-pollentemplated SiO 2 replicas show type IV-like isotherm with the characteristics of mesoporosity and corresponding Brunauer-Emmett-Teller (BET) surface areas are 10.5 and 5.2 m 2 •g -1 , respectively. The Barrett-Joyner-Halenda (BJH) pore size distribution of the rape-pollen-templated SiO 2 replicas presents smaller pores centered at 3.6 nm and bigger pores centered at 8.6 nm with a broad distribution whereas the camelliapollen-templated SiO 2 replicas display narrow BJH pore size distribution centered at 20 nm. The biofabrication procedure using ubiquitous, inexpensive and environment-friendly pollen grains as a biotemplate holds a promise as a simple route to construct controlled complex porous oxides via simple chemical methods.

Recent Applications of Ionic Liquids in the Sol-Gel Process for Polymer–Silica Nanocomposites with Ionic Interfaces

“…Thin films, porous materials or bulk structures are just examples that can be used as adsorbents or separation materials, catalysts or sensors. Many modeling (templating) techniques are discussed in the literature, using a broad variety of solvents, surfactants [71,72], even natural products ( Figure 3) [73]. Moreover, the effect of these molecules into the sol-gel development is so intrinsic that the final gel will inherit the natural ordering of entrapped molecules.…”

“…Molecular imprinted materials and their surface structure diversity. SEM images of (a) camellia and (b) rapeseed pollens (top) with their molecular impressions (bottom) [73] (permission obtained for reproduction); (c) chiral helical structure formed by a chiral low molecular weight gelators as templates [76] (Reprinted from Ref. [76] with permission of The Royal Society of Chemistry.)…”

Hollow Pollen Shells to Enhance Drug Delivery

“…All the particles from a single species of plant have the same size and decorations, for example Lycopodium clavatum particles shown in Figure 1 . This morphology was regarded as being so applicable to drug delivery that artificial pollen particles have been produced using silica [ 1 , 2 ], calcium carbonate or calcium phosphate [ 3 ], and iron oxide [ 4 ], but these particles lack the elasticity of exines extracted from plant pollen and spores and are difficult to make free from defects. It is possible to attach drugs to the outside of complete particles, but the loading is restricted and the drug receives little protection and its release is relatively uncontrolled.…”

Biotemplate synthesis of monodispersed iron phosphate hollow microspheres

“…So the utilization of natural materials is not only an efficient way to create materials with the desired structures and properties, but also an eco-friendly solution to answer increasingly pressing resource depletion [1]. In recent years, plenty of natural structures at multiple scales ranging from nano (proteins [2,3], bacteria [4] and viruses [5,6]), micro (insect wings [7,8], pollen grains [9,10] and diatoms [11]) to macro (wood [12,13], egg shell membranes [14]) have 1 Author to whom any correspondence should be addressed.…”