Biomimetic chitosan-mediated synthesis in heterogeneous phase of bulk and mesoporous silica nanoparticles

Abstract

Both bulk and mesoporous silica nanoparticles can be obtained in the form of granular aggregates using chitosan flakes as additive under very soft biomimetic reaction conditions.Biomineralization, that is the formation under extremely soft conditions of complex hierarchical inorganic materials by biological systems, is an exciting research field of increasing interest. 1 Indeed, while technological silica production usually requires vigorous conditions at high pH, 2 certain marine organisms and some higher plants are capable of forming silica skeletons under mild temperature and pressure conditions at circumneutral pH. 1,3,4 Such in vivo processes generating intricate silica nano and macro-scale patterns are speciesspecific, presumably encoded in the genome; 5-7 the possibility of controlling them in the laboratory remains a long-term major challenge. Notwithstanding, there have been different biomolecules identified like silicatein, silaffin and polyamines, which can play key roles in the hydrolysis, condensation and aggregation of the silica species. 3,4,8 Silica is widely used in industry, medicine and nanotechnology in a huge variety of forms. 2,7,9 This, coupled with the insufficiency of natural products of adequate purity and the scientific interest, justifies the search for bioinspired synthesis 8,10 leading to new silica-based materials with simple hierarchical structures or, at least, allowing silica production under soft-conditions (low-cost strategies). Then, inspired by nature, a variety of reagents have been added to check in vitro silicification processes in solution. 11,12 These additives, which intend to mimic the active natural molecules, can play different roles: catalysts, aggregation promoting reagents or structural directing agents. Otherwise, silicatein, silaffin and polyamines have been identified as constituents of the axial filaments in sponges and the cell walls in diatoms. 3,8,9 Although this fact strongly suggests that they process silica in the heterogeneous phase, as far as we know, there is no information about in vitro processes carried out under this conditioning (i.e. on the role of solid phase additives).Here we show how using solid flakes of chitosan (a commercial and low-cost biopolymer present in the shells of crustaceans and the cell walls of fungi and yeast, as well as in squid pens) 13 as additive, it is possible to promote silica polymerization and aggregation in the heterogeneous phase at room temperature, neutral pH and silica concentrations as low as those occurring in sea water or inside the diatom frustules. Our procedural approach leads to bulk biosilica nanoparticles or, alternatively, to similar mesoporous architectures when structural directing agents (SDA) are also added.In order to mimic frustule conditions, 6,14 we have performed the reactions in circulating silica solutions on chitosan flakes blocked in a part of the system in order to favour a certain confining effect (see ESIw). Summarized in Table 1 are the main parameters concerning syntheses of some sel...

Preparation and properties of organomineral adsorbent obtained by sol–gel technology

“…Under the acidic conditions employed, the amine group of chitosan is protonated and forms a charged NH 3 ? group which, in turn, is an even better hydrogen bonding partner than an uncharged NH 2 group [29,31]. The scheme of synthesis of chitosan-silica composite by the sol-gel method is presented in Fig.…”

“…Plenty preparation methods of hybrid materials based on inorganic materials and polysaccharides for different applications have been studied [24][25][26][27][28][29][30][31]. Ion-imprinting concept and polysaccharide incorporated sol-gel process were applied to the preparation of a new silica-supported organic-inorganic hybrid sorbent for selective separation of Cd(II) from aqueous solution.…”

Preparation of hierarchical β and Y zeolite-containing mesoporous silica–aluminas and their properties for catalytic cracking of n-dodecane

“…The solid catalysts are a mass of objects for study of the sol-gel method. In recent years, much attention has been focused on the preparation of mesoporous materials [2][3][4][5][6][7][8][9][10], specifically the composite catalysts including micro/mesoporous materials for various reactions [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Zeolite has the high surface area and many strong acid sites, which give a potential for the high adsorption ability or the high activity in the reactions.…”

Preparation of Amorphous Silica-Alumina Using the Sol–Gel Method and its Reactivity for a Matrix in Catalytic Cracking

“…These ligands remain in the inside of the gel formed and change the extent and rate of polymerization, and their size itself also changes the size and diameter of pores formed [4]. These ligands are usually organic compounds such as carboxylic acids, alcohols [5,6], amine and organic polymers such as polyethylene oxide or biopolymer [7][8][9][10][11][12][13][14][15], and serve as not only templates for pore size and shape but also reagents for the dispersion of aluminum species and catalysts at the preparation of silica, alumina and silica-alumina in the sol-gel method.…”