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A combination of hard and soft templating for the fabrication of silica hollow microcoils with nanostructured walls.

Rodriguez-Abreu C, Vilanova N, Solans C, Ujihara M, Imae T, López-Quintela A, Motojima S - Nanoscale Res Lett (2011)

Bottom Line: Moreover, they have mesoporous walls (pore size ≈ 3 nm) with some domains where pores are ordered in a hexagonal array, originated from surfactant micelles.The obtained silica microcoils also show preferential adsorption of cationic fluorescent dyes.A mechanism for the formation of silica microcoils is proposed.

View Article: PubMed Central - HTML - PubMed

Affiliation: International Iberian Nanotechnology Laboratory (INL), Av, Mestre José Veiga, Braga, 4715-310, Portugal. crodriguez@inl.int.

ABSTRACT
Hollow silica microcoils have been prepared by using functionalized carbon microcoils as hard templates and surfactant or amphiphilic dye aggregates as soft templates. The obtained materials have been characterized by electron and optical microscopy, nitrogen sorption and small angle X-ray scattering. The obtained hollow microcoils resemble the original hard templates in shape and size. Moreover, they have mesoporous walls (pore size ≈ 3 nm) with some domains where pores are ordered in a hexagonal array, originated from surfactant micelles. The obtained silica microcoils also show preferential adsorption of cationic fluorescent dyes. A mechanism for the formation of silica microcoils is proposed.

No MeSH data available.


Related in: MedlinePlus

Silica microcoils prepared using PDI. (a) Molecular structure of PDI. (b) SEM image of silica microcoils at PDI/CMC-COOH ratio = 3; the arrows indicate elongated particles adhered to the coils. (c, d) SEM image of silica microcoils at PDI/CMC-COOH ratio = 0.2. The other initial weight ratios for the silica coating process were NH3(aq.)/CMC-COOH/TEOS = 300/0.37/10.1.
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Figure 5: Silica microcoils prepared using PDI. (a) Molecular structure of PDI. (b) SEM image of silica microcoils at PDI/CMC-COOH ratio = 3; the arrows indicate elongated particles adhered to the coils. (c, d) SEM image of silica microcoils at PDI/CMC-COOH ratio = 0.2. The other initial weight ratios for the silica coating process were NH3(aq.)/CMC-COOH/TEOS = 300/0.37/10.1.

Mentions: We also found that PDI (see Figure 5a), which is known to self-assemble in water [17], can be used as a soft template for the silica coating of CMC-COOHs. PDI has n-type semiconductor properties, with possible applications in organic field effect transistors and photovoltaics. Moreover, PDI molecules adsorb strongly to the CMC-COOH surface, as confirmed by UV-vis spectroscopy (see Figure S3 in Additional file 1). In the absence of CMC-COOH, PDI induces the formation of elongated silica particles in the sol-gel reaction mixture, which is attributed to the templating effect of cylindrical self-assemblies of the dye in solution [17]. At high PDI/CMC-COOH ratios, those elongated silica particles, precipitated from the solution, coat the surface of CMC-COOHs (see Figure 5b). When the TEOS/CMC-COOH ratio is decreased, hollow silica microcoils with smoother surface are obtained, suggesting that silica formation on the CMC-COOH surface is favoured over that occurring in the bulk solution (see Figure 5c,d). The yield of silica microcoils relative to amorphous silica also increases when the PDI/CMC-COOH ratios are decreased. It is to be noted here that when PDI is used as template, the walls of silica coils are probably microporous rather than mesoporous as suggested by preliminary nitrogen sorption measurements, which gave isotherms with features typical of microporous solids.


A combination of hard and soft templating for the fabrication of silica hollow microcoils with nanostructured walls.

Rodriguez-Abreu C, Vilanova N, Solans C, Ujihara M, Imae T, López-Quintela A, Motojima S - Nanoscale Res Lett (2011)

Silica microcoils prepared using PDI. (a) Molecular structure of PDI. (b) SEM image of silica microcoils at PDI/CMC-COOH ratio = 3; the arrows indicate elongated particles adhered to the coils. (c, d) SEM image of silica microcoils at PDI/CMC-COOH ratio = 0.2. The other initial weight ratios for the silica coating process were NH3(aq.)/CMC-COOH/TEOS = 300/0.37/10.1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211418&req=5

Figure 5: Silica microcoils prepared using PDI. (a) Molecular structure of PDI. (b) SEM image of silica microcoils at PDI/CMC-COOH ratio = 3; the arrows indicate elongated particles adhered to the coils. (c, d) SEM image of silica microcoils at PDI/CMC-COOH ratio = 0.2. The other initial weight ratios for the silica coating process were NH3(aq.)/CMC-COOH/TEOS = 300/0.37/10.1.
Mentions: We also found that PDI (see Figure 5a), which is known to self-assemble in water [17], can be used as a soft template for the silica coating of CMC-COOHs. PDI has n-type semiconductor properties, with possible applications in organic field effect transistors and photovoltaics. Moreover, PDI molecules adsorb strongly to the CMC-COOH surface, as confirmed by UV-vis spectroscopy (see Figure S3 in Additional file 1). In the absence of CMC-COOH, PDI induces the formation of elongated silica particles in the sol-gel reaction mixture, which is attributed to the templating effect of cylindrical self-assemblies of the dye in solution [17]. At high PDI/CMC-COOH ratios, those elongated silica particles, precipitated from the solution, coat the surface of CMC-COOHs (see Figure 5b). When the TEOS/CMC-COOH ratio is decreased, hollow silica microcoils with smoother surface are obtained, suggesting that silica formation on the CMC-COOH surface is favoured over that occurring in the bulk solution (see Figure 5c,d). The yield of silica microcoils relative to amorphous silica also increases when the PDI/CMC-COOH ratios are decreased. It is to be noted here that when PDI is used as template, the walls of silica coils are probably microporous rather than mesoporous as suggested by preliminary nitrogen sorption measurements, which gave isotherms with features typical of microporous solids.

Bottom Line: Moreover, they have mesoporous walls (pore size ≈ 3 nm) with some domains where pores are ordered in a hexagonal array, originated from surfactant micelles.The obtained silica microcoils also show preferential adsorption of cationic fluorescent dyes.A mechanism for the formation of silica microcoils is proposed.

View Article: PubMed Central - HTML - PubMed

Affiliation: International Iberian Nanotechnology Laboratory (INL), Av, Mestre José Veiga, Braga, 4715-310, Portugal. crodriguez@inl.int.

ABSTRACT
Hollow silica microcoils have been prepared by using functionalized carbon microcoils as hard templates and surfactant or amphiphilic dye aggregates as soft templates. The obtained materials have been characterized by electron and optical microscopy, nitrogen sorption and small angle X-ray scattering. The obtained hollow microcoils resemble the original hard templates in shape and size. Moreover, they have mesoporous walls (pore size ≈ 3 nm) with some domains where pores are ordered in a hexagonal array, originated from surfactant micelles. The obtained silica microcoils also show preferential adsorption of cationic fluorescent dyes. A mechanism for the formation of silica microcoils is proposed.

No MeSH data available.


Related in: MedlinePlus