Lipid-bilayer coated nanosized bimodal mesoporous carbon spheres for controlled release applications

Highly mesoporous nanosized carbon spheres (MCS) equipped with an active lipid bilayer demonstrate pronounced molecular release behavior, and excellent potential for drug delivery applications. We report a facile synthesis route for the creation of colloidal MCS with a bimodal pore size distribution, featuring a high BET surface area combined with high pore volume. Bimodal mesoporosity was achieved by a simultaneous co-assembly of a polymer resin (resol), tetraethyl orthosilicate (TEOS) and a block copolymer (Pluronic F127). The spherical geometry originates from casting the precursor mixture into a macroporous silica hard template, having a mean pore size of 60 nm, followed by thermopolymerization and final carbonization at 900 °C in nitrogen atmosphere. The final bimodal mesoporous MCS were obtained after removal of inorganic compounds by etching with hydrofluoric acid. Colloidal suspensions of MCS were prepared by oxidation with ammonium persulfate. MCS were loaded with calcein as a model drug. Efficient sealing of the MCS was achieved with a supported lipid bilayer (SLB). The SLB acts as a diffusion barrier against the uncontrolled release of encapsulated dye molecules until the release is triggered via the addition of a surface active agent. The high surface area and pore volume and the excellent release characteristics make the SLB-coated MCS a promising release-on-demand system

Lipid-bilayer coated nanosized bimodal mesoporous carbon spheres for controlled release applications

Highly mesoporous nanosized carbon spheres (MCS) equipped with an active lipid bilayer demonstrate pronounced molecular release behavior, and excellent potential for drug delivery applications. We report a facile synthesis route for the creation of colloidal MCS with a bimodal pore size distribution, featuring a high BET surface area combined with high pore volume. Bimodal mesoporosity was achieved by a simultaneous co-assembly of a polymer resin (resol), tetraethyl orthosilicate (TEOS) and a block copolymer (Pluronic F127). The spherical geometry originates from casting the precursor mixture into a macroporous silica hard template, having a mean pore size of 60 nm, followed by thermopolymerization and final carbonization at 900 °C in nitrogen atmosphere. The final bimodal mesoporous MCS were obtained after removal of inorganic compounds by etching with hydrofluoric acid. Colloidal suspensions of MCS were prepared by oxidation with ammonium persulfate. MCS were loaded with calcein as a model drug. Efficient sealing of the MCS was achieved with a supported lipid bilayer (SLB). The SLB acts as a diffusion barrier against the uncontrolled release of encapsulated dye molecules until the release is triggered via the addition of a surface active agent. The high surface area and pore volume and the excellent release characteristics make the SLB-coated MCS a promising release-on-demand system

Tuning the crystallinity parameters in macroporous titania films

Although macroporous titania scaffolds are used for many different applications, not much is known about the importance of the synthesis strategy on the resulting materials' properties. We present a comparative study on the influence of different colloidal titania precursors for direct co-deposition with poly(methyl methacrylate) (PMMA) beads on the properties of the resulting macroporous scaffolds after calcination. The colloidal titania precursors for the film assembly differ in their size and initial crystallinity, ranging from amorphous sol-gel clusters to already crystalline pre-formed particles of 4 nm, 6 nm and 20 nm in size, as well as a combination of sol-gel and nanoparticle precursors in the so-called `Brick and Mortar' approach. The type of the precursor greatly influences the morphology, texture and the specific crystallinity parameters of the macroporous titania scaffolds after calcination such as the size of the crystalline domains, packing density of the crystallites in the macroporous walls and interconnectivity between the crystals. Moreover, the texture and the crystallinity of the films can be tuned by postsynthesis processing of the films such as calcination at different temperatures, which can be also preceded by a hydrothermal treatment. The ability to adjust the porosity, the total surface area and the crystallinity parameters of the crystalline macroporous films by selecting suitable precursors and by applying different post-synthetic treatments provides useful tools to optimize the film properties for different applications

Tuning the crystallinity parameters in macroporous titania films

Although macroporous titania scaffolds are used for many different applications, not much is known about the importance of the synthesis strategy on the resulting materials' properties. We present a comparative study on the influence of different colloidal titania precursors for direct co-deposition with poly(methyl methacrylate) (PMMA) beads on the properties of the resulting macroporous scaffolds after calcination. The colloidal titania precursors for the film assembly differ in their size and initial crystallinity, ranging from amorphous sol-gel clusters to already crystalline pre-formed particles of 4 nm, 6 nm and 20 nm in size, as well as a combination of sol-gel and nanoparticle precursors in the so-called `Brick and Mortar' approach. The type of the precursor greatly influences the morphology, texture and the specific crystallinity parameters of the macroporous titania scaffolds after calcination such as the size of the crystalline domains, packing density of the crystallites in the macroporous walls and interconnectivity between the crystals. Moreover, the texture and the crystallinity of the films can be tuned by postsynthesis processing of the films such as calcination at different temperatures, which can be also preceded by a hydrothermal treatment. The ability to adjust the porosity, the total surface area and the crystallinity parameters of the crystalline macroporous films by selecting suitable precursors and by applying different post-synthetic treatments provides useful tools to optimize the film properties for different applications

Spherical Ordered Mesoporous Carbon Nanoparticles with High Porosity for Lithium-Sulfur Batteries

Superior cathode material: Spherical ordered mesoporous carbon nanoparticles featuring very high inner porosity (pore volume of 2.32 cm 3 g -1 and surface area of 2445 m 2 g -1) were synthesized in a two-step casting process. They were successfully applied as cathode material in Li-S batteries, where they showed high reversible capacity up to 1200 mA h g -1 and excellent cycling efficiency.close25618

Bimodal Mesoporous Carbon Nanofibers with High Porosity: Freestanding and Embedded in Membranes for Lithium–Sulfur Batteries

We demonstrate a synthetic approach for highly ordered hexagonal mesoporous carbon nanofibers with bimodal porosity, with an extremely high surface area and a high inner pore volume of 1928 m²/g and 2.41 cm³/g, respectively. A tubular silica template acts as an alternative fiber template for anodic alumina membranes. The sulfur cathode fabricated with the nanofibers shows much better electrochemical performance compared with our previously reported BMC-1/S cathodes by achieving a more homogeneous sulfur distribution in the carbon nanofiber framework. It is also noted that the variation of porous architectures of the carbon framework (i.e., low volumetric ratio of small mesopores over the total pore volume) results in very different electrochemistry, suggesting the significance of porosity optimization for sulfur electrodes

Electron Collection in Host–Guest Nanostructured Hematite Photoanodes for Water Splitting: The Influence of Scaffold Doping Density

Nanostructuring has proven to be a successful strategy in overcoming the trade-off between light absorption and hole transport to the solid/electrolyte interface in hematite photoanodes for water splitting. The suggestion that poor electron (majority carrier) collection hinders the performance of nanostructured hematite electrodes has led to the emergence of host–guest architectures in which the absorber layer is deposited onto a transparent high-surface-area electron collector. To date, however, state of the art nanostructured hematite electrodes still outperform their host–guest counterparts, and a quantitative evaluation of the benefits of the host–guest architecture is still lacking. In this paper, we examine the impact of host–guest architectures by comparing nanostructured tin-doped hematite electrodes with hematite nanoparticle layers coated onto two types of conducting macroporous SnO₂ scaffolds. Analysis of the external quantum efficiency spectra for substrate (SI) and electrolyte side (EI) illumination reveals that the electron diffusion length in the host–guest electrodes based on an undoped SnO₂ scaffold is increased substantially relative to the nanostructured hematite electrode without a supporting scaffold. Nevertheless, electron collection is still incomplete for EI illumination. By contrast, an electron collection efficiency of 100% is achieved by fabricating the scaffold using antimony-doped SnO₂, showing that the scaffold conductivity is crucial for the device performance