Controlled synthesis and tunable properties of ultrathin silica nanotubes through spontaneous polycondensation on polyamine fibrils

Abstract

SummaryThis paper describes a facile approach to a biomimetic rapid fabrication of ultrathin silica nanotubes with a highly uniform diameter of 10 nm and inner hollow of around 3 nm. The synthesis is carried out through a spontaneous polycondensation of alkoxysilane on polyamine crystalline fibrils that were conveniently produced from the neutralization of a solution of protonated linear polyethyleneimine (LPEI–H+) by alkali compounds. A simple mixing the fibrils with alkoxysilane in aqueous solution allowed for the rapid formation of silica to produce LPEI@silica hybrid nanotubes. These 10-nm nanotubes were hierarchically organized in a mat-like morphology with a typical size of 1–2 micrometers. The subsequent removal of organic LPEI via calcination resulted in silica nanotubes that keep this morphology. The morphology, the structure, the pore properties and the formation mechanism of the silica nanotubes were carefully investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller measurements (BET), and X-ray diffraction (XRD). Detailed studies demonstrated that the formation of the nanotubes depends on the molar ratio of [OH]/[CH2CH2NH] during the neutralization as well as on the basicity of the alkali compound and on the concentration of the silica source. The synthesis of silica nanotubes established here could be easily applied to a fabrication on the kilogram scale. Silica nanotubes that were obtained from the calcination of hybrid nanotubes of LPEI@silica in an N2 atmosphere showed a distinct photoluminescence centered at 540 nm with a maximum excitation wavelength of 320 nm. Furthermore, LPEI@silica hybrid nanotubes were applied to create silica–carbon composite nanotubes by alternative adsorption of ionic polymers and subsequent carbonization.

Anti‐Metastatic and Anti‐Angiogenic Activities of Core–Shell SiO2@LDH Loaded with Etoposide in Non‐Small Cell Lung Cancer

“…In comparison, the SiO 2 @LDH showed a centralized distribution, which corresponds to the hollow inner structure of SiO 2 @LDH. The BET results demonstrated that SiO 2 @LDH has an excellent thermal stability compared to the unmodified SiO 2 26, 27. Besides, based on Table 1, the specific surface area of each nanoparticle was 76.82, 122.06, and 25.65 m 2 g −1 , respectively, which suggests the better loading capacity of SiO 2 @LDH.…”

Preparation of thick silica coatings on carbon fibers with fine-structured silica nanotubes induced by a self-assembly process

“…A considerable number of factors can influence the shape of the primary LPEI aggregates and, consequently, the morphology of the mineralized silica particles. This can be realized by varying the LPEI and/or silica precursor concentration, timespan of silicification [ 19 ], media modulation (i.e., partial replacement of water by methanol or other solvents) [ 20 ], pH value [ 21 ], or by introducing acidic and basic additives that can interact with LPEI [ 22 ] and other proton donors [ 23 ]. Further modification of the silica morphology can be achieved by adding metal ions that form complexes with the secondary amine groups of LPEI [ 24 – 26 ].…”