Role of Organic and Inorganic Additives on the Assembly of CTAB-P123 and the Morphology of Mesoporous Silica Particles

Abstract

Mesoporous silica particles with various morphologies and structures have been synthesized by controlling the solubility, micellization, and assembly of a charged surfactant (cethyltrimethylammonium bromide, CTAB) and a pluronic (PEO 20 PPO 70 PEO 20 , P123) couple using an organic (benzene) or an inorganic (SO 4 2-, NO 3 -, or Cl -) additive. The effect of CTAB, with or without one of the Hofmeister ions or benzene in various concentrations, on the morphology, pore-size, pore-structure and the nature of the silica particles has been investigated. Increasing the lyotropic anion (SO 4 2-) or benzene concentration of the synthesis media creates wormlike particles with enlarged pores and reduced wall thickness. However, the hydrotropic anion (NO 3 -) influenced the solubility of the charged surfactant and increased the CTAB concentration in the CTAB-P123 micelles, and as a result, in the mesoporous silica particles. The surface area, unit cell, and pore size of the silica particles are diminished by increasing the nitrate ion centration. The effects of the Cl -ion are between the SO 4 2-and NO 3 -ions. It influenced the P123 at low and CTAB at high concentrations. At low CTAB/ P123 mol ratios, the Cl -ion affects mainly the P123, but at high CTAB/P123 it affects both the CTAB and P123. By carefully adjusting these ingredients (CTAB, SO 4 2-, Cl -, NO 3 -and benzene), not only the morphology of the particles, but also the pore-size and pore-structure of the mesoporous silica particles could be adjusted. The investigations were carried out by preparing a series of powder samples and, by varying the CTAB/P123 mol ratio (between 3.0 and 6.0) and the concentration of the organic (0.17 to 0.90 M) or inorganic (at 0.25, 0.50, or 1.00 M) additive in the synthesis media. The powder samples were analyzed using microscopy (SEM, TEM, and POM), diffraction (PXRD), and spectroscopy (FTIR, Raman, UV-vis, and EDS) techniques toward above goals.

ZnS porous fluorescent nanostructures synthesized by a soft template approach

“…The frames play roles in supporting the porous space, preventing the collapse of the structures. The weak peaks at 2920 and 2850 cm -1 that appear in both ZnS precursors before and after Soxhlet extraction are vibrational modes of CH and symmetric m-CH stretching [36]. These peaks did not appear in sample III, since Soxhlet extraction could not remove the organic templates completely, but calcinations could thermally decompose all of the organic substances.…”

A general approach to crystalline and monomodal pore size mesoporous materials

“…An interface modifier such as 1-butanol (for both polyethylene oxide (PEO) and polypropylene oxide (PPO)) compensates for the decrease of the aggregation number, hinders the condensation by forming a physical barrier between the oxo-clusters and limits oxidation of surfactant molecules (by TM clusters) present in the micelle. The hydrotropic nitrate ion increases solubility of P123, penetrates into the micelle and decreases the aggregation number, pulls the positively charged metal oxide clusters into the micelle and hydrates the core 21 . The existence of NO 3 À ions in the developed method is essential and such ions have multiple roles.…”

Mesoporous silica SBA-15 sheet with perpendicular nanochannels

“…For R = 1.80 and 2.0, the two profiles show type IV isotherms with H 1 -H 2 hysteresis loops. The two-step capillary evaporation of H 1 -H 2 hysteresis loop suggests the coexistence of cylindrical and cage-like pore structure [37][38][39]. With increasing R, the content of cage-like mesostructure increases.…”