posted on 2024-01-19, 10:13authored byYandong Han, Wensheng Yang
In
this study, we present a novel modified Stöber method
utilizing cetyltrimethylammonium bromide (CTAB) as a mediator for
the preparation of monodispersed, micron-sized supermicroporous silica
particles. Observed results show prepared silica particles ranging
in size from 0.64 to 1.36 μm with an increase in CTAB concentration
from 1.0 to 5.0 mM. The particles exhibited low polydispersity (<5%),
a high Brunauer–Emmett–Teller surface area (570 to 1064
m2/g), and pore volumes ranging from 0.22 to 0.39 cm3/g. The pore size, determined using the Barrett–Joyner–Halenda
method from the adsorption branches of the isotherms, was approximately
1.9 nm, specifically 1.83, 1.85, and 1.90 nm, as the CTAB concentration
increased from 1.0 to 2.5 and 5.0 mM, respectively. The resulting
particles displayed a narrow distribution of pore diameters. In addition,
to obtain an in-depth understanding of the role of CTAB on the preparation
of silica particles, a possible mechanism is also investigated using
conductivity, dynamic light scattering (DLS), zeta potential, FT-IR
spectra, and transmission electron microscopy. Our findings demonstrate
that CTAB plays multiple roles in the hydrolysis/condensation of TEOS
(tetraethyl orthosilicate) and subsequent nucleation and growth of
silica particles. CTAB acts as a template for superporosity, a stabilizer
for colloids, and an accelerator for nucleation and growth, leading
to formation of monodispersed micrometer silica particles. Further
characterization through FT-IR and 29Si solid NMR spectra
revealed that the micron silica particles were obtained with inhomogeneity
in the condensation degree, allowing for selective etching through
hot incubation to form micron-sized hollow silica spheres.