Unidirectional crystallization of charged colloidal silica due to the diffusion of a base.
Dilute aqueous dispersions of charged colloidal silica (particle volume fraction = approximately 0.03-0.04, particle diameter = 110 nm) exhibit unidirectional crystal growth due to the diffusion of a weak base, pyridine (Py). Similar diffusion-crystallization is enabled by a salt of a weak acid and a strong base, sodium hydrogen carbonate (NaHCO3). The resulting crystals consist of columnar (or cubic) crystal grains with a maximum height of a few centimeters and a maximum width of 1 cm. The crystal growth process is attributed to a combination of (i) the diffusion of Py or NaHCO3 accompanied by a charging reaction of the silica particles and (ii) the charge-induced crystallization of the silica colloids. Theoretical growth curves based on the reaction-diffusion model for the case of Py were in good agreement with the observed curves. We also report the immobilization of the resulting large crystals by using a polymer hydrogel matrix.
Murai
Masako
M
Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603, Japan.
Yamada
Hiroshi
H
Yamanaka
Junpei
J
Onda
Sachiko
S
Yonese
Masakatsu
M
Ito
Kensaku
K
Sawada
Tsutomu
T
Uchida
Fumio
F
Ohki
Yoshimasa
Y
D000327:Adsorption; D003102:Colloids / Q000737:chemistry*; D003460:Crystallization; D004058:Diffusion; D020100:Hydrogels / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology; D010316:Particle Size; D011725:Pyridines / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D017693:Sodium Bicarbonate / Q000737:chemistry; D055672:Static Electricity; D014961:X-Ray Diffraction
D003102:Colloids; D020100:Hydrogels; D011725:Pyridines; D012822:Silicon Dioxide; D017693:Sodium Bicarbonate