TY - JOUR
T1 - Growth mechanism of dendritic hematite via hydrolysis of ferricyanide
AU - Green, Alice E.
AU - Chiang, Chang Yang
AU - Greer, Heather F.
AU - Waller, Ashleigh
AU - Ruszin, Aron
AU - Webster, James
AU - Niu, Ziyin
AU - Self, Katherine
AU - Zhou, Wuzong
N1 - Copyright:
© 2017 American Chemical Society.
PY - 2017/2/1
Y1 - 2017/2/1
N2 - The detailed process of the hydrolysis of ferricyanide into dendritic α-Fe2O3 (hematite) crystals with snowflake-like, feather-like, and leaf-like morphologies has been investigated. [Fe(CN)6]3- anions were found to polymerize into large, disordered soft matter aggregates at an early stage. The nucleation of hematite crystals took place near the surface of these aggregates via further hydrolysis. After the crystals grew to a certain size, branches started to appear. When the concentration of ferricyanide was low (i.e. 2 mM to 3.8 mM), growth was preferentially along the six equivalent ?1120? directions, resulting in a flat snowflake-like shape, while high concentrations (i.e. 9 mM to 500 mM) of ferricyanide led to the growth of selective directions along the ?1011? zone axes, forming a feather-like or leaf-like morphology. Highly selective adsorption and surface hydrolysis of [Fe(CN)6]3-anions on α-Fe2O3 crystals was found to be a crucial process in the formation of these novel morphologies. It was found that the polymerization of ferricyanide led to a reduction of pH value and that the formation of Fe2O3 increased the pH value. The pH value of the solution at the point when the branches start to grow can significantly affect the distribution of Lewis acidic sites on different surfaces and, therefore, change the growth direction. The newly established mechanism is complementary to the classical theories of crystal growth.
AB - The detailed process of the hydrolysis of ferricyanide into dendritic α-Fe2O3 (hematite) crystals with snowflake-like, feather-like, and leaf-like morphologies has been investigated. [Fe(CN)6]3- anions were found to polymerize into large, disordered soft matter aggregates at an early stage. The nucleation of hematite crystals took place near the surface of these aggregates via further hydrolysis. After the crystals grew to a certain size, branches started to appear. When the concentration of ferricyanide was low (i.e. 2 mM to 3.8 mM), growth was preferentially along the six equivalent ?1120? directions, resulting in a flat snowflake-like shape, while high concentrations (i.e. 9 mM to 500 mM) of ferricyanide led to the growth of selective directions along the ?1011? zone axes, forming a feather-like or leaf-like morphology. Highly selective adsorption and surface hydrolysis of [Fe(CN)6]3-anions on α-Fe2O3 crystals was found to be a crucial process in the formation of these novel morphologies. It was found that the polymerization of ferricyanide led to a reduction of pH value and that the formation of Fe2O3 increased the pH value. The pH value of the solution at the point when the branches start to grow can significantly affect the distribution of Lewis acidic sites on different surfaces and, therefore, change the growth direction. The newly established mechanism is complementary to the classical theories of crystal growth.
UR - http://www.scopus.com/inward/record.url?scp=85011372921&partnerID=8YFLogxK
U2 - 10.1021/acs.cgd.6b01655
DO - 10.1021/acs.cgd.6b01655
M3 - Article
AN - SCOPUS:85011372921
SN - 1528-7483
VL - 17
SP - 800
EP - 808
JO - Crystal Growth and Design
JF - Crystal Growth and Design
IS - 2
ER -