  This study examines the anisotropic dissolution of the basal plane gibbsite
({\gamma}-Al(OH)3) nanoplates in sodium hydroxide solution using in situ atomic
force microscopy (AFM) and density functional theory (DFT) calculations. In the
surface-reaction controlled regime, in situ AFM measurements reveal anisotropic
dissolution of hillocks and etch pits on the gibbsite basal plane, with
preferred dissolution directions alternating between layers. The
mirror-symmetric pattern of dissolution preference between adjacent gibbsite
aluminum hydroxide sheet, observed along the crystallographic a-c plane,
results from the matching symmetry between the structures of the adjacent (001)
and (002) crystal planes. Consequently, the overall dissolution rate of
gibbsite nanoplates exhibits crystallographic a-c plane symmetry, as the rate
of parallel steps is governed by the slower ones. DFT calculations suggest that
the anisotropic dissolution is partially due to the orientation and strength of
Al-OH-Al linkages pair within gibbsite surface structure. These findings offer
a comprehensive understanding of anisotropic dissolution behavior of gibbsite
and illuminate the mechanisms behind preferential dissolution.
