Fig. 5
From: Effect of Mn2+ concentration on the growth of δ-MnO2 crystals under acidic conditions
TEM images of δ-MnO2 react with 25 mM Mn2+ at pH 2.5 about 1 h (a and b), and 1 d (c and d). The red line and circles represent hexagonal δ-MnO2 nanoflakes in image b. The yellow dashed lines within the red rectangular area show the assembly of several δ-MnO2 nanoflakes into nanoribbons in image d