The relationship between the morphology and the concentration of the two building blocks was also evaluated (Figure ). In these experiments, the metal salt-to-ligand molar ratio of 2:1 was kept constant. However, the concentrations of both NiCl2 (1.2 mM) and CSB (0.6 mM) were varied by a factor of 2, 1.35, 0.7, and 0.25. The highest concentration (×2) resulted in large plates as the major product and hedrites (16.8 ± 2.5 μm) as a minor product (Figure ). The branches are relatively thin and less prominent. Such structures are known to be precursors for the formation of sheafs. The concentration of ×1.35 resulted in the formation of well-defined sheaf-like crystals (9.5 ± 1.6 μm) with the free bridge having a length of 3.4 ± 0.5 μm and a width of 2.6 ± 0.4 μm. Along with sheaf-like structures, nanorods were observed as a minor product (Figure ). Decreasing the concentrations to ×0.7 generated plates (37.6 ± 5.8 μm) having a layered surface texture and larger structures (51.4 ± 6.2 μm) that resemble half of the sheafs (Figure ). Some of these latter structures have hollow tubular sub-units. Further decreasing the concentrations to ×0.25 resulted in smooth plates (55.8 ± 7.2 μm) (Figure ). The structures formed under the abovementioned different reaction conditions (concentration and metal salt-to-ligand ratio) have similar homogeneous elemental compositions (EDS-SEM) and Nipyridine coordination chemistry (XPS) (Figure ). All structures have a metal cation-to-ligand ratio of 2:1, therefore all the reaction solutions contained excess of the metal salt but in different concentrations. The metal cations modulate the crystal morphology, dimensions and their uniformity.