Supporting information: 1. Lewis acid-base theory (Pearson HSAB classification) The general approach for studying the coordination bonds is with Hard Soft Acid Base theory (Pearson HSAB) 1. In this theory, metals and ligands can be classified as acid and base, and then the theory can be applied to metal and ligands reaction. In general, hard-hard and soft-soft interactions are most preferred energetically. The group electronegativity of surfactant is determined not only by the central atoms but also by the connecting atoms as shown in the drawing. In fact, the connecting atoms can strongly affect the properties of the functional groups. The general equation1 for group electronegativity considers these two aspects. χg = (Vc* χc +sum of Ni *χi)/N Where Vc and χc are the valence of central atom and its atomic electronegativity value, Ni is the bond number of atom i, and χi is the electronegativity of atom i ; N is the sum of the valence of the central atom and all the atoms directly connected to the central atom. Base on this equation, values for some surfactants are calculated as shown in Table 1. elements O N P H χi (ev) 3.44 3.04 2.19 2.02 groups -COOH -NH2 >NH χg (ev) 2.88 2.63 2.82 2.80 Table 1 Group electronegativity data of some common elements and surfactants used in the synthesis The ligand-metal interaction could be rationalized qualitatively by this HSAB theory. The calculated data suggest that –COOH (high electronegativity) group binds stronger than other groups. TOPO binding ability is slightly higher than Di-amines based on their electronegativity. The total reactivity of the surfactants is also dependent on the surfactant chain characteristic. The longer and the more bulky the chain, the less the reactivity is. For example, TOPO and DOA have similar binding strength, but TOPO is less reactive due to the bulky tail. So the monomer complex is less reactive. 1. J.E. Huheey, Inorganic Chemistry; HARPER & Row: New York 1983. 2.X-ray diffraction Jade software simulation results Profile Fitting Report Residual Error of Fit = 20.40%, Total Area = 29881 (815), Crystallinity = ? @ 2- Theta d(nm) Centroid Height Area(a1) Area% Shape Skew FWHM Breadth XS(nm) 44.567 0.20314 1221 15215 0.526 (0.017) (0.00015) 44.572 (33) (565) 100 2.340p -0.044 (0.018) 0.623 12(2) 47.151 0.19259 652 9713 0.523 (0.020) (0.00016) 47.13 (26) (460) 63.8 1.128p 0.164 (0.028) 0.745 13(2) 49.626 0.18355 305 3998 0.580 (0.033) (0.00023) 49.562 (17) (311) 26.3 3.513p 0.423 (0.039) 0.655 12(2) 56.488 0.16277 955 0.614 (0.094) (0.00050) 56.438 71 (9) (193) 6.3 4.000p 0.318 (0.106) 0.673 12(4) 1. Jade software simulations and results for single crystalline cobalt nanoparticles Profile Fitting Report Residual Error of Fit = 17.27%, Total Area = 34116 (2223), Crystallinity = ? @ 2- Theta d(nm) Centroid Height Area(a1) Area% Shape Skew FWHM Breadth XS(nm) 49.489 0.18402 106 7494 1.644 (0.156) (0.00109) 49.775 (19) (1633) 46.7 0.510p -0.619 (0.707) 3.535 5 (3) 44.774 0.20225 417 16053 1.484 (0.052) (0.00045) 44.601 (21) (1118) 100 1.438p 0.442 (0.111) 1.925 5 (2) 47.185 0.19246 219 9174 1.609 (0.100) (0.00077) 47.155 (20) (905) 57.1 1.370p 0.076 (0.144) 2.095 5 (2) 56.241 0.16343 1395 1.794 (0.249) (0.00133) 56.803 28 (6) (455) 8.7 0.500p -0.9 (0.682) 2.491 5 (3) 2. Jade software simulations and results for multiple grained cobalt nanoparticles .