Effect of reaction temperature
The present investigation reveals that nanoparticles did not synthesize below the temperature 333K in any
conditions. This shows that reaction constant at this temperature is too low to progress the reaction. Therefore
reaction temperature higher than 333K with appropriate concentration of the reactants should be inserted to the
progress of the reaction for synthesis of copper nanoparticles. In Figure 3, SEM images A, B, C of copper
nanoparticles synthesized at 343 K, 353 K, 363 K respectively, comparison of the images shows that the copper
nanoparticles synthesized at 363 K have a wider range of size distribution. In addition, the nanoparticles were
agglomerated in these conditions while copper nanoparticles synthesized at 353 K are well dispersed with an
average size about 12 nm.
Basically, the reduction rate of Cu+2ions was increases by increasing the reaction temperature. Therefore the
synthesis rate is too high to control particle size at high temperature. When reducing agent adds to precursor solution
at 363 K, rate of growth and agglomeration as well as nucleation of copper nanoparticles accelerated almost
coincidently. These phenomena result in the formation of copper nanoparticles with high averaged size of the copper
nanoparticles were precipitated. Thus moderate temperature (353 K) should be selected for synthesis of the copper
nanoparticles with appropriate controlling on size.