The preliminary test to check is the UV visible spectroscopy.

perform UV visible spectroscopy of your solutions of cu(II) before and after reduction. you will surely see a shift in the peak after the reduction.

Good Luck

Plant extracts contain weak reducing agents, which usually reduce ions of silver, gold, platinum ... Iron ions are reduced by strong reducing agents with hydrazine, borohydride and in the presence of an inert gas of argon or nitrogen. Then, the resulting metal nanoparticles do not oxidize. To analyze the end of the reaction, it is useless to use UV-visible spectroscopy. Extracts contain substances absorbing in this part of the spectrum. If you get solid nanoparticles, they need to be separated in a centrifuge or long-term sedimentation, washed from the substances of the extract and do elemental analysis.

Thank you for all of your response. Well appreciated :)