Green Preparation of Cu Nanoparticles with Bioreductor of Red Dragon Fruit Peel Extract: Visible Spectroscopy Properties oleh La Ode Ahmad Nur Ramadhan, Siti Linda Cahayani Fanihu, Abdul Haris Watoni, Rijal Rijal, Nur Sofa Camelia Santoso, Wa Ode Nasyarah Rafiqa, Cindy Agriningsih Haruna, Zainal Syam Arifin