Mangifera indica leaf-assisted biosynthesis of well-dispersed silver nanoparticles

Natural fluorite crystals containing oxygen impurities are colored electrolytically by using a pointed cathode and a flat anode at various temperatures and voltages. F and F₂ color centers are produced in colored fluorite crystals. O²⁻–V_a⁺, O²⁻–V_a⁺ aggregate, Yb²⁺, Ce³⁺ and Sm²⁺ absorption bands are observed in absorption spectra of uncolored fluorite crystals. O²⁻–V_a⁺, O²⁻–V_a⁺ aggregate, Yb²⁺, Ce³⁺, Sm²⁺, F, M (F₂) absorption bands and group of four absorption bands are observed simultaneously in absorption spectra of colored fluorite crystals. Current−time curve for electrolytic coloration of natural fluorite crystal and its relationship with electrolytic coloration process are given. Production and conversion of color centers are explained.