Preparation and testing of dyes
The dye extraction from papaya leaves (PL) was carried out as follows: the raw material (∼35 g) was first added to ethyl alcohol (350 mL, 96%, Merck, Germany) and heated at 70 °C for 3 h. The extracted dyes were then isolated from the ethanolic solution by rotary evaporation. Afterwards, the PL extracts were mixed with ethyl alcohol (96%, Merck, Germany) until the required concentration of 8 g/100 mL [7] was obtained.