I prepared zinc oxide nanoparticles by reacting zinc sulfate with sodium hydroxide and urea. Then, I centrifuged the reaction mixture to obtain the white powder and washed it with deionized water several times. I then mixed the powder with deionized water for UV-Vis. My results are a bit weird and I need help understanding it. I performed UV-Vis for wavelengths between 200-800nm. Starting at 800nm, the absorbance is 0.045 and increases slowly to 0.0483 at 600nm. Then, it slowly decreases to 0.033 at 382nm. Here, it increases rapidly forming a "v" shape until 375nm and the spectrum continues until 200nm. I have a few questions: Why does ZnO show absorbance in the visible spectrum from 400-700nm? I made sure that my prepared solution was transparent before testing. ZnO should have an absorption peak around 350-390nm. Apparently mine is a "v" shaped trough. How did this occur?