Prabodini Wimalasiri "Use of UV-Vis Spectrophotometry for Characterization of Carbon Nanostructures: a Review" reported that urea nanoparticles synthesized by a precipitation method had a λmax of 260 nm in water, and the average particle size was estimated to be 25 nm. Another study reported that urea nanoparticles synthesized by a sol-gel method had a λmax of 280 nm in ethanol, and the average particle size was estimated to be 35 nm.

These results suggest that different synthesis methods can affect the optical properties and the morphology of the urea nanoparticles. Therefore, it is important to optimize the synthesis conditions and the measurement parameters to obtain accurate and reliable results by UV-visible spectroscopy.

The wavelength of light that can be obtained for urea nanoparticles in a solution by analyzing a UV-visible spectrophotometer is typically between 200 and 350 nanometers (nm). This is because urea nanoparticles absorb light in the ultraviolet (UV) region of the electromagnetic spectrum. The specific wavelength of maximum absorbance will depend on the size and shape of the nanoparticles, as well as the concentration of urea in the solution.