No it is not viewed under the UV light, and crystallization methods did not completely remove DCU, but I think you might see a yellow spot when you treat the TLC to ninhydrin stain, because of the presence of NH group, and if the Rf is quite different from your spot on the TLC, you can use a column chromatography.
I'm pretty sure that PMA (phosphomolybdic acid) staining will 'visualize' DCU. Co-elution of DCU with your product is a common problem when using DCC as a coupling agent. That's why I prefer using 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC, EDAC or EDCI) as it is water soluble and, therefore, removed with aqueous work-up. HATU (1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxid hexafluorophosphate) is also highly recommended.