A new application of Langmuir-Blodgett (LB) film for the selective isolation of UO22+ from aqueous solution is reported. UO22+ can be isolated onto a quartz plate coated with a novel LB film which possesses the potential to form a complex with transition metal cations. The isolation process can be switched on by photoillumination and is distinguished by optical absorption spectroscopy. Isolated UO22+ can partly be released into acid solution, and the film can be used repeatedly for this extraction. This ion-exchange capability is sufficiently selective for UO22+ because of its strong affinity to the functional group in the LB film. Using the results traced by optical measurements, the lower limit of ion concentration for extraction was estimated to be 5 x 10(-5) M.