Metal phosphates are widely utilized in nonlinear optical materials, phosphors, sensors, heat-resistant, and biocompatible materials. A particular emphasis has been placed on the study of rare-earth or rare-earth-doped phosphate materials for applications in photonic devices. [1] This interest is primarily attributed to the position of the 4f electrons, which are well shielded from the effects of the neighboring ions. Such shielding leads to discrete and well-defined energy level schemes, as well as to rather weak coupling between the electronic and vibrational wave functions. The specific luminescence with a characteristic long lifetime originates from the f-f emissions. However, at present, the progress with regard to new luminescent materials is chiefly focussed on short emission wavelengths, which are useful for imaging, lithography, and optical data recording.[2] The rare-earth ions Ce 3+ and Sm 2+ exhibit a 5d-4f emission with a larger absorption in the UV region and a shorter luminescence lifetime due to allowed electric dipole transitions; thus, they display excellent properties for applications in these fields. [3] On the other hand, although the doping of transparent Ce 4+ ions in luminescence materials has been prohibited due to the competitive absorption in UV region, some Ce 3+ /Ce 4+ hybrid systems in glass hosts exhibit a strong blue emission, which possibly results from electron transfer from a donor level to the neighboring Ce 4+ ions, consequently forming excited states of Ce 3+ ions. [4] Taking into account the strong UV absorption of Ce 4+ ions, such hybrid structures are good candidates for materials that display blue emission with high absorption and fast emissive rates. [5] One-dimensional nanomaterials, that is, nanotubes made of, for example, C, BN, WS 2 , VO x , TiO 2 , and InP [6] have been synthesized and display novel properties that are frequently different from those of the bulk forms. However, the synthesis and emission behaviour of nanotube-like hybrid materials containing Ce 4+ /Ce 3+ ions has received much less attention. Herein, we report on a reproducible and controllable route for the production of cerium phosphate nanotubes, the first rare-earth phosphate nanotubes. Tetravalent cerium phosphate (CeP, Ce(HPO 4 ) 2 ·n H 2 O) nanotubes were first synthesized after improving the traditional synthetic route toward a CeP fiber.[7] Subsequent annealing of the assynthesized nanotubes led to a mixture of valence states, and the desired Ce 3+ /Ce 4+ hybrid phosphate nanotubes were obtained for the first time. The nanotubes display novel optical properties; that is, the Ce 4+ ions effectively absorb the UV light, whereas the Ce 3+ ions exhibit strong emission in the blue region of a photoluminescence spectrum.It has been reported that a high PO 4 /Ce ratio (20:1-120:1) in the initial solution and a high reaction temperature (up to 95 8C) are needed to form a CeP fiber. [7,8] In this study, we have increased the PO 4 /Ce ratio to 300:1 and increased the reaction temperature to above ...