Nano Titanium Monoxide Crystals and Unusual Superconductivity at 11 K

Nano TiO2 is investigated intensely due to extraordinary photoelectric performances in photocatalysis, new‐type solar cells, etc., but only very few synthesis and physical properties have been reported on nanostructured TiO or other low valent titanium‐containing oxides. Here, a core–shell nanoparticle made of TiO core covered with a ≈5 nm shell of amorphous TiO1+x is newly constructed via a controllable reduction method to synthesize nano TiO core and subsequent soft oxidation to form the shell (TiO1+x). The physical properties measurements of electrical transport and magnetism indicate these TiO@TiO1+x nanocrystals are a type‐ІІ superconductor of a recorded Tconset = 11 K in the binary Ti–O system. This unusual superconductivity could be attributed to the interfacial effect due to the nearly linear gradient of O/Ti ratio across the outer amorphous layer. This novel synthetic method and enhanced superconductivity could open up possibilities in interface superconductivity of nanostructured composites with well‐controlled interfaces. Nano‐titanium‐monoxide with the crystalline core (TiO) covered with a ≈5 nm shell of amorphous TiO1+x is prepared for the first time and the highest Tc (11 K) in the binary Ti–O system is observed. Through controllable reduction and soft oxidation, the obtained sample is observed with nearly linear (1.0–1.9) variation of O/Ti ratio across the amorphous layer, suggesting a smooth interface which contributes to the unusual superconductivity.