Here, we report mesoporous TiO@N-doped carbon composite nanospheres synthesized via a double-surfactant-assisted assembly sol-gel process followed by sequential carbonization of surfactants under a N atmosphere. The resulting TiO@N-doped C composite nanospheres are composed of uniformly distributed TiO nanocrystals with a diameter of ∼8 nm coated by a N-doped carbon layer that was formed by surfactants. Moreover, a large number of connected mesopores were observed in the nanospheres after high-temperature carbonization treatment. The synthesized nanospheres possess a large specific surface area (∼120 m g) and a large pore size (4-40 nm), with a well-defined spherical structure and a diameter in the nanoscale range. As an anode material for lithium-ion batteries (LIB), the mesoporous composite nanospheres delivered a reversible capacity of ∼117 mA h g after 2000 cycles at a current rate as high as 10 C, as well as superior rate capability. The N-doped carbon layers greatly improved the overall electrical conductivity of the mesoporous TiO nanospheres. This study provides a remarkable synthetic route for the preparation of mesoporous TiO-based N-doped carbon composite materials as high-performance anode materials in LIBs.

Exploring facile and reproducible methods to prepare mesoporous TiO2 nanospheres is crucial for improving the performance of TiO2 materials for energy conversion and storage. Herein, we report a simple and reproducible double-surfactant assembly-directed method to prepare monodisperse mesoporous TiO2 nanospheres. A double-surfactant system of n-dodecylamine (DDA) and Pluronic F127 was adopted to control the hydrolysis and condensation rates of tetrabutyl titanate in a mixture of water and alcohol at room temperature. In this process, the diameter size of mesoporous TiO2 nanospheres can be simply tuned from ∼50 to 250 nm by varying the concentration of H2O and surfactants. The double-surfactant system of DDA and F127 plays an effective role in determining the size, morphology, and monodispersity of mesoporous TiO2 nanospheres to reduce agglomeration during the sol-gel process. The resultant mesoporous anatase TiO2 nanospheres after solvothermal treatment at 160 °C are built of interpenetrating nanocrystals with a size of ∼10 nm, which are arranged to obtain a large number of connecting mesopores. Mesoporous TiO2 nanospheres with a small diameter size of around 50 nm possess a high surface area (∼160 m(2)/g) and mesopores with sizes of 4-30 nm. The small diameter size, high crystallinity, and mesoporous structure of TiO2 nanospheres lead to excellent performance in cycling stability and rate capability for lithium-ion batteries. After 500 cycles, the monodisperse mesoporous TiO2 nanospheres exhibit a charge capacity as high as 156 mAhg(-1) without obvious fade, and the Coulombic efficiency can reach up to 100%.

A general method for assembling patterned interfaces of uniform, flexible mesoporous iron oxide nanopyramid islands (NPIs) is presented. The three-dimensional (3D) mesoporous iron oxide-NPI interfaces possess a unique mesostructure that features a large surface area (~158 m 2 g − 1 ), a large pore size (~18 nm) and excellent flexibility (can be folded 100 times). Furthermore, the 3D mesoporous Au-NPI interfaces allow efficient immobilization of cytochrome c (Cyt c; more than 165-fold increase) and a significant enhancement of localized surface plasmon resonance (~26-fold at 625 nm) compared with that of two-dimensional (2D) planar iron oxide films without nanopores. More importantly, the ultrasensitive integrated interfaces demonstrate over 1000-fold enhancement of the photocurrent variation on the 3D mesostructures based on the switchable direct electrochemistry of Cyt c. The strategy of interfacial assembly offers new possibilities for the chemical design of patterned mesoporous semiconductors with high flexibility and tailored photocatalytic characteristics. This investigation provides a novel paradigm for an unconventional 3D porous biointerface that can be used for sub-nanomolar level recognition of biomolecules (~0.2 nM for H 2 O 2 ) and suggests the new concept of large-surface-area 3D mesostructure-protein interfaces as a step toward using direct electrochemistry for biomedical applications.