The Critical Effect of Niobium Doping on the Formation of Mesostructured TiO2: Single-Crystalline Ordered Mesoporous Nb-TiO2and Plate-like Nb-TiO2with Ordered Mesoscale Dimples

Preparation of mesoporous nitrogen-doped titania comprising large crystallites with low thermal conductivity

Reducing the thermal conductivity (κ) of mesoporous N-doped titania (TiO2) is crucial for the development of TiO2-based materials that exhibit excellent electronic, photochemical, and thermoelectric properties. Mesopores can contribute to the reduction of κ via phonon scattering, and the scattering effect due to the randomness of crystal interfaces should be significantly reduced to clarify the role of mesopores in reducing thermal conductivity. Highly ordered mesoporous N-doped TiO2 comprising large crystallites was prepared with silica colloidal crystals as a template into which a Ti source was introduced, followed by calcination with urea. N-doped samples comprising large crystallites exhibiting random mesopores were also prepared and used for the investigation of the effects of the shape and arrangement of the mesopore on phonon scattering. The mesostructures of the two separately prepared N-doped TiO2 samples were retained after sintering at 873 K and 80 MPa to fabricate pellets. Furthermore, the effective suppression of the long mean-free-path phonon conduction by the thin pore walls at a nanometer scale thickness significantly reduced the thermal conductivities of both samples. The presence of ordered mesopores further contributed to the reduction of κ, which was probably due to the enhanced contribution of the backscattering of phonons caused by ordered pore wall surfaces.

Solvothermal synthesis of Nb-doped TiO2 nanoparticles with enhanced sonodynamic effects for destroying tumors

Titania (TiO₂) nanomaterials have been proved to be biocompatible sonosensitizers for sonodynamic therapy (SDT) of various cancer cells, while they suffer from weak sonodynamic effects due to fast combination of excited carriers. In this work, to improve the therapeutic efficiency, we prepared PEGylated Nb-doped TiO₂ (TiO_2−x:Nb) nanoparticles by a simple solvothermal method and a subsequent surface modification process. The TiO_2−x:Nb nanoparticles exhibited an average size of 11 nm and a polydisperse index of 0.12. The Nb doping had no obvious effect on the phase of TiO₂ matrixes but released electrons to the conduction band of TiO₂, resulting in high concentrations of deficiencies. As a result, the TiO_2−x:Nb nanoparticles exhibited a higher efficiency of singlet oxygen (¹O₂) generation than that of pure TiO₂ nanoparticles upon ultrasound irradiation. Importantly, the TiO_2−x:Nb nanoparticles had high biocompatibility similar to pure TiO₂ nanoparticles, while they could efficiently produce cytotoxic ¹O₂ to destroy cancer cells in vitro in comparison to the partially destroyed cancer cells by pure TiO₂ nanoparticles upon ultrasound irradiation. More importantly, the TiO_2−x:Nb nanoparticles displayed obvious tumor cellular injury in tumor-bearing mice in vivo through high SDT effects. Therefore, the synthesized PEGylated TiO_2−x:Nb nanoparticles in this study exhibited higher therapeutic effects of SDT than that of the pure TiO₂ nanoparticles, and the doping strategy would provide some insights for tuning traditional weak sonosensitizers into efficient ones.

TiO_2−x:Nb nanoparticles displayed obvious tumor cellular injury in tumor-bearing mice in vivo through high SDT effect.

Fully printable hole-conductor-free mesoscopic perovskite solar cells based on mesoporous anatase single crystals

Mesoporous anatase single crystal titania with a small particle size was introduced into fully printable hole-conductor-free hybrid solar cells, which shows an optimal electron transport and carrier lifetime, leading to an enhanced device performance.