Study of Different Ti/Zr Ratios on the Physicochemical Properties and Catalytic Activities for CuO/Ti–Zr–O Composites

Chemical synthesis, characterization, and anticancer potential of CuO/ZrO2/TiO2/RGO nanocomposites against human breast (MCF-7) cancer cells

Nanocomposites (NCs) have attractive potential applications in gas-sensing, energy, photocatalysis, and biomedicine. In the present work, the fabrication of CuO/ZrO2/TiO2/RGO nanocomposites (NCs) was done via a simple chemical route. Our aim in this work was to synthesis and investigate the selective anticancer activity of TiO2 NPs by supporting CuO, ZrO2, and RGO toward cancer and normal cells. Different analytical techniques, such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL) spectroscopy, and dynamic light scattering (DLS), were carefully applied to characterize the physicochemical properties of the produced samples. XRD results showed that the phase and crystal structure of TiO2 NPs were enhanced after adding CuO, ZrO2, and RGO. TEM and SEM images showed that CuO/ZrO2/TiO2/RGO NCs were similarly distributed on RGO sheets with high crystallinity, excellent quality of lattice fringes, and lower agglomeration compared with pure TiO2 NPs. EDX and XPS analysis confirmed the presence of elements Cu, Zr, Ti, O, and C in the obtained CuO/ZrO2/TiO2/RGO NCs. Raman and FTIR spectra verified the presence of functional groups and crystal structures in the produced samples. PL data showed that the optical properties of TiO2 improved after adding CuO, ZrO2, and RGO sheets owing to the reduction in the recombination rate between the electron-hole pair. DLS analysis showed that the prepared CuO/ZrO2/TiO2/RGO NCs had excellent colloidal stability and good distribution in the suspension of the media culture. Anticancer results for CuO/ZrO2/TiO2/RGO NCs exhibited about 2-fold higher toxicity for 24 h and 4-fold for 48 h against breast cancer (MCF-7) cells than pure TiO2 NPs, while their biocompatibility was excellent against HUVEC normal cells. Additionally, the IC50 values of CuO/ZrO2/TiO2/RGO NCs were 44.19 ± 1.2 μg mL-1 and 24.52 ± 0.8 μg mL-1 for 24 h and 48 h, respectively. These results indicate that adding CuO, ZrO2, and RGO plays a crucial role in enhancing the anticancer property of TiO2 NPs. This study suggests that CuO/ZrO2/TiO2/RGO NCs could be applied in cancer therapy applications in in vivo models.

Study of Mesoporous Zr-TiO2 Catalyst with Rich Oxygen Vacancies for N-Methylmorpholine Oxidation to N-Methylmorpholine-N-oxide

A series of Zr-TiO2 catalysts were prepared using a facile sol-gel method and were used for N-methylmorpholine (NMM) oxidation to N-methylmorpholine-N-oxide (NMMO). The structure features of Zr-TiO2 catalysts were studied in detail through a variety of characterization methods, such as XRD, SEM, N2 adsorption-desorption isotherms, XPS, EPR, and O2-TPD. As-obtained 5%Zr-TiO2 catalysts had superior catalytic performance and stability with a 97.6% NMMO yield at 40 °C, which related to Zr doping, a higher surface area, more oxygen vacancies, and oxygen chemisorption on the catalytic surface. This work provides an efficient preparation strategy of TiO2-based catalysts for selective oxidation reactions by a facile method.

Green Synthesis of N/Zr Co-Doped TiO2 for Photocatalytic Degradation of p-Nitrophenol in Wastewater

TiO2 prepared by a green aqueous sol–gel peptization process is co-doped with nitrogen and zirconium to improve and extend its photoactivity to the visible region. Two nitrogen precursors are used: urea and triethylamine; zirconium (IV) tert-butoxide is added as a source of zirconia. The N/Ti molar ratio is fixed regardless of the chosen nitrogen precursor while the quantity of zirconia is set to 0.7, 1.4, 2, or 2.8 mol%. The performance and physico-chemical properties of these materials are compared with the commercial Evonik P25 photocatalyst. For all doped and co-doped samples, TiO2 nanoparticles of 4 to 8 nm of size are formed of anatase-brookite phases, with a specific surface area between 125 and 280 m2 g−1 vs. 50 m2 g−1 for the commercial P25 photocatalyst. X-ray photoelectron (XPS) measurements show that nitrogen is incorporated into the TiO2 materials through Ti-O-N bonds allowing light absorption in the visible region. The XPS spectra of the Zr-(co)doped powders show the presence of TiO2-ZrO2 mixed oxide materials. Under visible light, the best co-doped sample gives a degradation of p-nitrophenol (PNP) equal to 70% instead of 25% with pure TiO2 and 10% with P25 under the same conditions. Similarly, the photocatalytic activity improved under UV/visible reaching 95% with the best sample compared to 50% with pure TiO2. This study suggests that N/Zr co-doped TiO2 nanoparticles can be produced in a safe and energy-efficient way while being markedly more active than state-of-the-art photocatalytic materials under visible light.

Facile preparation of highly active and stable CuO–CeO2 catalysts for low-temperature CO oxidation via a direct solvothermal method

CuO–CeO₂ catalysts prepared by a direct solvothermal method exhibit high activity and stability for low-temperature CO oxidation.