Structural and photocatalytic properties of co-doped hybrid ZrO2–TiO2 photocatalysts

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.

The Application of TiO2/ZrO2-Modified Nanocomposite PES Membrane for Improved Permeability of Textile Dye in Water

This study investigates the modification of polyethersulfone (PES) membranes with 1 wt% titanium dioxide (TiO2), zirconium dioxide (ZrO2) and a nanocomposite of TiO2/ZrO2. The aim was to efficiently remove Rhodamine B (RhB) from water using a threefold approach of adsorption, filtration and photodegradation. Among the modified membranes (TiO2, ZrO2 and TiO2/ZrO2), the TiO2/ZrO2-PES nanocomposite membrane showed a better performance in rejection of RhB than other membranes with the rejection efficiency of 96.5%. The TiO2/ZrO2-PES membrane was found to possess a thicker selective layer and reduced mean pore radius, which contributed to its improved rejection. The TiO2/ZrO2 nanocomposite membrane also showed high bulk porosity and a slightly lower contact angle of 69.88° compared to pristine PES with a value of 73°, indicating an improvement in hydrophilicity. Additionally, the TiO2/ZrO2-PES nanocomposite membrane demonstrated a relatively lower surface roughness (Sa) of 8.53 nm, which offers the membrane antifouling properties. The TiO2/ZrO2-PES membrane showed flux recovery ratio (FRR), total fouling (Rt), reversible fouling (Rr) and irreversible fouling (Rir) of 48.0%, 88.7%, 36,8% and 52.9%, respectively. For the photocatalytic degradation performance, the removal efficiency of RhB followed this order TiO2 > TiO2/ZrO2 > ZrO2 (87.6%, 85.7%, 67.8%). The tensile strength and elongation were found to be compromised with the addition of nanoparticles and nanocomposites. This indicates the necessity to further modify and optimise membrane fabrication to achieve improved mechanical strength of the membranes. At low pressure, the overall findings suggest that the TiO2/ZrO2 nanocomposite has the potential to offer significant improvements in membrane performance (water flux) compared to other modifications.

Ce-Zr-based mixed oxide catalyst for oxidative depolymerization of kenaf stalk (biomass) into vanillin

Since petroleum became depleted, rapid attention has been devoted to renewable energy sources such as lignocellulosic biomass to produce useful chemicals for industry (for instance vanillin). Three primary components of lignocellulose are lignin, cellulose, and hemicellulose. This paper uses microwave-assisted technology to oxidize the kenaf stalk (lignocellulosic biomass) and extract lignin to produce vanillin. Catalysts with variable acid-base and redox properties are essential for the mentioned effective conversion, for this reason, CeO2-CA, ZrO2-CA, and CeZrO2-CA catalysts were synthesized. The citrate complexation method was used for the catalyst synthesis and the physicochemical characteristics were analyzed by XRD, FTIR, FE-SEM, TEM, BET, and TPO. The characterization results demonstrated that CeZrO2-CA shows the smallest sized crystallites with a large specific surface area among the other chosen catalysts. For vanillin production, the effect of reaction temperature, reaction time, and catalyst loading was studied. It was observed that compared to other catalysts, CeZrO2-CA produced the highest vanillin yield of 9.90% for kenaf stalk for 5 wt% of CeZrO2-CA at 160 °C for 30 min. Furthermore, vanillin production using extracted lignin is studied keeping CeZrO2-CA as a catalyst and with the same operating parameters, which yielded 14.3% of vanillin. Afterward, the change in yield with respect to pH is also presented. Finally, the recyclability of catalyst is also studied, which showed that it has a strong metal support and greater stability which may give industrial applications a significant boost.

Effect of Ag Modification on the Structure and Photocatalytic Performance of TiO2/Muscovite Composites

Ag/TiO2/muscovite (ATM) composites were prepared by the sol–gel method and the effects of Ag modification on the structure and photocatalytic performance were investigated. The photocatalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller surface area (BET), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), photoluminescence spectra (PL) and ultraviolet–visible diffuse reflectance spectra (DRS). The photocatalytic activity of the obtained composites was evaluated by taking 100 mL (10 mg/L) of Rhodamine B (RhB) aqueous solution as the target pollutant. The muscovite (Mus) loading releases the agglomeration of TiO2 particles and the specific surface area increases from 17.6 m2/g (pure TiO2) to 39.5 m2/g (TiO2/Mus). The first-order reaction rate constant increases from 0.0009 min−1 (pure TiO2) to 0.0074 min−1 (150%TiO2/Mus). Ag element exists in elemental silver. The specific surface area of 1-ATM further increases to 66.5 m2/g. Ag modification promotes the separation of photogenerated electrons and holes and increases the visible light absorption. 1%Ag-TiO2/Mus (1-ATM) exhibits the highest photocatalytic activity. After 100 min, the rhodamine B (RhB) degradation degrees of PT, 150%TiO2/Mus and 1-ATM are 10.4%, 48.6% and 90.6%, respectively. The first-order reaction rate constant of 1-ATM reaches 0.0225 min−1, which is 25 times higher than that of pure TiO2.

Synthesis of Mixed-Phase TiO2-ZrO2 Nanocomposite for Photocatalytic Wastewater Treatment

The use of TiO₂ nanoparticles for photocatalysis for the degradation of organic dyes under UV light for wastewater treatment has been widely studied. However, the photocatalytic characteristics of TiO₂ nanoparticles are inadequate due to their UV light response and higher band gap. In this work, three nanoparticles were synthesized: (i) TiO₂ nanoparticle was synthesized by a sol-gel process. (ii) ZrO₂ was prepared using a solution combustion process and (iii) mixed-phase TiO₂-ZrO₂ nanoparticles were synthesized by a sol-gel process to remove Eosin Yellow (EY) from aqueous solutions in the wastewater. XRD, FTIR, UV-VIS, TEM, and XPS analysis methods were used to examine the properties of the synthesized products. The XRD investigation supported the tetragonal and monoclinic crystal structures of the TiO₂ and ZrO₂ nanoparticles. TEM studies identified that mixed-phase TiO₂-ZrO₂ nanoparticles have the same tetragonal structure as pure mixed-phase. The degradation of Eosin Yellow (EY) was examined using TiO₂, ZrO₂, and mixed-phase TiO₂-ZrO₂ nanoparticles under visible light. The results confirmed that the mixed-phase TiO₂-ZrO₂nanoparticles show a higher level of photocatalytic activity, and the process is accomplished at a high degradation rate in lesser time and at a lower power intensity.

Photocatalytic Degradation of Rhodamine B and Methylene Orange Using TiO2-ZrO2 as Nanocomposite

The present research reports the synthesis of ZrO2-doped TiO2 photocatalysts at different ZrO2 contents (1, 3 and 5% wt.) synthesized by the sol–gel method. The samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction, attenuated total reflectance-Fourier transform infrared, ultraviolet–visible, X-ray photoelectron spectroscopy and N2 adsorption–desorption analysis. The photocatalytic activity of the ZrO2-doped TiO2 was investigated against the dyes methyl orange and rhodamine B through mineralization studies. The ZrO2-doped TiO2 samples presented a semiglobular-ovoid agglomerate shape around 500–800 nm. The samples presented high crystallinity of the TiO2 anatase phase, XPS suggested the formation of Zr–O–Ti bonds and the samples were classified as mesoporous materials with slight changes in the optical features in comparison with pure TiO2. Our study shows that the ZrO2-doped TiO2 composites exhibited a higher photocatalytic activity than just utilizing the synthetized TiO2 and a commercial P25. The different degradation behaviors are attributed to differences in the textural properties, and to the different optical absorptions of the samples due to structural defects created by the level of doping of Zr4+ ions into the TiO2 lattice. Reaction kinetics parameters were calculated by the Langmuir–Hinshelwood model, and a third run cycle of the ZrO2-doped TiO2 at 1% wt. achieved a photocatalytic degradation of 78.1 and 75.5% for RhB and MO, respectively.