Complex ZnO-TiO2 Core-Shell Flower-Like Architectures with Enhanced Photocatalytic Performance and Superhydrophilicity without UV Irradiation

CdSe Quantum Dots Bedecked on ZnO/TiO2/CuO Ternary Nanocomposite for Enhanced Photocatalytic and Photovoltaic Applications

Herein, we synthesized a CdSe quantum dots (QDs)-decorated ternary metal oxide nanocomposite of ZnO/TiO2/CuO through a simple hydrothermal method. The prepared nanocomposite exhibited monoclinic, hexagonal, and cubic phase structures in XRD (X-ray diffraction) analysis. UV-vis absorbance spectra showed the broad absorption spectrum. SEM (scanning electron microscopy) clearly showed the presence of nanoparticles and confirmed the elements through elemental mapping. TEM (transmission electron microscopy) confirmed the nanostructure of metal oxides decorated with QDs. The average particle size was 45 nm for metal oxides and 7 nm for QDs. XPS (X-ray photoelectron spectroscopy) also confirmed the surface elemental composition. The prepared nanocomposites were introduced as photoanodes in DSSCs (dye-sensitized solar cells) and as photocatalysts for industrial dye solution. Among these samples, CdSe@CuO/TiO2/ZnO showed an improved performance of PCE (photon conversion efficiency) of 3.68% in DSSC and 96% photocatalytic degradation efficiency. It showed a recycling efficiency of ∼92% after 4 cycles against methylene blue (MB) organic dye under visible light irradiation.

The removal enhancement of organic contaminations and optimization of the photocatalytic efficiency by Box-Behnken design using ZnO-TiO2/porous graphene aerogel

In this study, zinc oxide-titanium dioxide/graphene aerogel (ZnO-TiO2/GA) was successfully synthesized through a simple and cost-effective hydrothermal self-assembly process. Besides, the surface response model and the experimental design according to the Box-Behnken model were selected to determine the optimal removal efficiency for crystal violet (CV) dye and para-nitrophenol (p-NP) phenolic compound. According to the obtained results, the highest degradation efficiency for CV dye of 99.6% was obtained under the following conditions: pH 6.7, CV concentration of 23.0 mg/L, and catalyst dose of 0.30 g/L. For p-NP, the degradation efficiency reached 99.1% under the following conditions: H2O2 volume of 1.25 mL, pH 6.8, and catalyst dose of 0.35 g/L. Therewithal, kinetic models of adsorption-photodegradation, thermodynamic adsorption, and free radical scavenging experiments were also investigated to propose the specific mechanisms involving the removal of CV dye and p-NP. According to the aforementioned results, the study provided a resulting ternary nanocomposite with great removal performance for water pollutants via the synergetic effects of adsorption and photodegradation processes.

ZnO nucleation into trititanate nanotubes by ALD equipment techniques, a new way to functionalize layered metal oxides

In this contribution, we explore the potential of atomic layer deposition (ALD) techniques for developing new semiconductor metal oxide composites. Specifically, we investigate the functionalization of multi-wall trititanate nanotubes, H₂Ti₃O₇ NTs (sample T1) with zinc oxide employing two different ALD approaches: vapor phase metalation (VPM) using diethylzinc (Zn(C₂H₅)₂, DEZ) as a unique ALD precursor, and multiple pulsed vapor phase infiltration (MPI) using DEZ and water as precursors. We obtained two different types of tubular H₂Ti₃O₇ species containing ZnO in their structures. Multi-wall trititanate nanotubes with ZnO intercalated inside the tube wall sheets were the main products from the VPM infiltration (sample T2). On the other hand, MPI (sample T3) principally leads to single-wall nanotubes with a ZnO hierarchical bi-modal functionalization, thin film coating, and surface decorated with ZnO particles. The products were mainly characterized by electron microscopy, energy dispersive X-ray, powder X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. An initial evaluation of the optical characteristics of the products demonstrated that they behaved as semiconductors. The IR study revealed the role of water, endogenous and/or exogenous, in determining the structure and properties of the products. The results confirm that ALD is a versatile tool, promising for developing tailor-made semiconductor materials.

rGO Functionalized ZnO–TiO2 Core-Shell Flower-Like Architectures for Visible Light Photocatalysis

Core-shell heterostructures with a complex, flower-like morphology, comprising a ZnO core and a TiO2 shell decorated with reduced graphene oxide (rGO) sheets by hydrothermal wrapping, are reported to extend the absorption properties of the semiconductors toward the visible light range. The ternary photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, Raman spectroscopy, diffuse reflectance UV–Vis, and attenuated total reflectance-Fourier transform infrared spectroscopy. Its photocatalytic performance was evaluated under visible light irradiation using methylene blue dye as a model pollutant. The rGO-modified ZnO–TiO2 photocatalyst exhibited superior photoactivity compared to that of the parent ZnO–TiO2 core-shell structures, which was dependent on its graphene content. The enhanced photocatalytic response was attributed to the higher absorption in the visible light range, as well as the pronounced electron and hole separation in the ternary system.

Microwave-assisted synthesis of porous and hollow α-Fe2O3/LaFeO3 nanostructures for acetone gas sensing as well as photocatalytic degradation of methylene blue

To address the urgent issues of hazardous gas detection and the prevention of environmental pollution, various functional materials for gas sensing and catalytic reduction have been studied. Specifically, the p-type perovskite LaFeO₃ has been studied widely because of its promising physicochemical properties. However, there remains several problems to develop a controllable synthesis of LaFeO₃-based p-n heterojunctions. In this work, α-Fe₂O₃ was further compounded with LaFeO₃ to form a porous and hollow α-Fe₂O₃/LaFeO₃ heterojunction to improve its gas-sensing performance and photocatalytic efficiency via a microwave-assisted hydrothermal method. While evaluated as sensors of acetone gas, the optimized sample exhibits excellent performance, including a high response (48.3), excellent selectivity, good reversibility, fast response, and recovery ability. Furthermore, it is an efficient catalyst for the degradation of methylene blue. This can be attributed to the enhancement effect of its larger specific surface area, fast diffusion, enhanced surface activities, and p-n heterojunction. Additionally, this work provides a rapid and rational synthesis strategy to produce metal oxides with both enhanced gas-sensing performance and improved photocatalytic properties.

Superhydrophilic Smart Coating for Self-Cleaning Application on Glass Substrate

In general, superhydrophilic coating on glass substrate possesses water contact angle (WCA) below 10° and contains high self-cleaning properties in outdoor environment as compared to noncoated glass substrate panels. In this study, the superhydrophilic coating behavior on glass substrate has been developed. The micro- and nanosized titanium dioxide (TiO2) particles have been utilized to improve the surface roughness, and the polypropylene glycol (PPG) has been utilized to increase the surface energy of glass substrates. The wettability of coating surface shows the coating possess water contact angle (WCA) as low as 5° and suddenly reduce to 0° after 10 s. Superhydrophilic coated glass clearly shows excellent dirt repellent against dilute ketchup solution due to the absence of dirt streak on the glass surface. Meanwhile, the dirt streak is present on the bare glass surface indicating its weak self-cleaning property. The developed superhydrophilic coating on glass substrate was also found to have great antifog property compared to the bare glass substrate. Superhydrophilic surfaces have showed free tiny droplet even at 130°C of hot boiling bath for 10 min and completely dry after 1 min. The superhydrophilic coating surfaces have demonstrated free water streak after impacting with harsh water spraying for 5 min confirming that the superhydrophilic coating on glass substrate is antiwater streak.