metal-oxide-heterojunction-for-photocatalytic-activities

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale ...

Adama Science and Technology University

This work reveals a green combustion route for the synthesis of TiO, FeO and TiO-FeO nanocomposites as photocatalysts for decolorization of Titan Yellow (TY) and Methyl Orange (MO) dyes at room temperature in aqueous solution concentration of 20 ppm under UV-light irradiation. We observed that the TiO-FeO nanocomposite shows superior photocatalytic activity for TY dye compared to pure TiO and FeO. Rate constant (k) values of TiO, FeO and TiO-FeO for TY and MO are 0.0194, 0.0159, 0.04396 and 0.00931, 0.00772 0.0119 kmin respectively. The surface area and pore volume of TiO-FeO nanocomposite were found to be 71.56 m/g and 0.076 cm/g, respectively as revealed by BET studies. From the Barrett-Joyner-Halenda (BJH) plot, the mean pore diameter of TiO-FeO nanoparticles was found to be 2.43 nm. Further, the TiO-FeO nanocomposite showed good electrochemical behavior as an electrode material for supercapacitors when compared to pure TiO and FeO nanoparticles resulted in stable electrochemical performance with nearly 100% coulombic efficiency at a scan rate of 10 mV/s for 1000 cycles. Interestingly, the novelty of this work is that the designed supercapacitors showed stable electrochemical performance even at 1000 cycle, which might be useful for rechargeable supercapacitor applications. The electrochemical properties of the nanocomposites were compared by the data obtained by cyclic voltammograms, charge-discharge tests and electrochemical impedance spectroscopic studies. These results demonstrated that the TiO-FeO nanocomposite showed stable performance compared to TiO and FeO nanoparticles at current density of 5 Ag.

Enhanced photocatalytic and electrochemical performance of TiO-FeO nanocomposite: Its applications in dye decolorization and as supercapacitors.

Metal oxide nanomaterials are one of the preferences as antibacterial active materials. Due to its distinctive electronic configuration and suitable properties, ZnO is one of the novel antibacterial active materials. Nowadays, researchers are making a serious effort to improve the antibacterial activities of ZnO by forming a composite with the same/different bandgap semiconductor materials and doping of ions. Applying capping agents such as polymers and plant extract that control the morphology and size of the nanomaterials and optimizing different conditions also enhance the antibacterial activity. Forming a nanocomposite and doping reduces the electron/hole recombination, increases the surface area to volume ratio, and also improves the stability towards dissolution and corrosion. The release of antimicrobial ions, electrostatic interaction, reactive oxygen species (ROS) generations are the crucial antibacterial activity mechanism. This review also presents a detailed discussion of the antibacterial activity improvement of ZnO by forming a composite, doping, and optimizing different conditions. The morphological analysis using scanning electron microscopy, field emission-scanning electron microscopy, field-emission transmission electron microscopy, fluorescence microscopy, and confocal microscopy can confirm the antibacterial activity and also supports for developing a satisfactory mechanism. Graphical abstract showing the metal oxides antibacterial mechanism and the fluorescence and scanning electron microscopic images.

A Review on Enhancing the Antibacterial Activity of ZnO: Mechanisms and Microscopic Investigation.

Zinc oxide (ZnO) is a fascinating semiconductor material with many applications such as adsorption, photocatalysis, sensor, and antibacterial activities. By using a poly (vinyl alcohol) (PVA) polymer as a capping agent and metal oxides (iron and manganese) as a couple, the porous PVA-aided Zn/Fe/Mn ternary oxide nanocomposite material (PTMO-NCM) was synthesized. The thermal, optical, crystallinity, chemical bonding, porosity, morphological, charge transfer properties of the synthesized materials were confirmed by DTG/DSC, UV-Vis-DRS, XRD, FT-IR, BET, SEM-EDAX/TEM-HRTEM-SAED, and CV/EIS/amperometric analytical techniques, respectively. The PTMO-NCM showed an enhanced surface area and charge transfer capability, compared to ZnO. Using the XRD pattern and TEM image analysis, the crystalline size of the materials was confirmed to be in the nanometer range. The porosity and superior charge transfer capabilities of the PTMO-NCM were confirmed from the BET, HRTEM (IFFT)/SAED, and CV/EIS analysis. The adsorption kinetics (adsorption reaction/adsorption diffusion) and adsorption isotherm test confirmed the presence of a chemisorption type of adsorbate/methylene blue dye-adsorbent/PTMO-NCM interaction. The photocatalytic performance was tested on the Congo red and Acid Orange-8 dyes. The superior ascorbic acid sensing capability of the material was understood from CV and amperometric analysis. The noble antibacterial activities of the material were also confirmed on both gram-negative and gram-positive bacteria.

Multifunctional application of PVA-aided Zn-Fe-Mn coupled oxide nanocomposite.

Zinc oxide is one of the novel metal oxides utilized for diverse applications. The sol-gel and unintended self-propagation procedures were applied to synthesize the porous and high surface area ZnO-based metal oxide nanocomposite. The p-type manganese(III) oxide was successfully coupled with n-type ZnO The physical property characterization results revealed the surface area, porosity, and charge transfer capability improvement on the poly(vinyl alcohol) (PVA)-aided binary nanocomposite (PVA-ZnO/MnO), compared to ZnO. The XRD patterns and TEM image analysis validated the nanometer size range for the materials (15-60 nm). The SEM micrographs and BET spectral details have confirmed the porous nature of the PVA-ZnO/MnO nanocomposite. The supporting results were obtained from the HRTEM (IFFT) and SAED pattern analyses. The EDX and HRTEM analyses were used for the confirmation of elemental composition and reality of the PVA-ZnO/MnO composite, respectively. The presence of the improved charge transfer property for PVA-ZnO/MnO, compared to ZnO, was evidenced from acid orange-8 dye degradation. The highest zone of inhibition (14 mm) was recorded on  bacteria for the uncalcined PVA-ZnO/MnO nanocomposite compared to PVA, yet, less zone of inhibition compared to the calcined PVA-ZnO/MnO nanocomposite. The authors recommend the formation of the couple between metal oxides by electrochemical technique analyses as a future work.

Synthesis of Poly(vinyl alcohol)-Aided ZnO/MnO Nanocomposites for Acid Orange-8 Dye Degradation: Mechanism and Antibacterial Activity.

Colloidal nanocrystals play a vital role in several applications. The doping of cations in the nanocrystal matrix enhances the optical, electrical, and magnetic properties. The number and well-defined distribution of the dopant are crucial to protect the nanocrystal from clustering. The XRD, XPS, and XAS instruments reveal the change in the lattice parameters, chemical states, and local coordination environment information. In addition of detecting the position and distribution of the dopant, the 4D-STEM detector mode gathers all types of real-space atomic-resolution images by collecting all diffraction datasets from each electron probe with high-speed and efficient detection. Dopant-host ligand type, reactions conditions, and reaction time optimization during synthesis are critical for the host and dopant reactivity balance. Pearson's hard/soft acids/bases theory would be a base for balancing the solubility of the dopant-host in the given solvents/surfactant. In addition, tuning the colloidal nanocrystals to secondary structures, which enhances the mass-/ions transport, can contribute a combination of properties that do not exist in the original constituents.

Article	Year
Enhanced photocatalytic and electrochemical performance of TiO-FeO nanocomposite: Its applications in dye decolorization and as supercapacitors. Scientific reports\| PubMed ID: 31988344	2020
A Review on Enhancing the Antibacterial Activity of ZnO: Mechanisms and Microscopic Investigation. Nanoscale research letters\| PubMed ID: 33001404	2020
Multifunctional application of PVA-aided Zn-Fe-Mn coupled oxide nanocomposite. Nanoscale research letters\| PubMed ID: 33387075	2021
Synthesis of Poly(vinyl alcohol)-Aided ZnO/MnO Nanocomposites for Acid Orange-8 Dye Degradation: Mechanism and Antibacterial Activity. ACS omega\| PubMed ID: 33458547	2021
Insights into ZnO-based doped porous nanocrystal frameworks. RSC advances\| PubMed ID: 35424565	2022

Buzuayehu Abebe

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