Green and Phytogenic Fabrication of Co-Doped SnO2 Using Aqueous Leaf Extract of Tradescantia spathacea for Photoantioxidant and Photocatalytic Studies

Microwave-assisted synthesis of Ni-doped europium hydroxide for photocatalytic degradation of 4-nitrophenol

Microwave-assisted synthesis method was used to prepare europium hydroxide (Eu(OH)3) and different percentages of 1, 5, and 10 % nickel-doped Eu(OH)3 (Ni-Eu(OH)3) nanorods (NRs). X-ray diffraction study showed a hexagonal phase with an average crystallite size in the range of 21 - 35 nm for Eu(OH)3 and Ni-Eu(OH)3 NRs. FT-IR and Raman studies also confirmed the synthesis of Eu(OH)3 and Ni-Eu(OH)3. The synthesized materials showed rod-like morphology with an average length and diameter between 27 - 50 nm and 8 - 13 nm, respectively. The band gap energies of Ni-Eu(OH)3 NRs were reduced (4.06 - 3.50 eV), which indicates that the doping of Ni2+ ions has influenced the band gap energy of Eu(OH)3. The PL study exhibited PL quenching with Ni doping. The photocatalytic degradation of 4-nitrophenol (4-NP) by the synthesized materials under UV light irradiation was investigated, in which 10 % Ni-Eu(OH)3 NRs showed the best response. A kinetic study was also conducted which shows pseudo-first-order kinetics. Based on this, Ni-Eu(OH)3 NRs have shown a potential to be a UV-light active material for photocatalysis.

Impact of Co-Doping on the Visible Light-Driven Photocatalytic and Photoelectrochemical Activities of Eu(OH)3

The microwave-assisted synthesis approach was used to synthesize Eu(OH)3 and Co-Eu(OH)3 nanorods. Various techniques were used to investigate the structural, optical, and morphological features of the Eu(OH)3 and Co-Eu(OH)3 NRs. Both Eu(OH)3 and Co-Eu(OH)3 NRs were found to be hexagonal with crystallite sizes ranging from 21 to 35 nm. FT-IR and Raman spectra confirmed the formation of Eu(OH)3 and Co-Eu(OH)3. Rod-shaped Eu(OH)3 and Co-Eu(OH)3 with average lengths and diameters ranging from 27 to 50 nm and 8 to 12 nm, respectively, were confirmed by TEM. The addition of Co was found to increase the particle size. Furthermore, with increased Co doping, the band gap energies of Co-Eu(OH)3 NRs were lowered (3.80-2.49 eV) in comparison to Eu(OH)3, and the PL intensities with Co doping were quenched, suggesting the lessening of electron/hole recombination. The effect of these altered properties of Eu(OH)3 and Co-Eu(OH)3 was observed through the photocatalytic degradation of brilliant green dye (BG) and photoelectrochemical activity. In the photocatalytic degradation of BG, 5% Co-Eu(OH)3 had the highest response. However, photoelectrochemical experiments suggested that 10% Co-Eu(OH)3 NRs showed improved activity when exposed to visible light. As a result, Co-Eu(OH)3 NRs have the potential to be a promising visible-light active material for photocatalysis.

Photocatalytic degradation of brilliant green and 4-nitrophenol using Ni-doped Gd(OH)3 nanorods

Gadolinium hydroxide (Gd(OH)3) was synthesized via a microwave-assisted synthesis method. Nickel ion (Ni2+) was doped into Gd(OH)3, in which 4-12% Ni-Gd(OH)3 was synthesized, to study the effect of doping. The structural, optical, and morphological properties of the synthesized materials were analyzed. The crystallite sizes of the hexagonal structure of Gd(OH)3 and Ni-Gd(OH)3, which were 17-30 nm, were obtained from x-ray diffraction analysis. The vibrational modes of Gd(OH)3 and Ni-Gd(OH)3 were confirmed using Raman and Fourier-transform infrared spectroscopies. The band gap energy was greatly influenced by Ni-doping, in which a reduction of the band gap energy from 5.00 to 3.03 eV was observed. Transmission electron microscopy images showed nanorods of Gd(OH)3 and Ni-Gd(OH)3 and the particle size increased upon doping with Ni2+. Photocatalytic degradations of brilliant green (BG) and 4-nitrophenol (4-NP) under UV light irradiation were carried out. In both experiments, 12% Ni-Gd(OH)3 showed the highest photocatalytic response in degrading BG and 4-NP, which is about 92% and 69%, respectively. Therefore, this study shows that Ni-Gd(OH)3 has the potential to degrade organic pollutants.

Visible-Light-Induced Photocatalytic and Photoantibacterial Activities of Co-Doped CeO2

As one of the most significant rare earth oxides, the redox ability of cerium oxide (CeO₂) has become the primary factor that has attracted considerable interest over the past decades. In the present study, irregular pentagonal CeO₂ (S-CeO₂) and different amounts of (1, 4, 8, and 12% Co) cobalt-doped CeO₂ nanoparticles (Co-CeO₂ NPs) with particle sizes between 4 and 13 nm were synthesized via the microwave-assisted synthesis method. The structural, optical, and morphological studies of S-CeO₂ and Co-CeO₂ were carried out using various techniques. The shifts in the conduction band and valence band were found to cause the reduction of the band gap energies of S-CeO₂ and Co-CeO₂ NPs. Moreover, the quenching of photoluminescence intensity with more Co doping showed the enhanced separation of charge carriers. The photocatalytic activities of S-CeO₂ and Co-CeO₂ NPs for methylene blue dye degradation, 4-nitrophenol reduction, and their photoantibacterial properties under visible-light irradiation were investigated. Findings showed that, due to the lower band gap energy (2.28 eV), more than 40% of both photocatalytic activities were observed for 12% Co-CeO₂ NPs. On the other hand, higher antibacterial impact in the presence of light shows that the Co doping has a considerable influence on the photoantibacterial response of Co-CeO₂. Therefore, microwave-assisted synthesized CeO₂ and Co-CeO₂ NPs have shown potential in photocatalytic dye degradation, chemical reduction, and photoantibacterial activities.

Recent progress of phytogenic synthesis of ZnO, SnO2, and CeO2 nanomaterials

A critical investigation on the fabrication of metal oxide nanoparticles (NPs) such as ZnO, SnO₂, and CeO₂ NPs synthesized from green and phytogenic method using plants and various plant parts have been compiled. In this review, different plant extraction methods, synthesis methods, characterization techniques, effects of plant extract on the physical, chemical, and optical properties of green synthesized ZnO, SnO₂, and CeO₂ NPs also have been compiled and discussed. Effect of several parameters on the size, morphology, and optical band gap energy of metal oxide have been explored. Moreover, the role of solvents has been found important and discussed. Extract composition i.e. phytochemicals also found to affect the morphology and size of the synthesized ZnO, SnO₂, and CeO₂ NPs. It was found that, there is no universal extraction method that is ideal and extraction techniques is unique to the plant type, plant parts, and solvent used.

Effect of Zr doping on photoantioxidant and antibiofilm properties of CeO2 NPs fabricated using aqueous leaf extract of Pometia pinnata

Synthesized cerium oxide nanoparticles (S-CeO₂ NPs) and 1%, 5% and 10% zirconium doped CeO₂ (Zr-doped CeO₂) NPs were fabricated using aqueous leaf extract of Pometia pinnata. The synthesized NPs were characterized using standard techniques which confirmed successful synthesis of NPs with particle size ranging from 12 to 23 nm and band gap energy of 2.54-2.66 eV. Photoantioxidant activities showed enhanced activities under visible light irradiation in comparison to the dark condition in the dose-dependent study. Biofilm inhibition studies showed ~ 73% biofilm inhibition of Staphylococcus aureus at 512 µg/mL for S-CeO₂, whereas 10% Zr-doped CeO₂ NPs showed biofilm inhibition of 52.7%. The bactericidal tests showed killing properties at 1024 µg/mL of S-CeO₂ NPs and at 512 µg/mL of 1% Zr-doped CeO₂. Reduced bactericidal activities were observed for 5% and 10% Zr-doped CeO₂. These studies showed that the fabricated NPs have both good photoantioxidant and antibacterial properties.