Machine Learning-Assisted Estimation of the Photoantioxidant Activities of Bare, Mg, Cu, and Mg/Cu Dual-Doped ZnO

Green-synthesized pure zinc oxide (ZnO), Mg-doped ZnO, Cu-doped ZnO, and Mg/Cu dual-doped ZnO using aqueous leaf extract of Ziziphus mauritiana were analyzed for their antioxidant activities. In this study, the data-driven approach has been used to estimate the photoantioxidant activities of ZnO, Mg-doped ZnO, Cu-doped ZnO, and Mg/Cu dual-doped ZnO based on the experimental data and synthetic data generated through simulations. Three different machine learning models, including artificial neural network, extreme gradient boosting, and automated machine learning, were explored and compared for both data sets. These models were validated by using external validation and applicability domain methods based on the values of coefficient of determination, root mean square, and mean absolute errors. The performance of the machine learning techniques showed that photoantioxidant activities could be predicted accurately from the input variables such as types of dopants, percentage of dopants, average crystallite size, lighting condition, and concentration of antioxidants (photocatalyst). Doping and the lighting condition were found to have a more significant impact on the values of photoantioxidant activities of the ZnO, Mg-doped ZnO, Cu-doped ZnO, and Mg/Cu dual-doped ZnO in comparison to other variables. Based on three artificial neural network models, the variables for Mg doping and the lighting condition had weights with values ranging between 1.1 and 2.9

Biofilm-Assisted Fabrication of Ag@SnO₂‑<i>g</i>‑C₃N₄ Nanostructures for Visible Light-Induced Photocatalysis and Photoelectrochemical Performance

Development of advanced materials with a benign environmentally friendly approach for heterogeneous visible light photocatalysis is always preferable. An environmentally favorable approach was used to anchor silver nanoparticles (Ag NPs) to tin oxide-decorated-graphitic carbon nitride (SnO2-g-C3N4) using a biofilm as a green reducing tool for the biogenic synthesis of 1–6 mM Ag@SnO2-g-C3N4 nanostructures (NSs). The fabricated NSs were characterized using sophisticated techniques. The developed Ag@SnO2-g-C3N4 NSs showed a well-defined spherical-shaped Ag NPs anchored to SnO2-g-C3N4 NSs. The synthesized NSs were applied for photocatalytic degradation of hazardous dyes and photoelectrochemical studies. A comparative investigation of Ag@SnO2-g-C3N4 NSs for the visible light-assisted photocatalytic degradation of Methylene blue (MB), Congo red (CR), and Rhodamine B (RhB) was performed. The photocatalytic degradation of MB, CR, and RhB reached ∼99% in 90 min, ∼98% in 60 min, and ∼94% in 240 min, respectively. The anchoring of Ag NPs to SnO2-g-C3N4 NSs further enhanced the visible light photocatalytic degradation of the dyes due to surface plasmon resonance and by lowering the recombination of the photogenerated electrons and holes. Further, high electron transfer ability of Ag@SnO2-g-C3N4 NSs was investigated by electrochemical impedance spectroscopy to understand the mechanistic insights of the excellent activity under visible light irradiation. Hence, the present study provides an environmentally benign approach for the synthesis and excellent visible light effective photocatalysis and photoelectrochemical performance

Machine-Learning-Based Cyclic Voltammetry Behavior Model for Supercapacitance of Co-Doped Ceria/rGO Nanocomposite

This paper examines the cobalt-doped ceria/reduced graphene oxide (Co-CeO2/rGO) nanocomposite as a supercapacitor and modeling of its cyclic voltammetry behavior using Artificial Neural Network (ANN) and Random Forest Algorithm (RFA). Good agreement was found between experimental results and the predicted values generated by using ANN and RFA. Simulation results confirmed the accuracy of the models, compared to measurements from supercapacitor module power-cycling. A comparison of the best performance between ANN and RFA models shows that the ANN models performed better (value of coefficient of determination >0.95) than the RFA models for all datasets used in this study. The results of the ANN and RFA models could be useful in designing the unique nanocomposites for supercapacitors and other strategies related with energy and the environment

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

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

Environmentally Sustainable Fabrication of Ag@<i>g‑</i>C₃N₄ Nanostructures and Their Multifunctional Efficacy as Antibacterial Agents and Photocatalysts

Noble-metal silver (Ag) nanoparticles (NPs) anchored/decorated onto polymeric graphitic carbon nitride (<i>g</i>-C₃N₄) as nanostructures (NSs) were prepared using modest and environment-friendly synthesis method with a developed-single-strain biofilm as a reducing implement. The as-fabricated NSs were characterized using standard characterization techniques. The nanosized and uniform AgNPs were well deposited onto the sheet-like matrix of <i>g</i>-C₃N₄ and exhibited good antimicrobial activity and superior photodegradation of dyes methylene blue (MB) and rhodamine B (RhB) dyes under visible-light illumination. The Ag@<i>g</i>-C₃N₄ NSs exhibited active and effective bactericidal performance and a survival test in counter to <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, and <i>Pseudomonas aeruginosa.</i> The as-fabricated NSs also exhibited superior visible-light photodegradation of MB and RhB in much less time as compared to other reports. Ag@<i>g</i>-C₃N₄ NSs (3 mM) showed superior photocatalytic measurements under visible-light irradiation: ∼100% MB degradation and ∼89% of RhB degradation in 210 and 250 min, respectively. The obtained results indicate that the AgNPs were well deposited onto the <i>g</i>-C₃N₄ structure, which decreases the charge recombination rate of photogenerated electrons and holes and extends the performance of pure <i>g</i>-C₃N₄ under visible light. In conclusion, the as-fabricated Ag@<i>g</i>-C₃N₄ NSs are keen nanostructured materials that can be applied as antimicrobial materials and visible-light-induced photocatalysts

Simultaneous Enhancement of Methylene Blue Degradation and Power Generation in a Microbial Fuel Cell by Gold Nanoparticles

This study examined the effect of positively charged gold nanoparticles [(+)­AuNPs] on the enhancement of methylene blue (MB) degradation in a microbial fuel cell (MFC) cathode. Complete MB degradation and a maximum electricity production of 36.56 mW/m2 were achieved simultaneously. The MFC performance and MB degradation were found to be strictly dependent on the cathodic conditions, such as N2 bubbling, air bubbling, and addition of H2O2. MB was reduced rapidly under anaerobic conditions, whereas complete oxidative mineralization of MB occurred in the presence of dissolved oxygen (DO) or H2O2. (+)­AuNPs enhanced the electricity generation in the MFCs involving MB degradation owing to its electron-relay effect. The presence of both (+)­AuNPs and H2O2 produced the greatest enhancement in MB degradation. After 5 h, almost all of the MB (98%) and chemical oxygen demand (COD) (96%) had been removed in the presence of (+)­AuNPs, whereas only 57.4% of the MB and 40% of the COD had been removed in the absence of (+)­AuNPs

Biogenic Synthesis, Photocatalytic, and Photoelectrochemical Performance of Ag–ZnO Nanocomposite

The development of coupled photoactive materials (metal/semiconductor) has resulted in significant advancements in heterogeneous visible light photocatalysis. This work reports the novel biogenic synthesis of visible light active <i>Ag</i>–ZnO nanocomposite for photocatalysis and photoelectrode using an electrochemically active biofilm (EAB). The results showed that the EAB functioned as a biogenic reducing tool for the reduction of Ag⁺, thereby eliminating the need for conventional reducing agents. The as-prepared <i>Ag</i>–ZnO nanocomposite was characterized by X-ray diffraction, transmission electron microscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic experiments showed that the <i>Ag</i>–ZnO nanocomposite possessed excellent visible light photocatalytic activity for the degradation of methyl orange, methylene blue, and 4-nitrophenol. Electrochemical impedance spectroscopy and linear scan voltammetry under dark and visible light irradiation confirmed the enhanced visible light activity of the <i>Ag</i>–ZnO as photocatalyst and photoelectrode. These results suggest that Ag nanoparticles induced visible light photocatalytic degradation and enhanced the visible light activity of the photoelectrodes by minimizing the recombination of photogenerated electrons and holes, thereby extending the response of pure ZnO to visible light

α‑Glucosidase Inhibitory Activity and Cytotoxicity of CeO₂ Nanoparticles Fabricated Using a Mixture of Different Cerium Precursors

A mixture of three distinct cerium precursors (Ce­(NO3)3·6H2O, CeCl3·7H2O, and Ce­(CH3COO)3·H2O) was used to prepare cerium oxide nanoparticles (CeO2 NPs) in a polyol-mediated synthesis. Different ratios of diethylene glycol (DEG) and H2O were utilized in the synthesis. The properties of the synthesized CeO2 NPs, such as structural and morphological properties, were investigated to observe the effect of the mixed cerium precursors. Crystallite sizes of 7–8 nm were obtained for all samples, and all synthesized samples were confirmed to be in the cubic phase. The average particle sizes of the spherical CeO2 were between 9 and 13 nm. The successful synthesis of CeO2 can also be confirmed via the vibrational band of Ce–O from the FTIR. Antidiabetic properties of the synthesized CeO2 NPs were investigated using α-glucosidase enzyme inhibition assay, and the concentration of the synthesized CeO2 NPs was varied in the study. The biocompatibility properties of the synthesized CeO2 NPs were investigated via cytotoxicity tests, and it was found that all synthesized materials showed no cytotoxic properties at lower concentrations (62.5–125 μg/mL)

Biogenic Fabrication of Au@CeO₂ Nanocomposite with Enhanced Visible Light Activity

This study reports a biogenic approach to the synthesis of Au@CeO₂ nanocomposite using electrochemically active biofilms (EABs) in water under normal pressure and 30 °C. This work presents the results of extensive morphological, structural, optical, visible light photoelectrochemical and photocatalytic studies of Au@CeO₂ nanocomposite. The presence of a large number of interfaces between Au nanoparticles and CeO₂ for charge transfer is believed to play a key role in enhancing the optical and visible light photoelectrochemical and photocatalytic performance of Au@CeO₂ nanocomposite. The enhanced visible light degradation of methyl orange and methylene blue by Au@CeO₂ nanocomposite was much higher than that by pure CeO₂. The reusability, stability, and other results suggests that the Au@CeO₂ nanocomposite could be exploited as potential candidates for visible light photocatalysis, photovoltaic, and photoelectrochemical devices