Visible light-driven photocatalytic activity of wide band gap ATiO3 (A = Sr, Zn and Cd) perovskites by lanthanide doping and the formation of a mesoporous heterostructure with ZnS QDs.

Charge carrier recombination and wide band gap energy are still the main challenges in the visible-light-driven photocatalytic applications of titanate perovskites, ATiO3. Herein, three strategies are rationally used to achieve a titanate-based photocatalyst with high photocatalytic performance under visible light. In the first step, SrTiO3, ZnTiO3, and CdTiO3 perovskites were synthesized and their photocatalytic activity was evaluated in the degradation of methylene blue (MB) and bisphenol A (BPA). Then, a dysprosium cation (Dy3+) was doped into an ATiO3 crystalline lattice. Systematic investigations indicate that Dy doping in SrTiO3 and CdTiO3 extends the ligand to metal charge transfer absorption edge to visible wavelengths leading to the activation of doped perovskites under visible light. Higher visible-light-driven photocatalytic performance (73.29% for MB and 52.57% for BPA) and higher total organic carbon (TOC) removal (59.20% for MB and 39.53% for BPA) have been achieved by Dy doped CdTiO3 compared to other photocatalysts. Finally, we prepared a Dy-CdTP/ZnS QD mesoporous type-II heterostructure by the in situ growth of ZnS QDs on a flower-like Dy-CdTP. This design accelerates the separation and transfer of photogenerated electron-hole pairs. The surface area of the Dy-CdTP/ZnS QD heterostructure was ∼11.6 times greater than that of Dy-CdTP, offering a large surface area for the adsorption of organics, and abundant active sites for photocatalytic degradation. Taking advantage of the large surface area and considerable suppressing of the charge carrier recombination, the optimized Dy-CdTP(0.6)/ZnS QD photocatalyst exhibits excellent and stable performance for the degradation of MB (98.25%) and BPA (89.12%) with their considerable mineralization under visible light.

Non-Calcined Layer-Pillared Mn0.5Zn0.5 Bimetallic-Organic Framework as a Promising Electrocatalyst for Oxygen Evolution Reaction.

Electrocatalytic generation of oxygen is of great significance for sustainable, clean, and efficient energy production. Multiple electron transfer in oxygen evolution reaction (OER) and its slow kinetics represent a serious hedge for efficient water splitting, requiring the design and development of advanced electrocatalysts with porous structures, high surface areas, abundant electroactive sites, and low overpotentials. These requisites are common for metal-organic frameworks (MOFs) and derived materials that are promising electrocatalysts for OER. The present work reports on the synthesis and full characterization of a heteroleptic 3D MOF, [Zn2(µ4-odba)2(µ-bpdh)]n·nDMF (Zn-MUM-1), assembled from 4,4'-oxydibenzoic acid and 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (bpdh). Besides, a series of heterometallic MnZn-MUM-1 frameworks (abbreviated as Mn0.5Zn0.5-MUM-1, Mn0.66Zn0.33-MUM-1, and Mn0.33Zn0.66-MUM-1) was also prepared, characterized, and used for the fabrication of working electrodes based on Ni foam (NF), followed by their exploration in OER. These noble-metal-free and robust electrocatalysts are stable and do not require pyrolysis or calcination while exhibiting better electrocatalytic performance than the parent Zn-MUM-1/NF electrode. The experimental results show that the Mn0.5Zn0.5-MUM-1/NF electrocatalyst features the best OER activity with a low overpotential (253 mV at 10 mA cm-2) and Tafel slope (73 mV dec-1) as well as significant stability after 72 h or 6000 cycles. These excellent results are explained by a synergic effect of two different metals present in the Mn-Zn MOF as well as improved charge and ion transfer, conductivity, and stability characteristics. The present study thus widens the application of heterometallic MOFs as prospective and highly efficient electrocatalysts for OER.

Improving photocatalytic activity of the ZnS QDs via lanthanide doping and photosensitizing with GO and g-C3N4 for degradation of an azo dye and bisphenol-A under visible light irradiation.

In this research, insertion of Gd ions (2 wt%) into the crystalline lattice of the ZnS QDs enhanced the photocatalytic activity of the QDs. In addition, the influence of graphene oxide (GO) and graphitic carbon nitride (g-C3N4) was assessed on the photocatalytic activity of the ZnS QDs through degradation of acid red 14 (AR14) and bisphenol-A (BA) under visible light. Higher photocatalytic degradation efficiency (97.1% for AR14 and 67.4% for BA within 180 min) and higher total organic carbon (TOC) removal (67.1% for AR14 and 59.2% for BA within 5 h) was achieved in the presence of ZnS QDs/g-C3N4 compared with ZnS QDs/GO nanocomposite. Finally, the Gd-doped ZnS QDs were hybridized with g-C3N4 as optimal support to fabricate a potent visible-light-driven photocatalyst for the decomposition of organic contaminants. The maximum photocatalytic degradation of 99.1% and 80.5% were achieved for AR14 and BA, respectively, in the presence of Gd-doped ZnS QDs/g-C3N4 nanocomposite. The photosensitization mechanism was suggested for the improved photocatalytic activity of the ZnS QDs/GO, ZnS QDs/g-C3N4, and Gd-doped ZnS QDs/g-C3N4 nanocomposites under visible light.

Sonochemical Synthesis, Characterization and Optical Properties of Tb-Doped CdSe Nanoparticles: Synergistic Effect between Photocatalysis and Sonocatalysis.

In this study, Tb-doped CdSe nanoparticles with variable Tb3+ content were synthesized by a simple sonochemical technique. The synthesized nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and powder X-ray diffraction (XRD). The sono-photocatalytic activities of the as-prepared specimens were assessed for the degradation of Reactive Black 5. The experimental results show that the sono-photocatalytic process (85.25%) produced a higher degradation percentage than the individual sono- (22%) and photocatalytic degradation (8%) processes for an initial dye concentration and Tb-doped CdSe dosage of 20 mg/L and 1 g/L, respectively. Response surface methodology (RSM) was utilized to assess model and optimize the impacts of the operational parameters, namely, the Tb3+ content, initial dye concentration, catalyst dosage, and time. The addition of benzoquinone results in remarkably inhibited degradation and the addition of ammonium oxalate reduced the removal percentage to 24%. Superoxide radicals and photogenerated holes were detected as the main oxidative species.

Screening of pectinase-producing bacteria from farmlands and optimization of enzyme production from selected strain by RSM.

Pectinolytic enzymes that catalyze the breakdown of substrates containing pectin are widespread. Pectinases have potential applications in various industries, including food, animal feed, textile, paper, and fuel. In this study, one hundred bacterial isolates were collected from Marand city farmlands (Azarbaijan-E-Sharqi, Iran) and screened by MP medium on the base of pectinase activity considering the significance of pectinases. The results depicted that three isolates showed the most pectinase activity (more massive halo). The biochemical and molecular test results showed that the three screened bacteria were Enterobacter and named Enterobacter sp. MF41, Enterobacter sp. MF84, and Enterobacter sp. MF90. Enterobacter sp. MF84 had the largest halo, so this strain was selected for the study of its produced pectinase. The results exhibited that the produced enzyme has optimum temperature and pH for activity at 30 °C and in 9, respectively. Finally, the enzyme production by Enterobacter sp. MF84 is optimized using response surface methodology (RSM) considering four factors (NH4Cl, K2HPO4, pectin, and incubation time) as variables. The results showed that the optimization procedure increased the enzyme production up to 12 times (from 1.16 to 14.16 U/mg). The Pareto analysis revealed that ammonium chloride has a significant role in decreasing the enzyme production, probably by inducing the nitrification pathway enzymes in the presence of organic nitrogen in Enterobacter sp. MF84.

Fe0 nanoparticles improve physiological and antioxidative attributes of sunflower (Helianthus annuus) plants grown in soil spiked with hexavalent chromium.

Contamination of agricultural land by chromium (Cr) can inhibit physiological and biochemical processes in plants, leading to reduced crop productivity and food/feed safety. Owing to their fine size, large surface area, and high adsorption affinity for metals, nanomaterials have shown a potential for phytoremediation of heavy metal-contaminated soils. Nanomaterials enhance fitness of plants under metal stress through their modifying effects on plant physiology and biochemistry. The aim of this study was to assess the performance of sunflower (Helianthus annuus) plants grown in soil spiked with hexavalent chromium (Cr IV; 0, 75 and 150 ppm) and the potential role of nano-zerovalent iron (Fe0 nanoparticles; 0, 1 and 2%) to ameliorate Cr toxicity. Results revealed that the Cr uptake decreased by increasing the concentration of Fe0 nanoparticles, causing a significant enhancement in plant morphological and physiological attributes. Treatment with Fe0 nanoparticles reduced bioaccumulation factor (BAF) (in both root and shoot tissues) and translocation factor (TF); however, the magnitude of BAF and TF decreased significantly by increasing the level of Cr(VI). Chromium stress increased the activities of antioxidant enzymes, which further increased by Fe0 nanoparticle application, resulting in improved growth traits. A significant positive correlation was found between growth, BAF and TF of seedlings treated with Fe0 nanoparticles (both 1 and 2%) upon Cr exposure (75 and 150 ppm). The results demonstrated the potential of Fe0 nanoparticles to improve performance of sunflower plants under Cr toxicity through reducing their Cr uptake, which was accompanied by enhanced activity of detoxification enzymes (SOD, CAT, POX, and APX) in cells.