New insight into the selective photocatalytic oxidation of RhB through a strategy of modulating radical generation

Synthesis of Silver(I) Complexes through In Situ Reactions of dppeda with dmp in the Presence of Silver Halides for Photocatalysis

Due to the unique photosensitivity of silver compounds, they exhibit good photocatalytic activity as photocatalysts in the degradation of water pollutants. However, silver compounds have poor cycling stability and are prone to decomposition and reaction under light to form metallic silver, which greatly limits their practical application. Herein, a (2-(2-(diphenylphosphaneyl)ethyl)-9-methyl-1.10-phenanthroline (PSNNP)) pincer ligand was designed for stabilizing the central metal. The in situ-formed PSNNP ligand could be readily generated in one pot with the participation of silver halides. The reaction of silver halides with dppeda (N,N,N',N'-tetra(diphenylphosphanylmethyl)ethylene diamine) in the presence of dmp (2,9-dimethyl-1,10-phenanthroline) in acetonitrile afforded complexes Ag2X2 (PSNNP)2 (complexes 1, 2) (X = Cl, Br). Single-crystal X-ray diffraction shows that the tridentate coordination of the pincer ligand provides strong binding with metal centers and leads to high stability of the pincer metal unit. The removal rate of rhodamine B (RhB) by complexes 1 and 2 can reach up to 100%, demonstrating an excellent photocatalytic degradation performance for organic dyes. The important effect of PSNNP ligands on photocatalytic properties after coordination with central metals was studied through experiments and discrete Fourier transform (DFT) calculations. The photocatalytic reaction mechanism of complexes 1 and 2 was also studied. This result provides an effective pathway for the first synthesis of PSNNP and interesting insights into photocatalytic degradation chemistry.

Performance of Ag-doped CuO nanoparticles for photocatalytic activity applications: Synthesis, characterization, and antimicrobial activity

The auto-combustion method synthesized CuO NPs and Ag/CuO NPs. The Ag/CuO NPs were analyzed using Fourier-transform infrared, X-ray diffraction, scanning electron microscope, and Energy-dispersive X-ray spectroscopy instrumental analyses. The energy band gap, as determined by DRS properties, decreases from 3.82 to 3.50 eV for pure CuO and 10% Ag/CuO NPs, respectively. The photodegradation efficiency of Rhodamine-B & Carmine by 10% Ag/CuO NPs was nearly 98.9 and 97.8%, respectively. Antimicrobial trials revealed that the antimicrobial efficacy of Ag/CuO NPs at several dosages (20, 40, 60, 80, 100, and 120 µg/mL) against human pathogens was initially assessed using the agar well-diffusion method, and then the broth dilution method. Noticeably, the minimum inhibitory concentration of Ag/CuO NPs for all pathogens ranged from 100 to 120 µg/ml, was determined. Generally, the observed minimum microbicide concentration has a wide range of Ag/CuO NPs doses, ranging from 150 to 300 µg/ml, which helps kill (99.99%) all tested pathogenic cells. The largest relative inhibitory activities (%) were recorded against Escherichia coli (81.45 ± 1.39) at 120 g/mL of Ag/CuO NPs and 100 μg/mL (80.43 ± 0.59), followed by 80 µg/mL (72.33 ± 0.82). Additionally, the lowest relative inhibitory activities (%) were monitored versus fungal cells and Gram-positive bacteria at 120 µg/mL of Ag/CuO NPs as 52.17 ± 1.49 and 53.42 ± 1.71; respectively.

A novel and stretchable carbon-nanotube/Ni@TiO2:W photocatalytic composite for the complete removal of diclofenac drug from the drinking water

We present the structural, morphological and photocatalytic properties of stretchable composites made with carbon nanotubes (CNTs), silicon rubber and Ni@TiO₂:W nanoparticles (TiWNi NPs) with average size of 37 ± 2 nm. Microscopy images showed that the TiWNi NPs decorated the surface of the CNT fibers, which are oriented in a preferential direction. TiWNi NPs presented a mixture of anatase/rutile phases with cubic structure. The performance of the TiWNi powders and stretchable composites was evaluated for the photocatalytic degradation of diclofenac (DCF) anti-inflammatory drug under ultraviolet-visible light. The results revealed that the maximum DCF degradation percentages were 34.6%, 91.9%, 97.1%, 98.5% and 100% for the CNT composite (stretched at 0%), TiWNi powders, CNT + TiWNi (stretched at 0%), CNT + TiWNi (stretched at 50%) and CNT + TiWNi (stretched at 100%), respectively. Thus, stretching the CNT + TiWNi composites was a good strategy to enhance the DCF degradation percentage from 97.1% to 100%, since stretching created additional defects (oxygen vacancies) that acted as electron sink, delaying the electron-hole recombination, and favors the DCF degradation. Raman/absorbance measurements confirmed the presence of such defects. Moreover, the reactive oxygen species (ROS) were determined by the scavenger's experiments and found that the main ROS were the ·OH and O₂^- radicals, which attacked the DCF molecules, causing their degradation. The results of this investigation confirmed that the stretchable CNT/TiWNi-based composites are a viable alternative to remove pharmaceutical contaminants from water and can be manually separated from the decontaminated water, which is unviable using photocatalytic powders.

A sustainable composite of rice-paper/BaMoO4 nanoparticles for the photocatalytic elimination of the recalcitrant 2,6-dichlorobenzamide (BAM) pesticide in drinking water and its mechanisms of degradation

This research reports the use of biodegradable and flexible composites for the removal of the 2,6-dichlorobenzamide (BAM) pesticide from drinking water. Rice paper (a biodegradable substrate) and Ag/BaMoO4 (MOBA) nanoparticles were employed to fabricate these composites. The SEM images showed that the MOBA nanoparticles with sizes of 300-800 nm decorated the surface of the biodegradable substrate and formed porous agglomerates, which have sizes of 1-3 μm. The MOBA powders were dispersed in drinking water polluted with BAM and were exposed to 4 h of UV-VIS irradiation, producing a maximum degradation of 82% for the BAM. Moreover, the flexible and biodegradable rice/MOBA composite produced a maximum removal percentage of 95% for the BAM. Also, we studied the effect of pH of the initial solution utilizing both powders and composites. From here, we found that a pH of 10 leads to a complete degradation of BAM after 4h, while a pH of 3 degraded only 37-47% of BAM for the same reaction time. According to the scavenger experiments, the •OH radical and the h+ were the main oxidizing agents for the BAM. Overall, the biodegradable photocatalytic composites are a reliable and a low-cost alternative to eliminate pesticides from the drinking water and can find application in water purification processes.

α-MnO2 Nanowire Structure Obtained at Low Temperature with Aspects in Environmental Remediation and Sustainable Energy Applications

Hydrothermally obtained α-MnO2 nanowire characterizations confirm the tetragonal crystalline structure that is several micrometers long and 20–30 nm in diameter with narrow distributions in their dimensions. The absorption calculated from diffuse reflectance of α-MnO2 occurred in the visible region ranging from 400 to 550 nm. The calculated band gap with Quantum Espresso using HSE approximation is ~2.4 eV for the ferromagnetic case, with a slightly larger gap of 2.7 eV for the antiferromagnetic case, which is blue-shifted as compared to the experimental. The current work also illustrates the transformations that occur in the material under heat treatment during TGA analysis, with the underlying mechanism. Electrochemical studies on graphite supports modified with α-MnO2 compositions revealed the modified electrode with the highest electric double-layer capacitance of 3.444 mF cm−2. The degradation rate of an organic dye—rhodamine B (RhB)—over the compound in an acidic medium was used to examine the catalytic and photocatalytic activities of α-MnO2. The peak shape changes in the time-dependent visible spectra of RhB during the photocatalytic reaction were more complex and progressive. In two hours, RhB degradation reached 97% under sun irradiation and 74% in the dark.

Enhanced Photocatalytic Oxidation of RhB and MB Using Plasmonic Performance of Ag Deposited on Bi2WO6

Visible-light-driven heterostructure Ag/Bi2WO6 nanocomposites were prepared using a hydrothermal method followed by the photodeposition of Ag on Bi2WO6. A photocatalyst with a different molar ratio of Ag to Bi2WO6 (1:1, 1:2 and 2:1) was prepared. The catalytic performance of Ag/Bi2WO6 towards the photocatalytic oxidation of rhodamine B (RhB) and methylene blue (MB) was explored. Interestingly, the Ag/Bi2WO6 (1:2) catalyst exhibited superior performance; it oxidized 83% of RhB to Rh-110 and degraded 68% of MB in 90 min. This might be due to the optimum amount of Ag nanoparticles, which supported the rapid generation and transfer of separated charges from Bi2WO6 to Ag through the Schottky barrier. An excess of Ag on Bi2WO6 (1:1 and 2:1) blocked the active sites of the reaction and did not produce the desired result. The introduction of Ag on Bi2WO6 improved the electrical conductivity of the composite and lowered the recombination rate of charge carriers. Our work provides a cost-effective route for constructing high-performance catalysts for the degradation of toxic dyes.

Efficient solar removal of acetaminophen contaminant from water using flexible graphene composites functionalized with Ni@TiO2:W nanoparticles

This work presents the morphological, structural and photocatalytic properties of flexible graphene composites decorated with Ni@TiO₂:W nanoparticles (TiNiW NPs) with an average size of 27 ± 2 nm. The TiNiW NPs were immobilized on the surface of a flexible graphene composite using a PVA-based slurry-paste (FG/TiNiW composite). The SEM study showed that the TiNiW NPs remained exposed on the surface of the FG/TiNiW composite, which benefited its photocatalytic activity. The photocatalytic performance for the degradation of acetaminophen (ACT) was evaluated using both the TiNiW powders and the FG/TiNiW composite, obtaining maximum degradation efficiencies of 100 and 86%, respectively, after 3 h under natural solar irradiation. The degradation of ACT was caused mainly by the reactive oxygen species such as OH radicals and h⁺, which was confirmed by scavenger experiments. Photoluminescence, XPS and absorbance experiments revealed that oxygen vacancy defects were created by i) doping the TiNiW NPs with W and by ii) introducing graphene into the composites. These defects enhanced the absorbance of light in the range of 400-800 nm, which in turn, promoted the photocatalytic degradation of ACT. Moreover, the reuse experiments confirmed that both the TiNiW NPs and FG/TiNiW composite were very stable for the degradation of ACT, since degradation efficiencies >82% were obtained after 4 reuse cycles for both photocatalysts. The experimental findings of this work demonstrate that the flexible TiO₂/graphene composites are a feasible option for the removal of pharmaceutical contaminants from water using natural solar irradiation.

Acid-activated carbon nitrides as photocatalysts for degrading organic pollutants under visible light

Three-dimensional (3D) carbon nitride (C₃N₄) can be used as a promising platform for visible-light-active photocatalysts because of its suitable band positions. This study reports that HNO₃ activation improves the photocatalytic activity of 3D melamine-derived C₃N₄ (MCN) materials, which degrade the organic pollutant rhodamine B (RhB). HNO₃ treatment under reflux removes the carbonaceous impurities in MCN and introduces oxygen-containing functional groups on its surface. Under visible light irradiation, the nitric acid treated MCN (NT-MCN) completely degrades RhB within 30 min. Photophysical characterizations and control experiments with radical scavengers reveal that MCN and NT-MCN follow different reaction mechanisms. Because NT-MCN exhibits a longer photoluminescence lifetime, smaller electrochemical resistance, and larger photocurrent than those of MCN, it enables a better transfer of charge carriers during the catalytic reaction.

One-pot synthesis of BiOCl nanosheets with dual functional carbon for ultra-highly efficient photocatalytic degradation of RhB

Water pollution from Rhodamine B (RhB) has become a challenging problem which human beings are urgent to confront. A high-efficiency photocatalysis system is required for the industrial application. A novel carbon doped bismuth oxychloride (C-BiOCl) composite photocatalyst with dual functional carbon was synthesized by one-pot hydrothermal process. The introduction of the carbon in the synthesis modified the morphology of BiOCl by suppressing the growing-up of the layered structures, which resulted in more active catalytic sites and shorter path of charge transfer. Moreover, the doped carbon would improve the utilization of light, and shift the band structures of the BiOCl. The as-synthesized C-BiOCl possesses a significant improvement (around 400%) on the photocatalytic degradation of RhB. Therefore, this efficient photocatalyst with dual functional carbon has been synthesized and would be regarded as a novel strategy for the design of high-performance photocatalysts.

In situ replacement of Cu-DEN: an approach for preparing a more noble metal nanocatalyst for catalytic use

The advantage of dendritic monodisperse macromolecules’ dual templating ability was useful in the formation of silica-supported copper nanoparticles Cu_n@SiO₂NPs.