Spin-trapping Experiments Research Articles

Fe, Mn-Prussian blue analogue@MXene composites for efficient photocatalytic peroxydisulfate-activated degradation of tetracycline hydrochloride and photoelectrochemical desalination

The utilization of wastewater or saline as a source of clean and safe freshwater is a potential solution to address water pollution and scarcity. In this study, we synthesized a composite material, i. e. Fe, Mn-Prussian blue analogue@MXene, which is highly responsive to visible light and serves as an innovative activator for peroxydisulfate (PDS) in the degradation of tetracycline hydrochloride (TCH). The FeMn-PBA@MXene-0.30 composite, with its unique metal-organic framework (MOF) structure, exhibited excellent photocatalytic activity in the degradation of TCH by activating PDS through dual redox cycles of Mn(II)–C≡N–Fe(III) and Mn(III)–C≡N–Fe(II). A remarkable 93.41% removal of TCH can be achieved at a concentration of 30 mg·L−1 within 120 min. The presence of MXene in the composite may facilitate the efficient electron transportation owing to its excellent conductivity. The influences of various reaction conditions are also investigated, such as the concentration of potassium persulfate (KPS), TCH concentration, and solution pH value. Electron spin resonance (ESR) analysis and trapping experiments revealed the presence of reactive species, including 1O2, ∙OH, and h+, in the FeMn-PBA@MXene-0.30/visible light/PDS system. Furthermore, we demonstrated the application of the FeMn-PBA@MXene-0.30 composite as the photoanode of a solar-assisted photoelectrochemical desalination (SA-PED) device, which combines the TCH degradation with photoelectrochemical desalination. This novel approach enabled simultaneous degradation and desalination, resulting in a significant reduction of 4000-ppm brine to 240 ppm (lower than the freshwater threshold of 500 ppm), with a salt removal efficiency (SRE) of 94.00%. Meanwhile, the degradation rate of TCH (900 mg·L−1) reached up to 98.91% under visible light irradiation. This work not only provides valuable insights into the development of PDS-activated catalysts but also explores new avenues for the multifunctional application of photocatalysts in addressing water pollution and scarcity.

Efficient degradation of ciprofloxacin by a flower-spherical Bi2MoO6/BiOCl Z-type heterojunction photocatalyst enriched with oxygen vacancies

Ciprofloxacin (CIP) is difficult to degrade naturally, for example by microorganisms, and will persist in water bodies for a long period of time, seriously jeopardizing the ecological environment and human health. Photocatalysis has high practical application value as a green and efficient technology. However, the photogenerated electrons and holes of the photocatalysts are prone to complexation, which limits the degradation efficiency of photocatalysis. Therefore, in this work, spherical Bi2MoO6/BiOCl (OVs-BMO/BOC) Z-type heterojunction photocatalysts enriched with oxygen vacancies (OVs) were successfully synthesized by a hydrothermal-calcination method. A series of characterizations showed that the OVs-BMO/BOC photocatalysts could perform Z-type charge transfer, which increased the visible light response range and improved the separation efficiency of photogenerated electrons and holes, thus improving the degradation efficiency of CIP. Under visible light, the removal efficiency of OVs-BMO/BOC composites for CIP could reach 97.40% at 120 min. It has a quasi-primary rate constant of 0.03008, which is 4.1, 3.48, and 2.19 times higher than that of monomeric BOC, BMO, and BMO/BOC, respectively. Meanwhile, the good stability of OVs-BMO/BOC was verified, and its degradation efficiency could still reach 87.80% after four cycles. Finally, electron spin resonance analysis and trapping experiments were carried out, which demonstrated that a large number of OVs were produced by the BMO/BOC composite photocatalyst generated by calcination, and also identified that the OVs-BMO/BOC produced active substances (•OH, h+, and •O2−), which revealed the mechanism of degradation of CIP by the OVs-BMO/BOC. Our study provides a new way of thinking to achieve efficient elimination of antibiotics from wastewater.

Unveiling the metallic size effect on O2 adsorption and activation for enhanced electro-Fenton degradation of aromatic compounds

Metal-atom-modified nitrogen-doped carbon materials (M-N-C) have emerged as promising candidates for electro-Fenton degradation of pollutants. Nonetheless, a comprehensive exploration of size-dependent M-N-C catalysts in the electro-Fenton process remains limited, posing challenges in designing surface-anchored metal species with precise sizes. Herein, a heterogeneous-homogeneous coupled electro-Fenton (HHC-EF) system was designed and various M-N-C catalysts anchored with Co single atoms (CoSA-N-C), Co clusters (CoAC-N-C), and Co nanoparticles (CoNP-N-C) were successfully synthesized and employed in an HHC-EF system. Intriguingly, CoAC-N-C achieved outstanding removal efficiencies of 99.9% for BPA and RhB within 10 and 15 min, respectively, with the fastest reaction kinetics (0.70 min−1 for BPA and 0.34 min−1 for RhB). Electron spin resonance and trapping experiments revealed that·OH played a crucial role in the HHC-EF process. Moreover, experiments and theoretical calculations revealed that the unique metallic size effect facilitate the in-situ electro-generation of H2O2. Specifically, the atomic interaction between neighboring Co atoms in clusters enhanced O2 adsorption and activation by strengthening the Co-N bond and transforming O2 adsorption configuration to the Yeager-type. This study provides valuable insights that could inspire the size-oriented metal-based catalyst design from the perspective of the potential atomic distance effect.

Photoactivable alizarin and eugenol-based materials for antibacterial applications

We report herein the design of a new visible-light epoxy-based alizarin photosensitizer (AE) of iodonium salt (Iod) for the cationic polymerization (CP) of epoxidized eugenol monomers under visible-light irradiation. The combination of AE and Iod demonstrates highly efficient photoinitiating properties under air. As highlighted by fluorescence, laser flash photolysis (LFP) and electron paramagnetic resonance spin-trapping (ESR ST) experiments, AE acts as an electron donating molecule, and reacts with Iod under light exposure through its excited singlet and triplet states via a photoinduced electron transfer reaction, producing thus protonic acids, H+, able to initiate CP. Also, we demonstrate by EPR ST that the addition of diepoxy eugenol monomer may lead to the formation of reactive radical species which may be oxidized by Iod to form cationic species. Thus, new bio-based and photoactivable materials were designed by cationic photopolymerization with the use of alizarin-based photosensitizer and eugenol derived monomers. By tuning the weight proportion of eugenol derived epoxy monomers (mono- (EE) and di-epoxidized (EdE) eugenol), we can modulate the thermal and mechanical properties of the resulting materials. The new AE-based materials have demonstrated two interesting properties: first, the presence of EE in the polymer network has considerably decreased the number of colony forming units (CFUs) at the surface of materials whatever the bacterial strains used, and these samples demonstrate photoactivable properties as they produce, under visible-light irradiation, singlet oxygen, a biocide agent against bacteria. Interestingly, the irradiation of the AE/Iod/EE(50)/EdE(50) materials lead to a tremendous decrease of the number of E. coli and S. aureus CFUs at their surface. A reduction by 100% of the bacterial adhesion is observed upon visible-light exposure.

Dopant-driven recombination delay and ROS enhancement in nanoporous Cd1-xCuxS heterogeneous photocatalyst for the degradation of DR-23 dye under visible light irradiation

Developing an efficient heterogeneous photocatalyst for environmental remediation and treatment strategies using visible light harvesting processes is promising but challenging. Herein, Cd1-xCuxS materials have been synthesized and characterized by precise analytical tools. Cd1-xCuxS materials exhibited excellent photocatalytic activity for direct Red 23 (DR-23) dye degradation in visible light irradiation. The operational parameters, like dopant concentration, photocatalyst dose, pH, and initial concentration of dye were investigated during the process. The photocatalytic degradation process follows pseudo-first-order kinetics. As compared to other tested materials, 5% Cu doped CdS material revealed superior photocatalytic performance for the degradation of DR-23 (k = 13.96 × 10−3 min−1). Transient absorption spectroscopy, EIS, PL, and transient photocurrent indicated that adding copper to the CdS matrix improved the separation of photo-generated charge carriers by lowering the recombination rate. Spin-trapping experiments recognized the photodegradation primarily based on secondary redox products, i.e., hydroxyl and superoxide radicals. According to by Mott-Schottky curves, photocatalytic mechanism and photo-generated charge carrier density were elucidated regarding dopant-induced valence and conduction bands shifting. Thermodynamic probability of radical formation in line with the altered redox potentials by Cu doping has been discussed in the mechanism. The identification of intermediates by mass spectrometry study also showed a plausible breakdown mechanism for DR-23. Moreover, samples treated with nanophotocatalyst displayed excellent results when tested for water quality metrics such as DO, TDS, BOD, and COD. Developed nanophotocatalyst shows high recyclability with superior heterogeneous nature. 5% Cu-doped CdS also exhibit strong photocatalytic activity for the degradation of colourless pollutant bisphenol A (BPA) under visible light (k = 8.45 × 10−3 min−1). The results of this study offer exciting opportunities to alter semiconductors' electronic band structures for visible-light-induced photocatalytic activity for wastewater treatment.

In Situ Synthesis of Bi2MoO6/Bi2SiO5 Heterojunction for Efficient Degrading of Persistent Pollutants.

Photocatalytic degradation is an environmentally friendly way to eliminate environmental pollution. Exploring a photocatalyst with high efficiency is essential. In the present study, we fabricated a Bi2MoO6/Bi2SiO5 heterojunction (BMOS) with intimate interfaces via a facile in situ synthesis method. The BMOS had much better photocatalytic performance than pure Bi2MoO6 and Bi2SiO5. The sample of BMOS-3 (3:1 molar ratio of Mo:Si) had the highest removal efficiency by the degradation of Rhodamine B (RhB) up to 75% and tetracycline (TC) up to 62% within 180 min. The increase in photocatalytic activity can be attributed to constructing high-energy electron orbitals in Bi2MoO6 to form a type II heterojunction, which increases the separation efficiencies of photogenerated carriers and transfer between the interface of Bi2MoO6 and Bi2SiO5. Moreover, electron spin resonance analysis and trapping experiments showed that the main active species were h+ and •O2- during photodegradation. BMOS-3 maintained a stable degradation capacity of 65% (RhB) and 49% (TC) after three stability experiments. This work offers a rational strategy to build Bi-based type II heterojunctions for the efficient photodegradation of persistent pollutants.

Enhanced Plasmonic Photocatalysis of Au-Decorated ZnO Nanocomposites

The rapid development of technological processes in various industrial fields has led to surface water pollution with different organic pollutants, such as dyes, pesticides, and antibiotics. In this context, it is necessary to find modern, environmentally friendly solutions to avoid the hazardous effects on the aquatic environment. The aim of this paper is to improve the photocatalytic performance of zinc oxide (ZnO) nanoparticles by using the plasmonic resonance induced by covering them with gold (Au) nanoparticles. Therefore, we evaluate the charge carriers’ behavior in terms of optical properties and reactive oxygen species (ROS) generation. The ZnO-Au nanocomposites were synthesized through a simple chemical protocol in multiple steps. ZnO nanoparticles (NPs) approximately 20 nm in diameter were prepared by chemical precipitation. ZnO-Au nanocomposites were obtained by decorating the ZnO NPs with Au at different molar ratios through a reduction process. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) confirmed the simultaneous presence of hexagonal ZnO and cubic Au phases. The optical investigations evidenced the existence of a band-gap absorption peak of ZnO at 372 nm, as well as a surface plasmonic band of Au nanoparticles at 573 nm. The photocatalytic tests indicated increased photocatalytic degradation of the Rhodamine B (RhB) and oxytetracycline (OTC) pollutants under visible light irradiation in the presence of ZnO-Au nanocomposites (60–85%) compared to ZnO NPs (43%). This behavior can be assigned to the plasmonic resonance and the synergetic effects of the individual constituents in the composite nanostructures. The spin-trapping experiments showed the production of ROS while the nanostructures were in contact with the pollutants. This study introduces new strategies to adjust the efficiency of photocatalytic devices by the combination of two types of nanostructures with synergistic functionalities into one single entity. ZnO-Au nanocomposites can be used as stable photocatalysts with excellent reusability and possible industrial applications.

Modulating Photochemical Properties to Enhance the Stability of Electronically Dimmable Eye Protection Devices†.

The study evaluates compatibility of stabilizers with dye doped liquid crystal (LC) scaffolds that are used in electronically dimmable materials. The photodegradation of the materials was investigated and suitable stabilizers were evaluated to slow the degradation process. Various types of benzotriazole-based stabilizers were evaluated for stabilizing the liquid crystals. Based on spin trapping experiments, radicals generated upon UV exposure is likely responsible for the degradation of the system. The radical generation is competitively inhibited by the addition of stabilizers.

Understanding the Photocatalytic Activity of Sodium Hexatitanate Nanoparticles for Pollutants Degradation: A Spectroscopic Insight

Sodium hexatitanate (Na2Ti6O13) nanoparticles have been synthesized by the hydrothermal method with microwave and conventional heating, after which their photocatalytic properties toward an azo dye pollutant degradation have been investigated. Insights into the dynamics and reactivity of the species involved in the photocatalytic mechanism of the (Na2Ti6O13) samples were precisely investigated, for the first time, by X-band electron paramagnetic resonance (EPR) spectroscopy under different experimental conditions. X-ray diffraction structural analysis revealed that all samples crystallized in a monoclinic C2/m structure, with different short-range structural order according to the employed heating, as indicated by Raman. Field-emission scanning electron microscopy and transmission electron microscopy results revealed the formation of rod- and fiber-like nanoparticles with different diameters and lengths. EPR measurements indicated the presence of different Ti3+ point defects and F centers in the samples. X-ray photoelectron spectroscopy analysis proved the presence of oxygen-related defects, but no Ti3+ was detected on the surface. Spin trapping experiments monitored the generation of hydroxyl (OH·) radicals over UV-irradiation time. Various parameters contribute to the photocatalytic activity of the samples; however, the type of defect and particle morphology appeared as key factors for enhanced efficiency. Our study provides significant information about paramagnetic defects in Na2Ti6O13 materials and their role in photocatalysis to design other Ti-based photocatalysts.

Oxidative carbonylation of methane to acetic acid on an Fe-modified ZSM-5 zeolite

Direct catalytic conversion of methane under mild conditions is beneficial but challenging. Herein, we report a direct co-conversion of methane, carbon monoxide, and hydrogen peroxide into acetic acid, catalyzed by Fe/ZSM-5 (0.25) zeolite under mild conditions. The highest reported acetic acid space-time yield of ∼12.01 mmol gcat−1 h−1 with an optimal selectivity of 63.2% is achieved at 50 °C. This relatively high yield is ascribed to the mononuclear Fe3+ species. 13C-Tracking experiments revealed that the methyl and carbonyl groups of acetic acid originate from methane and carbon monoxide, respectively. Spin-trapping experiments indicated that ∙OH and ∙CH3 radicals are involved in the reaction. In situ Raman analysis suggested that –Fe–OCH3 species is the possible intermediate. Overall, our method is greener, and our catalyst is more economical than those currently used in the industrial process. Therefore, we expect a pilot-scale test to determine the possibility as an industrial alternative.

Flavonol dioxygenation catalysed by cobalt(II) complexes supported with 3N(COO) and 4N donor ligands: a comparative study to assess the carboxylate effects on quercetin 2,4-dioxygenase-like reactivity.

Two new cobalt(II)-acetato complexes, [CoII(L3NCOO)(OAc)]·0.5H2O (1OAc·0.5H2O) and [CoII(L4N)(OAc)](PF6) (2OAc(PF6)), were synthesised using ligands L3NCOO- (Li+L3NCOO- = lithium 2-(benzyl((6'-methyl-[2,2'-bipyridin]-6-yl)methyl)amino)acetate) and L4N (N-benzyl-1-(6'-methyl-[2,2'-bipyridin]-6-yl)-N-(pyridin-2-ylmethyl)methanamine), respectively, to mimic the functional activity of cobalt(II)-quercetin-2,4-dioxygenase (CoII-2,4-QD). Additionally, Co(II)-flavonolato ternary complexes, [CoII(L3NCOO)(fla)]·H2O (1fla·H2O) and [CoII(L4N)(fla)](PF6) (2fla(PF6)), were synthesised as enzyme-substrate models. All four complexes were thoroughly characterised by elemental analyses and spectroscopic methods. Structural characterisation was performed for 1OAc·0.5H2O, 2OAc(PF6)·CH2Cl2 and 2fla+ with a perchlorate counter anion, 2fla(ClO4)·1.5H2O. Furthermore, density functional theory (DFT) calculations, time-dependent DFT (TD-DFT) and molecular orbital (MO) analysis were performed for the flavonolato adducts 1fla and 2fla+. The catalytic activities of complexes 1OAc·0.5H2O and 2OAc(PF6) in the oxygenative degradation of flavonol (multiple-turnover reactions) were investigated at 70 °C in DMF to determine the effect of the carboxylate substituent over a pyridyl donor residue on reactivity. Complex 1OAc·0.5H2O showed a higher catalytic rate than complex 2OAc(PF6). The same reactivity order was observed for single-turnover dioxygenation reactions with ternary complexes (1fla > 2fla+). The formation constants (Kf) of 1fla and 2fla+ species are comparable, implying that catalyst-substrate adduct formation occurs in similar amounts for both catalytic reactions. Therefore, the Kf values have a similar impact on reactivities. However, the oxidation potential of the bound fla-/fla˙ couple in 1fla is considerably lower than that in 2fla+. DFT calculations predicted that the negatively charged carboxylate group of ligand L3NCOO- determines the higher reactivity of 1fla with dioxygen by decreasing the oxidation potential of the bound fla-/fla˙ couple. During the dioxygenation process, the reactive Co(II)-bound flavonoxy radical was generated via single-electron transfer from the coordinated fla- to dioxygen, simultaneously forming a superoxide ion. The anionic carboxylate group improves the stability of the bound flavonoxy radical by providing substantial electron density to the electron-deficient fla˙ through the Co(II) centre, allowing the reactive fla˙ species to accumulate at an optimal concentration for effective catalysis. EPR spectroscopy successfully detected the cobalt-bound fla˙ species formed through the dioxygenation of 1fla. NBT2+ and EPR spin-trapping experiments confirmed superoxide formation during the dioxygenation process. So, the present work describes CoII-2,4-QD model studies and clarifies the function of carboxylate in quercetinase-like reactivity.

Integrated adsorption and photodegradation of tetracycline by bismuth oxycarbonate/biochar nanocomposites

Adsorption and photodegradation are two widely studied wastewater treatment technologies. In this work, we have firstly prepared the bismuth oxycarbonate (Bi2O2CO3) and biochar nanocomposites for synergistic adsorption-photodegradation of tetracycline (TC). It was found that Bi2O2CO3 and biochar composites exhibited stronger adsorption capacity and photocatalytic activity compared to Bi2O2CO3. Among them, Bi2O2CO3/2.5 wt% biochar possessed the highest adsorption capacity for TC (173.0 mg/L) and the best combined removal rate of TC (84.7 %) in 60 min by adsorption and photodegradation, which were 1.9 times and 1.5 times that of Bi2O2CO3, respectively. The biochar in the composite increased the specific surface area, promoted the adsorption of TC, facilitated charge transfer capability, thereby enhanced the photocatalytic activity of composites. The effects of experimental parameters (temperature, co-existing ions, and initial pH) on TC degradation were examined. Electron spin resonance (ESR) and trapping experiments of free radical confirmed that 1O2, •O2− and h+ were the main species in photocatalytic degradation. The potential degradation pathways were proposed based on liquid chromatograph mass spectrometer (LC-MS) test of the intermediates of TC degradation. It is hoped that this work not only represents the significantly importance of biochar in photocatalytic wastewater treatment, but also promotes further interests in design synergistic adsorption-photodegradation materials.

Lag Time Determinations in Beer Samples. Influence of Alcohol and PBN Concentration in EPR Spin Trapping Experiments

The beers’ lag time measured with the PBN (N-t-Butyl-α-phenylnitrone) spin trapping experiments coupled with EPR spectroscopy is related to their antioxidant capacity and shelf life. The effect on the lag time of the alcohol content of the beer (starting values, 9 and 13%) and PBN concentration (50 or 200 mM) was analyzed on three samples, a pilsner, a strong lager, and a blonde Ale heated at 60 °C to trigger the production of the 1-hydroxyethyl radical. The lag time was determined only for the strong lager beer, with the values depending on the experimental conditions, being higher when PBN had a lower concentration. The antioxidant activity of the three beers gave the following values: 0.9089 mL pilsner beer/mg DPPH, 0.8510 mL strong lager beer/mg DPPH, and 0.7184 mL blonde Ale beer/mg DPPH, indicating that the unsuccessful determination of the lag time was not due to stale beers. The EPR intensity of the PBN adduct after 150 min (I150) and the area under the curve (AUC) were also measured and related to the oxidative stability of beers. Further studies are needed to verify the influence of the heating temperature in samples that do not show a lag time at 60 °C.

Pd Nanoparticles Supported on N-Doped TiO2 Nanosheets: Crystal Facets, Defective Sites, and Metal-Support Interactions Boost Reforming of Formaldehyde Solution for Hydrogen Production.

To produce H2 from formaldehyde (HCHO), dehydrogenation offers an alternative approach to future hydrogen-based energy sources, but the unsatisfactory efficiency hinders its practical application. Here, ultrafine Pd nanoparticle (NP) decorated N-doped TiO2 nanosheets exposed with (001) facet catalysts (denoted as Pd/TiO2-x) have been prepared and exhibit superior H2 production performance from alkaline HCHO aqueous solution. Under our current conditions, the Pd/TiO2-x catalyst with a Pd loading of 1 wt % exhibits a H2 production rate of 183.77 mL/min/g, which is 1.75 and 3.66 times that of Pd/TiO2 and Pd NPs, respectively. Based on the results of Fourier transform infrared spectroscopy (FTIR), Raman, and liquid-phase electron paramagnetic resonance (EPR) spin-trapping experiments, the excellent H2 generation of Pd/TiO2-x can be attributed to the synergistic contribution among the reactive crystal facets, defective sites, and metal-support interactions in boosting the breakage of C-H bonds in HCHO, dissociation of H2O, and ultimately the formation of H2. This work is expected to provide a paradigm of an efficient catalyst to produce H2 from HCHO/H2O solution.

Peroxide stabilizers remarkably increase the longevity of thermally activated peroxydisulfate for enhanced ISCO remediation

Thermally activated peroxydisulfate In Situ Chemical Oxidation (TAP-ISCO) is often applied for the remediation of soil-sorbed hydrophobic organic contaminants (HOCs) and nonaqueous phase liquids (NAPLs), which act as long-term sources of groundwater contamination. TAP-ISCO benefits from improved desorption/dissolution of organic contaminants into the aqueous phase and efficient activation of peroxydisulfate at elevated temperatures, but the primary limitation of TAP-ISCO is the short lifetime of peroxydisulfate (therefore the availability of reactive radical species). To resolve this problem, coupling of peroxide stabilizers with TAP were tested. The compatibility of seven representative commercial organic and inorganic peroxide stabilizers, including sodium stannate, trisodium phosphate, sodium pyrophosphate, sodium silicate, sodium citrate, ethylene diamine tetra methylene phosphonic acid and ethylenediaminetetraacetic acid disodium salt, with TAP in aqueous solutions and solutions containing goethite or soil particles were first studied. The effects of stabilizers on the formation, distribution and reactivity of reactive oxygen species were then investigated through electron paramagnetic resonance (EPR) spin-trapping experiments using 5,5-dimethyl-1-pyrroline-N-oxide, chemical probe experiments using anisole, nitrobenzene and hexachloroethane, and biphasic trichloroethylene (TCE) dense nonaqueous phase liquids (DNAPLs) TAP-ISCO mimicking experiments. The results indicate that organic stabilizers significantly accelerate peroxydisulfate decomposition at both ambient and elevated temperatures. In contrast, inorganic stabilizers can markedly increase peroxydisulfate longevity by suppressing the acid-catalyzed peroxydisulfate decomposition, quenching radical-chain acceleration, and sequestering transition metal species. In addition, TAP systems containing inorganic stabilizers can effectively generate a variety of reactive radical species, including SO4•−, HO•, and O2•−, and improve the oxidation of anisole and nitrobenzene, though suppressing the reduction of hexachloroethane to some extent. Especially, suitable inorganic stabilizers (e.g., trisodium phosphate) can effectively improve TAP oxidation of TCE DNAPL while suppressing peroxydisulfate decomposition. Overall, this study provides the fundamental basis of coupling TAP-ISCO with peroxide stabilizers.

Metal-free modification of porphyrin-based porous organic polymers for effective photocatalytic degradation of bisphenol A in water

Porphyrin based photocatalysts have demonstrated exciting features, such as outstanding photoelectric properties, good photothermal stability, and structural diversity. Meanwhile, hydrophilic porphyrin is easily dispersed in water, increasing photocatalyst contact with pollution while also reducing the distance of carrier transport. In this study, porphyrin-based porous organic polymers (POPs), TEPP-F-TBT, was successfully fabricated for degradation of bisphenol A (BPA) using Sonogashira coupling. To enhance the dispersion of TEPP-F-TBT, modification of TEPP-F-TBT by 3-mercapto-1-propanesulfonic acid sodium was performed using the thiol-alkyne click reaction. Subsequently, under illumination, the modified polymer TEPP-F-TBT-S degrades more than 99.0% of 10 ppm BPA within 30 min, but TEPP-F-TBT can only degrade 25% of 10 ppm BPA under the same conditions. A possible mechanism of photocatalytic degradation of BPA was speculated using characterizations, such as electron spin resonance and trapping experiments. Our study presents a green approach for modifying POPs to design and synthesize organic photocatalysts with outstanding performance.

Z-scheme g-C3N4/ZnS heterojunction photocatalyst: One-pot synthesis, interfacial structure regulation, and improved photocatalysis activity for bisphenol A

Taguchi experiment was used to optimize the experimental conditions, including the dosage of precursor and calcination temperature, in order to controllably synthesize g-C3N4/ZnS heterojunction composites from zinc acetate (Zn(OAc)2) and thiourea (Tu) by facile one-pot annealing method. The photocatalytic activity of g-C3N4/ZnS heterojunction composites for bisphenol A (BPA) in aqueous solution was studied. The g-C3N4/ZnS composites prepared at the optimum conditions according to the results of Taguchi experiment (labeled as g-C3N4/ZnS-10) exhibited significantly improved removal rate of BPA (92.1% after 8 h), which was 7.4, 2.1 and 6.6 times higher than that of g-C3N4, ZnS and g-C3N4/ZnS-1 (the composites with the lowest photocatalytic activity in Taguchi experiment), respectively. g-C3N4/ZnS heterojunction composites was characterized by XRD, FT-IR, BET, SEM, TEM, EDS, XPS, PL, EPR, UV–vis DRS and UPS. The trapping experiment and DMPO spin-trapping experiment revealed that Superoxide radicals played a major role in the photocatalysis of BPA. The excellent photocatalytic activity of g-C3N4/ZnS-10 was mainly attributed to the synergistic effect which can create the internal driving force to enhance the light response and improve the separation/transfer efficiency of interfacial charge in Z-scheme heterojunction. The underlying photocatalytic mechanism was discussed and analyzed in details.

Electronic Coupling in 1,2,3-Triazole Bridged Ferrocenes and Its Impact on Reactive Oxygen Species Generation and Deleterious Activity in Cancer Cells

Mixed-valence (MV) binuclear ferrocenyl compounds have long been studied as models for testing theories of electron transfer and in attempts to design molecular-scale electronic devices (e.g., molecular wires). In contrary to that, far less attention has been paid to MV binuclear ferrocenes as anticancer agents. Herein, we discuss the synthesis of six 1,2,3-triazole ferrocenyl compounds for combined (spectro)electrochemical, electron paramagnetic resonance (EPR), computational, and anticancer activity studies. Our synthetic approach was based on the copper-catalyzed 1,3-dipolar azide–alkyne cycloaddition reaction and enabled us to obtain in one step compounds bearing either one, two, or three ferrocenyl entities linked to the common 1,2,3-triazole core. Thus, two series of complexes were obtained, which pertain to derivatives of 3′-azido-3′-deoxythymidine (AZT) and 3-azidopropionylferrocene, respectively. Based on the experimental and theoretical data, the two mono-oxidized species corresponding to binuclear AZT and trinuclear 3-azidopropionylferrocene complexes have been categorized as class II mixed-valence according to the classification proposed by Robin and Day. Of importance is the observation that these two compounds are more active against human A549 and H1975 non-small-cell lung cancer cells than their congeners, which do not show MV characteristics. Moreover, the anticancer activity of MV species competes or surpasses, dependent on the cell line, the activity of reference anticancer drugs such as cisplatin, tamoxifen, and 5-fluorouracil. The most active from the entire series of compounds was the binuclear thymidine derivative with the lowest IC50 value of 5 ± 2 μM against lung H1975 cancer cells. The major mechanism of antiproliferative activity for the investigated MV compounds is based on reactive oxygen species generation in cancer cells. This hypothesis was substantiated by EPR spin-trapping experiments and the observation of decreased anticancer activity in the presence of N-acetyl cysteine (NAC) free-radical scavenger.

Visible-Light-Driven Thioesterification of Aryl Halides with Potassium Thiocarboxylates: Transition-Metal Catalyst-Free Incorporation of Sulfur Functionalities into an Aromatic Ring.

Reactions of acceptor-substituted aryl iodides and bromides with potassium thiocarboxylates under white light irradiation allow for the preparation of S-aryl thioesters including synthetically versatile S-aryl thioacetates. This transition-metal and external photocatalyst-free method features extremely mild reaction conditions compared with those used in transition-metal-catalyzed protocols. Reactions proceed via the initial formation of an electron donor-acceptor (EDA) complex in the ground state, which was supported by UV-vis spectra. Electron paramagnetic resonance (EPR) spin-trapping experiments using phenyl-N-tert-butylnitrone (PBN) have revealed the radical nature of the reaction.

Selective oxidation of benzene by an iron oxide carbonaceous nanocatalyst prepared from iron perchlorate salts and hydrogen peroxide in benzene and acetonitrile

Direct benzene hydroxylation under mild conditions using hydrogen peroxide can be essential in producing phenol. A new iron oxide-carbonaceous nanocatalyst (Fe-oxide CNC) is prepared in situ using a precursor of Fe(ClO4)2 and H2O2 in benzene and CH3CN. The obtained Fe-oxide CNC can efficiently catalyze benzene oxidation to phenol using H2O2(aq) in CH3CN. The highest phenol production was achieved with the turnover number (TON) of 122 in unit iron content and selectivity of 96% at 60 °C. The catalyst was characterized by SEM, TEM, XAS, XPS, Raman, XRD, BET, and TGA techniques.Interestingly, materials identification and characterization of the Fe-oxide CNC provided evidence to support the presence of Fe2O3. In addition, the carbonaceous moieties mainly consisted of branched aliphatic hydrocarbons on the iron oxide surface, which enhance the catalytic performance for benzene oxidation to phenol. The Fe-oxide CNC can be recycled three times with comparable catalytic efficiency. Using H218O2 as an oxidant, the phenol product with highly enriched 18O-atom indicates that the reactive oxygen species (ROS) activated by H2O2(aq) is crucial for aromatic oxidation. Time-resolved spin trapping experiments displayed the formation of the intermediate adducts consisting of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and reactive oxygenated radicals. For 3‒24 h durations, higher steady-state concentrations of the oxygenated intermediates observed at 25 °C than 60 °C indicate that the catalytic oxidation of benzene mediated by Fe-oxide CNC performs much faster kinetics at 60 °C than the ambient condition.