Radical Trapping Research Articles

Ultrasound-assisted synthesis of a novel type-II Bi12O15Cl6/CTF-1 heterojunction for visible-light-driven photocatalytic degradation of levofloxacin: Reaction kinetics, degradation pathways, and toxicity assessment

Fluoroquinolones (FQL) are ubiquitous in aquatic environments due to their widespread use, posing a serious environmental threat. In this regard, a novel Bi12O15Cl6/CTF-1 (BTF) photocatalyst was prepared by integrating a covalent triazine framework (CTF-1) with Bi12O15Cl6 by a simple wet-impregnation method for removing levofloxacin (LFX), an FQL-based antibiotic, from an aqueous solution. Under optimal conditions, BTF (III) (comprising 20 % CTF-1) showed the highest photocatalytic activity, achieving approximately 94 % LFX (10 mg/L) degradation in 120 min under visible light with a pseudo-kinetic rate constant of 0.02072 min−1. This can be attributed to the reduced recombination rate and efficient transfer and separation of photoinduced charge carriers. The photocatalyst demonstrated remarkable stability and reusability. The radical trapping experiment revealed O2•− and h+ to be the primary active species facilitating the photocatalytic degradation of LFX. Furthermore, the seed germination test affirmed treated effluent to be non-phytotoxic and suitable for irrigation.

The one-pot synthesis of defect-rich bimetallic MOFs for efficient photocatalytic Fenton degradation of organic pollutants

The efficient and straightforward treatment of organic contaminants in water remains a significant challenge. This study presents the synthesis of a defective NH2-MIL-88Fex/Cuy photo-Fenton catalyst via a simple one-pot hydrothermal method. The incorporation of the inexpensive metal Cu enhances the valence cycles of Cu2+/Cu+ and Fe3+/Fe2+ under the photo-Fenton system, thereby compensating for the rapid consumption rate of ·OH radicals. Degradation tests demonstrated that NH2-MIL-88Fe0.5/Cu0.5 can degrade 99.99 % of methylene blue within 30 min under visible light irradiation. Free radical trapping experiments and Electron Paramagnetic Resonance (EPR) confirmed that ·OH radicals play a predominant role in the catalytic system. Density Functional Theory (DFT) calculations verified the improved binding energy of the catalyst materials following the introduction of structural defects. The degradation pathway and mechanism of methylene blue were elucidated. This study offers a novel approach for designing photo-Fenton catalysts and holds significant promise for practical applications in wastewater treatment.

Visible Light-Mediated Co(II) Catalyzed Synthesis of α,β-Epoxy Ketones by Oxidative Coupling of Alkenes and Aldehydes in Water.

A one-step, two-component visible light-mediated CoCl2·6H2O-catalyzed oxidative acylation of alkenes by aldehydes to synthesize α,β-epoxy ketone has been achieved in water at room temperature. The photocatalytic activity of Co(II) presented a remarkable achievement for synthesis of α,β-epoxy ketones from aldehydes and olefins, with a wide substrate compatibility including aromatic, heteroaromatic and aliphatic aldehydes, styrenes with both electron-donating and withdrawing groups, α-substituted styrenes, stilbene, acrylates, and even the challenging unactivated aliphatic alkenes. Mechanistic studies including radical trapping experiments, intermediate detection by GCMS, Hammett analysis, and DFT studies unveil the nature of the photocatalytic pathway.

Synthesis of Bi-BiPO4-Ag3PO4/PAN composite nanomaterial photocatalyst with the degradation performance for rhodamine B

A highly efficient visible-light-driven photocatalyst Bi-BiPO4-Ag3PO4/PAN was synthesized by electrospinning, in-situ growth, immersion and reduction methods. The prepared composites were characterized by SEM, TEM, XPS, UV–vis, FT-IR and EIS. The results showed that the loading of BiPO4 significantly improved the photocatalytic efficiency of Ag3PO4, and the photocatalytic efficiency was further improved by a certain degree of reduction. When the ratio of BiPO4 to Ag3PO4 is 8 %, the catalyst: reducing agent is 1:2 and the reduction time is 15 min, the degradation rate of rhodamine B was the highest under visible light irradiation (λ ≥ 420 nm). The rate constant of Bi-BiPO4-Ag3PO4/PAN-8 % is (0.01401 min−1) 2.56 times that of pure Ag3PO4 (0.00327 min−1). The photocatalyst also has good degradation performance for different kinds of dyes and antibiotics under visible light irradiation, which is universal and easy to recycle. Free radical trapping experiments showed that •O2− is the main active oxidant affecting the photodegradation of rhodamine B and interacts with h+ and •OH. This study not only provides a new idea for the synthesis of Ag3PO4-based photocatalysts, it is also proved that Bi-BiPO4-Ag3PO4/PAN composite is a promising photocatalyst for the treatment of organic pollutants in water.

Z-Scheme Heterojunction of Phosphorus-Doped Carbon Nitride/Titanium Dioxide: Photocatalytic Performance.

With increasingly serious environmental pollution problems, the development of efficient photocatalytic materials has become a hotspot in current research. This study focused on phosphorus-doped carbon nitride/titanium dioxide (PCT) Z-type heterojunctions, aiming to deeply investigate their photocatalytic degradation and photosensitive antimicrobial properties. A PCT Z-type heterojunction was successfully fabricated using melamine phosphate, cyanuric acid, and titanium dioxide. The structure, morphology, and optical properties of PCT Z-type heterojunctions were explored by FTIR, XRD, XPS, BET, SEM, UV-Vis DRS, TEM, EIS, and PL. A comprehensive and in-depth analysis of the structure, morphology, and optical properties of PCT Z-type heterojunctions was carried out. The photocatalytic degradation experiments revealed that PC3T Z-type heterojunctions exhibited an excellent degradation capability for methylene blue (MB) under visible light. The effect of PC3T on the adsorption-photocatalytic degradation of MB is more than 1.5 times that of a single titanium dioxide and P-doped carbon nitride. In the photosensitive antimicrobial performance study, PC3T reduced the survival rate of E. coli to 7%, after 120 min. Through free radical trapping experiments, it was shown that the hydroxyl radicals and superoxide radicals exerted an influence on the photocatalytic process. This study offers new ideas and approaches to address environmental pollution problems and holds significant theoretical and applied value.

Rational design of Zn4O(BDC)3 metal organic framework incorporated with NiCr2O4 nanoparticles: An affordable photocatalyst for the degradation of hazardous dyes

In this work, a simple hydrothermal approach was used to make Zn4O(BDC)3-NiCr2O4 nanocomposite. The structural, morphological and photophysical properties of the prepared samples were used to evaluate various characterization approaches. The Zn4O(BDC)3-NiCr2O4 nanocomposite appears to have a large surface area and increased absorption of visible light. When compared to pure Zn4O(BDC)3 and NiCr2O4, the Zn4O(BDC)3-NiCr2O4 nanocomposite displayed more effective catalytic activity for degradation of methyl orange (MO) and Rhodamine (Rh B) dye from aqueous solution when exposed to visible light. The Zn₄O(BDC)₃-NiCr₂O₄ nanocomposite achieved degradation efficiencies of 93.75 % and 89.91 % for MO and Rh B dyes, respectively, after 210 and 150 minutes of visible light irradiation. The degradation rate for MO was 0.016 min⁻¹, which is approximately 6.66 times and 3.13 times higher than that of pure Zn₄O(BDC)₃ or NiCr₂O₄ nanoparticles, respectively. In addition, the Zn4O(BDC)3-NiCr2O4 nanocomposite showed high structural stability after the degradation test, and most of its photocatalytic activity was retained even after the recycling examination. Moreover, the radical trapping experiments demonstrated that the major active species including superoxide and hydroxyl radicals played main roles in the photocatalytic process. Additionally, the photocatalytic mechanism of Zn4O(BDC)3-NiCr2O4 nanocomposite has been examined, and a more plausible path of hazardous dye degradation has been provided.

Synthesis of MoS2@MoO3/(Cu+/g-C3N4) ternary composites with double S-scheme heterojunction for peroxymonosulfate activation exposing to visible light

The construction of semiconductor heterojunction is an effective way for charge separation in photocatalytic degradation of pollutants. In this study, a novel MoS2@MoO3/(Cu+/g-C3N4) ternary composites (MMCCN) was prepared via a simple calcination method. The as-prepared composites exhibited exceptional performance in activating peroxymonosulfate (PMS) for the degradation of rhodamine B (RhB). The activity testing results indicated that 99.41 % of RhB (10 mg·L−1, 10 mL) was effectively removed by the synergistic effect of composites photocatalyst (0.1 g·L−1) and PMS (0.1 g·L−1) under visible light irradiation for 40 min. Its reaction rate constant exceeded that of Cu+/g-C3N4, MoO3 and MoS2 by a factor of 3.56, 17.30 and 11.73 times, respectively. The crystal structure, band gap and density of states (DOS) of the semiconductors were calculated according to the density functional theory (DFT). Free radical trapping tests and electron spin resonance spectroscopy validated that 1O2, O2− and h+ are primary reactive species participating in the decomposition of RhB. The ternary composites demonstrated good stability and maintained excellent degradation efficiency even across four reaction cycles. Furthermore, the activation mechanism and the intermediates produced during the decomposition course of RhB by MMCCN/PMS/vis system were analyzed and elucidated. A double S-scheme heterojunctions was responsible for efficient separation of photo-induced electron-hole pairs. This work presents a novel method in the construction of double S-scheme heterojunctions for PMS activation which is expected to find wide applications in wastewater treatment and environmental remediation.

Green synthesis of Z-scheme N-doped g-C3N4/Nd-doped ZnO heterostructure by pomegranate waste peel with enhanced photocatalytic performance for organic pollutants removal and antibacterial activity

Nowadays, the growing global population and increased industrialization have exacerbated water pollution, posing a significant environmental threat. To tackle this issue, there is an urgent need for effective catalysts to remove pollutants. This study developed a novel N-doped g-C3N4/Nd-doped ZnO (NZ) heterostructure using a green approach by incorporating pomegranate peel waste as a stabilizing and capping agent. Characterization techniques confirmed successful NZ nanohybrid preparation. The synthesized NZ displayed high photocatalytic activity in degrading methylene blue (MB) and tetracycline (TC) pollutants found in wastewater, achieving degradation efficiencies of 95.3 % and 98.3 %, respectively. Meanwhile, it demonstrated satisfactory photostability after five-cycle experiments. The radical trapping experiments revealed that superoxide (O2−) and hydroxyl (OH) are the dominant active species and play an essential role in photocatalytic pollutant deterioration. Additionally, it exhibited suitable antimicrobial activity against Staphylococcus aureus and Vibrio cholerae bacterial strains. The enhanced performance is attributed to the abundant reaction sites of porous N-doped g-C3N4, the photo-redox capability of Nd-doped ZnO, and the efficient charge separation process in the Z-type heterojunction. This work advances sustainable and eco-friendly chemistry for the biosynthesis of organic/inorganic heterojunctions used in pollutant degradation and bacterial disinfection of wastewater.

Construction of PANI@V2O5-ZnIn2S4 Z-scheme heterojunction photocatalysts for highly effective degradation of industrial dyes and antibiotics

From an environmental protection, the highly effective photodegradation of organic dyes and antibiotics in wastewater needs to be solved expeditiously. Fortunately, the construction of Z-scheme heterojunction for photocatalytic degradation is considered to be an effective method. In this paper, after the fabrication of V2O5 by calcination and loading of PANI on its surface by aniline polymerization, a novel PANI@V2O5-ZnIn2S4 composite photocatalysts prepared by one-pot synthesis method and used for the degradation of industrial dyes (crystalline violet, Congo red) and antibiotics (tetracycline-TC). Under the optimal photodegradation conditions, the 30 wt% PANI@V2O5-ZnIn2S4 heterojunction photocatalysts resulted in more than 95 % degradation of CR, CV and TC solutions after 32 min of irradiation. The optimal photodegradation conditions of the simulated pollutants in real aqueous environments catalyzed by the as-synthesized photocatalysts were explored via response surface methodology (RSM). Multiple material characterization techniques, such as FESEM, HRTEM, XPS valence band spectrum, photoelectrochemistry, radical trapping experiments and EPR tests verified the existence of Z-scheme heterojunction. Especially, the coating of conductive PANI on the V2O5 surface can further improve the separation and transfer efficiency of photogenerated charge carriers, thereby enhancing the photocatalytic activity of the semiconductor photocatalyst. This study will provide a robust option for the design and construction of Z-scheme heterojunctions photocatalysts for environmental pollution remediation.

Z-scheme flower-like Ag/AgCl/NiZnAl-LDH for high efficiency removal of Methylene Blue: Performance and mechanism insights

3D flower-like NiZnAl-LDH was prepared, and then the Z-scheme Ag/AgCl/NiZnAl-LDH heterojunctions were further constructed by loading different amounts of AgCl on NiZnAl-LDH surface. The structure, morphology and photoelectric properties were characterized by a variety of advanced techniques, such as XRD, XPS, SEM, HRTEM and EIS. Furthermore, methylene blue, abbreviated MB, was used as the target pollutant, and the photocatalytic degradation activity of Ag/AgCl/NiZnAl-LDH on it was explored. Results displayed that the Ag/AgCl/NiZnAl-LDH photocatalysts displayed excellent photocatalytic degradation activity for MB dye compared with AgCl and NiZnAl-LDH, and the loading of different AgCl on the surface of NiZnAl-LDH has a considerable influence on the photocatalytic performance. The alkaline condition and low concentration of MB are more conducive to the photocatalytic degradation of MB by Ag/AgCl/NiZnAl-LDH. The photocatalytic process conforms to the first-order kinetic model with a rate constant of 0.0082 min−1, which is about 3.4 times that of AgCl and NiZnAl-LDH. Compared with AgCl and NiZnAl-LDH, it is found that Ag/AgCl/NiZnAl-LDH increases the separation rate of photogenerated electrons and holes, the photogenerated carrier recombination is inhibited, and the electrochemically active area is increased. The outstanding photocatalytic activity and stability make Ag/AgCl/NiZnAl-LDH a perfect material to ease the environmental crisis. Besides, combined with free radical trapping experiments, a possible photocatalytic mechanism was raised.

Fabrication of dual-functional smart materials: 2D-WO3/rGO nanocomposite for electrochemical detection and photocatalytic degradation of tetracycline

The extensive utilization of the antibacterial agent tetracycline (TC) in pharmaceuticals and livestock farming has sparked considerable health apprehensions for the welfare of both animals and humans. The presence of TC drug residues in soil, rivers, lakes, and groundwater further exacerbates these concerns. To address these issues, we synthesized WO3/rGO nanocomposites using a simple hydrothermal method and explored their bifunctional catalyst properties for the first time. These nanocomposites were investigated for their potential applications in electrochemical sensing and photocatalytic degradation of TC drug. The electrocatalytic oxidation of TC drug using the WO3/rGO/Glassy Carbon Electrode (GCE) nanocomposites demonstrated good sensitivity, low detection limit, low quantification limit and wide linear range of 1.708 µA µM−1 cm−2, 202 nM, 0.202 µM and 0.1–400 µM, respectively. Moreover, we assessed the WO3/rGO/GCE nanocomposites effectiveness in detecting TC drug in real samples, including milk, lake water, fish, and tap water, and found the recovery results to be satisfactory. Additionally, the nanocomposites displayed noteworthy photocatalytic activity in degrading the TC drug. The as-prepared WO3/rGO nanocomposites exhibited an impressive degradation efficiency of 87.5 % over 120 minutes under UV–visible light irradiation. Radical trapping tests confirmed that the *OH- radicals played a significant role in the degradation process. Our study highlights the outstanding electrochemical and photocatalytic properties of WO3/rGO nanocomposites, positioning them as highly promising materials for future biomedical and environmental applications.

Decomposition of tetracycline with peroxymonosulfate activated by an ordered hierarchical pores Fe-N/C catalyst rich in FeNx sites: Insights into singlet oxygen mechanism

FeNx sites show significant superiority in the degradation of antibiotic contaminants, but there are difficulties in successfully constructing highly dispersed FeNx sites. In this work, Fe-N/C catalysts doped with hierarchical ordered pores structure and FeNx active sites were prepared by metal node exchange strategy. Among them, Fe-N/C-2 had more excite species for peroxymonosulfate (PMS) owing to the synergy between Fe and N coordination, which achieved 89.36 % tetracycline (TC) removal rate within 20 min, and its reaction kinetic (k = 0.245 min−1) is 7.66 times more than original PMS system. Moreover, the material exhibited excellent activation performance in a variety of complex water environments, such as the coexistence of multiple anions, strong acids and alkalis (pH = 2.90 ∼ 10.73), and natural organic matter interference. Chemical bond detection confirmed the successful formation of FeNx sites, free radical trapping experiments showed that FeNx was the main catalytic site, and 1O2 was the main active component. Furthermore, the reaction principle of the FeNx site catalyzing the production of 1O2 from PMS was revealed in detail through mechanism exploration. Next, the probable pathways of TC decomposition were elaborated in terms of the intermediates identified by Liquid Chromatograph Mass Spectrometer (LC-MS). This study emphasized the significant potential of synthesizing Fe-N/C catalysts with activated FeNx sites, elucidated mechanism of FeNx in PMS activation, and confirmed its feasibility in TC degradation.

Degradation of thiamphenicol by La-Fe2O3/DBD/HCP synergistic catalytic system

In this study, a highly efficient La-Fe2O3/dielectric barrier discharge (DBD)/honeycomb ceramic plate synergistic catalytic system was successfully constructed by using modified iron oxide (Fe2O3) catalyst coating assisted DBD plasma, and the prepared catalytic coating was fully characterized by various techniques. The results indicate that the lanthanum (La) is efficiently and uniformly doped in Fe2O3, and the modified La-Fe2O3 catalyst exhibited a better photocatalytic performance. The overuse of Thiamphenicol (TAP), as a typical chloramphenicol antibiotic, has led to its accumulation in the aquatic environment. Accordingly, TAP was selected as the target contaminant to evaluate the catalytic activity of the synergistic system. The results confirmed that the catalytic ability of the synergistic catalytic system was significantly improved, and the data showed that the degradation rate of the synergistic system reached 99.1% under the same conditions compared with 68.2% for the single DBD plasma, which effectively improved low energy efficiency limitations of the single DBD technology. Through quantitative measurements of the concentrations of dissolved ozone (O3) and hydrogen peroxide (H2O2) in the system and radical trapping experiments, combined with emission spectroscopy, the mechanism of synergistic system degradation of TAP was analyzed. The intermediates in the degradation process were characterized by high-resolution mass spectrometry, and the degradation pathway of TAP was proposed based on the analysis of the intermediates and their combination with theoretical calculations. This study presents a theoretical basis for the improvement of DBD technology and a technical guide for the removal process of antibiotics from industrial wastewater.

Constructing novel metal-free HCOF-Ph@g-C3N4 heterojunctions through molecular expansion to enhance photogenerated carrier involved molecular oxygen activation and photocatalytic hydrogen evolution

Modification of covalent organic frameworks (COFs) have exceptional stability as well as tunable structures is the key to efficient photocatalysts. In this study, hyper-crosslinked COF-Ph was constructed with g-C3N4 to obtain a novel HCOF-Ph@g-C3N4 heterojunction, and the lamellar mesoporous of g-C3N4 was successfully embedded into the pores of 3D HCOF-Ph. The synthetic strategy greatly enhanced the photocatalytic properties and molecular oxygen activation capability of the catalyst. 10 mg of HCOF-Ph@g-C3N4 heterojunction could completely degrade 30 mg/L of tetracycline (TC) within 14 min, and the rate of hydrogen generation reached 9214.69 μmol g−1 h−1. The active species in this process of photocatalysis were verified through tests with free radical trapping and ESR spectra. In addition, the molecular oxygen activation capacity of heterojunction interface and the yield of superoxide radicals were examined by 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation and degradation of nitrotetrazolium nlue chloride (NBT) experiments, respectively. We found that the molecular expansion strategy can change molecule energy band structure to improve absorption of sunlight, and the efficient segregation of the photogenerated charge were ensured by the complementary energy band structure between g-C3N4 and HCOF-Ph. This study created an efficient molecular expansion method for the synthesis of COF-based catalysts with potential uses in the energy and environmental fields.

Activation of Peroxymonosulfate using a novel heterogeneous catalyst SO-gCN@ZIF-67 for excellent degradation of Brilliant Green dye

This work presents a design of a novel heterogeneous catalyst, SO-gCN@ZIF-67, comprising Co-based MOF, ZIF-67, over a two-dimensional S and O co-doped graphitic carbon nitride nanosheet is reported. This novel heterogeneous SO-gCN@ZIF-67 catalyst is used to degrade organic polluting dyes by activating Peroxymonosulfate (PMS) at room temperature. Various analytical and spectroscopic techniques, such as PXRD, FT-IR, FE-SEM, EDS, HR-TEM, XPS, and UV-DRS, were employed to characterize the as-synthesized nano-catalyst. The as-prepared catalyst can activate PMS effectively to rapidly decolorize the Brilliant Green dye (BG dye) solution at room temperature. The catalyst SO-gCN@ZIF-67 showed high efficiency for PMS activation and decolorization of approximately 96.7 % BG dye with a catalyst concentration of 80.0 mg/L, which was achieved in 15 min. The degradation of the dye obeyed pseudo-first-order kinetics with a reaction rate constant of 0.2262 min−1. Further, the parameters that could influence the activation of PMS, such as the role of different catalysts, catalyst dosage, PMS dosage, and initial dye concentration, were also investigated. Radical trapping experiments revealed that O2− radicals and non-radical singlet oxygen, 1O2, were involved in the degradation of BG dye. A plausible mechanism for the degradation has been proposed using SO-gCN@ZIF-67 and the PMS system.

Employing Cu@Fe3O4/SiO2@MWCNTs as New Catalyst for the Green Synthesis of New Pyridopyrroloindoles Using Multicomponent Reactions of Isatins

ABSTRACTBy using a multicomponent reaction involving isatins, diamines or aminoalcohols, activated acetylenic compounds, haloketones, and ammonium acetate in aqueous media in the presence of Cu@Fe3O4/SiO2@MWCNTs as new catalyst, the novel pyridopyrroloindole was produced in high yields. This catalyst was produced by employing Petasites hybridus rhizome water extract as a green media and moderate base. The pyridopyrroloindole derivatives were newly synthesized compounds, and their antioxidant properties were assessed using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical trapping and ferric reducing ability of plasma (FRAP) experiments. The pyridopyrroloindole 6b showed higher performance than butylated hydroxytoluene (BHT) and tert‐butylhydroquinone (TBHQ) better results. This method is used to make pyridopyrroloindole derivatives, and it has the advantages of a quick reaction, high yields, and the ability to separate the products easily.

C3 Selective chalcogenation and fluorination of pyridine using classic Zincke imine intermediates

Regioselective C–H functionalization of pyridines remains a persistent challenge due to their inherent electronically deficient properties. In this report, we present a strategy for the selective pyridine C3-H thiolation, selenylation, and fluorination under mild conditions via classic N−2,4-dinitrophenyl Zincke imine intermediates. Radical inhibition and trapping experiments, as well as DFT theoretical calculations, indicated that the thiolation and selenylation proceeds through a radical addition-elimination pathway, whereas fluorination via a two-electron electrophilic substitution pathway. The pre-installed electron-deficient activating N-DNP group plays a crucial and positive role, with the additional benefit of recyclability. The practicability of this protocol was demonstrated in the gram-scale synthesis and the late-stage modification of pharmaceutically relevant pyridines.

A novel all-solid-state Z-scheme BiVO4/Ag/Cu2O heterojunction: Photocatalytic and photothermal synergistic catalysis of tetracycline under simulated sunlight irradiation

The possible hazards posed by tetracycline (TC) to the environment and public health have made it a critical concern. In this work, the all-solid-state Z-scheme heterojunction BiVO4/Ag/Cu2O nanocomposites (NCs) were synthesized through a hydrothermal approach for the purpose of achieving efficient degradation towards TC. BiVO4/Ag/Cu2O NCs were able to efficiently degrade TC when exposed to simulated sunlight. The results showed that the photocatalytic efficiency was significantly influenced by Cu2O and Ag nanocrystals. The presence of Ag with large light absorption capability facilitated the efficient electron (e-) transfer between BiVO4 and Cu2O nanocrystals, thereby expanding the spectral range of light absorption in BiVO4/Cu2O NCs. Under photocatalytic and photothermal synergistic conditions, BiVO4/Ag/Cu2O NCs with an optimal addition of Ag were able to degrade TC within 60 min at reaction rate constant (k) of 0.04816 min−1. It was discovered that the best-performing photocatalysts (BAC-2) achieved photothermal conversion rates as high as 27.9 %, and they could exhibit outstanding photocatalytic and photothermal efficiency even after six cycles. Furthermore, the results obtained in radical trapping experiments suggested that photogenerated holes (h+), electrons (e-), superoxide radicals (·O2-), hydroxyl radicals (·OH) and singlet oxygen (1 O2) were involved in the photocatalytic degradation of TC. In the context of practical application, the effects of different initial TC concentrations and different irradiation conditions were studied in depth. In addition, the all-solid-state Z-scheme heterojunction mechanism for degrading TC was put forward. This research endeavors to broaden the application scope of all-solid-state Z-scheme heterojunction photocatalysts, with the aim of achieving significantly improved photocatalytic degradation of antibiotic pollutants.

Synergistic enhancement of singlet oxygen generation in Au and oxygen vacancy co-modified Bi2MoO6 ultrathin nanosheets for efficient ciprofloxacin degradation

Solar-driven molecular oxygen activation (MOA) is crucial for generating reactive oxygen species (ROS) for pollutant degradation, while the low activation efficiency greatly weakens the degradation efficiency. Herein, oxygen vacancies (OVs) and Au nanoparticles are co-introduced into Bi2MoO6 (ABMOH) to enhance the photocatalytic activity of Bi2MoO6 (BMO), thereby promoting MOA efficiency. Density functional theory demonstrates that the introduction of OVs not only improves the molecular oxygen adsorption on BMO, and but also strengthens the O-O bond dissociation of molecular oxygen, which is beneficial to MOA. Meanwhile, the unique localized surface plasmon resonance effect of Au nanoparticles immensely increases the photo-absorption capacity. Crucially, both OVs and Au nanoparticles work as “electron traps” to capture photogenerated electrons, thereby accelerating charge transfer. Based on the advantage of OVs and Au nanoparticles, ABMOH displays excellent MOA efficiency, and the degradation rate constant of ciprofloxacin (CIPF) by ABMOH-4 is 3.62-fold higher than BMO. Free radical trapping experiment and electron spin resonance suggest that singlet oxygen (1O2) can be selectively formed in the ABMOH system for CIPF degradation, and superoxide radical (•O2–) conversion and energy transfer are two pathways for 1O2 formation. This investigation serves as a beacon for the strategic design of high-performance and stable photocatalysts for MOA activation, paving the way for advancements in environmental remediation.

Construction of g-C3N4@Bi-MOF@BiOCl double Z-type heterojunctions for photodegradation of antibiotics under visible light irradiation: Mechanism, pathway, and toxicity assessment

In this study, flower-like microspheres dispersed double Z-type heterojunction g-C3N4@Bi-MOF@BiOCl photocatalysts were prepared using Bi-MOF as the structural template. The photocatalyst showed good degradation ability for both tetracycline antibiotics under simulated sunlight irradiation, as well as stable recyclability and total organic carbon mineralization (TOC). This excellent photocatalytic activity was mainly attributed to the formation of double Z-type heterojunctions that accelerated charge separation and transfer and drove stronger redox capacity. In addition, the effects of conditions such as catalyst dosage, initial concentration of tetracycline hydrochloride (TC) and initial pH (3–11) value of the solution on the photocatalytic reaction were investigated. The results of free radical trapping experiments and ESR analyses indicated that O2−, h+ and OH were the active free radicals that could not be neglected for the degradation of tetracycline hydrochloride (TC), and a possible degradation mechanism was further proposed. Finally, the possible pathways for degradation of the intermediates were rationally deduced by gas chromatography (GC–MS) and evaluated by ecotoxicity analysis based on the utilization rate (T.E.S.T.) of the intermediates produced. This study provides an effective idea for the rational design and synthesis of highly efficient dual Z-type photocatalysts for antibiotic contamination in water-polluted environments.