Effective Electron-hole Separation Research Articles

Efficient photocatalytic degradation of ethylenethiourea with zinc oxide photocatalysts: Parameters optimization, mechanism insight, exploration of degradation pathways and toxicity assessment

Traditional advanced oxidation processes (AOPs) for the removal of toxic and refractory ethylenethiourea (ETU) is uneconomical because of the demand for continuous chemical input and full-scale systems. Herein, ETU was efficiently mineralized without sacrificial reagents for the first time through the utilization of ZnO nano-photocatalysts which were synthesized by the adjustment of ratio between the precursor ZnCl2 and alkaline source KOH during hydrothermal process. Compared to other ZnO samples, ZnO-1/3 (1:3 M ratio of ZnCl2 to KOH) exhibited higher apparent rate constant (0.00661 min−1) towards the degradation of ETU because of more effective electron-hole separation. The optimum conditions for ETU degradation (ZnO-1/3 dosage of 0.4 g/L, initial ETU concentration of 10 mg/L and photocatalytic reaction temperature of 35 °C) were acquired according to the outcome of the response surface methodology (RSM) based on the Box-Behnken design (BBD), and the predicted maximum removal efficiency of ETU reached 93.17 % and was consistent with the experimental results under this optimum conditions. The h+ and •OH were proved to the main reactive species during the photocatalytic process by the free radical capture experiments and electron spin resonance (ESR) analysis. Furthermore, the possible degradation pathways of ETU were suggested based on the identified degradation intermediates, and the reduced toxicity of intermediates was also demonstrated through the quantitative structure–activity relationship (QSAR) prediction and the growth of mung bean seedlings. Hence, photocatalysis with ZnO can be regarded as a promising alternative for ETU elimination.

Efficient photocatalytic degradation of ethylenethiourea with zinc oxide photocatalysts: Parameters optimization, mechanism insight, exploration of degradation pathways and toxicity assessment

Traditional advanced oxidation processes (AOPs) for the removal of toxic and refractory ethylenethiourea (ETU) is uneconomical because of the demand for continuous chemical input and full-scale systems. Herein, ETU was efficiently mineralized without sacrificial reagents for the first time through the utilization of ZnO nano-photocatalysts which were synthesized by the adjustment of ratio between the precursor ZnCl2 and alkaline source KOH during hydrothermal process. Compared to other ZnO samples, ZnO-1/3 (1:3 M ratio of ZnCl2 to KOH) exhibited higher apparent rate constant (0.00661 min−1) towards the degradation of ETU because of more effective electron-hole separation. The optimum conditions for ETU degradation (ZnO-1/3 dosage of 0.4 g/L, initial ETU concentration of 10 mg/L and photocatalytic reaction temperature of 35 °C) were acquired according to the outcome of the response surface methodology (RSM) based on the Box-Behnken design (BBD), and the predicted maximum removal efficiency of ETU reached 93.17 % and was consistent with the experimental results under this optimum conditions. The h+ and •OH were proved to the main reactive species during the photocatalytic process by the free radical capture experiments and electron spin resonance (ESR) analysis. Furthermore, the possible degradation pathways of ETU were suggested based on the identified degradation intermediates, and the reduced toxicity of intermediates was also demonstrated through the quantitative structure–activity relationship (QSAR) prediction and the growth of mung bean seedlings. Hence, photocatalysis with ZnO can be regarded as a promising alternative for ETU elimination.

Twisted leaf like ZnO-flake-like BiOI@CNF grown on ITO substrate as a nanostructured pioneering platform for photoelectrochemical water splitting

Despite ZnO nanostructures garnering significant attention for photoelectrochemical (PEC) water splitting, the quest for efficient ZnO-based photoelectrodes with optimal light absorption, effective electron-hole separation, and transfer remains a challenge. The formation of ZnO heterojunctions with lower bandgap nanostructures of semiconductors has emerged as a strategy to enhance charge transfer while mitigating recombination rates. Additionally, the introduction of carbon nanofibers (CNFs) to these heterojunctions serves to further suppress recombination by electron trapping and enhances catalytic active sites, thereby elevating PEC performance. In this study, twisted leaf-like ZnO, flake-like BiOI, ZnO-BiOI nanostructure heterojunctions, and ZnO-BiOI@C composites were synthesized through a solvothermal method. Notably, the ZnO-BiOI@C photoelectrode exhibited outstanding performance, achieving a photocurrent density of 5.6 mA/cm2 through linear sweep voltammetry under light illumination. Each synthesized photoelectrode demonstrated robust photocurrent responsiveness and excellent stability under chopped conditions for up to 1150 s with a 50 s interval. This remarkable stability is attributed to the unique and stable morphological characteristics and strong crystallinity of the synthesized materials. The formed heterojunction between ZnO-BiOI was found to extend light absorption capabilities, while the incorporation of CNFs effectively trapped electrons from the heterojunction's conduction band, enhancing overall water splitting performance. The results underscore the potential of the ZnO-BiOI@C composite as a high-performing photoelectrode for PEC applications, emphasizing the importance of morphological and compositional considerations in advancing PEC technologies.

Exploring electronic features in monolayer and bilayer MX2 (M = Hf, Zr; X = S, Se) structures under shear strain

This study employed first-principles calculations to investigate the dynamic stability of monolayer, bilayer, and heterostructure systems of four MX2 (M = Hf, Zr and X = S, Se) TMDCs, as well as the influence of shear strain on their electronic properties. The computed binding energies and phonon dispersions demonstrate the excellent dynamic stability of bilayer systems, while the small effective masses of electrons and holes in monolayer systems suggest high carrier mobility. Under shear strain, the bandgap size and type of monolayer MX2 system and their vdW heterostructures are effectively modulated, transitioning to metallic behavior under certain strain conditions. Both types of heterostructures exhibit type-II band alignment, serving as direct bandgap semiconductors, facilitating effective electron-hole separation between different layers and thereby reducing recombination. This study elucidates the tunability of the electronic properties of monolayers, bilayers, and heterostructures of MX2 systems under shear strain, which is important for expanding material functionalities and optimizing device performance.

Enhanced selectivity of novel sea urchin-like h-/m-WO3 hetero nanoflowers for highly sensitive detection of ammonia by double filtration method

Real-time monitoring of toxic gases and breath markers can be performed by metal oxide semiconductor-based chemo-resistive gas sensors due to their simple structures, low cost, and faster and better recovery and response. Due to the effective electron-hole separation, tuning the development of phase junctions of the metal oxide is an efficient method for improving their gas sensing properties. In this study, two distinct hydrothermal methods were used to synthesize h-/m-WO3 hetero-nanoflowers. In the first method, L-Cysteine was used to facilitate the formation of phase junctions between h-WO3 and m-WO3 nanostructures, whereas Thiourea was used in the second. Various characterisation approaches validated the hexagonal-monoclinic phase junction development in the nanoflowers. The sensing material fabricated using Thiourea with a concentration of 0.01M performed better than other sensors. At 350°C, the selected sample displayed outstanding ammonia sensing capacity with the experimental detection limit of 1 ppm (response=3.33). The theoretical detection limit is determined to be 27 ppb. The selectivity of the sensor towards NH3 over H2S and acetone is increased by combining the devices with a double filtration setup. The effectiveness of the selected h-/m-WO3 sensor for diagnosing kidney dysfunction was evaluated by analyzing simulated breath samples.

Full-Spectrum Utilization of ZIF-67/Ag NPs/NaYF4:Yb,Er Photocatalysts for Efficient Degradation of Sulfadiazine: Upconversion Mechanism and DFT Calculation.

In this work, novel ternary composite ZIF-67/Ag NPs/NaYF4:Yb,Er is synthesized by solvothermal method. The photocatalytic activity of the composite is evaluated by sulfadiazine (SDZ) degradation under simulated sunlight. High elimination efficiency of the composite is 95.4% in 180min with good reusability and stability. The active species (h+, ·O2 - and ·OH) are identified. The attack sites and degradation process of SDZ are deeply investigated based on theoretical calculation and liquid chromatography-mass spectrometry analysis. The upconversion mechanism study shows that favorable photocatalytic effectiveness is attributed to the full utilization of sunlight through the energy transfer upconversion process and fluorescence resonance energy transfer. Additionally, the composite is endowed with outstanding light-absorbing qualities and effective photogenerated electron-hole pair separation thanks to the localized surface plasmon resonance effect of Ag nanoparticles. This work can motivate further design of novel photocatalysts with upconversion luminescence performance, which are applied to the removal of sulphonamide antibiotics in the environment.

One-dimensional Bi2MoO6 nanosheets/TiO2 hollow tubes:Controllable synthesis and enhanced visible photocatalytic activity

By electrostatic spinning technology combined with solvothermal method, Bi2MoO6 nanosheets were loaded on TiO2 hollow tubes, and Bi2MoO6/TiO2 nanocomposite photocatalytic materials were successfully prepared. The products were characterized by scanning electron microscopy (SEM), Transmission electron microscopy (TEM),X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis) and photoluminescence spectroscopy (PL). The results show that the lamellar Bi2MoO6 nanostructures were successfully grown on TiO2 hollow tubes. The photocatalytic experiments showed that the Bi2MoO6/TiO2 nanocomposites exhibited higher visible light photocatalytic activity than both pure TiO2 and pure Bi2MoO6, which may be due to the effective photogenerated electron-hole separation generated by the Bi2MoO6/TiO2 heterojunction, the photocatalytic degradation of detetracycline, doxycycline and aureomycin by Bi2MoO6/TiO2 photocatalytic system was also compared. In addition, the Bi2MoO6/TiO2 photocatalyst maintained good photocatalytic performance after five cycles, and it was demonstrated by the capture experiments that the superoxide radical played a dominant role in the photocatalytic degradation process, and the contributions of light-generated holes and hydroxyl radicals were approximately the same, and the possible mechanism of its photocatalytic system was proposed.

Cost-effective efficient materials for dye degradation using non-aqueous sol-gel route.

In the present studies, the synthesis of pure ZnO nanoparticles and Mg and S-doped ZnO particles were carried out using a non-aqueous sol-gel method. The synthesized nanoparticles (NPs) are characterized using XRD, FESEM, EDX, FTIR, UV-Vis-DRS, XPS, PL, and BET surface area analysis. X-ray diffraction (XRD) techniques were used to examine the crystallization of ZnO, Mg-ZnO, and S-ZnO samples. The Mg-ZnO and S-ZnO samples exhibit significant c-axis compression and smaller crystallite sizes as compared to undoped ZnO. The optical band gap of Mg-ZnO and S-ZnO NPs were found to be 2.93eV and 2.32eV, respectively, which are lower than that of ZnO NPs (3.05eV). The S-doped ZnO resulted in the homogenous distribution of sulfur ions in the ZnO lattice crystal. XPS analysis revealed that the doped S element was mostly S4+ and S6+. A systematic evaluation has been conducted to assess the influence of several operational parameters, including doped/undoped stoichiometry, solution pH, catalyst dosage, and radical trapping experiment, on the photocatalytic degradation of Rhodamine 6G (Rh 6G) dye. Furthermore, we investigated the photocatalytic degradation activity of ZnO, Mg-ZnO, and S-ZnO samples with aquoues solution of 5ppm Rhodamine 6G (Rh 6G) at room temperature. Results indicated that pure ZnO nanoparticles have the highest photocatalytic degradation rate constant (0.00344min-1), compared to the samples Mg-ZnO (0.00104min-1) and S-ZnO (0.00108min-1) with Rh 6G dye in presence of visible light emitting diode (Vis-LED) source at room temperature. The enhanced visible light photocatalytic activities of pure ZnO NPs were attributed to their superior surface properties (18.30 m2/g) and effective electron-hole separation.

Regulating Relative Nitrogen Locations of Diazine Functionalized Covalent Organic Frameworks for Overall H2 O2 Photosynthesis.

Nitrogen-heterocycle-based covalent organic frameworks (COFs) are considered promising candidates for the overall photosynthesis of hydrogen peroxide (H2 O2 ). However, the effects of the relative nitrogen locations remain obscured and photocatalytic performances of COFs need to be further improved. Herein, a collection of COFs functionalized by various diazines including pyridazine, pyrimidine, and pyrazine have been judiciously designed and synthesized for photogeneration of H2 O2 without sacrificial agents. Compared with pyrimidine and pyrazine, pyridazine embedded in TpDz tends to stabilize endoperoxide intermediate species, leading toward the more efficient direct 2e- oxygen reduction reaction (ORR) pathway. Benefiting from the effective electron-hole separation, low charge transfer resistance, and high-efficiency ORR pathway, an excellent production rate of 7327 μmol g-1 h-1 and a solar-to-chemical conversion (SCC) value of 0.62 % has been achieved by TpDz, which ranks one of the best COF-based photocatalysts. This work might shed fresh light on the rational design of functional COFs targeting photocatalysts in H2 O2 production.

Ultra-sensitive photoelectrochemical biosensor for determination of African swine fever virus based on surface plasmon resonance

Sensitive and specific detection of African swine fever virus (ASFV) is crucial for agricultural production and economic development due to the mortality and infectivity. In this study, a bismuth induced enhanced photoelectrochemical (PEC) biosensor based on in-situ loop mediated isothermal amplification (LAMP) was constructed using deposited bismuth nanoparticles loaded bismuth oxycarbonate (Bi/(BiO)2CO3) as photoactive material, using primers designed according to LAMP as recognition elements, and using in-situ LAMP to achieve nucleic acid amplification of target genes. As the Bi induced surface plasmon resonance (SPR) effect, enhanced light captures and effective electron hole separation, it could effectively enhance the photoelectric activity, so the prepared Bi/(BiO)2CO3 nanohybrid had higher photocurrent intensity and good stability. The constructed PEC biosensor has realized the detection of ASFV in real samples with good sensitivity, specificity and repeatability. In the range from 1.0 × 10−13 to 1.0 × 10−7 g/L, the photoelectric current decreased with the increase of the concentration of ASFV, and the detection limit was 3.0 × 10−14 g/L (about 0.048 copies/μL). Combining the advantages of LAMP with the excellent performance of PEC, it provides a simple, economical and efficient method for nucleic acid diagnosis, and also provides a new idea for biosensor detection.

Highly Efficient Van Der Waals Heterojunction on Graphdiyne toward the High-Performance Photodetector.

Graphdiyne (GDY), a new 2D material, has recently proven excellent performance in photodetector applications due toits direct bandgap and high mobility. Different from the zero-gap of graphene, these preeminent properties made GDY emerge as a rising star for solving the bottleneck of graphene-based inefficient heterojunction. Herein, a highly effective graphdiyne/molybdenum (GDY/MoS2 ) type-II heterojunction in a charge separation is reported toward a high-performance photodetector. Characterized by robust electron repulsion of alkyne-rich skeleton, the GDY based junction facilitates the effective electron-hole pairs separation and transfer. This results in significant suppression of Auger recombination up to six times at the GDY/MoS2 interface compared with the pristine materials owing to an ultrafast hot hole transfer from MoS2 to GDY. GDY/MoS2 device demonstrates notable photovoltaic behavior with a short-circuit current of -1.3 × 10-5 A and a large open-circuit voltage of 0.23V under visible irradiation. As a positive-charge-attracting magnet, under illumination, alkyne-rich framework induces positive photogating effect on the neighboring MoS2 , further enhancing photocurrent. Consequently, the device exhibits broadband detection (453-1064nm) with a maximum responsivity of 78.5 A W-1 and a high speed of 50 µs. Results open up a new promising strategy using GDY toward effective junction for future optoelectronic applications.

A Novel Z-Scheme Heterostructured Bi2 S3 /Cu-TCPP Nanocomposite with Synergistically Enhanced Therapeutics against Bacterial Biofilm Infections in Periodontitis.

Porphyrin-based antibacterial photodynamic therapy (aPDT) has found widespread applications in treating periodontitis. However, its clinical use is limited by poor energy absorption, resulting in limited reactive oxygen species (ROS) generation. To overcome this challenge, a novel Z-scheme heterostructured nanocomposite of Bi2 S3 /Cu-TCPP is developed. This nanocomposite exhibits highly efficient light absorption and effective electron-hole separation, thanks to the presence of heterostructures. The enhanced photocatalytic properties of the nanocomposite facilitate effective biofilm removal. Theoretical calculations confirm that the interface of the Bi2 S3 /Cu-TCPP nanocomposite readily adsorbs oxygen molecules and hydroxyl radicals, thereby improving ROS production rates. Additionally, the photothermal treatment (PTT) using Bi2 S3 nanoparticles promotes the release of Cu2+ ions, enhancing the chemodynamic therapy (CDT) effect and facilitating the eradication of dense biofilms. Furthermore, the released Cu2+ ions deplete glutathione in bacterial cells, weakening their antioxidant defense mechanisms. The synergistic effect of aPDT/PTT/CDT demonstrates potent antibacterial activity against periodontal pathogens, particularly in animal models of periodontitis, resulting in significant therapeutic effects, including inflammation alleviation and bone preservation. Therefore, this design of semiconductor-sensitized energy transfer represents an important advancement in improving aPDT efficacy and the treatment of periodontal inflammation.

Construction of S-scheme heterostructured TiO2/g-C3N4 composite microspheres with sunlight-driven photocatalytic activity

In recent years, the emerging S-scheme heterojunction photocatalyst has embodied great potential in promoting the research and application of photocatalytic technology. Herein, a new TiO2/g-C3N4 S-scheme heterojunction photocatalyst (TCN-20) was constructed by decorating graphite-like carbon nitride on sea urchin-like TiO2 microspheres with a large specific surface area and a mesoporous structure. TCN-20 has excellent optical absorption ability, effective photogenerated electron-hole pair separation and very high photocatalytic degradation activity in the simulated sunlight. The degradation rate of TCN-20 for Rhodamine B reaches 96.5 %, and the reaction rate constant is 4.98 and 4.52 times higher than that of pure TiO2 and g-C3N4, respectively. Moreover, X-ray photoelectron spectra, Fermi level and band structure analyses as well as radical quenching experiments authenticate the S-scheme charge transfer mechanism of TCN-20. TCN-20 is an easy-to-prepare, non-toxic, inexpensive and promising S-scheme heterojunction photocatalyst with strong redox ability.

The performance and mechanism of persulfate activation boosted MoO2@LDHs Z-scheme heterojunction for efficient photocatalytic degradation of tetracycline

Photocatalytic activation of persulfate for the synergistic degradation of pollutants has become a major research hotspot, but the activation effect is poor due to the problems of low catalyst carrier separation efficiency and insufficient active sites. In this study, direct Z-Scheme heterojunctions of MoO2@CoFe LDHs were prepared by a simple hydrothermal method and a Co and Fe dual active site system was constructed to activate Na2S2O8 (PS) for the synergistic degradation of tetracycline under visible light. The results showed that the synergistic degradation of tetracycline was 3.7 times and 2.7 times more efficient than the original heterojunction and PS, respectively. Combining material characterisation, photovoltaic performance tests and theoretical calculations revealed that the high efficiency is attributed to the formation of an internal electric field under the Z-Scheme heterostructure type generating effective electron-hole separation, with more photo-generated electrons converted into radicals acting together with holes to degrade the TC and activate the PS. More importantly, Co(II) and Fe(II) provide electrons to synergistically activate PS, and a portion of the photogenerated electrons and PS activation intermediates can facilitate cycling between Co(II)/Co(III) and Fe(II)/Fe(III) to accelerate PS activation. This paper's work on activating PS-assisted Z-Scheme heterojunctions for the efficient degradation of TC provides a reference for the study of high-performance photocatalytic catalysts for the degradation of organic pollutants.

Study on Method and Mechanism of Noble Metals Photoelectric Deposition by Directly Utilizing Solar Energy

The recovery of noble metals is crucial in terms of resource utilization and ecological environment. Herein, a green strategy for the recovery of three noble metals, Au, Ag, and Pt, by photoelectric deposition at the cathode without external voltage is described. The realizability and mechanism of noble metals deposition are investigated and analyzed in terms of the band structure and the reduction potential of metal ions using the special heterostructure ZnO/ZnS composites derived from metal–organic frameworks, as well as ZnO and Fe2O3 semiconductors. It is found that ZnO/ZnS has preferable photoelectrochemical performance than pure ZnO due to their effective electron–hole separation and appropriate band matching structure. To deposit metals Au, Ag, and Pt, the potential of electrons in the conduction band of ZnO/ZnS should be more negative than the reduction potential of these metals, allowing for the deposition of these metals while simultaneously undergoing an oxygen evolution reaction, mediated by the photogenerated holes on the surface of the photoanode, and the collection of conduction band electrons by the back electrode.

Enhanced photocatalytic activity of cubic ZnSn(OH)6 by in-situ partial phase transformation via rapid thermal annealing

In this study, a mixed phase ZnSn(OH)6/ZnSnO3 photocatalyst was synthesized by calcining ZHS nanostructures via rapid thermal annealing (RTA) process. The composition ratio of ZnSn(OH)6/ZnSnO3 was controlled by changing the duration of the RTA process. The obtained mixed-phase photocatalyst was characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, ultraviolet photoelectron spectroscopy, photoluminescence, and physisorption analysis. Results showed that ZnSn(OH)6/ZnSnO3 photocatalyst obtained by calcining ZHS at 300 °C for 20 sec displayed the best photocatalytic performance under UVC light illumination. Under optimized reaction conditions, ZHS-20 (0.125 g) demonstrated nearly complete removal (>99%) of MO dye in 150 min. Scavenger study revealed the predominant role of OH• in photocatalysis. The enhanced photocatalytic activity of the ZnSn(OH)6/ZnSnO3 composites was mainly ascribed to the photosensitization of ZHS by ZTO and effective electron-hole separation at the ZnSn(OH)6/ZnSnO3 heterojunction interface. It is expected that this study will provide new research input for the development of photocatalyst through thermal annealing-induced partial phase transformation.

Hydrazine-induced synthesis of CdS nanorings for the application in photodegradation

In this paper, CdS nanorings synthesized by a facile hydrazine-induced microwave method for the photodegradation of pollutants were reported for the first time. Different reaction method, microwave power, the category and dosage of pH regulating reagent, reaction temperature and reaction time were investigated. The formation of CdS nanorings from the self-assembly of nanoparticles was attributed to the coordination of hydrazine producing the dipole–dipole interaction among the uniform nanoparticles prepared by microwave method. The crystal phase, composition, morphology and surface property of CdS nanorings were characterized. The results showed that 100 nm-sized wurtzite CdS nanorings generated with the self-assembly of 5–8 nm nanoparticles, which presented mesoporous structures. To study the influence of ring-like structures on the photocatalysis, the photodegradation of rhodamine B (RhB) with CdS nanorings and nanoparticles was compared. The results showed that, CdS nanorings displayed higher photodegradation efficiency, which were originated from more favorable band edge potential and effective electron–hole separation producing more superoxide radical and holes as active specifies. The photodegradation path of RhB contained the process of the demethylation, the decarboxylation process, the chromophore cleavage and ring-open reactions. Finally, the available photodegradation of multiple pollutants and reusability of CdS nanorings were carried out.

Strong interface interaction and internal electric field promote electron transfer of Bi2O2S/NiFe2O4 heterojunction for photocatalytic antibiotic degradation

Heterojunction photocatalysts have shown considerable activities for organic pollutants degradation. However, the faint connection interface and inferior charge shift efficiency critically block the property of heterojunction photocatalysis. Herein, Bi2O2S/NiFe2O4 nanosheets heterojunction with ultrastrong interface interaction and high internal electric field are designed by an in-situ growth method. Tentative and theoretical consequences prove that the interfacial interaction and internal electric field not only act as the electron flow bridge but also decrease the electrons shift energy obstacle, thus speeding up electrons transfer and achieving effective spatial electron-hole separation. Therefore, a large amount of ·O2– and holes as active species were generated. Remarkably, Bi2O2S/NiFe2O4 establishes a considerably boosted photocatalytic performance for tetracycline degradation (0.032 min–1), which is about 14.2-fold and 7.8-fold of the pristine BOS and NFO, respectively. This work provides a promising motivation for modulating charge transfer by interface control and internal electric field to boost photocatalytic performance.

Titanium-based metal-organic framework capsulated with magnetic nanoparticles: Antimicrobial and photocatalytic degradation of pesticides

Pesticide residues create an ecological ecosystem that is incredibly dangerous and presents major risks to human health. To solve this issue, scientists are concentrating on creating extremely effective composites with superior photocatalytic performance. Even if several efforts have been made to remove pesticides and dangerous compounds using adsorption, the development of novel adsorbents with large adsorption capabilities is still very desirable. Here, the photocatalytic of carbamate pesticides in aqueous solution under simulated sunlight irradiation in the existence of Fe3O4, CuO/Cu2O, MIL-125-NH2, Fe3O4@MIL-125-NH2 and CuO/Cu2O@MIL-125-NH2 were investigated. The photocatalytic process may be credited with the effective electron-hole separation and wider area of light response. Moreover, the mechanism of pesticide photocatalytic process was discovered as mineralization of pesticides to carbon dioxide, water, sulphate, and ammonia. Total organic carbon (TOC) analysis was used to quantify the mineralization of pesticides while UV spectroscopy was used to measure the rates of pesticides photocatalytic activity. CuO/Cu2O@MIL-125-NH2 and Fe3O4@MIL-125-NH2 composite demonstrated the maximum pesticide photocatalytic efficiency and outstanding cycle stability. The antimicrobial potency was increased and the inhibition zone was minimised when treated by a parent MIL-125-NH2 and its composites, which is surprising data when employing CuO/Cu2O@MIL-125-NH2 and Fe3O4@MIL-125-NH2 nanocomposite as an anti-bacterial material.

Combination of covalent-organic framework and Bi2O2S by covalent bonds to form p-n heterojunction for enhanced photocatalytic CO2 conversion

The objective of current photocatalysis research is to increase the separation efficiency of photogenerated carriers and convert CO2 into useful resources for human beings. In the present study, TpPa-2-COF was successfully grown in situ on Bi2O2S nanosheets by hydrothermal and thermal solvent two-step experimental method, and a typical p-n heterojunction was constructed by covalent-bond between TpPa-2-COF and Bi2O2S, which significantly improved the photocatalytic activity of CO2. When Bi2O2S@TpPa-2-COF-15 heterojunction was illuminated with 300 W xenon lamp for 3 h, the CO yield reached 19.5 μmol·g−1·h−1, while the CH4 yield reached 6.2 μmol·g−1·h−1. Compared with pure TpPa-2-COF and Bi2O2S, the photocatalytic activity of the Bi2O2S@TpPa-2-COF-15 increased 66.8 and 3.96 times, respectively. Meanwhile, the Bi2O2S@TpPa-2-COF-15 composite showed good stability under multiple cycles. Furthermore, the mechanism of Bi2O2S@TpPa-2-COF heterojunction enhanced photocatalytic reduction of CO2 was also proposed. The experimental and characterization findings have shown that the transit of photo-generated electron-hole pairs via TpPa-2-COF to Bi2O2S may be greatly promoted to achieve the effect of electron hole separation under visible-light irradiation.