Schematic diagram for the antibacterial in the direct Z-scheme silver iodide decorated bismuth vanadate photocatalyst.
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Novel Z-scheme AgI/BiVO4 photocatalysts were fabricated by a ...chemical deposition-precipitation approach. The photocatalytic activities of the obtained catalysts were evaluated by disinfection of Escherichia coli (E. coli) and degradation of oxytetracycline hydrochloride (OTC-HCl) under visible-light irradiation. The BA3 (contained 9.09% of AgI) exhibited the highest photocatalytic activity and maintained good stability. It could completely inactivate 7.0×107 CFU/mL of E. coli in 50 min and degrade 80% of OTC-HCl in 60 min. The enhanced photocatalytic activity of AgI/BiVO4 composites could be ascribed to the lower recombination rate of electron-hole pairs. Meanwhile, radical trapping experiments revealed that the superoxide radical (O2−) and holes (h+) were the dominant reactive species in photo-disinfection process. Furthermore, the effects of bacterial initial concentration and inorganic anions were also investigated to optimize the photocatalyst for practical application. This study will give a new insight to construct the effective Z-scheme system for bacterial inactivation and organic pollutants degradation.
•A high BDE-47 debromination strategy assisted with solar energy is provided.•The artificial Z-scheme system possesses both reduction and oxidation abilities.•The novel system possesses enhanced ...charge carrier separation and transfer.•A possible transfer pathway of BDE-47 debromination was proposed.
2,2′,4,4′-Tetrabrominateddiphenyl ether (BDE-47), as one of polybrominated diphenyl ethers (PBDEs), has been proven to be global contaminant owing to widespread utilization as flame retardant. Herein, a novel visible-light-driven (VLD) artificial indirect Z-scheme system of Ag@Ag3PO4/g-C3N4/rGO is finely designed for BDE-47 removal assisted with abundant solar energy. The novel hybrid composite exhibits an enhanced reductive debromination activity with removal efficiency of 93.4% under visible light irradiation (λ > 420 nm) for 120 min, which is 173.65 times higher than pristine g-C3N4 catalyst. A series of experiments in terms of the environmental effects of initial concentration, pH, solvent and light source are performed to optimize the photocatalytic performance. The presence of rGO as an excellent storing and shuttling medium, can further facilitate the charge carrier separation in the indirect Z-scheme system for the enhanced photo-reduction debromination performance. The accumulated electrons on the solid catalyst can attack the ortho-Br of BDE-47 to formation of BDE-28, and then so on. The protons (H+) can be reduced to atomic hydrogen (H°), which can greatly weaken para-Br of BDE-47 to generation of BDE-17. Furthermore, the remaining holes can react with CH3OH to generate CH2OH radical, and then further directly produce electron for debromination process. A possible debromination pathway for BDE-47 was proposed. This work provides a green and promising strategy utilizing solar energy to remove BDE-47 in the liquid medium by virtue of VLD composite.
Developing photocatalysts with superior performance to generate hydrogen peroxide (H2O2) and degrade oxytetracycline (OTC) is an effective strategy for the treatment of energy crisis and water ...purification. Herein, BN nanosheets were anchored onto the Zn3In2S6 microspheres for the research. Experimental and density functional theory (DFT) results demonstrate that due to different work functions and unique 2D/2D contact, the electron is spatially separated in BN/Zn3In2S6 nanocomposite, which increases the electron transfer efficiency from 43.7% (Zn3In2S6) to 55.6% (BN/ZIS-4). As a result, BN/ZIS-4 with optimal ratio of BN and Zn3In2S6 exhibits the highest OTC degradation efficiency (84.5%) and H2O2 generation rate (115.5 μmol L−1) under visible light illumination, which is 2.2 and 2.9 times than that of pristine Zn3In2S6. H2O2 generation is dominated by two pathways: two-step single-electron process (O2 → ∙O2- → H2O2) and another way (O2 → ∙O2- → 1O2 → H2O2). In the process of degrading OTC, ∙O2-, 1O2 and ∙OH are regarded as the main active species. This work offers a new insight for designing efficient, stable and reusable photocatalysts to solve current environmental conundrums.
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•Outstanding H2O2 generation capacity and OTC degradation performance.•Two generation pathways of H2O2 production and their specific mechanisms.•This work offers new insight into the development of ZnInS-based catalysts.
Photocatalysis is considered to be an effective way to remove organic pollutants, but the key to photocatalysis is finding a high-efficiency and stable photocatalyst. 2D materials-based ...heterojunction has aroused widespread concerns in photocatalysis because of its merits in more active sites, adjustable band gaps and shorter charge transfer distance. Among various 2D heterojunction systems, 2D/2D heterojunction with a face-to-face contact interface is regarded as a highly promising photocatalyst. Due to the strong coupling interface in 2D/2D heterojunction, the separation and migration of photoexcited electron-hole pairs are facilitated, which enhances the photocatalytic performance. Thus, the design of 2D/2D heterojunction can become a potential model for expanding the application of photocatalysis in the removal of organic pollutants. Herein, in this review, we first summarize the fundamental principles, classification, and strategies for elevating photocatalytic performance. Then, the synthesis and application of the 2D/2D heterojunction system for the removal of organic pollutants are discussed. Finally, the challenges and perspectives in 2D/2D heterojunction photocatalysts and their application for removing organic pollutants are presented.
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•The fundamental principles and synthesis methods of 2D/2D heterojunction.•Type I, type II, p-n junction, Z-scheme, S-scheme and Schottky junction.•The photodegradation performance of 2D/2D heterojunction systems.•The current challenges and future development directions of 2D/2D heterojunctions.
Magnetic materials usually exhibit advanced performance in many areas for their easy separating and recycle ability. In this study, silver iodide/copper ferrite (AgI/CuFe
O
) catalysts with excellent ...magnetic property were successfully synthesized and characterized by a series of techniques. Two typical bacteria Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were applied to estimate the photocatalytic inactivation performance of obtained AgI/CuFe
O
catalysts. Results revealed that the AgI/CuFe
O
(12.5% AgI) composite could absolutely inactivate 3 × 10
CFU/mL E. coli and 2.7 × 10
CFU/mL S. aureus cells severally in 50 min and 40 min under visible light irradiation, which showed a much higher photo-disinfection activity than monomers. Transmission electron microscopy was used to study the biocidal action of this nanocatalyst, the results confirmed that the treated E. coli cells were damaged, the nanocatalyst permeated into cells and resulting in death of cells. Besides, it was found that the destruction of bacterial membrane together with substantial leaked potassium ion (K
) which caused by the photo-generated reactive species superoxide radical (O
) and holes (h
) could be the direct disinfection principles. For a deep insight into practical applications, the influences of different catalyst concentrations and reaction pH were also taken into discussion in details. The overall results indicated the novel photocatalyst with strong redox capacity and outstanding reusability can be widely employed in bacteria elimination.
•Magnetic-graphene oxide (M-GO) with excellent antibacterial activity is prepared.•The antibacterial activity of M-GO relies on concentration and mass ratio of M/GO.•Synergetic antibacterial effect ...of M-GO is observed with M/GO mass ratio of 9.09.•TEM images illustrate that M-GO has penetrated into the cytoplasm.•Synergetic mechanism accounts for the antibacterial activity of M-GO.
The challenge to achieve efficient disinfection and microbial control without harmful disinfection byproducts calls for developing new technologies. Magnetic-graphene oxide (M-GO) with magnetic iron oxide nanoparticles well dispersed on graphene oxide (GO) nanosheets exerted excellent antibacterial activity against Escherichia coli. The antibacterial performance of M-GO was dependent on the concentration and the component mass ratio of M/GO. The synergetic antibacterial effect of M-GO was observed with M/GO mass ratio of 9.09. TEM images illustrated the interaction between E. coli cells and M-GO nanocomposites. M-GO nanomaterials were possible to deposit on or penetrate into cells leading to leakage of intercellular contents and loss of cell integrity. The inactivation mechanism of E. coli by M-GO was supposed to result from both the membrane stress and oxidation stress during the incubation period. M-GO with excellent antibacterial efficiency against E. coli and separation-convenient property from water could be potent bactericidal nanomaterials for water disinfection.
•A fluorescent ratiometric sensor for water content determination in organic solvents was presented in this paper.•The fluorescence ratio sensor proposed in the paper minimized the influence of ...measuring external conditions and obtains a more stable signal.•The sensor showed satisfactory selectivity, reproducibility, stability, and fast response time.
This paper describes a fluorescent ratiometric sensor for water content determination in organic solvents. Two different compounds, 4′-N, N-dimethylamino-4-methylacryloylamino chalcone (DMC) and 5, 10, 15, 20-tetra-(4-methylacryloylaminophenyl)porphyrin Zinc (TMAPPZn), were synthesized as indicators for fluorescence ratiometric water sensing. DMC is a fluorescence indicator with charge donor parts and acceptor parts and sensitive to solvent polarity and water content. The fluorescence intensity of TMAPPZn is insensitive to the water content lower than 10% (v/v) water content and employed as the reference indicator. The use of TMAPPZn as a reference indicator resulted in a more stable signal due to minimizing the effects of fluctuations of light intensity, fluorophore bleaching, background signal, and so forth. DMC and TMAPPZn were photo-copolymerized on the silanized glass surface to prevent leakage of the fluorescence indicators. Three organic solutions (ethanol, acetone, and tetrahydrofuran) were used to verify the performances of the proposed sensor, and the sensor exhibited a good linearity in the range 0–10% (v/v) water content with detection limits of 0.0097%, 0.011%, and 0.017% for ethanol, acetone, and tetrahydrofuran, respectively. The ratiometric sensor was characteristic of satisfactory reproducibility, reversibility, short response time. The sensing membrane was found to have a lifetime of two month. We carried out preliminary spiking experiments on the actual samples, and the spiked recoveries were of 99.2–102.0%.
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At present, various organic pollutants and pathogenic microorganisms presented in wastewater have severely threatened aquatic ecosystem and human health. Meanwhile, semiconductor ...photocatalysis technology for water purification has attracted increasingly significant attention. Herein, we successfully constructed a series of novel visible-light-driven (VLD) Bi4O5I2/AgI hybrid photocatalysts with different AgI amounts. Compared with pristine AgI and Bi4O5I2, Bi4O5I2/AgI with the optimal AgI contents exhibited remarkably enhanced photocatalytic performance in probe experiment for Escherichia coli (E. coli) disinfection and tetracycline (TC) degradation. The efficiency for TC degradation and E. coli inactivation reached 82% and 100% in 30 min, respectively. The enhanced electron-hole separation efficiency was responsible for improved photocatalytic activity. In addition, the destruction process of the chemical structure of TC molecules was further investigated by three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs). The activity and crystal phase of the catalysts did not change significantly after four cycles, demonstrating their excellent recyclability and stability of catalysts. The Ag+ ion leaking experiments, radical trapping experiments and ESR tests demonstrated that OH, O2− and h+ were the main active species in photocatalytic disinfection processes. Furthermore, the photocatalytic mechanism of Bi4O5I2/AgI nanomaterials was discussed in detail in conjunction with the energy band structure, and a reasonable Z-scheme interfacial charge transfer mechanism was proposed. This work is expected to provide an efficient water disinfection method.
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•2D/1D MgIn2S4/CdS heterojunction was fabricated through a simple hydrothermal hydrothermal.•Band structure and density of states were calculated according to density functional ...theory.•MgIn2S4/CdS-0.3 composite displayed lighly efficient Cr(VI) reduction without adding hole scavengers.•The as-synthesized MgIn2S4/CdS composite showed remarkable photocatalytic activity for organic degradation and H2 production.•Enhanced charge carrier separation and transfer were main reasons for excellent photocatalytic capacity.
A novel visible-light-driven 2D/1D MgIn2S4/CdS catalyst with heterostructure was fabricated for sewage treatment and energy conversion. In this study, MIS/CdS-0.3 heterostructure catalyst displayed the remarkable photocatalytic performance, which could reduce about 100% of Cr(VI) within 30 min and decompose approximately 95.98% of oxytetracycline (OTC) after 60 min. Meanwhile, the degradation details and possible decomposition pathways for OTC solution were further verified by 3D EEM and LC-MS. Moreover, the as-obtained 2D/1D MgIn2S4/CdS hybrid composites signally promoted the hydrogen evolved in the light illumination at 420 nm. Meanwhile, some consequences based on various characterization technologies confirmed that the significant photo-induced charge separation rate is a crucial factor in the enhancement of photocatalytic capacity. The intimate contact and the formation of heterostructure between 2D MgIn2S4 nanosheets and 1D CdS nanorods with matched band gaps were beneficial for charge migration. Moreover, the band structures and the density of states (DOS) of MgIn2S4 and CdS were obtained based on density functional theory (DFT). In addition, the results of cycling experiments, XRD spectra and PL showed that the composition and performance of the composite are well-maintained, suggesting the great recyclability and stability. This work indicated that developing a 2D/1D heterostructure photocatalyst offers a cracking approach to enhance the photocatalytic property of semiconductor-based catalysts for pollutant removal and the generation of clean energy.
To maximize the phocatalytic activity, semiconductor-based catalysts need to be properly modified in various methods. Here, a feasible synergistic strategy is proposed for enhancing the ...photocatalytic property. We firstly combine 2D ZnInS4–S nanosheets with amorphous CoB nanoparticles to obtain hybrid catalysts with Schottky junction and S vacancy engineering, and indicate that the CoB/ZnInS4–S with the synergistic effect owns efficiently improved photocatalytic antibacterial performance. Based on systematic characterization technologies and theoretical calculations, it is concluded that the wonderful photocatalytic activity of CoB/ZnIn2S4–S results from enhanced light-harvesting ability, accelerated charge-carriers separation, high specific surface area and more active sites. Moreover, the upward band bending resulted from the difference in work function between two components causes the directional electrons flow from ZnIn2S4–S to CoB, inhibiting the electron backflow and stimulating more reactive oxygen species (ROS) formation. Meanwhile, S vacancy can capture electrons to boost charge-carriers separation. As a result, the optimal 2CoB/ZnIn2S4–S composite can thoroughly inactivate 6.18-log of E. coli under 100 min of visible light illumination. Furthermore, we explored the damage degree of cell membrane by various characterizations to prove the thorough death of E. coli. It is desired that this work can offer some inspiration to develop more progressive photocatalytic systems by multiple effects engineering.
Combing the merits of 2D ZnIn2S4 nanosheets and CoB nanoparticals, a novel photocatalyst with synergistic effect including Schottky junction and S vacancy engineering was fabricated via a simple electrostatic self-assembly method. Due to the difference in work functions between ZnIn2S4 and CoB, the upward band bending results in the directional flow of the photo-generated electrons from ZnIn2S4–S to CoB, and inhibits the electrons backflow. Meanwhile, S vacancies can capture electrons to boost charge-carriers separation. The efficient charge-carriers separation stimulates the generation of more reactive oxygen species (ROS). Finally, ROS and photo-generated h+ act synergistically on the cell membrane of E. coli, leading to the irreversible death of these cells. Display omitted
•CoB/ZIS-S photocatalyst with Schottky junction and vacancy engineering was successfully fabricated.•DFT calculation reveals the charge transfer mechanism of photocatalytic reaction.•The establishment of Schottky barrier in CB/ZIS-S can effectively inhibit the backflow of electrons.•CoB/ZIS-S displays excellent performance for photocatalytic E. coli inactivation.
