Degradation of toxic industrial dyes using SnO2/g-C3N4 nanocomposites: Role of mass ratio on photocatalytic activity

Interface engineered cascade-type electronic structure of 2D/0D/2D CdS-CdCO3/SnO2 quantum dots/g-C3N4 nanocomposite for boosting solar-driven photocatalysis

A rational design of heterojunctions with high-quality contacts is essential for efficiently separating photogenerated charge carries and boosting the solar-driven harvesting capability. Herein, we fabricated a novel heterojunction of SnO2 quantum dots-anchored CdS-CdCO3 with g-C3N4 nanosheets as a superior photocatalyst. SnO2 quantum dots (SQDs) with positively charged surfaces were tightly anchored on the negatively charged surface of CdS nanosheets (NSs). The resulting CdS@SnO2 was finally decorated with g-C3N4 NSs, and a new crystalline phase of CdS-CdCO3 was formed during the hydrothermal decoration process, g-C3N4 decorated CdS-CdCO3@SnO2 (CdS-CdCO3@SnO2@g-C3N4). The as-synthesized photocatalysts were evaluated for the degradation of methyl orange dye under solar light conditions. The CdS-CdCO3@SnO2@g-C3N4 exhibited 7.7-fold and 2.3-fold enhancements in photocatalytic activities in comparison to those of the bare CdS and CdS@SnO2 NSs, respectively. The optimal performance of CdS-CdCO3@SnO2@g-C3N4 is primarily attributed to the cascade-type conduction band alignments between 2D/0D/2D heterojunctions, which can harvest maximum solar light and effectively separate photoexcited charge carriers. This work provides a new inspiration for the rational design of 2D/0D/2D heterojunction photocatalyst for green energy generation and environmental remediation applications.

Metal-organic frameworks incorporated with C3N4: A visible light enhanced platform for degradation of polybromodiphenyl ethers

A series of nano-photocatalysts metal-organic frameworks (MOFs)/graphitic carbon nitride (CN) (named MOFCN-x) with high activity have been synthesized by in-situ growth method. Under visible light irradiation, MOFCN-x hybrids show enhanced photocatalytic activity for the debromination of polybromodiphenyl ethers (PBDEs) compared with CN. Among all the hybrids, MOFCN-2 shows the highest reaction rate, which is 3.3 times as high as that in CN. MOFCN-x photocatalysts own stable visible light activity after recycled experiment. It indicates that a moderate amount of MOFs in MOFCN-x can largely enhance the photocatalytic ability by improved visible light absorption, larger specific surface area and better photo-generated charge carriers separation and transfer capabilities. More interestingly, the debromination pathway of PBDEs by MOFCN-x shows obvious selectivity compared with pure CN that bromines at meta-positions are much more susceptible than those at the para- and ortho-positions. The possible photoreductive mechanism has been proposed. This study shows that nanocomposite MOFCN can be an excellent candidate for dealing with halogen pollutants by solar-driven.

Improved photocatalytic degradation of rhodamine B by g-C3N4 loaded BiVO4 nanocomposites

Photocatalytic degradation has emerged as one of the most efficient methods to eliminate toxic dyes from wastewater. In this context, graphitic nitride (g-C3N4) loaded BiVO4 nanocomposites (5 wt% g-CN@BiVO4 and 10 wt% g-CN@BiVO4) have been fabricated by the wet impregnation method, and their efficiency towards photocatalytic removal of rhodamine B have been investigated under visible light irradiation. These hybrid composites have been characterized by XRD, FESEM, HRTEM, EDS-mapping, UV-Vis DRS, DLS, XPS and BET, etc. The HRTEM images revealed that BiVO4 has a decagonal shape covered by a layered nanosheet-like structure of g-C3N4. BET measurements suggest increasing the proportion of g-C3N4 results enhancement of the specific surface area. Among different photocatalysts, the 10 wt% g-C3N4@BiVO4 hybrid possesses the best catalytic activity with 86% degradation efficiency after 60 min of reaction time. The LC-MS studies suggest that the degradation reactions follow the de-ethylation pathway. Even after five cycles, the heterostructure shows only a 14% decrease in photocatalytic activity, confirming its stability. As a result, the binary composite can be regarded as a promising catalyst for the degradation of pollutants due to its ease of preparation, high stability and superior catalytic activity.

Constructing Z-scheme 1D/2D heterojunction of ZnIn2S4 nanosheets decorated WO3 nanorods to enhance Cr(VI) photocatalytic reduction and rhodamine B degradation

Photocatalysis has been vastly employed as a feasible and efficient strategy for the removal of environmental pollutants. In this study, a well-designed core-shell heterojunction of WO3 decorated with ZnIn2S4 nanosheets were fabricated under mild in-situ conditions, and fabricated processes were systematically investigated with different fabrication durations. The coupling of WO3 and ZnIn2S4 (ZIS) resulted in a Z-scheme mechanism for charge carrier transfer, holding the respective redox capacity. The as-prepared 1D/2D WO3@ZIS heterostructure displayed the highest removal efficiency within 30 min for 25 mg L-1 Cr(VI), 89.3 and 29.7 times higher than pure WO3 and ZnIn2S4. 1D/2D WO3@ZIS remained excellently stable after 5 cycling experiments. Moreover, 40 mg L-1 RhB could be degraded within 50 min. The broad and short photogenerated electron transportation path is guaranteed by the 1D/2D and Z-scheme charge separation mechanism. It efficiently prevented photo-generated charge carriers from recombination, resulting in a longer carrier lifespan and better photocurrent responses than that of pure ones. This photocatalytic system showed promising results and also provides a framework for an efficient system for photocatalysis with potential for environmental application.

Construction of SnO2/g-C3N4 an effective nanocomposite for photocatalytic degradation of amoxicillin and pharmaceutical effluent

The current study mainly focused on the fabrication of 2D graphitic carbon nitride-supported tin oxide nanoparticles (SnO₂/g-C₃N₄) for the effective degradation of Amoxicillin (AMX). Tin oxide (SnO₂) NPs were prepared by green and easy modification technique, and then it is decorated over g-C₃N₄ nanosheets. The structural morphology and surface composition of the synthesized SnO₂/g-C₃N₄ nanocomposite were fully analysed by UV-Vis, XRD, XPS, and HR-SEM with EDAX, FT-IR, and BET analysis. The (HR-TEM) microscopy, the size of SnO₂ NPs which as a diameter is about 6.2 nm. The Raman analysis revealed that the SnO₂/g-C₃N₄ composite had a moderate graphitic structure, with a measured I_D/I_g value of 0.79. The degradation efficiency of antibiotic pollutant AMX and pharma effluent treatment was monitored by UV spectroscopy. The optical band gap of SnO₂ (2.9 eV) and g-C₃N₄ (2.8 eV) photocatalyst was measured by Tauc plots. To investigate the mechanism through the photodegradation efficiency of the catalyst was analysed by using different Scavenger EDTA-2Na holes (h⁺) has a greater contribution towards the degradation process. Under visible irradiation, SnO₂/g-C₃N₄ nanocomposite has exhibited an excellent degradation performance of 92.1% against AMX and 90.8% for pharmaceutical effluent in 80 min.

Sodium alkoxide-mediated g-C3N4 immobilized on a composite nanofibrous membrane for preferable photocatalytic activity

g-C3N4 is a classic photocatalyst not only owing to the metal-free semiconducting electronic structure but also tunable multifunctional properties. However, strategies for chemical exfoliation of g-C3N4 based on organic bases have been rarely reported. A family of sodium alkoxide-mediated g-C3N4 has been prepared via a simple synthesis. The degradation rate of bulk g-C3N4 is 39.8% when irradiation lasts 140 minutes. However, the degradation rate of g-C3N4-MeONa, g-C3N4-EtONa, and g-C3N4- t BuONa is 55.1%, 68.6%, and 79.1%, respectively, under the same conditions. Furthermore, g-C3N4- t BuONa has been immobilized on flexible electrospun PAN nanofibers to prepare floating photocatalysts. SEM analysis shows that the paper-based photocatalyst PAN/g-C3N4- t BuONa becomes a nanofiber membrane (A4 size, 210 mm × 297 mm). The nanofiber is approximately 350 nm in diameter. Interestingly, once synthesized, the g-C3N4- t BuONa particles move into the spinning solution, where the nanofiber wraps around them to form a monodisperse structure that resembles beads, or knots of 1-2 μm, on a string. The degradation efficiency of 10 mg L-1 MB solution can reach 100% for 2 hours until the solution becomes colorless. In addition, the photocatalytic mechanism studies have been validated. Different from H2SO4 or HNO3, this work has proposed a facile strategy for designing preferable floating photocatalysts using sodium alkoxide.

A Comprehensive Review of Graphitic Carbon Nitride (g-C3N4)-Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing

g-C3N4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C3N4, such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C3N4-metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C3N4 and then, we discussed the combination of g-C3N4 with various metal oxides such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, SnO2, etc. We summarized some of their characteristic properties of these heterojunctions, their optical features, photocatalytic performance, and electrical band edge positions. This review covers recent advances, including applications in water splitting, CO2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C3N4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C3N4-metal-oxide-based heterojunctions.

Carbon nanotubes as electronic mediators combined with Bi2MoO6and g-C3N4to form Z-scheme heterojunctions to enhance visible light photocatalysis

In this paper, Z-scheme Bi₂MoO₆/CNTs/g-C₃N₄composite photocatalysts were prepared through a simple hydrothermal method. The analysis was performed by XRD, FT-IR, SEM, EDS, TEM, HRTEM, XPS, BET, UV-Vis diffuse reflectance and PL spectrums. Various analyses show that CNTs not only act as excellent charge transfer bridges, but also enable a formation of the Z-scheme of charge transfer mechanism between Bi₂MoO₆and g-C₃N₄. This process not only effectively isolates electrons and holes, but also prolongs electron-hole pair lifetimes, resulting in a substantial improvement in the photocatalytic performance of the composite photocatalyst. Best photocatalytic degradation performance was shown by Bi₂MoO₆/CNTs/g-C₃N₄composite photocatalyst under simulated sunlight, while the composite photocatalyst still maintained extremely high degradation performance in cycling tests.

Recent advances in Cu2O-based composites for photocatalysis: a review

Cu₂O-based composites for photocatalysis have been extensively explored owing to their promising application in solving environmental and energy problems. At present, the research on photocatalysis is focused on improving the photocatalytic performance of materials. It has been reported that adjusting the morphology and size of Cu₂O can effectively improve its photocatalytic property. However, photocorrosion is still an inevitable problem, which hinders the application of Cu₂O in photocatalysis. The strategies of constructing heterogeneous nanostructures and ion doping can significantly improve the light stability, light absorption capacity and separation efficiency of electron-hole pairs. Cu₂O-based composites exhibit superior performances in degrading organic matter, producing hydrogen, reducing CO₂ and sterilization. Therefore, the construction of multi-materials will be one of the future directions in their photocatalytic application. This review summarizes the recent strategies for enhancing the photocatalytic activity of Cu₂O by analyzing different Cu₂O-based photocatalysts, and the charge transfer pathway is further discussed in detail. Finally, several opportunities and challenges in the field of photocatalysis are illustrated.

Crucial cytotoxic and antimicrobial activity changes driven by amount of doped silver in biocompatible carbon nitride nanosheets

The use of Ag-modified nanomaterials continues to attract attention in biological contamination control, their potential cytotoxicity is often overlooked. Herein, biocompatible carbon nitride is modified with 1 and 5 wt.% Ag and effects of different nanomaterial dose and Ag content on antimicrobial activity and cytotoxicity is studied. Pure Ag nanoparticles and AgNO₃ is tested for comparison, together with ten bacterial strains including pan-resistant Pseudomonas aeruginosa. Cytotoxicity is then investigated in three adherent and two suspension human cell lines, and results confirm that cancer adherent cell lines are the most immune lines and human cervical adenocarcinoma cells (HeLa) are more resilient than human lung adenocarcinoma cells (A549). The HeLa remains over 90 % viable even after 24 -h treatment with the highest concentration of 5%Ag/g-C₃N₄ (300 mg L^-1) while A549 sustained viability only up to 100 mg L^-1. Higher concentrations then induce cytotoxicity and A549 cell viability decreases. Our results show the importance of complementary testing of cytotoxicity by LIVE/DEAD assay using flow cytometry with more different human cell lines, which might be less immune to tested nanomaterials than HeLa and A549. Combined controls of new antibacterial agent activity tests then provide increased knowledge of their biocompatibility.

Morphology-controlled Fabrication of SnO2 /ZnO Nanocomposites with Enhanced Photocatalytic Performance

In this work, a series of novel SnO₂ /ZnO nanocomposites with different morphologies were fabricated via a facile hydrothermal technique followed by calcination in air. The morphological, structural and photocatalytic properties of the SnO₂ /ZnO nanocomposites were studied using different methods. The results showed that the synthesized nanocomposites possessed crystal phases of wurtzite hexagonal phase ZnO and tetragonal rutile phase SnO₂ . In addition, the morphologies of SnO₂ /ZnO nanocomposites strongly depended on the molar ratios of Sn and Zn. Compared with ZnO and SnO₂ , the SnO₂ /ZnO nanocomposites exhibited considerably higher degradation efficiency for the photodegradation of methylene blue and quinolone antibiotics under mercury lamp irradiation. The SZ-2 nanospheres exhibited the highest degradation efficiency of 95.81%, which was about 2.63 times higher than that of ZnO nanoparticles. Moreover, the trapping experiments confirmed that ˙OH played the dominant role in MB degradation. Finally, the charge carriers potential transfer pathway and photocatalytic degradation mechanism were put forward. This study provides an economical way to prepare hybrid nanocomposites with controlled morphology for practical applications in the photocatalytic degradation of organic dyes and residual antibiotics.

Ternary dual Z-scheme graphitic carbon nitride/ultrathin metal–organic framework nanosheet/Ag3PO4 photocatalysts for boosted photocatalytic performance under visible light

The enhanced photocatalytic activity of CN10UA results from fast charge transport through dual Z-scheme channels.