Synthesis and characterization of g-C3N4 nanosheets decorated Ag2S composites for investigation of catalytic reduction of 4-nitrophenol, antioxidant and antimicrobial activities

Preparation strategies, properties highlights, and emerging applications across environmental, biological, and energy industries of silver-loaded graphitic carbon nitride: A critical review

In light of escalating environmental pollution and tremendous energy shortage, the development of multifunctional materials with diverse applications across biomedical and energy production platforms has become imperative. Among this domain, nanostructured heterogeneous composites based on semiconductors are exclusively promising owing to their distinct configurations. Notably, graphitic carbon nitride (g-C3N4 (CN)) has drawn substantial interest as a sustainable candidate with surface functionality, electron-rich nature, and interconnected conjugation system along the polymeric matrix. To address the remaining limitations in sub-optimal visible light absorption and rapid charge recombination, the decoration of plasmonic metals, particularly silver (Ag) nanostructures, on bare CN has been reported to induce considerable synergistic promotions. This review highlights the major advancements and challenges in designing silver-loaded graphitic carbon nitride (Ag/CN (ACN)). Fundamentals in typical synthetic strategies, such as hydrothermal, co-precipitation, or chemical reduction, for ACN heterostructures are summarized. The appearance of Ag also influences the inherent properties of CN, as emphasized through alterations in structural as well as electronic behaviors in many studies. We expect that this study can deepen insights into multiple extending applications of ACN regarding environmental, biological, and energy industries, thanks to its favorable well-rounded attributions.

Immobilization of silver-loaded graphene oxide (Ag-GO) on canvas fabric support for catalytic conversion of 4 nitrophenol

Due to the rising human population and industrialization, harmful chemical compounds such as 4-nitrophenol (4-NP) and various dyes are increasingly released into the environment, resulting in water pollution. It is essential to convert these harmful chemicals into harmless compounds to mitigate this pollution. This research focuses on synthesizing a novel heterogeneous catalyst using modified canvas fabric (CF) decorated with silver metal nanoparticles on graphene oxide nanosheets (Ag-GO/CF). The process involves coating the fabrics (CF) with graphene oxide (GO) nanosheets through sonication. Subsequently, silver nanoparticles are deposited in situ and reduced on the GO surface, resulting in the formation of the Ag-GO/CF composite. Various physicochemical characterizations were conducted to examine the interfacial interactions between CF, GO, and Ag nanoparticles. The catalytic activity of the nanocomposite was assessed by hydrogenating 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride (NaBH4). The results showed that the 10%Ag-5%GO/CF with a surface of 6 cm2 (3 × 2 cm) exhibited the highest catalytic activity, achieving a reduction efficiency of over 96% in 5 min. The 4-NP reduction reaction rate was well-fitted with a pseudo-first-order kinetics model with an apparent reaction rate constant (Kapp) of 0.676 min-1. Furthermore, the Ag-GO/CF composite demonstrated remarkable stability over successive cycles, with no noticeable decrease in its catalytic activity, suggesting its promising application for long-term chemical catalytic processes. This synthesized composite can be easily added to and removed from the reaction solution while maintaining high catalytic performance in the reduction of 4-NP, and it could be beneficial in avoiding problems related to powder separation.

Incorporation of g-C3N4 nanosheets and CuO nanoparticles on polyester fabric for the dip-catalytic reduction of 4 nitrophenol

In the present work, we present the preparation of a new emerged heterogeneous catalyst (PE/g-C3N4/CuO) by in situ deposition of copper oxide nanoparticles (CuO) over the graphitic carbon nitride (g-C3N4) as the active catalyst and polyester (PE) fabric as the inert support. The synthesized sample (PE/g-C3N4/CuO) "dip catalyst" was studied by using various analytical techniques (Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy and dispersive X-ray spectroscopy (SEM/EDX), and transmission electron microscopy (TEM). The nanocomposite is utilized as heterogeneous catalysts for the 4-nitrophenol reduction in the presence of NaBH4, in aqueous solutions. According to experimental results, PE/g-C3N4/CuO with a surface of 6 cm2 (3 cm × 2 cm) demonstrated the catalyst exhibit excellent catalytic activity with 95% reduction efficiency for only 4 min of reaction and an apparent reaction rate constant (Kapp) of 0.8027 min-1. Further evidence that this catalyst based on prepared PE support can be a good contender for long-lasting chemical catalysis comes from the remarkable stability after 10 repetitions reaction cycles without a noticeably loss in catalytic activity. The novelty of this work consists to fabricate of catalyst based of CuO nanoparticles stabilized with g-C3N4 on the surface of an inert substrate PE, which results in an heterogenous dip-catalyst that can be easily introduced and isolated from the reaction solution with good retention of high catalytic performance in the reduction of 4-nitrophenol.

Ag NPs decorated on the magnetic rod-like hydroxyapatite/MIL-101(Fe) nanocomposite as an efficient catalyst for the reduction of some nitroaromatic compounds and as an effective antimicrobial agent

A rod-like magnetic nanocomposite was successfully synthesized in this work by loading Ag and Fe₃O₄ nanoparticles onto the surface of the hydroxyapatite/MIL-101(Fe) metal-organic framework. Various techniques were used to investigate the crystalline nature, size, morphology, and magnetic and structural properties of the HAP/MIL-101(Fe)/Ag/Fe₃O₄ nanocomposite, including X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), BET surface area measurements, and zeta potential analysis. The results indicate that the nanocomposite sample is composed of Ag and Fe₃O₄ nanoparticles adhered to rod-like hydroxyapatite/MIL-101(Fe). The catalytic and antibacterial abilities of the as-prepared HAP/MIL-101(Fe)/Ag/Fe₃O₄ were studied. This nanocomposite was utilized as a heterogeneous catalyst for the catalytic reduction of toxic pollutants, including 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), 2,4-dinitrophenol (2,4-NP), 4-nitroaniline (4-NA), and 2-nitroaniline (2-NA) by NaBH₄ in water and at room temperature. These compounds were converted to their amine derivatives within 8-18 min with rate constant values equal to 0.2, 0.3, 0.33, and 0.47 min^-1, respectively. This quaternary magnetic catalyst can be easily separated from the reaction medium using an external magnetic field and reused. The synthesized nanocomposite maintained its efficiency in reducing nitroaromatic compounds after 5 runs, showing the high stability of the catalyst. Besides, the antibacterial activity of the nanocomposite against Gram-negative and Gram-positive bacteria was evaluated using the disk diffusion method. The inhibition zone diameter of the nanocomposite against Staphylococcus aureus, Staphylococcus saprophyticus, and Escherichia coli was measured to be 17, 14, and 12 mm, respectively.

Facile synthesis of CuO/g-C3N4 nanolayer composites with superior catalytic reductive degradation behavior

The cupric oxide (CuO) loaded graphitic carbon nitride (g-C₃N₄) nanocomposites (CuO/g-C₃N₄) were prepared by a facile calcination method. The formation of monoclinic CuO nanocrystals along with g-C₃N₄ was confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic analysis. X-ray photoelectron spectral (XPS) analysis further confirms the formation of CuO/g-C₃N₄. Distribution of CuO stone-like crystalline nanoparticles on g-C₃N₄ nanosheets was observed by transmission electron microscopic images. The influence of CuO loading on the optical property of g-C₃N₄ was determined by ultraviolet (UV)-visible absorption and photoluminescence (PL) spectral analysis. Band gap was decreased from 2.7 to 2.3 eV by the addition of CuO nanoparticles. The catalytic performance of the synthesized samples in 4-nitrophenol (4-NP) and methyl orange (MO) reduction was evaluated. The 5 wt% CuO/g-C₃N₄ showed 99.5% (7 min) and 99.7% (4 min) reduction efficiency for 4-NP and MO respectively. The 5 wt% CuO/g-C₃N₄ could become a potential catalyst in the chemical treatment of organic pollutants.

Microwave-assisted Synthesis, Characterization, Photocatalytic Degradation of Antibiotics, and Fluorometric Selective Sensing Activity of g-C3N4 Supported CuO Composites

Herein, we have designed for the fabrication of a series of g-C₃N₄/CuO composite by using one-step microwave-assisted synthesis for the degradation of antibiotics and detection of nano-molar range of toxic heavy metal ions. The synthesized g-C₃N₄/CuO composites were analyzed and characterized to know the structure, phase, surface area, absorption region, bandgap, and size of the composites. From the observation of TEM and XRD measurements, g-C₃N₄/CuO composites have hexagonal shape with average diameter of the particles is 25 ± 5 nm. The observed band gap values from UV-vis DRS for g-C₃N₄ nanosheets and CuO NPs are 2.64 eV and 1.72 eV. The synthesized g-C₃N₄/CuO composite has prodigious specific surface area (32.47 m²/g), which is the evident for superior heterogeneous catalytic applications. Therefore, the synthesized g-C₃N₄/CuO composites were tested for the degradation of antibiotics such as tetracycline (TC) and ciprofloxacin (CIP) under UV light illumination, it shows 88.02% and 90.01% degradation was observed within 1 h due to the matching optical band gap and internal charge transfer of excitons with in the heterojunction surface among g-C₃N₄ and CuO in the composite than the individual components (g-C₃N₄ and CuO) due to the high surface area and tiny particles of CuO were randomly deposited on the surface of g-C₃N₄ nanosheets. The catalytic reduction reaction follows as pseudo-first order equation and reused for 5 consecutive cycles without remarkable loss of catalytic activity. Moreover, the synthesized CuO NPs and g-C₃N₄/CuO composites were used as a prominent fluorescence sensing probe for the selective detection of Pb²⁺ in nano-molar range of concentration with K_sv is 1.38 × 10⁴ mol^- 1dm³. It was observed as a linear relationship based on the change in intensity, the limit of detection was determined to be 0.184 nM.

Recent Advances in g-C3 N4 -Based Photocatalysts for Pollutant Degradation and Bacterial Disinfection: Design Strategies, Mechanisms, and Applications

Emerging photocatalytic technology promises to provide an effective solution to the global energy crisis and environmental pollution. Graphite carbon nitride (g-C₃ N₄ ) has gained extensive attention in the scientific community due to its excellent physical and chemical properties, attractive electronic band structure, and low cost. In this paper, research progress in design strategies for g-C₃ N₄ -based photocatalysts in the past five years is reviewed from the perspectives of nanostructure construction, element doping, and heterostructure construction. To clarify the relationship between application requirements and structural design, variations in the morphology, electronic energy band structure, light absorption capacity, as well as interfacial charge transfer caused by various modification strategies are discussed in detail. The recent applications of g-C₃ N₄ -based photocatalysts for pollutant degradation and bacterial disinfection are reviewed, as well as the antimicrobial activity and degradation mechanisms. Finally, current challenges and future development directions for the practical application of g-C₃ N₄ -based photocatalysts are tentatively discussed.

Ag-SPR and semiconductor interface effect on a ternary CuO@Ag@Bi2S3 Z-scheme catalyst for enhanced removal of HIV drugs and (photo)catalytic activity

The development of ternary composites has gained great interest as they can be used as a catalyst due to the different semiconductors with the variation in the band edge positions creates a potential gradient at the composite interface.

TriMOF synergized on the surface of activated carbon produced from pineapple leaves for the environmental pollutant reduction and oxygen evolution process

Facile and modest synthesis of significantly effective and less-cost catalysts for environmental pollutant degradation and oxygen evolution holds substantial potential in environmental and energy fields. Hereby, Trimetallic organic frameworks (TriMOF) consisting of Fe, Co, and Zn synergized on the surface of activated carbon (AC) from pineapple leaves tend to show exponential catalytic activity due to the more excellent ionic conductivity, catalytic stability and multiple active sites provided by different metal precursors. Furthermore, the developed nanocomposite was coated on the stainless-steel electrode substrate at room temperature, delivering greater electrocatalytic surface area and numerous active sites. The oxidation reaction kinetics drives the catalytic reduction of 4-nitrophenol to 4-aminophenol with a minimal time of 12 min @ >97 % efficiency. Furthermore, on electrocatalytic oxidation of water splitting process due to the presence of multiple metallic, active sites, the overpotential is at 370 mV having Tafel slope of 40 mV/dec and electrochemically active surface area of is 9.9 mF/cm². This superior catalytic reduction of 4-nitrophenol and electrocatalytic water oxidation process is attributed to the developed composite's active centre and conductivity.

Self-Supporting g-C3N4 Nanosheets/Ag Nanoparticles Embedded onto Polyester Fabric as “Dip-Catalyst” for Synergic 4-Nitrophenol Hydrogenation

Herein, we report the design of a cost-effective catalyst with excellent recyclability, simple recuperation and facile recovery, and the examination between the reaction cycles via the development of self-supporting g-C3N4 nanosheets/Ag NPs polyester fabric (PES) using a simple, facile and efficient approach. PES fabrics were coated via a sono-coating method with carbon nitride nanosheets (GCNN) along with an in situ setting of Ag nanoparticles on PES coated GCNN surface producing PES-GCNN/Ag0. The elaborated textile-based materials were fully characterized using FTIR, 13C NMR, XRD, TGA, SEM, EDX, etc. Catalytic performance of the designed “Dip-Catalyst” demonstrated that the as-prepared PES-GCCN/Ag0 has effectively catalyzed the hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4. The 3 × 3 cm2 PES-GCNN/Ag0 showed the best catalytic activity, displaying an apparent rate constant (Kapp) equal to 0.43 min−1 and more than 10 reusability cycles, suggesting that the prepared catalyst-based PES fabric can be a strong nominee for sustainable chemical catalysis. Moreover, the coated fabrics exhibited appreciable antibacterial capacity against Staphylococcus epidermidis (S. epidermidis) and Escherichia coli (E. coli). The present study opens up new opportunities for the future design of a low cost and large-scale process of functional fabrics.

Recent advances in graphite carbon nitride-based nanocomposites: structure, antibacterial properties and synergies

Bacterial infections and transmission threaten human health and well-being. Graphite carbon nitride (g-C₃N₄), a promising photocatalytic antibacterial nanomaterial, has attracted increasing attention to combat bacterial transmission, due to the outstanding stability, high efficiency and environmental sustainability of this material. However, the antibacterial efficiency of g-C₃N₄ is affected by several factors, including its specific surface area, rapid electron/hole recombination processes and optical absorption properties. To improve the efficiency of the antibacterial properties of g-C₃N₄ and extend its range of applications, various nanocomposites have been prepared and evaluated. In this review, the advances in amplifying the photocatalytic antibacterial efficiency of g-C₃N₄-based nanocomposites is discussed, including different topologies, noble metal decoration, non-noble metal doping and heterojunction construction. The enhancement mechanisms and synergistic effects in g-C₃N₄-based nanocomposites are highlighted. The remaining challenges and future perspectives of antibacterial g-C₃N₄-based nanocomposites are also discussed.

Ultrafast conversion of carcinogenic 4-nitrophenol into 4-aminophenol in the dark catalyzed by surface interaction on BiPO4/g-C3N4 nanostructures in the presence of NaBH4

The heterogeneous catalytic conversion of pollutants into useful industrial compounds is a two-goals at once process, which is highly recommended from the environmental, economic, and industrial points of view. In this regard, design materials with high conversion ability for a specific application is required to achieve such a goal. Herein, the synthesis conditions for the fabrication of BiPO4 nanorod bundles supported on g-C3N4 nanosheets as heterojunction composites was achieved using a facile ex situ chemical deposition for the reductive conversion of carcinogenic 4-nitrophenol (4-NP) into 4-aminophenol (4-AP). To better understand the mechanistic reduction pathways, BiPO4/g-C3N4 composites with varying ratios where obtained. The morphology and structure of BiPO4/g-C3N4 composites were checked using several methods: XRD, FE-SEM, HRTEM, XPS, and FT-IR, and it was found that hexagonal phase BiPO4 nanorod bundles were randomly distributed on the g-C3N4 nanosheets. Overall, the reduction ability of BiPO4/g-C3N4 composites was far better than bare BiPO4 and g-C3N4. A total reductive conversion of 4-NP at a concentration of 10 mg L-1 into 4-AP was found with 50% BiPO4/g-C3N4 composite within only one minute of reaction. Moreover, the presence of reducing agent (NaBH4) enhanced the kinetic rate constant up to 2.914 min-1 using 50% BiPO4/g-C3N4, which was much faster than bare BiPO4 (0.052 min-1) or g-C3N4 (0.004 min-1). The effects of some operating parameters including the initial concentration of 4-NP and catalyst dosage were also evaluated during the experiments. BiPO4/g-C3N4 showed great stability and recyclability, wherein, the catalytic reduction efficiency remains the same after five runs. A plausible 4-NP reduction mechanism was discussed. The high catalytic activity with the good stability of BiPO4/g-C3N4 make it a potential candidate for the reduction of nitroaromatic compounds in real wastewaters.

Heterojunction of N/B/RGO and g-C3N4 anchored magnetic ZnFe2O4@ZnO for promoting UV/Vis-induced photo-catalysis and in vitro toxicity studies

To promote the low photocatalytic efficiency caused by the recombination of electron/hole pairs and widen the photo-response wavelength window, ZnFe₂O₄@ZnO-N/B/RGO and ZnFe₂O₄@ZnO-C₃N₄ ternary heterojunction nanophotocatalysts were designed and successfully prepared through a sol-gel technique. In comparison to bare ZnFe₂O₄ and ZnO, the ZnFe₂O₄-ZnO@N/B/RGO and ZnFe₂O₄@ZnO-C₃N₄ ternary products showed highly improved photocatalytic properties in the degradation of methyl orange (MO) under ultra-violet (UV) and visible light irradiation. Various physicochemical properties of the photocatalysts were evaluated through field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM) techniques. The observations indicated that the ternary heterojuncted ZnFe₂O₄@ZnO-N/B/RGO absorbs lower energy visible light wavelengths, which is an enhancement in the photocatalytic properties of ZnFe₂O₄@ZnO loaded on reduced graphene oxide (RGO) nanosheets and graphite-like carbon nitride (g-C₃N₄). This gives the catalyst photo-Fenton degradation properties.

Microwave-assisted fabrication of g-C3N4 nanosheets sustained Bi2S3 heterojunction composites for the catalytic reduction of 4-nitrophenol

In this work, we report a stable g-C₃N₄, Bi₂S₃, and g-C₃N₄/Bi₂S₃ composite catalysts were prepared via a facile one-pot microwave-assisted method and characterized. The orthorhombic phase and nearly spherical shape of the particles with an average diameter of 5-25 nm of g-C₃N₄/Bi₂S₃ composite were obtained from XRD and TEM. The composite also exhibits a high surface area (32.15 m²/g), which may provide convenient transportation and diffusion for substrate molecule. The optical studies were displayed the g-C₃N₄/Bi₂S₃ composite has a sharp absorption band in the visible region, higher charge separation, and reduced recombination rate. These results show that the Bi₂S₃ NPs have good crystallinity and are uniformly deposited on the surface of the g-C₃N₄ sheet. The catalytic performance of the g-C₃N₄/Bi₂S₃ composite for the reduction of 4-NP to 4-AP was exhibited approximately 100%, which is 1.48 and 2.34 times higher than the Bi₂S₃ and g-C₃N₄ catalysts, respectively. The pseudo-first-order rate constant was estimated as 1.648 × 10 ^-2 min^-1 for the reduction of 4-NP using g-C₃N₄/Bi₂S₃ composite in 1 h reaction time. The effect of catalyst dosage (0-30 mg) was also investigated for the reduction of 4-NP using g-C₃N₄/Bi₂S₃ composite catalyst. Moreover, the reusability of the g-C₃N₄/Bi₂S₃ composite was exhibited a better reduction of the 4-NP even after 5 cycles and it was found that 8% reduction in the initial reduction rate. The obtained results from this study show that g-C₃N₄/Bi₂S₃ composite has the potential efficiency and stability to make it an ideal catalyst for the reduction of toxic effluents and wastewater treatment.