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Graphene oxide (GO) and reduced GO (rGO) have become the most exciting material in the applications for photocatalysts. However, the GO composite film-based high-activity photocatalyst is usually not durable in aqueous solution. Therefore, in this paper, the non-woven polyester fabric (NWPF)-supported cuprous oxide nanoparticles (Cu2O) decorated on rGO (Cu2O/rGO@NWPF) membrane were suggested to synthesize via chemical reduction method. The Cu2O/rGO@NWPF nanocomposite was characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller method, and energy-dispersive X-ray spectroscopy analysis. The combination of rGO and Cu2O particles supported on NWPF exhibited enhanced photocatalytic degradation of methylene blue (MB) under solar light and achieved 96% of MB removal efficiency in 120 min. The photocatalytic mechanism and the synergistic effects between Cu2O nanoparticles and rGO sheets were comprehensively investigated. The Cu2O/rGO@NWPF catalyst showed excellent stability with retained catalytic activity in four consecutive recycles. The obtained results indicated that the Cu2O/rGO@NWPF composite has a good application potential to large-scale water treatment at lakes or rivers.

In this study, a simple one-step synthetic approach using lotus seed pods and iron(III) chloride has been developed to prepare Fe3O4 nanoparticles loaded activated carbon composite (Fe3O4-NPs/AC) for removal of Ni(II) ions from aqueous solution. The physical and chemical characteristics of Fe3O4-NPs/AC were comprehensively analyzed by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and Brunauer–Emmett–Teller analysis. On account of the combined advantages of lotus seed pod carbon and Fe3O4 nanoparticles, the Fe3O4-NPs/AC showed excellent adsorption efficiency for Ni(II) ions with the maximum adsorption capacity of 50.72 mg g-1 at optimal conditions (pH of 6, contact time of 60 min, 25 °C, and adsorbent dosage of 4.0 g L-1). It was found that the adsorption process of Ni(II) on Fe3O4-NPs/AC was feasible, spontaneous and endothermic, and was well described by the Langmuir isotherm model and pseudo-first-order kinetic equation. The Fe3O4-NPs/AC composite also showed good reusability with removal efficiency of greater than 86.25% after five cycles of reuse.

Herein, the single-atom Ni site heterogeneous catalysts supported by the UiO-66 structure (University of Oslo-66 metal organic framework) were successfully synthesized by a postsynthetic metalation method, where Ni ions are covalently attached to the missing-linker defect sites at zirconium oxide clusters (Zr6O4(OH)4) in as-prepared UiO-66 structure, [Zr6O4(OH)4(BDC)(DMF)10(OH)10] (BDC (benzene-1,4-dicarboxylate), DMF (dimethylformamide)). The structure properties of the catalysts were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), N2 adsorption-desorption isotherms (BET), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). It was found that single-atom Ni heterogeneous catalysts supported by the UiO-66 structure, UiO-66/Ni1.0 [Zr6O4(OH)4(C8H4O4)(DMF)10(OH)8Ni2(OH)2(Cl)2], showed a sphere-like morphology with a high specific surface area as well as good thermal stability. Specifically, the as-prepared UiO-66/Ni1.0 exhibited the excellent catalytic activity and stability for 4-nitrophenol reduction in terms of low activation energy (Ea=23.15 kJ mol−1), high turnover frequency (76.19 molecules g-1 min-1), and high apparent rate constant (kapp=0.956min−1). In addition, methylene blue (MB) was also chosen as the organic dye model for catalytic reduction reaction. The kapp and TOF for the reduction of MB using UiO-66/Ni1.0 were 0.787 min−1 and 33.89×1020 molecules g−1 min−1, respectively.

This paper presents a green synthesis method for growing carbon quantum dots (CQDs) from turmeric starch. The CQDs were then used as reducing agents and stabilizers to synthesize dual-shaped gold nanoparticles (AuNPs) with spherical and triangular shapes. In addition to the advantages of CQDs in catalysis, such as their large surface area and the presence of functional groups, including hydroxyl (-OH) and carbonyl (-C=O), as evidenced by FTIR analysis, the material also demonstrates excellent electron transfer efficiency. This efficiency is attributed to the synergistic interaction between AuNPs and the functional groups on CQDs, facilitating catalytic electron transfer processes in reducing 4-nitrophenol (4-NP). Furthermore, the obtained AuNPs/CQDs material benefits from the plasmonic properties of AuNPs, enhancing light absorption and accelerating catalytic reactions. As a result, AuNPs/CQDs have been successfully applied to effectively catalyze the reduction of 4-NP in aqueous media with high efficiency. The synergy between the plasmonic effect of AuNPs and the catalytic properties of CQDs results in a high catalytic efficiency and a fast reaction time of 20 min, making this method simple, rapid, scalable, and highly effective for environmental pollution remediation.

In the context of increasing water pollution by organic dyes, the development of environmentally friendly materials with effective treatment capabilities is urgently needed. This study aimed to synthesize a biodegradable nAg-CS/PVA hydrogel with high compatibility for dye adsorption applications. The dual gamma irradiation technique successfully synthesized nAg-CS/PVA hydrogel material from the immobilization of nAg-CS particles (particle size of 24.95 nm, a polydispersity index of 0.202, and zeta potential of +20.7 mV) into the PVA polymer network. The formation of nAg-CS/PVA was confirmed by FTIR, DSC, and FESEM analyses, which showed that the strong interaction between the functional groups of chitosan and PVA, combined with the superior complexation ability of Ag, contributed to the enhancement of gelation and swelling properties. The synthesized hydrogel was applied to remove methylene blue (MB) with a maximum adsorption capacity (qm) of 285.71 mg/g under optimal conditions (PVA solution 150 g/L, PVA:nAg-CS volume ratio of 8:2 and irradiation dose of 30 kGy). The neutron activation confirmed the successful immobilization of Ag nanoparticles, ensuring the minimal release of silver ions into the environment. These findings highlight the potential of nAg-CS/PVA hydrogel as an efficient and environmentally friendly material for the treatment of dye-contaminated wastewater.

This study is devoted to synthesis of nanosized zincated hydroxyapatite (Zn-HA) and its utilization as a heterogeneous photo-Fenton-like catalyst for degradation of methylene blue (MB) in aqueous solution. The prepared catalyst was characterized by various techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, and Fourier transform infrared spectroscopy. The catalytic activity of Zn-HA towards MB and the effects of various experimental factors such as pH, zinc substitution degrees, initial MB concentration, and H2O2 dosage were studied in detail. The results showed that the zinc substitution degree of 0.4 is optimal to get the highest degradation efficiency under conditions of pH = 10, H2O2 dosage of 0.05 M, and MB concentration of 30 mg/L for a contact time of 120 min. The degradation mechanism was proposed and discussed thoroughly. Besides, the ability of long-term use for the synthesized catalyst was also evaluated.

This article reports the synthesis of the University of Oslo-66 (UiO-66) and its application to simultaneous voltammetric determination of ascorbic acid (AA) and acetaminophen (AC). The zirconium terephthalate samples synthesized in different solvents (the N,N′-dimethylformamide, acetonitrile, and ethanol) are characterized with XRD, SEM, TG, nitrogen adsorption/desorption isotherm, and XPS techniques. Among solvents the N,N′-dimethylformamide solvent is favorable for the UiO-66 phase formation. The synthesized UiO-66 material with spherical particles with round 100–150 nm in diameters possesses a large specific surface area. The UiO-66 is used as electrode modifier to develop UiO-66 modified glassy carbon electrode for determining simultaneous AA and AC. The UiO-66 modified electrode demonstrates excellent electrocatalytic performance towards AA and AC oxidation compared with bare GCE. The anodic peak current varies linearly to AA and AC concentration in the range of 0.02 to 2.92 μM. The level of detection (S/N = 3) was found to be 0.019 and 0.018 μM, respectively. The proposed differential pulse voltammetry method was used to determine individually or simultaneously AA and AC in pharmaceutical formulations. The results are not significant different from those analyzed by high-performance liquid chromatography.

A simple approach was developed to synthesize cobalt ferrite nanoparticles/graphene quantum dots (CF/GQDs). The material was prepared from a homogeneous mixture of iron nitrate, cobalt nitrate, and starch at 140, 180 and 200 °C in a 24 h thermal hydrolysis process. The obtained materials were characterised by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, photoluminescence spectroscopy, vibrating-sample magnetometry, and nitrogen adsorption/desorption isotherms. Cobalt ferrite crystals of around 8–10 nm and graphene quantum dots formed directly at 200 °C. Stacking GQDs sheets onto the CF nanoparticles resulted in CF/GQDs nanoparticles. The nanocomposite exhibits satisfactory fluorescent and superparamagnetic properties, which are vital for catalytic applications. The CF/GQDs catalyse significantly the degradation of methylene blue (MB) under visible light. The catalyst can be recycled with an external magnetic field and displays suitable stability. Also, it was reused in three successive experiments with a loss of efficiency of about 5%. The CF/GQDs are considered as an efficient photocatalyst for MB degradation and other dyes.

Diatomite (DE) has attracted considerable attention owing to its abundance, low cost, and potential for a wide variety of applications. This work reports the development of mesoporous wool-ball-like (WBL) microspheres from natural DE through a simple hydrothermal treatment. We discovered that the presence of cetyltrimethylammonium bromide is a prerequisite for generating monodispersed WBL microspheres. The mechanism for the transformation of pristine DE into mesoporous microspheres through dissolution–recrystallization was clearly investigated. Interestingly, the microspheres exhibited a specific surface area 25–60 times larger than that of the pristine DE. The application of WBL microsphere DE as an effective support for metallic catalysts in the toluene total oxidation reaction was demonstrated.

In the present paper, a nanocomposite of rGO and TiO 2 nanoparticles (TiO 2 /rGO) was prepared by a facile synthesis method with peroxo titanium complexes as TiO 2 precursor. The morphology and structure of TiO 2 /rGO nanocomposite were investigated by X-ray diffraction (XRD), Raman spectroscopy, nitrogen adsorption/desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX)-elementary mapping spectroscopy. It was found that TiO 2 /rGO nanocomposites with high surface area were formed involving strong coupling interaction between TiO 2 and rGO. Based on the synergistic effect of rGO and TiO 2 nanoparticles, an electrochemical sensor for paracetamol (PAR) and codeine (COD) was fabricated by modifying the glassy carbon electrode (GCE) with TiO 2 /rGO material. The cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DP-ASV) were used to determine the electrochemical signals of these analytes. CVs of this sensor provided distinct and sharp oxidation peaks for PAR and COD. The DP-ASV parameters were optimized. It was found that the proposed electrode exhibits excellent electrochemical activity toward PAR and COD. Under the optimal conditions, the A low limit of detection of 0.28 µM for PAR and 0.25 µM for COD were achieved in the linear range from 0.4 to 2.0 µM for both PAR and COD. The proposed method was free from the interference effects of glucose, ascorbic acid, caffeine, and other inorganic salts. This electrode was also highly stable and sensitive making it applicable in the analysis of various real pharmaceutical samples. Graphical abstract