Green in situ synthesis of sandwich-like W-bridged siligraphene (g-SiC@WC@g-SiC) heterostructure from Saccharum Ravennae gum for ultrahigh-rate photodegradation of acetaminophen

Herein, the sandwich-like W-bridged siligraphene (W/g-SiC) as a heterojunction of WC and siligraphene nanosheets have been first accomplished via a simple green synthesis using Saccharum Ravennae gum as a natural Si and W sources and gelatin as a natural C and N sources. In a magnesiothermic process, Si and C atoms bond together and form a graphene-like structure where half of the C atoms are replaced by Si atoms. The presence of W in the natural precursor creates a W-doped siligraphene structure. Tungsten in the form of carbide (WC) creates a heterojunction with g-SiC, which reduces the bandgap. According to the experimental and computational data, the proposed structure of W/g-SiC was predicted by replacing the W atoms with Si atoms and bonding with C atoms in the siligraphene structure. The W-C bond in this structure is elongated and the W atom comes out of the siligraphene sheet and is placed between two siligraphene layers to interact with three carbons from the next layer. Under visible light irradiation, holes are generated on the g-SiC layers and electrons in the WC interlayer, which makes it a highly efficient photocatalyst with ultrafast charge separation and active surface for the removal of Acetaminophen.

In Situ Synthesis of Doped Bio-Graphenes as Effective Metal-Free Catalysts in Removal of Antibiotics: Effect of Natural Precursor on Doping, Morphology, and Catalytic Activity

Wastewater contaminated with antibiotics is a major environmental challenge. The oxidation process is one of the most common and effective ways to remove these pollutants. The use of metal-free, green, and inexpensive catalysts can be a good alternative to metal-containing photocatalysts in environmental applications. We developed here the green synthesis of bio-graphenes by using natural precursors (Xanthan, Chitosan, Boswellia, Tragacanth). The use of these precursors can act as templates to create 3D doped graphene structures with special morphology. Also, this method is a simple method for in situ synthesis of doped graphenes. The elements present in the natural biopolymers (N) and other elements in the natural composition (P, S) are easily placed in the graphene structure and improve the catalytic activity due to the structural defects, surface charges, increased electron transfers, and high absorption. The results have shown that the hollow cubic Chitosan-derived graphene has shown the best performance due to the doping of N, S, and P. The Boswellia-derived graphene shows the highest surface area but a lower catalytic performance, which indicates the more effective role of doping in the catalytic activity. In this mechanism, O2 dissolved in water absorbs onto the positively charged C adjacent to N dopants to create oxygenated radicals, which enables the degradation of antibiotic molecules. Light irradiation increases the amount of radicals and rate of antibiotic removal.

Novel synthesis of siligraphene/tungstates (g-SiC/AWO) with promoted transportation of photogenerated charge carriers via direct Z-scheme heterojunctions

We developed here the efficient photocatalysts for the removal of high concentrations of tetracycline under visible light by immobilizing the AWO (A = Ag, Bi, Na) nanocrystals on the surface of siligraphene (g-SiC) nanosheets. The g-SiC/AWO composites was synthesized by magnesiothermic synthesis of g-SiC and sonochemical immobilization of tungstates. These new heterojunctions of g-SiC/tungstates show superior photocatalytic activities in the degradation of high concentrations of tetracycline and 97, 98, and 94% of tetracycline were removed by using low amounts of g-SiC/Ag₂WO₄, g-SiC/Bi₂WO₆, and g-SiC/Na₂WO₄ catalysts, respectively. Based on band structures, the band gaps reduce and the photocatalytic activities were extremely enhanced due to the shortening of electron transfer distance through the Z-scheme mechanism. Also, the graphenic structure of g-SiC is another parameter that was effective in improving photocatalytic performance by increasing the electron transfer and decreasing the rate of electron-hole recombination. Furthermore, the π back-bonding of g-SiC with metal atoms increases the electron-hole separation to enhance the photocatalytic activity. Interestingly, g-SiC composites (g-SiC/AWO) showed much higher photocatalytic properties compared to graphene composites (gr/AWO) and can remove the tetracycline even at dark by producing the oxygenated radicals via adsorption of oxygen on the positive charge of Si atoms in siligraphene structure.

Spray-Based Method for Protecting and Restoring Historic Adobe Walls Using Nanomontmorillonite Clay

Restoring and protecting historic buildings worldwide are important because heritage buildings are records of the civilizations of various countries. Herein, nanotechnology was used to restore historic adobe walls. According to the Iran Patent and Trademark Office (IRPATENT) 102665, nanomontmorillonite clay has been selected as a natural and compatible material with adobe. Furthermore, it has been used as nanospray to be a minimally invasive method to fill cavities and cracks in the adobe surface. Various percentages of nanomontmorillonite clay (1-4%) in the ethanol solvent and the frequency of spraying on the wall surface were evaluated. Scanning electron microscopy and atomic force microscopy images, porosity tests, water capillary absorption, and compressive strength tests were used to evaluate the efficiency of the method, analyze cavity filling, and detect the optimal percentage of nanomontmorillonite clay. Results indicate that the double use of the 1% nanomontmorillonite clay solution exhibited the best results, filled the cavities, and reduced the pores on the surface of the adobe, increasing compressive strength and reducing water absorption and hydraulic conductivity. The use of a more dilute solution causes the nanomontmorillonite clay to penetrate deeply into the wall. This innovative method can help mitigate the existing disadvantages of historic adobe walls.

Porous biomorphic silica@ZnO nanohybrids as the effective photocatalysts under visible light

In this study, zinc oxide nanohybrids based on functionalized bio-silica were synthesized and used for the degradation of Congo red under visible light. Diatom was used as a Si natural source with hierarchical nanostructures to produce porous silica support. Functionalized porous silica is a good candidate for direct immobilization of metal oxide and therefore of interest as the catalyst. Here, six hybrids of functionalized bio-silica and ZnO were synthesized and characterized by FT-IR, XRD, SEM/EDX, BET/BJH, and UV-Vis spectroscopy. Then, the synthesized catalysts were subjected to degradation of different anionic azo dyes (Congo red, methyl orange, and methyl red) under visible light irradiation. The results show the decrease of band gap in bio-silica@ZnO hybrids which enhance the photocatalytic properties of hybrids due to the shifting to visible light adsorption. The best photocatalytic result of SiO₂@ZnO hybrid was obtained from chitosan-based amino-functionalized silica due to the best functionalization, highest loading of ZnO, low band gap, and filling of diatom pores with functional groups.

Novel siligraphene/g-C3N4 composites with enhanced visible light photocatalytic degradations of dyes and drugs

In this research, a novel graphene-like SiC (siligraphene) was synthesized using a natural precursor and used to improve the photocatalytic activity of g-C₃N₄. The synthesized siligraphene has shown an excellent photocatalytic property due to its low band-gap and graphene-like structure which increases the electron transfer and reduces the electron-hole recombination rate and can improve the photocatalytic activity. Also, the positive charged Si atoms in siligraphene structure can adsorb oxygen to produce radicals that can promote the oxidation reaction. However, commercial β-SiC has exhibited very poor photocatalytic properties. As we know, g-C₃N₄ is a potential material for photocatalytic applications. Here, the novel siligraphene/g-C₃N₄ composites were successfully synthesized to enhance the photocatalytic properties of g-C₃N₄ in the degradation of model dyes (Congo red, Methyl red, and Methyl orange) and model drugs (Acetaminophen and Tetracycline) under visible light irradiation. Results show that siligraphene/g-C₃N₄ composite exhibits much better photocatalytic properties than pure g-C₃N_4. This enhanced photocatalytic properties can be justified by the enlarged surface area, suitable band gap, excellent electron properties, appropriate surface charge, and efficient migration of electron in siligraphene/g-C₃N₄ composite.

Activated Carbon/MoO3: Efficient Catalyst for Green Synthesis of Chromeno[d]pyrimidinediones and Xanthenones

BACKGROUND

Nanoscale metal oxide catalysts have been extensively employed in organic reactions because they have been found to influence the chemical and physical properties of bulk material. The chromene (benzopyran) nucleus constitutes the core structure in a major class of many biologically active compounds, and interest in their chemistry consequently continues because of their numerous biological activities. The xanthene (dibenzopyran) derivatives are classified as highly significant compounds which display a number of various bioactive properties. Pyrimidinones have also gained interest due to their remarkable biological utilization, such as antiviral, antibacterial, antihypertensive, antitumor, and calcium blockers effects.

OBJECTIVE

The aim of this work presented herein was to prepare activated carbon/MoO3 nanocomposite and explore its role as a green and recyclable catalyst for the synthesis of chromeno[d]pyrimidinediones and xanthenones under ethanol-drop grinding at room temperature.

METHODS

The activated carbon/MoO3 nanocomposite was prepared successfully via a simple route in which the carbonization of gums as new natural precursors was used for the synthesis of activated carbon. This nanocomposite was then effectively used in a reaction of 3,4-methylenedioxyphenol, aromatic aldehydes, and active methylene compounds, including 1,3-dimethylbarbituric acid and dimedone, to synthesize a series of chromeno[d]pyrimidinediones and xanthenones in high yields. The synthesized catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), Powder x-ray diffractometry (XRD), Scanning electron microscope (SEM), Raman spectroscopy, and also by TGA analysis. Confirmation of the structures of compounds 5(a-g) and 6(a-g) were also established with IR, 1H NMR, and 13C NMR spectroscopic data and also by elemental analyses.

RESULTS

A number of 6,8-dimethyl-10-phenyl-6,10-dihydro-7H-[1,3]dioxolo[4´,5´:6,7]chromeno[2,3- d]pyrimidine-7,9(8H)-diones and 7,7-dimethyl-10-(4-methylphenyl)-6,7,8,10-tetrahydro-9H-[1,3]dioxolo[ 4,5-b]xanthen-9-ones were effectively synthesized using activated carbon/MoO3 nanocomposite (0.05 gr) as a catalyst under ethanol-drop grinding at room temperature. The desired products were obtained in high yields (93-97%) within short reaction times (15-20 min).

CONCLUSION

This paper investigates the catalytic potential of the synthesized activated carbon/MoO3 nanocomposite for the preparation of chromeno[d]pyrimidinediones and xanthenones under the ethanol-drop grinding procedure. The mildness of the reaction conditions, high yields of products, short reaction times, experimental simplicity, and avoiding the use of harmful solvents or reagents makes this procedure preferable for the synthesis of these compounds.

In Vitro Characterization and Evaluation of the Cytotoxicity Effects of Nisin and Nisin-Loaded PLA-PEG-PLA Nanoparticles on Gastrointestinal (AGS and KYSE-30), Hepatic (HepG2) and Blood (K562) Cancer Cell Lines

The aim of this study was an in vitro evaluation and comparison of the cytotoxic effects of free nisin and nisin-loaded PLA-PEG-PLA nanoparticles on gastrointestinal (AGS and KYSE-30), hepatic (HepG2), and blood (K562) cancer cell lines. To create this novel anti-cancer drug delivery system, the nanoparticles were synthesized and then loaded with nisin. Subsequently, their biocompatibility, ability to enter cells, and physicochemical properties, including formation, size, and shape, were studied using hemolysis, fluorescein isothiocyanate (FITC), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and scanning electron microscopy (SEM), respectively. Then, its loading efficiency and release kinetics were examined to assess the potential impact of this formulation for the nanoparticle carrier candidacy. The cytotoxicities of nisin and nisin-loaded nanoparticles were evaluated by using the MTT and Neutral Red (NR) uptake assays. Detections of the apoptotic cells were done via Ethidium Bromide (EB)/Acridine Orange (AO) staining. The FTIR spectra, SEM images, and DLS graph confirmed the formations of the nanoparticles and nisin-loaded nanoparticles with spherical, distinct, and smooth surfaces and average sizes of 100 and 200 nm, respectively. The loading efficiency of the latter nanoparticles was about 85-90%. The hemolysis test represented their non-cytotoxicities and the FITC images indicated their entrance inside the cells. An increase in the percentage of apoptotic cells was observed through EB/AO staining. These results demonstrated that nisin had a cytotoxic effect on AGS, KYSE-30, HepG2, and K562 cancer cell lines, while the cytotoxicity of nisin-loaded nanoparticles was more than that of the free nisin.

Extraction of caffeine and catechins using microwave-assisted and ultrasonic extraction from green tea leaves: an optimization study by the IV-optimal design

In this research, optimal conditions for extraction of caffeine and polyphenols were established from Iranian green tea leaves. In the first step, caffeine was extracted with efficacy about 86% versed to 4.5% of EGC + EGCG. The EGCG + EGC was extracted from partially decaffeinated green tea leaves through microwave-assisted extraction (MAE) and ultrasound-assisted extraction (USE) with efficiency levels of 95 and 85%, respectively. The best results for the MAE process were obtained with 7.8 min and three number of extraction cycles and for the USE process were as followed: time 57 min, temperature 65 °C, and the number of extraction cycles 3. The total phenol content values at the best conditions of MAE and the USE processes were 125 ± 5 and 96 ± 6 mg gallic acid/g DW. The 50% inhibition (IC₅₀) on 1,1-diphenyl-2-picrylhydrazyl (DPPH) were 56 and 66 mg/g of phenol for the MAE and USE processes.

An operationally simple green procedure for the synthesis of dihydropyrimido[4,5-d]pyrimidinetriones using CuI nanoparticles as a highly efficient catalyst

A green, efficient and simple protocol was developed for the synthesis of dihydropyrimido[4,5-d]pyrimidinetrione derivatives via a coupling reaction of 6-aminouracils, aromatic aldehydes and urea in aqueous media in the presence of nano-crystalline CuI at room temperature. The products were obtained in high yields. CuI nanoparticles can be recycled three times without significant loss of catalytic activity.

Molybdenum peroxo nanohybrid compounds in different structures and catalytic properties

The new nanohybrid of molybdenum peroxo compounds based on pyridine dicarboxylate ligands were synthesized by employing one-pot procedure in aqueous media and characterized by infrared (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal analysis (TGA/DTA). The prepared compounds were used as catalysts for the epoxidation of cyclohexene and cyclooctene in a mild condition. Results showed that these molybdenum peroxo compounds have significant potentials as oxidants in oxygen atom transfer reactions. These reagents oxidized olefins to epoxides in presence of hydrogen peroxide with high conversions and selectivity. Comparison of the relative reactivity of those compounds shows that the electronic nature of ligands influences the rate and activity of oxygen transfer reaction. It is also found that the addition of organic ligands not only prevented the formation of diols in epoxidation of alkenes, but also increased the reaction rate.