Efficient activation of persulfate by Fe3O4@β-cyclodextrin nanocomposite for removal of bisphenol A

Experimental studies were conducted to investigate the degradation of bisphenol A (BPA) by using persulfate (PS) as the oxidant and Fe₃O₄@β-cyclodextrin (β-CD) nanocomposite as a heterogeneous activator. The catalytic activity was evaluated in consideration of the effect of various parameters, such as pH value, PS concentration and Fe₃O₄@β-CD load. The results showed that 100% removal of BPA was gained at pH 3.0 with 5 mM PS, 1.0 g L⁻¹ Fe₃O₄@β-CD, and 0.1 mM BPA in 120 min. Further, the catalytic activity of Fe₃O₄@β-CD nanocomposite was observed as much higher when compared with Fe₃O₄ nanoparticles alone. The sulfate and hydroxyl radicals referred to in the Fe₃O₄@β-CD/PS system were determined as the reactive species responsible for the degradation of BPA by radical quenching and electron spin resonance (ESR) tests. In addition, the catalyst also possessed with accepted reusability and stability. On the basis of the results of the effect of chloride ions (Cl⁻), β-CD was found to play a crucial role in reducing interference from Cl⁻ ions, and lead to achieve higher removal efficiency for BPA in Fe₃O₄@β-CD/PS system. A possible mechanistic process of BPA degradation was proposed according to the identified intermediates by gas chromatography-mass spectroscopy (GC-MS).

Persulfate (PS), the most commonly used activator for in situ chemical oxidation (ISCO), could couple with Fe₃O₄@β-CD for effectively degrading BPA.     

A facile route to magnetic mesoporous core–shell structured silicas containing covalently bound cyclodextrins for the removal of the antibiotic doxycycline from water

The excessive use of antibiotics has led to various environmental problems; the control and separation of these antibiotics are important in environmental science. Herein, a novel mesoporous nanocomposite, Fe₃O₄@SiO₂@mSiO₂-CD, has been synthesized for the removal of antibiotic compounds from aqueous media. The well-designed nanocomposite is composed of β-cyclodextrin functionalized surfaces, ordered mesoporous silica shells with large radially oriented mesopores, and nonporous silica-coated magnetic cores (Fe₃O₄). The synergistic action of both the mesoporous structure and the accessible cavity of β-cyclodextrin ensures the good adsorption of doxycycline. Furthermore, the Fe₃O₄@SiO₂@mSiO₂-CD nanocomposite can be collected, separated and easily recycled from aqueous solution using an external magnet.

The controllable synthesis of a core–shell structured mesoporous organic–inorganic hybrid nanocomposite, Fe₃O₄@SiO₂@mSiO₂-CD, which demonstrates good adsorption of doxycycline.     

Novel magnetic g-C3N4/α-Fe2O3/Fe3O4 composite for the very effective visible-light-Fenton degradation of Orange II

A novel magnetic heterogeneous g-C₃N₄/α-Fe₂O₃/Fe₃O₄ catalyst was successfully synthesized through a simple hydrothermal method. The structure, morphology, and optical properties of the catalyst were characterized. The photocatalytic activity of the heterogeneous g-C₃N₄/α-Fe₂O₃/Fe₃O₄ catalyst for the photo-Fenton degradation of Orange II in the presence of H₂O₂ irradiated with visible light (λ > 420 nm) at neutral pH was evaluated. The g-C₃N₄/α-Fe₂O₃/Fe₃O₄ photocatalyst was found to be an excellent catalyst for the degradation of Orange II and offers great advantages over the traditional Fenton system (Fe(ii/iii)/H₂O₂). The results indicated that successfully combining monodispersed Fe₃O₄ nanoparticles and g-C₃N₄/α-Fe₂O₃ enhanced light harvesting, retarded photogenerated electron–hole recombination, and significantly enhanced the photocatalytic activity of the system. The g-C₃N₄/α-Fe₂O₃/Fe₃O₄ (30%) sample gave the highest degradation rate constant, 0.091 min⁻¹, which was almost 4.01 times higher than the degradation rate constant for α-Fe₂O₃ and 2.65 times higher than the degradation rate constant for g-C₃N₄/α-Fe₂O₃ under the same conditions. A reasonable mechanism for catalysis by the g-C₃N₄/α-Fe₂O₃/Fe₃O₄ composite was developed. The g-C₃N₄/α-Fe₂O₃/Fe₃O₄ composite was found to be stable and recyclable, meaning it has great potential for use as a photo-Fenton catalyst for effectively degrading organic pollutants in wastewater.

A novel magnetic heterogeneous g-C₃N₄/α-Fe₂O₃/Fe₃O₄ catalyst was firstly synthesized and exhibited very effective visible-light-Fenton degradation of Orange II at neutral pH.     

Microstructural analysis,magnetic properties,magnetocaloric effect,and critical behaviors of Ni0.6Cd0.2Cu0.2Fe2O4 ferrites prepared using the sol–gel method under different sintering temperatures

This work focuses on the microstructural analysis, magnetic properties, magnetocaloric effect, and critical exponents of Ni_0.6Cd_0.2Cu_0.2Fe₂O₄ ferrites. These samples, denoted as S1000 and S1200, were prepared using the sol–gel method and sintered separately at 1000 °C and 1200 °C, respectively. XRD patterns confirmed the formation of cubic spinel structures and the Rietveld method was used to estimate the different structural parameters. The higher sintering temperature led to an increased lattice constant (a), crystallite size (D), magnetization (M), Curie temperature (T_C), and magnetic entropy change (−ΔS_M) for samples that exhibited second-order ferromagnetic–paramagnetic (FM–PM) phase transitions. The magnetic entropy changed at an applied magnetic field (μ₀H) of 5 T, reaching maximum values of about 1.57–2.12 J kg⁻¹ K⁻¹, corresponding to relative cooling powers (RCPs) of 115 and 125 J kg⁻¹ for S1000 and S1200, respectively. Critical exponents (β, γ, and δ) for samples around their T_C values were studied by analyzing the M(μ₀H, T) isothermal magnetizations using different techniques and checked by analyzing the −ΔS_Mvs. μ₀H curves. The estimated values of β and γ exponents (using the Kouvel–Fisher method) and δ exponent (from M(T_C, μ₀H) critical isotherms) were β = 0.443 ± 0.003, γ = 1.032 ± 0.001, and δ = 3.311 ± 0.006 for S1000, and β = 0.403 ± 0.008, γ = 1.073 ± 0.016, and δ = 3.650 ± 0.005 for S1200. Obviously, these critical exponents were affected by an increased sintering temperature and their values were different to those predicted by standard theoretical models.

This work focuses on the microstructural analysis, magnetic properties, magnetocaloric effect, and critical exponents of Ni_0.6Cd_0.2Cu_0.2Fe₂O₄ ferrites.     

A new strategy for the sensitive electrochemical determination of nitrophenol isomers using β-cyclodextrin derivative-functionalized silicon carbide

In the present study, thiol β-cyclodextrin (SH-CD) and ethylenediamine β-cyclodextrin (NH₂-β-CD) were simultaneously grafted on the same interface of an Au NP deposited carboxyl SiC (Au@CSiC) nanocomposite. An electrochemical sensor for the simultaneous determination of nitrophenol isomers (o-nitrophenol, o-NP; p-nitrophenol, p-NP) using SH-CD and NH₂-β-CD functionalized Au@SiC (Au@CSiC-SH/NH₂-CD) nanocomposite was successfully constructed. Differential pulse voltammetry was used to quantify o-NP and p-NP within the concentration range of 0.01–150 μM under the optimal conditions. The detection limit (S/N = 3) of the sensor was 0.019 and 0.023 μM for o-NP and p-NP, respectively, indicating a low detection limit. Interference study results demonstrated that the sensor was not affected in the presence of similar aromatic compounds during the determination of NP isomers, showing high selectivity. The proposed electrochemical sensing platform was successfully used to determine NP isomers in tap water. The low detection limit and high selectivity of the proposed electrochemical sensor were caused by the high surface area, the excellent conductivity, and the more recognized (enriched) NP isomer molecules by SH-β-CD and NH₂-β-CD of the Au@CSiC-SH/NH₂-CD nanocomposite.

An illustration of simultaneous electrochemical determination of nitrophenol isomers using β-cyclodextrin derivative-functionalized silicon carbide.     

Evolution of microstructure and formation mechanism of Nd-Fe-B nanoparticles prepared by low energy consumption chemical method

Nd₂Fe₁₄B nanoparticles were successfully prepared by using a low-energy chemical method. The microscopic characteristics and formation mechanisms of the phases were investigated at each stage during the preparation of Nd-Fe-B nanoparticles. The Nd-Fe-B intermediates, Nd-Fe-B oxides and reduced Nd-Fe-B nanoparticles were detected and analyzed by using TEM, STEM, XRD, SEM, VSM and Rietveld calculations. The results showed that the intermediate of Nd-Fe-B consisted of Fe₃O₄ and Nd and Fe elements surrounded by nitrile organic compounds. The Nd-Fe-B oxide was composed of NdFeO₃ (48.619 wt%), NdBO₃ (31.480 wt%) and α-Fe (19.901 wt%), which was formed by the reaction among Nd, Fe₃O₄ and B₂O₃. NdFeO₃ and NdBO₃ exhibited a perovskite-like lamellar structure, and the grain size was smaller than that of α-Fe. Nd-Fe-B particles were mainly composed of Nd₂Fe₁₄B and α-Fe phases. The small particles of NdFeO₃ and NdBO₃ and the interstitial position between oxide particles and α-Fe were more favorable for the formation of Nd₂Fe₁₄B particles. At the same time, the surface of α-Fe particles can also diffuse to form Nd₂Fe₁₄B nanoparticles. The coercivity of Nd-Fe-B particles was 5.79 kOe and the saturation magnetization was 63.135 emu g⁻¹.

The Nd-Fe-B intermediate was successfully prepared by using a low-energy chemical method.     

Biosynthesis of magnetite and cobalt ferrite nanoparticles using extracts of “hairy” roots: preparation,characterization, estimation for environmental remediation and biological application

The “green” synthesis of magnetite and cobalt ferrite nanoparticles (Fe₃O₄-NPs and CoFe₂O₄-NPs) using extracts of Artemisia annua L “hairy” roots was proposed. In particular, the effect and role of important variables in the ‘green’ synthesis process, including the metal–salt ratio, various counter ions in the reaction mixture, concentration of total flavonoids and reducing power of the extract, were evaluated. The morphology and size distribution of the magnetic nanoparticles (MNPs) depended on the metal oxidation state and ratio of Fe(iii) : Fe(ii) in the initial reaction mixture. MNPs obtained from divalent metal salts in the reaction mixture were non-uniform in size with high aggregation level. Samples obtained by the FeCl₃/FeSO₄ mixture with a ratio of Fe(iii) : Fe(ii) = 1 : 2 showed an irregular shape of the nanoparticles and high aggregation level. MNPs obtained by the FeCl₃/FeSO₄/CoCl₂ mixture showed a regular shape with slight aggregation, and were in the nanosize range (10–17 nm). Thus, this mixture as a metal-precursor was used for MNP biosynthesis in the subsequent experiments. The XRD data showed that the magnetic specimens contained mainly spinel type phase. The data of EDX and XPS analysis indicated that the product of the “green” synthesis was magnetite with some impurities, owing to the obtained ratio of Fe : O being similar to the theoretical atomic ratio of magnetite (3 : 4). The Fe₃O₄-NP samples were superparamagnetic with high magnetization (until 68 emu g⁻¹). The Co-containing MNPs demonstrated low ferromagnetic properties. The MNPs with pure magnetite phase, very good magnetization and uniform size distribution (ca. 12–14 nm) were prepared by the “hairy” root extract characterized by the highest amount of total flavonoids. According to the FTIR data, the synthesized Fe₃O₄-NPs had a core–shell like structure, in which the core was composed of Fe₃O₄, and the shell was formed by bioactive molecules. The presence of several organic compounds (such as flavonoids or carboxylic acids) plays a key role in the suppression of Fe₃O₄-NP aggregation without addition of a stabilizing agents. Synthesized Fe₃O₄-NP samples effectively removed Cu(ii) and Cd(ii) with the maximum adsorption capacity, reaching 29.9 mg g⁻¹ and 33.5 mg g⁻¹, respectively. It is probable that the presence of organic components in extracts plays an important role in the adsorption properties of biosynthesised MNPs. The obtained MNPs were successfully applied to the removal of heavy metal ions in the environmental water samples. Fe₃O₄-NPs also negatively affected plant growth in the case of using “hairy” roots as a test model, and the greatest inhibitory activity (99.56 wt%) was possessed by MNPs with high magnetic properties.

The “green” synthesis of magnetite and cobalt ferrite nanoparticles (Fe₃O₄-NPs and CoFe₂O₄-NPs) using extracts of Artemisia annua L “hairy” roots was proposed.     

Hematite iron oxide nanoparticles: apoptosis of myoblast cancer cells and their arithmetical assessment

Hematite (α-Fe₂O₃) forms iron oxide nanoparticles (NPs) which are thermally stable and have various electrochemical and optochemical applications. Due to their wide applicability, the present work was designed to form the hematite phase of iron oxide (αFe₂O₃NPs) NPs prepared via a solution process. Their cytological performance was checked with C2C12 cells. The crystalline property of the NPs was examined with X-ray diffraction patterns (XRD) and it was found that the size of the particles formed ranged from 12 to 15 nm. Structural information was also identified via field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), which again confirmed that the size of each NP is about 12–15 nm. Surface topographical analysis was done via atomic force microscopy (AFM), which reveals that the size of the distance between two particles is in the range of 12 ± 3 nm. The C2C12 cells were cultured in a humidified environment with 5% CO₂ and were checked via a microscope. The αFe₂O₃NPs were used for cytotoxic evaluation against C2C12 cells. A MTT (3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was utilized to check the viability of cells in a dose-dependent (100 ng mL⁻¹, 500 ng mL⁻¹ or 1000 ng mL⁻¹) manner. The morphology of the cells under the influence of αFe₂O₃NPs for live and dead cells in a wet environment was confirmed via confocal laser scanning microscopy (CLSM). The apoptosis caused due to the αFe₂O₃NPs was evaluated in presence of caspases 3/7 with GAPDH genes, which confirmed the upregulation that is responsible in caspase 3/7 genes, with treatment of C2C12 at low (500 ng mL⁻¹) and high (1000 ng mL⁻¹) doses of αFe₂O₃NPs. Analytical studies were also performed to authenticate the obtained data for αFe₂O₃NPs using parameters such as precision, accuracy, linearity, limits of detection (LOD) and limit of quantitation (LOQ), quantitative recoveries and relative standard deviation (RSD). The analyses play a significant role in investigating the large effect of αFe₂O₃NPs on C2C12 cells.

Hematite (α-Fe₂O₃) forms iron oxide nanoparticles (NPs) which are thermally stable and have various electrochemical and optochemical applications.     

Fullerene–porphyrin hybrid nanoparticles that generate activated oxygen by photoirradiation

The preparation of water-dispersible hybrid nanoparticles comprising fullerene and porphyrin from cyclodextrin complexes is described. In the presence of polyethylene glycol, C₆₀ fullerene and porphyrin were expelled from the cyclodextrin cavity to form fullerene–porphyrin hybrid nanoparticles in water. The fullerene–porphyrin hybrid nanoparticles exhibit improved singlet oxygen generation ability under photoirradiation compared with that of C₆₀ nanoparticles.

Hybrid nanoparticles comprising fullerene and porphyrin are formed via guest exchange reaction of cyclodextrin complexes. The hybrid nanoparticles exhibit singlet oxygen generation ability under photoirradiation.

Water-dispersible colloidal fullerene assemblies, referred to as fullerene nanoparticles (NPs), have recently received increasing attention.^1–3 Fullerene NPs are negatively charged and can be dispersed in water in the absence of any solubilizer. Fullerene NPs demonstrate promise within biological and medical applications, as radical scavengers and photosensitizers for photodynamic therapy. To further extend the applications of fullerene NPs, additional hybridization with desired functional molecules is required. Porphyrin and associated derivatives are highly promising candidates for hybridization with fullerenes to increase photoactivity.⁴ Numerous studies on the complexation of fullerenes with porphyrin molecules using synthetic organic chemistry^5–7 or supramolecular chemistry^8–10 have been reported. Although fullerene NPs have been intensively studied over the last decade, no reliable method to achieve the hybridization of porphyrins with fullerene NPs has been proposed.Poly(ethylene glycol) monomethyl ether (PEG) was recently observed to accelerate the decomposition of fullerene C₆₀–γ-CD complexes in water, which leads to the rapid aggregation of C₆₀ to form water-dispersible C₆₀ NPs.¹¹ In this method, C₆₀–γ-CD complexes can exist as stable isolated molecules in water, enabling the precise size control and step-wise growth of C₆₀ NPs.^12,13 Herein, the preparation of hybrid NPs comprising C₆₀ and hydrophobic porphyrin molecules are reported. C₆₀–γ-CD and porphyrin-trimethyl-β-cyclodextrin (por–TMe-β-CD) complexes are mixed in water in the presence of PEG. Both complexes decompose through the interaction of PEG with the CDs, leading to the formation of C₆₀–porphyrin hybrid NPs (denoted as C₆₀–por NPs). The C₆₀–por NPs are negatively charged and easily disperse in water. Additionally, the ability of C₆₀–por NPs to generate activated oxygen is also evaluated.The C₆₀–γ-CD complex^14,15 and 1–TMe-β-CD complex (Fig. 1)^16–18 were prepared according to a previously described procedure (see the ESI^† for details). The ¹H NMR spectrum of the mixed solution comprising the C₆₀–γ-CD complex and PEG after 1 h incubation at 80 °C shows that the peaks attributed to the C₆₀–γ-CD complexes completely disappeared (Fig. S1^†). Hence, the ¹H NMR data confirm the decomposition of the C₆₀–γ-CD complexes and the formation of water-dispersible C₆₀ NPs, as previously reported.^11–13 The effect of PEG on 1–TMe-β-CD complexes was also investigated by ¹H-NMR as shown in Fig. S2.^† After incubating the mixed solution of 1–TMe-β-CD complex and PEG ([1] = 0.1 mM, [PEG] = 5.0 g L⁻¹) for 1 h at room temperature, peaks attributed to the 1–TMe-β-CD complex were still evident at 4.97 ppm and above 7.7 ppm (Fig. S2(i)^†). Hence, PEG has no influence upon the 1–TMe-β-CD structure at room temperature. Conversely, after incubating for 1 h at 80 °C, a dark purple precipitate formed and the aforementioned ¹H NMR peaks completely disappeared (Fig. S2(ii)^†). In the absence of PEG, the 1–TMe-β-CD complex was stable in water both at room temperature (Fig. S2(iii)^†) and 80 °C (Fig. S2(iv)^†). These results suggest a decomposition route of 1–TMe-β-CD by interaction with PEG at 80 °C, with a concomitant formation of non-dispersible large aggregates.Open in a separate windowFig. 1Chemical structures of porphyrin derivatives used in this study.To obtain hybrid NPs comprising C₆₀ and 1 (C₆₀–1 NPs), PEG (M_w = 2000) was added to an aqueous solution containing C₆₀–γ-CD and 1–TMe-β-CD complexes ([C₆₀] = [1] = 0.1 mM, [PEG] = 5.0 g L⁻¹), which were thereafter incubated at room temperature or 80 °C. The ¹H NMR spectrum of the mixed solution at room temperature shows peaks attributed to γ-CD in the C₆₀–γ-CD complex at 5.03 ppm, TMe-β-CD in the 1–TMe-β-CD complex at 4.97 ppm, and 1 in the 1–TMe-β-CD complex in the region of 7.6–8.5 ppm (Fig. 2a(i)). The data indicate that PEG fails to induce the decomposition of the C₆₀–γ-CD and 1–TMe-β-CD complexes at room temperature. Conversely, after the mixture was heated at 80 °C for 1 h, the peaks attributed to the C₆₀–γ-CD and 1–TMe-β-CD complexes completely disappeared (Fig. 2a(ii)). Hence, C₆₀–γ-CD and 1–TMe-β-CD were decomposed at 80 °C, in the presence of PEG. The solution after being subjected to heat treatment at 80 °C for 1 h, was dark purple in the absence of any precipitate. The hydrodynamic diameter and ζ-potential of the reacted solution were 125 nm (polydispersity index = 0.21) and −20.2 mV, respectively. Water dispersible fullerene NPs typically exhibit negative ζ-potentials, the origin of which still requires elucidating.^19,20 Hence, the formation of water-dispersible nano-composites, C₆₀–1 NPs, is suggested.Open in a separate windowFig. 2(a) ¹H NMR spectra of mixed solutions comprising fullerene C₆₀–γ-cyclodextrin (CD) and 1–trimethyl (TMe)-β-CD complexes ([C₆₀] = [1] = 0.1 mM) (i) before and (ii) after heating at 80 °C for 1 h, in the presence of polyethylene glycol (PEG) (5 g L⁻¹). Open circles: free γ-CD, filled circles: C₆₀–γ-CD, open diamonds: free TMe-β-CD, and filled diamonds: porphyrin–TMe-β-CD (por–TMe-β-CD) complex. The spectra at 7.6–8.5 ppm, are amplified five-fold. (b) Ultraviolet-visible (UV/Vis) absorption spectra of the mixed solution comprising C₆₀–γ-CD and 1–TMe-β-CD complexes ([C₆₀] = [1] = 0.1 mM) with PEG (5 g L⁻¹), before (dashed line) and after (solid line) heating at 80 °C for 1 h. (c) UV/Vis absorption spectra of the mixed solution comprising the C₆₀–γ-CD complex as a function of the 1–TMe-β-CD complex concentration ([C₆₀] = 0.1 mM, [1] = 0–0.2 mM) with PEG (5 g L⁻¹) after heating at 80 °C for 1 h.The por–TMe-β-CD complexes using 2–6 (Fig. 1), were also prepared adopting the same procedure as that for the 1–TMe-β-CD complex. Each por–TMe-β-CD complex solution was mixed with C₆₀–γ-CD and PEG ([C₆₀] = [por] = 0.1 mM, [PEG] = 5.0 g L⁻¹). The ¹H NMR spectrum of each individual mixed solution after being incubated for 1 h at 80 °C, is shown in Fig. S3.^† In the ¹H NMR spectrum of the mixture comprising C₆₀–γ-CD and 2–TMe-β-CD, the peaks attributed to these complexes at 5.03, 4.98, and 7.60–8.50 ppm, completely disappeared after being subjected to incubation for 1 h at 80 °C, without precipitation (Fig. S3a^†). Similar changes in the ¹H NMR spectrum of the mixture comprising C₆₀–γ-CD and 3–TMe-β-CD complexes are observed, as shown in Fig. S3b.^† The data suggest that the 2–TMe-β-CD and 3–TMe-β-CD complexes can be decomposed in a similar manner as the C₆₀–γ-CD complexes, and imply the formation of C₆₀–2 and C₆₀–3 NPs.The ¹H NMR spectra of the mixed solutions comprising C₆₀–γ-CD and 4, 5, or 6–TMe-β-CD complexes failed to show peaks attributed to the C₆₀–γ-CD complex, and peaks associated with the respective por–TMe-β-CD complexes were observed after incubation for 1 h at 80 °C (Fig. S3c–e,^† respectively). Hence, the data suggest that the C₆₀–γ-CD complex decomposed in the presence of PEG, and the 4, 5, and 6–TMe-β-CD complexes were observed to be stable without decomposition at 80 °C. There have been reports suggesting the strong interaction of water-soluble tetraphenyl porphyrins with TMe-β-CDs.^21,22 Polar substituents prompt the penetration of the polarized porphyrin rims into the TMe-β-CD cavity. Porphyrins 4–6 possess polar substituents, which are suggested to enable the formation of stable TMe-β-CD complexes. Furthermore, the size of the β-CD cavity is sufficiently narrow to prevent any strong interaction with PEG.²³ Thus, PEG-induced decomposition of the 4, 5, and 6–TMe-β-CD complexes is not possible.The absorption behavior of C₆₀–1 NPs was investigated using ultraviolet-visible (UV/Vis) spectroscopy. In the UV/Vis spectra, the characteristic peak of solvated C₆₀–γ-CD, at 333 nm shifted to 344 nm after heating at 80 °C for 1 h (Fig. 2b). An additional broad absorption at 400–550 nm is also apparent, which is characteristic of solid-state crystalline C₆₀ and arises from the electronic interactions between adjacent C₆₀ molecules.^24,25 The characteristic peak of the solvated 1–TMe-β-CD complex at 415 nm, shifted to 432 nm, with induced broadening after being subjected to heat treatment at 80 °C for 1 h (Fig. 2b). In the absence of C₆₀–γ-CD complexes, the characteristic absorption peak attributed to the solvated 1–TMe-β-CD complex completely disappeared after heating for 1 h at 80 °C, in the presence of PEG (Fig. S4^†). The data show that 1, when expelled from the TMe-β-CD cavities, forms non-dispersible precipitates in the absence of C₆₀. For 1 dispelled from the TMe-β-CD cavities to be stably dispersed in water, formation of co-aggregates with C₆₀ may be a prerequisite. C₆₀–2 and C₆₀–3 NPs also show similar UV-Vis absorption spectra after being subjected to heating at 80 °C for 1 h, as shown in Fig. S5a and b,^† respectively.To further elucidate the composite formation of C₆₀ and 1, the influence of 1 concentration on C₆₀–1 NP formation was investigated by UV/Vis spectroscopy (Fig. 2c). The intensity of the absorption peak at 432 nm increased as a function of 1 concentration from 0.05 to 0.1 mM. Conversely, the absorption peak at 345 nm, derived from the formation of fullerene NPs, shifted to 338 nm, with increasing concentration of 1. This absorption peak derives from the fullerene nanoparticle size, and as the size decreased (i.e., the NPs became smaller), the peak blue-shifted.¹¹ The results suggest that in the presence of 1, the fullerene interaction might be disturbed, or smaller C₆₀ NPs might form. For C₆₀–1 NPs formulated with 0.2 mM of 1 ([C₆₀] = 0.1 mM, [1] = 0.2 mM), the absorption peak derived from the Soret band of 1 split into two peaks (Fig. 2c). The absorption peak at the shorter wavelength of 415 nm is consistent with that of the 1–TMe-β-CD complex. The absorption peak at the longer wavelength of 431 nm is almost consistent with the absorption peaks in the UV/Vis spectra of C₆₀–1 NPs fabricated with 0.05 and 0.1 mM of 1. The findings indicate that in the sample comprising 0.2 mM of 1, a portion of the 1–TMe-β-CD complexes remained in the complex state after heating for 1 h at 80 °C, in the presence of PEG. The absorption peak at 338 nm, which reflects the state of fullerene NPs, is similar to that of C₆₀–1 NPs fabricated with 0.1 mM of 1. When C₆₀ and 1 form co-aggregated NPs, the ratio of 1 to C₆₀ is thought to be limited to ∼1 : 1.Morphological observations of the hybrid NPs were also undertaken. In the absence of the por–TMe-β-CD complex, C₆₀ NPs possessing fairly monodisperse size distributions were observed (Fig. S6a^†). The average diameter of the individual NPs, determined from the transmission electron microscopy (TEM) images, is 82 nm. C₆₀ NPs have been previously reported to exhibit lattice fringes and diffraction patterns, which suggests that C₆₀ NPs maintain the face-centered cubic (fcc) crystalline structure.¹¹ C₆₀–1 NPs prepared with 0.05 mM C₆₀ and 0.1 mM 1, possessed irregular shapes (Fig. 3a and b, respectively). The average diameter of C₆₀–1 NPs, determined by TEM, is 119 nm (Fig. 3a and S6b^†), demonstrating the larger C₆₀–1 NP size than that of the C₆₀ NPs (82 nm). Increasing the concentration of 1 to 0.1 mM results in the average diameter of C₆₀–1 NPs to increase to 131 nm (Fig. 3b and S6c^†). Similar morphology is observed from the TEM micrographs of C₆₀–2 and C₆₀–3 NPs having average diameters of 109 nm and 144 nm, respectively (Fig. 3c and d, respectively). A lower PEG molecular weight or a lower reaction temperature during C₆₀ NP formation via C₆₀–γ-CD complexes have been reported to induce an increase in the diameter of the C₆₀ NPs.^11,12 Thus, the findings suggest that slower reaction conditions result in less nucleation and a larger NP formation. Porphyrin 3 possesses a methoxy substituent at the para position of the phenyl group and is more polar than 1 or 2. Previous reports have demonstrated that the higher the polarity of the phenyl group, the more stable the complex with TMe-β-CD,^21,22 which indicates that 3–TMe-β-CD is more stable than 1– or 2–TMe-β-CD in water. Thus, the aforementioned decomposition, which results from the interaction with PEG, is slower in 3 with a concomitant increase in the NP size.Open in a separate windowFig. 3Transmission electron microscopy (TEM) images of C₆₀–1 nanoparticles (NPs) prepared with (a) 0.05 and (b) 0.1 mM of the 1–TMe-β-CD complex. TEM images of (c) C₆₀–2 and (d) C₆₀–3 NPs. Scale bars in images (a–d) are 100 nm. (e) High resolution TEM micrograph and selected-area electron diffraction pattern of C₆₀–1 NP. Scale bar is 10 nm. (f) ¹³C NMR spectra of (i) C₆₀ NPs and (ii) C₆₀–1 NPs. (g) Illustration of a C₆₀–por NP. A portion of C₆₀ form crystalline structures, while a portion of the porphyrin molecules interact with C₆₀ at the molecular level.In the high-resolution TEM micrograph (Fig. 3e), the C₆₀–1 NPs only exhibited partial lattice fringes, and hence did not show clear diffraction patterns compared with the C₆₀ NPs (inset in Fig. 3e).¹¹ The findings demonstrate the highly amorphous nature of the C₆₀–1 NPs, and that the C₆₀ crystal structure was only retained in part. ¹³C NMR spectra also provide important information about the structure of the C₆₀–1 NPs. A characteristic C₆₀ cluster signal at 142.4 ppm was detected in both C₆₀ NPs and C₆₀–1 NPs (Fig. 3f).²⁶ The C₆₀–1 NP dispersions also exhibited several small new signals at 141.5, 143.3, and 143.7 ppm, as shown in Fig. 3f(ii). When a fullerene and a porphyrin molecule form a stable complex in solution, the C₆₀ signal shifts depending on the interaction type between the fullerene and the porphyrin molecule.²⁷ Thus, the porphyrin molecule interacted with the aggregate of C₆₀ in C₆₀–1, as illustrated in Fig. 3g.Some porphyrin molecules can form a co-crystal with fullerene C₆₀.²⁸ To form a crystal structure, not only the interaction between molecules but also the relationship with the solvent, such as gradually changing the polarity of the solvent or removing the solvent, are important. In our system, porphyrin molecules that are pseudo-dissolved by TMe-β-CDs are added to water, which is a poor solvent for porphyrins, through the interaction of PEG with TMe-β-CDs. The porphyrin molecule should immediately aggregate and have difficulty forming a crystal structure. Furthermore, because water is also a poor solvent for fullerene C₆₀, C₆₀ also immediately aggregates in water. Thus, it should be extremely difficult for C₆₀ and porphyrin molecules to regularly associate to form a co-crystal structure.The concentration of singlet oxygen molecules (¹O₂, Type-II energy transfer pathway) generated by photoirradiation was measured according to a chemical method using 9,10-anthracenediyl-bis(methylene) dimalonic acid (ABDA)^15,29 as a marker to determine the biological activities of C₆₀ NPs, C₆₀–1 NPs, C₆₀–2 NPs, and C₆₀–3 NPs. The absorption of ABDA at the absorption maximum (380 nm) was monitored as a function of irradiation time ([C₆₀] = 0.1 mM, [por] = 0 or 0.1 mM). Under visible-light irradiation at wavelengths > 620 nm, C₆₀–1 NPs, C₆₀–2 NPs, and C₆₀–3 NPs generated higher levels of ¹O₂ than C₆₀ (Fig. 4a). These results show that the ¹O₂ photoproduction abilities of the C₆₀–por NPs were higher than that of the C₆₀ NPs. There are no significant differences in the ¹O₂ photoproduction abilities of C₆₀–1 NPs, C₆₀–2 NPs, and C₆₀–3 NPs, which suggests that the structure of the porphyrin has an insignificant influence on the ability of the hybrid NPs. The generation of formazan, via the reduction of nitroblue tetrazolium (NBT) by oxygen radicals (O₂˙⁻), is observed as an increase of absorption intensity at 560 nm.³⁰ The reduction of NBT by O₂˙⁻ was scarcely detected in solutions containing C₆₀–1 NPs, C₆₀–2 NPs, and C₆₀–3 NPs under photoirradiation, even though formazan was readily detected in the positive control sample in the presence of reduced nicotinamide adenine dinucleotide (NADH) (Fig. 4b). The results suggest that the reactive oxygen species produced by C₆₀–1 NPs, C₆₀–2 NPs, and C₆₀–3 NPs are predominantly ¹O₂ generated by a Type-II reaction.¹⁸Open in a separate windowFig. 4(a) ¹O₂ generation by NPs. Bleaching of 9,10-anthracenediyl-bis(methylene) dimalonic acid (ABDA) was monitored as a function of the decrease in the absorbance at 380 nm, for C₆₀ NPs (black circles and solid line), C₆₀–1 NPs (red circles and solid line), C₆₀–2 NPs (blue circles and solid line), and C₆₀–3 NPs (green circles and solid line) ([C₆₀] = 15 μM, [por] = 0 or 15 μM, [ABDA] = 25 μM). (b) O₂˙⁻ generation by NPs. The amount of formazan generated by the reduction of nitroblue tetrazolium (NBT) in the presence of O₂˙⁻ was analyzed by the absorbance at 560 nm, of C₆₀–1 NPs (red circles) and C₆₀–2 NPs (blue circles) in the absence (solid lines) and presence (dashed lines) of NADH ([C₆₀] = 15 μM, [por] = 15 μM, [NBT] = 200 μM, [NADH] = 0 or 625 μM). All samples were photoirradiated at >620 nm, in O₂-saturated aqueous solutions.In summary, the preparation of hybrid C₆₀–porphyrin NPs was achieved via a guest exchange reaction comprising porphyrin CD complexes and C₆₀. Seven C₆₀–por NP derivatives with various moieties were prepared. CD porphyrin complexes possessing phenyl and methoxyphenyl moieties were decomposed in the presence of PEG at the same time as C₆₀–γ-CD complexes and formed NPs with C₆₀. Porphyrins containing a hydrophilic moiety form stable complexes with TMe-β-CD and fail to co-aggregate with C₆₀. The C₆₀–por NPs are negatively charged and are easily dispersed and stable in water. The ¹O₂ generation ability of C₆₀–por NPs under photoirradiation (>620 nm) is greater than that of C₆₀ NPs. The findings herein demonstrate a new method to fabricate fullerene–porphyrin composite materials, which provides a route to highly functional fullerene-based materials.     

Efficient modification of PAMAM G1 dendrimer surface with β-cyclodextrin units by CuAAC: impact on the water solubility and cytotoxicity

The toxicity of the poly(amidoamine) dendrimers (PAMAM) caused by the peripheral amino groups has been a limitation for their use as drug carriers in clinical applications. In this work, we completely modified the periphery of PAMAM dendrimer generation 1 (PAMAM G1) with β-cyclodextrin (β-CD) units through the Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) to obtain the PAMAM G1-β-CD dendrimer with high yield. The PAMAM G1-β-CD was characterized by ¹H- and ¹³C-NMR and mass spectrometry studies. Moreover, the PAMAM G1-β-CD dendrimer showed remarkably higher water solubility than native β-CD. Finally, we studied the toxicity of PAMAM G1-β-CD dendrimer in four different cell lines, human breast cancer cells (MCF-7 and MDA-MB-231), human cervical adenocarcinoma cancer cells (HeLa) and pig kidney epithelial cells (LLC-PK1). The PAMAM G1-β-CD dendrimer did not present any cytotoxicity in cell lines tested which shows the potentiality of this new class of dendrimers.

The toxicity of the poly(amidoamine) dendrimers (PAMAM) caused by the peripheral amino groups has been a limitation for their use as drug carriers in clinical applications.     

Magnetic hyperthermia with ε-Fe2O3 nanoparticles

Biocompatibility restrictions have limited the use of magnetic nanoparticles for magnetic hyperthermia therapy to iron oxides, namely magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃). However, there is yet another magnetic iron oxide phase that has not been considered so far, in spite of its unique magnetic properties: ε-Fe₂O₃. Indeed, whereas Fe₃O₄ and γ-Fe₂O₃ have a relatively low magnetic coercivity, ε-Fe₂O₃ exhibits a giant coercivity. In this report, the heating power of ε-Fe₂O₃ nanoparticles in comparison with γ-Fe₂O₃ nanoparticles of similar size (∼20 nm) was measured in a wide range of field frequencies and amplitudes, in uncoated and polymer-coated samples. It was found that ε-Fe₂O₃ nanoparticles primarily heat in the low-frequency regime (20–100 kHz) in media whose viscosity is similar to that of cell cytoplasm. In contrast, γ-Fe₂O₃ nanoparticles heat more effectively in the high frequency range (400–900 kHz). Cell culture experiments exhibited no toxicity in a wide range of nanoparticle concentrations and a high internalization rate. In conclusion, the performance of ε-Fe₂O₃ nanoparticles is slightly inferior to that of γ-Fe₂O₃ nanoparticles in human magnetic hyperthermia applications. However, these ε-Fe₂O₃ nanoparticles open the way for switchable magnetic heating owing to their distinct response to frequency.

ε-Fe₂O₃ is a magnetic iron(iii) oxide with a giant coercivity. Its potential in hyperthermia applications has been evaluated in comparison with γ-Fe₂O₃ over a wide range of field frequencies and amplitudes.     

Glycosylation of luteolin in hydrophilic organic solvents and structure–antioxidant relationships of luteolin glycosides

An effective approach was developed to biotransform luteolin glycosides in hydrophilic organic solvents. Bacillus cereus A46 cells showed high activity and stability in 5–20% (v/v) DMSO with 90–98% conversion rates of luteolin glycosides. Five glycosides of luteolin 7-O-β-glucoside, luteolin 4′-O-β-glucoside, luteolin 3′-O-β-glucoside, luteolin 7,3′-di-O-β-glucoside and luteolin 7,4′-di-O-β-glucoside were obtained. The addition of DMSO greatly promoted the solubility of luteolin and further regulated the formation of the main products from five luteolin glycosides to luteolin 7-O-β-glucoside (931.2 μM). Fourteen flavonoids and anthraquinones were used as tentative substrates. Glycosylation positions were located at the C-7, C-3′ or C4′ hydroxyl groups of flavonoids and C-5 hydroxyl group of anthraquinones. The 3′,4′-dihydroxy arrangement played the key role for the antioxidant activity of luteolin.

Efficient glycosylation of luteolin in organic solvents and the structure–antioxidant relationships of luteolin glycosides were reported for the first time.     

Nano ferrites (AFe2O4, A = Zn,Co, Mn,Cu) as efficient catalysts for catalytic ozonation of toluene

Nano ferrites (AFe₂O₄, A = Zn, Co, Mn, Cu) were supported on the surface of γ-Al₂O₃ support by hydrothermal synthesis to prepare a series of novel composite catalysts (AFe₂O₄/γ-Al₂O₃) for catalytic ozonation for elimination of high concentration toluene at ambient temperature. The characterization results showed that the high-purity nano-AFe₂O₄ particles were uniformly loaded on mesoporous γ-Al₂O₃. Further, it was confirmed that among the several catalysts prepared, the amount of oxygen vacancies (O_vs), Lewis acid sites (LAS), and Brønsted acid sites (BAS) of the ZnFe₂O₄/γ-Al₂O₃ catalyst were the highest. This meant that the ZnFe₂O₄/γ-Al₂O₃ catalyst had a strong adsorption capacity for toluene and ozone (O₃), and had a strong catalytic activity. When the temperature was 293 K and the space velocity was 1500 h⁻¹, the mol ratio of O₃ to toluene was 6, the degradation rate of toluene (600 mg m⁻³) can reach an optimum of 99.8%. The results of electron paramagnetic resonance (EPR) and Fourier infrared (FT-IR) proved superoxide radicals and hydroxyl radicals by catalytic ozonation. Moreover, the GC-MS analysis results indicated that the toluene degradation began with the oxidation of methyl groups on the benzene ring, eventually producing CO₂ and H₂O. After repeated experiments, the toluene degradation rate remained stable, and the residual content of O₃ in each litre of produced gas was less than 1 mg L⁻¹, thereby indicating that the ZnFe₂O₄/γ-Al₂O₃ catalyst had excellent reusability and showed great potential for the treatment of toluene waste gas.

Nano ferrites (AFe₂O₄, A = Zn, Co, Mn, Cu) were supported on the surface of γ-Al₂O₃ by hydrothermal synthesis to prepare a series of novel catalysts (AFe₂O₄/γ-Al₂O₃) for catalytic ozonation of high concentration toluene at ambient temperature.     

Effects of reaction environments on radical-scavenging mechanisms of ascorbic acid

The effects of reaction environments on the radical-scavenging mechanisms of ascorbic acid (AscH₂) were investigated using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^•) as a reactivity model of reactive oxygen species. Water-insoluble DPPH^• was solubilized by β-cyclodextrin (β-CD) in water. The DPPH^•-scavenging rate of AscH₂ in methanol (MeOH) was much slower than that in phosphate buffer (0.05 M, pH 7.0). An organic soluble 5,6-isopropylidene-l-ascorbic acid (iAscH₂) scavenged DPPH^• much slower in acetonitrile (MeCN) than in MeOH. In MeOH, Mg(ClO₄)₂ significantly decelerated the DPPH^•-scavenging reaction by AscH₂ and iAscH₂, while no effect of Mg(ClO₄)₂ was observed in MeCN. On the other hand, Mg(ClO₄)₂ significantly accelerated the reaction between AscH₂ and β-CD-solubilized DPPH^• (DPPH^•/β-CD) in phosphate buffer (0.05 M, pH 6.5), although the addition of 0.05 M Mg(ClO₄)₂ to the AscH₂–DPPH^•/β-CD system in phosphate buffer (0.05 M, pH 7.0) resulted in the change in pH of the phosphate buffer to be 6.5. Thus, the DPPH^•-scavenging reaction by iAscH₂ in MeCN may proceed via a one-step hydrogen-atom transfer, while an electron-transfer pathway is involved in the reaction between AscH₂ and DPPH^•/β-CD in phosphate buffer solution. These results demonstrate that the DPPH^•-scavenging mechanism of AscH₂ are affected by the reaction environments.     

Graphene tailored by Fe3O4 nanoparticles: low-adhesive and durable superhydrophobic coatings

This study reports stable superhydrophobic Fe₃O₄/graphene hybrid coatings prepared by spin coating of the Fe₃O₄/graphene/PDMS mixed solution on titanium substrates. By tailoring graphene sheets with Fe₃O₄ nanoparticles, the superhydrophobicity of graphene platelets was largely enhanced with a water contact angle of 164° and sliding angle <2°. Fe₃O₄ nanoparticles interact with FLG sheets via Fe–O–C covalent link, to form a graphene micro-sheet pinned strongly by nano-sized Fe₃O₄. The newly-formed micro/nano-structured sheets interact with each other via strong dipole–dipole attractions among Fe₃O₄ nanoparticles, confirmed by the blue shifts of G band observed in Raman spectra. The strongly interactive micro/nano-structured sheets are responsible for the improvement of both the surface hydrophobicity and the durability towards water impacting. The obtained hybrid coatings possess excellent durability in various environments, such as acidic and basic aqueous solutions, simulating ocean water. And also the coatings can retain their stable superhydrophobicity in Cassie–Baxter state even after annealing at 250 °C or refrigerating at −39 °C for 10 h. We employed an AFM to probe nanoscale adhesion forces to examine further the ability of the as-prepared coatings to resist the initial formation of water layers which reflects the ability to prevent the water spreading. The most superhydrophobic and durable hybrid coating with 1.8 g Fe₃O₄, shows the smallest adhesion force, as expected, indicating this surface possesses the weakest initial water adhesive strength. The resulting low-adhesive superhydrophobic coating shows a good self-cleaning ability. This fabrication of low-adhesive and durable superhydrophobic Fe₃O₄/FLG hybrid coatings advances a better understanding of the physics of wetting and yield a prospective candidate for various practical applications, such as self-cleaning, microfluidic devices, etc.

Strongly interactive graphene micro-sheets tailored by Fe₃O₄ nanoparticles exhibit low-adhesive and durable superhydrophobicity.     

The effect of oxidant species on direct,non-syngas conversion of methane to methanol over an FePO4 catalyst material

The effect of the phase transformation of a FePO₄ catalyst material from the tridymite-like (tdm) FePO₄ to the α-domain (α-Fe₃(P₂O₇)₂) during the direct selective oxidation of methane to methanol was studied using oxidant species O₂, H₂O and N₂O. The main reaction products were CH₃OH, carbon dioxide and carbon monoxide, whereas formaldehyde was produced in rather minute amounts. Results showed that the single-step non-syngas activation of CH₄ to oxygenate(s) on a solid FePO₄ phase-specific catalyst was influenced by the nature of the oxidizer used for the CH₄ turnover. Fresh and activated FePO₄ powder samples and their modified physicochemical surface and bulk properties, which affected the conversion and selectivity in the partial oxidation (POX) mechanism of CH₄, were investigated. Temperature-programmed re-oxidation (TPRO) profiles indicated that the type of moieties utilised in the procedures, determined the re-oxidizing pathway of the reduced multiphase FePO₄ system. Mössbauer spectroscopy measurements along with X-ray diffraction (XRD) examination of neat, hydrogenated and spent catalytic compounds, demonstrated a variation of the phosphate into a mixture of crystallites, which depended on operating process conditions (for example time-on-stream). The Mössbauer spectra revealed the change of the initial ferric orthophosphate, FePO₄ (tdm), to the divalent metal form, iron(ii) pyrophosphate (Fe₂P₂O₇); thereafter, reactivity was governed by the interaction (strength) with individual oxidizing agents. The Fe³⁺ ↔ Fe²⁺ chemical redox cycle can play a key mechanistic role in tailored multistep design, while the advantage of iron-based heterogeneous catalysis primarily lies in being inexpensive and comprising non-critical raw resources. When compared to the other catalysts reported in the literature, the FePO₄-tdm phase catalysts showed in this work exhibited a high activity towards methanol i.e., 12.3 × 10⁻³ μmol_MeOH g_cat h⁻¹ using N₂O as an oxidant. This catalyst also showed a high activity with O₂ as an oxidant (5.3 × 10⁻³ μmol_MeOH g_cat h⁻¹). Further investigations will include continuous reactor unit engineering optimisation.

The effect of the phase transformation of a FePO₄ catalyst material from the tridymite-like (tdm) FePO₄ to the α-domain (α-Fe₃(P₂O₇)₂) during the direct selective oxidation of methane to methanol was studied using oxidant species O₂, H₂O and N₂O.     

In vitro and in silico studies of SARS-CoV-2 main protease Mpro inhibitors isolated from Helichrysum bracteatum

Discovering SARS-CoV-2 inhibitors from natural sources is still a target that has captured the interest of many researchers. In this study, the compounds (1–18) present in the methanolic extract of Helichrysum bracteatum were isolated, identified, and their in vitro inhibitory activities against SARS-CoV-2 main protease (M^pro) was evaluated using fluorescence resonance energy transfer assay (FRET-based assay). Based on 1D and 2D spectroscopic techniques, compounds (1–18) were identified as 24-β-ethyl-cholesta-5(6),22(23),25(26)-triene-3-ol (1), α-amyrin (2), linoleic acid (3), 24-β-ethyl-cholesta-5(6),22(23),25(26)-triene-3-O-β-d-glucoside (4), 1,3-propanediol-2-amino-1-(3′,4′-methylenedioxyphenyl) (5), (−)-(7R,8R,8′R)-acuminatolide (6), (+)-piperitol (7), 5,7,4′-trihydroxy-8,3′-dimethoxy flavanone (8), 5,7,4′-trihydroxy-6-methoxy flavanone (9), 4′,5-dihydroxy-3′,7,8-trimethoxyflavone (10), 5,7-dihydroxy-3′,4′,5′,8-tetramethoxy flavone (11), 1,3-propanediol-2-amino-1-(4′-hydroxy-3′-methoxyphenyl) (12), 3′,5′,5,7-tetrahydroxy-6-methoxyflavanone (13), simplexoside (piperitol-O-β-d-glucoside) (14), pinoresinol monomethyl ether-β-d-glucoside (15), orientin (16), luteolin-3′-O-β-d-glucoside (17), and 3,5-dicaffeoylquinic acid (18). Compounds 6, 12, and 14 showed comparable inhibitory activities against SARS-CoV-2 M^pro with IC₅₀ values of 0.917 ± 0.05, 0.476 ± 0.02, and 0.610 ± 0.03 μM, respectively, compared with the control lopinavir with an IC₅₀ value of 0.225 ± 0.01 μM. The other tested compounds showed considerable inhibitory activities. The molecular docking study for the tested compounds was carried out to correlate their binding modes and affinities for the SARS-CoV-2 M^pro enzyme with the in vitro results. Analyzing the results of the in vitro assay together with the obtained in silico results led to the conclusion that phenylpropanoids, lignans, and flavonoids could be considered suitable drug leads for developing anti-COVID-19 therapeutics. Moreover, the phenylpropanoid skeleton oxygenated at C3, C4 of the phenyl moiety and at C1, C3 of the propane parts constitute an essential core of the SARS-CoV-2 M^pro inhibitors, and thus could be proposed as a scaffold for the design of new anti-COVID-19 drugs.

Compounds isolated and identified from Helichrysum bracteatum leaves showed promising in vitro inhibitory activities against SARS-CoV-2 main protease (M^pro). Thus, could be considered suitable drug leads for developing anti-COVID-19 therapeutics.     

Fluorinated β-diketonate complexes M(tfac)2(TMEDA) (M = Fe,Ni, Cu,Zn) as precursors for the MOCVD growth of metal and metal oxide thin films

Partially fluorinated β-diketonate complexes M(tfac)₂(TMEDA) (M = Fe 1, Ni 2, Cu 3, Zn 4; tfac = 1,1,1-trifluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine) were synthesized and structurally (sc-XRD) and thermochemically (TGA) characterised. A new polymorph of Fe(tfac)₂(TMEDA) was found. The structural and physicochemical properties of 1–4 were compared with related M(acac)₂(TMEDA) and M(hfac)₂(TMEDA) (acac = 2,4-pentanedionate, hfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate) β-diketonate complexes to evaluate the effect of the degree of fluorination. A positive effect on the thermal behaviour of the metal acetylacetonates was observed, but no discernible trends. Application of complexes 1–4 as precursors in a MOCVD process yielded either metal (Ni, Cu) or metal oxide thin films (Fe₃O₄, ZnO), which were further oxidized to NiO, CuO and α-Fe₂O₃ films by calcination in air at 500 °C.

Novel trifluoroacetylacetonate complexes M(tfac)₂·TMEDA (M = Fe, Ni, Cu, Zn) were used as precursors for the MOCVD growth of metal and metal oxide thin films.     

Linear α-olefin production with Na-promoted Fe–Zn catalysts via Fischer–Tropsch synthesis

The production of linear alpha-olefins (α-olefins) is a practical way to increase the economic potential of the Fischer–Tropsch synthesis (FTS) because of their importance as chemical intermediates. Our study aimed to optimize Na-promoted Fe₁Zn_1.2O_x catalysts such that they selectively converted syngas to linear α-olefins via FTS at 340 °C and 2.0 MPa. The Fe₁Zn_1.2O_x catalysts were calcined at different temperatures from 350 to 700 °C before Na anchoring. The increase in the size of the ZnFe₂O₄ crystals comprising the catalyst had a negative effect on the reducibility of Fe oxides and the particle size of Fe₅C₂ during the reaction. The Na species in the catalyst restrained the reduction of Fe₁Zn_1.2O_x but facilitated the formation of Fe₅C₂. When pure Fe₁Zn_1.2O_x was calcined at 400 °C, the corresponding catalyst (i.e., Na_0.2/Fe₁Zn_1.2O_x (400)) exhibited higher catalytic activity and stability than the other catalysts for a 50 h reaction. Compared to the other catalysts, Na_0.2/Fe₁Zn_1.2O_x (400) enabled a higher number of active Fe carbides (Fe₅C₂) to intimately interact with the Na species, even though the catalyst had a lower total surface basicity based on surface area. The Na_0.2/Fe₁Zn_1.2O_x (400) showed a maximum hydrocarbon yield of 49.7% with a maximum olefin selectivity of 61.3% in the C1–C32 range. Examination of the reaction product mixture revealed that the Na_0.2/Fe₁Zn_1.2O_x catalysts converted α-olefins to branched paraffins (13.9–19.5%) via a series of isomerization, skeletal isomerization, and hydrogenation reactions. The Na_0.2/Fe₁Zn_1.2O_x (400) catalyst had a relatively low consumption rate of internal olefins compared to other catalysts, resulting in the lowest selectivity for branched paraffins. The Na_0.2/Fe₁Zn_1.2O_x (400) showed a maximum α-olefin yield (26.6%) in the range C2–C32, which was 27.9–50.0% higher than that of other catalysts. The α-olefin selectivity in the C5–C12 range for the Na_0.2/Fe₁Zn_1.2O_x (400) was 37.5% relative to the total α-olefins.

Intimate contact between Fe₅C₂ and Na₂O leads to high linear olefin selectivity with minimizing branched paraffin formation.     

Antiproliferative activity of new pentacyclic triterpene and a saponin from Gladiolus segetum Ker-Gawl corms supported by molecular docking study

A new triterpenoidal saponin identified as 3-O-[β-d-glucopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 4)-β-d-xylopyranosyl]-2β,3β,16α-trihydroxyolean-12-en-23,28-dioic acid-28-O-α-l-rhamnopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 2)-α-l-arabinopyranoside 1 together with a new oleanane triterpene identified as 2β,3β,13α,22α-tetrahydroxy olean-23,28-dioic acid 2 and 6 known compounds (3–8) have been isolated from Gladiolus segetum Ker-Gawl corms. The structural elucidation of the isolated compounds was confirmed using different chemical and spectroscopic methods, including 1D and 2D NMR experiments as well as HR-ESI-MS. Moreover, the in vitro cytotoxic activity of the fractions and that of the isolated compounds 1–8 were investigated against five human cancer cell lines (PC-3, A-549, HePG-2, MCF-7 and HCT-116) using doxorubicin as a reference drug. The results showed that the saponin fraction exhibited potent in vitro cytotoxic activity against the five human cancer cell lines, whereas the maximum activity was exhibited against the PC-3 and A-549 cell lines with the IC₅₀ values of 1.13 and 1.98 μg mL⁻¹, respectively. In addition, compound 1 exhibited potent activity against A-549 and PC-3 with the IC₅₀ values of 2.41 μg mL⁻¹ and 3.45 μg mL⁻¹, respectively. Interestingly, compound 2 showed the maximum activity against PC-3 with an IC₅₀ of 2.01 μg mL⁻¹. These biological results were in harmony with that of the molecular modeling study, which showed that the cytotoxic activity of compound 2 might occur through the inhibition of the HER-2 enzyme.

A new triterpenoidal saponin 1, a new oleanane triterpene 2, and 6 known compounds (3–8) have been isolated from Gladiolus segetum Ker-Gawl corms.