Ophiorrhiza mungos-Mediated Silver Nanoparticles as Effective and Reusable Adsorbents for the Removal of Methylene Blue from Water.

Green synthesis of silver nanoparticles (AgNPs) using a plant extract has attracted significant attention in recent years. It is found as an alternative for other physicochemical approaches because of its simplicity, low cost, and eco-friendly rapid steps. In the present study, Ophiorrhiza mungos (Om)-mediated AgNPs have been shown to be effective bioadsorbents for methylene blue (MB) dye removal (88.1 ± 1.74%) just after 1 h at room temperature in the dark from an aqueous medium for the first time. Langmuir and Freundlich isotherms fit the experimental results having the correlation coefficient constants R2 = 0.9956 and R2 = 0.9838, respectively. From the Langmuir fittings, the maximum adsorption capacity and adsorption intensity were found to be 80.451 mg/g and 0.041, respectively, indicating the excellent performance and spontaneity of the process. Taking both models under consideration, interestingly, our findings indicated a fairly cooperative multilayer adsorption that might have been governed by chemisorption and physisorption, whereas the adsorption kinetics followed the pseudo-second-order kinetics mechanism. The positive and low values of enthalpy (ΔH0 = 4.91 kJ/mol) confirmed that adsorption is endothermic and physical in nature; however, the negative free energy and positive entropy value (ΔS0 = 53.69 J/mol K) suggested that the adsorption is spontaneous. The biosynthesized adsorbent was successfully reused up to the fifth cycle. A proposed reaction mechanism for the adsorption process of MB dye onto Om-AgNPs is suggested. The present study may offer a novel finding such as an effective and sustainable approach for the removal of MB dye from water using biosynthesized Om-AgNPs as reusable adsorbents at a comparatively faster rate at a low dose for industrial applications.

Facile preparation of a lightweight multifunctional interlayer for high-performance Li-S batteries.

The construction of functional interlayers for separator modification in Li-S batteries has been proven to be a feasible and effective strategy to alleviate the shuttle effect. However, several challenging issues in interlayer design and fabrication, including the tedious material preparation process and high weight loading of the interlayer on the pristine separator, jeopardize the battery energy density. In this work, a nitrogen-abundant nanoporous carbon/graphene (NC/G) composite was synthesized by a facile method and fabricated into a lightweight membrane, which was investigated as a multifunctional interlayer in a Li-S battery. The abundant nitrogen sites and nanoporous structure of NC/G can effectively anchor and trap polysulfides; graphene (G) can create an excellent conductive network in NC/G. These attributes of NC/G are able to efficiently boost the sulfur redox reaction kinetics and significantly suppress the shuttle effect, leading to superb battery performance. More importantly, the low density of NC/G was conducive to reducing the load on the separator, thus reducing the decline in battery energy density, which is promising for practical applications. Even at an ultra-low loading of NC/G on the pristine separator (0.08 mg cm-2), the battery showed a competitive electrochemical performance compared with many reported materials. We believe this work provides a strategic guidance for the future fabrication of promising functional interlayers for practical Li-S battery applications.

Size controlled biosynthesis of silver nanoparticles using Ophiorrhiza mungos, Ophiorrhiza harrisiana and Ophiorrhiza rugosa aqueous leaf extract and their antimicrobial activity.

In this work, the aqueous leaf extracts of three Ophiorrhiza genus species, namely Ophiorrhiza mungos (Om), Ophiorrhiza harrisiana (Oh) and Ophiorrhiza rugosa (Or), have been used as the reducing and capping agents to control the size of AgNPs, Om-AgNPs, Oh-AgNPs and Or-AgNPs, respectively and found to be an effective antimicrobial agent against a wide range of bacteria and fungi. The biosynthesized AgNPs were studied by UV-Visible spectrophotometer, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray, transmission electron microscopy (TEM) and Fourier transform infrared spectrometer (FTIR). The average particle sizes of Om-AgNPs, Oh-AgNPs and Or-AgNPs were measured as 17 nm, 22 nm and 26 nm, respectively, and observed to be spherical and face-centered cubic crystals. The antibacterial test of synthesized AgNPs was performed against Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Vibrio cholerae where the maximum antibacterial activity was observed by reducing the nano-size and increasing the silver content of AgNPs. The antifungal effect of these three types of AgNPs on Penicillium notatum and Aspergillus niger was also evaluated and their growth with AgNPs concentrations of 450 µg/mL was inhibited up to 80-90% and 55-70%, respectively. The size-control synthesis of AgNPs using the Ophiorrhiza genus species is presented here for the first time where the synthesized AgNPs showed higher stability and antimicrobial activities. Therefore, this study might lead to synthesize AgNPs with different morphologies using plant extracts of the same genus but from different species and provide strong encouragement for future applications in treating infectious diseases.

Aqueous Nd3+ capture using a carboxyl-functionalized porous carbon derived from ZIF-8.

A porous graphitic carbon was obtained via the pyrolysis of a zeolite imidazolate framework (ZIF-8) under Ar atmosphere. Then, the carbon was functionalized with carboxylic groups and applied for separation of neodymium ions (Nd3+) from water. The adsorbent (denoted as C-ZDC) was characterized by X-ray diffraction, N2 adsorption-desorption isotherms, infrared spectroscopy, X-ray photoelectron spectroscopy, scanning and transition electron microscopies, thermogravimetric analysis, and Boehm titration. A practical adsorption equilibrium was attained within 4 h, and the adsorption isotherm at 25 °C revealed a maximum adsorption capacity of 175 mg/g, which is one of the highest values reported for different kinds of adsorbents. The adsorption kinetics and equilibrium isotherms were modeled, and the selectivity for Nd3+ over other metal ions was examined. From the effect of solution pH on the adsorption and material characterization results before and after adsorption, the high adsorption capacity of C-ZDC was ascribed to the formation of coordination bonds between Nd3+ ions and the -COOH groups. Further, the material was reusable for at least four adsorption-desorption cycles after a simple step of acid washing.

Palladium Nanoparticles Supported on MIL-101 as a Recyclable Catalyst in Water-Mediated Heck Reaction.

Pd nanoparticles supported on the chromium terephthalate metal organic framework, Pd0.9/MIL-101, was prepared by simple Pd-acetate adsorption on MIL-101 followed by reduction in acetone. The material was characterized by XRD, N2 adsorption-desorption isotherm, TEM and ICP analysis. Pd0.9/MIL-101 was found to be an effective heterogeneous catalyst for the water-mediated Heck cross-coupling reaction of various aryl iodides and alkenes under mild reaction conditions with product yields of 81 to 97%. The electron-withdrawing group attached to aryl iodide reacted faster than the electron-donating one, and the activity increased in the sequence of 4-methoxy-1- iodobenzene << iodobenzene < 1-iodo-4-nitrobenzene. The catalyst could be reused several times without losing its initial catalytic activity, and XRD and TEM confirmed that the crystallinity of Pd0.9/MIL-101 had been retained during the reaction with no metal leaching or agglomeration observed.

Pd nanoparticles supported on MIL-101: an efficient recyclable catalyst in oxidation and hydrogenation reactions.

Pd nanoparticles supported on the chromium terephthalate metal organic framework MIL-101 (Pd/MIL-101) in different loadings (0.9 and 4.5 wt%) have been successfully prepared through a simple Pd-acetate adsorption and reduction in acetone, and tested as catalyst for selected liquid phase oxidation and hydrogenation reactions. The materials were characterized by XRD, N2 adsorption--desorption isotherm, TEM, SEM-EDX and ICP analysis. The parent MIL-101 structure was found well preserved after formation of Pd nanoparticles and after catalytic reaction runs. The present catalyst afforded good activity and selectivity for the oxidation of benzyl alcohol to benzaldehyde with 85% conversion and 97% selectivity using air (1 atm) at 85 degrees C after 14 h. The catalyst also showed good activity in the hydrogenation of the C=C bond in alkenes to corresponding alkanes and also benzaldehyde to benzyl alcohol at room temperature using H2 (1 atm). Rigorous test results confirmed that Pd-nanoparticles supported on MIL-101 are responsible for the catalytic reactions occurred. Pd/MIL-101 was reusable several times without losing the structural integrity and initial activity, and demonstrated significantly higher catalytic activities than those by a commercial Pd catalyst supported on activated carbon.

A new heterogeneous catalyst for epoxidation of alkenes via one-step post-functionalization of IRMOF-3 with a manganese(II) acetylacetonate complex.

A manganese(II) acetylacetonate complex has been immobilized to the metal-organic framework IRMOF-3 through a one-step post-synthetic route for the first time, providing an effective and recyclable heterogeneous catalyst for epoxidation of alkenes.

Solvothermal synthesis of Fe-MOF-74 and its catalytic properties in phenol hydroxylation.

A Fe-containing metal-organic framework, Fe-MOF-74, was solvothermally synthesized using FeCl2.4H2O and 2,5-di-hydroxy-1,4-benzenedicarboxylic acid. Characterization was conducted by XRD, BET surface area measurement, FT-IR spectroscopy, TGA, and elemental analysis, which confirmed successful preparation of Fe-MOF-74 having an identical framework structure to that reported for MOF-74. Fe-MOF-74 was found to be an effective heterogeneous catalyst for the hydroxylation of phenol using H2O2 as an oxidant; 60% phenol conversion was achieved at 20 degrees C in water with 68 and 32% selectivity to catechol and hydroquinone, respectively. The effect of temperature, phenol/H2O2 mole ratio, catalyst quantity, and solvent on catalytic performance was discussed, and a reaction mechanism is proposed based upon the experimental results.

Selective oxidation of tetralin over a chromium terephthalate metal organic framework, MIL-101.

MIL-101, a mesoporous chromium terephthalate metal organic framework, was found to be an efficient heterogeneous catalyst for selective oxidation of tetralin to 1-tetralone using tert-butyl hydroperoxide or acylperoxy radicals generated in situ from trimethylacetaldehyde and O(2) as an oxidant.

Synthesis and characterization of novel chiral sulfonato-salen-manganese(III) complex in a zinc-aluminium LDH host.

A novel heterogeneous catalyst, [Zn(2.15)Al(0.86)(OH)(6.02)][Mn](0.19)[C(6)H(5)COO](0.48.2H(2)O, where [[Mn]= chiral sulfonato(-)salen-manganese(iii) complex, Na(2)MnC(20)H(22)N(2)S(2)O(12)Cl, intercalated into Zn(II)-Al(III) layered double hydroxide host], has been synthesized and found to be an effective heterogeneous catalyst for the stereoselective epoxidation of R-(+)-limonene using molecular oxygen. The catalyst could be recycled without loss of performance.