Characterization of Trigonella foenum-graecum Derived Iron Nanoparticles and Its Potential Pesticidal Activity Against Tuta absoluta (Lepidoptera)

Journal of Cluster Science - Indiscriminate use of synthetic chemicals for pest management in agriculture leads to resistance development by the pests in addition to being toxic to non target...     

A polymer-anchored cobalt(II) complex as a reusable catalyst for oxidation of benzene,ethylbenzene and cyclohexane

A polymer-supported cobalt complex of 2,6-bis(benzimidazolyl)pyridine (BBP) was synthesized by immobilization of BBP on chloromethylated polystyrene cross-linked with 6.5 % divinylbenzene, followed by complexation with CoCl₂ in methanol, and characterized by physico-chemical and spectroscopic methods. The polymer-bound Co(PS–BBP)Cl₂ was found to be more stable compared to free Co(BBP)Cl₂ as determined by TGA analyses. The catalytic activity of Co(PS–BBP)Cl₂ was investigated towards oxidation of benzene, ethylbenzene and cyclohexane using tert-butylhydroperoxide as oxidant. At optimum conditions, benzene showed 72.6 % conversion with 100 % selectivity towards phenol; ethylbenzene exhibited 97.0 % conversion with 82.5 and 17.4 % selectivity towards benzaldehyde and acetophenone, respectively, whilst conversion of cyclohexane was 60.0 with 75.8 and 24.1 % selectivity towards cyclohexanol and cyclohexanone. The unsupported complex Co(BBP)Cl₂ showed lower activities and selectivities compared to the polymer-supported complex. Co(PS–BBP)Cl₂ was found to be very active and reusable, giving high yields of the desired products. A possible reaction mechanism is proposed for these oxidation reactions.     

Aggregation of a C60-didodecyloxybenzene dyad: structure, dynamics, and mechanism of vesicle growth

The mechanism of formation and the stability of spontaneously formed vesicles upon self-assembly of a partially ground-state charge-separated, nonpolar-polar-nonpolar fullerene(C60)-didodecyloxybenzene (DDB) dyad in binary solvent mixtures requiring a critical dielectric constant of approximately 30 are reported. Molecular interactions giving rise to defined vesicles with in-plane bilayer packing are detailed from the predominant van der Waals and electrostatic interactions existing on the dyad's framework. The vesicles are formed with a large bending rigidity of 18kBT, which on further extraction into a polar water medium resulted in uniform spheres that corroborated well with the theoretical predictions. Furthermore, the water-extracted spherical dyad aggregates at an increased dyad concentration, leading to the formation of giant micrometer-sized fractals following diffusion-limited cluster aggregation. These dyad aggregates act as efficient quenchers of fluorescent dyes with a quenching rate of 4.6 x 10(13) M(-1) s(-1).     

Effect of side chain and backbone length on lamellar spacing in polystyrene‐block‐poly(dimethyl siloxane) brush block copolymers

We report the synthesis of polystyrene‐block‐poly(dimethyl siloxane) (PS‐b‐PDMS) brush block copolymers (BBCPs) through sequential ROMP of norbornene‐modified macromonomers (‐NB) and explore the effect of side chain length (N_sc) and total backbone degree of polymerization (N_bb) on the self‐assembly of lamellar morphologies. Group I (PS‐NB M_n = 2.9 kg/mol, PDMS‐NB M_n = 4.8 kg/mol) exhibits asymmetric side chains, while Group II (PS‐NB M_n = 4.7 kg/mol, PDMS‐NB M_n = 4.8 kg/mol) possess a more symmetric arrangement. Both families rapidly self‐assemble into well‐ordered lamellar morphologies with domain spacings (d₀) ranging from d₀ = 54 to 140 nm. The scaling relationship between d₀ and N_bb (d₀ ~N_bb^α) was determined as the measure of backbone flexibility. Exponents of α = 0.71 and α = 0.81 are observed for Groups I and II, respectively, indicating the BBCPs adopt an extended backbone conformation. The presence of a low T_g side chain such as PDMS increases apparent flexibility of the backbone. The interplay between contrasting characteristics of the side chains is discussed and reveals the importance of understanding the physical consequences of block architecture on controlling BBCP assembly. These findings provide necessary information for future investigations of complex phases and well‐defined nanostructures fabricated using the brush architecture. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 691–699     

Liquid-to-solid transitions in nanoparticle-filled brush block copolymer composites

The natural self-assembly of densely grafted brush block copolymers (BBCP) is used to direct functional nanoparticles (NP) into well-ordered structures with large lattice spacings and high NP content. Understanding the NP's impact on the phase behavior and viscoelastic properties is necessary for optimizing the processing windows for such materials. Thermo-structural and thermo-rheological properties are investigated in a model nanocomposite system composed of a di-block bottlebrush (dbBB) poly(tert-butyl acrylate)-block-poly(ethylene oxide) (PtBA-b-PEO), complexed with surface functionalized zirconium oxide (ZrO₂) NPs. The NPs selectively sequester into the microphase separated PEO domains through coordinated hydrogen bonding. Loading up to φ = 30 wt% NP is achieved, and the lamellar morphologies are stable in the melt state according to temperature controlled small angle X-ray scattering (SAXS). Systematic transitions in the linear viscoelasticity, determined by small amplitude oscillatory shear (SAOS) suggest that at slow timescales, the NP superstructure inhibits the highly mobile relaxation processes inherent to the dbBB architecture. Further analysis of the relaxation time spectrum H(τ) is used to describe the constraint of such relaxation mechanisms. The structure–property relationships realized by SAOS and SAXS enable future manipulation of mechanical properties and processing of BBCP/NP composites for both established and emergent applications.     

Analyzing the Synergistic Effects of Antioxidants in Combating Photoaging Using Model Nematode,Caenorhabditis elegans

Aging, a universal and unique process, occurs both intrinsically (chronological) and extrinsically (photoaging). Ultraviolet-A (UV-A)-mediated stress is a growing health hazard to mankind as it is the major cause of photoaging, which could lead to much damage of skin cells and tissues ranging from tan, burn, or even cancer. The present study focuses on the role of antioxidants and other natural compounds which have been widely used in oral/topical applications to combat and delay the effects of photoaging using model nematode Caenorhabditis elegans. Compounds like green tea extract, naringenin, and naringin, which are known for their antioxidant properties, were able to extend life span and healthspan of the nematode in normal as well as under UV-A-mediated stress conditions. Regulation of both the stress-responsive genes (skn-1 and sir-2.1) and the aging-regulating genes (daf-2 and age-1) was attributable for these conditions. Interestingly, it was observed that these compounds when combined in equal ratios by weight worked synergistically to combat the aging process. Pronounced synergistic effects were observed during UV-A-mediated stress conditions, suggesting that these could be used as potential antiphotoaging compounds which will be of greater significance for health-based research.     

Determination of uranium in process stream solutions from uranium extraction plant employing energy dispersive X-ray fluorescence spectrometry

Energy dispersive X-Ray fluorescence (EDXRFS) method is developed and standardized for the determination of uranium on routine basis in various process stream solutions, covering a vide range of concentrations from 0.1 to 400?g?L^?1, from an Uranium Extraction Plant at Nuclear Fuel Complex. The method has been applied to aqueous stream samples. Except for dilution, no much sample preparation was involved in the analysis and accordingly the experimental parameters were optimized. The calibration curve in the range of 0.1?C10?g?L^?1 of U was drawn manually using synthetic standard solutions prepared from U₃O₈ powder and L?? (13.61?keV) line of uranium was used for the measurements. The results from EDXRFS method are compared with other methods and are found to be in good agreement. The EDXRFS measurements carried over a range of 0.1?C350?g?L^?1 of uranium have shown a RSD of ±1?C5%. Also, the limitations of reported methods in literature and the advantages of present method are highlighted in the paper.     

Hydrogenation of substituted nitroarenes by a polymer-bound palladium(II) Schiff base catalyst

The catalytic activity of a polymer-bound palladium Schiff base catalyst was investigated toward the reduction of aryl nitro compounds under ambient temperature and pressure. The dependence of the rate of hydrogenation of o-nitroaniline and o-nitrotoluene on substrate concentration, catalyst concentration and temperature has been determined. Based on the results obtained a plausible mechanism for the hydrogenation reaction is proposed and a rate expression is deduced. The energy and entropy of activation have been evaluated from the kinetic data. The polymer-bound catalyst was found to be better than its homogeneous analog PdCl₂(NSBA) [NSBA = N-salicylidene benzylamine] for both stability and reusability. Recycling studies revealed that the catalyst could be used six times without metal leaching or significant loss in activity.     

Optical,spectral and thermal properties of organic nonlinear optical single crystal: 2,3-Dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate

The potential organic nonlinear optical single crystal of 2,3-dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate has been grown by slow evaporation solution growth technique (SEST) using ethanol–water solution at room temperature. The powder X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non-centrosymmetric space group P2₁2₁2₁ and the cell parameters are a = 7.61 Å, b = 10.73 Å, c = 29.49 Å, V = 2410.75 Å³. The functional groups of the synthesized compound have been identified by FT-Raman and FTIR analyses. Photoluminescence spectroscopy study is determined to explore its efficacy towards device fabrications. Birefringence measurement has been carried out in order to analyze the optical homogeneity of the grown crystal. The optical constants such as reflectance (R) and extinction coefficient (K) have been determined from the transmittance data. The relative second harmonic efficiency of the compound is found to be 4 times greater than that of KDP. DTA-DSC measurements indicate that the crystal is thermally stable up to 174 °C.