No abstract

No abstract

Valorization of oilseed processing wastes is thwarted due to the presence of several antinutritional factors such as phenolics, tannins, glucosinolates, allyl isothiocyanates, and phytates; moreover, literature reporting on their simultaneous extraction and subsequent practical application is scanty. Different solvent mixtures containing acetone or methanol pure or combined with water or an acid (hydrochloric, acetic, perchloric, trichloroacetic, phosphoric) were tested for their efficiency for extraction of these antinutritive compounds from rapeseed press-cake. Acidified extraction mixtures (nonaqueous) were found to be superior to the nonacidified ones. The characteristic differences in the efficacy of these wide varieties of solvents were studied by principal component analysis, on the basis of which the mixture 0.2% perchloric acid in methanol/acetone (1:1 v/v) was deemed as "the best" for detoxification of rapeseed meal. Despite its high reductive potential, hemolytic activity of the extract from this solvent mixture clearly indicated the toxicity of the above-mentioned compounds on mammalian erythrocytes. Because of the presence of a high amount of antinutritive antioxidants, the study was further extended to examine the influence of this solvent extract on the stability of waste cooking oil-derived biodiesel. Treatment with the extract harbored significant improvement (p < 0.05) in the induction periods and pronounced reduction in microbial load of stored biodiesel investigated herein. Thus, a suitable solvent system was devised for removing the major antinutrients from rapeseed press-cake, and the solvent extract can, thereafter, be used as an effective exogenous antioxidant for biodiesel. In other words, integrated valorization of two different industrial wastes was successfully achieved.

The presence of lanthanide-tellurite “anti-glass” nanocrystalline phases not only affects the transparency in glass–ceramics (GCs) but also influences the emission of a dopant ion. Therefore, a methodical understanding of the crystal growth mechanism and local site symmetry of doped luminescent ions when embedded into the precipitated “anti-glass” phase is crucial, which unfolds the practical applications of GCs. Here, we examined the Ln2Te6O15 “anti-glass” nanocrystalline phase growth mechanism and local site symmetry of Eu3+ ions in transparent GCs produced from 80TeO2–10TiO2–(5 – x)­La2O3–5Gd2O3–xEu2O3 glasses, where x = 0, 1, 2. A crystallization kinetics study identifies a unique crystal growth mechanism via a constrained nucleation rate. The extent of “anti-glass” phase precipitation and its growth in GCs with respect to heat-treatment duration is demonstrated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis. Qualitative analysis of XRD confirms the precipitation of both La2Te6O15 and Gd2Te6O15 nanocrystalline phases. Rietveld refinement of powder X-ray diffraction patterns reveals that Eu3+ ions occupy “Gd” sites in Gd2Te6O15 over “La” sites in La2Te6O15. Raman spectroscopy reveals the conversion of TeO3 units to TeO4 units with Eu2O3 addition. This confirms the polymerizing role of Eu2O3 and consequently high crystallization tenacity with increasing Eu2O3 concentration. The measured Eu3+ ion photoluminescence spectra revealed its local site symmetry. Moreover, the present GCs showed adequate thermal cycling stability (∼50% at 423 K) with the highest activation energy of around 0.3 eV and further suggested that the present transparent GCs would be a potential candidate for the fabrication of red-light-emitting diodes (LEDs) or red component phosphor in W-LEDs.

No abstract

No abstract

Conspectus The pursuit for the discovery of new and powerful synthetic methods to access high-value N-heterocycles has been at the forefront of organic chemistry research for more than a century. Considering the importance of N-scaffolds in modern science, over the past few decades, great research efforts have been made to develop efficient synthetic methods for the construction of nitrogen-rich molecules. Among many efforts, transition metal catalyzed denitrogenative annulation reaction has emerged as a cornerstone due to its innate versatility and wider scope of application. The denitrogenative annulation approach offers clear advantages over many existing methods, as it enables effective, single-step interconversion of easily available feedstocks into a variety of other important N-containing heterocyclic frameworks. Recently, transition metal catalyzed denitrogenative annulation reaction of the 1,2,3-triazole via a metal carbene intermediate sparked significant interest in the application of various important heterocycle syntheses. Denitrogenative annulation reaction of 1,2,3-triazoles proceeds via an ionic mechanism. Recently, we demonstrated a new concept for the denitrogenative reaction of triazoles with alkenes and alkynes via in situ generated 2-(diazomethyl)­pyridines. The method takes advantage of the inherent properties of a Co­(III)–carbene radical intermediate and is the first report of the denitrogenative annulation/cyclopropanation by a radical-activation mechanism. On the other hand, in contrast to the denitrogenative annulation of 1,2,3-triazole, annulation reaction of 1,2,3,4-tetrazole (a surrogate of azide having an important pyridyl unit) via metal nitrene remains a big challenge. Previously, flash vacuum pyrolysis studies had been used for nitrene–nitrene rearrangement of 1,2,3,4-tetrazole at high temperature. This Account summarizes our recent efforts in developing transition metal catalyzed denitrogenative annulation of 1,2,3-triazoles via a radical mechanism and 1,2,3,4-tetrazoles via metal nitrene to access important nitrogen-rich molecules. We demonstrated that the 1,2,3,4-tetrazole under Ir-catalyzed reaction conditions can produce a productive Ir–nitrene intermediate that can successfully be employed for the construction of a wide number of α-carbolines and 7-azaindoles. Moreover, we developed an iron-based unique strategy for the intermolecular denitrogenative annulation reaction between tetrazoles and alkynes. The reaction overcomes the traditional click reaction and proceeds via an unprecedented metalloradical activation mechanism. Furthermore, we used our understanding of tetrazole reactivity to design an iron-catalyzed intramolecular denitrogenative C­(sp3)-H amination reaction of primary, secondary, and tertiary centers by using a metalloradical activation concept. At the same time, we also developed a general catalytic method to enable two distinct reactions (1,3-cycloaddition and denitrogenative annulation) using Mn­(TPP)Cl that afforded two different classes of nitrogen heter...

A series of Dy3+–Eu3+‐codoped ZrO2 nanocrystals with tetragonal and cubic symmetry was synthesized via a wet chemical reaction. When the Eu3+‐doping content was fixed, the crystal structure could be stabilized from the mixed phase to single cubic phase by simply adjusting the content of Dy3+. The cubic ZrO2:Dy3+–Eu3+ nanoparticles exhibited spherical and nonagglomerated morphology. The effective phonon energy of cubic ZrO2:5%Dy3+–5%Eu3+ was calculated to be 445 cm−1, which is lower than the previously reported results. Extensive luminescence studies of ZrO2:Dy3+–Eu3+ as a function of Dy3+ content demonstrated that the dopant concentration and its site symmetry play an important role in the emissive properties. Under 352 nm excitation, the increment of Dy3+ concentration in ZrO2:Dy3+–Eu3+ led to an increase in orange (590 nm) and red (610 nm) emissions of Eu3+ ions, which are attributed to the 5D0→7FJ(J = 1, 2) transitions of Eu3+ ions. This increment is possibly due to the efficient energy transfer (ET) 4F9/2:Dy3+→5D0:Eu3+. The phosphors can generates light from yellow through near white and eventually to warm white by properly tuning the concentration of Dy3+ ions through the ET and change in site symmetry. These phosphors may be promising as warm‐white‐/yellow‐emitting phosphors.