Synergism in CdSe/MMT photocatalyst induces efficient synthesis of 2-substituted benzazoles under visible light with excellent yields and recycling capability.
The
present work describes the improved photocatalytic activity
of cetyl trimethylammonium bromide (CTAB)-assisted Bi2WO6 (CBTH) toward the synthesis of bioactive benzazoles. X-ray
diffraction analysis of CBTH suggests that crystal growth has occurred
along the (200) plane, whereas field-emission scanning electron microscopy
images confirm two-dimensional rose bud morphology and high-resolution
transmission electron microscopy analysis suggests the formation of
thin nanosheets possessing an orthorhombic structure. Temperature-programmed
desorption of ammonia and Py-IR measurements indicate substantial
acidity with the generation of Brønsted acid sites on the surface
of CBTH. Raman spectra of CBTH also corroborate these observations
with the formation of defects within [Bi2O2]2+ layers, resulting in decreased thickness and shapes of nanoplates.
These beneficial properties are explored toward the photochemical
synthesis of benzazoles using a 35 W tungsten lamp and a CBTH photocatalyst,
resulting in better yields at lesser exposure time. It is observed
that the catalytic activity is retained up to five consecutive cycles
with marginal decrease in % yield. Such a feature can be ascribed
to the photostability of the photocatalyst even after continuous exposure
to light, implying that the surface active sites remained unaltered
as evident from the X-ray photoelectron spectroscopy analysis of pre-
and post-characterization of CBTH. Moreover, decrease in the surface
hydroxyl groups after five catalytic cycles also accounts for the
generation of enhanced Brønsted sites owing to the presence of
Bi–O on the surface of CBTH. It exhibits better catalytic activity
as compared to other photocatalysts employed for the synthesis of
benzazoles. Thus, CBTH serves as a robust photocatalyst for the facile
synthesis of these heterocycles in a sustainable manner.
Many invasive weeds are known to create their deleterious effects on biological ecosystems and also rhizosphere soils. Weeds such as Cosmos and Xanthium have their existence near agricultural crops fields. Such weeds grow in abundance, releasing specific allelochemicals which have adverse effect on germination rate, physiological patterns and reproduction of crop plants. In present work, allelopathic effects of leaf leachates of Cosmos and Xanthium were observed on seed germination and seedling growth of Triticum aestivum, Vigna radiata and Trigonella foenum-graceum like crops. Seed germination was inhibited at higher concentration at 6% while lower concentrations showed stimulatory effect on Mungbean and Fenugreek from 1%-4% concentrations. But seed germination percentage of Vigna and Trigonella showed 70% and 60% growth in response to leaf leachates of Cosmos at 6% concentration. Triticum showed total inhibition of 40% to both leaf leachates. The qualitative phytochemical analyses showed presence of alkaloids, phytosterols, phenols, tannins and flavonoids. GCMS and IR studies revealed presence of major constituents such as esters, ethers, anhydride and polyalcohols. Cosmos and Xanthium showed the characteristic FTIR fingerprinting regions of various functional groups such as –OH, carbonyl, anhydride, ester and amides. The variations in phytochemicals of these invasive might be attributed to response of the plants to different environmental stresses.
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