This work presented controllable growth of ZnO nanostructures with different aspect ratios by the microwave irradiation method and investigated the photocatalytic degradation of methyl red (MR). X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) measurements showed that all ZnO nanostructures were of a hexagonal phase structure. It was revealed by field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images that the morphology of ZnO can be effectively controlled as sheetlike, rod-like, brush-like, flower-like, prism-like, and pyramid-like only by changing the molar ratio (zinc acetate: KOH) and reaction time. With the increase of molar ratio and reaction time, modification in the E 2 (high) and E 1 (LO) Raman modes was observed. The energy band gap was found to be tuned by the aspect ratio of ZnO nanostructures. Photoluminescence spectroscopy revealed the low-intensity NBE emission and high and broad defect-related emission for high aspect ratio ( 14) nanorods. BET surface area porosity analysis confirmed the presence of a mesoporous network in all the nanostructures, showed high surface area and a uniform pore-size distribution for high aspect ratio nanorods. A terephthalic acid assay study confirmed the formation of hydroxyl radicals (OH) in MR dye solution treated with a ZnO nanostructures photocatalyst. The photodegradation of MR under UV light irradiation showed that ZnO nanorods with a high aspect ratio of $14 showed superior photodegradation ($98% degradation of MR within 60 min) than that of the lower aspect ratio nanostructures. The apparent reaction rate constant for high aspect ratio (14) nanorods was higher than that of the lower aspect ratio nanostructures. The enhancement in photocatalytic performance could be due to the high surface area and enhanced charge separation and transfer efficiency of photoinduced charge carriers in the high aspect ratio nanorods.
Nanocellulose (NC) from cellulosic biomass has recently gained attention owing to their biodegradable nature, low density, high mechanical properties, economic value and renewability. They still suffer, however, some drawbacks. The challenges are the exploration of raw materials, scaling, recovery of chemicals utilized for the production or functionalization and most important is toxic behavior that hinders them from implementing in medical/pharmaceutical field. This review emphasizes the structural behavior of cellulosic biomass and biological barriers for enzyme interactions, which are pertinent to understand the enzymatic hydrolysis of cellulose for the production of NCs. Additionally, the enzymatic catalysis for the modification of solid and NC is discussed. The utility of various classes of enzymes for introducing desired functional groups on the surface of NC has been further examined. Thereafter, a green mechanistic approach is applied for understanding at molecular level.
We report studies on the magnetocaloric effect of samarium doped lanthanum manganites with different Sm-concentrations. Polycrystalline La0.7-x
Sm
x
Ca0.30MnO3 (0≤x≤0.3) samples were prepared using the conventional solid-state reaction method with phase purity and structure confirmed using X-ray diffraction. Temperature dependent magnetization measurements and Arrott analysis reveal first order ferromagnetic transition in parent sample and second order ferromagnetic transition in doped sample with Curie temperature decreasing progressively with increasing Sm concentration from ∼182 K for x = 0.05 to 109 K for x = 0.30. A large magnetic entropy change (∼1.75 J kg-1 K-1 at 0.5 T) has been observed in La0.7Ca0.3MnO3 sample, and is greatly suppressed as a function of disorder caused by Sm doping. This is ascribed to the gradual loss of first-order ferromagnetic transition. This investigation suggests that La0.7-x
Sm
x
Ca0.30MnO3 compounds can be used as a potential magnetic refrigerating material with wide range of temperature.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.