Self‐assembled dandelion‐like hydroxyapatite (HAp) nanostructures were successfully synthesized via a mild template‐free hydrothermal process, using ethylenediaminetetraacetic acid (EDTA) as the surfactant. The obtained dandelion‐like HAp nanostructures were between 5 and 8 μm in diameter and were composed of radially oriented nanorods with an average diameter of about 200 nm. The X‐ray diffraction analysis and Fourier transform infrared spectroscopy were used to characterize the crystalline phase and purity of the synthesized nanostructures. The Brunauer–Emmett–Teller surface area of the dandelion‐like nanostructures was measured to be about 39 m2/g. The results of thermal analysis revealed that dandelion‐like HAp nanostructures have appropriate thermal stability up to 1200°C. Scanning electron microscopy and transmission electron microscopy analyses showed that EDTA plays an important role in obtaining the dandelion‐like morphology, because without it, only monodispersed HAp nanoparticles with an average diameter of about 125 nm were formed. The mechanism for the formation of dandelion‐like HAp nanostructures was suggested based on the radial self‐assembly of Ca‐EDTA molecular complexes.
Heterocyclic motif is an important scaffold which has both industrial and pharmaceutical applications. These motifs can be prepared using wide variety of reaction conditions such as the use of expensive catalyst, toxic solvent, harsh reaction condition like the use of base, high temperature, and multistep reaction. Although various methods are involved, the chemistry arena is now shifted towards the greener way of synthesis. Nanocatalyst constitutes an important role in the green synthesis. This is because the activity of the catalyst resides in the exposed portion of the particles. By decreasing the size of the catalyst, advantages such as more surface area would be exposed to the reactant, only negligible amount would be required to give the significant result and selectivity could be achieved, thereby, eliminating the undesired products. The current review enlists the various types of nanocatalyst involved in the heterocyclic ring formation and also some other important functionalization over the ring.
Monodispersed single‐crystal hydroxyapatite (HAp) nanorods with nearly uniform diameters and lengths of, respectively, about 25 and 100 nm were rapidly synthesized using a template‐free and convenient microwave irradiation method. Precipitation of HAp occurred directly in a calcium‐phosphate precursor solution containing ethylenediaminetetraacetic acid (EDTA) as a capping agent and using microwave irradiation of 900 W power and 2.45 GHz frequency as the heating source. Transmission electron microscopy observations revealed that faceted surfaces and narrow‐size distribution were two interesting features of the HAp nanorods obtained. The selected area electron diffraction pattern of the nanorods obtained clearly confirmed their single crystalline nature and the growth along the basal (001) planes. Furthermore, the formation mechanism of HAp nanorods was clearly proposed, identifying the influences of EDTA and microwaves in the growth process.
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