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In this letter, we report an important issue in nanoparticle synthesis by the “bottom up” approach. By controlling the pH of the starting mixture of the salts we have been successful in obtaining the desired conductivity of nanosized nickel ferrite. X-ray diffraction and transmission electron microscopy confirmed the size, structure, and morphology of the nanoferrites. All the materials are typical semiconducting oxides whose conductivity depends on the pH of the starting salt solution. Direct current and alternating current conductivity studies coupled with thermoelectric measurements and the resultant activation energies help us to propose the mechanism of conductivity in these ferrites. X-ray photoelectron spectroscopy studies are indicative of Ni3+ presence in p-type ferrite. The n- and p-type conductivity in these materials is attributed to the hopping due to the presence of Fe3+ and Ni3+ ions, respectively.

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In the present investigation, crab shells as seafood wastes were successfully recycled into an extremely useful biomaterial by the thermal treatment method. Thermogravimetric-differential thermal analysis studies concluded that the calcination temperature must be beyond ∼570 °C to get a fine and crystalline apatite powder from the crab shells. Thus, the calcination temperature is taken to be 700 °C. Powder X-ray diffraction analysis of the calcined crab shells revealed hydroxyapatite (HAp)/carbonated HAp (CHAp) with an average crystallite size of 24.4 nm. Scanning electron microscopy revealed the surface morphology of the crab shells-derived apatite powder as needle-like nanorods of HAp of diameter ≈ 100–300 nm and nanospheres of CHAp of diameter ≈ 100–500. Energy-dispersive X-ray spectroscopy showed the presence of calcium, phosphorous, magnesium, and oxygen as major elements in the apatite constituents. Fourier transform infrared as well as Raman spectroscopies confirmed the formation of apatite powder. X-ray photoelectron spectroscopy results indicated the electronic environment and oxidation states of the constituent elements, Ca, C, and P. On the basis of the results obtained from various characterization techniques, the overall study emphasized an environment-friendly and cost-effective approach for recycling of the bio-pollutant and synthesis of ultra-fine, ultra-crystalline apatite-based excellent biomaterial derived from crab shells as seafood wastes with its application as a futuristic biomaterial in bone/teeth implants.

Asparagusroot-like and scattered needle-like formation of hydroxyapatite nanoparticles under microwave irradiation.