Synthesis and characterization of nickel selenide nanoparticles: size and shape determining parameters

Nickel selenide nanoparticles of different sizes and shapes were synthesized using a modified solvothermal method. The effects of the reaction time, pH and solvent on the properties of nickel selenide were also explored. The particles synthesized in 1 h yielded mono-dispersed spheres with a Ni0.95Se phase, whilst the particles synthesized in 3 h resulted in a mixture of spherical and fused cylindrical nanoparticles with a single Ni0.95Se phase. Further increments of time (6 and 24 h) resulted in mixtures of particle sizes and shapes and both the samples displayed a Ni3Se4 phase. The pH had effected very little changes on the properties of the nanoparticles though at highly acidic pH the particles evolved from spherical shaped Ni0.95Se to cubic shaped Ni3Se4. The effect of the solvent was also investigated. The water synthesis resulted in mono-dispersed nanospheres with a Ni0.95Se crystal phase whilst the ethylenediamine synthesized particles resulted in very small particles engulfed in an ethylenediamine layer with a Ni6Se5 crystal phase. The particles synthesized in pyridine on the other hand resulted in poly-dispersed Ni5Se5 nanoparticles with spherical and cubic morphologies.