Optical and structural characterization of nickel selenide nanoparticles synthesized by simple methods

A series of nickel selenide (NiSe₂, NiSe and Ni₃Se₄) nanoparticles have been synthesized by three different methods, i.e. the single-source precursor (method 1), the thermolysis of trioctylphosphine selenide (TOPSe) and nickel chloride in hexadecylamine (method 2) as well as the reaction of nickel chloride and selenium using sodium borohydride as a reducing agent in methanol and in water (method 3). The optical properties of nickel selenide synthesized from all the methods showed good nanometric characteristics with an observed blue-shift in absorption band-edge from bulk nickel selenide. The structural characteristics varied with the methods employed, with method 1 producing 10 nm spherical NiSe₂ particles, method 2 star-shaped NiSe particles, while method 3 produced hexagonal NiSe nanoparticles in methanol and rod-shaped Ni₃Se₄ particles in water.