Preparation and characterization of Ni nanoparticles with tunable size and controllable structure in room temperature ionic liquid

Three kinds of Ni nanoparticles were synthesized in two kinds of room temperature ionic liquid, 1-butyl-3-methyl limidizaolium tetrafluoroborate ([BMIm] [BF₄]) and 1-hexyl-3-methyl limidizaolium tetrafluoroborate ([HMIm][BF₄]), respectively, via thermolysis of nickel formate at 250 °C. The structures of the Ni nanoparticles were characterized by means of Fourier transform infrared spectrometry, X-ray diffraction and transmission electron microscopy. The XRD results indicate that the nanoparticles synthesized in [BMIm][BF₄] have cubic structure or hexagonal structure synthesized in [HMIm][BF₄]. The TEM results indicate that the nanoparticles have different diameter under different concentration at the same thermolysis temperature. So, by adjusting the concentration of the nickel formate, the Ni nanoparticle size can be expediently controlled. The FT-IR results indicate that the surface of the Ni nanoparticles was modified with the room temperature ionic liquid. So it is concluded that Ni nanoparticles with tunable size and controllable structure can be expediently prepared in room temperature ionic liquid. The proposed formation mechanism of the Ni nanoparticles was also discussed.