Laser-Assisted Synthesis of Colloidal Ni Nanoparticles: Structural and Morphological Analysis

We report on the synthesis of Ni/NiO nanoparticles (NPs) using pulsed laser ablation in liquid (PLAL) technique in deionized water (DI). The laser-generated Ni/NiO NPs in DI show a bimodal size distribution. The structural and morphological analysis using microscopic technique reveal the formation of core-shell structure together with the formation of three distinct features of Ni/NiO nanostructures in DI, nanosheet, hollow and chain-like structures. The formation of a nanosheet-like structure in the colloidal NP solution is attributed to the deformation of the cavitation bubble (CB) and the presence of high pressure at the interface between the bubble and the target during the collapse of CB. The observation of hollow NPs is attributed to the Kirkendall effect and nanochain-like structures due to the post-irradiation effect and laser melting during PLAL. The selected area electron diffraction (SAED) pattern analysis reveals the presence of both Ni and NiO phases indicating the synthesized NPs are polycrystalline. Based on the experimental results, the possible growth mechanisms for the formation of different structures and morphology of Ni NP in DI during PLAL are discussed.