Optical Properties and Colloidal Stability Mechanism of Bismuth Nanoparticles Prepared by Q-Switched Nd:Yag Laser Ablation in Liquid

Bismuth is semimetal with unique properties such as magnetoresistance and thermoelectric behaviors due to high electron mobility, low carrier density and highly anisotropic Fermi surface. In addition, bismuth NPs undergoes a semimetal to semiconductor transition due to size induced quantum confinement effect. Therefore, bismuth NPs are potentially useful for optical and electro optical devices. In addition, bismuth NPs are interesting as green lubricant and thermoelectric materials. Recently, laser ablation is extensively employed to synthesis of metal NPs by laser target interaction in liquid environment. The aim of this work is the synthesis of stable bismuth colloidal NPs by Q-switched laser ablation in acetone. A Q-switched Nd:YAG laser with the fundamental wavelength at 1064 nm,energy of 118 mJ/pulse and 12 ns pulse duration was employed for bismuth target ablation. The laser was operated for 5 min at repetition rate of 10 Hz. Colloidal stability, particle size, crystal structure and optical properties of the NPs were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy respectively. The bismuth NPs were rather spherical and with the particle size of 27 9 nm. The XRD pattern of NPs was consistent with a bismuth rhombohedral crystal structure. Colloidal bismuth NPs in acetone is in light brown color. UV-Visible spectra were measured in 6 months shows perfect stability of colloidal samples without any precipitation. Optical extinction without plasmon resonance pick in visible wavelengths is the optical characteristic of bismuth NPs and reveal perfect dispersion of NPs without agglomeration or coupling of NPs in liquid. According to the FT-IR result as the stability of NPs is related to the large dipole moment of acetone molecule and acetone enolate formation on the surface of bismuth NPs.