Formation mechanisms, structural and optical properties of Bi/Bi2O3 One dimensional nanostructures prepared via oriented aggregation of bismuth based nanoparticles synthesized by DC arc discharge in water

Bismuth based rod-like nanostructures were prepared via oriented attachment of colloidal bismuth based nanoparticles synthesized by direct current (DC) arc discharge in liquid. For the synthesis of bismuth based nanoparticles 5 A and 20 A DC electrical currents were applied between two pure bismuth electrodes in water. Bismuth based nanoparticles extracted from the water after 30 days then dispersed in ethanol. Bismuth based rod-like nanostructures formed via the oriented attachment mechanism in ethanol during 30 days. According to X-ray diffraction (XRD) patterns of as-prepared samples, the main parts of the particles were bismuth phase while after 30 days bismuth oxide and bismuth hydroxide phases were dominant. To investigate the species that formed in plasma during the electrical discharge in water, optical emission spectroscopy (OES) was used. The OES spectra demonstrate the creation of Bi-I, Bi-II, O-I, O-II and H ions and H-2-I molecules for both currents. UV-visible spectroscopy and field emission scanning electron microscopy (FE-SEM) were used for the study of optical properties, morphology and size distribution of the nanostructures respectively. Optical transmission spectra of synthesized nanostructures in water indicated the optical characteristic of both bismuth and bismuth oxide. FE-SEM images illustrate that bismuth based nanoparticles are rather spherical as-prepared and formed rod-like nanostructures by passing the time in the presence of ethanol. Also, the size of nanoparticles and subsequently diameter of rod-like nanostructures for samples that prepared by 5 A arc current is more than samples that prepared by 20 A. The results provide a simple and flexible method for synthesis of bismuth based rod-like nanostructures.