Nanoparticles for nucleation of heavy metal iodide films: Mercuric iodide and bismuth tri-iodide cases

Mercuric iodide and bismuth tri-iodide nanoparticles were synthesized by suspension in octadecene, from Hg(NO₃)₂. H₂O and I₂, and from Bi(NO₃)₃. 5H₂O and I₂, respectively. The best synthesis conditions were 2 hrs. at 60-70 ^oC, followed by 10 min. at 95-110 ^oC for mercuric iodide nanoparticles, and 4 hrs. at 80-110 ^oC, followed by 10 min. at 180-210 ^oC for bismuth tri-iodide ones. Nanoparticles were then washed and centrifugated with ether repeatedly. Compounds identity was confirmed by X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). Nanoparticles were characterized by transmission (TEM) and scanning (SEM) electron microscopy. Disk-like and squared mercuric iodide nanostructures were obtained, 80-140 nm and 100-125 nm in size respectively. Rounded and rod-like bismuth tri-iodide nanoparticles, 30-500 nm in size were obtained. Acetonitrile and isopropanol suspensions of mercuric iodide nanoparticles, and acetonitrile suspension of bismuth tri-iodide nanoparticles exhibited peak maxima shifts in their UV-Vis spectra, as was reported for nanoparticles of other materials. It is the first time that mercuric iodide and bismuth tri-iodide nanoparticles are synthesized by the suspension method, although uniform shape and size distributions have not yet been obtained. They offer interesting perspectives for crystalline film nucleation, for improving current applications of these materials, as far as for opening new ones.