Synthesis of BiOI nanoparticles toward potential contrast applications

Abstract

The use of heavy metal-containing nanoparticles as potential X-ray contrast agents for the medical imaging of the human body, predates the advent of iodinated compounds because of their high X-ray attenuation power. Among the investigated heavy metals for contrast agents, Bi is the heaviest stable nonradiative metal element with a very high X-ray attenuation coefficient. There have been very few attempts to make hydrolytically stable CT (Computerized Tomography) active nanoparticles; Bismuth tends to form chalcogens among which Bi2S3 has been investigated to be used for a prospective CT contrasting agent. The said synthesis has given ultra-small nanoparticles, but they are hydrolytically unstable giving off a foul smelled toxic gas H2S over time. However, the colloidal solution of BiOI NPs withstands mild acidic conditions, whereas the Bi2S3 is not stable in acidic condition. In this preliminary study, a unique decelerated hydrolytic procedure was developed for synthesizing biocompatible and ultrasmall PVP(polyvinylpyrrolidone) coated BiOI nanoparticles which are having a nearly spherical structure with an average size of ~2.7 nm. The phase purity and crystal structure of these prepared materials was determined by X-ray powder diffraction using bulk materials. The synthesized compound has a layered structure and is hydrolytically stable at neutral pH. Hence, the prepared BiOI nanoparticles can be an ideal material for potential CT contrast agents.