Size Characterization of Ultrasmall Silver Nanoparticles Using MALDI-TOF Mass Spectrometry

摘要

Ultrasmall nanoparticles have recently been the subject of a plethora of research owing to the unique physical and chemical properties manifest in the particles as their size approaches a molecular dispersion.Among the ultrasmall nanoparticles, ultrasmall silver nanoparticles were actively researched because of their unique optical and magnetic properties. Although silver is diamagnetic in the bulk state, ultrasmall silver nanoparticles were found to be ferromagnetic. When the size of silver nanoparticles reduces to only a few nanometers, the electronic energy levels become quantized, and the particles emit luminescence. This luminescence has been used as an in vitro optical imaging probe. The magnetic and optical properties of ultrasmall silver nanoparticles are highly size-dependent and are derived from the surface of the particle. As particles become smaller in size, the total surface area increases while the core size decreases such that small enough particles may have no core atoms at all. Considering this, the ability to control the functional properties of these particles requires first being able to control the size of the particle during synthesis, and second being able to accurately measure the size distribution. With regard to the latter, microscopic techniques such as transmission electron microscopy (TEM) are the standard for measuring the size of nanoparticles. However, these