  Nanoparticles (NPs) are widely used in diverse application areas, such as
medicine, engineering, and cosmetics. The size (or volume) of NPs is one of the
most important parameters for their successful application. It is relatively
straightforward to determine the volume of regular NPs such as spheres and
cubes from a one-dimensional or two-dimensional measurement. However, due to
the three-dimensional nature of NPs, it is challenging to determine the proper
physical size of many types of regularly and irregularly-shaped NPs (IS-NPs) at
high-throughput using a single tool. Here, we present a relatively simple
method that statistically determines a better volume estimate of many types of
NPs by combining measurements from their top-down projection areas and
peak-heights using two tools. The proposed method is significantly faster and
more economical than the electron tomography method. We demonstrate the
improved accuracy of the combined method over scanning electron microscopy
(SEM) and atomic force microscopy (AFM) by using both modeling and
measurements. This study also shows that SEM provides a more accurate estimate
of size than AFM for most IS-NP size measurements. The method provides a much
needed, proper high-throughput volumetric measurement method useful for many
applications.
