Nanoparticle Shape and Size Characterization with Solid State Nanopores

Abstract

Typically Solid state nanopores are used to study bio molecules like DNA and proteins using the principle of Resistive Pulse technique. In this work, we report on using well characterized nano particles of different size, surface charge, and shape to probing the geometry and surface properties of solid-state nanopores. Comparing the stable shape of the nano particles to relatively unstable protein molecules, this study will help us understand and characterize the translocation dynamics of nano particles as well as protein and DNA molecules. We present the translocation behavior of negatively charged polystyrene nano particles that are electrophoretically driven through 40-70nm solid state nanopores. The translocation of these particles produces current blockage events and analyzing these events in terms of blockage amplitude and duration allows us to estimate particle size, shape, electrophoretic mobility and zeta potential of the nanoparticles. All these parameters are studied as a function of electrolyte concentration, pH of the electrolyte and applied voltage. The solid state nanopores are fabricated using a combination of focus ion beam and low energy ion beam in silicon nitride membranes. HRTEM is used to measure the 3D geometry of the nanopores and a Finite element analysis method (COMSOL) is used to simulate the experimental results.