Development of a concentration cell-based method for nanoparticle characterization

This study introduces an innovative particle measurement device utilizing a concentration cell, which comprises two half-cells separated by a track-etched polycarbonate membrane with 100 nm pores, two copper electrodes, CuSO₄ solutions of varying concentrations, and a multimeter interfaced with a computer. The incorporation of SiO₂ nanoparticle colloids into the low-concentration half-cell led to pore obstruction by the nanoparticles, resulting in a reduction in the membrane potential, which correlated with the SiO₂ particle concentration. The detection limit for the particle concentration, derived from this correlation, decreased as the SiO₂ particle size increased. Given that the particle concentration can be converted to the particle content in the colloid solution by weight, it was determined that the particle size could be estimated using a calibration curve of the particle content and particle size at the detection limit. Additionally, the introduction of positively charged SiO₂ particles enhanced the surface charge of the membrane, causing a gradual increase in the membrane potential beyond the baseline, following an initial decline. This observation suggests a potential method for determining the charge polarity of particles with unknown surface charges. This study demonstrates the viability of employing a concentration cell as a straightforward and cost-effective method for particle measurement, with the capability to ascertain the particle size and surface charge.