Practical considerations on detectability of electrically active nanoparticles in environmental samples

Environmental impact of nanotechnologies is among the most important global concerns because these technologies have introduced a completely new class of artificial pollutants with very diverse biological effects. Detection and characterization of nanoparticles in environmental samples requires highly sensitive methods and laboratory equipment. Recently introduced chronoamperometry of single nanoparticles has a potential to measure parameters of nanoparticles of different kinds, including organic and inorganic substances, metals and their oxides. This paper reports practical considerations on factors limiting the level of detection (LOD) for the chronoamperometry of single nanoparticles, successfully used to characterize electrically active nanoparticles. The influence of two major sources of electrical current noise on LOD was studied. It was shown that electrochemical noise dominates over the noise of electronic components. The LOD for a typical laboratory potentiostat was calculated. The overall background current noise (root mean square value) for a typical ultra-low input current potentiostat is between 10 − 13 – 10 − 12 A, that allows detecting silver nanoparticles with radius of 10 – 15 nm, LOD for nanoparticles of -Fe 2 O 3 is 60-80 nm. The theoretical limit of minimum detectable size of nanoparticle is at least 10 times lower, but to achieve this limit very complicated technical issues should be resolved.