Nanosprings and the Electric Double Layer

Abstract

The electric double layer (EDL) is a very important aspect in surface science. Small objects on the surface around which the EDL has formed can change the composition of the EDL. This change can be used to detect small objects. We have prepared a setup in which we can use this technique to visualise a nanosping, which then can be used to determine the mobility of a particle. The setup consisted of a potentiodynamic optical contrast microscope and conductive sampleslides. The samples we created are PEG linkers adhered to an ITO surface, to act as the nanosprings, with gold nanoparticles on top. To give advice on specific parameters to use in the experiments, we created a simulation in python. In the simulation, a nanoparticle is subject to spring, drag and electric forces as well as Brownian motion. In the electric field, some influences of the electric double layer were introduced in the form of the so-called Debye Hückel approximation. Upon analysing the simulation data my advise on carrying out the experiment as described in part I is to use a timestep between dt = 10􀀀5 and dt = 10􀀀3 s. For the simulation, my advice would be to use Nt = 105. For optimal results, the length nanospring should around 25 nm, with an applied potential of around 0.07 V.