Study on the signal analysis of single Pd NP Collision on Carbon fiber, Cu, Au and Pt Ultramicroelectrodes

Abstract

Recently, an electrochemical method for the detection a nanoparticle’s (NP’s) collision at the surface of an ultramicroelectrode (UME) was studied by the Bard group and others. (Bard et al. 2010, Compton et al. 2017) The observation of a unique NP collision through the electrocatalytic amplification (ECA) method is made possible by the right combination of a NP, an inert electrode, and an electrocatalytic reaction. Pd NP is one of the most widely used as an electrocatalyst owing to its versatile electrocatalytic activity. Various materials such as carbon fiber, (Daryanavard, Zare 2017) Au, (Park, Kim et al. 2018) and Ni (Oja, Wood et al. 2013) have experimentally served as the inert electrodes for the detection of single Pd NPs collisions. The response type of the transient current by the single NP collision is affected various factors including the material of the UME. The transient current of a NP, which collided and stayed on the electrode surface, manifested a staircase response. On the contrary, a blip (spike) response resulted when the collided NP bumped out of the UME surface or underwent side reactions. Therefore, various factors such as the reaction rate, and applied potential, also can affect the types of current response of a single NP collision. The material of UME is a key element that determines the type of current response

vi in a single NP collision event. The observation of multiple types of current responses at different UMEs is probably caused by the different interaction mechanisms between the NP and the UMEs. The shape of transient current implied that the electrocatalytic ability of the NP did not change consistently or diminished. The continuous electrocatalytic reaction should be the reason why we observed a staircase response. Meanwhile, the blip response indicates the deactivation of the NPs for some various facts, such as the metal alloying between the NP and the UME or facts related to the adsorption impurity. Therefore, the reciprocal interaction between the NP and UMEs or between the NP and the chemicals such as impurities or reaction products is a key element in the determination of the current response of a single NP collision. The electrode material does not only affect the current response; it can affect the collision frequency as well. The reason to this possibility is the fact that there is an interdependency between the collision frequency and the adsorption coefficient of the NP on the UME. In this study, carbon fiber (C), copper (Cu), nickel (Ni), gold (Au), and platinum (Pt) were introduced as a new electrode material for the electrocatalytic activity study of a single Pd NP collision on various material. The current responses of the single Pd NP collision on the various electrode was investigated. The transient current by the Pd NP collision changed from staircase to blip response depending on the material and applied potential of UME. Also, an analysis and comparison of the frequencies and peak heights of the transient currents was carried out, indicating that they were significantly different from each kind of UME.