Measuring\nthe Effects of Tunable Alkanethiol Monolayers\non the Adsorption and Collision Dynamics of Platinum Nanoparticles

Platinum nanoparticles (PtNPs) catalyze the Hydrogen\nEvolution\nReaction upon colliding at a catalytically inactive electrode surface\nwhen sufficient potential is applied and in the presence of adequate\nhydrogen ion concentration. Here, we investigated nanoscale interactions\nof PtNPs at alkanethiol modified gold electrode surfaces and examined\nthe effects of monolayer hydrophilicity and hydrophobicity on single\nparticle collision dynamics. After colliding with and adsorbing onto\nthe modified electrode surface, PtNPs generate a measurable cathodic\ncurrent arising from the reduction of hydrogen. Each single particle\ncollision is indicated by a spike-step or spike of current in the\ncurrent time trace. The shape, frequency, and size of these current\nsteps are dependent on the terminal chemistry of the alkanethiol covalently\nbound to the electrode surface. Using the collisional frequency as\na function of PtNP concentration, we determined the rate of particle\nadsorption, <i>k</i><sub>ads</sub>, to be 2.23 × 10<sup>–6</sup> cm/s and 8.85 × 10<sup>–6</sup> cm/s\nfor −CH<sub>3</sub> and −OH terminated surfaces, respectively.\nElectrodes modified with a mixture of alkanethiols (−CH<sub>3</sub>/–OH) exhibited collision frequencies that scale linearly\nwith the ratio of hydrophilicity of alkanethiol immobilized on the\nelectrode surface. The results indicate the dependence of intermolecular\neffects on PtNP collision dynamics at the electrode surface, with\nhydrophobic-dominating surfaces having the least observed collisions.\nThis study provides insights into the influence of surface chemistry\non single nanoparticle interactions, which could advance the designs\nof biosensors and more efficient nanocatalysts by offering a deeper\nunderstanding of the interfacial mechanism of PtNPs on modified electrode\nsurfaces.