For the AFM measurements in the article “Direct observation of the dynamics of single metal ions at the interface with solids in aqueous solutions” by Ricci, M. et al. a NanoWorld Arrow-UHFAuD AFM probe was used. Congratulations to the authors!
The dynamics of ions adsorbed at the surface of immersed charged solids plays a central role in countless natural and industrial processes such as crystal growth, heterogeneous catalysis, electrochemistry, or biological function. Electrokinetic measurements typically distinguish between a so-called Stern layer of ions and water molecules directly adsorbed on to the solid’s surface, and a diffuse layer of ions further away from the surface. Dynamics within the Stern layer remain poorly understood, largely owing to a lack of in-situ atomic-level insights. Here we follow the dynamics of single Rb+ and H3O+ ions at the surface of mica in water using high-resolution atomic force microscopy with 25 ms resolution. Our results suggest that single hydrated Rb+ions reside τ1 = 104 ± 5 ms at a given location, but this is dependent on the hydration state of the surface which evolves on a slower timescale of τ2 = 610 ± 30 ms depending on H3O+ adsorption. Increasing the liquid’s temperature from 5 °C to 65 °C predictably decreases the apparent glassiness of the interfacial water, but no clear effect on the ions’ dynamics was observed, indicating a diffusion-dominated process. These timescales are remarkably slow for individual monovalent ions and could have important implications for interfacial processes in electrolytes.
Maria Ricci, William Trewby, Clodomiro Cafolla, Kislon Voïtchovsky Direct observation of the dynamics of single metal ions at the interface with solids in aqueous solutions Nature Scientific Reportsvolume 7, Article number: 43234 (2017)
Using blueDrive and the NanoWorld Arrow UHF AFM tip, it was also possible to simultaneously map the topography and tip-sample stiffness using AM-FM mode (Figure 2). Like Burson et al., a disordered-appearing surface, with length scales similar to those reported in that paper could be seen. Interestingly, these structures were visible with slightly different resolutions with every attempt made. This is a testament to the low noise of the Cypher AFM and to the reliable sharpness of the Arrow UHF cantilevers.
Courtesy of Dr. Roger Proksch, Asylum Research, an Oxford Instruments Company.
Ethan J. Miller, William Trewby, Amir Farokh Payam, Luca Piantanida, Clodomiro Cafolla, Kislon Voïtchovsky, Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid (2016), JoVE, 1940-087X, doi:10.3791/54924