In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface

“Methanol occupies a central role in chemical synthesis and is considered an ideal candidate for cleaner fuel storage and transportation. It can be catalyzed from water and volatile organic compounds, such as carbon dioxide, thereby offering an attractive solution for reducing carbon emissions.”*

In “In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface” the authors show that graphite immersed in ultrapure water is able to spontaneously catalyze methanol from volatile organic compounds in ambient conditions. Using single-molecule resolution atomic force microscopy (AFM) in liquid, they directly observe the formation and evolution of methanol–water nanostructures at the surface of graphite.*
The findings described in this article could have a significant impact on the development of organic catalysts and on the function of nanoscale carbon devices

NanoWorld ARROW-UHFAuD AFM probes were used for the Atomic Force Microscopy imaging in liquid.

Figure 1 from “In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface” by W. Foster et al.: High-resolution amplitude modulation AFM imaging of HOPG immersed in initially ultrapure water. (a) A solid-like patch formed by the self-assembly of molecules (dashed white outline) nucleates from an atomic step at the HOPG surface (dashed black line). The molecular self-assembly is observed here in situ as it progressively grows across the HOPG surface over a period of 9 min, with the patch edges moving away from the step. Rowlike structures with a periodicity of 4.30 ± 0.28 nm as visible within the patch. (b) Sub-nanometer imaging of other structures reveals detailed features (0.79 ± 0.08 nm periodicity, red arrows) perpendicular to the main rows (periodicity 2.45 ± 0.08 nm, white arrow). The exact molecular arrangement is not known, but strongly reminiscent of the alternated water–methanol nanoribbons recently reported by our group.(22) The white scale bars are 100 nm in (a) and 1 nm in (b). The purple color scale bar represents a topographic variation of 20 Å in (a) and 1 Å nm in (b). The blue scale bar represents a phase variation of 20° in (a) and 10° in (b). In (a) the time lapse between the first and second frames is 1 min and then 4 min elapses between the subsequent frames. NanoWorld Arrow-UHFAuD AFM probes were used.
Figure 1 from “In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface” by W. Foster et al.: High-resolution amplitude modulation AFM imaging of HOPG immersed in initially ultrapure water. (a) A solid-like patch formed by the self-assembly of molecules (dashed white outline) nucleates from an atomic step at the HOPG surface (dashed black line). The molecular self-assembly is observed here in situ as it progressively grows across the HOPG surface over a period of 9 min, with the patch edges moving away from the step. Rowlike structures with a periodicity of 4.30 ± 0.28 nm as visible within the patch. (b) Sub-nanometer imaging of other structures reveals detailed features (0.79 ± 0.08 nm periodicity, red arrows) perpendicular to the main rows (periodicity 2.45 ± 0.08 nm, white arrow). The exact molecular arrangement is not known, but strongly reminiscent of the alternated water–methanol nanoribbons recently reported by our group.(22) The white scale bars are 100 nm in (a) and 1 nm in (b). The purple color scale bar represents a topographic variation of 20 Å in (a) and 1 Å nm in (b). The blue scale bar represents a phase variation of 20° in (a) and 10° in (b). In (a) the time lapse between the first and second frames is 1 min and then 4 min elapses between the subsequent frames

*William Foster, Juan A. Aguilar, Halim Kusumaatmaja, Kislon Voϊtchovsky
In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface
ACS Appl. Mater. Interfaces, 2018, 10 (40), pp 34265–34271
DOI: 10.1021/acsami.8b12113

Please follow this external link for the full article: https://pubs.acs.org/doi/full/10.1021/acsami.8b12113

Open Access The article “In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface” by William Foster, Juan A. Aguilar, Halim Kusumaatmaja and Kislon Voϊtchovsky is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Direct observation of the dynamics of single metal ions at the interface with solids in aqueous solutions

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!

Figure 3 from: "Ricci, M. et al. Direct observation of the dynamics of single metal ions at the interface with solids in aqueous solutions."
Figure 3 from: “Ricci, M. et al. Direct observation of the dynamics of single metal ions at the interface with solids in aqueous solutions.“: Kinetic experiments conducted in pure water (a) show mainly two levels (arrows) when compared to Fig. 2a. Height variations are less pronounced than in RbCl solution and analysis of the surface dynamics (inset) reveals slower timescales with a relatively strong dependence on the choice of threshold. The profile shown in the inset is taken after site averaging (see e.g. Fig. 2d), hence the small height variations. More reliable results were obtained for lower threshold values (here −20 pm, see Supplementary Fig. S10). The overall ratio between the two levels visible in (a) can be changed by adjusting the pH of the water with HCl (b–g), suggesting the higher level to be related to hydration water and the lower level to reflect adsorption of H3O+, as detected by the AFM tip. For each of the pH value studied, the raw kinetic experiments (b,e) are site-averaged (c,f) as in Fig. 2d to remove the mica corrugation and imaging noise. The height distribution of the site-averaged data is then binarised automatically (d,g) depending on whether the surface height is higher or lower than the average between the surface’s highest and lowest points. The fraction of surface interpreted as covered with H3O+ (purple in d and g) changes from 55 ± 3% to 75 ± 2%. (b,e) were acquired with a same tip. The mica samples have been rinsed with the imaging solution after being cleaved and the presence of K+ ions on the surface can be neglected (concentration <10 nM). The scale bar is 3 nm in all experiments.

Abstract:
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 Reports volume 7, Article number: 43234 (2017)
doi: https://doi.org/10.1038/srep43234

Please follow this external link for the full article: https://rdcu.be/4QVb

This article “Direct observation of the dynamics of sigle metal ions at the interface with solids in aqueous solutions” by Ricci, M. et al. is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

High resolution imaging of amorphous glass surfaces in liquid

Inspired by Kristen M. Burson et al.’s “Resolving amorphous solid-liquid interfaces by atomic force microscopy”, Applied Physics Letters 108, 201602 (2016); http://aip.scitation.org/doi/abs/10.1063/1.4949556, the scans below were made by Dr. Roger Proksch of Asylum Research using a NanoWorld Arrow UHF AFM probe and an Asylum Cypher Atomic Force Microscope.

Figure 1. Topography images of disordered lattice imaged at an amplitude setpoint of 2 nm. a) 10nm scan and b) 5nm scan. Both images clearly demonstrate sub-nm amorphous glass surface.
Figure 1. Topography images of disordered lattice imaged at an amplitude setpoint of 2 nm. a) 10nm scan and b) 5nm scan. Both images clearly demonstrate sub-nm amorphous glass surface.

 

 

 

 

 

 

Figure 2. a) Surface topography and b) tip-sample stiffness of a region of the glass sample imaged using AMFM stiffness mapping. 10 nm scan
Figure 2. a) Surface topography and b) tip-sample stiffness of a region of the glass sample imaged using AMFM stiffness mapping. 10 nm scan

 

 

 

 

 

 
 

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.

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