Category: Featured

Spontaneous Selective Deposition of Iron Oxide Nanoparticles on Graphite as Model Catalysts

Defect generation process steps.

Chathura de Alwis (Chemistry), Timothy R. Leftwich (MSE), Pinaki Mukherjee (MSE), Alex Denofrea (Chemistry) and Kathryn A. Perrine (Chemistry) published a paper titled “Spontaneous selective deposition of iron oxide nanoparticles on graphite as model catalysts” in Nanoscale Advances in 2019.

DOI: 10.1039/c9na00472f

Extract

Iron oxide nanomaterials participate in redox processes that give them ideal properties for their use as earth-abundant catalysts. Fabricating nanocatalysts for such applications requires detailed knowledge of the deposition and growth. We report the spontaneous deposition of iron oxide nanoparticles on HOPG in defect areas and on step edges from a metal precursor solution.

Various defects were created on the highly oriented pyrolytic graphite (HOPG) surface using either argon (Ar+) sputtering or a focused ion beam (FIB) to provide defects for nucleation sites. A Hitachi 2000 A FIB instrument was used to create tailored arrays of defects on HOPG using a Ga+ beam.

The sputter rate was calculated using the amount of materials removed, by recording a height profile of 1 nm using atomic force microscopy (AFM) and the time to sputter the pattern.

All the samples were imaged using a Hitachi S-4700 cold field emission high resolution field emission scanning electron microscopy (FE-SEM) instrument.

X-ray photoelectron spectroscopy (XPS) was performed using a PHI 5800 to analyze the elemental composition and oxidation state of surface species of the iron oxide nanoparticles grown on the HOPG surface.

Scanning transmission electron microscopy (STEM) imaging and energy dispersive X-ray spectroscopy (EDS) mapping were used to measure the phase and composition of iron oxide nanoparticles after annealing and to confirm if the deposition was preferential at the defect sites of graphite. A FEI Titan Themis aberration corrected scanning transmission electron microscope was used to obtain atomically resolved electron images and EDS maps of the iron oxide nanoparticles on the graphene coated TEM grid. The microscope was operated at 200 kV using a point resolution of the aberration corrected STEM mode of 0.08 nm. The microscope was equipped with a SuperX™ X-ray detector, which is composed of 4 detectors for fast X-ray mapping in STEM mode. The EDS mapping of the sample was performed on specific particles with an average beam current of 100 pA.

Acknowledgements

Equipment for obtaining the AFM images in this project was provided by NSF CHE #1725818. The electron microscopy research was performed at the Applied Chemical and Morphological Analysis Laboratory, at Michigan Technological University. The electron microscopy facility is supported by NSF MRI 1429232. We acknowledge the Michigan Tech REF-RS fund for support of this work and the David J. and Valeria Pruett Graduate Research Fellowship. We acknowledge the Applied Chemical and Morphological Analysis Laboratory (ACMAL) for staff assistance and use of facilities.

Recommended Citation

de Alwis, C., Leftwich, T., Mukherjee, P., Denofre, A., & Perrine, K. (2019). Spontaneous selective deposition of iron oxide nanoparticles on graphite as model catalysts. Nanoscale Advances, 1(12), 4729-4744.

http://doi.org/10.1039/C9NA00472F

Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/1246


FESEM and FIB Used in Area-selective Atomic Layer Deposition Research

Surface Science cover for volume 690 December 2019.
Raman confocal images of Al2O3 make the cover of Surface Science.

Graduate students Mikhail Trought (Chemistry) and Chathura de Alwis (Chemistry), with undergraduate student alumnus Isobel Wentworth (ChemEng), research assistant professor Timothy R. Leftwich (MSE), and assistant professor Kathryn A. Perrine (Chemistry) published a paper titled “Influence of surface etching and oxidation on the morphological growth of Al2O3 by ALD” in Surface Science on August 9, 2019.

https://doi.org/10.1016/j.susc.2019.121479

The authors acknowledge the Applied Chemical & Morphological Analysis Laboratory (ACMAL) at Michigan Technological University for use of instruments and staff assistance, including Director Owen Mills, for training on the FESEM and FIB.

M. Trought and K. Perrine prepared the samples at Michigan Tech and at the Univ. of Minnesota, performed the surface analysis, analyzed all data collected, and wrote the manuscript. T. Leftwich assisted with the XPS data collection and analysis, and reviewing & editing the manuscript. I. Wentworth and C. de Alwis assisted with sample preparation and FTIR analysis. K. Perrine conceptualized the project.


S-TEM Tomography Video

Screenshot of particles in a box with 500 nm scale bar
S-TEM Tomography of Li-ion Battery Cathode Particles

Watch the Video

Research by Stephen A. Hackney, Professor, Materials Science and Engineering, Michigan Technological University.

Imaging by Pinaki Mukherjee, Staff, Materials Science and Engineering, Engineer/Scientist, Applied Chemical and Morphological Analysis Laboratory (ACMAL).

Instrument: FEI 200kV Titan Themis S-TEM in ACMAL’s Electron Optics Facility.

Scale bar indicates 500 nm.

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Surface Analysis Using the XPS

PHI 5800 X-ray Photoelectron Spectrometer
PHI 5800 X-ray Photoelectron Spectrometer

Analyzing the surface of materials takes X-ray vision.

To do so, researchers peer into the surface chemistry of materials using X-ray photoelectron spectroscopy (XPS). At Michigan Technological University, the Applied Chemical and Morphological Analysis Laboratory (ACMAL) delves into surfaces with a PHI 5800 XPS.

Read more at Be Brief: Surface, by Allison Mills.

Timothy Leftwich, research assistant professor of materials science, helps researchers to collect, analyze, and understand their XPS data at the ACMAL facility. Kathryn Perrine, assistant professor of chemistry, helped to bring the XPS instrument to Tech and teaches students and researchers to understand surface processes. They both bring expertise in surface science and analysis of materials.


Graphite exfoliation by supercritical carbon dioxide extraction

Wattanaprayoon Supercritical Carbon Dioxide
A schematic of graphite exfoliation by supercritical carbon dioxide.

Extract

Supercritical carbon dioxide is used to exfoliate graphite, producing a small, several-layer graphitic flake. The supercritical conditions of 2000, 2500, and 3000 psi and temperatures of 40°, 50°, and 60°C, have been used to study the effect of critical density on the sizes and zeta potentials of the treated flakes. Photon Correlation Spectroscopy (PCS), Brunauer-Emmett-Teller (BET) surface area measurement, field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) are used to observe the features of the flakes.

Wattanaprayoon, Chaiyaporn, “Graphite exfoliation by supercritical carbon dioxide extraction”, Master’s Thesis, Michigan Technological University, 2011.

https://digitalcommons.mtu.edu/etds/8