Catalytic Segregation of Graphene Using Silver
Nanoparticles
Brandon R. Reed CHEM318 Introduction A fast developing field
Desirable to cut correct shapes
Few techniques currentlyavailable This research
illustratesreproducible results. Catalytic Environment
Catalysis occurs at the step edges of graphene. At high
temperatures, silver nanoparticles located at theseedges are able
to channel trenches through the graphene. nanoparticle Catalytic
Environment
Mechanism of channeling Particles cling to surface defects
Energetically favorable Reaction involves oxygen chemisorbed by
particle (Silveroxide). Oxidize atoms of graphene into CO2. Follows
the receding edge Chemiabsorbed> reaction silveroxide? 3nm
graphene fold resonate 00: 22:38 - resonate
00: 50:54 - film uplifts 3nm graphene fold resonate Ag
Nanoparticles-Multiple Methods
NaBH4 and AgNO3 on ice Laser reflection colloidal solution. No
aggregation, citrate buffer: double layer of charge,
stabilizesparticles and prevents aggregation Ag Nanoparticles -
Buffers
Magnetite Nanoparticle Buffers & aggregation Materials &
Methods highly oriented pyrolytic graphene (HOPG)
Aqueous AgNO2 vs AgNO3 High temp (650 C ). In heated quartz tube (D
= 3cm). Imaging Ag particles : Scanning Force Microscopy (SFM)
& ScanningTunneling Microscope (STM). HOPG= high purity of
crystal lattice. Note D = diameter HOPG structure Lattice
multi-layered
highest degree of three dimensionalordering Essentially low
imperfections vsregular graphene samples Mosaic Spread roughness
Less cleavability Data & Results SFM surface morphology
SFM images graphene 1 min anneal = no etching. Cutting speed/trench
length correlated to size of the nanoparticles. Properties Findings
Trench Length 9.0 uM Trench Width 6-100 nm Max Speed 250 nm s-1 (a)
SFM height image of a sample annealed for 45 s
(a) SFM height image of a sample annealed for 45 s. The area is
chosen to demonstrate that trenches channeled through graphene
layers of different thickness. (b) Dependence of trench length on
trench width for trenches formed in graphene bilayer on a sample
annealed for 1 min (see Supporting Information for dependencies for
other graphene thickness). The dashed line is the linear fit. (c)
STM image of a monolayer trench on a sample annealed for 1 min
reveals smooth edges with peak-to-peak roughness (i.e., d) below 2
nm. The width of the imaged trench is about 9 nm. (d) SFM height
image of a sample annealed for 1 min, a few examples of spiral (S)
and zigzag (Z) trenches are outlined. Notice that particles can
switch back and forth between spiral or zigzag and straight
channeling. Trenching Types Silver nanoparticles stay along the
defects or step edges of thegraphene. 3 types of trenches: Straight
segmented trenches Spiral tranches Zig zag trenches Alternate
trench formation causes Pollution of sample Sulfur Dioxide HOPG vs
regular graphene. The roughness of the regular would skew data.
Spiral Trenching Talk about how spiral trenching occurs. Pollution
Insight HOPG covered with silver nitrite in the presence of a small
amount ofsulfur. 1-min run. Annealing of a new sample brief
ventilation Spiral trenching. Insight poisoning of the catalyst
responsible for formation of spiraltrenches Further studies needed.
Just silver dioxide? Conclusions Fast channeling of large
nanoparticles vs small
Rate-limiting step is the adsorption of molecular oxygen Larger
particles assemble at higher step edges Max channeling speed 250
nm/s is of importance Implications: any size particle capable given
enough oxygen Future Possibilities? YES!
New applications High precision lithography on graphenes. Catalysis
applications probe tip. Current Research Developments - kirigami
Current Research Developments - kirigami Current Research
Developments - Shape
Slater, J.A. Thomas; Macedo, Alexandra; Schroeder, L. M. Sven; et
al; Correlating Catalytic Activity of Ag-Au Nanoparticles with 3D
compositional Variations. ACS, 2014, 14, Ag and AuCl4- Current
Research Developments - Shape
Slater, J.A. Thomas; Macedo, Alexandra; Schroeder, L. M. Sven; et
al; Correlating Catalytic Activity of Ag-Au Nanoparticles with 3D
compositional Variations. ACS, 2014, 14, References Severin, N.;
Kirstein, I. M. Sokolov; Rabe, J. P.; Rapid Trench Channeling of
Graphenes withCatalytic Silver Nanoparticles. 2009, 9, Slater,
J.A.; Macedo, A.; Schroeder, L. M. Sven; et al; Correlating
Catalytic Activity of Ag-AuNanoparticles with 3D compositional
Variations. ACS, 2014, 14, Barberio, M.; Barone, P.; Imbrogno, A.;
Xu, Fang.; CO2 adsorption on silvernanoparticle/carbon nanotube
nanocomposites: A study of adsorption characteristics, J.
physicastatus solidi, 2015, Vol. 252, 9, 19551959. Bahadory, M. S.;
Synthesis of Silver Nanoparticles, Journal of Chemical Education,
2007, 84, Oldenburg, J. S.; Silver Nanoparticles: Uses and
Applications, Sigma Aldrich, NanoComposixInc HOPG Detailed
Description,2014,accessed: 8 October 2015. Blees, M.; Nature-Video
Research-Graphene Kirigami.edge/, 2015, accessed: 14 September
2015. Questions Additional Notes/ Questions Quad image-notes (a)
SFM height image of a sample annealed for 45 s. The area is chosen
todemonstrate that trenches channeled through graphene layers of
different thickness. (b) Dependence of trench length on trench
width for trenches formed in graphenebilayer on a sample annealed
for 1 min. The dashed line is the linear fit. (c) STM image of a
monolayer trench on a sample annealed for 1 min revealssmooth edges
with peak-to-peak roughness below 2 nm. The width of the
imagedtrench is about 9 nm. (d) SFM height image of a sample
annealed for 1 min, a few examples of spiral (S)and zigzag (Z)
trenches are outlined. Notice that particles can switch back and
forthbetween spiral or zigzag and straight channeling. Sulfur
Dioxide Pollution-Notes
To propve pollution of catalyst, team annealed HOPG covered with
silver nitrite in the presence of a small amount of sulfur. SFM
imaging of results showed inhibition of channeling: the trenches
were no longer than 50 nm (not shown). Annealing of a new sample
after a brief ventilation produced mostly spiral type of trenches,
which proves the poisoning of the catalyst to be responsible for
the formation of spiral trenches. Thus these experiments give a
nanoscopic insight into the poisoning mechanism of catalysts.
Quantitative characterization of catalyst poisoning will require
further investigations. NOT DETERMINITIVE