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