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3439 Nanochemistry
Introduction Andreas Borgschulte ([email protected])
CHE729.1 Mi. 10:15-12:00 Contents of this lecture Introduction: We are assembled nano-machines! Nanotechnology History, Definition Visualization of nanostructures Size dependent properties Preparation of nano structures Bottom-up approach top-down approach theory Some applications colloids Hydrogen storage catalysis membranes cell biology Nanotoxicity What is NOT Nanochemistry? What are the scientific questions to be addressed? Definition / History
Nanotechnology is the manipulation of matter on an atomic and molecular scale. Generally, nanotechnology works with materials, devices, and other structures with at least one dimension sized from 1 to 100 nanometres.
The scanning tunneling microscope, an instrument for imaging surfaces at the atomic level, was developed in 1981 by Gerd Binnig and Heinrich Rohrer at IBM Zurich Research Laboratory
K. Eric Drexler developed and popularized the concept of nanotechnology and founded the field of molecular nanotechnology. In 1979, Drexler encountered Richard Feynman's 1959 talk There's Plenty of Room at the Bottom.
Ref. wikipedia Liquids/gases Pyrite FeS2
1023 Perovskite CaTiO3 3-mm diamond in eclogite graphene
Diamond
Graphite Fullerene Carbon nanotubes
• Allotrope of carbon • Graphite sheet rolled into a tube • 50,000x smaller than human hair • Members of fullerene family (including buckyballs)
www.ewels.info/img/science/nano.html Single-walled nanotubes
• Capped or uncapped • All covalent sp2 bonding • Metallic conductors or semiconductors • Bundles • Defects – points for reaction Multi-walled nanotubes
• 63GPa tensile strength (steel 1.2GPa) • Inner tubes slide without friction
http://www.msm.cam.ac.uk/polymer/research/nanointroCNT.html Graphene – the new Wonder material
Strength of graphene Graphene has a breaking strength of 42N/m, which is more than 100 times stronger than steel Electrical conductivity of graphene The sheet conductivity of a 2D material is given by . The mobility is theoretically limited to μ=200,000 cm2V−1s−1 by acoustic phonons at a carrier density of n=1012 cm−2. The 2D sheet resistivity, also called the resistance per square, is then 31 Ω. Our fictional hammock measuring 1m2 would thus have a resistance of 31 Ω. σ=enμ Using the layer thickness we get a bulk conductivity of 0.96x106 Ω-1cm-1 for graphene. This is somewhat higher than the conductivity of copper which is 0.60x106 Ω-1cm-1. Thermal conductivity The thermal conductivity of graphene is dominated by phonons and has been measured to be approximately 5000 Wm−1K−1. Copper at room temperature has a thermal conductivity of 401 Wm−1K−1. Background information Noble price in Physics 2010 https://www.nobelprize.org/nobel_prizes/physics/laureates/2010/advanc ed-physicsprize2010.pdf
Picture credit: Alexander Aius, Wikipedia https://www.youtube.com/watch?v=O1WpE5ntqbQ Massless Dirac quasiparticles in graphene
The intrinsic resistivity of graphene sheets would be 10−6 Ω⋅cm. This is less than the resistivity of silver. Electrons behave like a wave…
1 ∗ ⋯ 2
Akin Akturk and Neil Goldsman, J. Appl. Phys. 103, 053702 (2008); A. H. Castro Neto et al., Rev. Mod. Phys., Vol. 81, 109 (2009) Theory
2 M. D. Hanwell V R r (r) (r), 2m Schrödinger equation solvable for limited number of atoms N < 103
Nanomaterials 102 … 105 atoms Band structure in crystalline solids: Bloch functions N ~ 1023 (r R) (r) 0 exp2i / a
k = 0 E(k) k = 0 E0 k = /a Oleg Shpy k = 0 k = /a Nanoribbons for graphene transistors
Baringhaus, J.; Ruan, M.; Edler, F.; Tejeda, A.; Sicot, M.; Taleb-Ibrahimi, A.; Li, A. P.; Jiang, Z.; Conrad, E. H.; Berger, C.; Tegenkamp, C.; De Heer, W. A. Nature 506, 349–354 (2014)
J. Cai, P. Ruffieux, R. Jaafar, M. Bieri, T. Braun, S. Blankenburg, M. Muoth, A.P. Seitsonen, M. Saleh, X. Feng, K. Müllen, R. Fasel, Nature, 466, 470-473 (2010) Memory Chip Catalysis of hydrogen combustion
H combustion needs 600°C without, H 2 M 2H *M 2 proceeds at RT with Pt catalyst
H + H (E = 2.4 eV)
2H 2 O2 4H *2O* 2H 2O
Surface Reaction
Pt-nano particles on a ceramics
Catalytic hydrogen burner (Empa 2009) Döbereiner Cigar lighter (1823) Hydrogen dissociation on d-metals Solid–liquid interface: Electrochemical Double layer with ze kBT distance x exp x Debye length potential 1 0 r kBT 0.34 D 2 nm 2N Ae I Imol/l + water
+ - The mystery of electrochemistry
+ - + 0 0 + solid - - - +
+ T. Cosgrove, Colloid Science, Principles, methods, and applications, Wiley 2010; The hydrogen electrode: Butler‐Volmer equation
H 2 EU U / kT j k0 ' e Pt-electrode EU / kT j k0 1 e
U
U chemical potential H H O-H+ 2 E e- e- + H + H2O H2O-H H+ H3O+
+ H H2O-H reaction coordinate H2 H H O-H+ 2 log j log j0 b()U Marcus‐Theory of the charge transfer
metal metal sphere GG sphere free energy free energy
reaction ecoordinate R.A. Marcus Nobel price 1992 1 1 1 1 2 G f (e) e electrostatic r R opt stat contribution
0 2 G + chemical G 0 Ion 4 contribution G Transition-state Theory
0 2 G k(T ) exp 4k T B Experimental confirmation of Marcus theory
G reactant / Product I/II/III Variation of G0 at constant
0 GI 0
0 GII
0 GIII
q=e
0 2 G k(T ) exp 4k T B
R. Marcus, Angew. Chem. lnt. Ed. Engl. 1993, 32. 1111 Electron transfer between molecules ~ Electrodes