3439 nanochemistry - uzhfa82ef8a-ce2d-4b1d... · r r g f e opt stat marcus‐theory of the charge...
TRANSCRIPT
WillkommenWelcomeBienvenue
3439Nanochemistry
Andreas Borgschulte([email protected])
Introduction
CHE729.1
Mi. 10:15-12:00
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?
Contents of this lecture
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.
Definition / History
Ref. wikipedia
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
http://www.msm.cam.ac.uk/polymer/research/nanointroCNT.html
Multi-walled nanotubes
• 63GPa tensile strength(steel 1.2GPa)
• Inner tubes slide without friction
Picture credit: Alexander Aius, Wikipedia https://www.youtube.com/watch?v=O1WpE5ntqbQ
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/advanced-physicsprize2010.pdf
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…
Akin Akturk and Neil Goldsman, J. Appl. Phys. 103, 053702 (2008); A. H. Castro Neto et al., Rev. Mod. Phys., Vol. 81, 109 (2009)
∗12 ⋯
Massless Dirac quasiparticles in graphene
Oleg Shpy
Band structure in crystalline solids: Bloch functions
airRr /2exp)()( 0
Theory
k = 0
k = /a
k = 0
k = 0 k = /a
E(k)
E0
),()(2
2
rrrRVm
Schrödinger equation solvable for limited number of atoms
N ~ 1023
N < 103
M. D. Hanwell
Nanomaterials102 … 105
atoms
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)
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)
H2 combustion needs 600°C without, proceeds at RT with Pt catalyst
Catalysis of hydrogen combustion
Döbereiner Cigar lighter (1823)
H + H (E = 2.4 eV)
MHMH *22
OHOHOH 222 2*2*42
Catalytic hydrogen burner (Empa 2009)
Pt-nano particles on a ceramics
Surface Reaction
Solid–liquid interface: Electrochemical Double layer
pote
ntia
ldistance
-
water
solid +
+
+
+
+
+
nm
mol/lIIeNTk
A
BrD
34.02 2
01
xxTkB
expze with
Debye length
T. Cosgrove, Colloid Science, Principles, methods, and applications, Wiley 2010;
-+-
-0
-0
The mystery of electrochemistry
kTUEekj /0 1
H
H+
H
H
H2O-H+
H2O-H+
H2O-H+
H2Oe-e-
H2O-H+
H2
H+ H3O+ch
emic
al p
oten
tial
reaction coordinate
U
U
E
kTUUEekj /0 '
The hydrogen electrode: Butler‐Volmer equation
H2
Pt-electrode
Ubjj )(loglog 0
G
reaction coordinate
free
ener
gy
21111)( eRr
efGstatopt
Marcus‐Theory of the charge transfer
TkGTkB
4
exp)(20
Transition-state Theory
electrostatic contribution
4
20GG + chemical
contribution G0
metalsphere
metalsphere
Ion
G
e
free
ener
gy
R.A. MarcusNobel price 1992
TkGTkB
4
exp)(20
00 IG
0IIG
0IIIG
G
q=e
reactant / Product I/II/III
Experimental confirmation of Marcus theory
R. Marcus, Angew. Chem. lnt. Ed. Engl. 1993, 32. 1111
Variation of G0 at constant
-1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2
1E9
1E10
1E11
1E12
1E13
k (s
-1)
G (eV)
ln ∝∆
4 ∙
0.5 0.4 0.3 0.2 0.1 0.0 -0.10.1
1
10
100
j (m
A/c
m2 )
U = G (eV)
ln ∝ 2 ln
+- +
inverted region
Electron transfer between molecules ~ Electrodes
S. Murphy, et al., J. Org. Chem., 60, 2411, 1995; M. H. Miles, et al. J. Electrochem. Soc., Bd. 123, p. 332, 1976.
∝∆2
B
Reorganization energy
sv
The outer part corresponds to the energy cost from the solvent response.
The inner part corresponds to the energy cost due to geometry modifications to go from a neutral to a charged geometry and vice versa.
0 50 100 150 2001.4
1.6
1.8
2.0
2.2
volta
ge (V
)
current density (mA cm-2)
TkGTkB
4
exp)(20
of the first electron transfer only ~0.25 eV out of an overall excitation energy of 1.38 eV
R. Marcus, Angew. Chem. lnt. Ed. Engl. 1993, 32. 1111
Simplified spatial scheme of photosynthesis
ADP+P
ATP
4H + O+2
2 H O2
H+ NADP + H+
NADPH
3H+
OEC
HECP680/Q PQ
PC
P700/Q
cyto
chro
me
ATP
synt
hase
lumen
stroma
Lurgi, Zdansky-Lonza pressure electrolysis: (a) Bipolar electrodes, dimple plate cell partition; (b) Pre-electrodes in the form of nets on both sides of asbestos diaphragms ;(c) Asbestos diaphragms; (d) Cell frame;
(Häussinger P., et al., 2006)
gas separation by membranesl = 1mm
Alkaline water electrolyzers: electrolyte/membrane
+ -H2O2
Mg1 Mg1
Mg1Mg1 Mg1
SiO4SiO4
Mg2Mg2
SiO4 SiO4
Mg1 Mg1
Mg1Mg1 Mg1
Mg2Mg2
Mg2 Mg2
SiO4
Mg2
SiO4
Mg1Mg1
Mg1Mg1 Mg1
SiO4SiO4
Mg2Mg2
SiO4 SiO4
Mg1 Mg1
Mg1Mg1 Mg1
Mg2Mg2
SiO4
Mg2
SiO4
Mg1Mg1
Mg1 Mg1Mg1
http://webmineral.com/
Olivine, (Mg,Fe)2SiO4)
Main unit for all silicates :
O
Si
SiO4
SiO4
SiO4
SiO4
SiO4
SiO4
SiO4
SiO4
SiO4
Quartz SiO2
Chrysotile(Asbestos):Mg3Si2O5(OH)4
Betechtin, Mineralogy, 1951
Top: SEM image of a chrysotile, Mg3Si2O5(OH)4, one of the asbestos minerals) fiber bundle. Bottom: through the fiber bundle (Ref: Grobety et al.,)
BO
NBO
Pyroxene, (Fe, Ca,Mg)2Si2O6
Silicates: crystal structure
However, the physical shape of material can seriously affect its toxicity
Asbestos
Serpentine– flat sheets of atoms, harmless
Chrysotile– nano-scale tubes
One should treat these new nano-materials with caution
Nano-structured membranes have superior properties
http://whatisasbestosis.com/risks-of-asbestos-exposure/
Nanotoxicity
Empa Nanosafety Research: Human macrophage exposed to Hematite-Nano particles (70 nm). SEM
band-aid coated with Ag nano particles (Empa)
C. A. Poland et al. nature nanotechnology 3, 423 (2008)
‘frustrated’ phagocytosis of carbon nanotubes by peritoneal macrophages.
Asbestos nano fibres cause lung cancer
Nanotoxicity of Au-particles
All nanoparticles within the 2–100 nm size range were found to alter signalling processes essential for basic cell functions (including cell death), 40- and 50-nm nanoparticles demonstrated the greatest effect.
W. Jiang et al. nature nanotechnology 3, 145 (2008)
Buckyball(~1nm)DNA
(~2nm diameter)
Red blood cells(~2-5μm)
Hair (~60-120μm)Virus(10-300nm)
Gold atom(135pm)
10mm
1mm
0.1mm
0.01mm
0.001mm, 1μm (1000nm)
0.1μm (100nm)
0.01μm (10nm)
1nm
Ult
ravi
olet
Infr
ared
Mic
row
ave
0.1nm
10-2m
10-3m
10-4m
10-5m
10-6m
10-7m
10-8m
10-9m
10-10m
X-ra
y
Courtesy ZoeSchnepp
Bio-nano machines (<10 nm) Ag-nanoparticles(1-100 nm)
colloids, (micro-) emulsion phase diagrams, stability Ostwald ripening, coalescence electrochemical double layer,
zeta-potential rheology Aerosols
Tyndall effect
Colloids
pics_: Wikipedia
NAd
2
resolution limit of the microscope
Can we see nano structures?
optics: d ~ 200 nmelectron microscope d < 1 nm
JEOL 2200FS TEM/STEMHigh-resolution and analytical STEM/TEMTomographyPoint resolution TEM 0.23 nmResolution STEM 0.16 nm
Ernst Karl Abbe
Scanning Probe Microscopy
Measuring physical interaction (z)
Use it as a control parameter to map the surface
Force (AFM) Tunneling current (STM) Capacity (SCAM) Light (SNOM) Thermal properties
+
+- -
+-
s
R
1st images of Si (111): Binnig and Rohrer 1982
Tunneling current in STM
U I
surface tip
vacuummetal metal
dEF
Atomic resolution of ||2 (no atoms!)
Size and surface area effects 1 nm – 100 nm Fundamental materials properties remain the same but size, shape and surface area alter some behaviors such as work function, solubility, chemical potential, contaminate sorption
Critical Size and Characteristic Length Scale Interesting or unusual properties because the size of the system approaches some critical length (includes quantum effects). Many characteristics of material may have normal or nearly normalbehavior
New (Non-extensive) Properties Systems not large enough to have extensive properties. Particles become effectively polymorphs of “bulk” materials and statistical homogeneity may not be valid.
Size dependent properties
0.1
1
10
100
1000
spec
ific
surf
ace
area
[m2 g
-1]
10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3
characteristic length [m]
1020
1015
1010
105
100
number of atom
s per particle
C
Pd
ratio surface atoms / bulk atoms
rVm 2
contribution by surface energy significant below 3 nm
Size dependent properties
45
Size dependent properties
Melting Temperature of Au Clusters
Ph. Buffat and J.-P. Borel, Phys. Rev. A 13, 6 1976), pp. 2287-2298
Au~800
24 Å
rHV
TT m
2
Catalytic properties of Au Clusters
X. Lai, D. W. Goodman, J. Molecular Catalysis A: 162, (2
Size dependent properties
Optical properties of Au Clusters
Lycurgus cup(Roman times)
Illuminated from behind, the gold nanoparticle-containing dichroic glass that the cup is made from appears deep red in color.
window glass(Medieval times)
Maksym V. Kovalenko ,* Erich Kaufmann , Dietmar Pachinger , Jürgen Roither , Martin Huber , Julian Stangl , Günter Hesser,Friedrich Schäffler , and Wolfgang Heiss, J. Am. Chem. Soc., 2006, 128 (11), pp 3516–3517
Angshuman Nag, Maksym V. Kovalenko, Jong-Soo Lee, Wenyong Liu, Boris Spokoyny, and Dmitri V. Talapin, J. Am. Chem. Soc., 2011, 133 (27), pp 10612–10620
Size dependent properties
Colloidal HgTe Nanocrystals with Widely Tunable Narrow Band Gap Energies: From Telecommunications to Molecular Vibrations
Metal-free Inorganic Ligands for Colloidal Nanocrystals: S2–, HS–, Se2–, HSe–, Te2–, HTe–, TeS32–, OH-, and NH2– as Surface Ligands
http://www.nanoscience.at
Preparation of nano structures
The ‘top-down’ approach
The ‘bottom-up’ approach
structuring matter“Nanotechnology”
self-assembly“Nanochemistry”
The quantum corral reef -An academic gadget (Eigler et al. IBM)
Nanostructuring on atomic length scale (Top-down)
G. Medeiros-Ribeiro et al., Phys. Rev. B 58, 3533 (1998)
external transport
homogeneous nuleationheterogeneous
adsorption-desorption
Cluster-kinetics
surface-diffusion
growth- kinetics
Nanostructuring by thin film technology
physical vapor deposition (bottom-up) chemical vapor deposition (bottom-up) sputtering (bottom-up) electrochemistry (bottom-up) ion etching (top-down) (photo-)lithography (top-down)
0 10 20 30 400
10
20
30
40
50
Ti(C,N)-phase Ni-phase
sche
rrer
cry
stal
lite
size
[nm
]
m illing time [h]
Nanostructuring by ball milling (Top-down)
Courtesy Nico Eigen
Preparation: The ‘bottom-up’ approach
Small molecules or particles pre-designed to self assemble into larger, organised structures
e.g. surfactants Hydrophilic head group
Hydrophobic tail
Spherical micelle
water
oil
oil
oil
oil oil
Courtesy Zoe S h
http://www.biologycorner.com/resources/DNA-colored.gif
Sugar phosphate
backbone
Bottom-up approach in nature
Guanine Cytosine
Adenine Thymine
Courtesy Zoe S h
relevant biosystem can be grown/studied in labs
Nano particles in Freshwater Biofilms
Stream biofilm inhabitants. By D. C. Sigee
http://www.iees.ch/EcoEng061/EcoEng061 Rijstenb
400 500 600 700
0.2
0.4
0.6
0.8
1.0
1.2
Abs
orba
nce
Wavelength [nm]
After 0 h After 1 h After 10 h After 20 h
+++++++++++++++++++++
++++++++++++++++++++++++++
++++++++++++++++++
- - - - - - -- - - - - - - - - -
- - - - - - - - - - - -- - - - - - - - - - -
- - - - - - - - -
- - - - - - -- - - - - - - - - -
- - - - - - - - - - - -- - - - - - - - - - -
- - - - - - - - -
- - - - - - -- - - - - - - - - -
- - - - - - - - - - - -- - - - - - - - - - -
- - - - - - - - -
+
=
plasmon oscillation
discrete positive nuclei positive background
free electron cloud
jellium
UV-VIS on Silver-Nanoparticles
Interaction depends on size of the Nano particles
principles of existing / future technologies
What are the scientific questions to be addressed?
chemistry
biology
physics
chemical engineering
principles of existing / future technologies Underlying science / methods
What are the scientific questions to be addressed?
computer science
surface science / microscopy
experimental methods, tools, concepts
principles of existing / future technologies Underlying science / methods What are the problems/limits of these technologies?
What are the scientific questions to be addressed?
applications
materials properties
safety/cost/abundancepicture by Zoe Schnepp
principles of existing / future technologies Underlying science / methods What are the problems/limits of these technologies? future visions
What are the scientific questions to be addressed?
artificial photosynthesis
nanocar
24.02.2016Introduction 02.03.2016Measurement of Nanostructures I 09.03.2016Measurement of Nanostructures II 16.03.2016Optical Properties 23.03.2016Surface Science I 06.04.2016Surface Science II 13.04.2016Preparation of nano structures I 20.04.2016Preparation of nano structures II 27.04.2016Applications I: Catalysis 04.05.2016Applications II: Energy 11.05.2016Applications III: Wetting, Colloids 18.05.2016Theory 25.05.2016cell biology / Nanotoxicity 01.06.2016seminar talks
Contents of lecture NanoChemistry