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1
Interface MD
Application
July 15, 2017
Hendrik HeinzDepartment of Chemical and Biological
EngineeringMaterials Science and Engineering Program
University of Colorado-Boulder, CO, USA
2
Predict Facet-Specific Binding of Peptides in
Solution to Surfaces and Nanoparticles (Pd)
Ramezani-Dakhel et al. 2017, 9, 8401-8409.
Pd4 @ {111} Pd4 @ {100}Pd4 @ {110}
10 Å
5 Pd4 @ 21 Å
5 Å
C D E
F G
∆𝑬𝒂 = -68±1 ∆𝑬𝒂 = +3±1∆𝑬𝒂 = -43±2
∆𝑬𝒂 = -20±1 ∆𝑬𝒂 = -17±1 Pd C N O H
7 Pd4 @ 26 Å 9 Pd4 @ 31 Å
∆𝑬𝒂 = -29±2
H
Pd4 peptide = TSNAVHPTLRHL
3
aPredict of Activity of Pd Nanoparticle Catalysts in C-C
Coupling Reactions (Stille Reaction)
H. Ramezani-Dakhel, M. R. Knecht, R. R. Naik, H. Heinz PCCP 2013; ACS Nano 2015, 9, 5082; Chem. Sci. 2015, 6, 6413.
Catalytic efficiency is predictable for any
given particle shape, determined from HE-
XRD/PDF data, and using the computed
atom leaching rate
Ei : abstraction energy of atom i
N
i
RT
E
N
i
eN
R1
1~
RN : total rate of abstraction
N : total number of surface atoms
a b
c
35-45
45-55
55-65
25-35
65-75
> 85
Abstraction energy
(kcal/mol)
75-85
Ei : abstraction energy of atom i
N
i
RT
E
N
i
eN
R1
1~
RN : total rate of abstraction
N : total number of surface atoms
a b
c
35-45
45-55
55-65
25-35
65-75
> 85
Abstraction energy
(kcal/mol)
75-85
Ei : abstraction energy of atom i
N
i
RT
E
N
i
eN
R1
1~
RN : total rate of abstraction
N : total number of surface atoms
a b
c
35-45
45-55
55-65
25-35
65-75
> 85
Abstraction energy
(kcal/mol)
75-85
Mechanism
Particle
shape
(Pd4)
Ei : abstraction energy of atom i
N
i
RT
E
N
i
eN
R1
1~
RN : total rate of abstraction
N : total number of surface atoms
a b
c
35-45
45-55
55-65
25-35
65-75
> 85
Abstraction energy
(kcal/mol)
75-85
Activity
Ei : abstraction energy of atom i
N
i
RT
E
N
i
eN
R1
1~
RN : total rate of abstraction
N : total number of surface atoms
a b
c
35-45
45-55
55-65
25-35
65-75
> 85
Abstraction energy
(kcal/mol)
75-85
Rate
determining
step
4
Explain Interlayer Structure in Clay Minerals
(Alkylammonium-Montmorillonite)
• Increase of basal-plane spacing in a step-like pattern according to the
formation of an alkyl monolayer, alkyl bilayer etc (<5% dev from XRD)
• Gallery spacing for peralkylated head groups rises smoothly and is shifted by
~ 2 C atoms relative to primary ammonium head groups (“bumpy” due to H bonds)
0 2 4 6 8 10 12 14 16 18 20 22 2412
13
14
15
16
17
18
19
20
21
22
23
Ba
sa
l p
lan
e s
pa
cin
g (
A)
Carbon atoms per chain
NH3 head group
NMe3 head group
monolayer
complete
bilayer
complete
HRTEM of MMT
embedded in an
epoxy matrix
(Drummy et al.
JPCB 2005)
Heinz et al. J. Am. Chem. Soc. 2003, 125, 9500. Heinz et al. Chem. Mater. 2007, 19, 59-68.
(CnH2n+1NR3)0.33(Si4O8)[Al1.67Mg0.33O4(OH)4]
CEC 90 mmol/100g
5
Identify Atomic Positions and Structure in Alloys
and Carbides By Imaging Plus Simulation
3D structure of a WCx tip containing
amorphous carbon inclusions:
x ~0.15 at surface and ~8 layers penetration
Str
ain
fie
ld in
exp
eri
me
nt
Str
ain
fie
ld in
MD
sim
ula
tio
n
With Jianwei Miao, UCLA,
U. Dahmen, LBL,
W. Ercius, Birmingham (UK)
Imaged at TEAM I
(currently largest EM)
Xu et al. Nat. Mater. 2015, 14, 1099.
6
Understand Mechanisms of Cement Hydration
(CSH) with Polycarboxylate Ethers
(100) surface of
tobermorite 14 Å
7
Supply Realistic, pH-Resolved Surface Models –
Example: Silica Surface Model Database
0% ionized – 4.7 OH/nm2 (pzc)
pH~4 for 20 nm particle
pH~2.5 for 400 nm particle*
9% ionized –
pH~7 for 20 nm particle
pH~5 for 400 nm particle
18% ionized –
pH~9 for 20 nm particle
pH~7 for 400 nm particle
Typical: Q3 surfaces, 4.7 SiO(H,Na) per nm2, with 0-20% ionization
Amorphous Q3, Q3/Q4, Q2 surfaces with 0-20% ionization
Si O O- Na+ H
2 nm
Emami, Perry, and Heinz et al. Chem. Mater. 2014, 26, 2647.
8
Understand Nanocrystal Growth – Example:
Hydroxyapatite Biomineralization
Exptl data from C. Tamerler, U Kansas
(020)
-27-25
-15
-48
HAp (001) HAp (101) HAp (010) HAp (020)0
-10
-20
-30
-40
-50
Ad
so
rpti
on
en
erg
y (
kc
al/
mo
l)
HAp cleaved surface
Peptide HABP 1 strong binding
(MLPHHGA)
11
-15
5
14
HAp (001) HAp (101) HAp (010) HAp (020)20
15
10
5
0
-5
-10
-15
-20
Ad
so
rpti
on
en
erg
y (
kc
al/
mo
l)
HAp cleaved surface
Peptide HABP 2 nonbinding
(NPGFAQA)
(020)
(020)
9
Explain Molecular Control Over Pt Nanocrystal Shape
Using a Phenyl Molecular Switch
Y. Huang and H. Heinz et al. Nano Letters 2013, 13, 840.
Synthesis
from H2PtCl6with sodium
borohydride
and ascorbic
acid in the
presence of
peptides
Binding
contrast
between
{111} and
{100}
surfaces
determines
preferred
shape
With Y. Huang,
UCLA
Ramezani-Dakhel et al. Adv. Funct. Mater. 2015, 25, 1374.
10
• Up to 70% reduction in cohesive
energy of hydroxylated (040)
cleavage plane by grinding aids
• Significant differences among
molecules depending on surface-
specific mitigation of local electric
fields0
100
200
300
400
500 HC: Hydroxylated C3S
Ag
glo
me
ratio
n E
nerg
y,
mJ/m
2
C3S HC HC-Gly HC-TEA HC-TIPA HC-MDIPA
Discover Mechanism of Mineral Agglomeration and
Working Principle of Grinding Aids (Ca3SiO5)
Mishra, Flatt, Heinz J. Phys. Chem. C 2013, 117, 10417. Sandmeyer Award (SCS 2016).
• 0.5 nm thin
organic layer
eliminates >90%
of attractive
Coulomb forces
Heinz, Farmer et al. J. Chem. Phys. 2006, 124, 224713.