Molecular Biomimetics: Synthesizing Gold Nanostructures with ...

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Nov 15, 2013 (3 years and 6 months ago)

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Molecular
Biomimetics
:

Synthesizing Gold
Nanostructures with Amino
Acids


Alexander Chen

Chemical and Environmental Engineering Department, UC Riverside

Reasons For Using
Biomimetics


Simple and efficient method that creates
consistent nanostructures and patterns in
easily controllable environments.


Environmentally Safe
-

no harmful waste
are produced in comparison to chemical
methods of synthesis.


Has potential for greater compatibility and
efficiency for integration within biological
environments during medical use.

Process of Synthesizing Gold
Nanostructures with Amino Acids


The nanostructures are synthesized through mixing AuCl
4

and specific amino
acids within an aqueous solution and incubated (Mimicking physiological
environments in which typical synthesis reactions occur).



The gold structures that are formed are based on the specific binding properties
of each particular amino acid and the control of concentration, contents of
solution, pH, and temperature.



Synthesis Conditions and Procedure:


1mL samples consisting of 940ųL water, 40ųL 0.5mM or 20mM AuCl4, and 10ųL amino acid (A
lanine,
Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Glycine, Histidine, Isoleucine,
Leucine, Lysine, Methionine, Phenylalanine, Proline, Serine,Threonine, Tryptophan, Tyrosine, and Valine)

and 1 control sample with no amino acid


Excess chloride concentration were set at 0N, 0.1N, and 0.5N for various sets.


25M NaOH used to adjust pH to 3 and 5 for 0.5mM AuCl4 and to 3.2, 4.5, 5.2, 7.5, and 11.6 for 20mM
AuCl
4

-

Initial pH of each individual sample is recorded to ensure uniformity between samples (
±
0.1)

-

Solutions are incubated for 3 days at 37
°
C

-

Centrifuged and washed for three cycles at 10 rpm and 10min/cycle.

-

Final pH after the reaction are measured to examine correlation with synthesizing and binding efficiency.

-

10ppm of amino acid solution mixed with HCl(10%) to create 5mL solutionand measured gold ion concentration in


solution with AAS (Atomic Absorbtion Spectrophotometer).

-

Photographs of gold nanostructures and speciation taken with microscope.

Amino Acids and Gold Chloride Used to Make Standard Solution

Alanine


Ala A 89.1g/mol


C
3
H
7
N
O
2


1.8

.0009mol(.08019
g)

Arginie


Arg R 174.2g/mol

C
6
H
14
N
4
O
2



-
4.5

.0009mol(.156
78g)

Asparagine


Asn N 132.188g/mol

C
4
H
8
N
2
O
3



-
3.5

.0009
mol(
.118
9692g)

Aspartic Acid


Asp
D 133.10g/mol

C
4
H
7
N
O
4



-
3.5

.0009mol(.119
79g)

Cysteine


Cys C 121.16g/mol

C
3
H
7
N
O
2
S



2.5

.0009
mol(
.109004
g)

Glutamic Acid Glu E 147.13g/mol

C
5
H
9
N
O
4



-
3.5

.0009mol(.132417g)

Glutamine Gln Q 146.15g/mol

C
5
H
10
N
2
O
3



-
3.5

.0009mol(.131535g)

Glycine


Gly G 75.07g/mol

C
2
H
5
N
O
2


-
0.4

.0009mol(.
0
67563g)

Histidine


His H 155.16g/mol

C
6
H
9
N
3
O
2


-
3.2

.0009
mol(.139
644g)

Isoleucine


Ile I 131.17g/mol

C
6
H
13
NO
2

4.5

.0009mol(
.118
053g)

Leucine


Leu L 131.18g/mol

C
6
H
13
N
O
2


3.8

.0009mol(
.118
062g)

Lysine



Lys K 146.188g/mol

C
6
H
14
N
2
O
2

12

-
3.9

.0009mol(
.131
5692g
)

Methionine


Met M 149.21g/mol

C
5
H
11
N
O
2
S


1.9

.0009mol(
.134
289g)

Phenylalanine Phe F 165.19g/mol

C
9
H
11
N
O
2


2.8

.0009mol(
.148
671g)

Proline


Pro P 115.13g/mol

C
5
H
9
N
O
2

12

-
1.6

.0009mol(
.103
617g)

Serine



Ser S 105.09g/mol

C
3
H
7
N
O
3


-
0.8

.0009mol(
.094
581g)

Threonine


Thr T 119.12g/mol

C
4
H
9
N
O
3


-
0.7

.0009mol(
.
1
07
208g)

Tryptophan


Trp W 204.225g/mol

C
11
H
12
N
2
O
2


-
0.9

.000
9mol(
.183
8025g)

Tyrosine


Tyr Y 181.19g/mol

C
9
H
11
N
O
3


-
1.3

.00045mol(
.0815
355g)

Valine



Val V 117.15g/mol

C
5
H
11
N
O
2


4.2

.0009mol(
.105
435g)


HAuCL
4

3H
2
O

393.845g/mol

0.0005mol(.196923g)

C

Extremely small, granular gold structures

D

Medium, thin, overlapping, truncated triangle
gold structures

P

Medium, solid, polygonal gold structures

W

Extremely small, granular gold
structures

Speciation of Gold Nanostructures (0.5mM AuCl
4

pH 3 0.0M
NaCl
)

Reduction Rate of Amino Acids

(0.5mM AuCl
4

pH 3 0.0M
NaCl
)


W
Y
C
M
H
K
N
D
F
L
I
T
S
G
P
R
E
V
Q
A
CT
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Synthesized Gold (mg/mL)
Amino Acids
Averages and Standard Deviation for Gold Synthesized by Amino Acids (Set 1,2,3)
L
-
PH5
-
0.0N NaCl

Small, head and tail w/
granular, gold structures

N
-
PH5
-
0.0N NaCl

Small, granular, gold
structures

L
-
PH5
-
0.1N NaCl

Large, head and tail w/
morphing into polygonal
plates

N
-
PH5
-
0.1N NaCl

Small, head and tail w/
clusters, gold structures

L
-
PH5
-
0.5N NaCl

Large, solid polygonal
plate, gold structures

N
-
PH5
-
0.5N NaCl

Very small, solid polygonal
plate, gold structures

0.5mM AuCl
4

(0.0M, 0.1M, 0.5M
NaCl
) pH 5 Comparison

(Lysine and
Asparagine
)

200
400
600
800
1000
1200
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
Absorbance
Wavelength(nm)

F

G

I

L

P

V
Absorbance vs Wavelength (Set 1)
200
400
600
800
1000
1200
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Absorbance
Wavelength(nm)

C

M

N

Q

S

T

W

Y
Absorbance vs Wavelength (Set 1)
200
400
600
800
1000
1200
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
Absorbance
Wavelength(nm)

H

K

R
Absorbsance vs Wavelength (Set 1)
200
400
600
800
1000
1200
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
Absorbance
Wavelength(nm)

D

E
Absorbance vs Wavelength (Set 1)
Wavelength Scans

by Functional Group (pH 5)

Lysine

Asparagine

0.5mM AuCl
4

(0.0M, 0.1M, 0.5M
NaCl
) pH 5 Color Comparison

V
-
PH3

Medium, solid, hexagonal gold
structures

V
-
PH5

Small, head and tail, gold structures
with extremely small, granular gold
structures


N
-
PH3

Large, solid & thin, gold structures

N
-
PH5

Extremely small, granular gold
structures

0.5mM AuCl4 0.0M
NaCl

pH 3 and 5 Comparison of Geometry

0.0N NaCl

0.1N NaCl

0.5N NaCl

pH

3.2

4.5

5.2

7.5

11.6

Geometry Change (20mM AuCl
4
)

A
F
C
M
H
K
D
E
CTRL
0.000
0.005
0.010
0.015
0.020
0.025
0.030

0.0NNaCl

0.1NNaCl

0.5NNaCl
Gold Synthesized (mg/mL)
Amino Acids
Gold Synthesized by Amino Acids (0.02M AuCl pH 3.2)
A
F
C
M
H
K
D
E
CTRL
0.000
0.005
0.010
0.015
0.020
0.025
0.030
Amino Acids
Gold Synthesized (mg/mL)
Gold Synthesized by Amino Acids (pH 3.2)

0.0NNaCl

0.1NNaCl

0.5NNaCl
A
F
C
M
H
K
D
E
CTRL
0.000
0.005
0.010
0.015
0.020
0.025
0.030
Gold Synthesized by Amino Acids (pH 4.5)
Amino Acids
Gold Synthesized (mg/mL)

0.0NNaCl

0.1NNaCl

0.5NNaCl
A
F
C
M
H
K
D
E
CTRL
0.000
0.005
0.010
0.015
0.020
0.025
0.030
Gold Synthesized by Amino Acids (pH 3.2)
Gold Synthesized (mg/mL)
Amino Acids

0.0NNaCl

0.1NNaCl

0.5NNaCl
Reduction Rate (20mM AuCl
4
)

A
F
C
M
H
K
D
E
CTRL
0.000
0.005
0.010
0.015
0.020
0.025
Gold Synthesized by Amino Acids (pH 4.5)
Amino Acids
Gold Synthesized (mg/mL)

0.0NNaCl

0.1NNaCl

0.5NNaCl
A
F
C
M
H
K
D
E
CTRL
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.016
0.018
0.020
0.022
0.024
Gold Synthesized by Amino Acids (pH 4.5)
Gold Synthesized (mg/mL)
Amino Acids

0.0NNaCl

0.1NNaCl

0.5NNaCl
A
F
C
M
H
K
D
E
CTRL
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
Gold Synthesized by Amino Acids (pH 11.6)
Amino Acids
Gold Synthesized (mg/mL)

0.0NNaCl

0.1NNaCl

0.5NNaCl
A
F
C
M
H
K
D
E
CTRL
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
Gold Synthesized by Amino Acids (pH 11.6)
Amino Acids
Gold Synthesized (mg/mL)

0.0NNaCl

0.1NNaCl

0.5NNaCl
A
F
C
M
H
K
D
E
CTRL
0.00
0.01
0.02
0.03
0.04
0.05
0.06
Gold Synthesized by Amino Acids (pH 5.2)
Amino Acids
Gold Synthesized (mg/mL)

0.0NNaCl

0.1NNaCl

0.5NNaCl
A
F
C
M
H
K
D
E
CTRL
0.00
0.01
0.02
0.03
0.04
0.05
0.06
Gold Synthesized by Amino Acids (pH 5.2)
Amino Acids
Gold Synthesized (mg/mL)

0.0NNaCl

0.1NNaCl

0.5NNaCl
pH 3.2

pH 4.5

pH 5.2

pH 7.5

pH 11.6

pH

Species

Geometry

3.2

AuCl4
-

(Yellow)

Plates

4.5

AuCl3(OH)
-

(Yellow)

Plates

5.2

AuCl2(OH)2
-

(Yellow)

Head and Tail

7.5

AuCl2(OH)2
-

+ AuCl(OH)3
-
(Orange)

Dark Orange Film

11.6

AuC
(OH)3
-

+ Au(OH)4
-

(Clear)

Granular
Partcles

Conclusion


Decrease in pH allows for greater synthesizing and bonding efficiency.



Size of nanostructure and thickness is inversely related to synthesizing efficiency.



Lowering the pH shifts the species towards [AuCl
4
]



and plate structures.



Increasing excess chloride concentration using NaCl has same effect as lowering pH down.



Initial structure for 0.0N NaCl has a strong correlation with the specific wavelength in UV/vis
spectrophotometer, color of sample, and pH:



Granular particles: 480 nm, Violet/Brown/Green/Grey, pH<3.8



Head and tail w/ granular particles: 500nm, Black or Dark Green/Grey Precipitates with Clear
-
Light Grey
Solutions, pH>3.8



Morphology of the nano structures from [AuCl(OH)
3
]
-

to

[AuCl
4
]

-
, : granular
-
>dark film
-
>head and
tail
-
>cluster
-
>solid plates




Morphology has a trend based on functional group of amino acids.

-
Hydrocarbons: small head and tail w/ granular
-
>medium/large head and tail morphing into plates
-
>very small/small
solid plates.

-
Neutral: granular
-
>small head and tail or granular w/ gold clusters
-
>very small
-
very large solid plates.

-
Base: small head and tail/granular
-
>plate/morphing into plate
-
>small
-
medium plate

-
Acid: small head and tail/granular
-
>head and tail w/ clusters
-
>plate



When morphology shifts, the amount of gold synthesized increases dramatically (Figure 4).



Increasing gold concentration has a similar, but reduced, effect as increasing chloride concentration or


lowering pH and increases the size of the structures formed, as well. Also increases consistency of


species and variation of pH between different amino acids (Figure 2 and 6).


Reduction rate increases whenever there is a shift in morphology or shape and size of geometry


Future Experiments




Determine quantity of dominant species formed for each amino acid


at various other pHs and concentrations.




Further correlate trends between speciation, pH, solution color,


wavelength, and concentration.




Controlling the shape of synthesized gold structures through


changes in pH levels and chloride concentration.




Use specific peptides to synthesize uniform
nanowires

and


nanoplates

for use in electronic and medical sensors.

Acknowledgments



Thanks goes to the BRITE program and Jun Wang for organizing this wonderful
opportunity in research, and to Professor
Nosang

Myung

and Ms.
Jungok

Kim of the
Chemical and Environmental Engineering Department for their guidance and mentoring.