Transcript Molecular Biomimetics: Synthesizing Gold Nanostructures

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 AuCl4 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 (Alanine,
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
AuCl4
-
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
C3H7NO2
Arginie
Arg R 174.2g/mol
C6H14N4O2
-4.5
.0009mol(.15678g)
Asparagine
Asn N 132.188g/mol
C4H8N2O3
-3.5
.0009mol(.1189692g)
Aspartic Acid
Asp D 133.10g/mol
C4H7NO4
-3.5
.0009mol(.11979g)
Cysteine
Cys C 121.16g/mol
C3H7NO2S
2.5
.0009mol(.109004g)
Glutamic Acid Glu E 147.13g/mol
C5H9NO4
-3.5
.0009mol(.132417g)
Glutamine
Gln Q 146.15g/mol
C5H10N2O3
-3.5
.0009mol(.131535g)
Glycine
Gly G 75.07g/mol
C2H5NO2
-0.4
.0009mol(.067563g)
Histidine
His H 155.16g/mol
C6H9N3O2
-3.2
.0009mol(.139644g)
Isoleucine
Ile
131.17g/mol
C6H13NO2
4.5
.0009mol(.118053g)
Leucine
Leu L 131.18g/mol
C6H13NO2
3.8
.0009mol(.118062g)
Lysine
Lys K 146.188g/mol
C6H14N2O2 12
-3.9
.0009mol(.1315692g)
Methionine
Met M 149.21g/mol
C5H11NO2S
1.9
.0009mol(.134289g)
Phenylalanine Phe F 165.19g/mol
C9H11NO2
2.8
.0009mol(.148671g)
Proline
Pro P 115.13g/mol
C5H9NO2 12
-1.6
.0009mol(.103617g)
Serine
Ser S 105.09g/mol
C3H7NO3
-0.8
.0009mol(.094581g)
Threonine
Thr T
C4H9NO3
-0.7
.0009mol(.107208g)
Tryptophan
Trp W 204.225g/mol
C11H12N2O2
-0.9
.0009mol(.1838025g)
Tyrosine
Tyr Y 181.19g/mol
C9H11NO3
-1.3
.00045mol(.0815355g)
Valine
Val V 117.15g/mol
C5H11NO2
4.2
.0009mol(.105435g)
HAuCL4 3H2O
I
119.12g/mol
393.845g/mol
1.8
.0009mol(.08019g)
0.0005mol(.196923g)
Speciation of Gold Nanostructures (0.5mM AuCl4 pH 3 0.0M NaCl)
C
Extremely small, granular gold structures
D
Medium, thin, overlapping, truncated triangle
gold structures
W
Extremely small, granular gold
structures
P
Medium, solid, polygonal gold structures
Reduction Rate of Amino Acids
(0.5mM AuCl4 pH 3 0.0M NaCl)
Averages and Standard Deviation for Gold Synthesized by Amino Acids (Set 1,2,3)
0.14
Synthesized Gold (mg/mL)
0.12
0.10
0.08
0.06
0.04
0.02
0.00
W Y C M H K N D F L
I
T S G P R E V Q A CT
Amino Acids
0.5mM AuCl4 (0.0M, 0.1M, 0.5M NaCl) pH 5 Comparison
(Lysine and Asparagine)
L-PH5-0.0N NaCl
Small, head and tail w/
granular, gold structures
L-PH5-0.1N NaCl
Large, head and tail w/
morphing into polygonal
plates
L-PH5-0.5N NaCl
Large, solid polygonal
plate, gold structures
N-PH5-0.0N NaCl
Small, granular, gold
structures
N-PH5-0.1N NaCl
Small, head and tail w/
clusters, gold structures
N-PH5-0.5N NaCl
Very small, solid polygonal
plate, gold structures
Wavelength Scans by Functional Group (pH 5)
Absorbance vs Wavelength (Set 1)
1.8
0.24
1.6
0.22
0.20
C
M
N
Q
S
T
W
Y
1.4
F
G
I
L
P
V
0.16
0.14
0.12
0.10
1.2
Absorbance
0.18
Absorbance
Absorbance vs Wavelength (Set 1)
0.08
1.0
0.8
0.6
0.06
0.4
0.04
0.02
0.2
0.00
200
400
600
800
1000
0.0
200
1200
400
600
Wavelength(nm)
Absorbsance vs Wavelength (Set 1)
2.6
800
1000
1200
Wavelength(nm)
0.09
2.4
Absorbance vs Wavelength (Set 1)
0.08
2.2
0.07
2.0
0.06
1.6
H
K
R
1.4
1.2
1.0
Absorbance
Absorbance
1.8
0.05
D
E
0.04
0.03
0.8
0.6
0.02
0.4
0.01
0.2
0.0
200
400
600
800
Wavelength(nm)
1000
1200
0.00
200
400
600
800
Wavelength(nm)
1000
1200
0.5mM AuCl4 (0.0M, 0.1M, 0.5M NaCl) pH 5 Color Comparison
Lysine
Asparagine
0.5mM AuCl4 0.0M NaCl pH 3 and 5 Comparison of Geometry
N-PH3
Large, solid & thin, gold structures
N-PH5
Extremely small, granular gold
structures
V-PH3
Medium, solid, hexagonal gold
structures
V-PH5
Small, head and tail, gold structures
with extremely small, granular gold
structures
Geometry Change (20mM AuCl4)
0.0N NaCl
3.2
4.5
pH
5.2
7.5
11.6
0.1N NaCl
0.5N NaCl
Reduction Rate (20mM AuCl4)
Gold Synthesized by Amino Acids (0.02M AuCl pH 3.2)
0.030
0.030
0.025
0.020
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.015
0.010
0.005
Gold Synthesized (mg/mL)
0.025
Gold Synthesized (mg/mL)
Gold Synthesized by Amino Acids (pH 3.2)
0.020
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.015
0.010
0.005
0.000
0.000
A
F
C
M
H
K
D
E
A
CTRL
F
C
K
D
E
CTRL
0.025
0.020
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.015
0.010
Gold Synthesized (mg/mL)
0.025
Gold Synthesized (mg/mL)
H
Gold Synthesized by Amino Acids (pH 3.2)
0.030
Gold Synthesized by Amino Acids (pH 4.5)
0.030
M
Amino Acids
Amino Acids
0.020
0.015
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.010
0.005
0.005
0.000
0.000
A
F
C
M
H
K
Amino Acids
D
E
CTRL
A
F
C
M
H
Amino Acids
K
D
E
CTRL
Gold Synthesized by Amino Acids (pH 5.2)
0.06
0.05
0.04
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.03
0.02
0.01
Gold Synthesized (mg/mL)
0.05
Gold Synthesized (mg/mL)
Gold Synthesized by Amino Acids (pH 5.2)
0.06
0.00
0.04
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.03
0.02
0.01
0.00
A
F
C
M
H
K
D
E
CTRL
A
F
C
M
H
Amino Acids
0.025
K
D
E
CTRL
Amino Acids
Gold Synthesized by Amino Acids (pH 4.5)
Gold Synthesized by Amino Acids (pH 4.5)
0.024
0.022
0.020
0.015
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.010
0.005
Gold Synthesized (mg/mL)
Gold Synthesized (mg/mL)
0.020
0.018
0.016
0.014
0.012
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.010
0.008
0.006
0.004
0.002
0.000
A
F
C
M
H
K
D
E
0.000
CTRL
A
Amino Acids
M
H
K
D
E
CTRL
Gold Synthesized by Amino Acids (pH 11.6)
0.045
0.040
0.040
0.030
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.025
0.020
0.015
0.010
Gold Synthesized (mg/mL)
0.035
0.035
Gold Synthesized (mg/mL)
C
Amino Acids
Gold Synthesized by Amino Acids (pH 11.6)
0.045
F
0.030
0.025
0.0NNaCl
0.1NNaCl
0.5NNaCl
0.020
0.015
0.010
0.005
0.005
0.000
0.000
A
F
C
M
H
K
Amino Acids
D
E
CTRL
A
F
C
M
H
K
Amino Acids
D
E
CTRL
pH 3.2
pH 4.5
pH 7.5
pH
pH 5.2
pH 11.6
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 [AuCl4] – 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 [AuCl4] -, : 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.