Shannon Cattie
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How does temperature affect the rate of
aggregation of colloidal gold?
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What is Colloidal Gold?
 Binary liquid mixture, containing gold nanoparticles
 Can be ingested orally to treat arthritis, hypertension, skin conditions,
heart rhythm, depression, inflammation, circulation, pain and stress
relief, nerve complaints, and act as an IQ booster
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History of Colloidal Gold
 Appearance in the Old Testament of the Bible (Exodus 32)
▪ Moses makes a make-shift colloidal gold to cure the impatience and
disobedience of the nation of Israel
 Alexandria, Egypt
▪ Alchemists discussed the Elixir of Life
▪ 16th century: alchemist, Paracelsus, founded the school of iatrochemistry, the
chemistry of medicines - beginning of modern pharmacology
 Ancient Rome
▪ Used to stain glass a deep red
 Used for photography in 1842 in the process of crysotype
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Nanotechnology
 Deals with processes that take place on the nanometer
scale, which is one billionth of a meter.
 Properties of metals are different on the Nano scale than
in bulk.
▪ Gold in bulk is a yellowish color, but gold’s nanoparticles are a winered
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Aggregation
 The formation of aggregates causing a change in color
 For the most part, irreversible
 An aggregate is a group of particles which are held
together; they can be held together in any way
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Why add Salt to Aggregate Colloidal Gold?
 Gold particles in colloidal solutions are negatively charged,
so they repel each other. They cannot clump together.
 Salt is added:
▪ Shields the negative charges
▪ Able to clump together and aggregate
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Why does Colloidal Gold turn Blue after Aggregation?
 Because of the change in the light spectra
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Salt
 Sodium chloride
 Suppose to lower the temperature in which aggregation
occurs
 Enhances aggregation
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If the temperature of colloidal gold is raised,
then the particles of the colloidal gold will
aggregate more readily than those at lower
temperatures.
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Journal
Pen
Aluminum foil
Refrigerator
Thermometer
A micro pipette
Spectro Vis
Logger Pro
10mL graduated cylinder
Paper towels
TO MAKE THE COLLOIDAL
GOLD
20 mL of 1mM hydrogen
tetrachloroaurate solution
 Distilled water
 2mL of 1% trisodium
citrate solution
 A hot plate
 An Erlenmeyer flask
 Graduated cylinder
 Crucible tongs
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FOR EACH TRIAL
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A cuvette and cap
1000 μL of 1 M sodium
chloride solution
3mL of colloidal gold
100μL of the solution
Make the Colloidal Gold
1.
Measure 20 mL of 1mM hydrogen tetrachloroaurate solution in a
graduated cylinder
2.
Pour the 20 mL of 1mM hydrogen tetrachloroaurate solution into a 250 mL
Erlenmeyer Flask
3.
Add distilled water to the 200 mL mark on the Erlenmeyer flask
4.
Place the Erlenmeyer flask onto a hot plate and turn the hot plate on a
medium-high setting
5.
Bring to a gentle boiling
6.
Measure 2mL of 1% trisodium citrate solution using a 10 mL graduated
cylinder
7.
Add the 2mL of 1% trisodium citrate solution to the boiling solution in the
Erlenmeyer flask
8.
Continue heating the solution at a gentle boil for about 10 minutes until the
solution is stable at a ruby or wine-red color and no longer changes color
9.
After the color stabilizes, remove the Erlenmeyer flask from the hot plate
and allow to cool
10.
Add distilled water until the solution reaches 200 mL again
1.
Begin by hooking up the spectrometer to the computer and opening
Logger Pro
2.
Measure 3 mL of Colloidal gold into a 10 mL graduated cylinder
3.
Pour it into a cuvette
4.
Cap the cuvette, wipe the sides of excess liquid, and place into the
spectrometer
5.
Locate the peak of absorption on the graph and record
6.
Heat colloidal gold to 30°C by using a hot plate, let sit for the day and
accumulate to room temperature (10°C), or place in refrigerator and cool
to 10°C
Procedure – Testing the
Aggregation
7. Collect the location of the peak of absorption on each
graph after following this procedure:
a. Add the colloidal gold to the cuvette
b. Measure 100 microliters of sodium chloride solution
using a micropipette
c. Add the 100 microliters of sodium chloride solution into
the cuvette
d. Shake the cuvette once, and let sit for approximately 20
seconds
e. Place into Spectro Vis
f. Collect data
g. Repeat ten times
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Independent variable: Sodium chloride
solution
Dependent variable: Aggregation rate
Control: Room temperature
Constants: Colloidal gold and amount of
sodium chloride solution added
Colloidal Gold at 10°C
Colloidal Gold at 10°C
800
800
700
600
600
Peak of Graph (nm)
Peak of Graph (nm)
R² = 0.8565
700
500
400
300
500
400
300
200
200
100
100
0
0
0
100 200 300 400 500 600 700 800 900 1000
Sodium Chloride Solution (μL)
0
100 200 300 400 500 600 700 800 900 1000
Sodium Chloride Solution (μL)
Colloidal Gold at 20°C
Colloidal Gold at 20°C
800
800
700
600
600
Peak of Graph (nm)
Peak of Graph (nm)
R² = 0.785
700
500
400
300
500
400
300
200
200
100
100
0
0
0
100 200 300 400 500 600 700 80 900 1000
Sodium Chloride Solution (μL)
0
100
200
300
400
500
600
700
Sodium Chloride Solution (μL)
80
900 1000
Colloidal Gold at 30°C
Colloidal Gold at 30°C
800
700
R² = 0.8773
700
600
500
Peak of Graph (nm)
Peak of Graph (nm)
600
500
400
300
400
300
200
200
100
100
0
0
0
100 200 300 400 500 600 700 800 900 1000
Sodium Chloried Solution (μL)
0
100
200
300
400
500
600
700
Sodium Chloried Solution (μL)
800 900 1000
Rate of Aggregation Between Three Temperatures
700
650
Peak of Graph (nm)
600
10C
550
20C
30C
500
450
400
0
100
200
300
400
500
600
Sodium Chloride Solution (μL)
700
800
900
1000
Rate of Aggregation Between Three Temperatures
750
10C
700
20C
30C
650
Peak of Graph (nm)
Linear (10C)
Linear (20C)
600
Linear (30C)
550
R² = 0.8565
R² = 0.785
500
R² = 0.8773
450
400
0
100
200
300
400
500
600
Sodium Chloride Solution (μL)
700
800
900
1000
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The data received showed all three temperatures
aggregated similarly.
 The hypothesis was rejected at the temperatures
tested.
 Further testing would be needed to conclude
whether higher temperatures of colloidal gold
increase the rate of aggregation.
Importance of this experiment:
 Pertains much to recent scientific discoveries
about nanotechnology
 Nanotechnologists are testing the ability of
colloidal gold to target cancer tumors.
Possible Errors:
 The testing taking place on different days
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o Slight temperature, humidity, and weather change
Change in temperature as the trials were being done
o Temperature was not monitored after being placed in the cuvette
o Solution could have accumulated to room-temperature without
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acknowledgement, although efforts were made to work quickly in
order to manage this temperature change.
Sodium chloride solution not beginning at the same temperature as
the colloidal gold
Improvements to this experiment:
 Make the sodium chloride solution the same temperature as the
colloidal gold, removing any difference in temperature between
what was recorded
 Monitor the solution temperature during procedure
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