1. The Effect of Temperature on the Aggregation of Colloidal Gold
Shannon Cattie

2. Problem
How does temperature affect the rate of aggregation of colloidal gold?

3. Background Information
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
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
Can you eliminate the items in the smallest print? You can SAY them, but don’t need to have them written.

4. Background Information
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 wine-red
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
Can you remove the item in the small print? You can say it but it doesn’t need to be written.

5. Background Information
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 shields negative charges, causing clumping
Why does Colloidal Gold turn Blue after Aggregation?
Because of the change in the light spectra
Salt (NaCl)
Suppose to lower the temperature in which aggregation occurs
Enhances aggregation
I re-formatted a bit.

6. Hypothesis
If the temperature of colloidal gold is raised, then the particles of the colloidal gold will aggregate more readily than those at lower temperatures.

7. Materials Journal Pen Aluminum foil Refrigerator Thermometer
A micro pipette
Spectro Vis
Logger Pro
10mL graduated cylinder
Paper towels

8. Materials 20 mL of 1mM hydrogen tetrachloroaurate solution
To make the colloidal gold
For each trial
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
A cuvette and cap
1000 μL of 1 M sodium chloride solution
3mL of colloidal gold
100μL of the solution

9. Procedure – Making the Colloidal Gold
Make the Colloidal Gold
Measure 20 mL of 1mM hydrogen tetrachloroaurate solution in a graduated cylinder
Pour the 20 mL of 1mM hydrogen tetrachloroaurate solution into a 250 mL Erlenmeyer Flask
Add distilled water to the 200 mL mark on the Erlenmeyer flask
Place the Erlenmeyer flask onto a hot plate and turn the hot plate on a medium-high setting
Bring to a gentle boiling
Measure 2mL of 1% trisodium citrate solution using a 10 mL graduated cylinder
Add the 2mL of 1% trisodium citrate solution to the boiling solution in the Erlenmeyer flask
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
After the color stabilizes, remove the Erlenmeyer flask from the hot plate and allow to cool
Add distilled water until the solution reaches 200 mL again

10. Procedure – Testing the Aggregation
Begin by hooking up the spectrometer to the computer and opening Logger Pro
Measure 3 mL of Colloidal gold into a 10 mL graduated cylinder
Pour it into a cuvette
Cap the cuvette, wipe the sides of excess liquid, and place into the spectrometer
Locate the peak of absorption on the graph and record
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
Equilibrate – not accumulate?

11. Procedure – Testing the Aggregation
7. Collect the location of the peak of absorption on each graph after following this procedure:
Add the colloidal gold to the cuvette
Measure 100 microliters of sodium chloride solution using a micropipette
Add the 100 microliters of sodium chloride solution into the cuvette
Shake the cuvette once, and let sit for approximately 20 seconds
Place into Spectro Vis
Collect data
Repeat ten times
Record the peak absorption not collect the location of the peak of absorption

12. Variables Independent variable: Sodium chloride solution
Dependent variable: Aggregation ratE
Control: Room temperature
Constants: Colloidal gold and amount of sodium chloride solution added
I Re-formatted a bit.

13. Data – Colloidal Gold at 10°C
I would just use one graph – use the trendline (the error bars don’t look quite right – it looks like you didn’t click and drag the stdev into the negative value)

14. Data – Colloidal Gold at 20°C
Same as previous

15. Data – Colloidal Gold at 30°C
same

16. Data – Comparison of all Three

17. Data – Comparison of all Three
You don’t need this graph

18. Conclusion
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.
Maybe the importance should be an additional slide?

19. Possible Errors and Improvements
The testing taking place on different days
Slight temperature, humidity, and weather change
Change in temperature as the trials were being done
Temperature was not monitored after being placed in the cuvette
Solution could have accumulated to room-temperature without 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
I made this a little bigger – you might consider just talking the improvements – they are really the same as the errors. I would put the error slide before the conclusion slide.

20. Works Cited
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Goldman, M. V. (n.d.). Absorption Spectra. In Absorption Spectra. Retrieved from Colorado Commission
on Higher Education and the National Science Foundation website:
physics/2000/quantumzone/fraunhofer.html
IUPAC. (2002, September 5). STABILITY OF COLLOIDAL SYSTEMS, AGGREGATION, COAGULATION, FLOCCULATION.
Retrieved from
Malvern Instruments Ltd. (2011). Colloidal Aggregation. Retrieved from
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11-13) [A Teacher's guide for experiments with colloidal gold]. Retrieved from
experiment-with-colorimetric-gold-nanosensors-teacher-guide-age-1113
Otwinowski, J. (2007, August 26). Temperature Induced Aggregation of Colloids [Journal testing the
effects of temperature on aggregation of colloids]. Retrieved from
~pschall/People/Alumni/Thesis_JakubOtwinowski.pdf
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Temperature and Salt [The effects temperature has on colloidal gold]. Retrieved from
database.
Space Today Online. (2003). Understanding Space Technology Spectrometers . Retrieved from
The Physics Classroom. ( ). Color and Vision. Retrieved from comPADRE website:
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Colloidal Gold]. Retrieved from