Fluorescence Measurement
In the experiment, the effects of both Mercaptocarboxylic acids and Mercaptoamines on the fluorescence of the Quantum Dots at various hydrocarbon chain lengths were investigated. Before both functional groups were compared, the relationship between hydrocarbon chain lengths and the fluorescence of the Quantum Dots within each functional group was investigated.
MERCAPTOCARBOXYLIC ACID
These are the fluorescence measurements for the samples with and without the ligand, when different wavelengths were shined on them. The blue graphs represent the control (Quantum Dots with no ligand attached), the red graphs represent the Quantum Dots coated with Thioglycolic acid, and the green graphs represent the Quantum Dots coated with 11-Mercaptoundecanoic Acid.
On the X-Axis, the first number shown is the excitation wavelength and the second number is the emission wavelength. The addition of ligands generally decreases the fluorescence of a Quantum Dot. This is possibly because of the aggregation of the quantum dots due to the hydrogen bonds and dipole interactions between the ligands.
It is difficult to compare the two ligands from the first graph as the control fluorescence is so high. In the graph above, they are being directly compared, with the control group removed from graph. It can be seen that the Quantum Dots coated with Thioglycolic Acid has an obviously much higher fluorescence than those coated with 11-Mercaptoundecanoic Acid.
 
MERCAPTOAMINE
As for the amine functional group, data was collected the same way and organised the same way. The blue graphs represent the control (Quantum Dots with no ligand attached), the red graphs represent the Quantum Dots coated with Cystamine, and the green graphs represent the Quantum Dots coated with 11-Amino-1-Undecanethiol. The controls, the uncoated Quantum Dots, also have higher fluorescence intensities than the quantum dots with ligands.
Comparing Cystamine directly with 11-Amino-1-Undecanethiol, we see that the Quantum Dots coated with Cystamine have a higher fluorescence than those coated with 11-Amino-1-Undecanethiol, similar to the results from the Carboxylic Acid functional groups.