Quantification of Quantum Dots in Solution using Surface Plasmon Resonance, Densitometry, and Analytical Ultracentrifugation

Quantum Dots are semiconducting nanocrystals with the ability to fluoresce under ultraviolet light. They have several applications including cellular imaging and drug delivery. To date, an accurate technique of measuring the concentration of quantum dots in solution is yet to be implemented, as the current methods of quantifying quantum dot solutions are prone to error. It is the goal of this project to craft a novel approach in measuring the concentration of quantum dots in solution. This would provide for more efficient use of quantum dots across their associated disciplines. Using surface plasmon resonance, we have determined a correction factor relating response units to refractive index. From this data and from the partial specific volumes calculated via densitometry, we are able to verify differential refractive index values for four different quantum dots in PBS solution.  The differential refractive indices allow us to relate total fringe values calculated from analytical ultracentrifugation to the concentration of quantum dots in solution. Ultimately, this potentiates the conversion of optical density values of quantum dots to their respective molar absorptivity constants. Upon completion of this project, we will be able to provide differential refractive index and molar absorptivity values of four different quantum dots to the scientific community, making the use of these nanocrystals more effective.