BS in Materials Engineering
Materials Engineering Department
Quantum dots show great potential for use as spectral converters in solar cells, lighting applications and biological imaging. These applications require precise control of quantum dot size to maximize performance. The fluorescence profile of quantum dots in solution correlates directly with particle size. An alternative, high precision process was developed for the synthesis of cadmium-selenide quantum dots using a microfluidic reactor and fluorescence flow through cell. The process required creating separate cadmium and selenium precursors that were then mixed in a nitrogen environment at 17± 1°C. Using an NE-300® syringe pump, the solution was pumped through a microfluidic reactor submerged in a 235°C oil bath. Then, the tubing fed into a water quench bath at 25°C to terminate the reaction. The fluorescence profiles of the quantum dot solutions were then characterized with an in-line fluorescence flow cell used in conjunction with an Ocean Optics USB4000® spectrometer and a ThorLabs® LED UV light source. Flow rates through the reactor were varied from 0.1 mL/min to 1.6 mL/min at increments of 0.1 mL/min. Separation of subsequent samples was achieved by introducing a bubble of nitrogen gas between each flow rate. A central peak wavelength was registered in the fluorescence profiles of each flow rate. Peak wavelengths ranged from 490nm up to 585nm and a relationship between flow rate and center wavelength was determined.