BS in Materials Engineering
Materials Engineering Department
A process was developed for the synthesis of cadmium-selenium quantum dots that fluoresce at multiple wavelengths, giving a white color to the solution. The process involved making a selenium pre-cursor, then a cadmium precursor, then injecting the selenium precursor into the cadmium precursor and extracting a sample. Once the a repeatable process for synthesizing white quantum dots was developed, the absorption and fluorescence was measured and recorded over a period of two weeks. In the development of the process, the key variables were the temperature of the cadmium precursor and the time between injecting the selenium precursor and extracting the sample. Extracting the quantum dots within the first second of injection and using a temperature of 220 ±6 °C repeatedly yielded the desired white quantum dots. The white dots exhibited three main fluorescence peaks: at 430-450 nm, 560-580 nm and 610-620 nm. The sample dots showed absorbance from 250 nm to 310 nm. Over time as the quantum dots remained in solution, the peaks shifted to higher wavelengths by 18.5 nm over two weeks, and the intensity decreased by 46%. The shift was caused by growth of the quantum dots over time, but did not significantly affect the visible white color of the dots. The testing showed white quantum dots could be made using a repeatable process with potential applications in white light LED technology.