Materials Engineering Department
BS in Materials Engineering
Richard Savage, Trevor Harding
Quantum dots have become an active area of research in the past decade due to their unique properties. Quantum confinement effects allow for efficient spectral conversion and size tunable fluorescence and absorption peaks. Near infrared spectral converting lead sulfide quantum dots have potential applications in solar power, biological imaging and communications technology. However at Cal Poly, lead sulfide dots have not been synthesized. The quantum dot synthesis currently adapted at Cal Poly encompasses organometallic precursors at high reaction temperatures, producing cadmium selenium dots. The organometallic approach has been found to produce nanocrystals with high quality photoluminescence, but due to its hazardous reaction parameters an environmentally safe synthesis is desired. The aim of this study was to adapt and develop an aqueous “green” synthesis method for producing lead sulfide quantum dots to Cal Poly. The method used within this study, previously reported Jiao, encompasses a low temperature aqueous synthesis method using low toxicity surfactant precursors SDS, CTAB and EDTA dissolved into deionized water heated to 70 C. A solution of lead acetate was injected into the surfactant solution to produce lead ion EDTA complexes. Thiourea solution was then slowly injected to introduce sulfur allowing lead sulfide to form. The formation of lead sulfide could be seen by the transformation of the solution from buff to dark brown. Samples taken from this solution were naturally cooled, centrifuged and rinsed with alcohol and DI water. Fluorescence and absorbance testing was conducted on produced samples to test for the presence of quantum dots. In addition, commercially purchased lead sulfide quantum dots were fluorescence tested for comparison to our samples.