Date of Award
MS in Engineering - Materials Engineering
A microfluidic reactor for synthesizing cadmium selenide (CdSe) quantum dots (QDs) was synthesized out of a silicon wafer and Pyrex glass. Microfabrication techniques were used to etch channels into the silicon wafer. Holes were wet-drilled into the Pyrex glass using a diamond-tip drill bit. The Pyrex wafer was anodically bonded to the etched silicon wafer to enclose the microfluidic reactor. Conditions for anodic bonding were created by exposing the stacked substrates to 300V at ~350oC under 5.46N of force. A syringe containing a room temperature CdSe solution was interfaced to the microfluidic reactor by using Poly (dimethylsiloxane) (PDMS) as an interface. The reactor was placed on a hot plate at 225oC, creating thermodynamic conditions for the QD chemical reaction to occur within the etched channels. Tygon® tubing transported solutions in and out of the microfluidic reactor. The CdSe solution was injected into the reactor by a syringe pump at an injection rate of 5 mL/hr, with a channel length of 2.5 cm. While in the microfluidic channels, QD residence time of approximately 30 seconds was sufficient enough for nucleation and growth of QDs to occur. The QD size was characterized by fluorescence full-width-half-maximum (FWHM), which is directly proportional to size distribution. The FWHM of the QDs synthesized was 38 nm, with a peak wavelength of 492 nm. By controlling combinations of pump rate and channel length, a range of QD sizes was able to be consistently synthesized through the microfluidic reactor with significant repeatability and reproducibility.