The Next Stage in Colloidal Synthesis of Aqueous CdSe Quantum Dots: High Throughput and Intense Emissive Properties

Abstract

Quantum dots (QDs) of CdSe have been produced with high yield using common reagents in water at 150 °C. The QDs thus produced are water compatible, show intense fluorescence emission and have high quantum yields (QYs). Their size can be controlled similarly to the high temperature organometallic method of synthesizing QDs, and these QDs produced in organic solvents at high temperature and the QDs produced in water both show comparable QYs. The great advantage is that a green solvent, water, is used and their separation from the water is very simple. They can be stored dry very easily. Similar to the organic method their size can be controlled by time, producing QDs with distinct fluorescence. The size obtained by TEM for 30, 60 and 90 minutes of reaction is 4.18 nm, 6.7 nm and 8.6 nm, respectively. This parallels the change in the emission wavelength of the QDs produced; green, yellow and orange, respectively. TEM dimensions are very similar to these of DLS (dynamic light scattering). These QDs display the hexagonal wurtzite phase, common for the higher temperature synthesis of QDs in organic solvents, and not the zinc blende phase of CdSe QDs common for the lower temperature water synthesis of QDs. The prepared QDs have shown the same intense emission for over a year after being synthesized.