Synthesis of CdSe quantum dots using various metal salts

Abstract

Several varieties of cadmium selenide (CdSe) quantum dots (QDs) were synthesized using different metal salts (cadmium perchlorate, purified cadmium chloride, anhydrous cadmium chloride, and cadmium sulfate) and water-soluble thiols. The spectral properties (absorption and emission spectroscopy) of these QDs were similar, regardless of metal salt. Mass spectrometry was performed on each to determine the molecular weight of the QDs. The mass spectral data obtained were not conclusive. Since the QD solution has a pH of ~11, we believe that the QDs are multiply charged because of the carboxylate groups of the water-soluble thiols surrounding the semiconducting core Because of the charges on the QDs, the molecular weight is difficult to determine. The pH of each QD solution was then adjusted to values near the pKa of the water-soluble thiols to reduce the amount of charge surrounding the QD cores. These pH-adjusted solutions were subsequently analyzed using spectroscopic techniques, including mass spectrometry.