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DOPING CdSe QUANTUM DOTS WITH VANADIUM(II) Quantum dots have optical properties that are based upon their size. By controlling the size of the quantum dots one can control their optical properties. Doping the nano particles with different metal clusters not only enhances the optical properties of the quantum dot but can also add magnetic properties to the material as well. During the summer I doped CdSe quantum dots with V(II). Vanadium was used because it has a tetrahedral configuration and contains three d orbital electrons. Because the energy gap between the orbitals is small there is more of a chance that and electron could move between the levels, which promotes the idea that the material would act like a switch and could be used for memory. In order to make CdSe quantum dots I had to first make the precursor cluster, Li2[Cd4(SPh)10], which was then combined with selenium to form Li4[Se4Cd10(SPh)16]. The Li4[Se4Cd10(SPh)16] was then placed into melted hexadecylamine (HDA) and heated. The HDA served to passivate the surface of the CdSe so that the product did not become a bulk material. To ensure that the proper size nano particle was obtained, absorptions had to be taken. Since the optical properties of quantum dots are based on their size one can take absorbances of the quantum dots during their growth to determine how large they have become. The CdSe quantum dots that I worked with absorbed at about six hundred nanometers. The CdSe was to be used as a reference to compare with the vanadium doped CdSe. The V(II) doped CdSe was achieved by combining Li4[Se4Cd10(SPh)16] with different amounts of vanadium(II)chloride and then heated in the presence of HDA. Absorbances were again taken so that a uniform absorption of six hundred nanometers could be obtained. Multiple samples of the same size CdSe quantum dot were obtained, each with different concentrations of vanadium. X-ray diffraction was used to determine if the CdSe had actually been doped or if the vanadium was only on the surface of the particle.
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