Synthesis and Characterization of New Inorganic Materials in Different Length Scales; from Nanometer to Micrometer

In this dissertation there are a new series of Preyssler polyoxometalate (POM) crystalline solids created using electrochemical potential. It was found that using electrochemical potential, where nucleation and reduction occur simultaneously, was a convenient method for exploratory synthesis creating new crystalline solids in aqueous solution and at room temperature. The general structure feature reveals that Preyssler POM was covalently linked by various metals from the d and f block including Co2+, Ni2+, La3+, Nd3+, Gd3+ and Ho3+ where the POM was reduced by 2 to 4 electrons. The resulting solids were crystallized from aqueous solution onto silver wires from a two–electrode set up as illustrated in Chapter 2. In Chapter 3, the case of the transition elements, the POMs were linked along the pentagonal window, a unique orientation compared to the previously reported transition metal linked Preyssler POMs from classical solid–state synthesis methods. The POMs in this configuration were linked to form 1–D column–like structures where there were no transition metals linking the parallel columns. In addition to this column–like nature when using Co2+, Ni2+ was also used and formed an isostructural complex with a minor phase that was unique due to its decoration of the Preyssler POM with Ni4O4 cubane–like units that decorated the POMs as well as space filling in between the POMs. In Chapter 4 the POMs are linked to each other by lanthanides some of which forming 2–D sheets of POMs linked by f–block elements. In Chapter 5 a different project is presented with carbon dots functionalized by TiO2 alone, a new structure type that does not involve the addition of organic passivation agents. The results were a fluorescent quantum yield of ~14% when excited at 400 nm in dimethyl formamide. The samples were characterized by spectroscopic means including UV–Vis and fluorescence spectroscopy as well as X–ray diffraction and electron microscopy. The work presented in this dissertation is significant as it explored the ability to prepare solids of different length scales using both POMs and carbon nanomaterials.