Thesis & Dissertations

Polyoxometalate Nanostructures: A Comparative Spectrophotometric Study


Polyoxometalates (POMs), form a supreme class of inorganic compounds, and can be described as nanomolecular metal oxide clusters with manageable sizes, structures, and shapes, resulting into outstanding properties in terms of molecular and electronic structural versatility, reactivity, and relevance that make them attractive for various applications in analytical chemistry, catalysis, biology, medicine, geochemistry, materials science, and topology. Accordingly, their interesting properties will be further analyzed, studied, and comprehensively compared within their own class of compounds and with other similarly comparable inorganic metal oxygen clusters. Specifically, the spectrophotometric properties of the synthesized POMs will be investigated and compared. The study will focus on the classical type POMs, both Keggin and Wells-Dawson, and is aimed at comparing and discussing the resulting spectrophotometric data arising from Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectrophotometry (UV-Vis), techniques. Consequently, the study at hand will enable us to better understand their fascinating properties, and thereof their reactivity and uniqueness to be applied in various uses and applications. Our results show that similarities appear from the recorded FTIR and UV-Vis spectra, between compounds of the same class, by category association. Very fine displacements of peaks that occur explain the influence of heteroatoms, addenda atoms or coordinated cations. Small displacements of the bands to higher energies, to higher frequencies, are due to the polyoxometalate building flexibility, that allows cation coordination. Here we report the synthesis and Fourier Transform Infrared spectroscopy characterization as well as Ultra Violet-Visible spectrophotometrical results dealing with the different types and structures of POMs. Their chemical structures were compared and contrasted accordingly. The infrared spectroscopy revealed the existence of chemically comparable solid networks with some differences due to the nature of the POM frameworks. The UV-Vis study allowed us to better understand the bands resulting from charge transfers within the POM, also has proven for the stability of POMs which is a well-known property of POMs in solution. The entire study at hand enabled us to shed the light on the POMs’ reactivity and enhance our knowledge and broaden our scope of how they can be applied in various uses and applications.


Nour Ibrahim El Ghouch


Rami Ghassan Al-Oweini