Nanomaterials based on cerium (IV) oxide, CeO2, have been investigated due to the readily available Ce3+/Ce4+ transition which allows antioxidant and enzyme mimetic behavior. The addition of trivalent Eu3+ to such structures may provide fluorescence and increase oxygen vacancies, oxygen mobility, and radical scavenging capabilities. Eumelanin is a complex dark brown pigment originating from the oxidation and oligomerization of tyrosine, or synthesized through the auto-oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA). Eumelanin has numerous potential applications due to its strong UV-VIS absorption, radical scavenging ability, and possible activity against Parkinson’s and Alzheimer’s associated amyloids. Fluorescent and non-fluorescent Eu-doped CeO2 rods, cubes, and wires have been synthesized using hydrothermal, electrospinning, and annealing techniques. The products have been characterized using TEM, EDX, XRD, and steady state fluorimetry. Experimental parameters providing dimensional and compositional control have been determined. The presence of CeO2 or Eu-CeO2 nanomaterials in L-DOPA-containing solutions suppresses the eumelanin-associated fluorescence intensity by up to 80%. The nanorods and nanocubes change from pale yellow to black or grey, while nanowires show no color change. The extent of color change corresponds to fluorescence suppression and changes in the UV-VIS absorption. This suggests deposition of eumelanin-associated species on the surface of the Eu-CeO2 nanomaterials. Various experimental parameters such as temperature, pH, and concentration have been analyzed for effects on the evolution of eumelanin in presence of the nanomaterials, and will be presented here. The antibacterial and radical scavenging activity of the above synthesized nanomaterials and Eu-CeO2:eumelanin composites will also be described.

Europium-doped cerium oxide nanomaterials: Synthesis and exposure to l-dopa and eumelanin

255th National Meeting (2018)

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