Date of Award

Spring 4-21-2017

Track

Chemistry

Degree Type

Thesis

Degree Name

Master of Science in Chemical Sciences (MSCB)

Department

Chemistry

Committee Chair

Dr. Bharat Baruah

Committee Member

Dr. Janet Shaw

Committee Member

Dr. Heather Abbott-Lyon

Abstract

Materials composed of titanium (IV) oxide (TiO2) have received enormous scientific interest due to titania’s abundance, non-toxicity, and photocatalytic proficiency, however its large band gap limits its applicability under ambient conditions. Various attempts have been made to incorporate titania into composite systems to sensitize it for activity under a broader range of wavelengths. One such method includes utilizing narrow band gap semiconductors to form an electron transfer process analogous to photosynthesis referred to as a Z-scheme. Z-scheme systems can catalyze the decomposition of aqueous pollutants via generation of reactive oxygen species after input of sunlight. This work reports the design of a photocatalyst consisting of macroporous inverse opal (io) TiO2 embedded with gold nanoparticles (AuNPs) and cadmium sulfide quantum dots (CdS QDs) into binary and ternary systems. These composites, labeled ioTiO2-Au, ioTiO2-CdS, and ioTiO2-Au-CdS are characterized via SEM, EDX, solid-state UV-vis, and Raman, and are subsequently evaluated for their photocatalytic efficiency against the pollutant analog trypan blue (TryB) under UV and white light LED lighting conditions. It was found that binary ioTiO2-CdS exhibits the best photocatalytic performance, with a rate constant 7.8, 5.2, 6.5, and 1.6 times faster than singular ioTiO2 and CdS, binary ioTiO2-Au, and ternary ioTiO2-Au-CdS under UV, respectively. Under white light LED all systems exhibit reduced activity, with ioTiO2-Au-CdS and ioTiO2-CdS showing no statistical difference, however, the ternary system performed most consistently across both light sources, retaining 92% of its UV performance. Loss of CdS due to photocorrosion limits recyclability of the thin films.

Comments

Thin film inverse opal (io) TiO2 photocatalysts were designed on glass slides and embedded with Au nanoparticles and/or CdS quantum dots to build binary and ternary systems. The films were extensively characterized by SEM, EDX, raman, and other spectroscopic methods, and were used for degrading an organic pollutant analogue tryapan blue in water under UV and visible lighting conditions. The binary ioTiO2-CdS system showed the best activity under UV light after 120 minutes followed by the ternary ioTiO2-Au-CdS system. Both systems were found to have comparable activities under visible light however the ternary system showed the most consistency across both light sources. The binary and ternary systems demonstrated enhanced activity over the combined activity of their constituent parts working simultaneously but independently, indicating a synergistic affect when these materials are assembled into composite materials.

Available for download on Saturday, May 05, 2018

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