Date of Award

2008-01-01

Degree Name

Doctor of Philosophy

Department

Material Science and Engineering

Advisor(s)

Russell R. Chianelli

Abstract

Maya Blue has been the focus of numerous studies and is believed to be a mixture of palygorskite clay and indigo dye.1,2 Several derivatives of this pigment have been developed with intriguing properties. For instance, the dye thioindigo reacts with the palygorskite clay to exhibit a broad range of colors from red to blue under UV-Vis excitation. Based on FT-Raman and computer simulation, previous work performed in our group could relate indigo and thioindigo interaction to the aluminum sites in the framework. super>3,4

The work performed with other inorganic host materials such as, layer structures and zeolites have displayed reversible acid indicator properties, similar to the ones observed in concentrated sulfuric acid. Spectroscopic analyses and computer modeling of the above mentioned interactions have been evaluated. Results obtained by these techniques showed that in dehydrated materials a disturbance of thioindigo C=O at 1655 cm-1 to lower frequencies occurs, due to the C=O---Lewis acid sites (LAS) interaction. In the presence of water, a smaller C=O shift due to C=O---HO(H)LAS was observed. Moreover, displacement of the 001 plane in some layer materials confirmed the effect of water on the color changes displayed by UV-Vis spectroscopy.

Based on these premises, it was concluded that weak electron donor-acceptor interactions took place between thioindigo functional groups (electron donors) and LAS of the aluminum silicate framework (electron acceptor). LAS (extra-framework aluminum and exchangeable cations) high hydration enthalpy made them extremely susceptible to water molecules (electron donors); generating a hydrogen bond between the two sites. The reversibility of these chromatic hybrid materials could have potential applications as water sensors and charge transfer photosensitizers in nanocrystalline TiO2-based solar cells.

1 R. J. Gettens, G.L. Stout (Eds.), Paint Materials: A short Encyclopedia. D. van

Nostrand, New York, NY, 1946.

2 L. A. Polette, Ph.D Thesis, University of Texas at El Paso, 2002.

3 F. S. Manciu, L. Reza, L. A. Polette, B. Torres and R. R. Chianelli, J.Raman

Spectrosc. 2007, 38, 1193-1198.

4 F. S. Manciu, A. Ramirez, W. Durrer, J. Govani and R. R. Chianelli, J.Raman

Spectrosc. 2008, 39(9), 1257-1261.

Language

en

Provenance

Received from ProQuest

File Size

337 pages

File Format

application/pdf

Rights Holder

Alejandra Ramirez

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