University of Texas at El Paso DigitalCommons@UTEP Open Access Theses & Dissertations 2008-01-01 Optical And Vibrational Spectroscopic Studies Of Synthetic Maya Pigments As A Function Of Swati Kumar University of Texas at El Paso, [email protected] Follow this and additional works at: https://digitalcommons.utep.edu/open_etd Part of the Inorganic Chemistry Commons, and the Organic Chemistry Commons Recommended Citation Kumar, Swati, "Optical And Vibrational Spectroscopic Studies Of Synthetic Maya Pigments As A Function Of" (2008). Open Access Theses & Dissertations. 296. https://digitalcommons.utep.edu/open_etd/296 This is brought to you for free and open access by DigitalCommons@UTEP. It has been accepted for inclusion in Open Access Theses & Dissertations by an authorized administrator of DigitalCommons@UTEP. For more information, please contact [email protected]. OPTICAL AND VIBRATIONAL SPECTROSCOPIC STUDIES OF SYNTHETIC MAYA PIGMENTS AS A FUNCTION OF CONCENTRATION OF INDIGOID DYES SWATI KUMAR Department of Chemistry APPROVED: ___________________________ Russell R. Chianelli, Ph.D., Chair ___________________________ Felicia Manciu, Ph.D. ___________________________ Wen-Yee Lee, Ph.D. ___________________________ Lori A. Polette-Niewold, Ph.D. __________________________ Patricia D. Witherspoon, Ph.D. Dean of the Graduate school © The University of Texas at El Paso, El Paso, Tx, USA, 2008 All rights reserved. Dedicated to My Loving Parents OPTICAL AND VIBRATIONAL SPECTROSCOPIC STUDIES OF SYNTHETIC MAYA PIGMENTS AS A FUNCTION OF CONCENTRATION OF INDIGOID DYES By SWATI KUMAR THESIS Presented to the Faculty of the Graduate School of The University of Texas at El Paso in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Department of Chemistry THE UNIVERSITY OF TEXAS AT EL PASO, EL PASO December 2008 ACKNOWLEDGMENTS First of all, I would graciously like to thank Prof. Russell R. Chianelli, who gave me an opportunity to learn new things and taught me to take up new challenges in the studies and also for providing the necessary facilities for carrying out present research work. I also want to thank Dr. Lori Polette for her valuable guidance, constant encouragement, keen interest and affectionate attitude during the course of this work. I gratefully acknowledge Dr. Felicia Manciu, for her tireless efforts and help in solving problems regarding spectroscopic data. I am deeply obliged to Prof. Keith H. Pannell, Professor, Department of Chemistry, for his well wishes and suggestions. I also would like to convey my special thanks to Prof. R. N. Kapoor and Dr. Hemant K. Sharma for their valuable suggestions and timely help. I would like to express my thanks to MRTI specially Alejandra Ramirez for her assistance, support and valuable discussion during my research work . Finally I wish to express my deepest gratitude to my parents, and friends for all they have done for me. The love, the inspiration, the care and the support that they have given me has been too overwhelming. I want to also say a special thank to my husband Mukesh Kumar, one of the most important and influential person in my life, who always inspired me to achieve my goal, I want to thank him for all his unconditional academic and emotional support. v ABSTRACT Pigments developed by the Mayan civilization around 8th century, represent some of the most versatile pigments known to date. Several derivatives of these pigments are popular subjects of current research interest. This is due to the characteristic stability which is provided by a bonding mechanism between the dye and the clay. One such pigment “Maya Blue”, a mixture of Indigo and Palygorskite, provides a dramatic background for murals and ceramics throughout Mesoamerica. Several research groups have devoted time and interest in unlocking its particular features. 1-3 The work embodied in this thesis is focused on the synthesis and characterization of three pigments: Maya Blue, Maya Purple and Royal Blue with varying concentrations (1-25%) of the organic dyes. Samples were prepared by heating the corresponding dye with Palygorskite (Inorganic clay) at 170 °C for 9 hours. Various factors which account for the stability of these complexes are discussed by a critical analysis of the results obtained. Ultra Violet-Visible (UV-Vis) spectra of Maya Blue, Maya Purple and Royal Blue samples provide an evidence for variations in the electronic structure of the dyes after they have incorporated into the Palygorskite matrix. This is suggested by a bathochromic shift of π→π* transition associated with dyes [ λmax (Indigo) = 584 nm, λmax (Maya Blue 6%) = 656 nm; λmax (Thioindigo) = 507 nm, λmax (Maya Purple 6%) = 590 nm]. In contrast, upon increasing the concentrations of the dye in the pigment, the absorption maxima shift to a lower wavelength which is suggestive of partial contribution of the dye at higher concentrations. vi Analysis of Fourier Transform Infrared (FTIR) spectra provides a qualitative bonding description of the C=O, N-H, C=C, O-H and Si-O-X (where X = H, Al, Si) groups. The stretching band due to C=O group shifts to at lower wavenumber after the pigments formation [( νC=O, cm-1) = 1626 (Indigo), 1622 (Maya Blue), 1655 (Thioindigo), 1627 (Maya Purple)]. The νN-H band disappeared at lower concentrations of the dye in the Maya Blue samples. These data support the involvement of such groups in bonding during the pigment formation. On the contrary, the bands due to C=O, N-H groups become more sharp at higher concentrations of the dye. In a linear argument, the appearance of sharp bands of the C=O group suggests an excess of Indigo and Thioindigo dyes. Fourier Transform Raman (FT Raman) spectroscopic, Powder X-ray diffraction (XRD), and Differential Scanning Calorimetric (DSC) studies further provide evidences to develop the binding mechanism of the dye and the clay. Based on all the results, it is envisaged that, at lower concentrations of the dye (<6%), the dye molecules may penetrate into the channels of clay while on increasing the concentrations (>6% - <16%), the dye molecules bind with the exposed surface involving Si-O-Mn+ (M = Al, Fe) sites. At much higher concentrations (>16%) of the dye, the surfacial activity predominates and the dye accumulates in the form of layers on the outer surface of the clay. vii TABLE OF CONTENTS Page ACKNOWLEDGEMENTS……………………………………………………………………...v ABSTRACT……………………………………………………………………………………...vi TABLE OF CONTENTS………………………………………………………………………viii LIST OF TABLES…………………………………………………………………………….....x LIST OF FIGURES…………………………………………………………………………......xi STATEMENT OF PROBLEM………………………………………………………………...xvi RESEARCH OBJECTIVES…………………………………………………………………..xvi JUSTIFICATION OF WORK…………………………………………………………………xvii Chapter 1. INTRODUCTION……………………………………………………………………………..1 2. MATERIAL SAMPLING AND CHARCTERIZATION TECHNIQUES………………….16 2.1 Material Sampling………………………………………………………………………16 2.2 Sample Preparation……………………………………………………………………16 2.3 Characterization Techniques………………………………………………………….16 3. RESULTS AND DISCUSSION……………………………………………………………19 3.1. Color Change…………………………………………………………………………19 3.2 UV-Vis Spectroscopy……………………………………………………………........22 3.2.1 Indigo/ Palygorskite complex: Maya Blue………………………………………...22 3.2.2 Thioindigo/ Palygorskite complex: Maya Purple…………………………………28 viii 3.3 FTIR Spectroscopy……………………………………………………………………32 3.3.1 Palygorskite FTIR …………………………………………………………………...32 3.3.2 Indigo FTIR…………………………………………………………………………..37 3.3.3 Thioindigo FTIR……………………………………………………………………..38 3.3.4 FTIR Studies of Maya Blue………………………………………………………...40 3.3.4.1 Vibrational Modes Associated with Palygorskite………………………………41 3.3.4.2 Vibrational Modes Associated with Indigo……………………………………..46 3.3.4.3 Concentration Change in Maya Blue …………………………………………...50 3.3.5 FTIR Studies of Maya Purple………………………………………………………53 3.3.5.1 Vibrational Modes Associated with Palygorskite………………………………55 3.3.5.2 Vibrational Modes Associated with Thioindigo………………………………...58 3.3.5.3 Concentration Change in Maya Purple………………………………………...59 3.4 FT Raman Study of Maya Blue……………………………………………………...62 3.5 Chemical Analysis of Palygorskite…………………………………………………..64 3.6 X-Ray Diffraction Study of Maya Blue and Maya Purple………………………….66 3.7 Royal Blue……………………………………………………………………………..69 3.8 Differential Scanning Calorimetry Studies………………………………………….73 3.9 Discussion and Conclusions…………………………………………………………78 REFERENCES………………………………………………………………………………..84 APPENDIX………………………………………………………………………………….....90 CURRICULUM VITA………………………………………………………………………….93 ix LIST OF TABLES Table 1 . Absorption intensities of Indigo and Maya Blue heated at 170 oC/9h………….27 Table 2. Absorption intensities of Indigo and Maya Purple heated at 170 oC/9h……….31 Table 3 . Frequencies and IR modes of Palygorskite………….......................................36 Table 4 . Frequencies and IR modes of Indigo……………………………………………..38 Table 5. Frequencies and IR modes of Thioindigo………………………………………..39 Table 6 . IR frequencies for water modes in Maya Blue (6%) heated at 170 °C/9h….....46 Table 7 . IR frequencies for carbonyl modes and N-H modes……………………………49 Table 8 . IR frequencies for carbonyl modes and N-H modes in Maya Blue (1-25%) heated at 170 °C/9h…………………………………………………………....53 Table 9 . IR frequencies for water modes in Maya Purple (6%) heated at 170 oC/9h......57 Table 10 . IR frequencies for carbonyl modes in Maya Purple……………………………59 Table 11 . IR frequencies for carbonyl modes in Maya Purple (1-25%) heated at 170 °C/9h……………………………………………………………………………………..61 Table 12 . WD-XRF chemical analysis……………………………………………………....65