Time resolved resonance Raman Spectroscopy of dyes in confined environments

• Grant number: 13/25900-4
• Support type: Scholarships abroad - Research Internship - Doctorate
• Effective date (Start): March 03, 2014
• Effective date (End): August 02, 2014
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal researcher: Dalva Lucia Araujo de Faria
• Grantee: Nathália Delboux Bernardino
• Supervisor abroad: Terry L. Gustafson
• Home Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Research place: Ohio State University, Columbus, United States
• Associated to the scholarship: 12/05643-4 - Impact of nanostructural aspects on the stability of dyes and pigments of archaeological interest, BP.DR

Abstract

It is well recognized that inorganic matrices can promote chemical stabilization of organic compounds and the Maya Blue is probably the best known example. Although this system has been the object of several investigations, some questions concerning the dye structure inside the clay nanopores are yet to be answered. The main objective of this investigation is to enlarge our understanding of the structure and vibrational and electronic energy level of indigo, alizarin and ²-carotene dyes intercalated into inorganic matrices, such as palygorskite, montmorillonite and layered double hydroxide (LDH). A comparative study of the same dyes adsorbed on the external surfaces of the clay will also be performed. Such informations can contribute to clarify the reasons for the enhanced chemical stability of such dyes when interacting with the clays. Time resolved spectroscopic techniques are able to probe molecular excited states and other dynamic processes, using dephased pulsed radiation (lasers) to pump and probe these states. Time resolution in such experiments depends on the experimental setup and can reach the 10-15 s range. For probing electronic excited states generally nano or picoseconds time resolution is enough to bring most of the desired information. Thus, TR3 is a technique tailored to characterize excited conformations and energies and it is thus expected that it can shine light on the indigo chemical stability when intercalated in palygorskite, thus allowing the identification of the aspects that contribute to the observed spectral features. TR3 experiments will be carried out in the Ohio State University in collaboration with Professor Terry Gustafson. From the comparison of the indigo/clay and pure dye TR3 spectrum it is expected to a better understanding on how the excited electronic and vibrational levels are affected by intercalation and by the matrix properties. From such data a confirmation the current explanations for the indigo chemical stability is expected to be achieved or ruled out, with the TR3 results being able to provide support for a new and more reliable explanation. Considering that the dye/clay system is not soluble, dispersions in different solvents will be tested and used is a flow system. The results will be analyzed aiming at to find a correlation between the confined dye structure and the vibrational assignment of the bands obtained for the dye/clay system. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

BERNARDINO, N. D.; BROWN-XU, S.; GUSTAFSON, T. L.; DE FARIA, D. L. A. Time-Resolved Spectroscopy of Indigo and of a Maya Blue Simulant. Journal of Physical Chemistry C, v. 120, n. 38, p. 21905-21914, SEP 29 2016. Web of Science Citations: 8.