Probing the chemical reactivity of interfaces: Investigation on the interaction of dehydroindigo with Laponite by UV-vis, Raman and infrared spectroscopy

Author(s)

Bernardino, Nathalia D. ^[1] ; Constantino, Vera R. L. ^[1] ; de Faria, Dalva L. A. ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Quim Fundamental, Inst Quim, Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: VIBRATIONAL SPECTROSCOPY; v. 94, p. 83-88, JAN 2018.
• Web of Science Citations: 2

Abstract

In this work, the interaction between dehydroindigo (an intermediary oxidized form of indigo) and Laponite clay was investigated. Dehydroindigo (DHI) has been detected when indigo is adsorbed by clay minerals, but it is relatively unstable and in the presence of water it turns back into indigo. It is, therefore, important to understand the factors that extend its stability and Laponite was chosen because the small aspect ratio implies in a large amount of silanol groups (Si-OH) which would thus favor the DHI interaction through hydrogen bonding. A significant bathochromic shift (65 nm) of the DHI pi (R)pi{*} transition band in the visible region and changes in the relative intensities and position of the Raman bands at 1530,1378 and 1167 cm(-1) assigned to v(N=CC=N), delta(C=N) and v(C-N) respectively, indicate that the interaction is stronger than expected for the van der Waals and polarization forces involved in the external surfaces interactions with the siloxane groups. It was also observed that DHI presents an enhanced photochemical stability when interacting with Laponite. These results indicate that hydrogen bonding between a DHI nitrogen atom and the -Si-OH or M-OH groups is mainly responsible for the behavior present in the DHI + Lap system. (C) 2016 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 12/13119-3 - Vibrational spectroscopy in condensed phases
• Grantee: Mauro Carlos Costa Ribeiro
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 11/50318-1 - Development of compounds with pharmacological or medicinal interest and of systems for their transport, detection and recognition in biological media
• Grantee: Ana Maria da Costa Ferreira
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 12/05643-4 - Impact of nanostructural aspects on the stability of dyes and pigments of archaeological interest
• Grantee: Nathália Delboux Bernardino
• Support Opportunities: Scholarships in Brazil - Doctorate