Using SMS to Describe The Fading Mechanisms of Organic Red Dyes

When thinking about the great artists of our time, Da Vinci, Picasso, or Monet, to name a few, one comes to realize how important their contributions were to shaping the progression of our society. But as time goes on the masterpieces we cherish fade away, even under the care of the finest museums. Vibrant pigments become a dull semblance of what they once were, sometimes even changing color completely. So how can we preserve an artist’s original intent, letting their work be studied for decades to come? With chemistry.

I would like to better understand the fading mechanisms of select organic red dyes, specifically purpurin, alizarin, and their respective lake pigments. Purpurin lake is a dye that was used in historical artwork. Madder lake was a popular pigment as well, which is a combination of alizarin lake and purpurin lake. Purpurin and alizarin are very similar molecules, only separated by the absence of a single hydroxyl group.

Comparison in structure of alizarin (left) and purpurin (right)

Comparison in structure of alizarin (left) and purpurin (right)

The change in their structure, while small, is enough to cause visible and experimental differences, such as color to the naked eye and their behavior when exposed to UV/vis light. When these molecules become bonded to a mordant, such as aluminum, their behavior changes even further.

Here two alizarin molecules are bonded to an aluminum mordant. This pigment is now alizarin lake.

Here two alizarin molecules are bonded to an aluminum mordant. This pigment is now alizarin lake.

Does the presence of this mordant affect the dye fading process? The hypothesis I intend to pursue is that the addition of the hydroxyl group and/or mordant causes the molecule to undergo excited state intramolecular proton transfer (ESIPT), changing its energetic stability and the ease with which a molecule breaks down. I plan to use SMS to monitor individual pigment molecules when exposed to a laser because the results will provide structural data based on the theory of fluorescence emission.

An overarching goal of this project is to use single molecule spectroscopy to understand dye fading and eventually publish a paper describing the mechanisms by which a few historic dyes fade when exposed to light. Unveiling this process would carve the path to study as many pigments as possible and in turn allow us to suggest some potential treatments for artwork in order to preemptively minimize color-fading over the long-term. Being able to prevent the fading dyes in the first place would allow future generations to experience our culture in its full glory. This research on organic red dyes will get us one step closer to this goal.

A bit about me:

As a chemistry major and theatre minor, the integration of art and science is the backbone to my beliefs. I have always dreamed of being able to use my chemistry knowledge to advance understanding in the arts and vice versa while simultaneously inspiring young girls to become involved in STEM fields by reaching out and being a positive role model. Ideally, this dream would manifest itself in the form of a science television show; yes, I want to be the next Bill Nye the Science Guy. I am also passionate about the environment, and plan to attend graduate school to attain my Ph. D. in an field related to environmental chemistry, specifically climate change and oceanography. As I blog throughout the summer, I am going to try to tie in the connections I’m making between my research and it’s relevance, theatre, and life in general. I hope you follow me through my summer 2016 journey!