“This project began over a glass of wine with Eleanor Schofield, Ph.D., who is head of conservation at the Mary Rose Trust,” recalls Serena Corr, Ph.D., the project’s principal investigator. “She was working on techniques to preserve the wood hull and assorted artefacts and needed a way to direct the treatment into the wood. We had been working with functional magnetic nanomaterials for applications in imaging, and we thought we might be able to apply this technology to the Mary Rose.”The researchers present their results today at the 256th National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 10,000 presentations on a wide range of science topics.
The Mary Rose sank in 1545 off the south coast of England and remained under the seabed until she was salvaged in 1982 along with over 19,000 artefacts and pieces of timber. About 40 percent of the original structure survived. The ship and its artefacts give unique insights into Tudor seafaring and what it was like to live during that period. A state-of-the-art museum in Portsmouth, England, displays the ship’s hull and artefacts.
Once raised from the seabed, the Mary Rose was sprayed with cold water, which stopped it from drying out and prevented further microbial activity. The conservation team then sprayed the hull with different types of polyethylene glycol (PEG), a common polymer with a wide range of applications, to replace the water in the cellular structure of the wood and strengthen its outer layer.
But the ship still presented a number of challenges. While buried in the seabed, hydrogen sulphide formed by sulphur-reducing marine bacteria migrated into the wood. This reacted with iron ions from corroded fixtures like cannons to form iron sulphides. Stable in low-oxygen environments, sulphur rapidly oxidises in the presence of iron under atmospheric conditions to form destructive acids. The goal is to avoid acid production by removing the free iron ions, preventing reaction with sulphur compounds, and avoiding acid formation.
Corr and her postdoctoral fellow Esther Rani Aluri, Ph.D., and Ph.D. candidate Enrique Sanchez at the University of Glasgow (U.K.) are devising a new family of tiny magnetic nanoparticles to aid in this process in collaboration with Schofield and Rachel O’Reilly Ph.D. at the University of Birmingham. Led by Schofield, the team has employed synchrotron techniques to probe the nature of the sulphur species before turning the PEG sprays off and periodically as the ship has dried. This is the first real-time experiment that has taken an in-depth look at the evolution of oxidized sulphur and iron species. This accomplishment now informs efforts to design new targeted treatments for removal of these harmful species from the Mary Rose wood.
The next step is to use a nanocomposite based on core magnetic iron oxide nanoparticles functionalised with sequestering agents to remove harmful ions. The nanoparticles can be directly applied to the porous wood structure and guided to particular areas of the wood using external magnetic fields, a technique previously demonstrated for drug delivery. The nanocomposite will be encompassed in a heat-responsive polymer that protects the iron oxide core nanoparticles and provides a way to safely deliver the particles onto and off the wood surface. A major advantage of this approach is that it allows for the complete removal of harmful species such as free iron and sulphate ions from the wood, and these nanocomposites can be tuned by tweaking the surface functionalisation.
With this understanding, Corr notes, “Conservators will have, for the first time, a state-of-the-art quantitative and restorative method for the safe and rapid treatment of wooden artifacts. We plan to then transfer this technology to other materials recovered from the Mary Rose such as textiles and leather.”
The researchers acknowledge support and funding from the Mary Rose Trust and the Leverhulme Trust.