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2D Materials/Polyoxometalate Hybrids for Heritage Conservation

Periodic Reporting for period 1 - HeriCare (2D Materials/Polyoxometalate Hybrids for Heritage Conservation)

Reporting period: 2019-10-16 to 2021-10-15

Cultural heritage is the envelope of our lives and societies, acting as an invisible thread that links people, history and identity. Becoming more aware of its value, and in order to share and promote the understanding of our roots and appreciate our diversity, public administrations and private institutions have devoted increasing attention to the importance of preserving our shared cultural heritage. Unfortunately, due to their deteriorating condition, only a few prominent examples of tangible cultural heritage have lasted through to the present day. The main factors involved in the deterioration of heritage objects include environmental (exposure to light, humidity, acidic gases), microbial (bacterial or fungal) and human action (from intentional or accidental damage to intervention). Hence, the preservation of the past and future heritage is of key importance for European institutions and society as a whole, not only due to social and cultural importance, but also because of the economic implications arising from tourism, research and art. The HeriCare project comprises the development of effective nanomaterials as transparent, highly-active protective coatings for cultural heritage objects to prevent the bio- and environmental degradation of soft organic materials such as photographic films or paper. The main goal of this project was to develop transparent coatings based on nanomaterials which possess high antimicrobial activity. HeriCare project was developed by Dr. Andrés Seral-Ascaso, with the PI Prof. Jesús Martínez de la Fuente at Instituto de Nanociencia y Materiales de Aragón (INMA), a joint research center of CSIC & University of Zaragoza.
During implementation of the project, both 1-dimensional materials (silver nanowires) and hybrids of 2-dimensional materials with polyoxometalates were studied as antimicrobial agents to protect cultural heritage items. Among them, the silver nanowires resulted in the more active materials, due to their ability to create quasi-transparent, homogeneous coatings with high antimicrobial properties.
The antimicrobial assays were performed on non-pathogenic microorganisms, including the bacteria B. Subtilis and B. Megaterium and the fungi A. Niger. These microorganisms are capable of quickly degrading the photographic films under humid conditions. In contrast with the quick growth of the microorganisms and degradation of the pristine photographic film, those protected with a thin coating of silver nanowires showed a reduction greater than 99.5 % in the number of viable, culturable bacteria, and the fungi did not grow even after 14 days in humid conditions (Relative humidity >98%).
The implementation of the project included the training of the researcher on the synthesis and characterization of nanomaterials and on microbiological cultures and the performance of antimicrobial assays.
Exploitation and dissemination: the project did not produce results suitable for copyright or patenting. As a result of the action, a review article summarizing the state of the art of the use of nanomaterials as antimicrobials in the field of Heritage conservation has been published in the journal Chem (Cell Press, Elsevier), and a manuscript describing the use of silver nanowires as protective antimicrobial layer of photographic films is in preparation. The results have been presented at the E-MRS Spring meeting 2021 and the IBBS conference 2021.
The project has brought the attention of the research community to the opportunity of developing antimicrobial treatments based on nanomaterials to preserve our photographic and cinematographic heritage. Photographic films from the 19th and 20th century contains highly valuable historic, artistic and social information and images, which must be physically preserved for future generations. The HeriCare project has developed a quasi-transparent coating of silver nanowires to succesfully protect colour negatives from the biodeterioration caused by the bacteria B. subtilis and B. megaterium and the fungi A. niger. Within the framework of this project, a Summer University Course was organized, entitled “New perspectives on the application of nanomaterials in Heritage Conservation and Restoration”, as a highly specialized, formative activity. Beyond the scientific achievements, the outreach the project NanoRural has brought the latest advances in nanoscience and technology to tens of villages of less than 500 inhabitants in rural areas of Aragón, contributing to create awareness about the importance of science to sort the social challenges and also to create awareness about the need to bring science to all corners of every country.

Image foot: H: Liquid crystal demonstrator used in NanoRural. E: Course “New perspectives on the application of nanomaterials in Heritage Conservation and Restoration” organised in Albarracín (Teruel). R: C3N4 flakes under the electronic microscope (false coloured). I: Resazurin assay with POMs. C: Science dissemination in a rural school. A: colour photographic film. R: undeveloped fungi spore on silver-treated colour negatives, under electron microscope (false coloured). E: NanoRural science dissemination in Lecina, under the European Tree of the year 2021 :)
Summary of the activities & research of the project