Active and and monitoring materials for the environmentally safe storage and exhibition of works of art

The impact of atmospheric pollutants such as volatile organic compounds (VOCs) in corrupting and deteriorating different classes of works of art is of global concern. Indoor pollutants can be off gassed by different building materials, including items of the collection and display and storage cases. Granting the optimal environmental conditions around the art objects helps to minimize the pollutants amount in the microclimate within the storage items, eliminating the need for periodical direct interventions on the works of art. To mitigate the pollutant concentration in museum indoor environment, passive absorbers can be considered as the most suitable system to be adopted, since the number of items exposed and stored makes the use of active devices too complex and expensive. Nowadays, the substances commercially available for the removal of VOCs materials have some drawbacks that should be taken into account, such as cost, mitigation obtained purely by physisorption and poor sustainability. In this Phd research project, performed in the CNR-ISMN Research Group within the H2020 APACHE “Active & intelligent PAckaging materials and display cases as a tool for preventive conservation of Cultural Heritage” Project (GA n. 814496), chitosan-based aerogels were designed and produced to give a solid tool for VOCs mitigation in museum environments. Chitosan was used for the development of VOCs absorbers thanks to its numerous advantages, namely cost effectiveness, biocompatibility, abundance and adsorption efficiency. Different kind of aerogels were produced changing the dissolution agents, the amount of chitosan in the starting solution to be freeze dried and the fillers added to enhance the adsorption capacity and the antifungal properties. The aerogels thus produced were characterized by means of FE-SEM to study their porosity and structure. The adsorption efficiency of the aerogels towards certain pollutants was then checked by weight gain in tailored polluted environments, following a procedure of adsorption and desorption. A characterization by means of ATR-FTIR spectroscopy of the aerogels was carried out before and after their exposure to some pollutants, in order to check the chemical interaction of the chitosan and the fillers with the pollutants. The analysis of the mitigation efficacy of the aerogels continued using metal coupons as markers of the air-quality in polluted environment, in the presence of the developed aerogels. The results obtained from this research are promising, since most of the aerogels showed a good structure, a good porosity and an efficient mitigation power. As regards the tests in polluted environments, chitosan formulations were optimized and functionalised with CaCO3, since a good physisorption of the pollutants was observed (>20% after desorption) and the chemisorption by chitosan and CaCO3 of different class of pollutants was detected. Also, the mitigation of the pollutants by the aerogels observed analysing the corrosion products on the metal coupons gave clues of the efficacy of the selected system. Some of the aerogels obtained from the selected formulation are now exposed in real environments. In parallel with the study and the development of the chitosan-based aerogels, the chemical, morphological and structural properties of the sensing materials developed by the CNR-ISM and the CNR-ISMN Research Groups- within the APACHE Project - for the development of a multisensor able to detect some pollutants in museum environments were investigated during their development and after the tests in polluted environments. The analysis of the metal tracks’ surface of the sensors helped to understand the results obtained by the CNR-ISM, by means of impedance spectroscopy analysis carried out during the exposure of the sensors in tailored polluted environments. In the CNR-ISMN Research Group, the metal tracks were characterized to understand the surface modifications after exposure of the sensors in tailored polluted environments.