Newly Developed Nano-Calcium Carbonate and Nano-Calcium Propanoate for the Deacidification of Library and Archival Materials
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Hindawi Journal of Analytical Methods in Chemistry Volume 2017, Article ID 2372789, 8 pages https://doi.org/10.1155/2017/2372789 Research Article Newly Developed Nano-Calcium Carbonate and Nano-Calcium Propanoate for the Deacidification of Library and Archival Materials Marina Bicchieri,1 Federica Valentini,2,3 Andrea Calcaterra,3 and Maurizio Talamo3 1Chemistry Department, Istituto Centrale Restauro e Conservazione Patrimonio Archivistico e Librario, Via Milano 76, 00184 Roma, Italy 2Department of Chemistry, Università Tor Vergata, Via della Ricerca Scienti*ca 1, 00133 Roma, Italy 3INUIT Università Tor Vergata, Via dell’Archiginnasio snc, 00133 Roma, Italy Correspondence should be addressed to Marina Bicchieri; [email protected] Received 11 August 2017; Accepted 5 November 2017; Published 26 December 2017 Academic Editor: Jaroon Jakmunee Copyright © 2017 Marina Bicchieri et al. 'is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Paper-based cultural heritage objects are subject to natural deterioration due to internal and external factors, that is, the presence of heavy metals, incorrect conservation, humidity, exposure of the artifacts to pollutants, light, and high temperatures. To contrast the decay of the original objects, it is necessary to study and apply innovative speci1c techniques, set up novel preservation methodologies, and implement or synthesize new products. As the nanomaterial science 1eld developed over the last decades, the usage of nanomaterials in cultural heritage gained a prominent role. Such an excitement for the novel materials opened the path for an uncontrolled transfer of nanoparticles developed for di5erent applications to paper restoration, neglecting all their possible interactions with the support or the graphic media. 'e aim of this work was to synthesize new nanomaterials expressly conceived for the treatment of library materials. To evaluate their possible insertion in the o6cial conservation treatments that are subjected to validation by Istituto Centrale Restauro e Conservazione Patrimonio Archivistico e Librario, the new nanomaterials were tested both on laboratory paper samples and on original documents. 'is work presents the results of these studies (some of which still preliminary) stressing the positive and extremely promising outcomes of this research. 1. Introduction constitute the “real” objects. For these reasons, the techniques to be used should be carefully chosen, and the data collected Characterization of manuscripts, books, and graphic works with di5erent techniques must be correctly interpreted to is challenging due to the complexity of the possible in- permit the choice of the conservation/restoration method or teractions among all of the materials constituting the real product to be applied to each artifact. objects: paper support, inks, dyes, sizes, and adhesives, not to It is well known that oxidation and hydrolysis are the main mention the materials used for the bookbinding. degradation patterns that can occur in paper. Oxidation leads Each original object is unique, and no routine methods to the loss of paper strength and to its yellowing (by formation can be used to analyze them. It is necessary to study and of carbonyl conjugated double bonds, CC double bonds, in interpret all of the possible interactions between the com- the cellulosic network), to the acidi1cation of the paper (by ponents of the cultural heritage object and their degradation formation of carboxyl groups), while hydrolysis induces the patterns. Even though single speci1c problems related to the breaking of the chain, and the paper becomes fragile [1, 2]. deterioration of the documents have been investigated and at Because of the speci1city of the restoration treatments, it times theoretically modeled for “ideal” objects, ideal materials, is really important to be able to distinguish the kind of with single and well-de1ned degradation pattern, do not degradation occurred in the paper. 2 Journal of Analytical Methods in Chemistry In a previous study [3], we investigated, by means of Raman spectroscopy, di5erently degraded papers to identify the degradation products. Simply hydrolyzed papers, in which no modi1cation of the chemical structure of the cellulose occurred, were undistinguishable from the well- conserved papers. On the contrary, oxidized papers, in which the oxidation caused chemical and structural varia- tions in the cellulose macromolecule, showed signi1cant di5erences in particular in the range below 1800 cm−1. It is known that the Raman intensity of some peaks depends on the orientation of the sample, with respect to the polarization of the exciting beam. Polarization analysis performed in Raman spectroscopy highlighted that several characteristic Raman intensity-stacked spectra bands of the cellulose showed variations in intensity, as a function of the orientation of the 1bers, but a quite broad peak at about 1577 cm−1 was always present in the oxidized 200 400 600 800 1000 1200 1400 1600 samples and did not change in intensity with 1ber orien- −1 tation and rotation, making this band a good “marker” of the Raman shi (cm ) oxidation process. Figure −1 1: Raman spectra (excitation line λ 785 nm) of papers, It is to underline that in the region around 1600 cm , showing three possible degradations occurring in the cellulose chain. di5erent group vibrations overlap: for the oxycellulose, CC 'e characteristic peaks are marked with arrows. Blue line: formation symmetric stretching, CC–O symmetric stretching, and of carboxylic groups (636 cm−1 OC–O i.p. deformation; 1444 cm−1 O–CO asymmetric stretching. 'e presence of other bands OC–O sym. stretching; 1577 cm−1 OC–O asym. stretching). Red permits to understand and con1rm the formation of speci1c line: formation of carbon-carbon double bonds (634 cm−1 CC–H functional groups (634 cm−1 for CC–H wagging; 636 cm−1 wagging; 1577 cm−1 CC–O stretching). Black line: formation of −1 for OC–O in plane deformation; 716 cm−1 for C–O–C a 1ve-member cyclic ether (716 C–O sym. stretching; 1079 cm C–O symmetric stretching of a 1ve-member ether; 1079 cm−1 for asym. stretching). 'e ether is formed after oxidative breaking of C–O–C asymmetric stretching of a 1ve-member ether; C2–C3 bond in the anhydroglucose ring and subsequent rearrange- ment with formation of an ether linkage between C3 and C6 [2]. 1444 cm−1 for OC–O symmetric stretching; and 1577 cm−1 for OC–O asymmetric stretching and CC symmetric stretching), Figure 1. For cleaning, mending, and reinforcement of paper, many After detecting the kind of degradation su5ered by the products have been tested—natural or arti1cial macromole- paper [4], the correct treatment and the most adequate solvent cules or synthetic polymers [11, 12]. to be applied can be chosen. In the last years, some nanomaterials developed for di5erent 'e problems related to the oxidation of cellulose and applications [13] have been “transferred” to paper restoration, the methods of intervention on real artifacts have been without considering the possible negative interactions. discussed elsewhere [5–8] and will not be discussed here. 'e 'e aim of this work was to synthesize new nano- products studied and their application to library and archival materials expressly conceived for the reinforcement and materials have been inserted in the o6cial methods of the deacidi1cation treatment of books, archival documents, and Italian Ministero dei Beni e delle Attivita` Culturali e del graphic works of art, to verify their behavior after appli- Turismo [9]. cation to laboratory paper samples and original documents, To solve the problems related to the acidi1cation of the and to evaluate their possible application in the o6cial support, deacidi*cation treatments are applied [10]. conservation treatments that are subjected to validation by 'e so-called deacidi*cation of paper materials consists the Istituto Centrale Restauro e Conservazione Patrimonio in the neutralization of the acidic groups, that is, the car- Archivistico e Librario. boxylic functions, by formation of water-insoluble salts. Historically, calcium carbonate has been widely used for 2. Materials and Methods deacidi1cation, but this compound presents some disad- vantages: it is insoluble in water (bubbling of carbon dioxide 2.1. Materials. 'e synthesis of CaCO3 nanoparticles is in water solution is needed to obtain the dissolution) and in reported in a previous work [14], while the synthesis of other organic solvents; it is only possible to obtain solutions calcium propanoate nanoparticles is under patent as well as at low concentration (0.3 g·L−1) and the solution should be the new analytical fabrication of the innovative graphene freshly prepared to avoid reprecipitation of the salt; long sheets. time of immersion is needed to obtain a satisfactory de- All the reagents (Sigma-Aldrich) were of analytical grade acidi1cation; moreover, aqueous treatments are not always and used as received. A Milli-Q water system was used to compatible with the graphic media. 'e calcium salt is produce ultrapure water and all daily solutions. applied in excess and not in stoichiometric amount in order For the laboratory samples, Whatman CHR-1 chro- both to neutralize the acidic functions present in the paper matography paper (Sigma-Aldrich) was used. 'e paper had and to deliver calcium, if new acidic functions are formed. been then sized with cationic modi1ed oat starch Cerestar Journal of Analytical Methods in Chemistry 3 C∗05702, 10% w/v in water. Some samples were acidi1ed by exposure to vapors of concentrated hydrochloric acid (37%; Sigma-Aldrich) for 15 minutes. 'ese samples were used both for destructive and nondestructive analyses. 'e original paper samples belonged to “Archivio di Casa Conti-Anni 1750–1789,” no more subjected to the survey by the Italian Ministero dei Beni e delle Attivita` Culturali e del Turismo. 'e papers, sized with gelatin, had been manu- factured by using 100% Max 1bers and the texts written with iron-gall ink.