eschweizerbart_xxx Nuclear Magnetic Resonance to investigate inorganic porous materials of interest in the cultural heritage field VALERIA DI TULLIO 1 ,DONATELLA CAPITANI 1, * ,GIORGIO TROJSI 2 ,SILVIA VICINI 3 and NOEMI PROIETTI 1 1 Laboratorio di Risonanza Magnetica ‘‘Annalaura Segre’’, Istituto di Metodologie Chimiche, CNR Area della Ricerca di Roma 1, via Salaria km. 29,300, 00015 Monterotondo, Rome, Italy *Corresponding author, e-mail: donatella.capitani@cnr.it 2 Laboratorio di Diagnostica, ‘‘Suor Orsola Benincasa’’, Universita ` di Napoli, Via S. Caterina 37, 80132 Naples, Italy 3 Dipartimento di Chimica e Chimica Industriale, Universita ` di Genova, Via Dodecaneso 31, 16146 Genoa, Italy Abstract: Nuclear Magnetic Resonance (NMR) can be successfully applied to a wide number of organic, inorganic, and hybrid materials regarding cultural heritage. High-resolution solid-state NMR provides information on the structure of materials, and portable NMR devices allow non-destructive and non-invasive in situ investigation of variably sized objects. This result is possible by combining open magnets and surface radiofrequency coils to generate a sensitive volume external to the sensor and inside the object under investigation. In this paper we focus on the application of NMR to investigate inorganic porous materials such as pottery, plasters, and stones from cultural heritage sites. 27 Al MAS and 3QMAS, and 29 Si MAS high-resolution solid-state NMR along with spectral deconvolution allowed for the investigation of the chemical structure of ancient pottery. Portable unilateral NMR was used to investigate, in a non-invasive and non-destructive way, the porous structure of pottery. The effect of protective-consolidating treatments on plaster was carefully investigated by 1 H NMR depth profiles that allowed for scanning with micrometric resolution of plaster specimens. Changes occurring in the total open porosity after treatments were also evaluated. NMR diffusion measurements provided information on the restricted geometry of the porous structure of two types of biocalcar- enite and tuff. A suitable processing of collected data enabled us to define the average pore radius and pores’ interconnection in these materials. Key-words: unilateral NMR; 27 Al MAS; 29 Si MAS; porous stones; plaster; pottery; non-invasive analysis; XRD; thin section analysis; cultural heritage. 1. Introduction With the development of high-resolution solid-state tech- niques (Schmidt-Rohr & Spiess, 1994; MacKenzie & Smith, 2002), Nuclear Magnetic Resonance (NMR) has become a powerful tool to characterize organic, inorganic, and hybrid materials (Bonhomme et al., 2014). These techniques are constantly being extended to a diverse range of materials, making possible the investigation of an ever-expanding range of nuclides, including some pre- viously considered too intractable to provide useful results. Over 80 % of all nuclei have at least one NMR-active isotope, which can be investigated to obtain information in many fields of research, including solid-state chemistry, materials science, Earth science, condensed matter phy- sics, biology, and bio-inorganic molecular science. With regard to inorganic materials, solid-state NMR has been applied to the study of glasses, zeolitic framework structures, clay minerals, stones, ceramic materials, cement-based materials, pottery, guest-ion incorporation, and degree of reaction. The NMR spectroscopy is able to probe the atomic environment of the most disordered as well as the most ordered single-crystal systems. It allows for the monitoring of changes occurring in the atomic environment when materials transform from one state of structural disorder or heterogeneity to another, such as nucleation of polycrystals from glass and the formation and growth of crystalline phases when minerals react or change phase by heating or mechanical grinding. With specific reference of materials of interest for cultural heri- tage, clay and pottery may be investigated by 29 Si and 27 A1 solid-state NMR (Presciutti et al., 2005). Because the number and the amount of samples col- lected from precious artifacts must be reduced to a mini- mum, multi-analytical studies where micro-destructive, non-destructive, and possibly non-invasive techniques are 0935-1221/15/0027-2453 $ 6.30 DOI: 10.1127/ejm/2015/0027-2453 # 2015 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart Eur. J. Mineral. 2015, 27, 297–310 Published online 27 March 2015 ‘‘Characterization, diagnosis and conservation of cultural heritage’’. School held in Catania/Siracusa, 1 st to 4 th July 2014