An ab-initio approach to cultural heritage: The case of ancient paper degradation

Abstract

Paper is an important material for many applications. During the centuries, it has been the most widely used writing support and therefore paper degradation is a major issue for cultural heritage. The main component of paper is cellulose, one of the most abundant biomaterials on Earth. Cellulose oxidation is mainly responsible for the yellowing of the ancient samples, through the formation of chromophores. In order to investigate this issue and the chromophores’ role, we exploit the optical properties combining non‐destructive experiments and theoretical calculations based on ab‐initio techniques. In this paper, we illustrate the method and show its application to three ancient paper samples. The procedure we describe is a precious tool for cultural heritage preservation: indeed, the approach we present is based on non‐invasive and non‐destructive measurements that allows a microscopic understanding of cellulose‐based artifacts degradation.

Visual degradation in Leonardo da Vinci's iconic self-portrait: A nanoscale study

“…[11][12][13] For this reason, in order to interpret the results (and following on from our previous work [11][12][13] ), we modelled oxidized cellulose using eight different configurations of ketone, diketone, and aldehyde groups within the b-D-glucopyranose units (see Figs. 4-6 of Ref.…”

“…7 The white appearance of paper is due to its light scattering effect. 11,12 The yellowing seen in ancient papers is mainly due to the fact that chromophores in cellulose 13 absorb in the higher energy range of visible light (corresponding to violet and blue) and largely scatter the yellow and red portion, thereby producing the characteristic yellow-brown hue.…”

Quantitative diagnostics of ancient paper using THz time-domain spectroscopy

“…The values of v for the samples studied are reported in Table 2. Such numbers are required to calculate the absolute absorption coefficient (α) of cellulose fibers, given that THz radiation probes the volume averaged properties of the papers sheets [27,24,28,20]:…”

“…Cellulose was modeled as a crystal in its most common crystalline form (I β phase), as in Refs. [24,27,28]. Both the unit cell and the atomic coordinates of the structures were relaxed by using a densityfunctional-theory plane-wave code with ultrasoft pseudopotentials (QUANTUM ESPRESSO [33]).…”

“…Proper ultrasoft pseudopotentials [38], conveniently generated [39] to be suitable for the nonlocal VdW functionals, were used. The Irreducible Brillouin Zone has been sampled with 14 k-points [24,27,28]. Vibrational properties have been calculated using finite displacements within the DFT framework, as described in Ref.…”