Theoretical optical spectroscopy of complex systems

Conte, Adriano Mosca; Violante, C.; Missori, Mauro; Bechstedt, F.; Teodonio, Lorenzo; Ippoliti, Emiliano; Carloni, Paolo; Guidoni, Leonardo; Pulci, Olivia

doi:10.1016/j.elspec.2013.02.002

Cited by 7 publications

(6 citation statements)

References 73 publications

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“…This approach is possible because of the direct proportionality between the intensity of the optical absorption spectra calculated below 4.96 eV and the concentration of oxidized groups. Thanks to this proportionality, demonstrated by several tests [8,20,21], we could perform calculations with one oxidized group per unitary cell. In fact, the optical spectra obtained by reducing the level of oxidation (considering one oxidized group every two and four cells) gives spectra with the same shape.…”

Section: Theoretical Analysismentioning

confidence: 91%

“…Theoretical spectra of aged cellulose are calculated following Refs. [8,20,21], as linear combinations of these spectra computed with one oxidized group per cell:…”

Section: Theoretical Analysismentioning

confidence: 99%

“…In order to evaluate the number of moles of oxidized groups per gram of cellulose, we used the property observed in Refs. [8,20,21] that the intensity of the experimental optical absorption α(λ) is proportional to the number of oxidized groups N ox/mole contained in a mole of cellulose: α(λ) = α 0 (λ) N ox/mole , where α 0 (λ) is the absorption of a sample with only one oxidized group per mole of cellulose. Theoretical absorption spectra can be normalized in such a way to obtain spectra of virtual cellulose samples with one oxidized group per cell, and that contain therefore an Avogadro number (N A ) of oxidized groups per mole of cellulose: α(λ) theor norm = α 0 (λ) N A .…”

Section: Theoretical Analysismentioning

confidence: 99%

“…Pristine cellulose does not absorb light above about 200 nm (below 6 eV) [8,18]. The yellow color seen in aged papers is mainly due to the fact that chromophores in paper absorb the higher energy band of visible light (corresponding to violet and blue) and largely scatter the yellow and red portion, thereby producing the characteristic yellow-brown hue [8,15,20,21].…”

Section: Introductionmentioning

confidence: 99%

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Optical response of strongly absorbing inhomogeneous materials: Application to paper degradation

et al. 2014

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In this paper, we present a new noninvasive and nondestructive approach to recover scattering and absorption coefficients from reflectance measurements of highly absorbing and optically inhomogeneous media. Our approach is based on the Yang and Miklavcic theoretical model of light propagation through turbid media, which is a generalization of the Kubelka-Munk theory, extended to accommodate optically thick samples. We show its applications to paper, a material primarily composed of a web of fibers of cellulose, whose optical properties are strongly governed by light scattering effects. Samples studied were ancient and industrial paper sheets, aged in different conditions and highly absorbing in the ultraviolet region. The recovered experimental absorptions of cellulose fibers have been compared to theoretical ab initio quantum-mechanical computational simulations carried out within time-dependent density functional theory. In this way, for each sample, we evaluate the absolute concentration of different kinds of oxidized groups formed upon aging and acting as chromophores causing paper discoloration. We found that the relative concentration of different chromophores in cellulose fibers depends on the aging temperature endured by samples. This clearly indicates that the oxidation of cellulose follows temperature-dependent reaction pathways. Our approach has a wide range of applications for cellulose-based materials, like paper, textiles, and other manufactured products of great industrial and cultural interest, and can potentially be extended to other strongly absorbing inhomogeneous materials

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Section: Theoretical Analysismentioning

confidence: 91%

“…Theoretical spectra of aged cellulose are calculated following Refs. [8,20,21], as linear combinations of these spectra computed with one oxidized group per cell:…”

Section: Theoretical Analysismentioning

confidence: 99%

Section: Theoretical Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical response of strongly absorbing inhomogeneous materials: Application to paper degradation

et al. 2014

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“…2(b)). The linear combination coefficients obtained give an estimation of the concentration of chromophores inside aged paper, 20,21 and make it possible to obtain chemical information on the self-portrait by entirely non-destructive and non-invasive optical measurements.…”

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confidence: 99%

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

Conte

Pulci

Misiti

et al. 2014

Applied Physics Letters

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The discoloration of ancient paper, due to the development of oxidized groups acting as chromophores in its chief component, cellulose, is responsible for severe visual degradation in ancient artifacts. By adopting a non-destructive approach based on the combination of optical reflectance measurements and time-dependent density functional theory ab-initio calculations, we describe and quantify the chromophores affecting Leonardo da Vinci's iconic self-portrait. Their relative concentrations are very similar to those measured in modern and ancient samples aged in humid environments. This analysis quantifies the present level of optical degradation of the Leonardo da Vinci's self-portrait which, compared with future measurements, will assess its degradation rate. This is a fundamental information in order to plan appropriate conservation strategies. (C) 2014 AIP Publishing LLC

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

Violante

Teodonio

Conte

et al. 2014

Phys. Status Solidi B

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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.

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Theoretical optical spectroscopy of complex systems

Cited by 7 publications

References 73 publications

Optical response of strongly absorbing inhomogeneous materials: Application to paper degradation

Optical response of strongly absorbing inhomogeneous materials: Application to paper degradation

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

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

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