Experimental and theoretical UV/Vis-IR-THz spectroscopies
for diagnostic studies of ancient paper
Mauro Missori1*, Adriano Mosca Conte1,2 Conte, Olivia Pulci2
1Istituto dei Sistemi Complessi – CNR, Unità Sapienza, Rome, Italy
2Dipartimento di Fisica, Università di Roma Tor Vergata, Rome, Italy
(*) e-mail: [email protected]
Outline
Brief description of ancient paper degradation
UV/Vis spectroscopy: measurement of chromophores concentration
IR spectroscopy for the assessment of oxidative degradation of cellulose
THz spectroscopy for the study of supermolecular structure of cellulose
2/15
4v 11v
Codex on the Flight of Birds (circa 1505)
Degradation of paper arteworks
L. Micheli, C. Mazzuca et al., Microchemical Journal 138, 369-378 (2018)
Diana Scultori «Le Nozze di Psiche» (1613)
Leonardo da Vinci’s self-portrait (circa 1510)
Images acquired in 2012
Front Back
3/15
C
OH
Externaltemperature
humidity
radiations
microorganisms
Internalbyproducts
impurities
Degradation at the molecular scale
Mechanical and morphological degradation
hydrolysis
Variation of optical properties (yellowing)
UV-Vis active oxidized groups
(chromophores) containing carbonyl
(C=O) groups
oxidation
Development of acidic
byproducts (pH)
T. Lojewski, et al., Carbohydrate Polymers 82, 370 (2010).
S. Zervos, Natural and Accelerated Ageing of Cellulose and Paper: A Literature Review (2010).4/15
Measurement of paper optical response
10 mm
Whatman® 1
→ optical properties are strongly
governed by light scattering
Paper → fibres and voids with sizes > λ
→ optically inhomogeneous medium
Kubelka-Munk theory
Medium described by 2 phenomenological constants:
- absorption coefficient K
- scattering coefficient S
proportional to the concentrations (ci) of chromophores2(1 )
2
RK
S R
2i i i
i i
Kc
or black backing
integrating
sphere
Input
radiationoutput to
spectrometer
paper
G. Kortum, Reflectance Spectroscopy, Springer-Verlag (1969)
L. Yang, S. J. Miklavcic, J. Opt. Soc. Am. A 22, 9, 1866 (2005)
M. Missori et al., Physical Review B 89, 054201 (2014)
S is needed in order to recover K
5/15
UV-Vis results on the Leonardo’s drawings
Diffuse reflectance R∞
modern
sample
Pr1
Pr2 Pv
C4v
C2r
C11v
presence of several chromophores
Absorption coefficient (cm-1)
(cellulose fibers)
6/15
Time-Dependent
DFT Oxidized groups excited state
properties: dielectric function of
cellulose
→ UV-Vis absorption spectrumhttp://dp-code.org
Ground state properties: optimization
of the unitary cell geometry of pristine
and oxidized cellulose (monoclinic crystallographic phase Iβ)
Density
Functional
Theory (DFT)
http://www.quantum-espresso.org/
Cellulose chromophores theoretical simulation
Visible
diketone
Near UVCHObaldehyde
UV
ketone
7/15
UV-Vis experimental vs. theoretical spectra
Min [(exp(l)-ia
itheo
i(l))2 ] → c
i= (a
i/
ja
j) × 100%
2 mmol/100g cellulose
Minimal square
algorithmdiketones
aldehydes
ketones
6.1 mmol/100g cellulose
8/15
Chromophores concentration reduction in Le Nozze di Psiche (1613)
%
L. Micheli, C. Mazzuca et al., Microchemical Journal 138, 369-378 (2018)
M. Missori et al., Eur. Phys. J. Plus 134, 99-110 (2019)
9/15
Infrared spectroscopy of oxidized groups in cellulose
Near UV-Vis active
K. Ahn et al., Cellulose 26, 1, 429–444 (2019)
UV active
T. Łojewski et al., Appl Phys A 100, 809–821 (2010)
Transmission
experiments
cellulose 99.5%, lignin 0.5%
Aging at
90°C
RH=59%
days
cellulose 100.0%
days
10/15
Oxidized groups detection in pure cellulose paper
In collaboration with A. Nucara and M. Ortolani (Physics Dept., Sapienza Univ. of Rome)
Vacuum FT-IR spectrometer (Bruker IFS66v/S) equipped with reflection setup
Label Aging conditions Expected degradation factors Reactor type
D Dry air 90°C Air Drier
C Air at RH=59%, 90°C Air and water vapour Climatic chamber
V Air at RH=59%, 90°C Air, water vapour, gaseous by-products Closed vial
increasing
degradation
Spectra after 24 hours under vacuum
11/15
Difference spectra with unaged
Comparison with theoretical spectra
Taking into account Van der Waals interactions
OH
CH C=O
OH and CH
12/15
Formic acid
THz time-domain spectroscopy
Negligible ionization power
Penetrates optically opaque materials like painting layers,
paper, plastics ... but no metals …and water !
THz spectroscopyFrequency range 100 GHz - 10 THz (3 cm−1 - 300 cm−1)
Detection and identication of low-energy vibrational modes
Chemical analysis of intermolecular hydrogen bonds
Y. Ueno, Analytical Sciences, 24, 185-192 (2008)
C. Ciano et al., IEEE Trans. Terahertz Sci. Technol. 8, 4 (2018)
Clare J. Strachan et al., Chemical Physics Letters 390, 20–24 (2004)
K. Fukunaga, THz Technology Applied to Cultural Heritage in Practice, Springer, 2016
THz radiation for non-invasive diagnostics
crystalline
Indomethacin
(anti-inflammatory drug)
0.2 1 2 (THz)
13/15
33 67 100 (cm-1)
M. Missori et al., Microchem J 142, 54-61 (2018)
C. J. Garvey et al. Colloid and Polymer Science 297, 521–527 (2019)
THz time-domain spectroscopy
2.2 THz
2.7 THz
3.0 THz
Ab-initio low frequency vibrations
Moisture-activated dynamics on crystallite surfaces in cellulose14/15
Conclusions
Experimental and theoretical spectroscopy as non-destructive
diagnostic method for cultural heritage
Identification and quantification of chromophores in ancient paper
Identification of the IR spectra of oxidized groups in the ageing
process of cellulose
THz diagnostics of ancient paper: influence of water in the low-
frequency vibration of cellulose polymers
15/15
People
Adriano Mosca Conte Olivia Pulci
Paper restorationTheory
Experiments
Lorenzo Teodonio
Simonetta Iannuccelli Serena DominijanniSilvia Sotgiu
Arrigo Calzolari
Marco Buongiorno Nardeli
Claudia Violante
Joanna Łojewska Marco Peccianti
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