XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
20
I–2
Towards a new reference material for microfading spectrometry
of art objects
Tomasz Łojewski
1
, and Anna Klimek
2
1
AGH University of Science and Technology, Faculty of Materials Science and Ceramics,
al. Mickiewicza 30, 30-059 Kraków, Poland, e-mail: lojewski@agh.edu.pl
2
National Museum in Krakow, Laboratory of Analysis and Nondestructive Investigation of Heritage
Objects, National Centre for Cultural Heritage Science, ul. Piłsudskiego 14, 31-109 Kraków, Poland
Microfading testing (MFT) of cultural heritage objects helps in preparing and implementing
preventive conservation strategy and conservation treatment, based on data obtained for actual
artworks, thanks to nondestructive nature of MFT measurements. Blue Wool Standard scale
(BWS) has been widely used as a reference material in lightfastness studies. However, when
applied for microfading tests BWS presents a number of disadvantages. Test strips are made of
textile and have uneven surface (as warp and weft threads are inserted over-and-under) and non-
uniform staining of treads which leads to a low repeatability of results for BWS tested on a
submillimeter scale (usually 0.5 mm in diameter, depending on the MFT instrument design).
What is more, as MFT measurement causes irreversible colour change of BWS and thus testing
the same, already aged spot is possible and would lead to large errors. In the light of the above,
research concerning a new reference material seems to be well-founded.
In the ongoing research presented here we investigate the use of photochromic dye
(spirooxazine compound) incorporated into polymer matrix as a new reference material for
microscale lightfastness studies. Spirooxazines represent the most important class of
photochromic dyes nowadays. The use of such compound in MFT tests is possible thanks to the
fact that the photocleavage of spiro bond and transition into merocyanine takes place under
visible light (most of the spirocompounds absorb in the UV spectral region of the spectrum).
Colour change can only occur in a dye-matrix system. Suitable polymer matrix must provide
enough free volume for spirooxazine molecules to rotate but at the same time partially
immobilize them in order to slow down the reaction. Selection of polymer matrix is crucial for
the research. It should be pointed out, that contrary to BWS color change for polymer embedded
photochromic dye does not depend on the access to oxygen and water and thus is not sensitive to
changing environmental conditions. Another great advantage of spirocompound-based material
over BWS is its reversibility, as the merocyanine-spirooxazine transition occurs thermally
(under dark conditions). It gives an opportunity to create a reproducible and everlasting
reference material for MFT.
Results of measurements (e.g. reciprocity tests, repeatability of reflectance time-series and
CIE L*a*b* colour parameters obtained in the course of accelerated light ageing tests) for
spirooxazine-polymer systems would be compared to those obtained for BWS from leading
producers.
Keywords: accelerated light ageing; reference material; fiber-optics reflectance spectroscopy
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
21
I–3
IR photoacoustic spectroscopy – a tool for catalysts characterization
Janusz Ryczkowski
1
1
Faculty of Chemistry, Maria Curie-Sklodowska University, Pl. M. Curie-Sklodowskiej 3, 20-031
Lublin, Poland, e-mail: janusz.ryczkowski@umcs.eu
The analysis of solid samples can often be a difficult problem for the researchers dealing
with infrared (IR) spectroscopy. In conventional absorption spectroscopy the measurement of
absorption is transferred to that of the radiation transmitted through the sample. Three methods
stand out as being more suitable for studying solid materials. These methods are: diffuse
reflectance (DR), photoacoustic spectroscopy (PAS), and Fourier transform (FT) Raman. All
three methods require little or no sample preparation, and therefore are ideal for the samples that
may change during the preparation as mineral oil mulls or KBr disks. In the case of PAS, the
adsorbed radiation is determined directly via its heat and hence the sound produced in the
sample. Fourier transform infrared PAS (FT-IR/PAS) is one of the main IR techniques which
can be successfully applied in catalysis and surface science research. Some examples of this
spectroscopic technique application will be presented [1–5].
Photoacoustic (PA) measurements are unique in that they depend directly on the energy
absorbed by the sample, rather than on what is transmitted or reflected [1–3]. Electromagnetic
radiation absorbed in a sample excites ground state molecules to higher energy levels. The
excited states relax either radiatively or nonradiatively (Fig. 1) [4].
Fig. 1. Thermal effects due to light interaction with the studied sample [4].
Keywords: IR; photoacoustic; catalysis
References
[1] J. Ryczkowski, Catal. Today 68 (2001) 263.
[2] J. Ryczkowski, Catal. Today 124 (2007) 11.
[3] J. Ryczkowski, Laser spectroscopy applied to catalysis research, Chapter 14 in Lasers in chemistry:
probing and influencing matter (M. Lackner, Ed.), Wiley-VCH, 2008, ISBN: 978-3-527-31997-8, pp
403.
[4] J. Ryczkowski, Appl. Surf. Sci. 256 (2010) 5545.
[5] J. Kurczewska, J. Ryczkowski, S. Pasieczna-Patkowska, G. Schroeder, Spectrosc. Lett. 49 (2016) 529.
Dostları ilə paylaş: |