The use of the two deep UV-optimized
microscopes at the DISCO beamline
[4] provided unprecedented coupling
of submicrometric spatial resolution
and 3 orders of magnitude in spatial
dynamics, with synergistic spectral
and spatial characterization of samples.
Radiometric calibration of spectra
from raster scan microspectroscopy
measurements was implemented
using self-written procedures and
the SpectroMicro Package developed
at IPANEMA. RGB false colors images of
the historical ZnO pigments shown were
constructed using correction to provide
identical intensity scaling thereby allowing
visual intercomparison of the main
associated emissions.
We have performed careful measurements
at high spatial and spectral resolution
to obtain the distribution of the emission
spectra in different powder samples,
and have shown that we can discriminate
among them. Historical zinc white
powders that appear homogeneous at
the macroscale are highly heterogeneous
at the micro- and nanoscales, and are
markedly distinct from one another in
that the relative intensities of the band-
edge and the two defect-associated
emissions observed at the submicrometer
scale are very different (Fig.
➊
). Access
to this resolution, thus far inaccessible
with conventional PL in the DUV, allowed
straightforward visualization, comparison,
and study of the luminescence from
individual mineral grains (Fig.
➋
). Having
established that we can identify and
measure the diverse PL behavior of
different batches of ZnO, we are interested
in how it compares to particle shapes
and size, and how it corresponds to known
variation in chemistry, demonstrated
by the variability in long-term stability
of different paints. This research shows
that we can compare ZnO in various
artworks, and in different layers within one
work to help determine the relationships
between them, such if they were painted
using the same batch of paint.
A new synchrotron approach to study ancient materials
Differentiating pigments at the grain level
DISCO beamline & IPANEMA
ASSOCIATED PUBLICATION
A multiscalar photoluminescence approach
to discriminate among semiconducting
historical zinc white pigments
L. Bertrand*, M. Réfrégiers, B. Berrie,
J-P. Echard, and M. Thoury
Analyst 138(16) (2013), 4463
REFERENCES
[1] H. Kühn, in Artists' Pigments: A Handbook
of their History and Characteristics vol. I, ed.
R. L. Feller, National Gallery of Art,
Washington, DC, USA, 1986, 169
[2] M. Thoury et al. Anal. Chem. 83 (2011), 1737
[3] L. Bertrand et al. Phys. Rep. 519 (2012), 51
[4] F. Jamme et al. Microsc. Microanal.
16 (2010), 507
* IPANEMA, CNRS, Ministère de la Culture
et de la Communication, USR 3461, BP48
Saint-Aubin, 91192 Gif sur Yvette cedex,
France; Synchrotron SOLEIL
CORRESPONDING AUTHOR
➋
Synchrotron full-field PL images of a zinc white powder under DUV excitation (280 nm, 100 × objective,
153 nm projected pixel size; scale bar: 500 nm).
95
SOLEIL
HIGHLIGHTS
2013
