Time-Resolved Photoluminescence Spectroscopy and Imaging: New Approaches to the Analysis of Cultural Heritage and Its Degradation

Abstract

Applications of time-resolved photoluminescence spectroscopy (TRPL) and fluorescence lifetime imaging (FLIM) to the analysis of cultural heritage are presented. Examples range from historic wall paintings and stone sculptures to 20th century iconic design objects. A detailed description of the instrumentation developed and employed for analysis in the laboratory or in situ is given. Both instruments rely on a pulsed laser source coupled to a gated detection system, but differ in the type of information they provide. Applications of FLIM to the analysis of model samples and for the in-situ monitoring of works of art range from the analysis of organic materials and pigments in wall paintings, the detection of trace organic substances on stone sculptures, to the mapping of luminescence in late 19th century paintings. TRPL and FLIM are employed as sensors for the detection of the degradation of design objects made in plastic. Applications and avenues for future research are suggested.

Degradation of Cd-yellow paints: Ab initio study of native defects in {10.0} surface CdS

“…In order to better understand the origin of their color and luminescence in the paint layer, recent studies [14,15,16,17,18] have focused on luminescence emission lifetimes of luminescent materials. Cd-and Zn-based pigments were characterized [17] both by a rapid picosecond lifetime band gap emission related to pigment composition and by further radiative relaxation decay paths due to trap state levels connected to the presence of intrinsic and extrinsic defects.…”

“…Cd-and Zn-based pigments were characterized [17] both by a rapid picosecond lifetime band gap emission related to pigment composition and by further radiative relaxation decay paths due to trap state levels connected to the presence of intrinsic and extrinsic defects. The first application of lifetime imaging [18] for the mapping of long-lived luminescence from the ZnO semiconductor pigment was on the painting on the paper "Les bretonnes et le pardon de pont Aven" of Vincent Van Gogh.…”

Dual wavelength excitation for the time-resolved photoluminescence imaging of painted ancient Egyptian objects

“…With these methods, the detection of PL can be carried out with imaging spectrometers or suitably filtered imaging detectors [13,14]. Another approach to the imaging of the PL from works of art relies on the detection of the emission lifetime, which can be achieved by combining pulsed laser excitation with a time-gated imaging detector, known as fluorescence lifetime imaging or, more generally, TRPL Imaging [15]. Applications of TRPL imaging for the detection of organic materials on stone sculptures [16], wall paintings [17], and semiconductor pigments on paper [18] have been published, and demonstrate how TRPL imaging can map the chemical composition of surfaces based on significant differences in emission lifetime.…”

A new insight into polyurethane foam deterioration – the use of Raman microscopy for the evaluation of long‐term storage conditions

“…Aromatic rings and amides have been described as responsible for the green (in flavins bonded to proteins under blue light) and blue (in protein compounds under ultraviolet light) fluorescence of animal and plant tissues . From previous studies concerning the fluorescence of polymers, the presence of aromatic fluorophores was also referred to cause emission . However, the fluorescence of the model PUR is weaker [Fig.…”

“…One could be associated to the formation of conjugated double bonds, deterioration products from protein compounds and to modifications on the microenvironment surrounding fluorescent species (such as aromatic rings) and, the second, to modifications on the redox state of the polymer . In relation to the first hypothesis, these changes were proved to give rise to fluorescence bands that were not present on the unaged samples . Regarding the second, according to one study about the autofluorescence of cells, the fluorescence intensity of these compounds depends on the redox state of the cell .…”