Fig. 1

PL analysis of the Egyptian blue painted model sample. (top) PL emission spectrum and (bottom) PL emission lifetime following 532 nm pulsed excitation of the model sample painted with the commercial Egyptian blue pigment. A linear fit of the detected emission decay kinetic (black line) on the basis of a monoexponential model and goodness of fit in terms of R². The sample exhibits an emission spectrum peaked at 920 nm and a monoexponetial decay kinetic with a lifetime of 138 μs