Differentiation of black writing ink on paper using luminescence lifetime by time-resolved luminescence spectroscopy

•Time-resolved luminescence and lifetimes of eighteen writing inks were measured.•Some samples only had short-lived luminescence components in the nanosecond region.•Other samples exhibited short- and long-lived components in the microsecond region.•Lifetimes of the long-lived components depended on the samples.•Luminescence lifetime could be used for the differentiation of writing inks.

The time-resolved luminescence spectra and the lifetimes of eighteen black writing inks were measured to differentiate pen ink on altered documents. The spectra and lifetimes depended on the samples. About half of the samples only exhibited short-lived luminescence components on the nanosecond time scale. On the other hand, the other samples exhibited short- and long-lived components on the microsecond time scale. The samples could be classified into fifteen groups based on the luminescence spectra and dynamics. Therefore, luminescence lifetime can be used for the differentiation of writing inks, and luminescence lifetime imaging can be applied for the examination of altered documents.

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