American Chemical Society
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Magnetic and New Optical Properties in the UV–visible Range of the Egyptian Blue Pigment Cuprorivaite CaCuSi4O10

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journal contribution
posted on 2021-11-09, 14:33 authored by Laurent Binet, Juliette Lizion, Sylvain Bertaina, Didier Gourier
Cuprorivaite CaCuSi4O10, the so-called Egyptian blue pigment, exhibits a characteristic and well-known near-infrared luminescence upon excitation in Cu2+ d–d transitions. Here, we show that upon excitation in the UV, this near-infrared emission is considerably amplified and is accompanied by three different UV–visible emission bands. These four UV-excited emissions are attributed to self-trapped excitons (emission at 2.8 eV), to excitons trapped at Cu sites (emission at 1.4 eV), and to trapped exciton emission where the hole is only trapped at Cu sites (emissions at 2.65 and 3.27 eV). Despite the high Cu content of cuprorivaite, electron magnetic resonance reveals only a weak antiferromagnetic interaction (about 0.08 meV), which averages out the hyperfine interaction of the electron spin with nuclear spins of 63Cu and 65Cu nuclei.