Exfoliation of Egyptian Blue and Han Blue, Two Alkali Earth Copper Silicate-based Pigments

Abstract

In a visualized example of the ancient past connecting with modern times, we describe the preparation and exfoliation of CaCuSi 4 O 10 and BaCuSi 4 O 10 , the colored components of the historic Egyptian blue and Han blue pigments. The bulk forms of these materials are synthesized by both melt flux and solid-state routes, which provide some control over the crystallite size of the product. The melt flux process is time intensive, but it produces relatively large crystals at lower reaction temperatures. In comparison, the solid-state method is quicker yet requires higher reaction temperatures and yields smaller crystallites. Upon stirring in hot water, CaCuSi 4 O 10 spontaneously exfoliates into monolayer nanosheets, which are characterized by TEM and PXRD. BaCuSi 4 O 10 on the other hand requires ultrasonication in organic solvents to achieve exfoliation. Near infrared imaging illustrates that both the bulk and nanosheet forms of CaCuSi 4 O 10 and BaCuSi 4 O 10 are strong near infrared emitters. Aqueous CaCuSi 4 O 10 and BaCuSi 4 O 10 nanosheet dispersions are useful because they provide a new way to handle, characterize, and process these materials in colloidal form.

Exfoliated near infrared fluorescent silicate nanosheets for (bio)photonics

“…Bulk EB shows a remarkable high quantum yield of 10.5% for a NIR emitter compared with SWCNTs, quantum dots, metal nanoclusters, and FDA-approved fluorophores such as ICG 5,28 . Recently, micrometer-sized monolayer sheets of EB were isolated by stirring in hot water for several days 29,30 . However, the remarkable properties of EB have not been explored for developing NIR luminescent nanomaterials for bioimaging applications.…”

Late production of Egyptian blue: synthesis from brass and its characteristics

“…In the second experiment, similar mixtures of brass, SiO 2 and CaCO 3 were heated in the same way but no flux was added and the temperature was raised to 975 °C. The conditions chosen for the second experiment are similar to those proposed in literature for solid-state synthesis (Johnson-McDaniel and Salguero 2014). Once at room temperature, the crucibles of both preliminary experiments were photographed with the Visible Induced Luminescence (VIL) technique to detect the presence of cuprorivaite-like materials formed.…”

Egyptian blue pigment in East Mediterranean wall paintings: A study of the lifetime of its optical infrared emission

“…Different ground particles were produced, varying in size between 125 and 250 μm. Two experimental methods have recently been reported for the production of the pigment described by Johnson‐McDaniel et al: The melt‐flux method requires lower temperature (875 °C) and produced smaller sized particles in the laboratory (5–15 μm crystallites by SEM), whereas solid state synthesis yielded larger particle sizes (15–50 μm) but requires higher synthesis temperatures (1020 °C), thus above the melting point of bronze. In archaeological studies, Grifa et al demonstrated that high temperatures were achieved in synthesis using crucibles from Cuma, thus exceeding the thermal stability of cuprorivaite crystals (950–1050 °C), thus within the range for both synthesis routes.…”