Alkaline earth copper silicates, with the general formula ACuSi4​O₁₀​ (A: Ca²⁺, Ba²⁺), are materials of historical relevance, known since ancient times. Notable examples are CaCuSi4​O₁₀​ (Egyptian Blue) and BaCuSi4​O₁₀​ (Han Blue), dating back to 2500 BC and 1200 BC respectively, both valued for their vibrant blue color and remarkable resistance to wear over time. In addition to their historical value, their unique layered crystalline structure and their ability to emit light in the NIR region make them promising candidates for optoelectronics. Their intense pigmentation is due to a chromophore center with a square planar [CuO₄​] group, surrounded by [SiO₄​] tetrahedra.

Although these are excellent optoelectronic materials, the literature lacks procedures for synthesizing a nanomaterial with good dimensional homogeneity. Current studies focus on exfoliating pre-formed bulk materials. A further advantage is their very low toxicity and biocompatibility, a rare quality for materials used in solar-to-electricity conversion, IR light-emitting devices, and telecommunications.

In this work, we present our recent results on the synthesis of 2D nanosheets of these two compounds and of SrCuSi4​O₁₀​. By modifying the reagents of the hydrothermal synthesis and the exfoliation conditions, it was possible to alter the final compounds obtained. Varied morphologies have been obtained: nanosheets, rolled nanosheets, and spheres. Depending on the different solvents used to exfoliate the samples, they undergo preferential exfoliation along different planes, resulting in a consequent variation in the relative intensity of the XRD pattern. The study on the influence of these multiple factors on NIR emission is currently underway.