Bottom-up strategies for emissive silicates nanocrystals

Alkaline earth copper silicates with the general formula ACuSi₄O₁₀ (where A = Ca2+ and Ba2+) represent a family of materials known since antiquity.[1] In particular, CaCuSi₄O₁₀ and BaCuSi₄O₁₀ traced back in 2500 BC and 1200 BC, and known as Egyptian blue and Han blue, respectively, are characterized by an intense blue color and high stability over time.[2] Besides historical interest, the peculiar layered crystalline structure and their emission in the near infrared region (NIR), makes them interesting new materials for optoelectronic applications.[3] The chromophore group is characterized by a [CuO4] in a square planar geometry surrounding by [SiO₄] tetrahedra.[4] Recent studies have demonstrated the possibility of obtaining them in nanometric dimensions through exfoliation.[5] In this work, we present our recent findings on the preparation of colloidally stable 2D nanosheets based on the aforementioned copper silicate compounds. The synthesized nanoplates exhibit an average lateral diagonal of 34 nm and a thickness of 6 nm (Figure 1). Their photoluminescence properties are consistent with those of the bulk material, featuring an excitation maximum at 618 nm and an emission peak at 950 nm. Furthermore, absorbance measurements in cuvettes demonstrate a nearly complete absence of scattering from the suspensions, confirming the high quality and stability of the resulting colloidal dispersions. This innovative synthetic protocol paves the way for a new class of 2D nanomaterials with promising applications in the fields of biomedical imaging, photovoltaic energy conversion, and IR light-emitting devices. Furthermore, their unique optical properties and stability make them excellent candidates for integration into advanced telecommunication systems.