Green Mechanochemical Synthesis of Binary and Ternary Cadmium Chalcogenides with Tunable Band Gaps

In this work, we report on the mechanochemical preparation and characterization of binary (CdS, CdSe, and CdTe) and ternary (CdS_0.5Se_0.5, CdS_0.5Te_0.5, and CdSe_0.5Te_0.5) cadmium chalcogenides. The compounds were synthesized in a planetary micro mill using a zirconia grinding bowl and zirconia grinding balls. The products were examined by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), UV–Vis spectroscopy, and differential scanning calorimetry (DSC). Interestingly, CdO formed as a by-product only during milling of Cd+S and Cd+Se in air, while it was absent in the Cd+Te and all ternary systems. The materials were obtained in the form of irregularly shaped aggregates measuring up to several hundred nanometers, composed of nearly spherical primary nanoparticles with diameters in the 10–20 nm range. The band gap energies calculated using Tauc plots for CdS_0.5Se_0.5, CdS_0.5Te_0.5, and CdSe_0.5Te_0.5 were 2.01 eV, 1.72 eV, and 1.53 eV, respectively. These results demonstrate the expected tunability of band gaps in ternary cadmium chalcogenides and attest to the potential of such materials for semiconducting applications, particularly in solar cells. The mechanochemical approach is once again shown to be a simple and effective method for the preparation of both binary and ternary chalcogenides, avoiding the use of solvents, toxic precursors, and energy-consuming reaction conditions.