**Abstract**

The newly synthesized cadmium chalcogenide ternary cluster is composed by six [S3Se]2− tetrahedron units, coordinated with six Cd2+ cations. The potential cavity, calculated by the PLATON program, occupied 38.1% of crystal cell volume. The charge of unit cell is neutral. Therefore, the unit cell formula is determinate as [Cd6S18Se6]. Two strong solid-state luminescence peaks, centered at 450 nm and 498 nm, were observed from the ternary [Cd6S18Se6] clusters by λ = 370 nm radiation. The 450 nm peak is due to the porosity property of cadmium chalcogenide clusters. However, the 498 nm peak has not been reported for the cadmium chalcogenide clusters before. In this study, we demonstrate that the 498 nm peak is attributed to the embedded Se atoms confined in the [S3Se]<sup>2</sup><sup>−</sup> unit of [Cd6S18Se6] cluster. The luminescent output from the ternary [Cd8S18Se6] cluster is stable in room temperature for more than 6 months.

**Keywords:** cadmium chalcogenides, luminescence, porosity, quantum confinement
