▎ 摘　　要

Using density functional theory calculations, we have examined the structural stability, electronic, magnetic, and optical properties of rectangular shaped quantum dots (QDs) of graphene (G), boron nitride (BN), and their hybrids. Different hybrid QDs have been considered by substituting a GQD (BNQD) with BN-pairs (carbon atoms) at different positions. Several parameters, like size, amount of substitution, and so forth, have been varied for all these QDs (GQDs, BNQDs, hybrid-QDs) to monitor the corresponding changes in their properties. Among the considered parameters, we find that substitution can act as a powerful tool to attain interesting properties with these QDs, for example, a broad range of absorption (similar to 2000 nm) in the near-infrared (NIR) region, spin-polarized HOMO-LUMO gaps without the application of any external-bias, and so forth, which are highly required in the preparation of opto-electronic and electronic/spintronic devices, among others. Explanations have been given in detail by varying different factors, like changing the position and amount of substitution, application of external electric field, and so forth, to ensure the reliability of our results.