Design and Characterization of Irida-Graphene and Boron-Nitrogen Co-Doped Quantum Dots via DFT Calculations

The novel material known as Irida-Graphene (IG), consisting of fused rings composed of trigons, hexagons, and octagons, has recently been predicted by Júnior et. al to be computationally stable1. This ground-breaking substance has the potential to produce exceptional electronic structures, possess outstanding mechanical and thermal properties, all while maintaining remarkable stability1. Nevertheless, it is noteworthy that at the GGA/PBE level, the material's infinite form is metallic, which limits its applications to the semiconductor domain, such as electronics, computing, optoelectronics, and sensing2. The ingenious concept of quantum confinement has presented us with a multitude of ways to tailor and finely tune the properties of matter3. As a result, the quantum dots of IG have been systematically engineered from the infinite 2D sheet employing the state-of-the-art computational chemistry software, Gaussian16 within the density functional theory(DFT) framework4. After optimization, the structure of IG quantum dot has been found to be highly stable, devoid of any imaginary Raman frequency, while simultaneously achieving a band gap opening. To enhance the band gap and fine-tune the properties, heterogeneous doping has emerged as a powerful tool with boron and nitrogen as key dopants5. Leveraging this approach, this work proposed three more novel quantum dots, each with a unique dopant configuration. These include: 1) Boron-Nitrogen doping at the central hexagonal ring (IG-BN-c), 2) Boron-Nitrogen doping at a single octagon (IG-BN-o1), and 3) Symmetrical Boron-Nitrogen doping across two hexagons (IG-BN-o2) as presented in Fig. 1. The optimization of all structures was conducted using the B3LYP functional in conjunction with the 6-31G(d,p) basis set, a widely recognized and trusted approach in computational chemistry. The findings of this study have far-reaching implications, as all three proposed structures exhibit exceptional stability with positive phonon modes and induce significant changes in their structural, electronic, and optical properties. Moreover, the Raman-active region of the IG quantum dot significantly increases after boron-nitrogen doping, serving as a benchmark for experimental calculations. The IG-BN-o1 structure attains a minimum band gap of 0.828 eV, while the IG-BN-o2 structure achieves a maximum band gap of 1.349 eV. The band gap of the IG is modulated by the introduction of dopants, which varies depending on several factors, such as the symmetry and number of boron and nitrogen atoms. This demonstrates the remarkable capability of the IG and BN co-doped structures to tailor their band gap to specific requirements, depending on the dopant location. The IG-BN-o1 structure attains a minimum band gap of 0.828 eV, while the IG-BN-o2 structure achieves a maximum band gap of 1.349 eV. Employing the time-dependent DFT at the same level of theory, this study has demonstrated a remarkable increase in the intensity of optical peaks following dopant introduction. The emergence of both red-shifted and blue-shifted peaks serves as compelling evidence of the significant impact of doping on the optical spectra. These results hold immense potential for the development of advanced materials with customized electronic and optical properties.