In this study, the optical refractive constants of the (5, 5) SWBNNT and (5, 5) SWCNT systems were calculated in both parallel and perpendicular directions of the tube axis by using Quantum ESPRESSO and YAMBO code. It also extended the optical behaviors of (5, 5) SWCNT and (5, 5) SWBNNT to both perpendicular and parallel directions instead of the parallel directions reported in the literature. It also looked at the effects of the diameter of the nanotube on the optical properties instead of chiral angles. From our results, the best optical reflection was found for (5, 5) SWBNNT, while the best optical refraction was found with (5, 5) SWCNT. It was observed that the SWCNT demonstrates refraction in both parallel and perpendicular directions, while (5, 5) SWBNNT shows perfect absorption in perpendicular direction. These new features that appeared for both nanotubes in perpendicular directions were due to new optical band gaps, which appear in the perpendicular directions to both nanotubes’ axis. The electron energy loss (EEL) spectrum of SWBNNT revealed the prominent π- and π + δ- Plasmon peaks, which demonstrates themselves in the reflectivity spectrum. Furthermore, little effect of diameter was observed for the perpendicular direction to both nanotubes’ axis; as such, the combined properties of (5, 5) SWBNNT and (5, 5) SWCNT materials/systems for transmitting light offer great potential for applications in mobile phone touch screens and mobile network antennas. In addition, the studies of optical properties in the perpendicular axis will help bring ultra-small nanotubes such as SWCNT and SWBNNT to the applications of next-generation nanotechnology.

This study investigates the effect of exchange-correlation on the electronic properties of hybridized hetero-structured nanomaterials, called single-walled carbon boron nitride nanotubes (SWCBNNT). A first principles (ab initio) method implemented in Quantum ESPRESSO codes, together with different parametrizations (local density approximation (LDA) formulated by Perdew Zunga (PZ) and the generalized gradient approximation (GGA) proposed by Perdew–Burke–Ernzerhof (PBE) and Perdew–Wang 91 (PW91)), were used in this study. It has been observed that the disappearance of interface states in the band gap was due to the discontinuity of the π–π bonds in some segments of SWCNT, which resulted in the asymmetric distribution in the two segments. This work has successfully created a band gap in SWCBNNT, where the PBE exchange-correlation functional provides a well-agreed band gap value of 1.8713 eV. Effects of orbitals on electronic properties have also been studied elaborately. It has been identified that the P^y orbital gives the largest contribution to the electrical properties of our new hybrid SWCBNNT nanostructures. This study may open a new avenue for tailoring bandgap in the hybrid heterostructured nanomaterials towards practical applications with next-generation optoelectronic devices, especially in LED nanoscience and nanotechnology.

This study investigated the photocatalytic properties of MoS₂-doped boron nitride nanotubes (BNNTs) for overall water splitting using popular density functional theory (DFT). Calculations of the structural, mechanical, electronic, and optical properties of the investigated systems were performed using both the generalized gradient approximation and the GW quasi-particle correction methods. In our calculations, it was observed that only (10, 10) and (12, 12) single-walled BNNTs (SWBNNTs) turned out to be stable toward MoS₂ doping. Electronic property calculations revealed metallic behavior of (10, 10)-MoS₂-doped SWBNNTs, while the band gap of (12, 12) SWBNNT was narrowed to 2.5 eV after MoS₂ doping, which is within the obtained band gaps for other photocatalysts. Hence, MoS₂ influences the conduction band of pure BNNT and improves its photocatalytic properties. The water-splitting photocatalytic behavior is found in (12, 12) MoS₂-doped SWBNNT, which showed higher water oxidation (OH^-/O₂) and reduction (H⁺/H₂) potentials. In addition, optical spectral calculations showed that MoS₂-doped SWBNNT had an optical absorption edge of 2.6 eV and a higher absorption in the visible region. All of the studied properties confirmed MoS₂-doped SWBNNT as a better candidate for next-generation photocatalysts for hydrogen evolution through the overall water-splitting process.

Investigation of the effects of oxygen absorption on the two types of single walled silicon carbide nanotubes (SWSiCNTs) with different chiral angles were done. Our calculations were performed using density functional theory with quantum ESPRESSO and YAMBO codes. Changes in electrical and optical properties were analyzed after introducing two molecules of oxygen as absorbing gas to both armchair and zigzag nanotubes. Results demonstrated a new future by SWSiCNT in which oxygen absorption significantly closes the band gap which transformed the materials from semiconducting to metallic. This future revealed its potential for application as automobile gas switches for air conditioners. Results from optical calculations revealed that zigzag SiCNT is not optically potential above 20 eV, generally, the (6, 6) SWSiCNT demonstrate higher transmission with and without oxygen absorption in the ultraviolet region. The first absorption peaks appeared within the range of 1 eV to 3.4 eV for all systems, there is higher absorption by the oxygen absorbed (6, 6) SWSiCNT than the oxygen absorbed (6, 0) SWZSiCNT. This demonstrates that armchair form of SWSiCNT absorbs gases more than the zigzag form. The absorption peaks can be seen to fall above 3.5 eV and then rise again up to 10 eV, this behavior justifies the nanotubes potential in automobile day light sensors.