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Two-dimensional materials from group IVA namely graphene, silicene, and germanene have gained research interest in various fields of applications recently due to their extraordinary properties. These substrates have been successfully synthesized and are found to have interesting gas sensing capabilities. In this work, first-principles study using density functional theory is carried out to investigate the adsorption of toxic gases such as CO, Cl2, NO2, and COCl2 on these monolayers. We analyze the best adsorption site and orientation for these molecules on the monolayers by calculating the adsorption energy. Charge transfer, the density of state (DOS) and band diagram calculations are performed to explore the changes in their electronic and structural properties due to the adsorbed gas molecules. As for the sensing performance, crude estimations of the sensitivity and recovery time are performed. The results show that silicene and germanene monolayers are better at detecting CO and NO2 as compared to graphene. They have a short recovery time for CO but a long recovery time for NO2 implying that they are better for scavenging NO2. Besides, silicene is also a better gas sensor for chlorine gas with a 44 min recovery time. As for graphene, it is the best gas sensor for phosgene among the substrates. This study gives a clear prediction of substrates for the detection of these toxic gases.

The aim of this work is to determine the effect of neodymium nanoparticles concentration on the elastic properties of zinc-tellurite glass. A series of neodymium nanoparticles doped zinc-tellurite glass systems (NdNPsZT) of composition= 0.01, 0.02, 0.03, 0.04, and 0.05, were synthesized by using conventional meltquenching method. The amorphous nature of the glass system was confirmed by using XRD analysis. The density of the glass system was determined by Archimedes method. The elastic properties were calculated from the measured density and ultrasonic velocity at 5 MHz frequency. The experimental results showed that the elastic properties rely upon the composition of the glass systems and the impact of neodymium nanoparticles (Nd 2 O 3 NPs) within the glass network. The increase in ultrasonic velocities is due to the increase in rigidity and change in structural units of the glass system. The softening temperature and the microhardness increased with the increase in Nd 3+ ions concentration from 0.1 to 0.2 mol and decreased when the Nd 3+ ions concentration increased from 0.2 to 0.5 mol. Poisson's ratio and Debye's temperature decreased with the increase in the Nd 3+ ions concentration from 0.1 to 0.2 mol and increased when the Nd 3+ ions concentration was increased from 0.2 to 0.5 mol.