We have used computational methodology based on the density functional theory to describe both copper(I) and copper(II) oxides, followed by the investigation of a number of different low index CuO surfaces. Different magnetic orderings of all the surfaces were studied and reconstructions of the polar surfaces are proposed. A detailed discussion on stabilities, electronic structure and magnetic properties is presented. CuO(111) and CuO(-111) were found to have the lowest surface energies and their planes dominate in the calculated Wulff morphology of the CuO crystal. We next investigated the adsorption of CO2 on the three most exposed CuO surfaces, viz. (111), (-111) and (011) by exploring various adsorption sites and configurations. We show that the CO2 molecule is activated on the CuO surfaces, with an adsorption energy of -93 kJ/mol adsorption energy on the (011) surface, showing exothermic adsorption, while (111) and (-111) surfaces show comparatively weak adsorption. The activation of the CO2 molecule is characterized by large structural transformations and significant charge transfer, i.e., forming a negatively charged bent CO2-δ species with elongated C-O bonds, which is further confirmed by vibrational analyses showing considerable red shift in the frequencies as a result of the activation.

A cost-effective synthesis was used to grow Zn_xCu_1−xO_y nanostructures. DFT calculations show that charge transfer along with changes in Fermi level facilitate H₂ gas sensing, which is further enhanced by Zn doping.

Hybrid metal oxide nano‐ and microstructures exhibit novel properties, which make them promising candidates for a wide range of applications, including gas sensing. In this work, the characteristics of the hybrid ZnO‐Bi₂O₃ and ZnO‐Zn₂SnO₄ tetrapod (T) networks are investigated in detail. The gas sensing studies reveal improved performance of the hybrid networks compared to pure ZnO‐T networks. For the ZnO‐T‐Bi₂O₃ networks, an enhancement in H₂ gas response is obtained, although the observed p‐type sensing behavior is attributed to the formed junctions between the arms of ZnO‐T covered with Bi₂O₃ and the modulation of the regions where holes accumulate under exposure to H₂ gas. In ZnO‐T‐Zn₂SnO₄ networks, a change in selectivity to CO gas with high response is noted. The devices based on individual ZnO‐T‐Bi₂O₃ and ZnO‐T‐Zn₂SnO₄ structures showed an enhanced H₂ gas response, which is explained on the basis of interactions (electronic sensitization) between the ZnO‐T arm and Bi₂O₃ shell layer and single Schottky contact structure, respectively. Density functional theory‐based calculations provide mechanistic insights into the interaction of H₂ and CO gas molecules with Bi‐ and Sn‐doped ZnO(0001) surfaces, revealing changes in the Fermi energies, as well as charge transfer between the molecules and surface species, which facilitate gas sensing.

Various forms of carbon, especially the nanocarbons, have received considerable attention in recent years. There has also been some effort to investigate borocarbonitrides, B_xC_yN_z, comprising besides carbon, the two elements on either side. Although uniformly homogeneous compositions of borocarbonitrides may be difficult to generate, there have been attempts to prepare them by solid state as well as gas phase reactions. Some of the products so obtained show evidence for the presence of BCN networks. Then, there are composites (G–BN) containing hexagonal BN (h-BN) and graphene (G) domains, G_1−x(BN)_x, in varying proportions. Nanotubes of B_xC_yN_z have been reported by several workers. The borocarbonitrides exhibit some interesting electronic and gas adsorption properties. Thus, some of the preparations show selective CO₂ adsorption. They also exhibit excellent characteristics for supercapacitor applications. In order to understand the nature of these understudied materials, it is necessary to examine the results from first-principles calculations. These calculations throw light on the variation in the band gap of G–BN with the concentration of h-BN, for different geometries of the domains and their boundaries. The possibility of formation of Stone–Wales (SW) defects at the interfaces of graphene and h-BN has been studied and the estimates of the formation energies of SW defects at the interfaces are ∼4 to 6 eV. The presence of such defects at the interfaces influences the electronic structure near the band gap and the associated properties. For example, adsorption of CH₄ and CO₂ occurs with significantly stronger binding at the interfacial defects.