Enhanced photocatalytic performance of CdFe2O4/Al2O3 nanocomposite for dye degradation.

In the present work, CdFe2O4/Al2O3 magnetic nanocomposite photocatalyst is successfully synthesized by simple sol-gel auto-combustion method. The role of this sample is studied as a photocatalyst. The influence of Al2O3 concentration with CdFe2O4 on the photocatalytic property is also studied. We have considered three weight percentage of Al2O3, 5%, 10%, and 20% with CdFe2O4. All the samples are characterized with X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), vibrating sample magnetometer (VSM), UV-Visible, and photoluminescence (PL) spectroscopy techniques. The 10% composite sample showed the lower particle size, higher surface area, enhanced porosity, higher saturation magnetization, and considerable band gap as compared to that of 5% and 20% CdFe2O4/Al2O3 as well as bare CdFe2O4 nanoparticles. The photocatalytic activity of the sample is evaluated towards the degradation of the xylenol orange (XO) dye under UV light. The degradation process of the dye is monitored spectrophotometrically. The performance in terms of removal efficiency is studied by varying the contact time, dye concentration and amount of catalyst. Among the three concentrations of Al2O3, the 10% weight concentration of Al2O3 with CdFe2O4 is found to be the optimal concentration and showed the higher degradation rate. After 30 min photocatalytic reaction, the degradation rate is 92.29% for 10% CdFe2O4/Al2O3 and for bare CdFe2O4, it is 85.79%. This work provides a new reference for designing Al2O3-based spinel ferrite nanocomposites and their role in wastewater management.

Structural, electronic and optical properties of metalloid element (B, Si, Ge, As, Sb, and Te) doped g-ZnO monolayer: A DFT study.

Stable geometries, electronic structure, and optical properties of ZnO monolayer doped with metalloid element (M = B, Si, Ge, As, Sb, and Te) atom have been studied using density functional theory. It is found that among these elements Ge, As, and Sb can be effectively doped at Zn site in the ZnO monolayer with the formation energies ranging from -1.02 to -0.96 eV. Except B element, all the metalloid atoms prefer to protrude out of the plane of the ZnO monolayer. The nonmagnetic nature of the ZnO monolayer is retained with the doping of B, Si, Ge, As, and Sb atom, while Te atom induces the magnetism in ZnO monolayer (2 µB). While doping of Si, As, Sb, and Te in ZnO monolayer resulted in a red shift in the absorption spectra of doped ZnO monolayer and the blue shift is observed for B and Ge doped ZnO. The static dielectric constant for ZnO monolayer is 1.49. With the doping of these metalloid elements in ZnO monolayer, the dielectric constant can be tuned from 1.36 to 2.84. These results are potentially useful for optoelectronic applications and the development of optical nanostructures.

Theoretical study of interaction of Fe13O8@Zn48O48 cluster with dopamine: Magnetic and optical properties.

In this study, we modelled the interaction of Fe13O8 and Fe13O8@Zn48O48 (core@shell) cluster with a biologically active dopamine molecule using density functional theory. First, the electronic, magnetic and optical properties of core@shell, Fe13O8@Zn48O48 cluster investigated and compared with isolated Fe13O8 and Zn48O48 clusters. Fe13O8@Zn48O48 cluster is found to be energetically stable. For Fe13O8 and Fe13O8@Zn48O48 clusters have the net magnetic moment 42 µB. The decrease in HOMO-LUMO gap of core@shell cluster as compared to that of isolated clusters reflects the higher reactivity. The results of the site dependent interaction of Fe13O8 and Fe13O8@Zn48O48 clusters with dopamine molecule are presented. The interaction strength is determined in terms of the cluster-dopamine complex binding energy and found to be enhanced for core@shell cluster than the Fe13O8. Furthermore, the calculated results predict that in presence of dopamine, the magnetic moment of Fe13O8 and Fe13O8@Zn48O48 cluster remains unaffected. The analysis of optical spectra of core@shell indicates the obvious red shift compared to Zn48O48 clusters. The optical spectra of Fe13O8@Zn48O48-dopamine shows the higher oscillator strength as compared to that of Fe13O8-dopamine complex. Fe13O8-dopamine complex gives rise to more quenched oscillator strengths as compared to that of bare iron oxide cluster. These results indicate interesting magneto-optical behaviour, which can be useful for biomedical applications.

Sensing Characteristics of a Graphene-like Boron Carbide Monolayer towards Selected Toxic Gases.

By using first-principles calculations based on density functional theory, we study the adsorption efficiency of a BC3 sheet for various gases, such as CO, CO2, NO, NO2, and NH3. The optimal adsorption position and orientation of these gas molecules on the BC3 surface is determined and the adsorption energies are calculated. Among the gas molecules, CO2 is predicted to be weakly adsorbed on the graphene-like BC3 sheet, whereas the NH3 gas molecule shows a strong interaction with the BC3 sheet. The charge transfer between the molecules and the sheet is discussed in terms of Bader charge analysis and density of states. The calculated work function of BC3 in the presence of CO, CO2, and NO is greater than that of a bare BC3 sheet. The decrease in the work function of BC3 sheets in the presence of NO2 and NH3 further explains the affinity of the sheet towards the gas molecules. The energy gap of the BC3 sheets is sensitive to the adsorption of the gas molecules, which implies possible future applications in gas sensors.

Density functional calculations of the structural and electronic properties of (Y2O3)(n)(0,±1) clusters with n = 1-10.

We report results of ab initio calculations on yttrium oxide clusters using a plane wave pseudopotential method within density functional theory. (Y2O3)n clusters in the size range n = 1-10 prefer compact and symmetric globular configurations where preference for an octahedron unit of Y6O8 is seen. The evolution of the atomic structures shows similarity with that of the local structure in the bulk cubic (C-Y2O3) phase. The maximum coordinations of Y and O atoms are 6 and 4, respectively. The addition (removal) of an electron to (from) the lowest energy configurations of the neutral clusters induces significant changes for some of the cluster sizes. Sequential addition of a Y2O3 unit to the (Y2O3)n cluster leads to an increase in the binding energy. However, the HOMO-LUMO gap, ionization potential, and electron affinity do not show any systematic variation in these clusters with increasing size. The bonding characteristics have been studied using charge density and Bader charge analysis. The charge transfer from Y atoms to oxygens increases with the increase in the cluster size and approaches the value in bulk. The stability of the clusters is dominated by ionic Y-O interactions. However, a small degree of covalency is also seen in Y-O bonding. All the lowest energy configurations of neutral clusters prefer the lowest spin state and the ionic clusters prefer a doublet state.

Optical properties of gallium oxide clusters from first-principles calculations.

The optical properties of the (Ga(2)O(3))(n) clusters, with n = 1-10, have been studied within the framework of time dependent density functional theory. The gallium oxide cluster geometries showed evolution from planar configuration (C(2v)) for Ga(2)O(3) to layered globular configuration (C(s)) for (Ga(2)O(3))(10) via corundum configuration (D(3d)) for (Ga(2)O(3))(4). For n ≤ 5, with the increase in coordination of Ga and O atoms, the polarizability decreases with the size of the cluster. For n ≥ 6, with the stabilization of average coordination number for gallium and oxygen atoms, the decrease in polarizability is very small. Further, the optical absorption spectra and the corresponding optical gap have been calculated. The overall shape of the calculated spectra strongly depend on cluster geometries. With the increase in size, the discrete spectra of small clusters evolves into quasicontinuous spectra. For n = 10, the spectra show a smooth absorption edge that is a characteristic of the bulk. It is observed that the optical gap oscillate with an increase in the cluster size. The calculated optical gap of these clusters are lower than the band gap of α- and ß-Ga(2)O(3) phases. The underestimation of the calculated values of the cluster optical gap is due to the use of local density approximation.