The adsorption of the H2S molecule on the undoped and N-doped TiO2 anatase supported Au nanoparticles were studied using density functional theory calculations. The adsorption of H2S on both Au and TiO2 sides of the nanoparticle was examined. On the TiO2 side, the fivefold coordinated titanium site was found to be the most favorable binding site, giving rise to the strong interaction of H2S with TiO2 supported Au overlayer. It was found that the central sulfur atom of the H2S molecule preferentially binds to the fivefold coordinated titanium sites via formation of strong chemical bonds. By substituting nitrogen atom into the oxygen vacancy of TiO2, significant changes in the bond lengths, bond angles and adsorption energies of the complex systems occur. The adsorption of H2S on the N-doped TiO2-supported Au nanoparticle is more favorable in energy than the adsorption on the pristine one, indicating the strong interaction of H2S with N-dopedTiO2-supported Au. Thus, the N-doped nanoparticle can be utilized as potentially efficient H2S gas detection device. The substantial overlaps between the projected density of states of the titanium and sulfur atoms indicate, the formation of a chemical bond between the nanoparticle and H2S molecule. This work not only proposes a theoretical basis for gas sensing behaviors of TiO2- supported Au overlayers, but also provides an effective strategy for the development of innovative sensor devices for H2S recognition in the environment. پرونده مقاله

The density functional theory (DFT) calculations were used to get information concerning the interaction of curcumin on the pristine and N-doped TiO2 anatase nanoparticles. Three adsorption geometries of curcumin over the TiO2 anatase nanoparticles were studied in order to fully exploit the sensing properties of TiO2 nanoparticles. Curcumin molecule adsorbs on the fivefold coordinated titanium sites of the TiO2 nanoparticle because of the higher affinity of these sites with respect to the curcumin molecule. A preferred perpendicular adsorption of curcumin on the OC-substituted nanoparticle was found to be the most favorable conformation with the estimated adsorption energy of about -5.33 eV. The results suggest that the curcumin molecule favorably interacts with the N-doped TiO2 nanoparticle, that is, the interaction of curcumin with the pristine nanoparticle is less favorable in energy than the interaction with the N-doped one. The structural parameters such bond lengths/angles and adsorption energies were examined for the discussion of results. The electronic structures of the system were analyzed in view of the density of states and molecular orbitals. The analysis of projected density of states and molecular orbitals showed forming new chemical bonds between the nanoparticle and curcumin molecule. By including vdW interactions, the adsorption energies of the most stable curcumin+TiO2 couples were increased, implying the dominant effect of dispersion energy. پرونده مقاله

Density functional theory calculations were performed to investigate vitamin C interaction with N-doped TiO2 anatase nanoparticles. The adsorption of vitamin C on the energy favorable fivefold coordinated titanium sites was investigated. Various adsorption geometries of vitamin C towards the nanoparticle were examined. Since the adsorption energies of N-doped nanoparticles are higher than those of undoped ones, the N-doped TiO2 nanoparticles can interact with vitamin C molecule more strongly. Besides, adsorption on the pristine nanoparticle is less favorable, whereas on the N-doped one, the adsorption process is more energy favorable. The electronic structure analysis was performed in view of the density of states and molecular orbitals of the considered nanoparticles with adsorbed vitamin C molecule. The significant overlaps between the PDOS spectra of the oxygen atom of vitamin C molecule and titanium atom of TiO2 confirm the chemisorption of vitamin C on the TiO2 nanoparticle. After the adsorption, the electronic densities in the HOMOs of the adsorption systems were mainly distributed over the vitamin C molecule, while the LUMOs were dominant at the TiO2 nanoparticle. Our calculations shed light on the understanding the interaction between vitamin C and TiO2 nanoparticles, which provides an efficient outline for future experimental studies. پرونده مقاله

The density functional theory (DFT) calculations were used to get information concerning the interaction of curcumin with pristine and N-doped TiO2 anatase nanoparticles. Three adsorption geometries of curcumin over the TiO2 anatase nanoparticles were studied in order to fully exploit the sensing properties of TiO2 nanoparticles. Curcumin molecule adsorbs on the fivefold coordinated titanium sites of the TiO2 nanoparticle because of the higher affinity of these sites with respect to the curcumin molecule. A preferred perpendicular adsorption of curcumin on the OC-substituted nanoparticle was found to be the most favorable conformation with the estimated adsorption energy of about -5.33 eV. The results suggest that the curcumin molecule favorably interacts with the N-doped TiO2 nanoparticle, that is, the interaction of curcumin with the pristine nanoparticle is less favorable in energy than the interaction with the N-doped one. The structural parameters such as bond lengths/angles and adsorption energies were examined for the discussion of results. The electronic structures of the system were analyzed in view of the density of states and molecular orbitals. The analysis of projected density of states and molecular orbitals showed forming new chemical bonds between the nanoparticle and curcumin molecule. By including vdW interactions, the adsorption energies of the most stable curcumin+TiO2 couples were increased, implying the dominant effect of dispersion energy. پرونده مقاله

Solar energy reserving and conversion into usable chemical energy withsemiconductor photocatalysts help a promising method to solve both energy andenvironmental issues. Green and efficient energy technologies are crucial wherenanoscience could change the paradigm shift from fossil fuels to renewablesources. One of the most attractive cases is solar energy utilization to earnelectricity or chemical fuel based on semiconductor nanomaterials' ability tofunction as photocatalysts promoting various oxidation and reduction reactionsunder sunlight. Recently, two-dimensional (2D) materials have attracted particularfocus because of their charming properties. We report on a novel class of twodimensionalphotocatalysts for hydrogen generation via water splitting. In thispaper, by Density Functional Theory (DFT) calculations, we investigated Hf2CO2 astwo-dimensional transition metal carbides, referred to as MXene, to understandits photocatalytic properties. Using this method, we theoretically investigatedthe structural, electronic, and optical properties of MXene-based nanostructuressuch as Hf2CO2 that were calculated using GGA-PBE and HSE06 functionals. The latticeconstant for GGA-PBE functional for Hf2CO2 is 3.3592A°. The calculated band gapsfor GGA-PBE and HSE06 functionals for two-dimensional Hf2CO2 MXene were 0.92and 1.75 eV, respectively. This MXene-based nanostructure also exhibits excellentoptical absorption performance. Hence, Hf2CO2 is a promising photocatalyticmaterial. پرونده مقاله

Quantum transport properties of pure and functioned infinite lead-connection region-lead systembased on the zigzag graphene nanoribbon (2-zGNR) have been investigated. In this work the effectof the doping functionalization on the quantum transport of the 2-zGNR has been computationallystudied. Also, the effect of the imposed gate voltages (-3.0, 0.0 and +3.0 V) and bias voltages 0.0 to2.0 V have been studied. The results were presented as the current versus the bias voltage (I-Vb)curves with unique properties for per studied systems, showing one or two negative differentialresistances (NDR). The NDR region was discussed and interpreted in the terms of the transmissionspectrum and its integral inside of the corresponding bias window. Also, the partial atomic chargedistribution in the center part of the system’s scattering region containing carbon atoms at the leftand right sides of substituted atoms which are connected to substituted atoms has been investigatedfor different bias voltages. پرونده مقاله