Search results for "Surfaces"
showing 10 items of 2837 documents
Enhancement of the sub-band-gap photoconductivity in ZnO nanowires through surface functionalization with carbon nanodots
2018
We report on the surface functionalization of ZnO nanowire (NW) arrays by attachment of carbon nanodots (C-dots) stabilized by polyethylenimine. The photoconductive properties of the ZnO NWs/C-dots devices were investigated under photoexcitation with photon energies below and above the ZnO band gap. The results indicate an increased photoresponse of the functionalized devices in the visible spectral range, as well as enhanced UV photoconductivity. This is attributed to the fast injection of photoexcited electrons from the C-dots into the conduction band of the ZnO NWs, and the subsequent slower desorption of molecular species from the NW surface, which reduces the surface depletion region i…
Development of photocatalytically active heterostructured MnO/ZnO and CuO/ZnO films via solution precursor plasma spray process
2019
Abstract Heterostructured ZnO photocatalysts for the degradation of organic pollutant are mainly synthesized by conventional chemical methods, suffering from long duration, multi-steps, and post-treatment of the powder-formed catalysts after usage. In this paper, Solution Precursor Plasma Spray (SPPS) process is demonstrated to be a fast and efficient method for the one-step preparation of MnO/ZnO and CuO/ZnO heterostructured films for photocatalytic applications. The ratios between MnO or CuO and ZnO materials in the films were easily adjusted by varying the molar ratio of Mn(OAc)2 or Cu(OAc)2 relative to Zn(OAc)2 during the SPPS synthesis. To optimize the microstructure of selected CuO/Zn…
Ab initio hybrid DFT calculations of BaTiO3, PbTiO3, SrZrO3 and PbZrO3 (111) surfaces
2015
Abstract The results of ab initio calculations for polar BaTiO 3 , PbTiO 3 , SrZrO 3 and PbZrO 3 (111) surfaces using the CRYSTAL code are presented. By means of the hybrid B3LYP approach, the surface relaxation has been calculated for two possible B (B = Ti or Zr) or AO 3 (A = Ba, Pb or Sr) BaTiO 3 , PbTiO 3 , SrZrO 3 and PbZrO 3 (111) surface terminations. According to performed B3LYP calculations, all atoms of the first surface layer, for both terminations, relax inwards. The only exception is a small outward relaxation of the PbO 3 -terminated PbTiO 3 (111) surface upper layer Pb atom. B3LYP calculated surface energies for BaO 3 , PbO 3 , SrO 3 and PbO 3 -terminated BaTiO 3 , PbTiO 3 , …
Ab initio calculations of the atomic and electronic structure of MgF2 (011) and (111) surfaces
2011
Abstract The results of ab initio slab calculations of surface relaxations, rumplings and charge distribution for the different terminations of the MgF2 (011) and (111) polar surfaces are presented and discussed. We have employed the computer code CRYSTAL with the Gaussian basis set and the hybrid B3PW exchange-correlation functional. Despite the ionic nature of the chemical bonding at both surfaces, a considerable decrease of the optical band gap is predicted (1.3 eV or 10%) for the (111) surface as compared to the bulk.
Novel 2D boron nitride with optimal direct band gap: A theoretical prediction
2022
Abstract A novel structurally stable 2D-boron nitride material, namely di-BN, is predicted by means of the first-principles simulations. This monolayer BN system is composed of the azo (N-N) and diboron (B-B) groups. Its in-plane stiffness is close to the monolayer h-BN. Usually, the boron nitride materials are semiconductors with large band gaps. However, the monolayer di-BN possesses a moderate direct band gap of 1.622 eV obtained from our HSE06 calculation. Although the GW correction enlarges the band gap to 2.446 eV, this value is still in the range of the visible light. The detailed investigation of its band arrangement reveals that this material is able to product hydrogen molecules i…
Random Structural Modification of a Low-Band-Gap BODIPY-Based Polymer
2017
International audience; A BODIPY thiophene polymer modified by extending conjugation of the BODIPY chromophore is reported. This modification induces tunability of energy levels and therefore absorption wavelengths in order to target lower energies.
Microhardness and adhesion measurements of reactively sputtered TiN/AlN multilayer coatings deposited as function of mass-flow of nitrogen
1998
Abstract Multilayer coatings of (Ti, Al)N x have been deposited by reactive sputtering from Ti and Al targets in a side-by-side configuration on WC and stainless steel substrates. The rotation of the substrate holder varied from 2 to 14 r.p.m. corresponding to a bilayer thickness of 0.8–8 nm. The acoustic emission scratch technique for adhesion measurements was used for studying coating performance, and critical load values for the coatings on WC substrate up to 150 N were obtained. The Vickers microhardness in the load range 0.003–2 N was measured, and in order to obtain true hardness values, an optimal range of indentation depth and coating thickness was determined. Depending on the nitro…
Logic gates using nanofluidic diodes based on conical nanopores functionalized with polyprotic acid chains.
2009
Single-track conical nanopores functionalized with polyprotic acid chains have pH-sensitive fixed charge groups and show three levels of conductance that allow integrating several functions on a single nanofluidic diode. Nanometer-scaled pores have previously been employed in separation and sensing but not in logic devices, despite the fact that biological ion channels with pH-dependent fixed charges are known to be responsible for information processing in biophysical structures. As a preliminary application, we propose a logic gate scheme where binary and multivalued logical functions are implemented.
Halloysite Nanotubes: Interfacial Properties and Applications in Cultural Heritage
2020
The peculiar surfaces of halloysite nanotubes and their biocompatibility are attracting the interest of researchers based on the wide range of attainable applications. The large aspect ratio of this nanotubular material ensures promising properties as a reinforcing agent in polymeric matrixes, such as cellulose and its derivatives, that entail strengthening due to, for instance, aging-induced degradation. The halloysite cavity has a suitable size for hosting a large variety of active species such as deacidifying (calcium hydroxide) and flame retardant agents (fluorinated surfactants) for a controlled and sustained release relevant to the conservation of cultural heritage. Additionally, anio…
Proteins in amorphous saccharide matrices: Structural and dynamical insights on bioprotection
2013
Bioprotection by sugars, and in particular trehalose peculiarity, is a relevant topic due to the implications in several fields. The underlying mechanisms are not yet clearly elucidated, and remain the focus of current investigations. Here we revisit data obtained at our lab on binary sugar/water and ternary protein/sugar/water systems, in wide ranges of water content and temperature, in the light of the current literature. The data here discussed come from complementary techniques (Infrared Spectroscopy, Molecular Dynamics simulations, Small Angle X-ray Scattering and Calorimetry), which provided a consistent description of the bioprotection by sugars from the atomistic to the macroscopic …