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J Phys Condens Matter ; 31(50): 505502, 2019 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-31470438


A large ferroelectric (FE) polarization and low bandgap are essential to improving the bulk photovoltaic response which is the generation of photocurrent in the polar non-centrosymmetric materials such as FE perovskite oxides. Among various perovskite oxides, Potassium Niobate (KNbO3, KNO) is a promising FE material for bulk photovoltaic applications as its bandgap and polarization can be tuned effectively by strain, doping, or by applying an electric field. In this work, using the density functional theory calculations, we present an insight into the strain engineering of polarization, band structure, and optical properties of the cubic (C), tetragonal (T), and orthorhombic (O) structures of KNO. The tensile and compressive strain under the triaxial, biaxial, and uniaxial conditions are applied along the direction parallel and perpendicular to the polar axis of KNO structures. We find that the bandgap decreases along with a substantial increment of polarization on the application of tensile strain along the direction parallel to the polar axis. In T (O) phase at +2% strain, the polarization increases by 18 µC cm-2 (14 µC cm-2) in triaxial, 26 µC cm-2 (16 µC cm-2) in biaxial, and 29 µC cm-2 (29 µC cm-2) in uniaxial conditions with a considerable decreasing of bandgap with respect to zero strain condition. Therefore, wisely applying the tensile strain along the direction parallel to the polar axis, the photovoltaic efficiency of KNO can be improved.

Nanomaterials (Basel) ; 9(3)2019 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-30857307


The mesoporous La-Na co-doped TiO2 nanoparticles (NPs) have been synthesized by non-aqueous, solvent-controlled, sol-gel route. The substitutional doping of large sized Na+1 and La+3 at Ti4+ is confirmed by X-ray diffraction (XRD) and further supported by Transmission Electron Microscopy (TEM) and X-ray Photo-electron Spectroscopy (XPS). The consequent increase in adsorbed hydroxyl groups at surface of La-Na co-doped TiO2 results in decrease in pHIEP, which makes nanoparticle surface more prone to cationic methylene blue (MB) dye adsorption. The MB dye removal was examined by different metal doping, pH, contact time, NPs dose, initial dye concentration and temperature. Maximum dye removal percentage was achieved at pH 7.0. The kinetic analysis suggests adsorption dynamics is best described by pseudo second-order kinetic model. Langmuir adsorption isotherm studies revealed endothermic monolayer adsorption of Methylene Blue dye.

Front Microbiol ; 7: 144, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26904017


Vibrio cholerae is an aerobic, sucrose fermentative Gram-negative bacterium that generally prevails in the environment. Pathogenic V. cholerae is well-known as causative agent of acute diarrhea. Apart from enteric infections, V. cholerae may also cause other diseases. However, their role in causing extraintestinal infections is not fully known as it needs proper identification and evaluation. Four cases of extraintestinal infections due to V. cholerae non-O1/non-O139 have been investigated. The isolates were screened for phenotypic and genetic characteristics with reference to their major virulence genes. Serologically distinct isolates harbored rtx, msh, and hly but lacked enteric toxin encoding genes that are generally present in toxigenic V. cholerae. Timely detection of this organism can prevent fatalities in hospital settings. The underlying virulence potential of V. cholerae needs appropriate testing and intervention.

J Colloid Interface Sci ; 445: 337-347, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25643961


In the current contribution we report on investigations regarding the surface of CuInS2 quantum dots and on different strategies to control the amount of surface ligands in a post-processing step. In particular, the reactivity of the organic components, that is, 1-dodecanthiol and 1-octadecene as ligand and solvent, respectively, during nanocrystal formation was studied. A new method to remove residuals from the reaction mixture and to detach excess organics from the surface of the nanocrystals is reported. Our new method, which is based on the utilization of acids, is compared with standard purification procedures by means of thermogravimetric analysis (TGA) with particular focus on its efficiency to remove organics. As a complement, the surface chemistry is analyzed by nuclear magnetic resonance spectroscopy (NMR) to shed light on the nature of the organic components still present after purification. Further analysis of the product by inductively coupled plasma optical emission spectroscopy (ICP-OES) is performed to verify the influence of the new purification method on surface composition and properties. Moreover, steady state and time resolved spectroscopies give insights into excitonic behavior as well as recombination processes. Finally, the new method is optimized for the purification of CuInS2-ZnS nanocrystals, which show enhanced optical properties.

ACS Nano ; 4(2): 1099-107, 2010 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-20112922


A nanofabrication technique combining pulsed laser deposition and a nanoporous anodic aluminum oxide membrane mask is being proposed to prepare various types of multiferroic nanocomposites, viz. periodically ordered CoFe(2)O(4) dots covered by a continuous Pb(Zr,Ti)O(3) layer, Pb(Zr,Ti)O(3) dots covered with CoFe(2)O(4), and Pb(Zr,Ti)O(3)/CoFe(2)O(4) bilayer heterostructure dots. By properly tuning the processing parameters, epitaxial nanodot-matrix composites can be obtained. For the composite consisting of CoFe(2)O(4) nanostructures covered by a Pb(Zr,Ti)O(3) film, an unexpected out-of-plane magnetic easy axis induced by the top Pb(Zr,Ti)O(3) layer and a uniform microdomain structure can be observed. The nanocomposites tested by piezoresponse force microscopy (PFM) exhibit strong piezoelectric signals, and they also display magnetoelectric coupling revealed by magnetic-field dependent capacitance measurement.

J Am Chem Soc ; 132(5): 1478-9, 2010 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-20078123


We report a process for the fabrication of an anatase TiO(2) mesosponge (TMS) layer by an optimized Ti anodization process in a hot glycerol electrolyte followed by a suitable etching process. Such layers can easily be grown to >10 microm thickness and have regular channels and structural features in the 5-20 nm range. The layers show high photocatalytic activity and are mechanically very robust. The layers therefore open new pathways to the wide field of TiO(2)(anatase) applications.