Color-tunable up-conversion emission in Y2O3:Yb3+, Er3+ nanoparticles prepared by polymer complex solution method

Powders of Y2O3 co-doped with Yb3+ and Er3+ composed of well-crystallized nanoparticles (30 to 50 nm in diameter) with no adsorbed ligand species on their surface are prepared by polymer complex solution method. These powders exhibit up-conversion emission upon 978-nm excitation with a color that can be tuned from green to red by changing the Yb3+/Er3+ concentration ratio. The mechanism underlying up-conversion color changes is presented along with material structural and optical properties

Synthesis of CdIn2S4 mesocrystals

Ternary nanosized sulfide CdIn2S4was synthesized using hot-injectionmethod in oleic acid/oleylamine mixture as reaction media at 270ºC. TEM images have shown that obtained material grows through multistep process, forming marigold structures built out from mesocrystals. Influence of oleic acid and oleic acid/oleylaminemixture as reaction media on mesocrystal formation is tracked and discussed.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 201

The influence of reaction media on CdIn2S4 and ZnIn2S4 nanocrystallite formation and growth of mesocrystal structures

A hot-injection method for the synthesis of CdIn2S4 in three different compositions of organic media/solvents was studied. Nanosized CdIn2S4 is successfully synthesized in an oleic acid/oleylamine mixture of complexing/capping agents. The obtained mesocrystals of 20-30 nm in diameter are self-organized in marigold-like structures. The estimated band-gap of synthesized semiconductor is in the visible spectral region and has a value of about 2.1 eV. The potential of the band edges is calculated using an empirical equation. The as-prepared material was successfully transferred from organic to aqueous media by using 2-mercaptoethanol in a surface ligand exchange process. Using a similar synthetic procedure, ZnIn2S4 synthesis was performed. The obtained materials were characterized using UV/vis spectroscopy, XRD and TEM. Formation and growth mechanisms of the synthesized materials are proposed

Nanoparticle shape and configuration analysis by transmission electron tomography

Tomographic reconstruction by transmission electron microscopy is used to reveal three-dimensional nanoparticle shapes and the stacking configurations of nanoparticle ensembles. Reconstructions are generated from bright-field image tilt series, with a sample tilt range up to +/- 70 degrees, using single or dual tilt axes. We demonstrate the feasibility of this technique for the analysis of nanomaterials, using appropriate acquisition conditions. Tomography reveals both cubic and hexagonal close-packing configurations in multi-layered arrays of size-selected In nanospheres. By tomography and phase-contrast lattice imaging, we relate the three-dimensional shape of PbSe octahedral nanoparticles to the underlying crystal structure. We also confirm simple-cubic packing in multi-layers of PbSe nanocubes and see evidence that the particle shapes have cubic symmetry. The shapes of TiO(2) nanorod bundles are shown by tomographic reconstruction to resemble flattened ellipsoids

Electrocatalityc application of gold-polyaniline nanocomposite

Gold‒polyaniline (AuPANI) nanocomposite, with granular morphology of PANI and rod‒like Au nanoparticles (NPs) as dominate structure distributed in it, was prepared by interfacial polymerization method in an immiscible water/toluene biphasic system. Simultaneously with the aniline polymerization to polyaniline (PANI) by HAuCl4, as an oxidant, AuNPs are formed. AuPANI composite as green precipitate is collected from aqueous phase. Polyaniline in the composite is in the conductive emeraldine salt form (PANIES), with high amount of Au (28.85 wt %). Nanocomposite showed great electrocatalytic activity towards the electrochemical O2reduction reaction (ORR), with high ORR onset potential and high selectivity for O2reduction to water. This makes it a good candidate for a new class of Pt‒free ORR catalyst.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 2016

The antimicrobial activity of triangular silver nanoplates on cotton fabric pretreated with chitozan

Triangular silver nanoplates are a type of most-studied noble-metal nanostructures over the past decade, owing to their special structural architecture, outstanding plasmonic features across both visible and IR regions, and catalytic properties for a wide range of applications. Herein, we used these nanoparticles to deposit on cotton (Co) fabric pretreated with biopolymer chitosan (CHT) and investigated their antimicrobial activity. The antimicrobial efficiency of the coated fabrics was evaluated toward Gram-negative bacteria E. coli, Gram-positive bacteria S. aureus and fungus C. albicans. It was found that deposited silver nanoparticles imparted excellent antimicrobial properties to Co fabric

Yb3+, Er3+ doped Y2O3 nanoparticles of different shapes prepared by self-propagating room temperature reaction method

In this report, a cost- and time-effective method for synthesis of Y2O3:Yb3+, Er3+ nanoparticles that exhibit up-conversion emission under infrared excitation is presented. The synthesis method is based on the self-propagating, room-temperature reaction between metal nitrates and sodium hydroxide, and a subsequent calcination process. Series of samples were prepared with calcinations at various temperatures (600 degrees C, 800 degrees C and 1100 degrees C) for 1 h, and also with different Yb3+-Er3+ ratios (10:1, 5:1 and 2:1). All calcined samples crystallized in a cubic bixbyite crystal phase with crystallite size from 12 to 44 nm in diameter, for samples calcined at 600 degrees C and 1100 degrees C, respectively. Different nanoparticle morphologies were obtained after calcinations on different temperatures; at temperatures under 1100 degrees C rod-like particles were obtained, while at 1100 degrees C spherical particles were formed. In all samples up-conversion emissions and corresponding lifetimes were measured after excitation in room temperature at 978 nm. The most intense emission originates from the characteristic intra-shell f-f electronic transitions of Er3+ ions: [2H(9/2)- GT I-4(15/2)] in blue (407-420 nm); [(H-2(11/2), S-4(3/2))- GT I-4(15/2)] green: 510-590 nm; and [F-4(9/2)- GT I-4(15/2)] in red (640-720 nm) spectral regions. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Non-contact thermometry with Dy3+ doped Gd2Ti2O7 nano-powders

The performance of Dy3+ doped Gd2Ti2O7 nano-powders for luminescence temperature sensing was tested over a temperature range from 293 to 443 K. The Dy3+ ions were incorporated into Gd2Ti2O7 nanocrystals using a hydrolytic sal-gel route. Microstructural characterization of the obtained material was performed using transmission electron microscopy and X-ray diffraction measurements. Luminescence spectra of Dy3+ doped Gd2Ti2O7 nano-powders consists of two distinct spectral regions: the highenergy region associated with the trap emission of the Gd2Ti2O7 host and the low-energy region with well-resolved emission peaks of the Dy3+ ions. The ratio between intensities of two Dy3+ emission lines, as well as the ratio between intensities of trap emission of host and Dy3+ emission show strong temperature dependence and are tested for temperature sensing. In both cases, ratiometric measurements provide comparable quality of temperature sensing, and when they are combined the relative sensor sensitivities were found to be higher than 0.9% K-1 over given temperature range. The fluorescence quenching of Dy3+ ions was discussed in terms of simple theoretical models. (C) 2015 Elsevier B.V. All rights reserved

Structural and morphological dependences of Sb2S3 nanobars synthesised by organo-colloidal process on precursor concentrations and reaction times

In this paper we report the synthesis of antimony sulphide (Sb2S3) nanobars performed using a simple organo-colloidal synthetic method. The as-synthesised Sb2S3 nanobars with various precursor concentrations and heating times showed differences in the morphology (open and enclosing forms) and structural parameters. UV-vis absorption measurements revealed that the optical band gap energies lay in the red part of the solar spectrum. The observed band gap energies, of nearly the same values (similar to 1.6 eV), proved that precursor concentrations and heating times had no effect on them. The structure refinement showed that the Sb2S3 powder belonged to the orthorhombic type with a space group Pbnm. It was found that Sb2S3 nanobars predominantly grew along the [010] direction, and that the unit cell parameters and the preferred orientation parameter (tau) refined against experimental data were quite dependent on both the precursor concentration and the heating time. The optimum heating time to nicely follow the dependence of structural parameters on the precursor concentration was observed. (C) 2012 Elsevier B.V. All rights reserved