Jovan M. Nedeljković

TiO2 films prepared by ultrasonic spray pyrolysis of nanosize precursor

Abstract A methodology for the preparation of the TiO 2 films, based on the process of ultrasonic spray pyrolysis and usage of TiO 2 nanoparticles, with the mean diameter of 45 A as a precursor, was developed. The X-ray diffraction (XRD) analysis of the TiO 2 films revealed the appearance of rutile phase at 620 °C. Morphology of the TiO 2 films deposited at different temperatures on titanium substrates was investigated by scanning electron microscopy (SEM). The SEM analysis revealed that morphology of the TiO 2 films can be adjusted by temperature. It seems that the process of ultrasonic spray pyrolysis provides an easy way to prepare either compact smooth films or films with a porous structure.

Influence of CdS-filler on the thermal properties of polystyrene

Influence of CdS-filler particles in the micrometer size range on the properties of the polystyrene (PS) matrix was studied using structural and thermal techniques. Improvement of the thermal stability of the PS matrix for about 50 K was found in the presence of the CdS-filler. Infrared measurements revealed that interaction between the surface of CdS-filler particles and the PS chain is weak. Non-significant changes in the glass transition temperature of the PS matrix upon the incorporation of CdS-filler particles also suggest weak interaction between filler and polymer.

Surface modification of anatase nanoparticles with fused ring catecholate type ligands: a combined DFT and experimental study of optical properties

Surface modification of nanocrystalline TiO(2) particles (45 Å) with catecholate-type ligands consisting of an extended aromatic ring system, i.e., 2,3-dihydroxynaphthalene and anthrarobin, was found to alter the optical properties of the nanoparticles in a similar way to modification with catechol. The formation of inner-sphere charge-transfer (CT) complexes results in a red shift of the semiconductor absorption compared to unmodified nanocrystallites and the reduction of the band gap upon the increase of the electron delocalization on the inclusion of additional rings. The binding structures were investigated by FTIR spectroscopy. The investigated ligands have the optimal geometry for binding to surface Ti atoms, resulting in ring coordination complexes of catecholate type (binuclear bidentate binding-bridging) thus restoring the six-coordinated octahedral geometry of surface Ti atoms. From the Benesi-Hildebrand plot, stability constants in methanol/water = 90/10 solutions at pH 2 of the order 10(3) M(-1) have been determined. Quantum chemical calculations on model systems using density functional theory (DFT) were performed to obtain vibrational frequencies of charge transfer complexes, and the calculated values were compared with the experimental data.

Ultrasonic spray pyrolysis of TiO2 nanoparticles

Abstract Synthesis of ultrafine spherical TiO 2 particles was achieved by using ultrasonic spray pyrolysis and nanoparticles of TiO 2 (≈2.5nm) as a precursor. The size distribution and morphology of TiO 2 particles obtained after ultrasonic spray pyrolysis were characterized by SEM and STM. Agreement between experimentally obtained results and theoretical calculation of particle size was found.

Self-referenced luminescence thermometry with Sm3+ doped TiO2 nanoparticles

The performance of Sm(3+) doped TiO2 nanoparticles for luminescence temperature sensing was tested over a temperature range from room to 110 °C. The Sm(3+) ions were incorporated into TiO2 nanocrystals using hydrolytic sol-gel route. Microstructural characterization of the obtained material was performed using transmission electron microscopy and x-ray diffraction measurements. Luminescence emission spectra of Sm(3+) doped TiO2 nanoparticles consists of two distinct spectral regions: the high energy region associated with the trap emission of the TiO2 host, and the low energy region with well-resolved emission peaks of the Sm(3+) ions. The ratio between Sm(3+) emission and TiO2 trap emission shows strong temperature dependence, and is tested for temperature sensing. The relative sensor sensitivity was found to be higher than 1% °C(-1) over given temperature range with the maximum value of 10.54% °C(-1) at 57.5 °C. Lifetime data derived from the Sm(3+) emission decay revealed that time-resolved measurements provide comparable quality of temperature sensing as corresponding ratiometric measurements, with a maximum relative sensitivity of 10.14% °C(-1) at 66.5 °C.

Influence of additives on the properties of spherical nickel particles prepared by ultrasonic spray pyrolysis

S. Stopic, J. Nedeljkovic, Z. Rakocevic and D. Uskokovic Journal of Materials Research / Volume 14 / Issue 07 / 1999, pp 3059 xad 3065 DOI: 10.1557/JMR.1999.0410 Link to this article: http://journals.cambridge.org/abstract_S088429140005113X How to cite this article: S. Stopic, J. Nedeljkovic, Z. Rakocevic and D. Uskokovic (1999). Influence of additives on the properties of spherical nickel particles prepared by ultrasonic spray pyrolysis. Journal of Materials Research,14, pp 3059xad3065 doi:10.1557/JMR.1999.0410 Request Permissions : Click here

Synthesis, characterization, and antimicrobial activity of poly(GMA-co-EGDMA) polymer decorated with silver nanoparticles

Composite consisting of silver nanoparticles coordinated to poly(GMA-co-EGDMA) macroporous copolymer was prepared by attachment of amino group to the poly(GMA-co-EGDMA) in the reaction with ethylene diamine, and consequent reduction of silver ions with amino groups at elevated temperature. The infrared measurements indicated that surface of silver nanoparticles is passivated through the coordination of the lone pair on the N atom of the imine present in the skeleton of the poly(GMA-co-EGDMA) copolymer. The inductively coupled plasma atomic emission, UV–Vis reflection spectroscopy, X-ray diffraction, and transmission electron microscopy measurements revealed the high content (52xa0wt%) of well-separated silver nanoparticles in the size range of 5–10xa0nm onto composite. Antimicrobial efficiency of composite was tested against Gram-negative bacteria E. coli, Gram-positive bacteria S. aureus, and fungus C. albicans in wide concentration range of composite. The composite ensured almost maximum reduction of both bacteria, while the fungi reduction reached 96.5xa0%.

Surface modification of submicronic TiO 2 particles prepared by ultrasonic spray pyrolysis for visible light absorption

Spherical, submicronic TiO2 assemblage with high specific surface area and controllable phase composition was prepared in the process of ultrasonic spray drying/pyrolysis in a wide temperature range (150–800xa0°C) by using as a precursor aqueous colloidal solution consisting of TiO2 nanoparticles (4.5xa0nm). Submicronic, soft and grained spherical TiO2 particles (dxa0=xa0370–500xa0nm) comprising clustered nanocrystals (<10xa0nm) were obtained at low processing temperature, while particle densification, intensive growth of the clustered primary units and anatase-to-rutile transformation (~30xa0wt%) were observed at the higher temperatures. Detailed structural and morphological characterisation were performed by X-ray powder diffraction, scanning and field emission electron microscopy, transmission electron microscopy, and laser particle size analysis. Moreover, the surface modification of TiO2 particles through the formation of charge-transfer (CT) complex was achieved with different ligands: ascorbic acid, dopamine, catechol, 2,3-dihydroxynaphthalene, and anthrarobin. Optical properties of the surface-modified TiO2 particles were studied by using diffuse reflection spectroscopy. The binding structure between the surface titanium atoms and different ligands was determined by using Fourier transform infrared spectroscopy. The formation of CT complexes induced significant red shift of optical absorption in comparison to unmodified TiO2 particles.

Tailor made synthesis of Q-TiO2 powder by using quantum dots as building blocks

Abstract A simple synthetic procedure based on ultrasonic spray pyrolysis and usage of TiO 2 quantum dots as building blocks leads to the formation of submicronic TiO 2 spheres which preserved optical and catalytic properties of the constituting elements. The methodology is not limited to semiconductor quantum dots, but provides general procedures for the rational design of novel and potentially useful composite materials.

In situ generation of Ag nanoparticles on polyester fabrics by photoreduction using TiO 2 nanoparticles

This study discusses the possibility of in situ generation of Ag nanoparticles on polyester fabric by photoreduction of Ag+ ions with deposited TiO2 nanoparticles in the presence of amino acid alanine and methyl alcohol. The presence of TiO2/Ag nanoparticles on the polyester fiber surface was confirmed by XRD, XPS, and SEM analyses. Such nanocomposite textile material provides excellent antimicrobial activity against Gram-negative bacterium E. coli, Gram-positive bacterium S. aureus, and fungus C. albicans. Maximum microbial reduction was preserved even after ten washing cycles. In spite of satisfactory laundering durability, the release of silver occurred during washing. The leaching of silver was also present when the fabrics were exposed to artificial sweat at pH 5.5 and pH 8.0 for 24xa0h. In addition to excellent antimicrobial properties, TiO2/Ag nanoparticles imparted maximum UV protection to polyester fabrics.