Synthesis and characterization of monodispersed water dispersible Fe3O4 nanoparticles and in vitro studies on human breast carcinoma cell line under hyperthermia condition.

Monodispersed Fe3O4 magnetic nanoparticles (MNPs) having size of 7 nm have been prepared from iron oleate and made water dispersible by functionalization for biomedical applications. Three different reactions employing thioglycolic acid, aspartic acid and aminophosphonate were performed on oleic acid coated Fe3O4. In order to achieve a control on particle size, the pristine nanoparticles were heated in presence of ferric oleate which led to increase in size from 7 to 11 nm. Reaction parameters such as rate of heating, reaction temperature and duration of heating have been studied. Shape of particles was found to change from spherical to cuboid. The cuboid shape in turn enhances magneto-crystalline anisotropy (Ku). Heating efficacy of these nanoparticles for hyperthermia was also evaluated for different shapes and sizes. We demonstrate heat generation from these MNPs for hyperthermia application under alternating current (AC) magnetic field and optimized heating efficiency by controlling morphology of particles. We have also studied intra-cellular uptake and localization of nanoparticles and cytotoxicity under AC magnetic field in human breast carcinoma cell line.

Oleylamine as a reducing agent in syntheses of magic-size clusters and monodisperse quantum dots: optical and photoconductivity studies.

Separation of magic size clusters (MSCs) from monodisperse quantum dots (QDs) has generally been a difficult task while employing the commonly used synthesis procedure, where for preparation of PbSe QDs, Se-TOP (TOP = trioctylphosphine) is injected into Pb-oleate in 1-octadecene medium. In this study, we report for the first time a simple method to prepare MSCs, QDs and particles close to the bulk of PbSe using oleylamine (OAM) as the reducing agent, where the individual entities are efficiently separated. The chemical yield is found to be 95%. Studies on optical properties revealed the absorption and emission peaks of MSCs at fixed positions of 600 and 780 nm, respectively, while QDs exhibit significant shift to longer wavelengths for both the cases, depending on the particle size. Shift of the emission peak position for QDs is observed to be larger for initial stages of the waiting time as compared to those for longer waiting times. This can be attributed to two factors: faster growth in particle size is favoured kinetically in the initial stages, while thermodynamic stability occurs in the later stages, and reduction in surface to core contribution with increase of waiting time. QDs were found to emit at only one particular wavelength while they absorbed at two or more wavelengths. The quantum yields (QYs) of particles of sizes 4.1 and 5.1 nm are found to be 80 and 30%, respectively. The lifetime values are found to be 1.0-1.3 µs for QDs having an emission peak in the range of 1300-1500 nm. The hybrid device of PbSe (5 nm size) and MEHPPV (2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) shows increased conductivity both in the dark and in light, due to absorption in the region of NIR photons in the former and additionally in the visible region in the latter.

Covalent bridging of surface functionalized Fe3O4 and YPO4:Eu nanostructures for simultaneous imaging and therapy.

Magnetic luminescent hybrid nanostructures (MLHN) have received a great deal of attention due to their potential biomedical applications such as thermal therapy, magnetic resonance imaging, drug delivery and intracellular imaging. We report the development of bifunctional Fe3O4 decorated YPO4:Eu hybrid nanostructures by covalent bridging of carboxyl PEGylated Fe3O4 and amine functionalized YPO4:Eu particles. The surface functionalization of individual nanoparticulates as well as their successful conjugation was evident from Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), zeta-potential and transmission electron microscopy (TEM) studies. X-ray diffraction (XRD) analysis reveals the formation of highly crystalline hybrid nanostructures. TEM micrographs clearly show the binding/anchoring of 10 nm Fe3O4 nanoparticles onto the surface of 100-150 nm rice grain shaped YPO4:Eu nanostructures. These MLHN show good colloidal stability, magnetic field responsivity and self-heating capacity under an external AC magnetic field. The induction heating studies confirmed localized heating of MLHN under an AC magnetic field with a high specific absorption rate. Photoluminescence spectroscopy and fluorescence microscopy results show optical imaging capability of MLHN. Furthermore, successful internalization of these MLHN in the cells and their cellular imaging ability are confirmed from confocal microscopy imaging. Specifically, the hybrid nanostructure provides an excellent platform to integrate luminescent and magnetic materials into one single entity that can be used as a potential tool for hyperthermia treatment of cancer and cellular imaging.

Synthesis, characterization and biocompatibility of chitosan functionalized superparamagnetic nanoparticles for heat activated curing of cancer cells.

Surface functionalization, colloidal stability and biocompatibility of magnetic nanoparticles are crucial for their biological applications. Here, we report a synthetic approach for the direct preparation of superparamagnetic nanoparticles consisting of a perovskite LSMO core modified with a covalently linked chitosan shell that provides colloidal stability in aqueous solutions for cancer hyperthermia therapy. The characterization of the core-shell nanostructure using Fourier transform infrared spectroscopy; thermo-gravimetric analysis to assess the chemical bonding of chitosan to nanoparticles; field-emission scanning electron microscopy and transmission electron microscopy for its size and coating efficiency estimation; and magnetic measurement for their magnetization properties was performed. Zeta potential and light scattering studies of the core shell revealed it to possess good colloidal stability. Confocal microscopy and MTT assay are performed for qualitative and quantitative measurement of cell viability and biocompatibility. In depth cell morphology and biocompatibility is evaluated by using multiple-staining of different dyes. The magnetic@chitosan nanostructure system is found to be biocompatible up to 48 h with 80% cell viability. Finally, an in vitro cancer hyperthermia study is done on the MCF7 cell line. During in vitro hyperthermia treatment of cancer cells, cell viability is reduced upto 40% within 120 min with chitosan coated nanoparticles. Our results demonstrate that this simplified and facile synthesis strategy shows potential for designing a colloidal stable state and biocompatible core shell nanostructures for cancer hyperthermia therapy.

Enhanced up-conversion and temperature-sensing behaviour of Er(3+) and Yb(3+) co-doped Y2Ti2O7 by incorporation of Li(+) ions.

Y2Ti2O7:Er(3+)/Yb(3+) (EYYTO) phosphors co-doped with Li(+) ions were synthesized by a conventional solid-state ceramic method. X-ray diffraction studies show that all the Li(+) co-doped EYYTO samples are highly crystalline in nature with pyrochlore face centred cubic structure. X-ray photon spectroscopy studies reveal that the incorporation of Li(+) ions creates the defects and/or vacancies associated with the sample surface. The effect of Li(+) ions on the photoluminescence up-conversion intensity of EYYTO was studied in detail. The up-conversion study under ∼976 nm excitation for different concentrations of Li(+) ions showed that the green and red band intensities were significantly enhanced. The 2 at% Li(+) ion co-doped EYYTO samples showed nearly 15- and 8-fold enhancements in green and red band up-converted intensities compared to Li(+) ion free EYYTO. The process involved in the up-conversion emission was evaluated in detail by pump power dependence, the energy level diagram, and decay analysis. The incorporation of Li(+) ions modified the crystal field around the Er(3+) ions, thus improving the up-conversion intensity. To investigate the sensing application of the synthesized phosphor materials, temperature-sensing performance was evaluated using the fluorescence intensity ratio technique. Appreciable temperature sensitivity was obtained using the synthesized phosphor material, indicating its applicability as a high-temperature-sensing probe. The maximum sensitivity was found to be 0.0067 K(-1) at 363 K.

Structured superparamagnetic nanoparticles for high performance mediator of magnetic fluid hyperthermia: synthesis, colloidal stability and biocompatibility evaluation.

Core-shell structures with magnetic core and metal/polymer shell provide a new opportunity for constructing highly efficient mediator for magnetic fluid hyperthermia. Herein, a facile method is described for the synthesis of superparamagnetic LSMO@Pluronic F127 core-shell nanoparticles. Initially, the surface of the LSMO nanoparticles is functionalized with oleic acid and the polymeric shell formation is achieved through hydrophobic interactions with oleic acid. Each step is optimized to get good dispersion and less aggregation. This methodology results into core-shell formation, of average diameter less than 40 nm, which was stable under physiological conditions. After making a core-shell formulation, a significant increase of specific absorption rate (up to 300%) has been achieved with variation of the magnetization (<20%). Furthermore, this high heating capacity can be maintained in various simulated physiological conditions. The observed specific absorption rate is almost higher than Fe3O4. MTT assay is used to evaluate the toxicity of bare and core-shell MNPs. The mechanism of cell death by necrosis and apoptosis is studied with sequential staining of acridine orange and ethidium bromide using fluorescence and confocal microscopy. The present work reports a facile method for the synthesis of core-shell structure which significantly improves SAR and biocompatibility of bare LSMO MNPs, indicating potential application for hyperthermia.

Enhanced photoluminescence in CaMoO4:Eu3+ by Gd3+ co-doping.

We have studied the luminescence property of CaMoO4:Eu(3+). The emission peaks at 590 ((5)D0→(7)F1) and 613 nm ((5)D0→(7)F2) for Eu(3+) are observed after excitation at 266 nm (i.e. Mo-O charge transfer band). The peak intensity of the latter dominates over the former indicating an asymmetric environment of Eu(3+) in EuO8 polyhedron or parity mixing. Luminescence intensity increases significantly with co-doping of Gd(3+). This is ascribed to energy transfer from Mo-O/Gd(3+) to Eu(3+). Luminescence intensity increases with annealing up to 900 °C due to the extent of decrease of non-radiative rates. Very high asymmetric values (A21) of 12-16 are found indicating a red emitter. As-prepared samples are dispersible in polar solvents like water, ethanol, methanol, dimethyl sulfoxide (DMSO) and ethylene glycol (EG); and among them, optimum luminescence is found in methanol. Polymer film shows red emission. The quantum yields of as-prepared 2 and 10 at% Gd(3+) co-doped CaMoO4:Eu(3+) under 277 nm (UV excitation) are 21 and 80%, respectively.

Influence of Gd3+ co-doping on structural property of CaMoO4:Eu nanoparticles.

A facile auto-combustion route is used for the synthesis of Gd(3+) (2, 5, 7 and 10 at%) co-doped CaMoO4:Eu nanoparticles. X-ray diffraction study suggests that as-prepared samples have extra impurity phases in addition to main tetragonal phase of CaMoO4, and such extra phases decrease as the annealing temperature increases from 600 to 900 °C. The crystal structure has been analysed using Rietveld program. It has space group I41/a (88) and Z = 4 (number of CaMoO4 formula units per unit cell). Average crystallite sizes of as-prepared, 600 and 900 °C annealed samples for 2 at% Gd(3+) are found to be ~33, 48 and 61 nm, respectively. The lattice strains of 5 at% Gd(3+) co-doped CaMoO4:Eu for as-prepared and 900 °C are 0.001 and 0.002, respectively. Fourier transform infrared spectroscopy gives the absorption bands at ~815 and 427 cm(-1), which are related to asymmetric stretching and bending vibrations of MoO4(2-) tetrahedron. Particle morphology is studied using scanning and transmission electron microscopy (SEM and TEM), and aggregation of particles is found. X-ray photoelectron spectroscopy (XPS) is utilized to examine the oxidation states of metal ions/oxygen and oxygen ion vacancies in Gd(3+) co-doped CaMoO4:Eu. With an increase in Gd(3+) concentration, peaks corresponding to the Gd(3+) (2p(3/2) and 2p(5/2)) binding energy could be detected.

Enhanced luminescence of CaMoO4:Eu by core@shell formation and its hyperthermia study after hybrid formation with Fe3O4: cytotoxicity assessment on human liver cancer cells and mesenchymal stem cells.

Highly water dispersible Eu³âº doped CaMoO4 nanoparticles (core) covered by CaMoO4 (shell) have been prepared using the polyol method. Significant enhancement in luminescence intensity by core@shell formation is observed due to the decrease of non-radiative rate arising from surface/defect of particles. Effect of 266 nm laser excitation (Mo-O charge transfer band) on the asymmetric ratio (A21 = intensity ratio of electric to magnetic dipole transitions) has been studied and compared with a xenon lamp source. Luminescence intensity increases with the increase of power at 532 nm laser excitation. In order to explore materials, which can show dual functionalities such as luminescence as well as magnetic properties (magnetization of ∼14.2 emu g⁻¹), water dispersible Fe3O4-CaMoO4:Eu hybrid magnetic nanoparticles (MN) have been prepared. This shows good heating ability up to ∼42 °C (hyperthermia) and luminescence in the red region (∼612 nm), which is in a biological window (optical imaging). Biocompatibility of the synthesized Fe3O4-CaMoO4:Eu hybrid magnetic nanoparticles has been evaluated in vitro by assessing their cytotoxicity on human liver cancer cells (HepG2 cells) and hTERT cells using the MTT assay and fluorescent microscopy studies.

Enhanced colloidal stability of polymer coated La0.7Sr0.3MnO3 nanoparticles in physiological media for hyperthermia application.

Surface of La(0.7)Sr(0.3)MnO3 (LSMO) magnetic nanoparticles (MNPs) is functionalized with polymer (dextran) and their colloidal stability in various mediums is carried out. The influence of the surface functionalization of LSMO MNPs on their colloidal stability in physiological media is studied and correlated with their hyperthermia properties. Many studies have concerned the colloidal stability of MNPs coated with polymer, but their long-term stability when such complexes are exposed to physiological media is still not well understood. After zeta potential study, it is found that the dextran coating on MNPs improves the colloidal stability in water as well as in physiological media like PBS. The specific absorption rates (SAR) of these MNPs are found to be in 50-85 W/g in different concentrations of glucose and NaCl; and there values are suitable for hyperthermia treatment of cancer cells under AC magnetic field. After incorporation of MNPs up to 0.2-1mg/mL in 2 × 10(5)cells/mL (L929), the apoptosis and necrosis studies are carried out by acridine orange and ethidium bromide (AO and EB) staining and followed by visualization of microstructures under a fluorescence microscope. It is found that there are no morphological changes (i.e. no signs of cell rounding, bubble formation on the membrane and nuclear fragmentation) suggesting biocompatibility of dextran coated LSMO nanoparticles up to these concentrations.

Synthesis of oleic acid functionalized Fe3O4 magnetic nanoparticles and studying their interaction with tumor cells for potential hyperthermia applications.

In the present study, oleic acid (OA) functionalized Fe3O4 magnetic nanoparticles (MN) were synthesized following modified wet method of MN synthesis. The optimum amount of OA required for capping of MN and the amount of bound and unbound/free OA was determined by thermogravimetric analysis (TGA). Further, we have studied the effect of water molecules, associated with MN, on the variation in their induction heating ability under alternating current (AC) magnetic field conditions. We have employed a new approach to achieve dispersion of OA functionalized MN (MN-OA) in aqueous medium using sodium carbonate, which improves their biological applicability. Interactions amongst MN, OA and sodium carbonate were studied by Fourier transform infrared spectroscopy (FT-IR). Intracellular localization of MN-OA was studied in mouse fibrosarcoma cells (WEHI-164) by prussian blue staining and confocal laser scanning microscopy (CLSM) using nile blue A as a fluorescent probe. Results showed MN-OA to be interacting mainly with the cell membrane. Their hyperthermic killing ability was evaluated in WEHI-164 cells by trypan blue method. Cells treated with MN-OA in combination with induction heating showed decreased viability as compared to respective induction heating controls. These results were supported by altered cellular morphology after treatment of MN-OA in combination with induction heating. Further, the magnitude of apoptosis was found to be ~5 folds higher in cells treated with MN-OA in combination with induction heating as compared to untreated control. These results suggest the efficacy of MN-OA in killing of tumor cells by cellular hyperthermia.

Bi-functional properties of Fe3O4@YPO4:Eu hybrid nanoparticles: hyperthermia application.

Magnetic nanoparticles based hyperthermia therapy is a possible low cost and effective technique for killing cancer tissues in the human body. Fe3O4 and Fe3O4@YPO4:5Eu hybrid magnetic nanoparticles are prepared by co-precipitation method and their average particle sizes are found to be ∼10 and 25 nm, respectively. The particles are spherical, non-agglomerated and highly dispersible in water. The crystallinity of as-prepared YPO4:5Eu sample is more than Fe3O4@YPO4:5Eu hybrid magnetic nanoparticles. The chemical bonds interaction between Fe3O4 and YPO4:5Eu is confirmed through FeO-P. The magnetization of hybrid nanocomposite shows magnetization Ms = 11.1 emu g(-1) with zero coercivity (measured at 2 × 10(-4) Oe) at room temperature indicating superparamagnetic behaviour. They attain hyperthermia temperature (~42 °C) under AC magnetic field showing characteristic induction heating of the prepared nanohybrid and they will be potential material for biological application. Samples produce the red emission peaks at 618 nm and 695 nm, which are in range of biological window. The quantum yield of YPO4:5Eu sample is found to be 12%. Eu(3+) present on surface and core could be distinguished from luminescence decay study. Very high specific absorption rate up to 100 W g(-1) could be achieved. The intracellular uptake of nanocomposites is found in mouse fibrosarcoma (Wehi 164) tumor cells by Prussian blue staining.

Functionalization of La(0.7)Sr(0.3)MnO3 nanoparticles with polymer: studies on enhanced hyperthermia and biocompatibility properties for biomedical applications.

Now-a-days surface functionalized La(0.7)Sr(0.3)MnO(3) (LSMO) nanoparticles by different biocompatible polymers are attracted considerable interest in various biomedical applications in general and magnetic fluid hyperthermia treatment of cancer in particular. In this paper La(0.7)Sr(0.3)MnO(3) nanoparticles are synthesized and functionalized with polymer (dextran, with mean particle size ~25 nm). Magnetic measurements of both coated and uncoated particles reveal the superparamagnetic nature at room temperature. The resulting coated particles form a stable suspension in an aqueous environment at physiological pH and possess a narrow hydrodynamic size distribution. In vitro cytotoxicity of the MNPs has been assessed under Trypan blue dye exclusion and MTT assay on HeLa and L929 cell lines. The results demonstrate that dextran functionalized nanoparticles have no significant effect on cell viability within the tested concentrations (0.2-1 mg/mL) as compared to bare LSMO. Magnetic fluid hyperthermia studies have been done in detail; the influence of an applied alternating current (AC) magnetic field on heat generation is presented in brief. Dextran functionalized LSMO has the higher Specific absorption rate (SAR) value than the bare LSMO. After functionalization with dextran the SAR values of LSMO nanoparticles increased from 25 to 51 W/g. The study shows that the rise in temperatures by these nanoparticles could be safely controlled around Curie temperature (T(c)).

Counter ion induced irreversible denaturation of hen egg white lysozyme upon electrostatic interaction with iron oxide nanoparticles: a predicted model.

The effects of electrostatic interaction between the hen egg white lysozyme (HEWL) and the functionalized iron oxide nanoparticles (IONPs) have been investigated using several techniques, e.g., CD, DSC, ζ-potential, UV-visible spectroscopy, DLS, TEM. Nanoparticles (IONPs) were functionalized with three hydrophilic ligands, viz., poly(ethylene glycol) (PEG), trisodium citrate (TSC) and sodium triphosphate (STP); where both TSC and STP contain Na(+) counter ions. It has been observed that the secondary structure of HEWL was not affected by PEG functionalized IONPs, but was partially and almost completely perturbed by TSC and STP functionalized IONPs, respectively. The perturbation of the secondary structure was irreversible. We have predicted an interaction model to explain the origin of perturbation of HEWL structure. We have also investigated the stability of nanoparticles dispersions after interaction with HEWL and used the DLVO theory to explain results.

Induction heating studies of dextran coated MgFe2O4 nanoparticles for magnetic hyperthermia.

MgFe(2)O(4) nanoparticles with sizes around 20 nm have been prepared by a combustion method and functionalized with dextran for their possible applications in magnetic particle hyperthermia. The induction heating study of these nanoparticles at different magnetic field amplitudes, from 6.7 kA m(-1) to 26.7 kA m(-1), showed self-heating temperature rise up to 50.25 °C and 73.32 °C (at 5 mg mL(-1) and 10 mg mL(-1) concentrations in water respectively) which was primarily thought to be due to hysteresis losses activated by an AC magnetic field. The dextran coated nanoparticles showed a maximum specific absorption rate (SAR) of about 85.57 W g(-1) at 26.7 kA m(-1) (265 kHz). Dextran coated nanoparticles at concentrations below 1.8 mg mL(-1) exhibit good viability above 86% on mice fibroblast L929 cells. The results suggest that combustion synthesized MgFe(2)O(4) nanoparticles coated with dextran can be used as potential heating agents in magnetic particle hyperthermia. Uncoated and dextran coated samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric-differential thermal analysis (TG-DTA) and zeta potential-DLS studies.

Improvement of blue, white and NIR emissions in YPO4:Dy3+ nanoparticles on co-doping of Li+ ions.

As-prepared samples of YPO(4):2Dy nanoparticles prepared by polyol route show strong blue luminescence because of strong host contribution, whereas 500 and 900 °C annealed samples show cold and warm white luminescence, respectively because of different energy transfer rates from host to Dy(3+). Li(+) co-doping improves luminescence intensity as well as crystallinity significantly. Interestingly, Li(+) ions occupy interstitial sites of lattice. These materials will be potential candidates for white light emitting diodes and near-infrared emitting phosphors.

Luminescence properties of Tb3+-doped CaMoO4 nanoparticles: annealing effect, polar medium dispersible, polymer film and core-shell formation.

Tb(3+)-doped CaMoO(4) (Tb(3+) = 1, 3, 5, 7, 10, 15 and 20 atom%) core and core-shell nanoparticles have been prepared by urea hydrolysis in ethylene glycol (EG) as capping agent as well as reaction medium at low temperature ~150 °C. As-prepared samples were annealed at 500 and 900 °C for 4 h to eliminate unwanted hydrocarbons and/or H(2)O present in the sample and to improve crystallinity. The synthesised nanophosphors show tetragonal phase structure. The crystallite size of as-prepared sample is found to be ~18 nm. The luminescence intensity of the (5)D(4) → (7)F(5) transition at 547 nm of Tb(3+) is much higher than that of the (5)D(4) → (7)F(6) transition at 492 nm. 900 °C annealed samples show the highest luminescence intensity. The intensity ratio R (I[(5)D(4) → (7)F(6)]/I[(5)D(4) → (7)F(5)]) lies between 0.3-0.6 for as-prepared, 500 and 900 °C annealed samples. The luminescence decay of (5)D(4) level under 355 nm excitation shows biexponential behaviour indicating availability of Tb(3+) ions on surface and core regions of particle; whereas, contribution of Mo-O charge transfer to lifetime is obtained under 250 nm excitation. The CIE coordinates of as-prepared, 500 and 900 °C annealed 5 atom% Tb(3+)-doped CaMoO(4) samples under 250 nm excitation are (0.28, 0.32), (0.22, 0.28) and (0.25, 0.52), respectively. The dispersed particles in polar medium and its polymer film show green light emission. The luminescence intensity is improved significantly after core-shell formation due to extent of decrease of non-radiative rates arising from surface dangling bonds and capping agent. Quantum yields of as-prepared samples of 1, 5 and 7 atom% Tb(3+)-doped CaMoO(4) samples are found to be 10, 3 and 2, respectively.

Re-dispersion and film formation of GdVO4 : Ln3+ (Ln3+ = Dy3+, Eu3+, Sm3+, Tm3+) nanoparticles: particle size and luminescence studies.

GdVO(4) : Ln(3+) (Ln(3+) = Dy(3+), Eu(3+), Sm(3+), Tm(3+)) nanoparticles are prepared by a simple chemical route at 140 °C. The crystallite size can be tuned by varying the pH of the reaction medium. Interestingly, the crystallite size is found to increase significantly when pH increases from 6 to 12. This is related to slower nucleation of the GdVO(4) formation with increase of VO(4)(3-) present in solution. The luminescence study shows an efficient energy transfer from vanadate absorption of GdVO(4) to Ln(3+) and thereby enhanced emissions are obtained. A possible reaction mechanism at different pH values is suggested in this study. As-prepared samples are well dispersed in ethanol, methanol and water, and can be incorporated into polymer films. Luminescence and its decay lifetime studies confirm the decrease in non-radiative transition probability with the increase of heat treatment temperature. Re-dispersed particles will be useful in potential applications of life science and the film will be useful in display devices.

Polyvinyl alcohol: an efficient fuel for synthesis of superparamagnetic LSMO nanoparticles for biomedical application.

La(0.7)Sr(0.3)MnO(3) (LSMO) nanoparticles have been prepared using glycine and polyvinyl alcohol (PVA) as fuels. Their crystal structure, particle morphology and compositions are characterized using X-ray diffraction, transmission electron microscopy, field-emission electron microscopy and energy dispersive analysis of X-ray. They show a pseudo-cubic perovskite structure. The spherical particle sizes of 30 and 20 nm have been obtained from samples prepared by glycine and PVA respectively. The field cooled (FC) and zero field cooled (ZFC) magnetizations have been recorded from 5 to 375 K at 500 Oe and superparamagnetic blocking temperatures (T(B)) of 75 and 30 K are obtained from samples prepared by glycine and PVA respectively. Particle size distribution is observed from dynamic light scattering measurements. Dispersion stability of the particles in water is studied by measuring the Zeta potential with varying the pH of the medium from 1 to 12. Under induction heating experiments, a hyperthermia temperature (42-43 °C) is achieved by both the samples (3-6 mg mL(-1)) at magnetic fields of 167-335 Oe and at a frequency of 267 kHz. The bio-compatibility of the LSMO nanoparticles is studied on the L929 and HeLa cell lines by MTT assay for up to 48 h. The present work reveals the importance of synthesis technique and fuel choice on structural, morphological, magnetic, hyperthermia and biocompatible properties of LSMO and predicts the suitability for biomedical applications.

Stabilization of intrinsic defects at high temperatures in ZnO nanoparticles by Ag modification.

The stabilization of defects in ZnO at high temperatures has been investigated. The properties of unmodified and modified ZnO nanoparticles (NPs) with 2 at.% of Ag prepared by microwave assisted combustion method, have been systematically studied using X-ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and photocatalytic activity measurements. Though the XRD data shows a marginal shift in the ZnO peak position upon Ag addition, the amount of shift does not change with annealing temperatures. The PL data reveals that the defect mediated visible emission intensity of unmodified ZnO NPs increases with increase in the annealing temperature, whereas it remains almost unchanged in Ag-ZnO. This study clearly establishes that silver is an efficient stabilizer of intrinsic defects in ZnO at high temperatures. This is further supported by the core and valence band XPS spectra.