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Diluted magnetic semiconductor based on Ni-doped TiO 2 has been synthesized by hydrothermal process and effect of Ni doping on structure, morphology and magnetic studies were investigated. X-ray Rietveld analysis confirmed that all the samples were TiO 2 anatase structure without having any impurity phase. The lattice parameter and cell volume increased in Ni-doped TiO 2 nanotubes. TEM micrograph reveals clearly the formation of TiO 2 nanotubes with diameter of ∼8 nm. Magnetic properties studies were carried out by using vibrating sample magnetometer at room temperature and ferromagnetism was observed in both pure and Ni-doped TiO 2 nanotubes. The bound magnetic polarons formed by Ni ions and the oxygen vacancy may be responsible for the increased magnetic moment in Ni-doped TiO 2 nanotubes. These findings provide a better understanding for the mechanisms of Ni doped TiO 2 nanotubes ferromagnetism at room temperature.

We investigated the static and dynamic aspects of the magnetic properties for single phase nanocrystalline BiFeO 3 with average crystallite size of 35 nm. The frequency dependence of the peak is observed in the real part of ac susceptibility χ′ ac vs T measurement and described well by the Vogel-Fulcher law as well as the power law. These analyses indicated the existence of cluster glass state with significant interaction among the spin clusters and results in cluster-glass like cooperative freezing at low temperature. The influence of temperature and magnetic field cooling on the exchange bias effect is investigated. A training effect is also observed. We have reported a significantly high ZFC & FC exchange bias of 200 Oe & 450 Oe at 300 K and 900 Oe & 2100 Oe at 5 K. The obtained results are interpreted in the framework of core-shell model, where the core of the BFO nanoparticles shows antiferromagnetic behavior and surrounded by CG-like ferromagnetic (FM) shell associated to uncompensated surface spins.

We report synthesis, characterization and magnetic properties of exchange-coupled L 1 0 -FePt/fcc-FePt nanomagnets. Structural and morphological characterization of exchange-coupled L 1 0 -FePt/fcc-FePt was carried out by powder X-ray diffraction, Mossbauer spectroscopy and transmission electron microscopy. Rietveld refinement of powder X-ray diffraction pattern has been used to quantify L 1 0 -FePt and fcc-FePt phases present in samples. Room temperature Mossbauer spectroscopy showed sextets of both L 1 0 -FePt and fcc-FePt phases with their respective hyperfine interaction parameters. Transmission electron microscopic (TEM and HRTEM) images confirmed nanocrystalline nature of exchange-coupled nanomagnets with particle size ranges from 15 nm to 50 nm after annealing for different time at 700 °C. Room temperature magnetic studies showed ferromagnetic nature of nanomagnets and maximum energy product (BH) max ~10.92 MGOe was obtained for sample containing 89.0% volume fraction of L 1 0 -FePt phase.

Textured Vanadium Nitride (VN) nanofibers are prepared from hydrothermally derived V 2 O 5 nanofibers by NH 3 reduction and nitridation approach. The reaction temperature is seen to be a crucial parameter to prepare pure VN phase. VN produced via this route has distinctive structural characteristics. The crystal structure, morphology, and oxidation states of the elements of VN nanofibers are characterized by XRD, FESEM, TEM, HRTEM, and XPS studies. Field emission properties for these textured VN nanofibers have been explored. The field emission properties show the reproducible turn-on field of 3.4 V/μm for the emission current density of 10 μA/cm 2 . The observed turn-on field is found to be quite superior compare to carbide, nitride and oxide nanostructures. High emission current density of 44 μA/cm 2 has been found at a field of 4 V/μm. Emission current stability for the preset current of 5 μA has been recorded for the period of 2 h. Present results indicate the considerable potential for the utilizing VN nanofibers as a cold cathode in the field emitter devices.

Electrochemical polarization behavior of two newly developed ferritic-pearlitic railway axle steels (MS3 and MS6) and the standard Indian conventional axle steel has been studied in sodium borate buffer solution of pH 8.4 with and without the presence of NaCl. The polarization behavior of both the new axle steels shows close resemblance, whereas, different polarization behavior has been observed for the conventional axle steel. Electrochemical impedance spectroscopy measurements have clearly reflected significantly improved passivation behavior for the newly developed steels compared to that of the conventional axle steel. NaCl salt fog exposure tests have also shown superior corrosion resistance of the newly developed axle steels as compared to the conventional axle steel. Higher surface roughness on the corroded conventional axle steel has also been observed compared to the smoother surface in case of the new axle steels. Higher corrosion resistance of the new axle steels has been attributed to their finer microstructure and strongly adherent protective rusts.

Monodisperse indium oxide (In 2 O 3 ) nanoparticles (NPs) with the average diameter of 11 nm were prepared by a solvothermal method. The In 2 O 3 NPs were characterized by X-ray diffraction, Raman and transmission electron microscopy. The intrinsic nature of ferromagnetism in In 2 O 3 NPs has been established with the experimental observation of magnetic hysteresis loop. Photoluminescence and UV–visible studies were employed to evidence the presence of oxygen vacancies and revealed that the oxygen vacancies contribute to the ferromagnetism. The origin of ferromagnetism in In 2 O 3 NPs may be due to exchange interactions among localized electron spin moments resulting from oxygen vacancies.

Carbon nanotubes (CNT) are nature’s finest gift to mankind, the most amazing and wonderful nanostructure that the human being has discovered so far. CNT are either single walled or multiwalled and have been studied extensively. A large number of research articles, review articles and books have been published on this topic. However, review articles covering all the aspects of CNT are rarely found. This article gives an overview of CNT in terms of classification, synthesis, characterization, functionalization, properties, composites, applications and future directions.

We report the room-temperature ferromagnetism in Cr-doped TiO 2 nanorods (NRs) synthesized via the hydrothermal method followed by annealing at 700 °C. The transmission electron microscopy showed that the diameter of the NRs is between 40 and 70 nm. X-ray diffraction, XPS and Raman technique are used to confirm the absence of magnetic contaminations of metallic Cr clusters or any other phases. To test the oxygen vacancy related ferromagnetism, annealing in oxygen, air and argon are performed. With the changing of annealing atmosphere from oxygen to argon, the saturation magnetization ( M s ) of NRs increases. These results strongly prove that the oxygen vacancies play an important role in inducing the ferromagnetism. The shifting and broadening of the most intense E g (1) mode at 144 cm −1 observed by Raman spectroscopy further confirms that the origin of the ferromagnetism in NRs is due to the oxygen vacancies.

We investigated static and dynamic magnetic properties of surfactant capped 25 nm Co 50 Ni 50 particles. These nanoparticles exhibit the superparamagnetic behavior at 300 K. Interestingly, a freezing temperature ( T f ∼ 16 K) is observed in the ZFC curve, which corresponds to surface spin-glass-like transition. The significant high coericivity ( H c ∼ 910 Oe) is observed at 5 K as compared to H c ∼ 180 Oe at 77 K and is attributed to the random freezing of surface spins at T ⩽ T f . The spin-glass-like behavior of nanoparticles is further verified by ac-susceptibility measurements as a function of temperature at different frequencies. The fits of Arrhenius law, Vogel–Fulcher law and dynamic scaling equation to data confirm the spin-glass-like behavior of Co 50 Ni 50 nanoparticles.

A series of Ti1−xFexO2−δ (0 ≤ x ≤ 0.03) nanoparticles (NPs) were synthesized by sol–gel route. The NPs had a size distribution in the range of 15–40 nm and were identified as the anatase TiO2 by X-ray diffraction (XRD) and Raman analysis. XRD, selected area electron diffraction, Raman and Mossbauer analysis ruled out the signature of Fe-cluster or any other oxides of Fe. The redshifting of the band edge emission peak observed in UV–vis absorption studies further confirmed the doping of Fe ions in the TiO2 lattice. Raman studies show the shifting and broadening in Eg(1) and Eg(3) modes with Fe doping. It suggested that the activation of ferromagnetism with increasing Fe doping concentration was related to the oxygen vacancy defects. The presence of such defects was further confirmed from electron paramagnetic resonance (EPR) measurements. The observed ferromagnetism is interpreted in terms of bound magnetic polaron (BMP) model.

Phase pure nanosized BiFeO3 (BFO) powder was synthesized by sol–gel method based on the propylene glycol-gel reaction. The formation mechanism, crystal structure, magnetic and optical properties were investigated by thermogravimetry, differential thermal analysis, infrared spectroscopy, X–ray diffractometry, Rietveld analysis, Raman spectroscopy, transmission electron microscopy, SQUID magnetometry and ultraviolet–visible spectroscopy. X–ray diffraction and Raman studies revealed the formation of pure and well-crystallized BFO nanocrystallites at a low temperature of 400°C. The BFO nanoparticles showed weak ferromagnetic property at room temperature due to size-confinement effects. The UV–visible spectra showed strong band-gap absorption at ~590 nm (2.1 eV) for BFO nanoparticles suggesting their potential application as visible-light-response photocatalyst.

We report the variation of Curie temperature ( T c ) and coercivity ( H c ) of the single domain Co N interstitial materials synthesized via nitridation of the hexa-ammine Cobalt(III) nitrate complex at 673 K. Co N materials crystallize in the fcc cubic structure with unit cell parameter, a = 3.552 A. The X-ray diffraction (XRD) peaks are broader indicating the materials to be nano-structured with crystallite sizes of 5–14 nm. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies confirm the nanocrystalline nature of the materials. TEM images show chain-like clusters indicating dipolar interactions between the particles. Magnetic studies focus on the existence of giant magnetic Co atoms in the Co N lattice that are not influenced by the thermal relaxation. The values of the H c could be tuned with the dimension of the particles. The values of T c of the nitride materials are masked by the onset of the ferromagnetic to superparamagnetic transition at higher temperatures. Thermomagnetic studies show an increasing trend in the Curie temperature, T c , with decrease in particle dimension. This result has been explained qualitatively on the basis of ferromagnetic to superparamagnetic transition and finite size scaling effects.

The Cu-doped hydrogen titanate nanorods are synthesized via a hydrothermal reaction and converted into Cu-doped TiO2(B) and anatase phases by calcinations. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and selected area electron diffraction (SAED) pattern do not show the presence of any other phases and thus confirmed the intrinsic ferromagnetic behavior rather than it arising from metallic clusters. The blue shifting in absorption edge and increase in photoluminescence (PL) intensity from Cu-doped hydrogen titanate to anatase phase are strongly correlated with concentration of oxygen vacancies and defect formation. The higher concentration of oxygen vacancies and/or structural defects leads to the coalescence of ferromagnetic domains, which corroborates to the observed higher magnetization value of Cu-doped anatase phase compared to other phases.

High-quality self-assembled V(2)O(5) nanofiber-bundles (NBs) are synthesized by a simple and direct hydrothermal method using a vanadium(v) hydroxylamido complex as a vanadium source in the presence of HNO(3). The possible reaction pathway for the formation of V(2)O(5) NBs is discussed and demonstrated that HNO(3) functions both as an oxidizing and as an acidification agent. V(2)O(5) NBs are single-crystals of an orthorhombic phase that have grown along the [010] direction. A bundle is made of indefinite numbers of homogeneous V(2)O(5) nanofibers where nanofibers have lengths up to several micrometres and widths ranging between 20 and 50 nm. As-prepared V(2)O(5) NBs display a high electrochemical performance in a non-aqueous electrolyte as a cathode material for lithium ion batteries. Field emission properties are also investigated which shows that a low turn-on field of ∼1.84 V μm(-1) is required to draw the emission current density of 10 μA cm(-2).

A simple methodology has been demonstrated to synthesize various nanocrystalline Cu2O materials assisted by composite surfactant system, SDS and Tween 80 using the polyol method. Glycolaldehyde prepared in situ by heating ethylene glycol solvent at 160 °C for 2 h, was utilized as the reducing agent. The relative ratio of the two surfactants was manipulated to achieve different Cu2O morphologies, e.g. nanocrystalline Cu2O flowers, hollow spheres consisting of holes and ring type structure. The FT-IR spectroscopy confirmed that the SDS and Tween 80 moieties were indeed present on the surface as capping agents in order to stabilize the surface nanocrystallites by the co-ordinative interactions between the oxygen atoms of Tween 80 and SDS and the Cu atoms at the surface of the synthesized Cu2O particles. These oxygen atoms eventually encourage the oxidation of the surface Cu atoms to form a thin CuO layer, presence of which on the surface was corroborated by the XPS measurements. Sputtering of the samples was also carried out to remove the surface CuO thin layer and expose the inner Cu2O. These nanomaterials were then investigated for their potential applications in photocatalytic degradation of Rhodamine B dye.

Nanotubes of TiO2(B) phase doped with 5 at.% of vanadium (V) have been synthesized by a hydrothermal method, followed by calcination at 300 °C in air and argon atmosphere, respectively. These nanotubes exhibit ferromagnetic character with clear hysteresis loop at room-temperature. X-ray diffraction and Fourier transform infrared spectroscopy confirm that the ferromagnetic behavior is intrinsic to the material and not due to other phases and/or metallic clusters. The photoluminescence and hysteresis loop characteristics are found to be dependent on calcination conditions, and implicate the role of oxygen vacancies. Existence of higher oxygen vacancies in V-doped TiO2(B) nanotubes synthesized in argon than the air atmosphere is supported by the room-temperature photoluminescence spectra. The enhanced ferromagnetic behavior observed in V-doped TiO2(B) nanotubes synthesized in argon than the air atmosphere is explained in terms of bound magnetic polaron (BMP) model.

Cu2O octahedra were successfully synthesized via a novel wet-chemical method using d -glucose and hydrazine as reducing agent at room temperature without the presence of any other surfactant. Presence of d -glucose was important for the stabilization of the evolved copper octahedra and also for facilitating the reduction of the Cu(II) ions. The existence of glucose moieties on the surface as capping agent was confirmed by the FT-IR spectra while there was presence of excess oxygen atoms on the surface leading to the formation of a thin CuO layer at the octahedra surface, as confirmed by the XPS study, probably promoted by the capping glucose. Effect of NaOH concentration on the reaction and the formation of octahedra was also studied. The formation mechanism of obtained Cu2O octahedra has been discussed. These octahedra were then studied for their photocatalytic properties in degradation of organic dyes, rhodamine B and methyl orange.

In this study, we describe the development of a facile and effective route for the synthesis of Fe(3)O(4)-based T(1) contrast agent, which can be useful for in vivo magnetic resonance (MR) imaging. Citrate-coated Fe(3)O(4) nanoparticles (6 nm) with a narrow size distribution were synthesized by "one-pot green chemistry route" in diethylene glycol (DEG) solvent. The synthesized nanoparticles were characterized by different analytical techniques including XRD, TEM, HRTEM, and FTIR. At room temperature, nanoparticles exhibited superparamagnetic nature with high saturation magnetization. The longitudinal (r(1)) and transverse (r(2)) relaxivities were found to be 35.45 and 51.81 mM(-1)s(-1), respectively. Contrast agent developed by this method showed a relatively higher longitudinal relaxivity (r(1)) and the lowest relaxivity ratio (r(2)/r(1)=1.46) at 3T MR field. The anionic nature of citric acid facilitated non-specific internalization without impairment of cell viability and functionality. The in vitro studies showed both phagocitic and non-phagocytic uptake of these NPs. In vivo MR imaging of swine showed both T(1) and T(2) contrast effect.

The changes in the ferroelectric and magnetic properties of the nanostructured Pb(Zr0.52Ti0.48)1-xFexO3 (0 ≤ x ≤ 0.06) due to the doping of different amounts of acceptor ions (Fe3+) have been studied. X-ray diffraction studies show that the system maintains the tetragonal phase up to the doping of 2 mol% of Fe3+ and the formation of secondary phase magnetoplumbite (PbFe12O19) on further doping. Electron paramagnetic resonance studies have revealed the formation of defect centers which in turn arise due to the interaction of Fe3+ ions with oxygen vacancies, which are generated in the lattice. This results in the appearance of room temperature ferromagnetic (RTFM) behavior in the doped samples. The dielectric studies reveal that with the concentration of Fe3+ the peak near the maxima of dielectric constant (e′m) is broadened. Studies of the defect dipoles on the ferroelectric properties have been performed by polarization measurement. The variations of the above properties with the structural and morphological features of the samples have also discussed.

Mn-doped TiO2 nanorods which showed room temperature ferromagnetic (RTFM) behavior have been synthesized by a hydrothermal method. Analysis of X-ray diffraction and Raman spectral data reveal the formation of anatase phase without any impurity phase. From the hysteresis loop measurements, it is possible to estimate the two parameters, magnetization (MS) and coercivity (HC) which are 33 memu/g and 89 Oe respectively, for 5 at% Mn-doped TiO2. The two parameters (MS, HC) are strongly dependent on the Mn doping concentration. The origin of the RTFM is understood in terms of the concentration of oxygen vacancies and/or defects which is created by Mn doping.

High quality, single-crystalline alpha-MoO3 nanofibers are synthesized by rapid hydrothermal method using a polymeric nitrosyl-complex of molybdenum(II) as molybdenum source without employing catalysts, surfactants, or templates. The possible reaction pathway is decomposition and oxidation of the complex to the polymolybdate and then surface condensation on the energetically favorable 001] direction in the initially formed nuclei of solid alpha-MoO3 under hydrothermal conditions. Highly crystalline alpha-MoO3 nanofibers have grown along 001] with lengths up to several micrometres and widths ranging between 280 and 320 nm. The alpha-MoO3 nanofibers exhibit desirable electrochemical properties such as high capacity reversibility as a cathode material of a Li-ion battery.

Cuprous oxide (Cu2O) flower-like nanostructures doped with various metal ions i.e. Fe, Co, Ni and Mn have been synthesized by an organic phase solution method. The powder X-ray diffraction study clearly reveals them as single phase simple cubic cuprite lattice. Study of their magnetic properties have shown that these doped samples are ferromagnetic in nature; however, no such property was observed for the undoped Cu2O sample. The magnitude of the ferromagnetic behavior was found to be dependent on the dopant metal ions amount, which increased consistently with its increase. As total magnetic moment contribution of the doped metal ions calculated was insignificant, it is believed to have originated from the induced magnetic moments at cation deficiency sites in the material, created possibly due to the disturbance of the crystal lattice by the dopant ions. The existence of the defects has been supported by photoluminescence spectra of the doped samples.

Here we report the synthesis and characterization of Cu 2 O nanorods doped with Mn, Ni and Co transition metal ions and the study of their magnetic properties. Synthesis of the nanorods was carried out by the modified polyol method. Powder X-ray diffraction patterns clearly showed them to be polycrystalline single phase material. They exhibited ferromagnetic behavior at room temperature, however no such behavior was observed for the reference undoped sample, which indicated that unintentionally introduced magnetic impurities were not responsible for the observed phenomenon. Ferromagnetic behavior was found to be dependent on the dopant concentration and increased consistently with its increment in the material. The total magnetic moments contribution was calculated for the dopant concentration and was found to be insignificant to account for the observed ferromagnetism, therefore it was suggested that ferromagnetism could have conjured up from the induced magnetic moment in the defects created as cation vacancies in the material. The presence of the defects was supported by the room temperature photoluminescence study which showed that intensity of the peaks was dependent on the dopant concentration and increased consistently with it. There was strong correlation between the magnitude of the photoluminescence peak and the observed ferromagnetic property in the doped samples.

Cuprous oxide (Cu2O) nanorods doped with iron impurities have been synthesized by the polyol method using sodium dodecyl sulfate as the surfactant. The X-ray diffraction measurement reveals the pure phase of simple cubic Cu2O and the electron microscopy displays its one dimensional morphology. Ferromagnetism was observed at room temperature in the magnetic measurements of the doped samples while undoped sample exhibits only diamagnetism. Room temperature Mossbauer spectra for the samples exhibited only doublets but no sextet, which corresponds to the presence of paramagnetic iron sites. As magnetic moment contribution of the doped ions was insignificant for the observed magnetism, ferromagnetic property in the doped samples could have been originated from the defects as cation vacancies. Existence of the defects was supported by the room temperature photoluminescence spectra of the doped samples in reference to the undoped sample.

We demonstrate the synthesis of large-scale high-quality single-crystalline γ-Mo2N fibers using α-MoO3 fibers as precursors by temperature-programmed reactions with NH3. The formation mechanism is discussed, and the morphology, structure, composition, and chemical states of the prepared fibers were characterized by X-ray diffraction pattern, field emission scanning electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction pattern, and X-ray photoelectron spectroscopy studies. The normal field emission properties of the product were investigated, and the turn-on field of 0.6 V/μm is reported for the first time. The Fowler−Nordheim (F-N) plot obtained from the current density-applied field (J-E) characteristic is almost found to be linear, and the I-t plot shows that the emission current remains nearly constant over 2 h. The γ-Mo2N fibers exhibit an enhanced performance as compared to other nitrides. Therefore, our field emission results show that the γ-Mo2N f...

Fe 3+ doped and undoped β-dicalcium silicates (β-Ca 2 SiO 4 or β-C 2 S) were prepared by sol–gel method. The gels formed were heated in a microwave oven and subsequently in a muffle furnace. The particle sizes of doped and undoped samples were found to be about 150 nm and 600 nm respectively. The materials were characterized by scanning electron microscopic, powder X-ray diffraction, BET specific area measurements, infrared spectroscopic and Mossbauer spectroscopic techniques. IR spectroscopic studies showed the possibility of distorted tetrahedral symmetry in Fe 3+ doped β-C 2 S. Calorimetric studies have shown that iron doped β-C 2 S is highly reactive. From Mossbauer spectroscopic studies it is found that electronic environment of Fe 3+ in β-C 2 S is changed due to hydration. Degree of hydration calculated from non-equilibrium water content measurements have shown that Fe 3+ doped β-C 2 S hydrates at a much higher rate. Scanning electron microscopic studies have revealed that the hydration products in both the cases are almost identical. Formation and hydration of β-C 2 S in the presence of Fe 3+ have been understood.

The magnetic ordering in e-Fe3N nanoparticles can be controlled by simultaneous variation of the particle size and nitrogen stoichiometry, which can lead to the ferromagnetism at room temperature. In this study, ∼73 nm e-Fe3−yN1+y (0.1 ≤ y ≤ 0.2) particles with saturation magnetization of 129.0 emu/g at 5 K (close to bulk 133.0 emu/g) are compared to ∼20 nm e-Fe2.999N1.001 particles. X-ray photoelectron spectroscopy (XPS) studies indicate the formation of nanometric surface oxide/oxynitride layer on the ferromagnetic/superparamagnetic nitride core. The nanoparticles are highly interacting with strong dipolar and exchange interactions. AC-susceptibility measurements confirm the spin-glass-like ordering at lower temperatures.

The Mossbauer spectra of e-Fe 3 N at 5 K show several sextets which indicate a disordered arrangement of nitrogen atoms. Even though the 5 K spectra hints out a distribution for the Fe atoms coordinated with two nitrogen atoms (Fe(II)), the in-field spectrum showed that the Fe(II) atoms are magnetically different. It is found that the arrangements of magnetic spins with the direction of easy magnetic axis are different for the two Fe(II) sites. In addition to this, the presence of an antiferromagnetic phase is revealed in an in-field Mossbauer spectrum at 5 K.

ɛ -Fe 2.4 Co 0.6 N nanoparticles are prepared by nitridation of ultrafine iron–cobalt oxide in NH 3 gas atmosphere at 873 K for 3 h. Their magnetic properties are studied using ac and dc magnetization techniques. Two peaks at 69 and 151 K are found in ac susceptibility study. The former peak is assigned to superparamagnetic blocking temperature ( T B ∼ 69 K), whereas the origin of the latter one could not be ascertained since it is observed only from imaginary part of ac susceptibility study. The positions of peaks are found to be dependent on the applied fields and frequencies. Also, dc magnetization studies corroborate T B . Anisotropy constant ( K a ) is found to be 2.3 × 10 5 erg/cm 3 . The peaks disappear at high-applied field due to the overcome of applied filed over anisotropic energy. Ferromagnetic domains rotate incoherently. At low temperature, Bloch law cannot be applied, but Curie law can be applied above T B . Interestingly, spin relaxation is faster at 10 K as compared to that at 70 K indicating the presence of frustration of spins at lower temperature.

The system manganese substituted lanthanum ferrite viz. LaMn x Fe 1− x O 3 (1.0 ≤ x ≥ 0) was prepared by sol–gel autocombusion method. The structural characterization of the samples was carried out by X-ray diffraction technique and it is found that, the phase transfer from cubic to orthorhombic perovskite structure. The lattice parameter and crystallite size decrease with increasing Mn content. The phase formation of perovskite was revealed by thermal analysis technique. The surface morphology and elemental analysis of all the samples were carried out by scanning electron microscopy and energy dispersive X-ray spectroscopic technique, respectively. Electrical properties of the compounds show that, they exhibit semiconducting behavior. The substitution of manganese ions plays an important role in changing their structural, electrical and magnetic properties of lanthanum ferrite.

e-Fe y N (2

Well defined, dense, hollow spheres of anatase titania (TiO 2 ) nanoparticles were produced from TiCl 4 (as precursor) by diffusion flame technique. Flow rates of gases (LPG/air/N 2 compositions) were found to affect particle size. Titania nanoparticles were observed to decrease from 19 to 8 nm when the air flow rates were increased from 20 to 25 lpm. However, the particle size was found to increase from 15 to 21 nm when the nitrogen flow rate was increased from 0.8 to 2.0 lpm. LPG has been used as fuel. The increase in particle size of anatase TiO 2 was due to higher flame height and temperature. The anatase (TiO 2 ) phase was predominant compare to rutile phase in the ratio of 74:26 using air as an oxidant. In the gas phase reaction, the nanoparticles formation occurs due to spontaneous increase of number density of nuclei. The coagulation or aggregation of particles leads to the formation of larger particles due to higher chances of collisions among the particles and sintering at high flame temperature.

A new ternary nitride, CoMoN2, was prepared in the nanosize regime of 9.0 ± 2.0 nm, by nitridation of the precursor intermetallic nitride Co3Mo3N. XRD–Rietveld analysis revealed the presence of 0.60 (±0.02) mass % of Co impurity phase. The calculated space groups of CoMoN2 and Co are P6 3 /mmc and Fm-3m, respectively. The N atoms lie at the interstitial sites and the 12 calculated nitrogen sites indicate the presence of a layered structure. The XPS studies indicated the presence of the nitride and surface oxynitride/oxide phases. CoMoN2 is an interstitial nitride with Co and Mo in the zero oxidation state. The room temperature susceptibility is estimated after subtracting the ferromagnetic contribution from cobalt and found to be 2.7 × 10−4 emu g−1 Oe−1, indicating the Pauli-paramagnetic nature. The ferromagnetic exchange interactions between the Co atoms in CoMoN2 are reduced due to the presence of Mo and N in the crystal lattice. The hysteresis loop shift 19 Oe is attributed to the demagnetizing dipolar fields created in the soft CoMoN2 phase by the hard Co phase.

Mixed metal oxides possessing spinel structure exhibit interesting structural, electrical, magnetic and catalytic properties. During the course of investigation, chromium substituted magnesium ferrites were synthesized by co-precipitation technique using NaOH at a pH of 9.5. Formation of spinel phase was identified using X-ray diffraction technique (CuK α 1.54056 A). All the compounds exhibited cubic spinel symmetry and lattice constant varied between 8.40 and 8.33 A. They showed decreasing trend with increase in concentration of chromium. Infra-red spectral studies showed two strong bands one around 600 cm −1 which is attributed to the intrinsic vibrations of tetrahedral complexes and other at 400 cm −1 is due to octahedral one. The morphology and size of the particles was found by scanning electron microscope while element compositions by elemental dispersive X-ray spectroscopy. The various compounds of the system MgFe 2− x Cr x O 4 were also investigated for their thermal, electronic and magnetic hysteresis studies.

Self-assembled monodispersed ferromagnetic fcc cobalt nanoparticles with sizes varying from 6 to 24 nm were synthesized by reductive thermal decomposition of cobalt–oleyl amine complex in the presence of various surfactants such as oleic acid, polyvinyl pyrollidone and trioctylphosphine. The magnetic measurements at 5 and 300 K established the single to multi-domain behavior. The highest coercivity for the nanoparticles was found to be of the values 622 and 210 Oe at 5 and 300 K respectively. This is due to the coherent rotation of spins.

Zirconium oxide (zirconia) exists in three crystalline forms of monoclinic, tetragonal and cubic structures at atmospheric pressures. The cubic form of zirconia is well known for its mechanical, electrochemical and optical applications. Fe-doped cubic zirconia (high temperature phase) compositions are synthesized by microwave combustion method. Here, we present a Mossbauer investigation of Zr1 − x Fe x O2 composition within a range of Fe (0.03 < x < 0.09). 57Fe Mossbauer spectra were recorded at room temperature and at low temperature (77 K) for all samples. 3% Fe-doped ZrO2 shows doublet and the corresponding 6% and 9% Fe-doped ZrO2 samples show superimposed sextet and doublets. The isomer shift and quadrupole moment indicate, Iron to be in III oxidation state and to occupy different octahedral sites, associated with some amount of disorder. X-ray powder diffraction pattern of Fe-doped ZrO2 samples appear as very well crystalline. The Miller indices refer to the cubic fluorite-type ZrO2 structure. The magnetic behavior shows increase in moment and decrease in coercivity, with increase in Fe concentration. The M vs. H plots of the as-prepared Zr1-x Fe x O2 essentially show typical hysteresis loops, indicating room temperature ferromagnetism. Thus, the introduced microwave combustion route is an effective process to achieve multifunctional Fe-doped Zirconia with coexistent magnetic properties.

Nano scale magnetite based ferrofluid is synthesized by chemical co pre cipitation technique and stabilized with oleic acid. Magnetization and viscosity measurements were used to optimize for texturing purpose. The freeze-textured ferrofluid in two configurations, namely, (1) field texture system (FTS) and (2) zero field texture system (ZTS) are investigated by magnetization measurements at 298 K and Mossbauer spectroscopy measurements at 77 and 298 K. These results are analysed on the basis of the contributions from collective superparamagnetic reversal and the strength of the inter particle interactions.

In the present communication, we have reported the synthesis of nanocrystalline lead ferrite (PbFe2O4) by citrate mediated autocombustion method. X-ray diffraction pattern reveals the single phase formation in cubic (spinel) structure. The particle size and the surface morphology of the samples are characterized by TEM and SEM analysis. Magnetic studies are carried out using vibrating sample magnetometer (VSM) shows a very high coercive field for the material. Mossbauer studies were performed to investigate the local symmetry i.e. Fe is in octahedral/tetrahedral site and the charge states of Fe ions.

Nanocrystalline Fe3Mo3N, FeMoN2 and Ni3Mo3N interstitial nitrides having particle sizes of 32, 50 and 80 nm respectively, were synthesized by molybdate precursor route. The nanocrystalline nature was examined by XRD and SEM. Both, the field and temperature dependence of magnetic characteristics indicate paramagnetic behavior of the materials and the possible presence of magnetic contamination in the nitride materials. We examine the Mossbauer spectroscopic investigations in order to probe the magnetic characteristics and contaminations therein. X-ray photoelectron spectroscopy (XPS) study corroborates the possible presence of magnetic oxide phases at the surface of the Fe3Mo3N and Ni3Mo3N nano-particles. In summary, this paper investigates the magnetic properties of newer nitrides with appropriate corroboration with the Mossbauer and XPS studies.

Nanostructured single domain ɛ-Fe3N particles have been prepared by chemical route. Magnetic dipolar interaction among particles has been observed. The FC and ZFC magnetization curves show the superparamagnetic blocking temperature around 125 K, at low applied field of 0.005 T. At higher applied field, these ZFC and FC magnetization curves merge because of increase in magnetization energy that overcomes the magnetic anisotropy and dipolar interaction energies. Mossbauer spectroscopy further corroborates the superparamagnetic nature at 300 K.

ɛ-Fe3−xNixN (0.1 ≤ x ≤ 0.8) nanoparticles are investigated for the magnetic interaction effects at low temperatures. The reduction of saturation magnetization (σs) values is attributed to spin pairing effects and surface spin canting. In ZFC and FC magnetization curves, the surface spin-glass layer (Tf1) and the reentrant spin-glass behavior (Tf2) are evidenced below 27 and 22 K respectively. The surface spin-glass phase is described by the random-field model of exchange anisotropy. Based on this theory, a surface spin-glass layer about 8 nm thick is determined. The reentrant spin-glass behavior occurs due to the disorder created by Ni substitution and is observed for 0.2 ≤ x ≤ 0.4. The spin-glass-like ordering in the representative ɛ-Fe2.6Ni0.4N system is verified using spin relaxation dynamics and ac susceptibility measurements. The dynamic scaling analysis, based on imaginary part of the ac susceptibility data, gives the parameters τ0 = 10−8 s, Tc = 15.3 K, and zν = 4.5 and hence confirm the spin-glass-like ordering in ɛ-Fe3−xNixN (0.1 ≤ x ≤ 0.8) nanoparticles.

Hydrogel/PZT composite was prepared by encapsulating, Pb(Zr0.52Ti0.48)O3 (PZT) nanoparticles in an electroactive (PVA–PAA) hydrogel. The XRD studies confirmed the presence of pure tetragonal phase in PZT with crystallite size of 13 nm in the composite matrix. PZT nanoparticles were found to be embedded in the micro pores of PVA–PAA hydrogel as indicated by the SEM images. The composite shows three step degradation process in the TG/DTA measurements. Dielectric properties were studied from room temperature to 120 °C within wide frequency range of 100 Hz–600 kHz. At room temperature and intermediate frequency range, the composite shows a high dielectric constant of ~225 to 600 and low dielectric loss of 0.08.

Nanoparticles of ɛ-Fe2.8Cr0.2N system exhibit the exchange bias phenomenon due to the exchange coupling of the spins of the antiferromagnetic (AF) oxide/oxynitride surface layer and the ferromagnetic (FM) nitride core. Exchange bias is observed at 10 K both in the absence and presence of cooling field. Due to the interface disorder, a mixture of parallel and anti-parallel/perpendicular coupling of the AF and FM spins is observed. The roughness of AF-FM interface induces disorder due to the random exchange anisotropy. The saturation magnetization is also found to be drastically lowered as compared to parent ɛ-Fe3N. Below 58 K, the broad peak (TE ≅ Tf) in zero-field cooled (ZFC) magnetization curves indicates the presence of unidirectional anisotropy and spinglass-like ordering, that arises from the freezing of localized frustrated spins.

Re-dispersible CdS, 5 at.% Eu3+-doped CdS, 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS nanoparticles in organic solvent are prepared by urea hydrolysis in ethylene glycol medium at a low temperature of 170°C. CdS nanoparticles have spherical shape with a diameter of ∼80 nm. The asymmetric ratio (A 21) of the integrated intensities of the electrical dipole transition to the magnetic dipole transition for 5 at.% Eu3+-doped CdS is found to be 3.8 and this ratio is significantly decreased for 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS (A 21 = 2.6). It establishes that the symmetry environment of Eu3+ ion is more favored by Li-doping. Extra peak at 550 nm (green emission) could be seen for 2 and 5 at.% Eu3+ co-doped CdS. Also, the significant energy transfer from host CdS to Eu3+ is found for 5 at.% Eu3+-doped CdS compared to that for 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS.

ɛ-Fe3N/GaN, 54/46-composite nanowires (aspect ratio: 40), with core–shell structure, are synthesized by wet chemical method. Structural and morphological investigations are performed using X-ray diffraction (XRD)-Rietveld analysis and microscopy techniques. The encapsulation of ɛ-Fe3N by GaN is probed by X-ray photoelectron spectroscopy (XPS). The in-depth profile analysis probes the large interface region consisting both the phases. Although the respective surface oxynitride phases are present, the nitride phases are dominant inside the nanowires. The interface region of the nanowires influences the low temperature magnetic behavior. The superparamagnetic and ferromagnetic fractions coexist even at 5 K, due to the nanowire size distribution. Spin-glass-like collective ordering is observed below 50 K due to the freezing of the localized frustrated spins. Room temperature photoluminescence (PL) reveals the presence of surface states in the GaN shell.

The epsilon-Fe3N-CrN composite nanorods are synthesized by wet chemical technique. XRD-Rietveld analysis shows that epsilon-Fe3N and CrN crystallize in the space group P6(3)/mmc and Fm3m with relative mass compositions 53% and 47%, respectively. The nanorods have an average diameter approximately 30 nm and length approximately 400 nm X-ray photoelectron spectroscopy (XPS) studies show the presence of nitrides and oxynitrides (Fe-O-N/Cr-O-N) at the surface and the presence of elemental Cr in CrN matrix along with the nitrides inside the nanorods, probed by the in-depth profile analysis. The magnetic interactions between the spins of ferromagnetic (FM) epsilon-Fe3N and antiferromagnetic (AF) CrN throughout the volume of the nanorods give rise to exchange bias coupling. The exchange bias phenomenon is influenced by the rough and non-uniform AF-FM interface and spin-glass-like ordering at lower temperatures. The ac susceptibility studies confirm the spin-glass-like ordering.

The antimicrobial effects of copper ions and salts are well known, but the effects of cuprous oxide nanoparticles (Cu 2 O-NPs) on staphylococcal biofilms have not yet been clearly revealed. The present study evaluated Cu 2 O-NPs for their antibacterial and antibiofilm activities against heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) and vancomycin-intermediate S. aureus (VISA). Nanoscaled Cu 2 O, generated by solution phase technology, contained Cu 2 O octahedral nanoparticles. Field emission electron microscopy demonstrated particles with sizes ranging from 100 to 150 nm. Cu 2 O-NPs inhibited the growth of S. aureus and showed antibiofilm activity. The MICs and minimum biofilm inhibitory concentrations ranged from 625 μg/ml to 5,000 μg/ml and from 2,500 μg/ml to 10,000 μg/ml, respectively. Exposure of S. aureus to Cu 2 O-NPs caused leakage of the cellular constituents and increased uptake of ethidium bromide and propidium iodide. Exposure also caused a significant reduction in the overall vancomycin-BODIPY (dipyrromethene boron difluoride [4,4-difluoro-4-bora-3 a ,4 a -diaza- s -indacene] fluorescent dye) binding and a decrease in the viable cell count in the presence of 7.5% sodium chloride. Cu 2 O-NP toxicity assessment by hemolysis assay showed no cytotoxicity at 625 to 10,000 μg/ml concentrations. The results suggest that Cu 2 O-NPs exert their action by disruption of the bacterial cell membrane and can be used as effective antistaphylococcal and antibiofilm agents in diverse medical devices.

The simultaneous thermal decomposition and nitridation of [VO(NH 2 O) 2 Gly]·H 2 O complex in NH 3 atmosphere at 723–973 K gives the nanocrystalline vanadium nitride (VN) having crystallite size of 8–32 nm. It shows cubic NaCl structure with lattice parameter of a = 4.137 nm. XRD pattern Rietveld analysis program for crystal structure of VN shows the space group- Fm 3 m . The particle sizes measured by BET and SEM techniques are in the range of 26–100 nm. The particles are spherical and distributed homogeneously and found larger than XRD crystallite size because of agglomeration of crystallites. The fundamental IR absorption of VN material is found at 995 cm −1 which gives the force constant of 634.3 Nm −1 . The electrical resistivity and magnetic studies show the superconducting to normal transition ( T c ) at 9.2 K. Thermal decomposition of VN is carried out in O 2 atmosphere which goes through the formation of an oxynitride (V–N p –O q ) intermediate phase up to 913 K. Finally, nanocrystalline V 2 O 5 is formed at 973 K. The V 2 O 5 has orthorhombic structure with lattice parameters of a = 11.537, b = 3.568 and c = 4.380 A and the XRD crystallite size of 10 nm.