Magnetic phase transition from paramagnetic in Nb2AlC-MAX to superconductivity-like diamagnetic in Nb2C-MXene: an experimental and computational analysis.

Transition metal carbides (TMCs) have recently emerged as competent members among the family of two-dimensional (2D) materials, owing to their promising applications. There are many promising applications of MXenes; however, their magnetic properties lack a wide margin, both experimentally as well as theoretically, which needs to be investigated for potential use in spintronics. In this study, we carried out a comprehensive etching process via selective extraction of Al layers from Nb2AlC-MAX using a wet electrochemical route under well-optimized conditions to obtain fine 2D-Nb2C MXene sheets. Structural analysis using X-ray diffraction (XRD) confirms the effective removal of Al followed by confirmation of a 2D layered structure from morphological analysis using scanning electron microscopy (SEM). Zero-field-cooled (ZFC) and field-cooled (FC) measurements of MAX and MXene at different field strengths were performed using a superconducting quantum interference device (SQUID). Magnetic measurements reveal the paramagnetic nature of Nb2AlC-MAX measured under 5 mT; however, this changes to a clear superconductor-like diamagnetic behavior with a shift of the magnetization from positive to negative values at low temperatures when measured under 5 mT and 10 mT for Nb2C MXene. The diamagnetism, however, is changed to paramagnetism at 100 mT, which shows the existence of critical fields known typically for a type-II superconductor. To gain an insight into this unusual behavior in MXene, density functional theory (DFT) first-principles calculation was also performed in Wein2K software using spin-polarized generalized gradient approximation (sp-GGA). The magnetic moment of the compound is calculated to be negative, which corresponds well with the experimental finding and suggests that the negative magnetic moment originated from the d-orbital of Nb2C. The present report provides a pathway to deeply understanding the existence of superconductivity-like diamagnetic behavior in Nb2C MXene, which is useful for future magnetic applications.

Anomalous anisotropic behaviour of spin-triplet proximity effect in Au/SrRuO3/Sr2RuO4 junctions.

Spin-polarized supercurrents can be generated with magnetic inhomogeneity at a ferromagnet/spin-singlet-superconductor interface. In such systems, complex magnetic inhomogeneity makes it difficult to functionalise the spin-polarized supercurrents. However, spin-polarized supercurrents in ferromagnet/spin-triplet-superconductor junctions can be controlled by the angle between magnetization and spin of Copper pairs (d-vector), that can effectively be utilized in developing of a field of research known as superconducting spintronics. Recently, we found induction of spin-triplet correlation into a ferromagnet SrRuO3 epitaxially deposited on a spin-triplet superconductor Sr2RuO4, without any electronic spin-flip scattering. Here, we present systematic magnetic field dependence of the proximity effect in Au/SrRuO3/Sr2RuO4 junctions. It is found that induced triplet correlations exhibit strongly anisotropic field response. Such behaviour is attributed to the rotation of the d-vector of Sr2RuO4. This anisotropic behaviour is in contrast with the vortex dynamic. Our results will stimulate study of interaction between ferromagnetism and unconventional superconductivity.

Morphological, Magnetic and Optical Properties of α-Fe2O3 Nanoflowers.

We report the morphological, structural and magnetic properties of the flower like iron oxide α-Fe2O3 samples prepared by the polyol method. The α-Fe2O3 samples were prepared by using different amount of the iron chloride in the starting materials and the impact of the different iron chloride amount on the morphology of the precursor and after heat treatment of the samples was investigated. The X-ray diffraction (XRD) analysis confirmed the formation of the α-Fe2O3 phase without detecting any impurity phase. The transmission electron microscopy (TEM) and the field emission scanning electron microscopy (FESEM) results showed that the flower like structures are composed of nanopetals with an average thickness and width of 60 nm and 735 nm respectively. A strong impact on the formation of the flower like iron oxide and the morphologies of these samples was observed with the variation of iron chloride concentration during synthesis process. The magnetic hysteresis measurements demonstrated that as prepared samples displayed ferromagnetic behavior and magnetic properties were found to be depending on the morphologies of as-prepared samples. The band gap energy was measured by using Tauc's method, and values for all the samples were found to be in the range 1.94-2.27 eV. The results obtained in the present work show that the α-Fe2O3 can be used as potential candidate material for use in gas sensors, photocatalysis and energy storage devices.

Direct penetration of spin-triplet superconductivity into a ferromagnet in Au/SrRuO3/Sr2RuO4 junctions.

Efforts have been ongoing to establish superconducting spintronics utilizing ferromagnet/superconductor heterostructures. Previously reported devices are based on spin-singlet superconductors (SSCs), where the spin degree of freedom is lost. Spin-polarized supercurrent induction in ferromagnetic metals (FMs) is achieved even with SSCs, but only with the aid of interfacial complex magnetic structures, which severely affect information imprinted to the electron spin. Use of spin-triplet superconductors (TSCs) with spin-polarizable Cooper pairs potentially overcomes this difficulty and further leads to novel functionalities. Here, we report spin-triplet superconductivity induction into a FM SrRuO3 from a leading TSC candidate Sr2RuO4, by fabricating microscopic devices using an epitaxial SrRuO3/Sr2RuO4 hybrid. The differential conductance, exhibiting Andreev-reflection features with multiple energy scales up to around half tesla, indicates the penetration of superconductivity over a considerable distance of 15 nm across the SrRuO3 layer without help of interfacial complex magnetism. This demonstrates potential utility of FM/TSC devices for superspintronics.

Novel Biomimatic Synthesis of ZnO Nanorods Using Egg White (Albumen) and Their Antibacterial Studies.

Zinc oxide (ZnO) is well-recognized as a biocompatible multifunctional material with outstanding properties as well as low toxicity and biodegradability. In this work, a simple and versatile technique was developed to prepare highly crystalline ZnO nanorods by introducing egg white to a bio-inspired approach. X-ray diffraction (XRD) and selected area electron diffraction (SAED) pattern results indicated that the ZnO nanorods have single phase nature with the wurtzite structure. Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) results showed the nanometer dimension of the nanorods. Raman, FTIR, and TGA/DTA analyses revealed the formation of wurtzite ZnO. The antibacterial properties of ZnO nanorods were investigated using both Gram-positive and Gram-negative microorganisms. These studies demonstrate that ZnO nanorods have a wide range of antibacterial activities toward various microorganisms that are commonly found in environmental settings. Survival ratio of bacteria decreased with increasing powder concentration, i.e., increase in antibacterial activity. The antibacterial activity of the ZnO nanorods toward Pseudomonas aeruginosa was stronger than that of Escherichia coli and Staphylococcus aureus. Surprisingly, the antibacterial activity did not require specific UV activation using artificial lamps, rather activation was achieved under ambient lighting conditions. Overall, the experimental results suggest that ZnO nanorods could be developed as antibacterial agents against a wide range of microorganisms to control and prevent the spreading and persistence of bacterial infections. This research introduces a new concept to synthesize ZnO nanorods by using egg white as a biological template for various applications including food science, animal science, biochemistry, microbiology and medicine.

Effect of Zinc Nitrate Concentration on the Optical and Morphological Properties of ZnO Nanorods for Photovoltaic Applications.

We report the effect of zinc nitrate (ZN) concentration on the growth of zinc oxide (ZnO) nanorods and their optical and morphological properties. As prepared ZnO nanorods on glass substrate were characterized using field emission scanning electron microscopy (FE-SEM), ultra violet-visible (UV-Vis), Raman and Photo-luminescence (PL) spectroscopy. FE-SEM results show that the nanorods were obtained for the 0.033 and 0.053 M concentration of ZN. As the ZN concentration increased from 0.033 M to 0.053 M, the diameter of the nanorods was increased. It indicated that the diameter of the nanorods was affected by the ZN concentration. The Raman spectra of nanorods show only one peak at 438 cm(-1) corresponding to E2(high) high mode, which means that ZnO nanorods grown perpendicularly on the glass substrate, i.e., the ZnO nanorod arrays are highly c-axis oriented. Room-temperature PL spectrum of the as-grown ZnO nanorods reveals a near-band-edge (NBE) emission peak and defect induced green light emission. The green light emission band at -579 nm might be attributed to surface oxygen vacancies or defects. The UV-visible measurements reflect that the total transmittance for the as grown ZnO nanorods is over 80%. The simple technique presented in this study to grow ZnO nanorods on a glass substrate can be helpful for making the cost effective photovoltaic devices.

Magnetization and Magnetocaloric Effect in Sol-Gel Derived Nanocrystalline Copper-Zinc Ferrite.

We report the sol-gel synthesis and magnetocaloric effect in nanocrystalline copper-zinc ferrite (Cu0.5Zn0.5Fe2O4). The synthesized powder was characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and magnetization measurements. The XRD results confirm the formation of single phase spinel structure. The average particle size was found to be ~58 nm. FE-SEM results suggested that the nanoparticles are agglomerated and spherical in shape. Magnetization measurement reveals that Cu0.5Zn0.5Fe2O4 nanoparticles exhibit transition temperature (Tc) above room temperature. The maximum magnetic entropy change (ΔSM)max shows interesting behaviour and was found to vary with the applied magnetic field. This nanopowder can be considered as potential material for magnetic refrigeration above room temperature.

Relationship Between Structural, Morphological, Optical and Magnetic Properties of Transition Metal (TM)-Doped ZnO Nanostructures Prepared by Microwave-Hydrothermal.

In this work, pure and 3% TM (Co, Ni, and Cu)-doped ZnO nanostructures were prepared by microwave-hydrothermal method. The striking similarities between changes in the lattice volume, bandgap energy, morphology and saturation magnetization indicated a strong correlation between these properties. XRD, SAED and HRTEM analyses revealed that all the TM-doped ZnO nano-structures have wurtzite structure and no secondary phase was detected. FESEM and TEM results confirmed a higher aspect ratio and highly crystalline nature of nanostructures. Raman spectra revealed that no defect related mode was observed which indicated that the nanostructures have high quality and negligible defects. The value of bandgap was found to decrease with the increase in atomic number of TM dopants. RTFM was observed in all the TM-doped ZnO nanostructures and the value of Ms and Mr were decreased with TM dopants.

Synthesis and Characterization of Nanocrystalline Doped-ZnO Powder for Advanced Varistor Application.

The nanocrystalline doped ZnO powder has been synthesized by solution combustion method using sucrose as fuel and zinc acetate as oxidant. The as-prepared nanopowders were characterized by XRD, showing particle size approximately 39 and 48 nm for fuel to oxidant ratio of 1:1 (stoichiometric) and 2:1 (fuel rich). The powders were compacted and sintered for 9 hours. The sintered samples were characterized by SEM and XRD, showing the presence of spinel (Zn7Sb2Ol2) and pyroclore (Zn2Bi3Sb3Ol4) phases at intergranular spacing. The phase distribution [spinel (Zn7Sb2Ol2), pyroclore (Zn2Bi3Sb3O14), ß-Bi2O3, and δ-Bi203] was found to be more homogeneous in case of samples obtained by adding the stoichiometric amount of fuel. The current-voltage (J-E) characterization shows the high non-linearity coefficient (α) ~22 and break-down voltage (VB) of ~0.41 kV/mm for the fuel rich sample.

Study of Magnetic and Magnetocaloric Behaviour of (1 - Y)La0.7Ca0.3MnO3/(Y)MnFe2O4, (1 - Y)La0.7Ca0.3MnO3/(Y)Ni0.9Zn0.1Fe2O4 Composites.

We report the structural, magnetic and magnetocaloric properties of (1 - Y)La0.7Ca0.3MnO3/ (Y)MnFe2O4 (LCMO/MFO) and (1 - Y)La0.7Ca0.3MnO3/(Y)Ni0.9Zn0.1Fe2O4 (LCMO/NZFO) composites. Polycrystalline LCMO/MFO samples were prepared using the conventional solid-state reaction technique. The results of X-ray diffraction indicates mainly LCMO phase without characteristic lines of the MFO and NZFO phase. The magnetic study has revealed that the Curie temperature was influenced by the concentration of MFO and NZFO phases. A large magnetic entropy change has been observed for La0.7Ca0.3MnO3 compound. The value of the maximum magnetic entropy change was found to decrease in the composites samples with increasing the concentration of the MFO and NZFO phases. This investigation suggests that LCMO/MFO and LCMO/NZFO types of composites can give a new kind of refrigeration candidates, which can easily provide the tunable magnetocaloric effect.

High sensitivity troponin T in acute medicine; more questions than answers?

BACKGROUND: Troponin testing in acute medicine is routine. The introduction of a high sensitivity assay (hs Tn T) has created uncertainty regarding the clinical significance of 'abnormal' troponin T levels. The previous assay could not detect troponin levels <30 ng/l. AIMS AND METHODS: To characterize those with a hs Tn T ≥14 ng/l. Prospective cohort study of consecutive admissions to an acute medical unit. RESULTS: Troponin was measured in 564 consecutive patients (∼50% of all admissions) over 1 month; was ≥14 ng/l in 224 (40%) of which 220 patients had demographic data for this analysis. Median (inter-quartile range) peak troponin was 47.5 ng/l (24-130) and 36% had a Tn T between 14 and 30 ng/l. Mean [standard deviation (SD)] age was 72 (12) years and 57% were male. Only 44 patients (20%) had an acute myocardial infarction, reflecting the increased sensitivity but reduced specificity of the assay. Prognosis was poor with 31% mortality at 1 year. Over a mean (SD) follow-up of 648 (61) days, there were 87 deaths (40%). Those with a primary non-cardiac diagnosis (n = 126) had poorer survival than those with a primary cardiac diagnosis (n = 94). Troponin elevation related to sepsis conferred a very poor prognosis with 24 deaths (70%) over the follow-up period. CONCLUSION: Elevated hs Tn T is very common in acute medicine, but myocardial infarction as an explanation is uncommon. Overall, the prognosis is poor with a tendency to worse outcomes in those with a primary 'non-cardiac' diagnosis.

Doping dependent properties of Cr-doped ZnO nanostructures prepared by microwave irradiation.

In this work, undoped and Cr-doped single-crystalline ZnO nanorods were prepared by a facile microwave assisted solution method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that Cr-doped ZnO was comprised of single phase nature with hexagonal wurtzite structure up to 5% Cr doping, however, secondary phase ZnCr2O4 appeared upon further increasing the Cr dopant concentration. Field emission scanning electron microscopy (FESEM) and TEM micrographs suggested that the undoped nanorods with an average length of -~2 µm and a diameter in the range of 150-200 nm, respectively were observed. Interestingly, the size of nanorods decreased with the increase of Cr concentration in ZnO. Optical studies depicted that the energy bandgap was decreased with the increase of Cr concentration. Raman scattering spectra of Cr-doped ZnO revealed the lower frequency shift of E2(high) phonon mode with the increase in concentration of Cr dopant, suggested the successful doping of Cr into Zn site in ZnO. Magnetic studies showed that Cr-doped ZnO exhibited room temperature ferromagnetism (RTFM) and the value of magnetization was continuously decreased with the increase in Cr doping.

Dimensionality dependent magnetic and magnetocaloric response of La0.6Ca0.4MnO3 manganite.

We report the sol-gel synthesis and impact of reduced dimensionality on the magnetocaloric properties of La0.6Ca0.4MnO3 manganite. The synthesized powders were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and magnetization measurements. The XRD results indicated that the La0.6Ca0.4MnO3 nanoparticles have single phase nature with orthorhombic structure. FE-SEM results suggested that the nanoparticles are agglomerated and crystallite size increases with the annealing temperature. Magnetization measurements show that the La0.6Ca0.4MnO3 nanoparticles exhibit transition temperature (T(c)) below room temperature. The transition temperature was found to increase with the increasing the crystallite size. Maximum in magnetic entropy change, (ΔS(M))(max) shows interesting behaviour and was found to vary with the particle size. At magnetic field of 1 T, the value of (ΔS(M))(max) - 0.13 J/kg K was observed at 213 K for the sample annealed at 600 degrees C. Also, the increment in the value of (ΔS(M))(max) was observed at higher annealing temperature. This study shows that the magnetic entropy of pervoskite manganite can be tuned by tuning the crystallite size of the manganites.

Anomalous switching in Nb/Ru/Sr2RuO4 topological junctions by chiral domain wall motion.

A spontaneous symmetry breaking in a system often results in domain wall formation. The motion of such domain walls is utilized to realize novel devices like racetrack-memories, in which moving ferromagnetic domain walls store and carry information. Superconductors breaking time reversal symmetry can also form domains with degenerate chirality of their superconducting order parameter. Sr2RuO4 is the leading candidate of a chiral p-wave superconductor, expected to be accompanied by chiral domain structure. Here, we present that Nb/Ru/Sr2RuO4 topological superconducting-junctions, with which the phase winding of order parameter can be effectively probed by making use of real-space topology, exhibit unusual switching between higher and lower critical current states. This switching is well explained by chiral-domain-wall dynamics. The switching can be partly controlled by external parameters such as temperature, magnetic field and current. These results open up a possibility to utilize the superconducting chiral domain wall motion for future novel superconducting devices.

Morphological studies of SnO2 thin films fabricated by using e-beam method.

This paper studies the variations in morphology of SnO2 nanostructures thin films deposited by using e-beam technique with the substrate temperature, oxygen partial pressure and the film thickness. The e-beam conditions were optimized to get crystalline nanosheets of SnO2. The films of 100-700 nm thickness were deposited on quartz substrates at temperatures ranging from room temperature (RT) to 300 degrees C and oxygen partial pressure ranging from 0 to 200 sccm. The nanostructured films have been characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and Energy dispersive spectroscopy (EDS) measurements. XRD results show that the films deposited at RT and 100 degrees C were amorphous, however, for 200 degrees C and 300 degrees C, the films showed crystalline nature with rutile structure. Also, the crystallinity increased with the increase of oxygen partial pressure. FE-SEM images revealed that at RT and 100 degrees C of substrate temperature, the film consist of spherical particles, whereas, the films deposited at 200 degrees C and 300 degrees C consist of sheet like morphology having thickness -40 nm and lateral dimension of 1 microm, respectively. The size of the nanosheets increased with the increase of substrate temperature and oxygen partial pressure due to the enhancement in the crystallinity of the films. A possible growth mechanism of the formation of SnO2 nanosheets is discussed.

Neurological improvement following reinstitution of a low phenylalanine diet after 20 years in established phenylketonuria.

A 41-year-old woman had meaningful functional improvement following reinstitution of a low phenylalanine diet. She was diagnosed at birth with phenylketonuria and followed strict dietary adherence till the age of 16. Thereafter the diet was discontinued. She subsequently presented with subacute profound visual loss, cognitive dysfunction and paraparesis such that she was bed bound requiring full nursing care. Following dietary intervention there was meaningful improvement such that she was no longer demented and while her vision remains poor she is now independent for activities of daily living. This case report suggests that consideration of reimplementation of dietary intervention is warranted even after a prolonged period of time.

Magnetic, optical and structural property studies of Mn-doped ZnO nanosheets.

We report the synthesis of pure and Mn doped ZnO in the form of nanosheets using a simple and single step procedure involving a microwave assisted chemical method. As prepared Mn-doped ZnO nanosheets were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultra violet-visible (UV-Vis), Raman spectroscopy and magnetization measurements. The structural studies using XRD and TEM revealed the absence of Mn-related secondary phases and showed that Mn-doped ZnO comprise a single phase nature with wurtzite structure. FESEM and TEM micrographs show that the average diameter of Mn-ZnO assembled nanosheets is about approximately 50 nm, and the length of a Mn-doped ZnO nanosheet building block which is made up of thin mutilayered sheets is around approximately 300 nm. Concerning the Raman scattering spectra, the shift in peak position of E2 (high) mode toward low frequencies due to the Mn doping could be explained well by means of the spatial correlation model. Magnetic measurements showed that Mn-doped ZnO nanosheets exhibit ferromagnetic ordering at or above room temperature.

Microwave assisted hydrothermal synthesis and magnetocaloric properties of La0.67Sr0.33MnO3 manganite.

We report microwave assisted hydrothermal synthesis and magnetocaloric properties of La0.67Sr0.33MnO3 manganite. The synthesized La0.67Sr0.33MnO3 nanoparticles was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and magnetization measurements. The XRD results indicated that La0.67Sr0.33MnO3 nanoparticles have polycrystalline nature with monoclinic structure. FE-SEM results suggested that La0.67Sr0.33MnO3 nanoparticles are assembled into rod like morphology. Magnetization measurements show that La0.67Sr0.33MnO3 nanoparticles exhibit transition temperature (Tc) above room temperature. The maximum magnetic entropy change (deltaS(M))max was found to be 0.52 J/kg K near Tc approximately 325 K at applied magnetc field of 20 kOe. This compound may considered as potential material for magnetic refrigeration near room temperature.

Structural and magnetic properties of Zn1-xcoxO nanorods prepared by microwave irradiation technique.

We have successfully synthesized large-scale aggregative flowerlike Zn1-xCo(x)O (0.0 < or = x < or = 0.07) nanostructures, consisting of many branches of nanorods at different orientations with diameter within 100-150 nm (tip diameter approximately 50 nm) and length of approximately 1 microm. The rods were prepared using Zinc nitrate, cobalt nitrate and KOH in 180 Watt microwave radiation for short time interval. The synthesized nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and DC magnetization measurements. XRD and TEM results indicate that the novel flowerlike nanostructures are hexagonal with wurtzite structure and Co ions were successfully incorporated into the lattice position of Zn ions in ZnO matrix. The selected area electron diffraction (SAED) pattern reveals that the nanorods are single crystal in nature and preferentially grow along [0 0 1] direction. Magnetic studies show that Zn1-xCo(x)O nanorods exhibit room temperature ferromagnetism. This novel nanostructure could be a promising candidate for a variety of future spintronic applications.

One step synthesis of rutile TiO2 nanoparticles at low temperature.

Sphere-like rutile TiO2 nanocrystals have been synthesized by sol-gel method followed by hydrolysis of titanium tetrachloride in deionized water in the presence of ammonium hydroxide as hydrolysis catalyst. The as-prepared TiO2 nanoparticles have single rutile phase with average diameter approximately 26.4 nm. The results show that the temperature has a great influence on the particle size distribution and also crystalline phase (rutile) of TiO2 nanoparticles is consistent with the temperature. Characterization of the as-prepared nanocrystalline powder was carried out by different techniques such as powder X-ray diffraction (XRD), field emission transmission electron microscopy (FE-TEM) and Raman spectroscopy.