Superconducting Quantum Interference Device Analysis Research Articles

Stable Inner 2H Tautomer of N-Confused-like Porphyrin Embedded with a Carbazole Subunit: Synthesis, Metal Coordination, and Magnetic and Anion Sensing Studies.

A new class of N-confused porphyrin 1 embedded with a carbazole subunit was prepared via [3 + 1] acid-catalyzed condensation of appropriate precursors. 1 underwent smooth metal complexation with Pd(II) and Cu(II) salts to provide the corresponding diamagnetic 1-Pd and paramagnetic 1-Cu, respectively. The single-crystal X-ray structure of 1-Pd is evident with a square-planar Pd-center through C-H activation of inverted pyrrole. Superconducting quantum interference device analysis combined with electron paramagnetic resonance (EPR) results provided insights into the paramagnetic nature of 1-Cu. Further, a ratiometric enhancement of near-IR fluorescence at 746 nm was found to be reversible upon adding CN- and F- ions. The solid-state structure of 1-Pd confirms that the anionic species is due to NH deprotonation.

Air Stable Chalcogen-Doped Rubicenes with Diradical Character

Air Stable Chalcogen-Doped Rubicenes with Diradical Character

Polyacrylate grafted graphene oxide nanocomposites for biomedical applications

Utilizing a reverse micelle process, we have grafted polyacrylate (P) on graphene oxide (GO) to realize polyacrylate grafted graphene oxide (P-GO) nanocomposites, upon whose subsequent reduction, polyacrylate grafted reduced graphene oxide (P-rGO) nanocomposites are achieved. Using techniques such as ultraviolet photoelectron spectroscopy (UPS), x-ray photoelectron spectroscopy, and x-ray absorption near edge structure (XANES) spectroscopy, in conjunction with high-resolution microscopy, Raman spectroscopy, and superconducting quantum interference device analysis, we have studied in depth the electronic, microstructural, electrical, and magnetic properties of these P-GO and P-rGO nanocomposites. While polyacrylate grafting ensures a high solubility of P-GO and P-rGO, the P-rGO nanocomposites additionally show a near doubling of the paramagnetic response (9.6 × 10−3 emu/g) as compared to the r-GO (5.6 × 10−3 emu/g) and P-GO (5.5 × 10−3 emu/g), respectively, at 2 K. The grafting of diamagnetic polyacrylate enhances the magnetic response for the P-GO and P-rGO owing to the increase in the defect states, sp3-type bonding, and enhanced magnetic coupling between the magnetic moments arising due to the presence of nitrogen functionalities. This behavior is further corroborated via the measurements of the electronic structure by XANES and UPS measurements. Thus, the possibility of manipulation of the magnetic behavior along with the abundance of surface functional groups makes both P-GO and P-rGO nanocomposites highly conducive for deriving water-soluble functionalized graphene by linking affinity molecules with polyacrylate backbone for biological and biomedical applications.

Effect of Cu2+ substitution on structural and magnetic properties of Ni–Zn ferrite nanopowders

In this study copper substituted nickel–zinc ferrite powders with the general composition Ni0.6−xCuxZn0.4Fe2O4 (x = 0, 0.05, 0.1, 0.15, 0.2, and 0.25) were prepared via auto-combustion sol–gel method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy, Mossbauer spectroscopy, vibrating sample magnetometer (VSM) and superconducting quantum interference device analysis were carried out in order to characterize the structural and magnetic properties of particles. The XRD results confirmed the formation of single phase spinel ferrite particles for all of the samples. The results of FTIR analysis indicated that the there are two main frequency bands, namely, the high frequency band observed at ~577 cm−1 and the low frequency band observed at ~450 cm−1. These two bands correspond to the intrinsic vibrations of tetrahedral and octahedral Fe3+–O2− complexes, respectively, and are the characteristics of all the ferrite materials. The size of particles was around 80–800 nm. The VSM results revealed that with an increase in the amount of copper in ferrites, the saturation magnetization increased. Saturation magnetization increased to 97 emu/g for x = 0.05 at room temperature and increased to 261 emu/g for x = 0 and 0.05 at 2 K. The results indicated that the powder is suitable for the application in multilayer chip inductor due to its low temperature sinterability and good magnetic properties.

L10-FePt films fabricated by wet-chemical route

In this work, we have developed a method to fabricate FePt films by a combination of chemical deposition and post-annealing. Pt-doped Fe films were deposited on Pt(100nm)/Ti(50nm)/SiO2/Si substrate using thermal deposition and the as-deposited films were subsequently annealed from 300°C to 800°C under 5% H2/95% N2. FePt films were achieved through diffusion and rearrangement of Fe and Pt atoms in post-annealing process. From X-ray diffraction results, the face-centered cubic (fcc) FePt phase appeared at 300°C and the transformation from fcc to L10 phase started at 400°C. The L10-FePt film possessed an out-of-plane anisotropy and a coercivity of 729kA/m after annealing at 600°C. A further increase in annealing temperature led to lower value of coercivity, probably because of grain growth. In addition, the thickness of Pt-doped Fe films could be controlled from 150nm to 700nm by adjusting the amount of surfactant used. Our superconducting quantum interference device analysis showed that Pt dopant could significantly improve the chemical stability of Fe films in air.

Phase transformation in Mn-doped titania hollow spheres and their biocompatibility studies

Mn-doped titania hollow nanospheres were prepared via sacrificial core templating method at room temperature, using carbon spheres as the sacrificial core and template. X-ray diffraction and thermal studies showed the phase transformation of titania from anatase to rutile at temperature as low as 550 °C, when the dopant (i.e., Mn) concentration was increased from 1 to 6 mol % (with respect to Ti). Fourier transform infra red spectroscopic studies have been carried out to determine the surface functional groups, while the spherical and hollow morphology of the titania nanostructures have been confirmed through scanning electron microscopic as well as transmission electron microscopic studies. The chemical composition of the samples has been determined through X-ray photoelectron spectroscopic studies, while their magnetic properties have been studied using superconducting quantum interference device analysis. The biocompatibility and suitability of the nanospheres for intracellular applications has been tested through conventional MTT assay using MDA-MB 231 human breast cancer cell lines.

Synthesis and characterization of cobalt-substituted hydroxyapatite powders

The crystal structure of hydroxyapatite lends itself to a wide variety of substitutions and ion doping, which allows for tailoring of material properties. Magnetic properties are one area of interest in which substitutions can be used to tailor hydroxyapatite properties. Pure HA is diamagnetic, but metal ion doping may lead to a magnetic apatite. In this study, cobalt doped hydroxyapatite was synthesized via two methods: a simple ion-exchange procedure and wet synthesis. The resulting materials were characterized thoroughly for crystal structure and phase purity using X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Magnetic properties were studied using vibrating sample magnetometer and superconducting quantum interference device analysis. The degradation behavior and cobalt release of pure HA and CoHA in simulated body fluid was also examined. The results showed that after both cobalt substitution methods the powder retained characteristic apatite crystal structure and functional groups. Cobalt substituted samples displayed paramagnetic properties, as opposed to the diamagnetism of pure HA. Degradation studies showed that CoHA did not display markedly different degradation behavior from pure HA and the amount of cobalt released over the course of a month was extremely low, alleviating toxicity concerns. Cobalt substituted hydroxyapatite nanoparticles, a biomaterial with magnetic properties, could be a promising material to be used in a variety of biomedical applications, including magnetic imaging, drug delivery, or hyperthermia based cancer treatments.

An Approach for Enhancement of Saturation Magnetization in Cobalt Ferrite Nanoparticles by Incorporation of Terbium Cation

Cobalt ferrite nanoparticles were synthesized by a reverse micelle process. The optimum processing conditions required to fabricate nanocrystalline cobalt ferrite using a reverse micelle technique, especially the effect of water-to-surfactant molar ratios including w = 8, 10, 12, and 14, pH values in the range of 8 to 11, and annealing temperatures in the range of 400°C to 800°C, were evaluated. x-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), vibrating-sample magnetometry, and superconducting quantum interference device analysis were employed to evaluate the structural and magnetic properties of synthesized nanoparticles. XRD analysis confirms that the nanoparticles have a single-phase cubic spinel structure. The average particle size increases with increasing pH value and annealing temperature. Magnetization study reveals that the cobalt ferrite nanoparticles exhibit a superparamagnetic trend. The zero-field-cooled magnetization curves of cobalt ferrite nanoparticles indicated that, with an increase in pH value, the blocking temperature increases. Based on the obtained optimum parameters, terbium-substituted cobalt ferrite nanoparticles with composition CoFe2−xTbxO4 (x = 0.1 to 0.5) were prepared by a reverse micelle process. XRD and field-emission scanning electron microscopy evaluation demonstrated that single-phase spinel ferrites with narrow size distribution were obtained. Mossbauer spectroscopy was used to determine the site preference of terbium cation. The results confirm that terbium cations were distributed at tetrahedral and octahedral sites, but with a preference for the former. It was observed that, with an increase in terbium content, the saturation magnetization increases.

Structural, morphological and magnetic properties of AlGaN thin films co-implanted with Cr and Sm ions

Cr and Sm co-implanted AlGaN (AlGaN:Cr:Sm) films have been fabricated by metal organic chemical vapor deposition, ion implantation and annealing. No secondary phase and metal-related peak can be detected within the detection limit of X-ray diffraction measurement. The Raman analysis demonstrated that the peak of E2 (H) phonon mode of sample B is much more narrow and sharp than that of sample A. The atomic force microscopy measurements indicated that the root mean square roughness for sample A and sample B were 2.26 and 1.07nm, respectively. According to superconducting quantum interference device analysis, the AlGaN:Cr:Sm films exhibit room-temperature ferromagnetism and colossal magnetic moment effect. Moreover, the saturation magnetization of sample B is 9.75μB/atom, which is much higher than that of sample A (1.86μB/atom). Finally, the possible origin of the room-temperature ferromagnetism in AlGaN:Cr:Sm films was discussed.

Synthesis and characterization of iron-substituted hydroxyapatite via a simple ion-exchange procedure

Hydroxyapatite (HA), the main inorganic component of natural bones, is widely studied as a biomaterial due to its excellent biocompatibility and osteoinductivity. The crystal structure of HA lends itself to a wide variety of substitutions and ion doping, which allows for tailoring of material properties. In this study, iron-doped HA was synthesized via a simple ion-exchange procedure and characterized thoroughly for crystal structure and phase purity using X-ray diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, and Fourier transform infrared spectroscopy. Magnetic properties were studied using vibrating sample magnetometer and superconducting quantum interference device analysis. Ion-exchange was attempted using both ferric and ferrous chloride iron solutions, but a substitution was only achieved using ferric chloride solution. The results showed that after iron substitution the powder retained characteristic apatite crystal structure and functional groups, but the iron-doped samples displayed paramagnetic properties, as opposed to the diamagnetism of pure HA. The effect of soaking time on iron content was also examined, and collectively X-ray diffraction and inductively coupled plasma atomic emission spectroscopy results suggested that an increase in soaking time led to an increase in iron content in the sample powder. Iron-substituted HA nanoparticles, a biomaterial with magnetic properties, could be a promising biomaterial to be used in a variety of biomedical fields, including magnetic imaging, drug delivery, or hyperthermia-based cancer treatments.

Fabrication of Aligned Magnetic Nanoparticles Using Tobamoviruses

We used genetically modified tube-shaped tobamoviruses to produce 3 nm aligned magnetic nanoparticles. Amino acid residues facing the central channel of the virus were modified to increase the number of nucleation sites. Energy dispersive X-ray spectroscopy and superconducting quantum interference device analysis suggest that the particles consisted of Co-Pt alloy. The use of tobamovirus mutants is a promising approach to making a variety of components that can be applied to fabricate nanometer-scaled electronic devices.

Preparation of Ni-filled carbon nanotubes for key potential applications in nanotechnology

Carbon nanotubes (CNTs) filled with ferromagnetic materials have the potentials for use in magnetic scanning probe microscopy and as an assembly of aligned high density magnetic nanocores for future magnetic data storage devices. Highly ordered and uniform Ni-filled CNTs were deposited by chemical vapour deposition. As-grown Ni-filled CNTs were characterized using transmission electron microscopy, Raman spectroscopy and nano-area diffraction. The magnetic properties of Ni-filled CNTs were investigated using superconducting quantum interference device analysis. Magnetisation characterization, performed at temperature 2 K with magnetic field up to 2 T, showed better ferromagnetism compared to the bulk Ni.