The effect of the particle size and magnetic moment of the Fe3O4 superparamagnetic beads on the sensitivity of biodetection

In recent years, the quantitative detection of biomolecules based on Giant magnetoresistive (GMR) sensors and magnetic nanoparticles have received continuous attention. Researchers try to improve the accuracy of detection by various methods, including using a more sensitive sensor, designing circuit to reduce system noise, and so on. In which, the intrinsic properties of magnetic labels, such as the particle size of labels is a vital aspect for the GMR biosensing technology. In this work, a series of Fe3O4 particles with average particle sizes from 80 to 580 nm were prepared for exploring the effect of particle size on the limit of detection (LOD). An ultra-low LOD of 0.1 ng/mL was obtained for small particles with average sizes from 80 to 200 nm detected by our home-made biodetection device. However, for the ones with large sizes from 330 to 580 nm, the LOD increases with the increase of particle size. The total magnetic moments of all particles attached on the sensor surface Σmm are calculated theoretically and compared with the experimental data of the normalized voltage ratio (Vnvr=|ΔV|/V0×100%) over particle size. It is found that not only the particle size but also the magnetic moment of particles affect the LOD of the concentration

Static and Dynamic Magnetic Properties of FeGa/FeNi (FeNi/FeGa) Bilayer Structures

FeGa/FeNi bilayer structures with different deposition order were fabricated by the electrodeposition method on indium tin oxide (ITO) substrates. The structure, morphology, static and dynamic magnetic properties of FeGa/FeNi (FeNi/FeGa) films were investigated. The bilayer structures exhibit extremely various magnetic properties with different deposition order which could be attributed to the different coupling interaction in the interface. When FeGa is on top, the bilayer structures show lower coercivity than when FeNi is on top. Meanwhile, increase of the proportion of FeNi in the bilayer structure could affect the Hc and Mr/Ms. The ferromagnetic resonance peak of FeGa on top moves to a high field compared with FeNi on top. Moreover, FeGa on top shows improved complex permeability and a clear resonant phenomenon of the magnetization. These properties make FeGa/FeNi bilayer structure a potential candidate for high-frequency application

Magnetization relaxation dynamics in [ Co / Pt ] 3 multilayers on pico- and nanosecond timescales

We experimentally investigated magnetization relaxation dynamics in the largely unexplored time window extending from few picoseconds up to two nanoseconds following femtosecond laser pulse excitation. We triggered magnetization dynamics in [Co(0.4nm)/Pt(0.7nm)]3 multilayers and measured the resulting magneto-optic response by recording both transient hysteresis loops as well as transients of magnetization dynamics. We observe that the coercive field of the sample is still strongly suppressed even ∼1 ms after the laser excitation, which is three orders of magnitude longer than the recovery time of the magnetization amplitude. In addition, we succeeded to fit the magnetization relaxation data in the entire experimentally observed time window by considering two phenomenological time constants τ∗f and τ∗s describing fast (ps) and slow (ns) magnetization relaxation processes, respectively. The fits of the data suggest a magnetic field dependent relaxation slowdown beyond 100 ps after excitation. We observe an explosion of the τ∗f and τ∗s values when the magnetization is completely quenched and relaxes intrinsically in the absence of an external magnetic field. We interpret the phenomenological time constants τ∗f and τ∗s using an intuitive physical picture based on the Landau-Lifshitz-Bloch model and numerical solutions of the extended three-temperature model [Shim et al., Sci. Rep. 10, 6355 (2020)]

Transcriptome profiling of Sorghum bicolor reveals cultivar-specific molecular signatures associated with starch and phenolic compounds biosyntheses and accumulation during sorghum grain development

Sorghum is an important crop, and starch and phenolic compounds are major and important components in the sorghum grain. However, the underlying critical genetic elements contributing to the rich portfolio of nutrients in sorghum grains are largely unknown. Transcriptomic methods were employed to characterize the expression patterns at five different grain developmental stages of Hongyingzi (an important brewing sorghum), and another two grain sorghums, Jinuoliang 1 and Hongliangfeng 1, for comparison. The uniquely expressed genes were identified at each developmental stage of Hongyingzi when compared with the other two sorghum cultivars. The co-regulated genes at different developmental stages and the regulatory network were determined; the determinant genes and single-nucleotide polymorphisms located at the promoters of these genes involved in starch and phenolic compounds biosynthetic pathways were also identified. These results will provide insights into the potential regulatory network and further contribute to the clarification of the key determinant genes involved in the biosyntheses of starch and phenolic compounds. Meanwhile, some new transcripts and genes were identified at five different developmental stages of grains of the three sorghum cultivars. Our work can provide impetus for further study of the genes responsible for the biosynthesis of starch and phenolic compounds in the sorghum grain, and pave a way for functional validation of a batch of potential genes and single-nucleotide polymorphisms proposed in current work

A Nanocrystalline Fe2O3 Film Anode Prepared by Pulsed Laser Deposition for Lithium-Ion Batteries

Abstract Nanocrystalline Fe2O3 thin films are deposited directly on the conduct substrates by pulsed laser deposition as anode materials for lithium-ion batteries. We demonstrate the well-designed Fe2O3 film electrodes are capable of excellent high-rate performance (510 mAh g− 1 at high current density of 15,000 mA g− 1) and superior cycling stability (905 mAh g− 1 at 100 mA g− 1 after 200 cycles), which are among the best reported state-of-the-art Fe2O3 anode materials. The outstanding lithium storage performances of the as-synthesized nanocrystalline Fe2O3 film are attributed to the advanced nanostructured architecture, which not only provides fast kinetics by the shortened lithium-ion diffusion lengths but also prolongs cycling life by preventing nanosized Fe2O3 particle agglomeration. The electrochemical performance results suggest that this novel Fe2O3 thin film is a promising anode material for all-solid-state thin film batteries

Tuning high frequency magnetic properties and damping of FeGa, FeGaN and FeGaB thin films

A series of FeGa, FeGaN and FeGaB films with varied oblique angles were deposited by sputtering method on silicon substrates, respectively. The microstructure, soft magnetism, microwave properties, and damping factor for the films were investigated. The FeGa films showed a poor high frequency magnetic property due to the large stress itself. The grain size of FeGa films was reduced by the additional N element, while the structure of FeGa films was changed from the polycrystalline to amorphous phase by the involved B element. As a result, N content can effectively improve the magnetic softness of FeGa film, but their high frequency magnetic properties were still poor both when the N2/Ar flow rate ratio is 2% and 5% during the deposition. The additional B content significantly led to the excellent magnetic softness and the self-biased ferromagnetic resonance frequency of 1.83 GHz for FeGaB film. The dampings of FeGa films were adjusted by the additional N and B contents from 0.218 to 0.139 and 0.023, respectively. The combination of these properties for FeGa films are helpful for the development of magnetostrictive microwave devices

Nano-LED driven phase change evolution of layered chalcogenides for Raman spectroscopy investigations

We present a device driving testing platform based on vertically integrated nano light emitting diodes (nano- LEDs). The nano-LEDs with a peak wavelength emission centered at ~ 445 nm were arranged in arrays and conditioned using a laser-micro-annealing process to individually tune their intensity. They were coupled with freestanding monocrystalline Ge1Sb2Te4 nano-membranes with three different thicknesses (~40, ~ 60 and ~ 90 nm) with the aim of initializing ultrafast switching processes and of observing phase changed states simulta- neously by Raman spectroscopy. Raman spectroscopy studies reveal that the optical pulses emitted from the nano-LEDs induce substantial, local changes in the nano-membranes’ states of the Ge1Sb2Te4 layered material. Beside the crystalline state in non-exposed areas (as-grown material), amorphous and different intermediate states were identified in exposed areas as island-like structures with diameters ranging from ~ 300 nm up to ~ 1.5 µm. The latter confirms the nano-LEDs’ emission role in both near- and far-field regimes, depending on the distance between nano-LED and nano-membrane, for driving i.e. inducing the phase change process. The results presented demonstrate the suitability and potential of the vertically integrated nano-LEDs as the key components for a testing platform/for electro-optical convertors driving phase change processes in optically active media. They could also play an important role in the development of future, e.g., non-volatile data storage as well as in optical and neuromorphic computing architectures based on transmistor devices

Coherent GHz lattice and magnetization excitations in thin epitaxial Ag/Fe/Cr/Fe films

We excited an epitaxial magnetic Ag/Fe/Cr/Fe multilayer nonthermally and nonoptically with very short (<1 ps) electromagnetic pulses. We detected the synchronous phononic-magnetic response by time-resolved magneto-optical Kerr effect measurements. The Ag/Fe/Cr/Fe multilayer was patterned into a coplanar waveguide transmission line, and the electromagnetic pulses were generated by pulsed-laser illumination of an integrated GaAs photoconductive switch (PCS). The detected magnetic excitations comprise up to four narrow-band high-order modes with the highest frequency reaching 30 GHz. The mode frequencies are independent of both temperature in the range from 16 to 300 K and the applied external magnetic field up to 120 mT. Our analysis shows that the origin of the rigidity of these high-frequency modes is the strong coupling of the magnetic subsystem with the lattice of the Ag/Fe/Cr/Fe multilayer. The exciting electromagnetic pulse generated by the PCS induces, via magnetoelastic coupling, long-lived (ns) standing GHz acoustic waves normal to the Ag/Fe/Cr/Fe film plane. These lattice oscillations in turn couple back and drive the magnetization oscillations via the magnetoelastic coupling. The temperature and field dependence of the damping of the oscillations can be described by inelastic phonon-phonon and phonon-magnon scattering. Our study opens up a possibility of using coherent lattice and magnetization dynamics in ferromagnetic films for spintronic devices at GHz clock rates