Analysis Of Magnetic Nanoparticles Research Articles

In-line monitoring of magnetic nanoparticles synthesis using reactor integrated on-chip magnetometer

The excellent multifunctional properties of magnetic nanoparticles (MNPs) allow them to be used in a wide range of applications. However, the required processes for the MNPs synthesis and characterization are still time-consuming and laborious, which further delays the research and development of the synthesis of MNPs. To overcome these difficulties, an on-chip magnetometer consisting of a planar Hall magnetoresistive (PHMR) sensor with a reactor was developed to optimize synthesis conditions for MNPs effectively. The microreactor was fabricated on the PHMR sensor, and the induced field from the synthesized magnetic particles was directly detected in the form of an output signal. Since the on-chip magnetometer enables simultaneous synthesis and measurement, it successfully monitored from the start point to the endpoint of the MNPs synthesis reaction. We studied the effect of the reagent ratio on the particle with iron chloride and aqueous ammonia solution, and we found the most suitable combination using a multi-array on-chip magnetometer. Experiments under various conditions were conducted simultaneously, and the experimental conditions were optimized in a short duration of time. Even though the synthesis reaction took place in a short time, the sensor's fast measurement rate and sensitivity allowed in-line measurement of the particle formation process. In addition, the developed on-chip magnetometer can be flexibly combined according to the desired configuration. Therefore, it is expected to be widely used as a new device for the simultaneous synthesis and analysis of MNPs.

Benchtop magnetic particle relaxometer for detection, characterization and analysis of magnetic nanoparticles

This paper presents the design, construction, and testing of a magnetic particle relaxometer (MPR) to assess magnetic nanoparticle response to dynamic magnetic fields while subjected to a bias field. The designed MPR can characterize magnetic particles for use as tracers in magnetic particle imaging (MPI), with the variation of an applied bias field emulating the scan of the MPI field free point. The system applies a high-frequency time-varying excitation field (up to 45 mT at 30 kHz), while slowly ramping a bias field (±100 mT in 1 s). The time-resolved response of the sample is measured using an inductive sensing coil system, made of a pick-up coil and a rotating and translating balancing coil to finely cancel the induction feed-through from the excitation field. A post-processing algorithm is presented to extract the tracer response related to the point spread function for MPI applications, and the performance of the MPR is demonstrated using superparamagnetic iron oxide particles (ferucarbotran).

Quantitative Analysis of Magnetic Nanoparticles by Means of Magnetic Force Microscopy

Magnetic force microscopy (MFM) is a powerful and simple tool to analyze magnetic materials and structures down to the nano-meter scale. However, there is still a demand for satisfactory models describing measured MFM data quantitatively, thereby allowing us to quantitatively analyze the magnetic properties of the sample. Here, we present an application of the recently proposed pseudo-pole model, which assumes that the tip can be represented by a cone covered homogeneously with dipoles pointing to the tip of the cone. Nano-composites of ferromagnetic Co nanoparticles (NPs) made by inert gas condensation and subsequently deposited non-magnetic SiO x cover layers with different layer thicknesses on single-crystalline Si substrates have been investigated in this paper. We extract quantitative information about the magnetization of individual NPs, as well as their depth below the surface of the SiO x films. In addition, we present an alternative method to extract information about the NP magnetic moment from the width of the NP signal in lift images, which does not require knowledge about the van der Waals interaction. We find good agreement between the magnetic moments determined by both approaches.

Analysis of magnetic nanoparticles using second harmonic responses

Magnetic particle imaging (MPI) is a new medical imaging technology with a number of potential applications. It is based on utilizing the non-linear magnetization response for magnetic nanoparticles (MNPs). We have proposed a method to improve the detection sensitivity for the magnetization of MNPs, and their imaging technique, based on the detection of a second harmonic of the response using a high Tc SQUID. The advantage of using the second harmonic is that the response can be measured even with small amplitudes. In this paper, superparamagnetic MNPs with different diameters and different compositions of materials were analyzed by this method. In the MNPs, Resovist was found to be almost one order of magnitude larger than that of the other MNPs tested. The magnetic moments of the MNPs were estimated by fitting with the Langevin function to obtain the magnetic moments m of Resovist of 3.62×10−18 [J/T]. The magnetic moment m of Resovist was 7.4 times larger than the other MNPs.

Preparation and Analysis of Magnetic Nanoparticles Used as Highly Active Catalysts over a Wide pH Range

In this work, Fe3O4 magnetic nanoparticles with high peroxidase-like catalytic activity and spontaneous pH adjustment ability were successfully prepared by co-precipitation method followed by appropriate thermal treatment. Key synthesis factors were identified and adjusted to tailor the crystallinity, chemical composition and then catalytic property. The crystal structure and Fe (II) content of the catalyst strongly affected its degradation efficiency. Phenol was completely removed by the optimal magnetic nanoparticles under a wide range of pH from 3.0 to 8.0. Additionally, this catalyst exhibited low iron leaching, good reusability and excellent potential to eliminate various organic pollutants from waste water. The reaction mechanism was discussed in terms of the formation of HO• and O2•−/HO2• radicals.

Nanoparticles as Smart Treatment-delivery Systems in Plants: Assessment of Different Techniques of Microscopy for their Visualization in Plant Tissues

The great potential of using nanodevices as delivery systems to specific targets in living organisms was first explored for medical uses. In plants, the same principles can be applied for a broad range of uses, in particular to tackle infections. Nanoparticles tagged to agrochemicals or other substances could reduce the damage to other plant tissues and the amount of chemicals released into the environment. To explore the benefits of applying nanotechnology to agriculture, the first stage is to work out the correct penetration and transport of the nanoparticles into plants. This research is aimed (a) to put forward a number of tools for the detection and analysis of core-shell magnetic nanoparticles introduced into plants and (b) to assess the use of such magnetic nanoparticles for their concentration in selected plant tissues by magnetic field gradients. Cucurbita pepo plants were cultivated in vitro and treated with carbon-coated Fe nanoparticles. Different microscopy techniques were used for the detection and analysis of these magnetic nanoparticles, ranging from conventional light microscopy to confocal and electron microscopy. Penetration and translocation of magnetic nanoparticles in whole living plants and into plant cells were determined. The magnetic character allowed nanoparticles to be positioned in the desired plant tissue by applying a magnetic field gradient there; also the graphitic shell made good visualization possible using different microscopy techniques. The results open a wide range of possibilities for using magnetic nanoparticles in general plant research and agronomy. The nanoparticles can be charged with different substances, introduced within the plants and, if necessary, concentrated into localized areas by using magnets. Also simple or more complex microscopical techniques can be used in localization studies.

Capillary Magnetic Field Flow Fractionation and Analysis of Magnetic Nanoparticles

This paper reports the purification and analysis of magnetic nanoparticles using capillary magnetic field flow fractionation, which utilizes an applied magnetic field oriented orthogonal to the capillary flow. To validate this approach as a separation method for nanometer-scale particles, samples of magnetic nanoparticles composed of either gamma-Fe2O3 (maghemite) or CoFe2O4 with average diameters ranging from 4 to 13 nm were prepared and characterized by transmission electron microscopy and SQUID magnetometry. Retention of the samples on the capillary was investigated as a function of solvent flow rate and the nanoparticle size and composition; the elution times of the nanoparticles are strongly dependent on their magnetic moments. We demonstrate the use of this method to separate a mixture of nanoparticles into size-monodisperse fractions. The magnetic moments of the particles are calculated based on analysis of the retention parameters and correlate with values obtained in separate SQUID magnetometry measurements.