Magnetic Heating Research Articles

Photo-induced processes of iron oxide nanoparticles to enhance laser therapy

Nanoparticles are used as drug carriers to increase the selectivity and effectiveness of therapy, as well as for combined therapy that utilizes different effects. Iron oxide nanoparticles are promising in this aspect. Due to magnetic properties, they can be used as a contrast agent for magnetic resonance imaging. Also, iron oxide nanoparticles could be coated with a photosensitizer for photodynamic therapy and their laser or magnetic heating can be used for phototherapy. Local enhancement of the electromagnetic field near iron oxide nanoparticles can increase the fluorescence intensity of photosensitizers and the efficiency of singlet oxygen generation. This paper presents the results of a study of iron oxide nanoparticles focused on the photophysical aspects of the formation of “hot spots” under laser irradiation. The photoinduced effects of iron oxide nanoparticles observed in in vitro experiments lead to the rupture of lysosomes. Theoretical modeling showed that the heating of iron oxide nanoparticles with a radius of 35 nm under the action of laser radiation is about 89°C and 19°C for wavelengths of 458 and 561 nm, respectively. Local field enhancement occurs in pairs of nanoparticles of various sizes and strongly depends on the distance between them. The maximum gain is achieved at small distances between nanoparticles. For a dimer of nanoparticles with radii of 10 and 35 nm at a distance of 1 nm, an enhancement factor of two orders of magnitude was obtained. The investigated phenomenon of «hot spots» is in demand for precision therapy, because the photo-induced processes occur at small distances between nanoparticles, in areas of their high accumulation.

Spatial matching relationship of dual heat sources in electromagnetic heating of pipes

• Dual heat sources reduce the probability of latent defects in electromagnetic heating. • The mechanism of the interference of dual heat sources on the induced magnetic field. • Reveal the spatial matching relationship of dual heat sources under moving conditions. In medium-frequency heat treatment, it is difficult to thoroughly heat the interior of welds of heavy-wall pipes, and blind zones of heating or overheating zones with latent defects are very readily present. To solve the electromagnetic-heating-induced latent defects, we researched the mode of heat transfer inside the welds with heat sources under motion conditions to determine the temperature field evolution, spatial magnetic field distribution, and spatial matching relationship in cases of dual heat sources interfering with each other, tangential to each other, and not interfering with each other. With the increase in the axial spacing between the internal and external heat sources, the magnetic field intensity at the middle of the thickest part of the welding seam on the steel pipe increased and then decreased. When the heat sources interfered with each other, the temperature rise at the weld center from electromagnetic heating was no longer fast after the Curie point was reached. The induced magnetic field heating concentration positions shifted toward both sides of the weld center. The latent defect area was reduced by 18.7 mm 2 when the spacing between the internal and external heat sources was 19 mm. This study explores the dual-heat-source interaction mechanism for the first time in the heat treatment of pipes to minimize the blind zones of heating and overheating zones.

The Sloan Digital Sky Survey Reverberation Mapping Project: UV–Optical Accretion Disk Measurements with the Hubble Space Telescope

Abstract We present accretion-disk structure measurements from UV–optical reverberation mapping (RM) observations of a sample of eight quasars at 0.24 < z < 0.85. Ultraviolet photometry comes from two cycles of Hubble Space Telescope monitoring, accompanied by multiband optical monitoring by the Las Cumbres Observatory network and Liverpool Telescopes. The targets were selected from the Sloan Digital Sky Survey Reverberation Mapping project sample with reliable black hole mass measurements from Hβ RM results. We measure significant lags between the UV and various optical griz bands using JAVELIN and CREAM methods. We use the significant lag results from both methods to fit the accretion-disk structure using a Markov Chain Monte Carlo approach. We study the accretion disk as a function of disk normalization, temperature scaling, and efficiency. We find direct evidence for diffuse nebular emission from Balmer and Fe ii lines over discrete wavelength ranges. We also find that our best-fit disk color profile is broadly consistent with the Shakura & Sunyaev disk model. We compare our UV–optical lags to the disk sizes inferred from optical–optical lags of the same quasars and find that our results are consistent with these quasars being drawn from a limited high-lag subset of the broader population. Our results are therefore broadly consistent with models that suggest longer disk lags in a subset of quasars, for example, due to a nonzero size of the ionizing corona and/or magnetic heating contributing to the disk response.

Thickness Dependent Microwave Magnetic Field Heating on Aluminum thin Films by Using Thermo-elastic Optical Indicator Microscopy Method

Thickness Dependent Microwave Magnetic Field Heating on Aluminum thin Films by Using Thermo-elastic Optical Indicator Microscopy Method

Impact of the agarose ferrogel fine structure on magnetic heating efficiency

Magnetic nanoparticles-mediated hyperthermia was widely studied in the last decades as applicable in cancer therapy. The majority of magnetic hyperthermia research was devoted to improvement of heating efficiency by application of various nanomaterials. The influence of biocompatibility, magnetic properties, sizes, composition, and concentration of magnetic nanoparticles (MNPs) on hyperthermia efficiency was extensively studied. Also, the limits preserving biological safety and the chemical stability of MNPs delivered to the tissue were established. However, much less research concerned the impact of the physical interactions between the closest MNPs on the hyperthermia efficiency. Our goal was to demonstrate the relationships between the internal structure of soft tissue containing MNPs, and the thermal effects of an alternating magnetic field. Because agarose-based gel exhibits a tissue-like internal structure, we performed hyperthermia experiments in two types of such gel containing bare and polyethylene glycol-coated Fe3O4 nanoparticles. We described the structural difference and we estimated the ferrogels specific absorption rate coefficients (SAR) from calorimetric experiments. Magnetic measurements showed 11% lower magnetic saturation of PEG-coated MNPs than of the bare MNPs. While the SAR of ferrogel with PEG-coated MNPs was 15% greater than bare MNPs. The structural characteristics calculated from TEM and SEM images were significantly different. Particularly, we observed the nanoparticle agglomeration in the gel with bare MNPs. The bare MNPs uniformly packed and located inside agarose double helices were observed for the first time. The distribution of MNPs and their spatial configuration in gel influenced strongly the strength of bonds blocking the movement of MNPs and determined the ferrogels heating efficiency. As the tissues to which we delivered MNPs were composed of agarose gel-like structures, our results may be useful in further research on hyperthermia in vivo.

Magnetic Nanoparticle-Mediated Heating for Biomedical Applications.

Magnetic nanoparticles, especially superparamagnetic nanoparticles (SPIONs), have attracted tremendous attention for various biomedical applications. Facile synthesis and functionalization together with easy control of the size and shape of SPIONS to customize their unique properties, have made it possible to develop different types of SPIONs tailored for diverse functions/applications. More recently, considerable attention has been paid to the thermal effect of SPIONs for the treatment of diseases like cancer and for nanowarming of cryopreserved/banked cells, tissues, and organs. In this mini-review, recent advances on the magnetic heating effect of SPIONs for magnetothermal therapy and enhancement of cryopreservation of cells, tissues, and organs, are discussed, together with the non-magnetic heating effect (i.e., high Intensity focused ultrasound or HIFU-activated heating) of SPIONs for cancer therapy. Furthermore, challenges facing the use of magnetic nanoparticles in these biomedical applications are presented.

Magnetic Induction Assisted Heating Technique in Hydrothermal Zeolite Synthesis.

The magnetic induction assisted technique is an alternative heating method for hydrothermal zeolite synthesis with a higher heat-transfer rate than that of the conventional convection oil bath technique. The research demonstrates, for the first time, the application of the magnetic induction heating technique with direct surface contact for zeolite synthesis. The magnetic induction enables direct contact between the heat source and the reactor, thereby bypassing the resistance of the heating medium layer. A comparative heat-transfer analysis between the two methods shows the higher heat-transfer rate by the magnetic induction heating technique is due to (1) eight-time higher overall heat-transfer coefficient, attributed to the absence of the resistance of the heating medium layer and (2) the higher temperature difference between the heating source and the zeolite gel. Thereby, this heating technique shows promise for application in the large-scale synthesis of zeolites due to its associated efficient heat transfer. Thus, it can provide more flexibility to the synthesis method under the non-stirred condition, which can create possibilities for the successful large-scale synthesis of a broad range of zeolites.

Tailoring Interfacial Exchange Anisotropy in Hard-Soft Core-Shell Ferrite Nanoparticles for Magnetic Hyperthermia Applications.

Magnetically hard–soft core-shell ferrite nanoparticles are synthesized using an organometallic decomposition method through seed-mediated growth. Two sets of core-shell nanoparticles (S1 and S2) with different shell (Fe3O4) thicknesses and similar core (CoFe2O4) sizes are obtained by varying the initial quantities of seed nanoparticles of size 6.0 ± 1.0 nm. The nanoparticles synthesized have average sizes of 9.5 ± 1.1 (S1) and 12.2 ± 1.7 (S2) nm with corresponding shell thicknesses of 3.5 and 6.1 nm. Magnetic properties are investigated under field-cooled and zero-field-cooled conditions at several temperatures and field cooling values. Magnetic heating efficiency for magnetic hyperthermia applications is investigated by measuring the specific absorption rate (SAR) in alternating magnetic fields at several field strengths and frequencies. The exchange bias is found to have a nonmonotonic and oscillatory relationship with temperature at all fields. SAR values of both core-shell samples are found to be considerably larger than that of the single-phase bare core particles. The effective anisotropy and SAR values are found to be larger in S2 than those in S1. However, the saturation magnetization displays the opposite behavior. These results are attributed to the occurrence of spin-glass regions at the core-shell interface of different amounts in the two samples. The novel outcome is that the interfacial exchange anisotropy of core-shell nanoparticles can be tailored to produce large effective magnetic anisotropy and thus large SAR values.

Improved Suzuki\u2013Miyaura reaction conversion efficiency using magnetic nanoparticles and inductive heating

The use of magnetic nanoparticles in C–C coupling reactions enables the facile recovery of the catalyst under environmentally friendly conditions. Herein, the synthesis of Pd/Fe@Fe3O4 nanoparticles by the reduction of Pd2+ and oxidation of Fe on the surface of preformed Fe@Fe3O4 is reported. The nanoparticles were characterized using a variety of analytical techniques (transmission electron microscopy, Mössbauer spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction) to determine their size, structure, and chemical composition. The catalytic efficiency of these nanoparticles in classical Suzuki–Miyaura coupling reactions was investigated. The nanoparticles achieved high catalytic activity with the application of local heating by an alternating magnetic field. An investigation was conducted at identical temperatures to compare global heating with the application of an external magnetic field; magnetic heating demonstrated excellent substrate conversion in lesser time and at a lower temperature. The catalyst could also be recycled and reused three times, with ~ 30% decrease in the substrate conversion, which is most likely due to the agglomeration of the Pd nanoparticles or poisoning of the Pd catalyst. This approach, which takes advantage of the catalytic activity and magnetic susceptibility of magnetic nanoparticles, can be applied to several organic transformations to improve their efficiency.Graphical abstract

Controllable Synthesis of Superparamagnetic Magnetic Iron Oxide Nanoparticles and Induction Heating Studies: A Comprehensive Chemistry Experiment

Controllable Synthesis of Superparamagnetic Magnetic Iron Oxide Nanoparticles and Induction Heating Studies: A Comprehensive Chemistry Experiment

Superhydrophobic Aerogel Blanket with Magnetic and Solar Heating Effect Enables Efficient Continuous Cleanup of Highly Viscous Crude Oil

Superhydrophobic Aerogel Blanket with Magnetic and Solar Heating Effect Enables Efficient Continuous Cleanup of Highly Viscous Crude Oil

Ultrafast Preparation of Nonequilibrium FeNi Spinels by Magnetic Induction Heating for Unprecedented Oxygen Evolution Electrocatalysis.

Carbon-supported nanocomposites are attracting particular attention as high-performance, low-cost electrocatalysts for electrochemical water splitting. These are mostly prepared by pyrolysis and hydrothermal procedures that are time-consuming (from hours to days) and typically difficult to produce a nonequilibrium phase. Herein, for the first time ever, we exploit magnetic induction heating-quenching for ultrafast production of carbon-FeNi spinel oxide nanocomposites (within seconds), which exhibit an unprecedentedly high performance towards oxygen evolution reaction (OER), with an ultralow overpotential of only +260 mV to reach the high current density of 100 mA cm−2. Experimental and theoretical studies show that the rapid heating and quenching process (ca. 103 K s−1) impedes the Ni and Fe phase segregation and produces a Cl-rich surface, both contributing to the remarkable catalytic activity. Results from this study highlight the unique advantage of ultrafast heating/quenching in the structural engineering of functional nanocomposites to achieve high electrocatalytic performance towards important electrochemical reactions.

Catalytic activity of magnetite and its magnetic heating properties

Magnetite (Fe3O4) nanoparticles have been successfully synthesized using cetyltrimethylammonium bromide (CTAB). The stabilizing agent CTAB reduces agglomeration of magnetic nanoparticles in solution. The formation of Fe3O4 nanoparticles was confirmed by X-ray diffractometry, IR spectroscopy and Mössbauer spectroscopy. The average crystallite size of magnetite nanoparticles was found to be 14.41 nm. The catalytic activity of the obtained magnetite have been tested in a batch reactor. Due to favourable redox properties and low crystallite size, magnetite nanoparticles have high catalytic activity in the decomposition of H2O2. The degree of H2O2 decomposition was 77.41% in 120 min. The induction heating of synthesized Fe3O4 nanoparticles have been investigated. At magnetite concentration of 40 mg/ml, the specific absorption rate is equal 14.57 W/g.

Electro-hydrogenation of biomass-derived levulinic acid to γ-valerolactone via the magnetic heating of a Ru nanocatalyst

The thermal imbalance between the surface of the Ru catalyst and the bulk liquid medium due to magnetic heating of the catalyst improves the yield of gamma-valerolactone.

삼방향 양측구조 직렬코어 공진 유도가열 보일링 시스템에 관한 연구

본 논문은 보다 효율적인 보일링(Boiling) 가열시스템을 위하여 삼방향 양측구조를 적용하여 열 교환면적을 확대하고 신속가열 그리고 저 전력을 통해 열에너지 효율을 극대화시킬 수 있는 기법을 제안한다. 자성을 갖는 자성가열(Magnetic heating)면을 구성하여 열 교환면적을 확대하였고 유도코일(Induction coil)을 직렬코어방식으로 구성하여 열매체의 신속한 가열이 가능함은 물론, 공진(Resonant) 임피던스 대역을 매칭(Matching)기법을 이용하여 유도가열(Induction heating) 주파수를 증폭하므로 에너지절감이 가능한 저 전력으로 높은 열에너지 효율을 극대화 시킬 수 있는 방법을 제안하였다. 본 논문에서 제안된 유도가 열방법을 기존의 가열방법과 비교하여 제안한 가열방법의 우수성을 종합적 실험결과를 통하여 확인할 수 있었다. 제안된 방법의 정량적인 결과 도출을 위하여 보일러 시스템에 적용 구현하였으며 기본 방식은 전자기유도가열(Electromagnetic Induction Heating)방식을 사용하였다.

Carbothermal treated ferrite nanoparticles with improved magnetic heating efficiency and T1-MRI performance

Ferrite nanoparticle based T1-magnetic resonance imaging (T1-MRI) guided magnetic hyperthermia is a promising method for accurate tumor treatment. In previous studies, ultra-small sized ferrite nanoparticles were required to achieve excellent T1-MRI performance. However, an ultra-small size is usually accompanied by weak magnetization, resulting in a low magnetic heating efficiency, which is insufficient for magnetic hyperthermia. Therefore, ferrite nanoparticles with high magnetic heating efficiency and excellent T1-MRI performance capabilities are still highly desired. Here, oxygen vacancies are introduced in Mn0.6Zn0.4Al0.2Fe1.8O4 ferrite nanoparticles by applying carbothermal treatments. As oxygen vacancy concentrations increase, the intrinsic loss power increases up to 2.55 nH m2/kg, which is 33% higher than that of Fe3O4 nanoparticles used in magnetic hyperthermia. Specific absorption rate (SAR) calculations indicate that the predominant heat generation mechanism changes from hysteresis loss and relaxation loss to eddy current loss owing to conductivity enhancement by carbothermal treatments. The eddy current loss accounts for 70.6% of the total SAR, and plays a crucial role in increasing magnetic heating efficiency. In addition, Mn0.6Zn0.4Al0.2Fe1.8O4 ferrite nanoparticles with oxygen vacancies exhibit a significantly high r1 value of 9.69 mM−1 s−1 and a low r2/r1 ratio of 1.6 on a 3.0 T scanner. This is because oxygen vacancies naturally exhibit oxygen affinity in water molecules. The findings of this study could serve as a methodological reference of preparing ferrite nanoparticles for T1-MRI guided magnetic hyperthermia.

Structure-Property-Function Relationships of Iron Oxide Multicore Nanoflowers in Magnetic Hyperthermia and Photothermia.

Magnetite and maghemite multicore nanoflowers (NFs) synthesized using the modified polyol-mediated routes are to date among the most effective nanoheaters in magnetic hyperthermia (MHT). Recently, magnetite NFs have also shown high photothermal (PT) performances in the most desired second near-infrared (NIR-II) biological window, making them attractive in the field of nanoparticle-activated thermal therapies. However, what makes magnetic NFs efficient heating agents in both modalities still remains an open question. In this work, we investigate the role of many parameters of the polyol synthesis on the final NFs' size, shape, chemical composition, number of cores, and crystallinity. These nanofeatures are later correlated to the magnetic, optical, and electronic properties of the NFs as well as their collective macroscopic thermal properties in MHT and PT to find relationships between their structure, properties, and function. We evidence the critical role of iron(III) and heating ramps on the elaboration of well-defined NFs with a high number of multicores. While MHT efficiency is found to be proportional to the average number of magnetic cores within the assemblies, the optical responses of the NFs and their collective photothermal properties depend directly on the mean volume of the NFs (as supported by optical cross sections numerical simulations) and strongly on the structural disorder in the NFs, rather than the stoichiometry. The concentration of defects in the nanostructures, evaluated by photoluminescence and Urbach energy (EU), evidence a switch in the optical behavior for a limit value of EU = 0.4 eV where a discontinuous transition from high to poor PT efficiency is also observed.

Direct Probing of Fe3O4 Nanoparticle Surface Temperatures during Magnetic Heating: Implications for Induction Catalysis

The presence of a temperature gradient between the magnetic nanoparticle (NP) surface and the bulk medium during induction heating has been observed across several fields. While no noticeable increase in bulk temperature is observed, biological (DNA denaturation, tumor apoptosis) and chemical (bond cleavage) evidence indicates high temperatures near/at the NP surface. Unfortunately, current methods for temperature probing rely on bulk temperature measurements (fiber-optic IR probes) or are limited by thermal stability and spatial resolution (organic molecules). To further the understanding of magnetic heating as a driving force in catalysis, as well as drug delivery/hyperthermia treatments, a more accurate description of the nanoparticle surface temperature is needed. This work uses inorganic luminescent probes in direct contact with the particle surface, entailing the deposition of YVO4:Eu3+ around a Fe3O4|SiO2 structure, to measure the local temperature. The luminescent response is calibrated in situ via a controlled temperature stage to extract the field-dependent heating. The luminescent probe results in a high spatial resolution (<5.5 nm) with temperatures up to 64 °C higher than standard fiber-optic probes. The direct contact between the photoluminescence (PL) probe and Fe3O4 allows for ballistic transport and improved temporal resolution, mimicking an adiabatic system (negligible long-range heat dissipation). Other advantages include avoiding measurements in liquid media, where the distance between the heat source and the probe cannot be controlled, adding to the uncertainty of the temperature measurement due to changes in colloidal anisotropy (which changes with the heating profile) of the magnetic cores and surface quenching of the luminescent signal.

Bone Tumor Suppression in Rabbits by Hyperthermia below the Clinical Safety Limit Using Aligned Magnetic Bone Cement.

Demonstrating highly efficient alternating current (AC) magnetic field heating of nanoparticles in physiological environments under clinically safe field parameters has remained a great challenge, hindering clinical applications of magnetic hyperthermia. In this work, exceptionally high loss power of magnetic bone cement under the clinical safety limit of AC field parameters, incorporating direct current field-aligned soft magnetic Zn0.3 Fe2.7 O4 nanoparticles with low concentration, is reported. Under an AC field of 4 kA m-1 at 430kHz, the aligned bone cement with 0.2 wt% nanoparticles achieves a temperature increase of 30 °C in 180 s. This amounts to a specific loss power value of 327 W and an intrinsic loss power of 47 nHm2 kg-1 , which is enhanced by 50-fold compared to randomly oriented samples. The high-performance magnetic bone cement allows for the demonstration of effective hyperthermia suppression of tumor growth in the bone marrow cavity of New Zealand White Rabbits subjected to rapid cooling due to blood circulation, and significant enhancement of survival rate.

Carbothermal treated iron oxide nanoparticles with improving magnetic heating efficiency for hyperthermia

Iron oxide nanoparticles with high magnetic heating efficiency is highly desired for magnetic hyperthermia applications. In this paper, carbothermal treatments with graphene are used for improving the magnetic heating efficiency of iron oxide nanoparticles. With the increasing treatment temperature from 400 °C to 700 °C, the specific absorption rate (SAR) increases 2–7 folds. Oxygen vacancies resulted from carbon reduction process, along with the rapid grain growth (from 5.1 nm to 225.6 nm), improve eddy current loss. SAR calculations suggest that eddy current loss accounts up to 23.9%-78.5% of the total SAR after carbothermal treatments, which is the main factor for SAR improvements. This work may provide a methodological reference of preparing iron oxide nanoparticles for magnetic hyperthermia.