Synthesis of Mn Fe_2O_4/cellulose aerogel nanocomposite with strong magnetic responsiveness

Cellulose aerogel, with abundant three-dimensional architecture, has been considered as a class of ideal eco-friendly matrix materials to encapsulate various nanoparticles for synthesis of miscellaneous functional materials. In the present paper, hexagonal single-crystalline MnFe_2O_4 was fabricated and inserted into the cellulose aerogel using an in situ chemical precipitation method. The as-prepared MnFe_2O_4 nanoparticles were well dispersed and immobilized in the micro/nanoscale pore structure of the aerogel, and exhibited superparamagnetic behavior. In addition, the nanocomposite was easily actuated under the effect of an external magnetic field, revealing its strong magnetic responsiveness.Combined with the advantages of environmental benefits,facile synthesis method, strong magnetic responsiveness,and unique structural feature, this class of MnFe_2O_4/cellulose aerogel nanocomposite has possible uses for applications such as magnetically actuated adsorbents.

Control of light scattering by nanoparticles with optically-induced magnetic responses

Conventional approaches to control and shape the scattering pattems of light generated by different nanostructures are mostly based on engineering of their electric response due to the fact that most metallic nanostructures support only electric resonances in the optical frequency range. Recently, fuelled by the fast development in the fields of metamaterials and plasmonics, artificial optically-induced magnetic responses have been demonstrated for various nanostructures. This kind of response can be employed to provide an extra degree of freedom for the efficient control and shaping of the scattering patterns of nanoparticles and nanoantennas. Here we review the recent progress in this research direction of nanoparticle scattering shaping and control through the interference of both electric and optically-induced magnetic responses. We discuss the magnetic resonances supported by various structures in different spectral regimes, and then summarize the original results on the scattering shaping involving both electric and magnetic responses, based on the interference of both spectrally separated （with different resonant wavelengths） and overlapped dipoles （with the same resonant wavelength）, and also other higher-order modes. Finally, we discuss the scattering control utilizing Fano resonances associated with the magnetic responses.

Study on Magnetic Responsibility of Rare Earth Ferrite/Polyacrylamide Magnetic Microsphere

In inverse microemulsion, rare earth ferrite/polyacrylamide magnetic microsphere were prepared and their magnetic responsibility were studied by magnetic balance. Results indicate that the magnetic responsibility of microsphere relates to magnetic moment of rare earth ion, and it can be improved by the addition of dysprosium ion of high magnetic moment. Dysprosium content has an effect on magnetic responsibility of dysprosium ferrite/polyacrylamide magnetic microsphere. The microsphere displays strong magnetic responsibility when the molar ratio of Dy3+/iron is 0.20.

A shape-reconfigurable,light and magnetic dual-responsive shape-memory micropillar array chip for droplet manipulation

Droplet manipulation on an open surface has great potential in chemical analysis and biomedicine engineering.However,most of the reported platforms designed for the manipulation of water droplets cannot thoroughly solve the problem of droplet evaporation.Herein,we report a shape-reconfigurable micropillar array chip for the manipulation of water droplets,oil droplets and water-in-oil droplets.Water-in-oil droplets provide an enclosed space for water droplets,preventing the evaporation in an open environment.Perfluoropolyether coated on the surface of the chip effectively reduces the droplet movement resistance.The micropillar array chip has light and magnetic dual-response due to the Fe3O4 nanoparticles and the reduced iron powder mixed in the shape-memory polymer.The micropillars irradiated by a near-infrared laser bend under the magnetic force,while the unirradiated micropillars still keep their original shape.In the absence of a magnetic field,when the micropillars in a temporary shape are irradiated by the near-infrared laser to the transition temperature,the micropillars return to their initial shape.In this process,the surface morphology gradient caused by the deformation of the micropillars and the surface tension gradient caused by the temperature change jointly produce the driving force of droplet movement.

Uncovering the magnetic response of open-shell graphene nanostructures on metallic surfaces at different doping levels

Open-shell graphene nanostructures(GNs)are promising candidates for future spintronics and quantum technologies.Recent progress based on on-surface synthetic approach has successfully created such GNs on metallic surfaces.Meanwhile,the doping effect of metallic surfaces is inevitably present and can significantly tune their electronic and magnetic properties.Here,we investigate the zigzag end states of open-shell 7-armchair graphene nanoribbons(7-AGNRs)on Au(111),Au(100)and Ag(111)surfaces.Combined with the manipulation of a scanning tunneling microscope,we demonstrate that the end states can be tuned from empty states to singly occupied states and to doubly occupied states by substrate doping.Furthermore,the singly occupied states can be finely tuned,with the occupancy number of the states and related magnetic behaviors uncovered by experiments at different temperatures and magnetic fields.Our results provide a comprehensive study of the magnetic response of open-shell GNs on metallic surfaces at different doping levels.

Observations on a magnetotactic bacteria-grazing ciliate in sediment from the intertidal zone of Huiquan Bay,China

Magnetotactic bacteria(MTB)are a group of prokaryotes having the ability to orient and swim along geomagnetic field lines because they contain intracellular magnetosomes that are synthesized through a biomineralization process.Magnetosomes have recently also been found in unicellular eukaryotes,which are referred to as magnetically responsive protists(MRPs).The magnetosomes have three origins in MRPs.In this study,we characterized a MTB-grazing ciliated MRP that was magnetically collected from intertidal sediment of Huiquan Bay,Qingdao,China.Based on 18S rRNA gene sequence analysis,the ciliated MRP was tentatively identified as Uronemella parafi lificum HQ.Using transmission electron microscopy,we observed that magnetosomes having 2-3 shapes were randomly distributed within this ciliate.Energydispersive X-ray spectroscopy and high-resolution transmission electron microscopy images of the magnetosomes were consistent with them being composed of magnetite.Magnetosomes having the same shape and mineral composition were also detected in MTB that occurred in the same environment as the ciliated MRP.Statistical analysis showed that the size and shape of the magnetosomes in the ciliated MRP were similar to those in MTB.The results suggest that this ciliated MRP can graze,ingest,and digest various types of MTB.It is certainly worth noting that this is the first record of MRPs in Asian aquatic sediment and suggesting they might be widely distributed.These results also support the assertion that MRPs probably contribute to the ecological cycles of iron,and expand possibilities for research into the mechanism of magnetoreception in eukaryotes.

Experimental Study on Split-Ring Resonators with Different Slit Widths

Metamaterial one-dimensional periodic structures are composed of split-ring resonators, which can display electric permittivity and magnetic permeability simultaneously negative, are studied experimentally. In the present study, each resonator is made up of two concentric circular copper rings patterned on a substrate of kapton, with slits diametrically opposite each other and with the line of the splits along the longitudinal direction of the periodic array containing seven split rings evenly spaced. The experiments consist in inserting the metamaterial slab into a square waveguide of side length 6 mm, corresponding to a cutoff frequency of 25 GHz. Transmission bands due to magnetic and electrical responses are identified for slits with aperture widths of 1 mm and 2 mm, centered at 5.67 and 6.12 GHz frequencies, respectively, values well below the 25 GHz frequency cutoff, so characterizing a medium with negative permeability and permittivity.

Dynamic torque response analysis of IPMSM in flux weakening region for HEV applications

An over-modulation based vector control strategy for interior permanent magnet synchronous machine（ IPMSM） is proposed and investigated. The strategy increases the reference flux weakening voltage to improve efficiency in flux weakening region of IPMSMwith the same dynamic torque response performance in standard SV Mtechnique. The relationship between dynamic torque performance and the reference flux weakening voltage is also discussed. In order to achieve fast and smooth shift process,the torque response must be less than 20 ms in the parallel hybrid electric vehicle（ HEV）,according to this,modeling and experimental studies were carried out. The results show that the proposed strategy can achieve the same dynamic and steady state torque performance with higher reference flux weakening voltage,which means higher efficiency.

Magnetic responsive polymer nanofiber composites for easy collecting chemical spills

We describe a simple method to prepare magnetic responsive polydivinylbenzene(PDVB)nanofiber composites by precipitated cationic living polymerization in the present of oleic acid capped Fe3O4 nanoparticles(NPs).The Fe3O4 NPs are encapsulated with the PDVB forming dendrites,from which thin nanofibers are grown in the tip-growth mode.The thin nanofibers are interwoven with the thick nanofibers forming robust composite network.The composites are magnetic responsive and highly efficient to gel almost all chemicals.Separation of the gelled chemicals from water becomes easier with a magnet.The performance is promising for magnetic collection of chemical spills.

Nonlocal response of electric and magnetic modes in a silver cuboid dimer

The nonlocal effect on the spontaneous emission of a silver cuboid dimer is investigated using a local analog model. Magnetic as well as electric dipole excitations are introduced to excite different gap modes. The nonlocal response of electric and magnetic modes on various parameters of gap （width and refractive index） are investigated. Unidirectional radiation is achieved by the interaction between electric and magnetic modes in both local and nonlocal models. Compared to local simulations, the resonant wavelength is blue shifted and the spontaneous emission enhancement is weakened in the nonlocal model. The relative shifts of the resonant wavelengths get larger in smaller gaps with a higher refractive index.

Synthesis of novel magneto-hybrid polyoxometalate composite membrane with simultaneous photocatalytic self-cleaning and antifouling functionalities

Membrane technology is ideal for removing aqueous humic acid,but humic acid deposits cause membrane fouling,a significant challenge that limits its application.Herein,this work proposed an alternative approach to the controllably magnetically induced magnetohybrid polyoxometalate(magneto-HPOM)nanocomposite migration toward the polyethersulfone(PES)membrane surface under a magnetic field to enhance the self-cleaning and antifouling functionalities of the membrane.Before incorporating magneto-HPOM nanocomposite into the PES casting solution,functionalized magnetite nanoparticles(F-MNP)were first coated with HPOM photocatalyst to fabricate a magneto-HPOM-PES membrane.It was shown that the apparent impacts of this novel magneto-HPOM-PES membrane on the hydrophilic behavior and photocatalytic properties of the magneto-HPOM nanocomposite improve the hydrophilicity,separation performance,antifouling and self-cleaning properties of the membrane compared with neat PES membrane.Furthermore,after exposure to ultraviolet light,the magneto-HPOM-PES membrane can be recovered after three cycles with a flux recovery ratio of 107.95%,100.06%,and 95.56%,which is attributed to the temporal super hydrophilicity effect.Meanwhile,the magneto-HPOM-PES membrane could efficiently maintain 100%humic acid rejection for the first and second cycles and 99.81%for the third cycle.This study revealed a novel approach to fabricating membranes with high antifouling and self-cleaning properties for water treatment.

Versatile nanocomposite augments high-intensity focused ultrasound for high-efficacy sonodynamic therapy of glioma

High-intensity focused ultrasound(HIFU),with inherent advantages of improved ultrasonic depth and low off-target damage,holds the promising capability for glioma treatment,but the relatively long therapeutic time and potential physical complications may hamper its clinical application.Herein,a bovine serum albumin(BSA)-based nanoplatform with in situ growth of MnO_(2) was synthesized,and Protoporphyrin IX(PpIX)was further anchored to obtain a versatile PpIX@MnO_(2)@BSA nanoplatform(denoted as BMP).By employing HIFU as the exogenous irradiation source,a high-efficacy sonodynamic therapy(SDT)is developed,in which the excited BMP enables the production of tumoricidal reactive oxygen species(ROS).The inherent tumor microenvironment(TME)-responsive property of MnO_(2) endows BMP with specific T1-weighted magnetic resonance imaging(MRI)by releasing Mn2+,and the simultaneously generated O_(2) facilitates hypoxia alleviation as well as ^(1)O_(2) generation.Compared with HIFU therapy alone,suppression of glioma growth and improved survival benefits are achieved through the designed TMEresponsive nanocomposite under HIFU exposure.The high-efficacy SDT strategy combining BMP and HIFU demonstrated favorable TME-responsive T1-weighted MRI,hypoxic environment alleviation,and anti-tumor capability,providing a perspective paradigm for MRI-guided glioma treatment.

Dipole-fiber system： from single photon source to metadevices

Radiation of an electric dipole（quantum emitter）in vicinity of optical structures still attracts great interest due to emerging of novel application and technological advances.Here we review our recent work on guided and radiation modes of electric dipole and optical fiber system and its applications from single photon source to metadevices.We demonstrate that the relative position and orientation of the dipole and the core diameter of the optical fiber are the two key defining factors of the coupled system application.We demonstrate that such a coupled system has a vast span of applications in nanophotonics;a single photon source,a high-quality factor sensor and the building block of metadevices.

Recent progress on smart hydrogels for biomedicine and bioelectronics

The increasing development of biomedicine and bioelectronics has highlighted the requirement for smart materials that can respond to changes in physical and chemical properties under external environments,such as magnetic fields,electric fields,and temperature.Accordingly,hydrogels have been widely evaluated as promising candidates for smart materials owing to their intriguing structures comprising a cross‐linked network of polymer chains with interstitial spaces filled with solvent water.This feature endows hydrogels with soft and wet characteristics,which not only induce high tissue affinity but also allow the introduction of environmentally responsive nanoparticles to release specific smart properties.Herein,we reviewed novel smart hydrogels that can be applied in biomedicine and bioelectronics,and highlighted and discussed existing challenges in current technologies and research.