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To overcome the negative contrast limitations, and to improve the sensitivity of the magnetic resonance signals, the mesoporous silica coated Fe/Mn multilayered nanowires (NWs) were used as a T 1 -T 2 dual-mode contrast agents (CAs). The single component Fe and Mn NWs, and Fe/Mn multilayer NWs were synthesized by electrodeposition in the homemade anodic aluminum oxide (AAO) templates with the aperture of about 30 nm. The structural characterization and morphology of single component and multisegmented NWs was done by X-ray diffraction and transmission electron microscopy. The elemental composition of Fe/Mn multilayerd NWs was confirmed by energy-dispersive X-ray and energy-dispersive spectrometer. Vibrating sample magnetometer was used to test the magnetic properties, and 1.5 T magnetic resonance imaging (MRI) scanner was used to measure the relaxation efficiency. Importantly, the MRI study indicated that the Fe/Mn multilayer NWs showed a significant T 1 -T 2 imaging effect, and have longitudinal relaxivity (r 1 ) value, that is, 1.25 ± 0.0329 × 10 -4 μM -1 s -1 and transverse relaxivity (r 2 ), that is, 5.13 ± 0.123 × 10 -4 μM -1 s -1 , which was two times of r 1 value (0.654 ± 0.00899 × 10 -4 μM -1 s -1 ) of Mn NWs, and r 2 value (2.96 ± 0.0415 × 10 -4 μM -1 s -1 ) of Fe NWs. Hence, Fe/Mn multilayer NWs have potential to be used as T 1 -T 2 dual-mode CAs., (© 2020 Wiley Periodicals LLC.)

Magnetic nanostructures and nanomaterials play essential roles in modern bio medicine and technology. Proper surface functionalization of nanoparticles (NPs) allows the selective bonding thus application of magnetic forces to a vast range of cellular structures and biomolecules. However, the spherical geometry of NPs poises a series of limitations in various potential applications. Mostly, typical spherical core shell structure consists of magnetic and non-magnetic layers have little tunability in terms of magnetic responses, and their single surface functionality also limits chemical activity and selectivity. In comparison to spherical NPs, nanowires (NWs) possess more degrees of freedom in achieving magnetic and surface chemical tenability. In addition to adjustment of magnetic anisotropy and inter-layer interactions, another important feature of NWs is their ability to combine different components along their length, which can result in diverse bio-magnetic applications. Magnetic NWs have become the candidate material for biomedical applications owing to their high magnetization, cheapness and cost effective synthesis. With large magnetic moment, anisotropy, biocompatibility and low toxicity, magnetic NWs have been recently used in living cell manipulation, magnetic cell separation and magnetic hyperthermia. In this review, the basic concepts of magnetic characteristics of nanoscale objects and the influences of aspect ratio, composition and diameter on magnetic properties of NWs are addressed. Some underpinning physical principles of magnetic hyperthermia (MH), magnetic resonance imaging (MRI) and magnetic separation (MS) have been discussed. Finally, recent studies on magnetic NWs for the applications in MH, MRI and MS were discussed in detail.

Porous polyethylene glycol terephthalate (PET) film is a kind of mesopore structure template with pore size ranging from nanometer to micrometer by chemical etching after irradiation of heavy ions. The etching rate is an important factor affecting the pore morphology and quality of the membrane. In this paper, four stacked PET film were irradiated with 140 MeV 32S ions at room temperature and vacuum. During chemical etching of irradiated samples, the path etching rate Vt was determined by conduction method, and the bulk etching rate Vb was determined by weighing method. The relationship between etching temperature, concentration, sensitization time, and etching rate was studied. The results show that the etching rate is exponentially correlated with the etching temperature, and increases linearly with the increase of the etching solution concentration. When the concentration of NaOH is 3 mol·L−1 and the etching temperature is 75°C, the formation of cylindrical micropores is the most favorable. The pore size of porous PET film can be adjusted, and the relationship between pore size and etching time is dnm=15nm+0.24t. This is of great significance for the preparation of nanowires with uniform size and stable properties. Highlights: We have obtained the optimal conditions for obtaining cylindrical holes.The relationship between the diameter of holes and etching time were determined. [ABSTRACT FROM AUTHOR]

To overcome the negative contrast limitations, and to improve the sensitivity of the magnetic resonance signals, the mesoporous silica coated Fe/Mn multilayered nanowires (NWs) were used as a T1–T2 dual‐mode contrast agents (CAs). The single component Fe and Mn NWs, and Fe/Mn multilayer NWs were synthesized by electrodeposition in the homemade anodic aluminum oxide (AAO) templates with the aperture of about 30 nm. The structural characterization and morphology of single component and multisegmented NWs was done by X‐ray diffraction and transmission electron microscopy. The elemental composition of Fe/Mn multilayerd NWs was confirmed by energy‐dispersive X‐ray and energy‐dispersive spectrometer. Vibrating sample magnetometer was used to test the magnetic properties, and 1.5 T magnetic resonance imaging (MRI) scanner was used to measure the relaxation efficiency. Importantly, the MRI study indicated that the Fe/Mn multilayer NWs showed a significant T1–T2 imaging effect, and have longitudinal relaxivity (r1) value, that is, 1.25 ± 0.0329 × 10−4 μM−1 s−1 and transverse relaxivity (r2), that is, 5.13 ± 0.123 × 10−4 μM−1 s−1, which was two times of r1 value (0.654 ± 0.00899 × 10−4 μM−1 s−1) of Mn NWs, and r2 value (2.96 ± 0.0415 × 10−4 μM−1 s−1) of Fe NWs. Hence, Fe/Mn multilayer NWs have potential to be used as T1–T2 dual‐mode CAs. [ABSTRACT FROM AUTHOR]

A lot of nanomaterials are using T1-T2 dual mode magnetic resonance (MR) contrast agents (CAs), but multilayer nanowire (NW) with iron (Fe) and manganese (Mn) as T1-T2 dual modal CAs has not been reported yet. Herein, we synthesized a Fe/Mn multilayer NW with an adjustable Fe layer, as T1-T2 dual-mode CAs. The relaxation performance of Fe/Mn multilayer NW was studied at 1.5 T. Results show that, when the length of the Fe layer is about 10 nm and the Mn is about 5 nm, the r1 value (21.8 mM−1s−1) and r2 value (74.8 mM−1s−1) of the Fe/Mn multilayer NW are higher than that of Mn NW (3.7 mM−1s−1) and Fe NW (59.3 mM−1s−1), respectively. We predict that our Fe/Mn multilayer NW could be used as T1-T2 dual mode MRI CAs in the near future. [ABSTRACT FROM AUTHOR]

In the last couple of decades, there has been a lot of progress in the synthesis methods of nano-structural materials, but still the field has a large number of puzzles to solve. Metal nanowires (NWs) and their alloys represent a sub category of the 1-D nano-materials and there is a large effort to study the microstructural, physical and chemical properties to use them for further industrial applications. Due to technical limitations of single component NWs, the hetero-structured materials gained attention recently. Among them, multi-segmented NWs are more diverse in applications, consisting of two or more segments that can perform multiple function at a time, which confer their unique properties. Recent advancement in characterization techniques has opened up new opportunities for understanding the physical properties of multi-segmented structures of 1-D nanomaterials. Since the multi-segmented NWs needs a reliable response from an external filed, numerous studies have been done on the synthesis of multi-segmented NWs to precisely control the physical properties of multi-segmented NWs. This paper highlights the electrochemical synthesis and physical properties of multi-segmented NWs, with a focus on the mechanical and magnetic properties by explaining the shape, microstructure, and composition of NWs. [ABSTRACT FROM AUTHOR]