Morphology and Microstructure Evolution of Gold Nanostructures in the Limited Volume Porous Matrices

The modern development of nanotechnology requires the discovery of simple approaches that ensure the controlled formation of functional nanostructures with a predetermined morphology. One of the simplest approaches is the self-assembly of nanostructures. The widespread implementation of self-assembly is limited by the complexity of controlled processes in a large volume where, due to the temperature, ion concentration, and other thermodynamics factors, local changes in diffusion-limited processes may occur, leading to unexpected nanostructure growth. The easiest ways to control the diffusion-limited processes are spatial limitation and localized growth of nanostructures in a porous matrix. In this paper, we propose to apply the method of controlled self-assembly of gold nanostructures in a limited pore volume of a silicon oxide matrix with submicron pore sizes. A detailed study of achieved gold nanostructures' morphology, microstructure, and surface composition at different formation stages is carried out to understand the peculiarities of realized nanostructures. Based on the obtained results, a mechanism for the growth of gold nanostructures in a limited volume, which can be used for the controlled formation of nanostructures with a predetermined geometry and composition, has been proposed. The results observed in the present study can be useful for the design of plasmonic-active surfaces for surface-enhanced Raman spectroscopy-based detection of ultra-low concentration of different chemical or biological analytes, where the size of the localized gold nanostructures is comparable with the spot area of the focused laser beam

Recent Advances of Amorphous Wire CMOS IC Magneto-Impedance Sensors: Innovative High-Performance Micromagnetic Sensor Chip

We analyzed and organized the reasons why the amorphous wire CMOS IC magneto-impedance sensor (MI sensor) has rapidly been mass-produced as the electronic compass chips for the smart phones, mobile phones, and the wrist watches. Comprehensive advantageous features regarding six terms of (1) microsizing and ultralow power consumption, (2) high linearity without any hysteresis for the magnetic field detection, (3) high sensitivity for magnetic field detection with a Pico-Tesla resolution, (4) quick response for detection of magnetic field, (5) high temperature stability, and (6) high reversibility against large disturbance magnetic field shock are based on the magneto-impedance effect in the amorphous wires. We have detected the biomagnetic field using the Pico-Tesla resolution MI sensor at the room temperature such as the magneto-cardiogram (MCG), the magneto-encephalogram (MEG), and the self-oscillatory magnetic field of guinea-pig stomach smooth muscles (in vitro) that suggest the origin of the biomagnetic field is probably pulsive flow of Ca2+ through the muscle cell membrane

Zinc-Doped Gold/Cobalt Ferrite Nanoparticles in Studying the Cytotoxic Effect on T-Lymphoblastic Leukemia Cells

The rapid development of the nanomaterials’ application’s fields in biomedicine is associated with the expanded possibilities of combining their properties in composite materials. The use of nanocomposites allows application in various types of therapy or theranostics. In this work, we propose a new approach for the fabrication of a gold/ferrite nanocomposite, which consists of gold particles up to 10 nm in diameter surrounded by small nanoparticles of cobalt ferrite (~5 nm) doped with zinc. The gold core is coated with arginine, while the ferrite particles have dihydrocaffeic acid shell. The fabricated nanocomposite possesses optical and magnetic properties due to the excitation of localized plasmon resonance in gold particles and the superparamagnetic state of ferrite particles. The results of studying the structural, magnetic, and optical properties, as well as the cytotoxicity of the obtained nanocomposite, allow us to conclude that it can be used in combined photo- and magnetic hyperthermic therapy

Spatial Manipulation of Particles and Cells at Micro- and Nanoscale via Magnetic Forces

The importance of magnetic micro- and nanoparticles for applications in biomedical technology is widely recognised. Many of these applications, including tissue engineering, cell sorting, biosensors, drug delivery, and lab-on-chip devices, require remote manipulation of magnetic objects. High-gradient magnetic fields generated by micromagnets in the range of 103–105 T/m are sufficient for magnetic forces to overcome other forces caused by viscosity, gravity, and thermal fluctuations. In this paper, various magnetic systems capable of generating magnetic fields with required spatial gradients are analysed. Starting from simple systems of individual magnets and methods of field computation, more advanced magnetic microarrays obtained by lithography patterning of permanent magnets are introduced. More flexible field configurations can be formed with the use of soft magnetic materials magnetised by an external field, which allows control over both temporal and spatial field distributions. As an example, soft magnetic microwires are considered. A very attractive method of field generation is utilising tuneable domain configurations. In this review, we discuss the force requirements and constraints for different areas of application, emphasising the current challenges and how to overcome them

Stress Effects on Magnetic Properties of Amorphous Microwires Subjected to Current Annealing

Effects of current annealing on magnetic hysteresis properties and magnetoimpedance (MI) of glass-coated amorphous microwires with nominal composition of Co71Fe5B11Si10Cr3 and small positive magnetostriction were investigated with the purpose to control the magnetic anisotropy. We have demonstrated that current annealing can produce a controllable change in the easy anisotropy direction from almost axial to circular, depending on the annealing time. The induced magnetization configuration is very sensitive to the applied tensile stress. The combination of positive magnetostriction and helical anisotropy makes it possible to realise large stress-magnetoimpedance (S-MI) effect without use of any dc bias fields owing to the directional change in magnetization. This is especially important for microwave frequency S-MI effect and can be very interesting for developing stress-sensors operating at the high frequency region

Gold/cobalt ferrite nanocomposite as a potential agent for photothermal therapy

The study encompasses an investigationof optical, photothermal and biocom-patibility properties of a composite con-sisting of golden cores surrounded bysuperparamagnetic CoFe 2 O 4 nanoparti-cles. Accompanied with the experiment,the computational modeling reveals that each adjusted magnetic nanoparticleredshifts the plasmon resonance frequency in gold and nonlinearly increases theextinction cross-section at 800 nm. The concentration dependent photothermalstudy demonstrates a temperature increase of 8.2 K and the photothermal con-version efficiency of 51% for the 100 μg/mL aqueous solution of the compositenanoparticles, when subjected to a laser power of 0.5 W at 815 nm. During anin vitro photothermal therapy, a portion of the composite nanoparticles, initiallyseeded at this concentration, remained associated with the cells after washing.These retained nanoparticles effectively heated the cell culture medium, result-ing in a 22% reduction in cell viability after 15 min of the treatment. The com-posite features a potential in multimodal magneto-plasmonic therapies