From Magnetic Nanoparticles to Magnetoresistive Biosensors

Abstract

This paper highlights recent advances in synthesis and magnetotransport properties of magnetic Co nanoparticles. It is shown that magnetic Co nanoparticles self-assembled in nanoparticular monolayers revealing giant magnetoresistance similar to granular systems but with additional features resulting from dipolar interactions between small domains of nanoparticles. A spin-valve with one magnetic Co nanoparticular electrode is employed as a model to demonstrate that individual magnetic moments of Co nanoparticles can be coupled to a magnetic Co layer which in turn oers tailoring of the resulting giant magnetoresistance characteristics. In addition, it is demonstrated that combining a magnetic on-o ratchet with magnetic tunneling junctions integrated in the ratchet introduces a new biosensor concept enabling: (1) simultaneous transporting and separating biomolecules, (2) dynamical biomolecule detection when passing magnetic tunneling junctions in a 1D arrangement. It is projected that this biosensor concept could be applied for viruses as well as for bacteria.

Perspective: Magnetoresistive sensors for biomedicine

“…For more than a decade, several research groups worldwide are focusing on the design and development of MR biosensing platforms for biomolecular recognition as well as detection and quantification of biological entities. [69][70][71][72][73][74][75][76] These applications are based on the giant magnetoresistance (GMR) [GMR multilayers and spin valves (SVs)] and the tunneling magnetoresistance (TMR) effects.…”

“…There, the electrons tunnel across the insulating barrier as a result of a spin dependent tunneling probability that causes an electron flow perpendicular to the plane (CPP). 65,67,71,72 An MTJ can operate as a switch between a low state and a high state of electrical resistance as explained in Ref. 61.…”

Giant Magnetoresistance: Basic Concepts, Microstructure, Magnetic Interactions and Applications

“…It also occurs in pure particular systems (see next section) and hybrid materials containing thin films as well as magnetic clusters. These hybrid structures can be prepared e.g., by heating of films or by preparing multilayers with ultrathin and therefore discontinuous magnetic layers [ 106 , 107 , 108 , 109 , 110 ]. Holody et al showed that Co/Py hybrid systems reveal advantages for sensor applications like a lateral decoupling in the cluster layer in combination with a low coercive field [ 106 ].…”

Diagnose Pathogens in Drinking Water via Magnetic Surface-Enhanced Raman Scattering (SERS) Assay

“…Magnetic nanoparticles (MNPs) have been widely applied in biological science for its affinity to biological molecules (Huang et al, 2010), such as bioenergy recovery (Lin et al, 2015), drug delivery (Sun et al, 2008) and drinking water purification (Xu et al, 2014). In environmental science, most relative research has addressed the magnetisms improvement (Ennen et al, 2012;Ozdemir et al, 2012) or surface modification to enhance bacteria capturing efficiency (Luis Corchero & Villaverde, 2009). There is limited work on how to use MNPs as a diagnosis tool in quantifying pathogens in drinking water.…”