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Magnetoresistive biosensors use a new detection method for molecular recognition reactions based on two recently developed techniques and devices: Magnetic markers and XMR sensors, where XMR means either giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR). The markers are specifically attached to the target molecules, and their magnetic stray field is picked up by an embedded magnetoresistive sensor as a change of the electrical resistance. Compared to established, e.g., fluorescent, detection methods, magnetic biosensors have a number of advantages, including low molecular detection limits, flexibility, and the direct availability of an electronic signal suitable for further automated analysis. This makes them a promising choice for the detection units of future widespread and easy-to-use lab-on-a-chip systems or biochips. In this article, we discuss recent advances in this field and compare possible approaches toward single molecule detection.

Novel amphiphilic trithiolates possess excellent properties for gold nanoparticle (AuNP) stabilization and functionalization and cannot be replaced by exchange reactions.

Co nanocrystals have been prepared via two different chemical preparation routes. Microstructural characterization has been carried out by conventional and high-resolution transmission electron microscopy. Magnetic characterization reveals that Co nanocrystals with mean particle size distributions about 6 nm are ferromagnetic at room temperature. Superlattices of about 1 m 1 m can be reproduced. For the second preparation route the formation of an -Co phase was detected by X-ray diffraction. Whereas the pure Co nanocrystals form domains with a mixture of simple cubic and hexagonal packing, FeCo alloyed nanoparticles form long chain-like structures.