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Mono-and multilayers of cadmium sulfide (CdS) nanoparticles were fabricated on a gold substrate covered with alkanedithiol self-assembled monolayers (SAMs) by an alternate immersion of the substrate into ethanolic solutions of dithiol, i.e., 1,6-hexanedithiol or 1,10-decanedithiol, and dispersion of CdS nanoparticles (ca. 3 nm in diameter), the latter of which was prepared in sodium bis(2-ethylhexyl)sulfosuccinate (Aerosol OT, AOT)/H 2 O/heptane reversed micelles. A layer-by-layer structure of dithiol SAM and CdS monolayer was confirmed with Fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy (XPS) at each step of composite-film preparation. It was revealed that CdS nanoparticles on SAMs were surrounded by AOT, which was then substituted by dithiols when the film was treated with the dithiol solution. The amount of CdS nanoparticles on the sample was measured by inductively coupled plasma mass spectrometry (ICP-MS) to be consistent with the above-mentioned monolayer structure. The photoinduced anodic current was observed when the composite film was immersed in an electrolyte solution containing triethanolamine as an electron donor. An action spectrum, which was quite similar to the absorption spectrum of CdS dispersion, indicates that the CdS nanoparticle keeps its size without mutual aggregation, and semiconducting properties even after being immobilized on the substrate.

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Magnetic nanoparticles have been attracting much interest as a labeling material in the fields of advanced biological and medical applications such as drug delivery, magnetic resonance imaging, and array-based assaying. In this review, synthesis of iron oxide magnetic nanoparticles via a reverse micelle system and modification of their surface by an organosilane agent are discussed. Furthermore, as a practical biological assay system, the magnetic detection of biomolecular interactions is demonstrated by using the combination of a patterned substrate modified with a self-assembled monolayer and the magnetic nanoparticles.