Nanoparticles Metalis Review

18

 WILEY-VCH-Verlag GmbH, D-69451 Weinheim, 2000

1439-4235/00/01/01 $ 17.50+.50/0

CHEMPHYSCHEM 2000, 1, 18 ± 52

Nanoparticle Arrays on Surfaces for Electronic, Optical, and Sensor Applications**
Andrew N. Shipway,[a] Eugenii Katz,[a] and Itamar Willner*[a]
Particles in the nanometer size range are attracting increasing attention with the growth of interest in nanotechnologicaldisciplines. Nanoparticles display fascinating electronic and optical properties as a consequence of their dimensions and they may be easily synthesized from a wide range of materials. The dimensions of these particles makes them ideal candidates for the nanoengineering of surfaces and the fabrication of functional nanostructures. In the last five years, much effort has been expended on theirorganization on surfaces for the construction of functional interfaces. In this review, we address the research that has led to numerous sensing, electronic, optoelectronic, and photoelectronic interfaces, and also take time to cover the synthesis and characterization of nanoparticles and nanoparticle arrays. KEYWORDS: colloids ´ interfaces ´ monolayers ´ nanostructures ´ sensors

1. IntroductionThe emerging disciplines of nanoengineering,[1] nanoelectronics,[2] and nanobioelectronics[3] require suitably sized and functional building blocks with which to construct their architectures and devices. This need has encouraged the development of supramolecular,[4] biomolecular,[5] and dendrimer[6] chemistries for engineering substatnces of Šngström and nanoscale dimensions but, even withlithographic techniques now reaching the 100 nm range, the intermediate scale of 10 ± 100 nm remains relatively unexploited (Figure 1). The world of colloid and cluster science[7] has risen to this challenge and is beginning to find ways to organize nanometer-sized particles on the micron and submicron scale. Although many of these particles have been known for a substantial time, it is only now thatthe tools for their engineering and characterization exist, which open the doors to new disciplines of nanoparticle and nanocrystal devices. Nanoparticles are not just convenient structural elements however, but can also display unique functions. They can be fashioned from many materials and have a wide functional diversity very different from bulk materials, with much of their electronic,[8, 9]optical,[7, 10±13] and catalytic[14] properties originating from their quantum-scale dimensions.[15] In order to tailor the new generation of nanodevices and ªsmartº materials, ways to organize the nanoparticles into controlled architectures must be found. This conundrum has been addressed to some extent by a large body of recent work describing the construction of colloidal dyads and triads,[16,17] ªstringsº,[18] clusters,[19] and other architectures[19±22] in solution and at liquid ± liquid interfaces. These constructions will not be described in any detail here, since this review is dedicated to surface-bound nanostructures. Likewise, we will not explore the highly active research area of single-nanoparticle electronics in great depth, as excellent reviews already exist.[12, 15, 20]These single-electron devices tap into the quantum properties of nanoparticles for the fabrication of single-electron transistors[23, 24] and similar devices[25±27] from isolated, immobilized nanoparticles. Here, we will focus on efforts to construct organized nanoparticle arrays which perform tangible functions. These superstructures are formed on various solid supports by specific adsorption orself-assembly techniques. Although work on spin-coated, evaporated, or nonspecifically adsorbed nanoparticle films has yielded noteworthy results,[28] these techniques are conceptually macroscopic rather than nanoscopic and so will not be covered here. The relevance of nanoparticle superstructures to the emerging areas of nanotechnology and nanophotoelectrochemistry, and to the development of...