ABSTRACT

Although nanometer-sized particles can be observed with an electron microscope, special environmental conditions are required for this method to work. Electron microscopes operate

only when samples are placed in vacuum. is puts severe limitations on biological and other applications. e main information obtained with electron microscopy is electron density in the sample and complementary methods are required for obtaining other characteristics. Some imaging techniques, such as nuclear magnetic resonance imaging (NMRI), are a long way from being capable to image even 1 μm particles not to mention single molecules. e resolution of an atomic force microscope substantially degrades when imaging through so tissues like cell membranes (de Jager and van Noort 2007). It turns out that optics and optical microscopy provide probably the most universal approach to the detection of nanoparticles under ambient conditions or embedded deeply into a transparent material. Moreover, it is quite common that optical properties of nanoparticles are of direct interest. In this chapter, particles of essentially sub-wavelength size will be of interest. Because the visible (optical) spectrum covers a range of wavelengths approximately between 400 and 750 nm, such particles should be smaller than 100 nm across. e attention will be mostly on the fundamental principles of optical detection.