Single physical aperture

Figure 1.7 Dual confocal aperturing achieved with a single physical aperture. Reproduced from Infrared Fourier Transform Spectrometry by P. R. Griffiths and ). A. de Haseth 2007, p. 307.

Figure 1.6 Dual confbcal aperturing achieved with a single physical aperture. (Reproduced from Ref. [10]. Copyright 2007, John Wiley Sons.)...

Up to now, a large part of the international scientific attention was devoted to the study of metallic nanoparticles (either single particles or in a colloid ensemble) (3, 14). Milling nanometric apertures in a metallic film is an intuitive way to manufacture new nanophotonics devices that are robust and highly reproducible. Although this concept appears very simple, such apertures exhibit attractive physical properties, such as localization of excitation light, strong isolation fi om emission produced by unbound species, and an increase in apparent absorption and emission yield. The simplicity of the structures and their ease of use should further expand their application towards the real-time detection and identification of a small number of molecules. 

In order to understand the physical phenomena behind nanoaperture-enhanced fluorescence, investigating an isolated nanoaperture is of major interest, which eliminates any effects of aperture coupling. Further, data from a single molecule may reveal information hidden by ensemble measurements, such as variances in kinetic rates, memory effects, or transient states (52). 

One further problem is the physical size of the food sample. Some specimens may simply be too small to measure successfully as single items, though recently instruments with very small aperture viewing heads which permit measnrements on areas of around 3 mm diameter are available. It is, however, more nsnal to bnlk such samples and then employ large area sample cups and large diameter instmment apertures when making the measnrements. 

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