Surface sensing

Here we will discuss in more detail the 10 Mach-Zehnder interferometer7. It is a nice vehicle for illustrating in what way the problem of looking for extremely high resolutions can be approached, an approach which appeared to be very successful. We will focus on the MZI used for bulk sensing and we will make some additional remarks on its utilization in surface sensing. 

Notice, that with these extremely good resolutions in case of surface sensing contamination of the sensitive layer with solid particles has to be avoided completely, e.g. by an appropriate filtering of the sample solutions. Notice also that the temperature coefficient of the refractive index of water is about 10-4 per °C. So if applying the surface sensing mode using watery solutions indeed a perfect balance of both branches and low temperature gradients have to be aimed at. 

Fig. 8.10 Inverse of the detection factors are plotted as a function of W and Rc using (a) homogeneous and (b) surface sensing. The minimal P occurs at larger W and Rc in both figures. Reprinted from Ref. 45 with permission. 2008 Institute of Electrical and Electronics Engineers...

Fig. 8.20 Experimental sequence of surface sensing (a) The sensor surfaces are functionalized with biotinylated BSA (b) Streptavidin is specifically bound to the sensor surface with the biotin moiety (c) Biotin is captured on the sensor surfaces by the streptavidin...

In surface sensing, the adsorbed biomolecules onto the inner wall of a microtube will change the wave vector of a supported mode from A 0 to k and the electric field from E0 to ). These unperturbed (L0) and perturbed (E ) electric fields still satisfied wave equation ... 

Fig. 8.34 Surface sensing sensitivity of different radial order modes are simulated by using the perturbation method with the same azimuthal number m 700.The adsorbed polymer layer is assumed to have a refractive index of 1.46...

Using the same definition in Table 8.1, the sensitivity in surface sensing can be then expressed as... 

Surface Sensing Experiment Detection of Lipid Membrane and Membrane Proteins... 

Fig. 13.22 (a) MNF/microsphere tool for surface sensing, (b) Transmission power dependence on the position of the microsphere at the diffraction grating surface. Comparison of two measure ments of the same grating region shows the reproducibility of measurements. Reprinted from Ref. 42 with permission. 2008 Optical Society of America... 

In Section HI, we discussed the combination of near-field microscopy and third-order nonlinear spectroscopic technique, CARS. Since near-field microscopy is a surface sensing technique, even-order nonlinear processes, which require... 

Metal-based receptors which are able to form preorganised monolayers on planar electrodes can be expected to do the same on the surface of nanoparticles, leading to a surface sensing amplification effect. The very large surface area of nanoparticles could also allow greater overall sensitivity to anions. 

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