Surface sensing amplification

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. 

Conventional ion-selective electrodes have been used as detectors for immunoassays. Antibody binding measurements can be made with hapten-selective electrodes such as the trimethylphenylammonium ion electrode Enzyme immunoassays in which the enzyme label catalyzes the production of a product that is detected by an ion-selective or gas-sensing electrode take advantage of the amplification effect of enzyme catalysis in order to reach lower detection limits. Systems for hepatitis B surface antigen and estradiol use horseradish peroxidase as the enzyme label and... 

Patolsky F, Lichtenstein A, Willner I (2001) Electronic transduction of DNA sensing processes on surfaces amplification of DNA detection and analysis of single-base mismatches by tagged liposomes. J Am Chem Soc 123 5194-5205... 

A noncovalent chiral amplification based on the sergeants and soldiers effect between chiral and achiral polymers in the film state has been developed by Fujiki et al., which results in the formation of helix bundles (Fig. 35) [ 159]. An optically active, helical polysilane 84 with an almost single-handed screw-sense was chemically bonded or spin-coated on the surface of a quartz plate, followed by further spin-coating of an optically inactive polysilane 85 to give... 

Surface relief nanostructures may be used to create LSPs. In contrast to using particles to excite plasmons, surface relief patterns have an advantage of no aggregation and thus offer reliable sensing performance. Much part of the discussion addresses field enhancement in the near-field. Near-field enhancement can lead to amplification of signals produced by bio-molecular interactions near surface. 

No doubt, the present author has his own private consensus which, in spite of his efforts, may inject itself into the review. In order to offset such an undesirable bias, as much as possible, and perhaps putting the cart before the horse, the author will state here his own conclusions and beliefs I am convinced that electric field amplification and enhanced emission near SERS-active surfaces due to resonating metal excitations (surface-plasmon polaritons, plasmonlike modes, shape resonances, or electron-hole pairs) is an active mechanism in most of the systems studied. However, in most systems, this contribution, though an important one, is minor compared to the total enhancement possible in SERS. The major mechanism, in my opinion, must be a resonance mechanism, in the sense of a resonance Raman process, i.e., a mechanism by which a part of the system (molecule, molecule-metal atoms, metal surface) becomes a strong scatterer by virtue of its large resonance polarizability and not as a result of strong fields exerted by the other parts of the system . 

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