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Interactions between analyte molecules (in a liquid or gas phase) and sensitive layers of solid-state chemical sensors can provide a considerable amount of information, eg, for environmental control, life science, or food safety purposes. Such sensors are composed of two main elements: the sensing layer and the transducer. The former is the part that interacts directly with the analyte (ie, where the vapor molecules or biological analytes are physically or chemically adsorbed), and the transducer is necessary for converting these processes into a detectable electric signal.Surface plasmon polaritons (SPPs) are transverse electromagnetic waves bound to a metal–insulator interface (typically in thin metal films). SPPs are excited—with the use of gratings or prism couplers—when collective oscillations of conduction electrons create regions of enhanced electromagnetic fields in direct proximity to a metal sensor. These regions are highly sensitive to the local changes in refractive index that occur at the surface of the thin metal film. This sensitivity, in turn, provides a capability for a label-free form of analytical detection. For this reason, surface plasmon resonance (SPR) phenomena1, 2 are commonly used to measure the binding of biomolecules to gold surfaces, and for monitoring interactions between a sensing layer deposited on a metal transducer interface and gas/liquid molecule analytes. 1, 2 Current SPR technology, however, is associated with the low detection limits of amplitude-sensitive schemes. The sensitivity is therefore insufficient for label-free detection of low concentrations of low-molecular-weight analytes (eg, drugs, vitamins, or antigens …
Publication date: 
1 Jan 2014
Biblio References: 
Volume: 58 Pages: 114-120
Biosens. Bioelectron.