Designer plasmons

Another application of 2D arrays of subwavelength holes in metal has found an important use in light trapping for infrared detectors. It is based on the so-called designer plasmons. 

Fig. 2.60 Metallodielectric EOT structure introducing designed plasmons with stmcturally tunable plasma frequency...

In other words, the effective dielectric permittivity of an EOT array has a form identical to that of plasmonic materials. At the same time, its plasma frequency and thus its operating range can be freely mned to the wavelength range of interest. Such surface waves actually mimic real SPP, so that one can fabricate an effective plasmonic material with a desired spectmm. Pendry denoted these surface waves as designer plasmons and they are also known as spoof plasmons. 

The existence of designer SPP is extremely important for infrared photodetectors. One is able to fabricate any desired plasmonic structure and to tune it for the targeted wavelength range. As an example, infrared detectors enhanced by designer plasmon structures tuned to the range of 8-10 pm have been reported [311]. 

Ina similarmarmerto surface-enhanced Raman scattering, surface-enhancement of hyper-Raman scattering is a promising method to study adsorbed molecules on metal surfaces [24]. Based on recent developments in plasmonics, design and fabrication of metal substrates with high enhancement activities is now becoming possible [21]. Combination of the surface enhancement with the electronic resonances would also be helpful for the practical use of hyper-Raman spectroscopy. Development of enhanced hyper-Raman spectroscopy is awaited for the study of solid/liquid interfaces. 

In these sensors, the intrinsic absorption of the analyte is measured directly. No indicator chemistry is involved. Thus, it is more a kind of remote spectroscopy, except that the instrument comes to the sample (rather than the sample to the instrument or cuvette). Numerous geometries have been designed for plain fiber chemical sensors, all kinds of spectroscopies (from IR to mid-IR and visible to the UV from Raman to light scatter, and from fluorescence and phosphorescence intensity to the respective decay times) have been exploited, and more sophisticated methods including evanescent wave spectroscopy and surface plasmon resonance have been applied. 

Using this screening approach, a fourfold amplification of the designed library member A-P was observed. Interestingly, a fivefold amplification of the peptidic dimer P-P was also observed. Amplification factors correlated well with dissociation constants (K ) subsequently measured by surface plasmon resonance (SPR) A-P was found to have a of 30 [tM, while the more strongly amplified P-P was found to have a of 22.5 [tM. 

AB, Switzerland) in SPR (surface plasmon resonance) studies. The PLL-PEG-biotin-sAV was used for microarray studies as described for the commercial product. A detailed description of the design and physical and chemical characterization of the PLL-grafted PEG monolayer is provided by Ruiz-Taylor et al. (2001). 

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