Plasmon resonance light absorption

The highest destruction ratio can be achieved by resonant absorption of laser light. Thereby to activate capsules remotely by laser light of near-IR band it is necessary to use plasmon-resonant particle absorption peak of which concides with laser... 

Another example of visible light-driven reaction through non-band-gap excitation is a photocatalytic reaction that uses surface-plasmon resonance (SPR) absorption of small metal particles loaded on base metal oxides. For example, gold particles of the size of ten to several ten nanometers, presenting purplish red color by the SPR absorption, loaded on titania particles have been used for photocatalytic reactions under visible-light irradiation at the wavelength of ca. 600 nm. Based on the results that titania or a related material is necessary for this visible fight-driven reactimi and that SPR absorption cannot induce electnaiic excitation of electrons, the mechanism of this kind of reaction seems complicated and is now under discussimi. 

K. Aydin, V.E. Ferry, R.M. Briggs, H.A. Atwater, Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers. Nat Commun. 2, 517... 

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. 

Fiber-optic biosensors are analytical devices in which a fiber optic device serves as a transduction element. The usual aim of fiber-optic biosensors is to produce a signal proportional to the concentration of target analyte to which the biological element reacts. Fiber-optic biosensors are based on the transmission of light along silica glass fiber, or POF to the site of analysis. They can be used in combination with different types of spectroscopic technique, e.g. absorption, fluorescence, phosphorescence, or surface plasmon resonance (SPR) (14). 

The field reaches its maximum at the surface plasmon resonance frequency when e = -2 Co where Co is the dielectric constant of the medium surrounding the particle surface. This induced field of the metallic nanoparticies provides an external field for the fluorescence excitation of the molecules in addition to the electric field of the incident light and thus increases the absorption rate which is responsible for the enhanced fluorescence intensity. 

The presence of MEF, MEP and Metal-Enhanced superoxide anion radical generation in the same system seems surprising at first, as these processes are effectively competitive and ultimately provide a route for deactivation of electronic excited states. As recently shown by the authors, simultaneous photophysical mechanisms can be present within the same system when enhanced absorption effects of the fluorophore near to silver are present (i.e. an enhanced excitation rate). In this case, enhanced absorption of Acridine near-to the plasmon resonant particles facilitates MEF, MEP, ME Oa and also Metal-Enhanced superoxide generation simultaneously within the same system. Aaidine showed an enhanced absorption spectra near-to silver, similar to other probes reported by the authors, in essence acridine absorbs more light. ... 

Strong enhancement of light absorption over the spectral range of the copper localized surface plasmon resonance has been observed at two-layer planar systems of copper and silver nanopaiticles made with the use of successive vacuum evaporation. The result obtained is treated with taking into account strong near-fieid coupling at a close-packed array of silver and copper nanoparticles. 

---