Molecular spectroscopy, plasmon-enhanced

Keywords UV Ultraviolet spectroscopy FUV spectroscopy DUV spectroscopy Plasmonically enhance spectroscopy Surface-enhance Raman scattering Electronic transition Rydberg transition Molecular imaging Near-field microscopy Photocatalysis... 

The electromagnetic field enhancement provided by nanostructure plasmonics is the key factor to manipulate the quantum efficiency. However, as it is illustrated in the unified theory of enhancement, since both the radiative and non-radiative rates of the molecular systems are affected by proximity of the nanostructure, the tuning has to be done on a case by case basis. In addition, there are factors due to molecule-metal interactions and molecular orientation at the surface causing effects that are much more molecule dependent and as are much more difficult to predict. Given the fact that fluorescence cross sections are the one of the highest in optical spectroscopy the analytical horizon of SEF or MEF is enormous, in particular in the expanding field of nano-bio science. 

The simplest way to prepare a plasmonic nanostructure is thermal and electron beam deposition in vacuum on a flat substrate that is either hydrophilic or hydrophobic. Even though the roughness of the structure depends on the contact angle between the metal and substrate, which is less controllable, the method can be well applied to some metals. DUV plasmonic nanostructures were readily formed by thermal deposition of indium onto a glass substrate. The size of indium nanostructures can be controlled from 15 to 50 nm by the evaporation speed, pressure, and the deposited thickness. The resulting extinction peaks due to the dipole resonance were tuned to between 260 and 600 nm, which were used for surface enhancement of Raman spectroscopy by DUV excitation [7]. Self-assembled arrays of hemispherical gallium nanoparticles were deposited by molecular beam epitaxy on a sapphire support as a substrate for UV plasmonics. The mean NanoParticle radii of 23, 26, and 70 nm were fabricated at LSPR frequencies... 

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