Highly sensitive, fast responsive, and highly reversible sensing of nitrogen dioxide, nitric oxide, and nitrous oxide at a ppm-to-sub-ppm level has been achieved by fluorescence measurements upon excitation of various dye-doped deoxyribonucleic acid (DNA) or hydrophobic DNA thin films spincoated on a thin silver film by electric-field-enhanced evanescent light at surface plasmon resonance. The response time, sensitivity, or selectivity was controlled by combination of dyes and matrices. The present result will make a great many contributions to environmental and medical applications.

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Photoreactions and aggregation of spiropyran with a long alkyl chain (SP98) were studied by surface reflection spectroscopy at the air-water interface. SP98 in mixtures with arachidic acid formed stable monolayers on pure water or on a subphase containing Cd2+. Colored photomerocyanine (PMC98) was formed at the air-water interface by UVirradiation. The reflection peak of PMC98 shifted from 545 nm to 618 nm with increasing 2+ surface pressure on a subphase containing Cd . The latter corresponded to the peak of aggregates observed in non-polar solutions. PMC98 formed 1-like aggregates at surface -1 2+ pressures above 10 -20 mN m on the subphase containing Cd , but hardly formed them on pure water. The back reaction from PMC98 to SP98 upon visible irradiation depended on the surface pressure and the subphase. About 36 % of aggregated PMC98 remained even after 90 min at 30 mN m , while at 10 and 1.5 mN m PMC98 converted completely to SP98 within 20 and 10 min, respectively.

Extremely sharp and uniform field-emitter arrays (FEAs) with low work function and environmentally resistant emitter materials, such as TiN and Au, have been fabricated by a transfer metal mold FEA fabrication method to realize highly efficient, highly reliable, and low-cost vacuum nanoelectronic devices and aerospace nanodevices for electric propulsion engines. The tip radii can be linearly controlled from 2.5 to 52.5 nm by changing the thickness of the emitter materials. For the first time, turn-on electric fields of the transfer metal mold FEAs have been controlled by changing tip radii. Control of turn-on field is one of requirements for realizing vacuum nanoelectronic devices, such as field-emission displays, aerospace devices, and so on. The transfer metal mold fabrication method is useful for controlling the turn-on fields and tip radii and conductive to changing emitter materials while maintaining sharp and uniform emitter shapes.

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