Using High Sensitivity NO₂ Sensors And Graphene Fluorescence Quenching Enhancement Enabled By Nanoporous Gold Structures

Nanoporous gold(NPG) is biocontinuous gold membrane with featured nanometer air pores. Such irregular connected air pores enables high surface-to-volume ratio as well as rapid gas transportation. In addition, the gold filaments which matches the wavelenth of light, sustain surface plasmons(SPs) and localized surface plasmons. Realizing the structure continuity, excellent thermal and electrical conductivity, and large surface area besides the characteristics of SP such as enhanced near fields and the subwavelength feature, nanoporous gold structure(NPG) is appealing to be a research platform in fields of basic researches and applications. In this thesis, two researches assisted by NPG are reported:First, bicontinuous Tin oxide(Sn O2) thin films were fabricated by atomic layer deposition(ALD), annealing, and acid washing with nanoporous gold(NPG) structure serving as templates. The resultant Sn O2 films show high sensitivity on NO2 gas. The detection limit is as low as 170 ppb in dry N2 flow and a rapid response/recovery time of 40/130 s. Interestingly, the responsibility increases dramatically when tested in air ambient, to be at two orders of magtitude larger than that measured in dry N2. We reveal that the performances of the gas sensor depend on the working temperatures and the exposure environments. Our study not only shows this bicontinuous Sn O2 films is promising for sensitive gas sensor but also provides insightful understanding on the NO2 gas sensing mechanism.Second, we hybridized graphene with the NPG structure, achieving enhanced quenching FRET applications. The hybrid structure offers new opportunities on highly sensitive detection of biomolecules. The capacity of electron extraction from Cd Se quantum dots by graphene is enhanced due to the graphene Fermi level adjustment via NPG coupling. Furthermore, the enhanced transition probability of photon-generated electron-hole pairs enabled by the enhanced near-field of SPs promote the Forster energy transfer and Dexter electron transfer process, which thus the cause of the intrinsic graphene quenching efficiency improving. Our study results are helpful on the explorations of highly sensitive FRET biosensor.