Simultaneous sensing of multiple gases by a single fluorescent-based gas sensor is of utmost importance for practical applications. Such sensing is strongly hindered by cross-sensitivity effects. In this study, we propose a novel analysis method to ameliorate such hindrance. The trial sensor used here was fabricated by coating platinum(II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and eosin-Y dye molecules on both sides of a filter paper for sensing O2 and NH3 gases simultaneously. The fluorescent peak intensities of the dyes can be quenched by the analytes and this phenomenon is used to identify the gas concentrations. Ideally, each dye is only sensitive to one gas species. However, the fluorescent peak related to O2 sensing is also quenched by NH3 and vice versa. Such cross-sensitivity strongly hinders gas concentration detection. Therefore, we have studied this cross-sensitivity effect systematically and thus proposed a new analysis method for accurate estimation of gas concentration. Comparing with a traditional method (neglecting cross-sensitivity), this analysis improves O2-detection error from −11.4% ± 34.3% to 2.0% ± 10.2% in a mixed background of NH3 and N2.
Porous anodic alumina oxide (AAO) is one of the most commonly used nanotemplates for growing arrays of nanoparticles, nanowires, nanocomposites, and nanoarchitectures because its pores, which are of a very uniform size, can grow longitudinally into arrays of self-aligned nanochannels with an extremely high aspect ratio. Furthermore, under specific combinations of anodization voltage and electrolyte, the lateral positions of nanochannels can self-organize into arrays of two-dimensional hexagonally close-packed lattices with domain sizes on the order of few tens of lattice units. The domain size can be greatly increased by prepatterning the Al surface with custom-designed nanoconcaves prior to the anodization process. The concaves guide the growth fronts of nanochannels and lead to the formation of an ideally long-range ordered lattice of nanochannel array. Such concaves have been fabricated by many methods, such as stamp imprinting, grating imprinting, and focused ion beam direct writing. In this review, we summarize the development of various methods to create AAO nanochannel arrays with custommade geometry and discuss the mechanism responsible for the guiding process.
K E Y W O R D Sanodic alumina, guided growth of anodic nanochannels, nanochannel arrays, nanotemplate
The
electromagnetic enhancement factor (M) of
a plasmonic nanostructure is the crucial quantity that characterizes
its enhanced optical effect. Retrieving it experimentally is however
stymied by the uncontrollable nuances in nanometer scale and by the
lack of a method to gauge the local field. We propose a method to
determine the enhancement factor of a plasmonic structure with narrow
gaps between adjacent metal nanoparticleshot spotsby
exciting the nanoparticles using a light pulse to assess their temperature
rise with simultaneously generated inelastic scattering radiation
and retrieving the electric field at the gap based on its simple relation
with the field inside the nanoparticles. The acquired enhancement
factors of Ag nanoparticle arrays with different gaps agree with the
values extracted by surface-enhanced Raman scattering and those predicted
theoretically. This study demonstrates a general method to retrieve
the enhancement factor of the plasmonic systems that are composed
of hot spots.
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