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Electrical Double Layer-Induced Ion Surface Accumulation for Ultrasensitive Refractive Index Sensing with Nanostructured Porous Silicon Interferometers
journal contribution
posted on 2018-01-04, 00:00 authored by Stefano Mariani, Lucanos Marsilio Strambini, Giuseppe BarillaroHerein, we provide
the first experimental evidence on the use of
electrical double layer (EDL)-induced accumulation of charged ions
(using both Na+ and K+ ions in water as the
model) onto a negatively charged nanostructured surface (e.g., thermally
growth SiO2)Ion Surface Accumulation, ISAas
a means of improving performance of nanostructured porous silicon
(PSi) interferometers for optical refractometric applications. Nanostructured
PSi interferometers are very promising optical platforms for refractive
index sensing due to PSi huge specific surface (hundreds of m2 per gram) and low preparation cost (less than $0.01 per 8
in. silicon wafer), though they have shown poor resolution (R) and detection limit (DL) (on the order of 10–4–10–5 RIU) compared to other plasmonic and
photonic platforms (R and DL on the order of 10–7–10–8 RIU). This can be ascribed
to both low sensitivity and high noise floor of PSi interferometers
when bulk refractive index variation of the solution infiltrating
the nanopores either approaches or is below 10–4 RIU. Electrical double layer-induced ion surface accumulation (EDL-ISA)
on oxidized PSi interferometers allows the interferometer output signal
(spectral interferogram) to be impressively amplified at bulk refractive
index variation below 10–4 RIU, increasing, in turn,
sensitivity up to 2 orders of magnitude and allowing reliable measurement
of refractive index variations to be carried out with both DL and
R of 10–7 RIU. This represents a 250-fold-improvement
(at least) with respect to the state-of-the-art literature on PSi
refractometers and pushes PSi interferometer performance to that of
state-of-the-art ultrasensitive photonics/plasmonics refractive index
platforms.
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Keywords
RIUplatformPSi interferometerslayer-induced ion surface accumulationDLISAUltrasensitive Refractive IndexEDL-ISAEDLindex variationNanostructured PSi interferometersinterferometer output signalElectrical Double Layer-Induced Ion Surface AccumulationPSi interferometer performanceNanostructured Porous Silicon Interferometers Herein
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