3 research outputs found
Wicking Nanopillar Arrays with Dual Roughness for Selective Transport and Fluorescence Measurements
Silicon
nanopillars are important building elements for innovative
nanoscale systems with unique optical, wetting, and chemical separation
functionalities. However, technologies for creating expansive pillars
arrays on the submicron scale are often complex and with practical
time, cost, and method limitations. Herein we demonstrate the rapid
fabrication of nanopillar arrays using the thermal dewetting of Pt
films with thicknesses in the range from 5 to 19 nm followed by anisotropic
reactive ion etching (RIE) of the substrate materials. A second level
of roughness on the sub-30 nm scale is added by overcoating the silicon
nanopillars with a conformal layer of porous silicon oxide (PSO) using
room temperature plasma enhanced chemical vapor deposition (PECVD).
This technique produced environmentally conscious, economically feasible,
expansive nanopillar arrays with a production pathway scalable to
industrial demands. The arrays were systematically analyzed for size,
density, and variability of the pillar dimensions. We show that these
stochastic arrays exhibit rapid wicking of various fluids and, when
functionalized with a physiosorbed layer of silicone oil, act as a
superhydrophobic surface. We also demonstrate high brightness fluorescence
and selective transport of model dye compounds on surfaces of the
implemented nanopillar arrays with two-tier roughness. The demonstrated
combination of functionalities creates a platform with attributes
inherently important for advanced separations and chemical analysis
Surface Modification of Silicon Pillar Arrays To Enhance Fluorescence Detection of Uranium and DNA
There is an ever-growing
need for detection methods that are both
sensitive and efficient, such that reagent and sample consumption
is minimized. Nanopillar arrays offer an attractive option to fill
this need by virtue of their small scale in conjunction with their
field enhancement intensity gains. This work investigates the use
of nanopillar substrates for the detection of the uranyl ion and DNA,
two analytes unalike but for their low quantum efficiencies combined
with the need for high-throughput analyses. Herein, the adaptability
of these platforms was explored, as methods for the successful surface
immobilization of both analytes were developed and compared, resulting
in a limit of detection for the uranyl ion of less than 1 ppm with
a 0.2 μL sample volume. Moreover, differentiation between single-stranded
and double-stranded DNA was possible, including qualitative identification
between double-stranded DNA and DNA of the same sequence, but with
a 10-base-pair mismatch
Nanopillar Based Enhanced-Fluorescence Detection of Surface-Immobilized Beryllium
The
unique properties associated with beryllium metal ensures the continued
use in many industries despite the documented health and environmental
risks. While engineered safeguards and personal protective equipment
can reduce risks associated with working with the metal, it has been
mandated by the Environmental Protection Agency (EPA) and Occupational
Safety and Health Administration (OSHA) that the workplace air and
surfaces must be monitored for toxic levels. While many methods have
been developed to monitor levels down to the low μg/m<sup>3</sup>, the complexity and expense of these methods have driven the investigation
into alternate methodologies. Herein, we use a combination of the
previously developed fluorescence Be(II) ion detection reagent, 10-hydroxybenzo[h]quinoline
(HBQ), with an optical field enhanced silicon nanopillar array, creating
a new surface immobilized (si-HBQ) platform. The si-HBQ platform allows
the positive control of the reagent for demonstrated reusability and
a pillar diameter based tunable enhancement. Furthermore, native silicon
nanopillars are overcoated with thin layers of porous silicon oxide
to develop an analytical platform capable of a 0.0006 μg/L limit
of detection (LOD) using sub-μL sample volumes. Additionally,
we demonstrate a method to multiplex the introduction of the sample
to the platform, with minimal 5.2% relative standard deviation (RSD)
at 0.1 μg/L, to accommodate the potentially large number of
samples needed to maintain industrial compliance. The minimal sample
and reagent volumes and lack of complex and highly specific instrumentation,
as well as positive control and reusability of traditionally consumable
reagents, create a platform that is accessible and economically advantageous