In nanobiotechnology, the importance of controlling interactions
between biological molecules and surfaces is paramount. In recent
years, many devices based on nanostructured silicon materials have
been presented, such as nanopores and nanochannels. However, there
is still a clear lack of simple, reliable, and efficient protocols
for preventing and controlling biomolecule adsorption in such structures.
In this work, we show a simple method for passivation or selective
biofunctionalization of silica, without the need for polymerization
reactions or vapor-phase deposition. The surface is simply exposed
stepwise to three different chemicals over the course of ∼1
h. First, the use of aminopropylsilatrane is used to create a monolayer
of amines, yielding more uniform layers than conventional silanization
protocols. Second, a cross-linker layer and click chemistry are used
to make the surface reactive toward thiols. In the third step, thick
and dense poly(ethylene glycol) brushes are prepared by a grafting-to
approach. The modified surfaces are shown to be superior to existing
options for silica modification, exhibiting ultralow fouling (a few
ng/cm2) after exposure to crude serum. In addition, by
including a fraction of biotinylated polymer end groups, the surface
can be functionalized further. We show that avidin can be detected
label-free from a serum solution with a selectivity (compared to nonspecific
binding) of more than 98% without the need for a reference channel.
Furthermore, we show that our method can passivate the interior of
150 nm × 100 nm nanochannels in silica, showing complete elimination
of adsorption of a sticky fluorescent protein. Additionally, our method
is shown to be compatible with modifications of solid-state nanopores
in 20 nm thin silicon nitride membranes and reduces the noise in the
ion current. We consider these findings highly important for the broad
field of nanobiotechnology, and we believe that our method will be
very useful for a great variety of surface-based sensors and analytical
devices.
The nuclear pore complex is a nanoscale assembly that achieves “shuttle-cargo” transport of biomolecules: a certain cargo molecule can only pass the barrier if it is attached to a shuttle...
Mercury is a highly
toxic heavy metal, and improved removal processes
are required in a range of industrial applications to limit the environmental
impacts. At present, no viable removal methods exist commercially
for mercury removal of aqueous solutions at high acidic conditions,
such as concentrated sulfuric acid. Herein, we show that electrochemical
mercury removal based on electrochemical alloy formation on platinum,
forming PtHg4, can be used to remove mercury from concentrated
sulfuric acid. Thin platinum film electrodes and porous electrodes
with supported platinum are used to remove more than 90% of mercury
from concentrated acid from a zinc smelter with an initial mercury
concentration of 0.3–0.9 mg/kg, achieving high-quality acid
(<0.08 mg/kg) within 80 h. The removal process is carried out in
50 mL laboratory-scale experiments and scaled up to a 20 L pilot reactor
with retained removal efficiency, highlighting excellent scalability
of the method. In addition, the removal efficiency and stability of
different electrode substrate materials are studied to ensure high-quality
acid and a long lifetime of the electrodes in harsh chemical conditions,
offering a potential method for future large-scale mercury decontamination
of sulfuric acid.
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