A Three Component-Based Van Der Waals Surface Vertically Designed for Biomolecular Recognition Enhancement
2020
Graphene-based vertical electrodes may
have applications in biomolecular recognition for producing low-cost biodevices
with high electronic conductivity. However, they are unsuitable for measuring small
interfacial capacitance variations because graphene is mostly composed of basal
sp2 carbon surface, which limits its sensitivity as an
electrochemical biosensor. Herein, we introduce an unconventional device alternative
based on a three-component vertically designed (TCVD) surface comprising
ferrocene/graphene/gold deposited on SiO2/Si wafers. Ferrocene is
the top layer that promotes reversible redox communication with the electrolyte,
while graphene–gold is the strategically projected layer underneath. Bader
charge analysis indicated that graphene donates electronic density to the gold
surface, thereby significantly increases the charge transfer exchange rate with
ferrocene. The TCVD surface is much more reactive and sensitive to charge variations
compared with pristine graphene, and it maintains excellent conductive
properties. The TCVD device was used to detect DNA hybridization in solutions,
since this is well-known to be a challenging process on a pristine graphene
vertical device. A TCVD device can detect small interfacial charge perturbations
from DNA hybridization. Based on quantum mechanics calculations combined with spectromicroscopy
data, it was realized that the unique synergic interaction between gold and graphene
amplified biomolecular recognition, whereby DNA in nanomolar range
concentration correlated to 0.8 ± 0.1 µF cm-2, which was effortlessly
detected. This result is promising since 3.0 µF cm-2 is the limit of
quantum capacitance for bare graphene. Notably, these results open a new
possibility for next-generation TCVD bioelectronics based on van der Waals
surfaces, while further innovation and material scrutiny may lead to the
achievement of TCVD devices with robust biomolecular recognition abilities.
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