Printing technologies offer an attractive means for producing
low-cost
surface-enhanced Raman spectroscopy (SERS) substrates with high-throughput
methods. The development of these substrates is especially important
for field-deployable detection of environmental contaminants. Toward
this end, we demonstrate SERS-based substrates fabricated through
aerosol jet printing of silver nanoparticles and graphene inks on
Kapton films. Our printed arrays exhibited measurable intensities
for fluorescein and rhodamine dyes down to concentrations of 10–7 M, with the highest SERS intensities obtained for
four print passes of Ag nanoparticles. The substrates also exhibited
an excellent shelf life, with little reduction in fluorescein intensities
after 9 months of shelf storage. We also demonstrated the capability
of our substrates to sense perfluoroalkyl substances (PFAS), the so-called
forever chemicals that resist degradation due to their strong C–F
bonds and persist in the environment. Interestingly, the addition
of graphene to the Ag nanoparticles greatly enhanced the SERS intensity
of the perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid
(PFOS) molecules under basic conditions (pH ∼ 9) compared to
that of fluorescein and rhodamine. We were able to successfully detect
SERS spectra from nano- and picomolar (∼0.4 ppt) concentrations
of PFOA and PFOS, respectively, demonstrating the viability of deploying
our SERS sensors in the environment for the ultrasensitive detection
of contaminants.
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