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conventional methods mainly based on high performance liquid
chromatography-mass spectrometry (HPLC-MS), which
are expensive and time-consuming.
In this framework, Cennamo et al. realized a novel approach
for the detection of perfluorobutanesulfonic acid
(PFBS) in water [28], exploiting a low-cost optical chemical
sensing strategy that is based on POFs and MIPs. PFBS is a
C4 perfluoroalkyl molecule which is difficult to remove with
common adsorbent media (for example, active carbons or ion
exchange resins). However, using an MIP it has been possible
to adsorb this substance, and the relative refractive index
variation of the MIP has been detected by SPR-POF technique.
The D-shaped POF-SPR platform, prepared as described in
[16], was coupled with an MIP able to recognize PFAs [29]. By
increasing the concentration of PFBS in water solution, the resonance
wavelength is shifted to smaller values, as shown in
Fig. 1a, while Fig. 1b presents the resonance wavelength as a
function of the PFBS concentrations along with the Hill fitting
of the experimental data.
A similar shift, already observed with perfluorooctanoic
acid (PFOA) or perfluorooctane sulfonic acid (PFOS) interaction
with the same MIP receptor [29], indicates a decrease in
the refractive index (RI) value of the MIP layer when the binding
occurs. The obtained LOD of PFBS in water solution was
lower than 1 ppb [28]. For this specific substance, there is not
a maximum residue limit fixed by the European Union regulations
yet. The proposed analytical approach demonstrated
the feasibility of monitoring pollutants in water, for example
PFAs, exploiting this kind of low-cost optical chemical sensor.
As many MIP receptors can be deposited on POF platforms
to detect various substances, the proposed method can be a
promising tool in Water Quality (WQ) monitoring in smart city
applications, considering that can be also conveniently linked
to the internet [20].
Conclusion
A brief overview on plasmonic optical fiber sensors has been
presented, focusing on some of the latest applications and
achievements related to their implementation. Among surface
plasmon resonance sensors, the class based on plastic optical
fibers represents the most promising approach for rapid and
real time sensing, thanks to the low-cost manufacturing process
and their easy handling. Their suitability to be integrated
with different kinds of MRE will allow future development
of other applications in many fields, addressing topics that
have been challenging to date such as environmental water
monitoring, on-field measurements and the development of
medical-diagnostic Point-Of-Care devices. Furthermore, the
possibility of connecting such types of sensors to the internet
makes them suitable for the development of several remote
sensing applications, opening new research activities, especially
towards IoT (Internet of Things) integrated technologies.
References
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Fig. 2. System architecture of Opto Spectrum System, a low-cost IT system
capable of storing and appropriate processing large amounts of data proposed
by Cennamo et al. [20]. (Adapted from [20], used with permission, ©IEEE,
2020).
August 2021
[11] H. Yu, Y. Chong, P. Zhang, J. Ma and D. Li, " A D-shaped fiber SPR
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