Citation: Cennamo, N.; Arcadio, F.;
Capasso, F.; Maniglio, D.; Zeni, L.;
Bossi, A.M. Non-Specific Responsive
Nanogels and Plasmonics to Design
MathMaterial Sensing Interfaces: The
Case of a Solvent Sensor. Sensors
2022, 22, 10006.
https://doi.org/10.3390/s222410006
Academic Editor: Yurui Fang
Received: 25 October 2022
Accepted: 14 December 2022
Published: 19 December 2022
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Article
Non-Specific Responsive Nanogels and Plasmonics to Design
MathMaterial Sensing Interfaces: The Case of a Solvent Sensor
Nunzio Cennamo
1
, Francesco Arcadio
1
, Fiore Capasso
1
, Devid Maniglio
2
, Luigi Zeni
1
and Alessandra Maria Bossi
3,
*
1
Department of Engineering, University of Campania Luigi Vanvitelli, Via Roma 29, 81031 Aversa, Italy
2
Department of Industrial Engineering, BIOtech Research Center, University of Trento, Via delle Regole 101,
Mattarello, 38123 Trento, Italy
3
Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy
* Correspondence: alessandramaria.bossi@univr.it
Abstract:
The combination of non-specific deformable nanogels and plasmonic optical probes pro-
vides an innovative solution for specific sensing using a generalistic recognition layer. Soft poly-
acrylamide nanogels that lack specific selectivity but are characterized by responsive behavior, i.e.,
shrinking and swelling dependent on the surrounding environment, were grafted to a gold plasmonic
D-shaped plastic optical fiber (POF) probe. The nanogel–POF cyclically challenged with water or
alcoholic solutions optically reported the reversible solvent-to-phase transitions of the nanomaterial,
embodying a primary optical switch. Additionally, the non-specific nanogel–POF interface exhibited
more degrees of freedom through which specific sensing was enabled. The real-time monitoring of the
refractive index variations due to the time-related volume-to-phase transition effects of the nanogels
enabled us to determine the environment’s characteristics and broadly classify solvents. Hence the
nanogel–POF interface was a descriptor of mathematical functions for substance identification and
classification processes. These results epitomize the concept of responsive non-specific nanomaterials
to perform a multiparametric description of the environment, offering a specific set of features for the
processing stage and particularly suitable for machine and deep learning. Thus, soft MathMaterial
interfaces provide the ground to devise devices suitable for the next generation of smart intelligent
sensing processes.
Keywords:
responsive nanomaterials; plasmonics; chemical sensor; MathMaterial; artificial intelligence;
interface; nanogel; multidimensional sensing
1. Introduction
Bio/chemical sensing is a two-component process in which a recognition element
and a transducer jointly work to generate a measurable response in the presence of the
target analyte. Recognition elements, that span across a variety of materials, such as
inorganics, organics, and biologicals, are meant to interact with the analyte molecule and
are contiguous to the transducer. Transducers, meant to translate a molecular interaction
into a measurable electronic signal, belong to different classes depending on their physical
working principles (electrochemical, piezoelectric, electrical, electronic, optical, etc.) [1].
In a typical sensor’s design, the chosen recognition element should match the trans-
ducer [
2
] and ensure a specific and selective interaction with the analyte. It follows the
paradigm that a one-sensor system provides specific information about a single analyte.
Under this model, multi-sensorial functions can be achieved by the sum of several one-
sensor units. Clustering together, sensors provide multiple-sensing platforms, i.e., sensor
arrays. Arrays consist of different recognition elements; a similar transducer, multiple
transducers, or both [
3
]. The sensor array provides a multi-faced description of the system
under analysis by combining the outputs of each single element. The epitome of the one-
sensing unit’s array is the electronic nose (E-nose) [
4
]. The E-nose is a multi-sensorial device
Sensors 2022, 22, 10006. https://doi.org/10.3390/s222410006 https://www.mdpi.com/journal/sensors
