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In this work, a surface plasmon resonance (SPR) multiparameter sensor for simultaneous determination of refractive index and temperature was manufactured through a novel and low-cost approach. Monitoring these parameters is useful when biosensors are developed by exploiting SPR phenomena. A polymer planar optical structure was realized via inkjet 3D printing, by using photo-curable resins having tailored refractive index for device’s core and cladding, respectively. The multiparameter sensor was fully designed, manufactured, and experimentally tested to check the numerical analyses run on a preliminary phase. In such a way, a temperature resolution equal to about 0.5°C and a refractive index resolution equal to about 2 × 10−4 RIU (refractive index unit) were obtained. Next, even a quality control analysis of the 3D printed surface was carried out by following a novel approach that relies on the profile monitoring technique, with the aim to evaluate the suitability of the design and the geometric accuracy control. In addition, thanks to the cost analysis performed through a properly model, it was proved that the multiparameter sensor designed, manufactured, and tested satisfies the low-cost requirements, being the estimated cost ~ 23 €, which is an absolutely competitive cost if compared with other traditional sensors. In the end, even the performance of the sensor in terms of bulk sensitivity (equal to about 900nm/RIU) resulted to be higher than similar devices already presented in the state-of-the-art, thus proving the validity of the developed SPR multiparameter sensor both in economic and performance terms. Graphical abstract: [Figure not available: see fulltext.]

A novel sensing method for temperature measurements of liquids, exploiting plasmonic resonance in multimode plastic optical fibers (POFs), has been devised. The possibility to measure the temperature is useful in several application fields of plasmonic sensors, such as when a binding test between a receptor and an analyte occurs, considering that the binding parameters are a function of the temperature. The novel temperature sensor consists of two different D-shaped POF connected in a cascade. The first element is a thermosensitive platform with a thin silicone layer on the POF core, whereas the second is a conventional surface plasmon resonance (SPR) D-shaped POF sensor. The operating principle of the novel temperature sensor is based on the variations of light launch conditions in the SPR-POF sensor as a consequence of the temperature changes in the solution covering the thermosensitive platform. In this way, the input light ray angle changes with the temperature, producing a shift in resonance wavelength conditions. The proposed sensor has been tested, as proof of concept, in a temperature range from 20°C to 38°C with a step size of 3°C , to establish the role of the silicone layer on the thermosensitive platform and the best configuration in terms of sensitivity.

The use of optical fibers has evolved from an optical transmission waveguide to a more intricated device for bio-chemical sensing. The possibility of measuring target substances with rapid and low-cost tools is still a main challenge in different application fields, from environmental monitoring to the medical-diagnostic sector. In recent decades, plasmonic fiber-optic sensors have gained great interest due to their excellent sensitivity and compactness, allowing the possibility of remote sensing for different target analytes that is real-time and label-free. Such sensors have constantly evolved over time. In this work, a short overview on plasmonic optical fiber sensors is presented, including illustrations that focus on the applications and achievements so far.

A low-cost plasmonic sensor based on a polymeric light diffusive optical fiber (LDF) has been designed, realized, and experimentally tested. The developed surface plasmon resonance (SPR) sensor has been realized by sputtering a gold nanofilm on the LDF. The work also presents a simple modal filter, realized by covering the LDF with an aqueous solution. Notably, this modal filter improves the signal-to-noise ratio (SNR) of the SPR sensor thanks to the filtering of the higher modes, without losing its sensitivity.

In this work, a Surface Plasmon Resonance (SPR) multiparameter sensor for simultaneous determination of refractive index and temperature was manufactured through a novel and low-cost approach. A polymer planar optical structure was realized via inkjet 3D printing, by using photo-curable resins having tailored refractive index for device’s core and cladding, respectively. The multiparameter sensor was fully designed, manufactured, and experimentally tested to check the numerical analyses run on a preliminary phase. In such a way, a temperature resolution equal to about 0.5°C and a refractive index resolution equal to about 2 x 10^-4 RIU were obtained. Next, even a quality control analysis of the 3D printed surface was carried out by following a novel approach that relies on the profile monitoring technique, with the aim to evaluate the suitability of the design and the geometric accuracy control. In addition, thanks to the cost analysis performed through a properly model, it was proved that the multiparameter sensor designed, manufactured and tested satisfies the low – cost requirements, being the estimated cost ~ 23 €, which is an absolutely competitive cost if compared with other traditional sensors. In the end, even the performance of the sensor in terms of bulk sensitivity (equal to about 900 nm/RIU) resulted to be higher than similar devices already presented in the state – of – the – art, thus proving the validity of the developed SPR multiparameter sensor both in economic and performance terms.

In this work, a novel optical fiber sensor system for ultra-low perfluorooctanoic acid (PFOA) detection in aqueous solutions is proposed. It is based on the connection, in series, of two different plastic optical fiber (POF) platforms: the first is a chemical chip realized by using a D-shaped POF with microholes filled with a specific molecularly imprinted polymer (MIP); the second is a typical surface plasmon resonance (SPR) sensor based on a D-shaped POF. In particular, the MIP-based chemical chip was used to launch the light inside the SPR–POF chip to change the SPR phenomenon by exploiting the PFOA–MIP interaction in the microholes. At first, experimental results were performed in water to demonstrate the applicability of the proposed sensing approach for measuring PFOA (or C8) in a concentration range of 1 ppt to 750 ppt, obtaining an ultra-low limit of detection (LOD) equal to about 0.81 ppt. Then, experimental results were carried out in simulated seawater to implement a complex matrix. The obtained results denoted a slight matrix effect, paving the way for the applicability of the proposed chemical sensing mechanism in several aqueous solutions.

Stress is a normal physiological and behavioral response to a stimulus that somehow disturbs the maintenance of homeostasis, leading to changes in cortisol levels. When stress is persistent and uncontrolled, it can severely affect several areas, such as human health and some marine biology sectors, including aquaculture production. Currently, the detection of cortisol is performed in laboratories using conventional techniques with several disadvantages, one of them being the long waiting time for a response. Therefore, it is essential the development of miniaturized analytical devices capable of monitoring in real-time, detecting and quantifying cortisol in point of care (POC). Special optical fiber structure, in this case, D-shape in silica optical fibers (SOF) and polymeric optical fibers (POF) coated with gold (Au) were used in this work for the development of immunosensors based on surface plasmon resonance (SPR) for cortisol (stress hormone) detection. In the laboratory, Au coated SOF (Au-SOF) and Au coated POF (Au-POF) were initially characterized at refractive index (RI) with eight glucose concentrations ranging from 1.333 to 1.386 RI units (RIU). The obtained sensitivities were, respectively, 1646.67 ± 91.66 nm/RIU, being lower than the simulated one with 2138.95 ± 142.65 nm/RIU, and 1566.81 ± 96.87 nm/RIU. Subsequently, the fibers were functionalized with anti-cortisol antibodies using cysteamine as the intermediate linker to allow the immobilization of the antibodies to the Au surface. After this procedure, both immunosensors were tested for cortisol concentrations ranging from 0.1 to 100 ng/ml to compare the performances, in which the Au-SOF and Au-POF immunosensors presented a total resonance wavelength shift of 3.22 and 2.10 nm, and sensitivities of 1.08 ± 0.21 nm/log(ng/mL) and 0.52 ± 0.03 nm/log(ng/mL), respectively. Different limits of detection (LODs) were calculated using different methods for each type of immunosensor. One method consisted in performing a Hill fitting to the results and another considering the response of the control interferents. For Au-SOF and Au-POF, the LODs attained through the first method were 0.12 and 0.13 ng/mL (considering the resonance wavelength shift), respectively, and 0.14 ng/mL considering the intensity variation of Au-POF. The second method enabled a LOD of 1.75 and 1.97 ng/mL for Au-SOF and Au-POF, respectively.

In this paper, we propose a dual wavelength scheme for the detection of liquids based on optically absorbing (Co2+-doped) optical fibers. The proposed configuration makes use of a Coherent-Optical Time Domain Reflectometer (C-OTDR) operating with standard fibers at 850 nm. Besides vibration measurements over all the sensing fiber, the proposed scheme performs liquid detection in short sections of Co2+-doped fibers, heated by a modulated optical pump at 1550 nm. We demonstrate that the proposed sensor detects the liquids surrounding the doped fiber, such as water or acetone.

Soft, deformable, molecularly imprinted nanoparticles (nanoMIPs) were combined to nano-plasmonic sensor chips realized on poly (methyl methacrylate) (PMMA) substrates to develop highly sensitive bio/chemical sensors. NanoMIPs (dmean < 50 nm), which are tailor-made nanoreceptors prepared by a template assisted synthesis, were made selective to bind Bovine Serum Albumin (BSA), and were herein used to functionalize gold optical nanostructures placed on a PMMA substrate, this latter acting as a slab waveguide. We compared nanoMIP-functionalized non-optimized gold nanogratings based on periodic nano-stripes to optimized nanogratings with a deposited ultra-thin MIP layer (

This work presents the design, the implementation, and the testing of a novel tool relative to plasmonic sensors in waveguides. A novel tool gathers all the latest information technology to speed up and improve the quality of the results of the experiments done. The developed tool is very simple to use and can be applied in several plasmonic sensor configurations, where the measurements can be carried out in spectral mode. The realized tool will be useful in different application fields, such as in point-of-care applications, environment monitoring, Internet of things (IoT) applications, security, and industrial applications. The key features will be portability and performance, taking advantage of technological developments, either hardware and software.

An optical sensor for uranyl has been prepared based on a gold-plated D-shaped plastic optical fiber (POF) combined with a receptor consisting of a bifunctional synthetic molecule, 11-mercaptoundecylphosphonic acid (MUPA), with a phosphonic group for complexing the considered ion, and a sulfide moiety through which the molecule is fixed at the gold resonant surface as a molecular layer in an easy and reproducible way. The sensor is characterized by evaluating the response in function of the uranyl concentration in aqueous solutions of different compositions and real-life samples, such as tap water and seawater. The mechanism of the uranyl/MUPA interaction was investigated. Two different kinds of interactions of uranyl with the MUPA layer on gold from water are observed: a strong one and a weak one. In the presence of competing metal ions as Ca2+ and Mg2+, only the strong interaction takes place, with a high affinity constant (around 107 M−1), while a somewhat lower constant (i.e., around 106 M−1) is obtained in the presence of Mg2+ which forms stronger complexes with MUPA than Ca2+. Due to the high affinity and the good selectivity of the recognition element MUPA, a detection limit of a few μg L−1 is reached directly in natural water samples without any time-consuming sample pretreatment, making it possible for rapid, in situ controls of uranyl by the proposed sensor.

In this paper, we demonstrate automatic vehicle detection and counting by processing data acquired using a phase-sensitive optical time-domain reflectometer (

A specific aptameric sequence has been immobilized on short polyethyleneglycol (PEG) interface on gold nano-film deposited on a D-shaped plastic optical fiber (POFs) probe, and the protein binding has been monitored exploiting the very sensitive surface plasmon resonance (SPR) phenomenon. The receptor-binding domain (RBD) of the SARS-CoV-2 spike glycoprotein has been specifically used to develop an aptasensor. Surface analysis techniques coupled to fluorescence microscopy and plasmonic analysis have been utilized to characterize the biointerface. Spanning a wide protein range (25 ÷ 1000 nM), the SARS-Cov-2 spike protein was detected with a Limit of Detection (LoD) of about 37 nM. Different interferents (BSA, AH1N1 hemagglutinin protein and MERS spike protein) have been tested confirming the specificity of our aptasensor. Finally, a preliminary test in diluted human serum encouraged its application in a point-of-care device, since POF-based aptasensor represent a potentially low-cost compact biosensor, characterized by a rapid response, a small size and could be an ideal laboratory portable diagnostic tool., Graphical abstract Image 1

Several surface plasmon resonance (SPR) sensors in optical fibers have been presented for the detection of magnetic fields. These SPR sensors measure the variation of the refractive index of a magnetic fluid in contact to the metal film, when the magnetic field changes. In this work, we have presented a different approach to monitor a magnetic field exploiting SPR optical fiber sensors and ferrofluids. More specifically, we have inserted a patch of multimode plastic optical fiber (POF) covered with ferrofluids between a light source and an SPR-POF sensor connected to a spectrometer. The magnetic field in the region near the patch covered by ferrofluids exerts a bending force on the patch changing the light in input to the SPR sensor and modifying the SPR phenomenon, in terms of resonance’s shape and wavelength.

This PRISMA-ScR driven scoping review aims to evaluate the influence of magnetic field stimulation on dental implant osseointegration. Seven databases were screened adopting ad-hoc strings. All clinical and preclinical studies analyzing the effects of magnetic fields on dental implant osseointegration were included. From 3124 initial items, on the basis of the eligibility criteria, 33 articles, regarding both Pulsed ElectroMagnetic Fields (PEMF) and Static magnetic Fields from permanent Magnets (SFM) were finally included and critically analyzed. In vitro studies showed a positive effect of PEMF, but contrasting effects of SFM on bone cell proliferation, whereas cell adhesion and osteogenic differentiation were induced by both types of stimulation. In vivo studies showed an increased bone-to-implant contact rate in different animal models and clinical studies revealed positive effects on implant stability, under magnetic stimulation. In conclusion, although positive effects of magnetic exposure on osteogenesis activity and osseointegration emerged, this scoping review highlighted the need for further preclinical and clinical studies. More standardized designs, accurate choice of stimulation parameters, adequate methods of evaluation of the outcomes, greater sample size and longer follow-ups are needed to clearly assess the effect of magnetic fields on dental implant osseointegration.

In this work, a novel sensing approach to realize a force optical fiber sensor is designed, developed, and experimentally tested. The proposed sensing methodology exploits the effects of deformation due to an applied force on a patch of plastic optical fiber (POF) connected at the input of a surface plasmon resonance (SPR) sensor realized in a D-shaped POF. Therefore, the proposed force sensor system consists of an SPR D-shaped POF sensor, connected to a spectrometer, within input of a POF patch, connected to a light source used for interacting with the applied force. When the applied force on the patch changes, the mode profile of the light in the multimode POF patch and the SPR-POF sensor change too, so the SPR spectra shift. The obtained experimental results demonstrate that the proposed sensor has a resolution of the force sensor equal to about 22 mN and an excellent linear response in the range from 0 N to 0.5 N.

A surface plasmon resonance (SPR) platform, based on a D-shaped plastic optical fiber (POF), combined with a biomimetic receptor, i.e., a molecularly imprinted polymer (MIP), is proposed to detect 2-furaldheide (2-FAL) in fermented beverages such as wine. The determination of 2-FAL in food samples is becoming a very crucial task, on the one hand for its role in the flavor and on the other in relation to its toxic and carcinogenic effects on human beings. The proposed sensing device is easy to use and cheap; it has been tested successfully for the detection and quantification of substances of interest in different fields, such as health, the environment and industry. The possibility of performing single-drop measurements is a further favorable aspect for practical applications. As an example, the use of an SPR-MIP sensor for the analysis of 2-FAL in wine, in a concentration range useful for practical applications, is here described.

The optical properties of multimode plastic optical fibers (POFs) could be used for both the monitoring of magnetic field and for the tuning of plasmonic phenomenon, when a magnetic fluid was deposited on its cladding and it is connected in input to a plasmonic POF sensor. In this case, a magnetic field exerts a bending force on the POF covered with magnetic fluid, thus producing a variation of light in input to the plasmonic POF sensor and changing the plasmonic phenomenon. In particular, the focus of this work is the assessment of the tuning mechanism for the plasmonic phenomenon, which has been performed through a dedicated measurement approach. Preliminary experimental results are here presented to demonstrate how this approach can be used to change several plasmonic parameters, such as the sensitivity and the signal-to-noise ratio (SNR). This approach could be used in biosensing applications, where even smaller variation of the plasmonic response can significantly improve the detection of substances.

We reported a low-cost optical chemical sensor for the detection of furfural (furan-2-carbaldehyde, 2-FAL) in aqueous media. This novel optical sensor platform is based on a PET (polyethylene terephthalate) substrate with a pattern of silver nanoparticles, printed on it by InkJet technology. To obtain the selective detection of the analyte, the slab waveguide has been covered by a specific molecularly imprinted polymer (MIP) for 2-FAL. The sensing device has connected to a light source and a spectrometer by two plastic optical fibers (POFs), to monitor the interaction between the MIP and 2-FAL. The performances reported in this work are comparable to those of plasmonic POF sensors combined with the same MIP.

The selective detection of pollutants in water in a laboratory scenario has been presented by authors exploiting low-cost optical biosensors based on plastic optical fibers (POFs) and biological or biomimetic receptors. So, for instance, the detection in water of naphthalene, perfluoroalkyl substances (PFAs) and polyfluoroalkyl substances have been investigated with interesting detection limits when compared to those obtained by using different expensive traditional approaches (e.g., liquid chromatography-mass spectrometry with high performances). In this article, we have developed and tested a novel approach used in a smart measuring system to use POF sensors in situ for the remote measures of pollutants in water for smart cities applications. More specifically, we have used different water–glycerin solutions to test the novel sensor system based on a Raspberry Pi connected to the Internet and to a spectrometer, a light source, a POF sensor, and two computers connected to Internet used as client and server.

Different lines of evidence indicate that monitoring the blood levels of therapeutic antibodies, characterized by high inter-individual variability, can help to optimize clinical decision making, improving patient outcomes and reducing costs with these expensive treatments. A surface plasmon resonance (SPR)-based immunoassay has recently been shown to allow highly reliable and robust monitoring of serum concentrations of infliximab, with significant advantages over classical ELISA. The next level of advancement would be the availability of compact and transportable SPR devices suitable for easy, fast and cheap point-of-care analysis. Here we report the data obtained with recently developed, cost-effective, optical-fibre-based SPR sensors (SPR-POF), which allow the construction of a compact miniaturized system for remote sensing. We carried out an extensive characterization of infliximab binding to an anti-infliximab antibody immobilized on the SPR-POF sensor surface. The present proof-of-principle studies demonstrate the feasibility of the proposed SPR-POF platform for the specific detection of infliximab, in both buffer and human serum, and pave the way for further technological improvements.

A novel low-cost surface plasmon resonance (SPR) platform has been tested, for the first time, to monitor the interaction between a molecularly imprinted polymer (MIP) and a small molecule as the substrate. As a proof of principle, the considered MIP was specific for furfural (2-FAL, MW = 96.4), so that the possibility of using the new device for detection of 2-FAL in aqueous media was investigated. For the sake of comparison a sensor based on the same MIP specific for 2-FAL deposited on an SPR platform in a D-shaped plastic optical fiber (POF), which has been previously demonstrated to well perform for different analytes, has been considered too. The experimental results showed good performances of the novel platform for chemical sensing based on MIP as receptor in terms of selectivity, sensitivity and figure of merit (FOM). The limit of detection (LOD) of this simple and low-cost SPR sensor system is about 0.03 ppm, completely comparable to that of previously proposed devices based on SPR in a D-shaped POF (about 0.05 ppm), but with the advantage of an easier and more reproducible preparation procedure.

The goal of this work is to test the possibility of selective detection of furfural (2-FAL) in aqueous solutions, with a molecularly imprinted polymer (MIP) receptor exploiting two different transduction methods, for food safety applications. In particular, sensors with electrochemical and surface plasmon resonance (SPR) transduction are considered. Two concentration ranges could be investigated by the different sensing approaches since the detectable concentration level depends on the sensitivity of the detection technique employed. The determination of 2-FAL at different concentration levels in the aqueous medium of interest, as for example beverages, is becoming a very crucial task not only for the relevance of furanic compounds in affecting the flavor but also for their possible toxic and carcinogenic effects on the human beings. For these reasons, their determination by a fast, easy and low-cost method is of interest. The sensor methods here proposed appears to be particularly suitable, since, although together and not individually, they allow the determination in a wide concentration range.

We present a comparative study of three optical sensing platforms based on surface plasmon resonance (SPR) in plastic optical fibers (POFs). The proposed sensors consist of a D–shaped POF sensing area, where the exposed core is covered by a photoresist layer, used as intermediate layer between the fiber’s core and the metal (gold) film. The photoresist deposited on the exposed core in the D–shaped POF region, is pivotal in order to improve the performances of the sensor in terms of sensitivity. In particular, we have compared the performances of three different buffer layers based on the following photoresist: Microposit SU-8 3005, Microposit S1813 before and after the expiry date.

Soft molecularly imprinted nanogels (nanoMIPs), selective for human transferrin (HTR), were prepared via a template assisted synthesis. Owing to their soft matter, the nanoMIPs were observed to deform at binding to HTR: while no relevant changes were observed in the hydrodynamic sizes of HTR-free compared to HTR-loaded nanoMIPs, the HTR binding resulted in a significant increment of the nanoMIP stiffness, with the mean Young's modulus measured by AFM passing from 17 ± 6 kPa to 56 ± 18 kPa. When coupled to a plastic optical fibre (POF) plasmonic platform, the analyte-induced nanoMIP-deformations amplified the resonance shift, enabling to attain ultra-low sensitivities (LOD = 1.2 fM; linear dynamic range of concentrations from 1.2 fM to 1.8 pM). Therefore, soft molecularly imprinted nanogels that obey to analyte-induced deformation stand as a novel class of sensitivity-gain structures for plasmonic sensing.

Authors recall two high sensitive, small size, and low-cost surface plasmon resonance (SPR) sensors based on plastic optical fibers (POFs): the first one, a D-shaped SPR intrinsic POF sensor, the second one an SPR extrinsic POF sensor. These plasmonic POF sensors, intrinsic and extrinsic, combined with different kinds of specific receptors can be directly connected to an online platform by a software interface, allowing storing, analyzing and displaying the sensor's data, to realize low-cost biochemical sensors for several applications. The simple experimental setup, used for both these SPR POF sensor configurations, was arranged to measure the light spectrum transmitted through the plasmonic platform, exploiting a halogen lamp and a spectrometer connected to a PC.

The COVID-19 pandemic has emphasized the need for portable, small-size, low-cost, simple to use, and highly sensitive sensors able to measure a specific substance, with the capability of the transmission over the Internet of statistical data, such as in this specific case on the spread of the SARS-CoV-2 virions. Moreover, to resolve the COVID-19 emergency, the possibility of making selective SARS-CoV-2 measurements in different aqueous matrices could be advantageous. Thus, the realization of rapid and innovative point-of-care diagnostics tests has become a global priority. In response to the current need for quick, highly sensitive and on-site detection of the SARS-CoV-2 virions in different aqueous solutions, two different nanolayer biorecognition systems separately combined with an adaptable optical fiber sensor have been reported in this work. More specifically, two SARS-CoV-2 sensors have been developed and tested by exploiting a plasmonic plastic optical fiber (POF) sensor coupled with two different receptors, both designed for the specific recognition of the SARS-CoV-2 Spike protein; one is aptamer-based and the other one Molecular Imprinted Polymer-based. The preliminary tests on SARS-CoV-2 virions, performed on samples of nasopharyngeal (NP) swabs in universal transport medium (UTM), were compared with data obtained using reverse-transcription polymerase chain reaction (RT-PCR). According to these preliminary experimental results obtained exploiting both receptors, the sensitivity of the proposed SARS-CoV-2 optical fiber sensors proved to be high enough to detect virions. Furthermore, a relatively fast response time (a few minutes) to detect virions was obtained without additional reagents, with the capability to transmit the data via the Internet automatically.

In this work, a novel approach to realize a plasmonic sensor is presented. The proposed optical sensor device is designed, manufactured, and experimentally tested. Two photo-curable resins are used to 3D print a surface plasmon resonance (SPR) sensor. Both numerical and experimental analyses are presented in the paper. The numerical and experimental results confirm that the 3D printed SPR sensor presents performances, in term of figure of merit (FOM), very similar to other SPR sensors made using plastic optical fibers (POFs). For the 3D printed sensor, the measured FOM is 13.6 versus 13.4 for the SPR-POF configuration. The cost analysis shows that the 3D printed SPR sensor can be manufactured at low cost (∼15 €) that is competitive with traditional sensors. The approach presented here allows to realize an innovative SPR sensor showing low-cost, 3D-printing manufacturing free design and the feasibility to be integrated with other optical devices on the same plastic planar support, thus opening undisclosed future for the optical sensor systems.

We present a hybrid Brillouin/Rayleigh sensor for multiparameter sensing in optical fibers. The system makes use of a single laser pulse to excite both Rayleigh and Brillouin backscattering in the same optical fiber. In the detection path, the backscattered signals are separated based on their different wavelengths. The system is capable of determining simultaneously the Brillouin frequency shift (BFS) of the fiber, as well as the frequency contents of any vibration acting on the same fiber as recovered by phase sensitive OTDR (ϕ-OTDR) measurements. The reported experiments show the possibility to perform simultaneous temperature and vibration measurements, as well as to perform dynamic strain measurements combining the information provided by slope-assisted Brillouin scattering measurements, with those provided by amplitude-based ϕ-OTDR measurements.

In this work, an unconventional light-diffusing fiber (LDF) plasmonic platform is exploited to efficiently monitor a bio-interaction. The surface plasmon resonance (SPR)-LDF sensor is used to detect the immunoglobulin G (IgG)/anti-IgG interaction as exemplifying bioassay. The IgG bioreceptor was deposited on the gold surface of the SPR-LDF platform, and the biological target was transported through a customized thermo-stabilized flow cell by means of a buffer fluid. Moreover, to test the usability of the proposed SPR-LDF biosensor also for immunosensing in complex matrices, a second assay was conducted by immobilizing anti-C-reactive protein (CRP) and detecting different concentrations of CRP in human serum. An innovative data analysis approach for the extraction of the best value of the resonance wavelength was developed and applied. The obtained results reveal that the unconventional platform represented by the LDF can be successfully exploited for the implementation of SPR-based biosensors with very good performances, also when compared to more common SPR systems.

The possibility of developing a multichannel optical chemical sensor, based on molecularly imprinted polymers (MIPs) and surface plasmon resonance (SPR) in a D-shaped multimode plastic optical fiber (POF), is presented by two cascaded SPR-POF-MIP sensors with different thicknesses of the gold layer. The low cost, the high selectivity and sensitivity of the SPR-POF-MIP platforms and the simple and modular scheme of the optical interrogation layout make this system a potentially suitable on-line multi-diagnostic tool. As a proof of principle, the possibility of simultaneous determination of two important analytes, dibenzyl disulfide (DBDS) and furfural (2-FAL), in power transformer oil was investigated. Their presence gives useful indication of underway corrosive or ageing processes in power transformers, respectively. Preliminarily, the dependence of the performance of the D-shaped optical platform on the gold film thickness has been studied, comparing two platforms with 30 nm and 60 nm thick gold layers. It has been found that the resonance wavelengths are different on platforms with gold layer of different thickness, furthermore when MIPs are present on the gold as receptors, the performances of the platforms are similar in the two considered sensors. Keywords: Cascaded multianalyte detection, Surface plasmon resonance, Dibenzyl disulfide, Furfural (furan-2-carbaldehyde), Molecularly imprinted polymers, Plastic optical fibers

Two sensors for the detection of the metal ion Cu(II), based on the same sensing layer, are compared. They rely on different transduction methods, i.e., electrochemistry and surface plasmon resonance (SPR). D,L-penicillamine was used as the specific receptor since it is a strong ligand for copper(II). Moreover it is easily immobilized on a gold layer by a self assembling procedure by contacting the gold layer overnight with water/EtOH (80/20) containing D,L-penicillamine, taking advantage of the spontaneous interaction of thiols with gold surfaces. Both the electrochemical and SPR platforms were derivatized in the same way. In the first case a gold disc was used as working electrode, and in the second one a thin gold layer (60 nm thick) was deposited by sputtering over the exposed core of a plastic optical fiber (POF), after removing the cladding along half circumference.

The detection of perfluorobutanesulfonic acid (PFBS) in water is presented for the first time exploiting a low-cost optical chemical sensing strategy, based on plastic optical fibers and molecularly imprinted polymers (MIPs), able to detect pollutants in water. The sensor’s response measured in this work for the detection of PFBS is similar to the one obtained with Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA), already investigated. The detection limit of PFBS is considered of interest when compared to those obtained by using different expensive traditional approaches, e.g. high performance liquid chromatography-mass spectrometry (HPLC-MS). Moreover, the use of this sensing approach is a very attractive perspective for fast, in situ, and remote low-cost detection of pollutants in water for smart cities applications.

We present a multichannel optical chemical sensor based on molecularly imprinted polymers (MIPs) and surface plasmon resonance (SPR) in a D-shaped plastic optical fiber (POF), for simultaneous determination of two important analytes, dibenzyl disulfide, and furfural, whose presence in the transformer oil is an indication of underway corrosive or ageing processes, respectively, in power transformers. Furthermore, an investigation on the dependence of performances of this optical platform on the gold film thickness is reported. The low cost, highly selective, and sensitive performance of the SPR-POF-MIP platforms and the simple and modular scheme of the optical interrogation layout make this system a potentially suitable on-line diagnostic tool for power transformers.

Optical chemosensors offer a decisive solution to monitor critical parameters in power transformers, as they can operate safely on electrical equipment. Surface Plasmon Resonance (SPR) is widely used as a detection principle for many sensors operating in different fields, such as bio and chemical sensing. Its use with optical fibers makes the remote SPR sensing straightforward and suitable for applications also in presence of high electromagnetic interferences, as in the case of power transformers. Additionally, a low-cost sensing device is achieved when an SPR chemical sensor is implemented in a plastic optical fiber (POF) in which an artificial receptor of chemical agents in different liquid environments is exploited. In this work, we report an overview on the main results about the feasibility of application of a developed SPR-POF sensor for the detection, in oil matrix, of two markers of the paper-oil insulating system degradation in oil-filled transformer.