SeS2B.3.pdf
Advanced Photonics © 2015 OSA
Sensing platforms exploiting surface plasmon resonance in polymeric optical fibers for chemical and biochemical applications Luigi Zeni1, Sabato D'Auria2, Maria Pesavento3, Letizia De Maria4, Nunzio Cennamo1 1
Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29- 81031 Aversa, Italy e-mail address: (LZ)
[email protected]; (NC)
[email protected] 2 Institute of Food Science, CNR, Via Roma 64- 83100 Avellino, Italy 3 Department of Chemistry, University of Pavia, Via Taramelli 12 - 27100 Pavia, Italy e-mail address:
[email protected] 4 Department of Transmission and Distribution Technologies, RSE, Via R. Rubattino 54- 20134 Milan, Italy e-mail address:
[email protected]
Abstract: An SPR sensor in POF, with possible implementation as bio/chemical sensor, is presented. This SPR-POF platform can be used in different application fields: industrial, medical diagnostics, environmental monitoring, food safety and security. 1. Introduction Surface plasmon resonance (SPR) is widely used as a detection principle for many sensors operating in different application fields, such as bio and chemical sensing. When artificial receptors are used for Bio/chemicals detection, the film on the metal surface selectively recognizes and captures the analyte present in a liquid sample so producing a local change in the refractive index at the metal surface. The refractive index change gives rise to a change in the propagation constant of the Surface Plasmon Wave (SPW) propagating along the metal surface which can be accurately measured as a shift of the resonance wavelength [1]. SPR is, in fact, known to be a very sensitive technique for determining refractive index variations at the interface between a metallic layer and a dielectric medium (analyte). In practical implementations, the biological targets are usually transported through a microfluidic system by means of a buffer or a carrier fluid. In the scientific literature, many different configurations based on SPR in silica optical fibers, have been described [2-4]. In general, the optical fiber employed is either a glass one or a plastic one (POF).The advantages of using POFs is that the properties of POFs, that have increased their popularity and competitiveness for telecommunications, are exactly those that are important for optical sensor. The use of optical fibers makes the remote sensing straightforward, and may reduce the cost and dimension of the device, with the possibility of integration of the SPR sensing platform with optoelectronic devices, eventually leading to “Lab-on-a-chip”. For low-cost sensing systems, POFs are especially advantageous due to their excellent flexibility, easy manipulation, great numerical aperture, large diameter, and the fact that plastic is able to withstand smaller bend radii than glass. In this paper, some SPR-POF bio/chemical sensor configurations are presented. The classic geometries of sensors based on SPR in silica optical fiber are adapted and borrowed for POF, so representing a simple approach to low cost plasmonic sensing [5,6]. When artificial receptors are used for Bio/chemicals detection, this low cost SPR-POF platform can be used in different fields: industrial applications, medical diagnostics, environmental monitoring, food safety and security.
2. SPR-POF sensing platform and applications The fabricated optical sensor system was realized removing the cladding of a plastic optical fiber along half the circumference, spin coating on the exposed core a buffer of Microposit S1813 photoresist, and finally sputtering a thin gold film using a sputtering machine [5]. In particular, the chosen fiber has a PMMA core of 980 μm and a fluorinated polymer cladding of 20 μm [6]. The refractive index, in the visible range of interest, is about 1.49 for PMMA, 1.41 for fluorinated polymer and 1.61 for Microposit S1813 photoresist. The device, shown in Fig. 1, consists in the plastic optical fiber without jacket embedded in a resin block, with the purpose of easing the polishing process. The polishing process is carried out with 5 μm and 1 μm polishing papers in order to remove the
SeS2B.3.pdf
Advanced Photonics © 2015 OSA
cladding and part of the core. The realized sensing region is about 10 mm in length. The buffer of Microposit S1813 photoresist is realized by depositing one drop (about 0.1 ml) on the center of the substrate and spinning it at 6,000 rpm for 60 seconds. The final thickness of the photoresist buffer is about 1.5 μm. Finally, a thin gold film is sputtered by using a sputtering machine (Bal-Tec SCD 500). The gold film so obtained is 60 nm thick and presents a good adhesion to the substrate, verified by its resistance to rinsing in de-ionized water, and it is also easy to functionalize with bio/chemical receptors. The experimental results indicate that the above configuration exhibits better performance in terms of detectable refractive index range and SNR with respect to the same device realized without the photoresist buffer [5].
Fig. 1. Multimode plastic optical fiber platform for bio/chemical applications
This platform, through the proper choice of the bio/chemical receptor layer, has been exploited for the selective detection and analysis of substances in aqueous and non-aqueous solutions, as for example mineral oil. The experimental setup is arranged to measure the light spectrum transmitted through the SPR-POF sensor and is characterized by a halogen lamp, illuminating the optical sensor system and a spectrum analyzer. The employed halogen lamp exhibits a wavelength emission range from 360 nm to 1,700 nm, while the spectrum analyzer detection range was from about 330 nm to 1,100 nm. An Ocean Optics USB2000+VIS-NIR spectrometer, controlled by a computer, is used. The SPR curves along with data values are displayed online on the computer screen and saved with the help of advanced software provided by Ocean Optics. The experimental data processing is carried out by Matlab software: SPR transmission spectra are normalized to the reference spectrum and the minimum, corresponding to the surface plasmon resonance wavelength, is identified. As an example, Figure 2 presents the experimentally obtained SPR transmission spectra, normalized to the spectrum achieved with air as the surrounding medium, of different water-glycerin solutions with the refractive index ranging from 1.330 to 1.390. In particular, results will be presented on the selective detection of trinitrotoluene (TNT), important in security applications [7], of furfural (furan-2-carbaldehyde) in transformer oil, very significant in industrial applications [8], of butanal, interesting in environmental monitoring and food safety [9], of transglutaminase/anti-transglutaminase antibodies useful in the diagnosis and/or follow-up of celiac disease [10], of Fe(III) [11] and L-nicotine [12], very important in clinical applications. Finally, the same basic device has also been exploited to excite localized surface plasmon resonance (LSPR) in gold nanoparticles dispersed in synthetic bio/chemical receptors, resulting in a more versatile sensor exhibiting, in some cases, a higher sensitivity than that of the sensor based on SPR [13, 14].
SeS2B.3.pdf
Advanced Photonics © 2015 OSA
Normalized Transmitted Light Intensity
1
0.98
0.96
0.94
1.330 1.340 1.350 1.360 1.370 1.380 1.390
0.92
0.9
0.88 550
600
650
700 Wavelength [nm]
750
800
Fig. 2. Experimentally obtained SPR transmission spectra, normalized to the reference spectrum, for different refractive indexes
3. Conclusions A simple optical platform based on the excitation of surface plasmons at the interface between an under test medium and a thin gold layer deposited on a photoresist film spin coated on a plastic fiber core, is presented along with some specific implementations, ranging from clinical to industrial applications. The proposed sensing device, being low cost and relatively easy to realize, is very attractive and promising for other bio/chemical sensors implementation also exploiting localized surface plasmon resonance. 4. References [1] [2] [3] [4] [5] [6] [7] [8]
[9] [10] [11] [12] [13]
[14]
J. Homola, "Present and future of surface plasmon resonance biosensors", Analytical and Bioanalytical Chemistry 377, 528–539 (2003). R.C. Jorgenson, S.S. Yee, "A fiber-optic chemical sensor based on surface plasmon resonance", Sensors and Actuators B, 12, 213–220 (1993). M. Kanso, S. Cuenot, G. Louarn, "Sensitivity of optical fiber sensor based on surface plasmon resonance: Modeling and experiments", Plasmonics, 3, 49–57 (2008). M. Iga, A. Sek, K. Watanabe, "Gold thickness dependence of SPR-based heterocore structured optical fiber sensor", Sensors and Actuators B 106, 363–368 (2005). N. Cennamo, D. Massarotti, L. Conte, L. Zeni, "Low cost sensors based on SPR in a plastic optical fiber for biosensor implementation", Sensors, 11, 11752–11760 (2011). N. Cennamo, D. Massarotti, R. Galatus, L. Conte, L. Zeni, "Performance Comparison of Two Sensors Based on Surface Plasmon Resonance in a Plastic Optical Fiber", Sensors, 13, 721-735 (2013). N. Cennamo, G. D'Agostino, R. Galatus, L. Bibbò, M. Pesavento, L. Zeni, "Sensors based on surface plasmon resonance in a plastic optical fiber for the detection of trinitrotoluene", Sensors and Actuators B, 188, 221-226 (2013). N. Cennamo, L. De Maria, G. D'Agostino, M. Pesavento, L. Zeni, "Combined Molecularly Imprinted Polymer and Surface Plasmon Resonance Transduction in Plastic Optical Fiber for Monitoring Oil-Filled Power Transformers", The 28th European Conference on Solid-State Transducers - Eurosensors 2014, (University of Brescia, Brescia- ITALY, 2014). N. Cennamo, S. Di Giovanni, A. Varriale, M. Staiano, F. Di Pietrantonio, A. Notargiacomo, L. Zeni, S. D’Auria, "Easy to use plastic optical fiber-based biosensor for detection of butanal", PLOS ONE, 2015 in press. N. Cennamo, A. Varriale, A. Pennacchio, M. Staiano, D. Massarotti, L. Zeni, S. D’Auria, "An innovative plastic optical fiber-based biosensor for new bio/applications. The Case of Celiac Disease", Sensors and Actuators B, 176, 1008–1014 (2013). N. Cennamo, G. Alberti, M. Pesavento, G. D'Agostino, F. Quattrini, R. Biesuz, L. Zeni, "A Simple Small Size and Low Cost Sensor Based on Surface Plasmon Resonance for Selective Detection of Fe(III)", Sensors, 14, 4657-4661 (2014). N. Cennamo, G. D'Agostino, M. Pesavento, L. Zeni, "High selectivity and sensitivity sensor based on MIP and SPR in tapered plastic optical fibers for the detection of L-nicotine", Sensors and Actuators B, 191, 529-536 (2014). N. Cennamo, G. D’Agostino, A. Donà, G. Dacarro, P. Pallavicini, M. Pesavento and L. Zeni, "Localized surface plasmon resonance with five-branched gold nanostars in a plastic optical fiber for bio-chemical sensor implementation", Sensors, 13, 14676-14686, 10.3390/s131114676 (2013). N. Cennamo, A. Donà, P. Pallavicini, G. D'Agostino, G. Dacarro, L. Zeni, M. Pesavento, "Sensitive detection of 2,4,6-trinitrotoluene by tridimensional monitoring of molecularly imprinted polymer with optical fiber and five-branched gold nanostars", Sensors and Actuators, B, 208, 291-298 (2015)
