Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS Optrodes
In this paper we report on the engineering of repeatable surface enhanced Raman scattering (SERS) optical fiber sensor devices (optrodes), as realized through nanosphere lithography. The Lab-on-Fiber SERS optrode consists of polystyrene nanospheres in a close-packed arrays configuration covered by a...
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MDPI AG
2018-02-01
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| Series: | Sensors |
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| Online Access: | http://www.mdpi.com/1424-8220/18/3/680 |
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| author | Giuseppe Quero Gianluigi Zito Stefano Managò Francesco Galeotti Marco Pisco Anna Chiara De Luca Andrea Cusano |
| author_facet | Giuseppe Quero Gianluigi Zito Stefano Managò Francesco Galeotti Marco Pisco Anna Chiara De Luca Andrea Cusano |
| author_sort | Giuseppe Quero |
| collection | DOAJ |
| description | In this paper we report on the engineering of repeatable surface enhanced Raman scattering (SERS) optical fiber sensor devices (optrodes), as realized through nanosphere lithography. The Lab-on-Fiber SERS optrode consists of polystyrene nanospheres in a close-packed arrays configuration covered by a thin film of gold on the optical fiber tip. The SERS surfaces were fabricated by using a nanosphere lithography approach that is already demonstrated as able to produce highly repeatable patterns on the fiber tip. In order to engineer and optimize the SERS probes, we first evaluated and compared the SERS performances in terms of Enhancement Factor (EF) pertaining to different patterns with different nanosphere diameters and gold thicknesses. To this aim, the EF of SERS surfaces with a pitch of 500, 750 and 1000 nm, and gold films of 20, 30 and 40 nm have been retrieved, adopting the SERS signal of a monolayer of biphenyl-4-thiol (BPT) as a reliable benchmark. The analysis allowed us to identify of the most promising SERS platform: for the samples with nanospheres diameter of 500 nm and gold thickness of 30 nm, we measured values of EF of 4 × 105, which is comparable with state-of-the-art SERS EF achievable with highly performing colloidal gold nanoparticles. The reproducibility of the SERS enhancement was thoroughly evaluated. In particular, the SERS intensity revealed intra-sample (i.e., between different spatial regions of a selected substrate) and inter-sample (i.e., between regions of different substrates) repeatability, with a relative standard deviation lower than 9 and 15%, respectively. Finally, in order to determine the most suitable optical fiber probe, in terms of excitation/collection efficiency and Raman background, we selected several commercially available optical fibers and tested them with a BPT solution used as benchmark. A fiber probe with a pure silica core of 200 µm diameter and high numerical aperture (i.e., 0.5) was found to be the most promising fiber platform, providing the best trade-off between high excitation/collection efficiency and low background. This work, thus, poses the basis for realizing reproducible and engineered Lab-on-Fiber SERS optrodes for in-situ trace detection directed toward highly advanced in vivo sensing. |
| first_indexed | 2024-04-11T20:46:43Z |
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| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-04-11T20:46:43Z |
| publishDate | 2018-02-01 |
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| spelling | doaj.art-de58db9b23584720b90ab04193bed3592022-12-22T04:04:00ZengMDPI AGSensors1424-82202018-02-0118368010.3390/s18030680s18030680Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS OptrodesGiuseppe Quero0Gianluigi Zito1Stefano Managò2Francesco Galeotti3Marco Pisco4Anna Chiara De Luca5Andrea Cusano6Optoelectronic Division-Engineering Department, University of Sannio, 82100 Benevento, ItalyInstitute of Protein Biochemistry, National Research Council, 80131 Napoli, ItalyInstitute of Protein Biochemistry, National Research Council, 80131 Napoli, ItalyInstitute for Macromolecular Studies, National Research Council, 20133 Milan, ItalyOptoelectronic Division-Engineering Department, University of Sannio, 82100 Benevento, ItalyInstitute of Protein Biochemistry, National Research Council, 80131 Napoli, ItalyOptoelectronic Division-Engineering Department, University of Sannio, 82100 Benevento, ItalyIn this paper we report on the engineering of repeatable surface enhanced Raman scattering (SERS) optical fiber sensor devices (optrodes), as realized through nanosphere lithography. The Lab-on-Fiber SERS optrode consists of polystyrene nanospheres in a close-packed arrays configuration covered by a thin film of gold on the optical fiber tip. The SERS surfaces were fabricated by using a nanosphere lithography approach that is already demonstrated as able to produce highly repeatable patterns on the fiber tip. In order to engineer and optimize the SERS probes, we first evaluated and compared the SERS performances in terms of Enhancement Factor (EF) pertaining to different patterns with different nanosphere diameters and gold thicknesses. To this aim, the EF of SERS surfaces with a pitch of 500, 750 and 1000 nm, and gold films of 20, 30 and 40 nm have been retrieved, adopting the SERS signal of a monolayer of biphenyl-4-thiol (BPT) as a reliable benchmark. The analysis allowed us to identify of the most promising SERS platform: for the samples with nanospheres diameter of 500 nm and gold thickness of 30 nm, we measured values of EF of 4 × 105, which is comparable with state-of-the-art SERS EF achievable with highly performing colloidal gold nanoparticles. The reproducibility of the SERS enhancement was thoroughly evaluated. In particular, the SERS intensity revealed intra-sample (i.e., between different spatial regions of a selected substrate) and inter-sample (i.e., between regions of different substrates) repeatability, with a relative standard deviation lower than 9 and 15%, respectively. Finally, in order to determine the most suitable optical fiber probe, in terms of excitation/collection efficiency and Raman background, we selected several commercially available optical fibers and tested them with a BPT solution used as benchmark. A fiber probe with a pure silica core of 200 µm diameter and high numerical aperture (i.e., 0.5) was found to be the most promising fiber platform, providing the best trade-off between high excitation/collection efficiency and low background. This work, thus, poses the basis for realizing reproducible and engineered Lab-on-Fiber SERS optrodes for in-situ trace detection directed toward highly advanced in vivo sensing.http://www.mdpi.com/1424-8220/18/3/680optical fiber sensoroptrodelab-on-fiberSERSself-assemblynanosphere lithography |
| spellingShingle | Giuseppe Quero Gianluigi Zito Stefano Managò Francesco Galeotti Marco Pisco Anna Chiara De Luca Andrea Cusano Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS Optrodes Sensors optical fiber sensor optrode lab-on-fiber SERS self-assembly nanosphere lithography |
| title | Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS Optrodes |
| title_full | Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS Optrodes |
| title_fullStr | Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS Optrodes |
| title_full_unstemmed | Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS Optrodes |
| title_short | Nanosphere Lithography on Fiber: Towards Engineered Lab-On-Fiber SERS Optrodes |
| title_sort | nanosphere lithography on fiber towards engineered lab on fiber sers optrodes |
| topic | optical fiber sensor optrode lab-on-fiber SERS self-assembly nanosphere lithography |
| url | http://www.mdpi.com/1424-8220/18/3/680 |
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