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Special Issue "SERS-Active Substrates"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (30 April 2018)

Special Issue Editors

Guest Editor
Prof. Fabrizio Giorgis

Department of Applied Science and Technology, Politecnico of Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy
Website | E-Mail
Interests: optics and photonics; plasmonics; nanotechnological processes; optical biosensing; surface-enhanced Raman scattering
Guest Editor
Prof. Hugo Aguas

Department of Materials Science / CENIMAT/i3N, Faculty of Science and Technology, NOVA University of Lisbon, CEMOP/UNINOVA, 2829-516 Caparica, Portugal
Website | E-Mail
Interests: microfluidics; optical sensors; biosensors; nanostructured metallic surfaces; surface-enhanced Raman spectroscopy (SERS) active substrates

Special Issue Information

Dear Colleagues,

Surface-enhanced Raman scattering/spectroscopy (SERS) has attracted increasing interest, both in terms of fundamental Physics/Chemistry and application in several fields, such as materials science, environmental sciences, sensors, biology, biophysics, and medicine. In fact, SERS can be exploited as a label-free detection method able to provide ultra-high sensitivity within biomolecular and chemical sensing. Typical SERS-active substrates are composed of noble metals (Au, Ag, Pt, etc.) in the form of roughened surfaces, nanoparticle aggregates, or arrayed elements.

Recently, a great deal of high quality research has been addressed to solid SERS nanostructured substrates, which can yield electromagnetic enhancement linked to surface plasmon resonances and/or chemical enhancement due to charge transfer processes. In addition to noble metals, semiconductors and transition metal-oxides have emerged as potential SERS-active substrates. The merging of electromagnetic and chemical enhancements can make SERS a powerful technique allowing vibrational spectra detection even from individual molecules. Moreover, microfluidic devices coupled with SERS detection methods are attracting great attention for the possibility to integrate in sensing platforms a biological or chemical protocol with a very sensitive technique, approaching a controlled analyte injection, a uniform molecular distribution and a reduced reagent volume.

This Special Issue aims to introduce recent progress in the synthesis and application of SERS-active substrates promoting a synergy of several complementary competences in the research community.

Prof. Fabrizio Giorgis
Prof. Hugo Aguas
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Raman spectroscopy
  • Surface-enhanced Raman scattering (SERS)
  • Plasmonic nanoparticles
  • Metal-dielectric nanostructures
  • Nano Technological fabrication
  • Low cost, efficient, uniform and reproducible SERS substrates fabrication technologies
  • Trace hazard substances detection
  • Portable SERS systems
  • Microfluidics
  • Biosensing

Published Papers (8 papers)

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Research

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Open AccessArticle Plasmonic Au Array SERS Substrate with Optimized Thin Film Oxide Substrate Layer
Materials 2018, 11(6), 942; https://doi.org/10.3390/ma11060942
Received: 26 April 2018 / Revised: 17 May 2018 / Accepted: 17 May 2018 / Published: 4 June 2018
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Abstract
This work studies the effect of a plasmonic array structure coupled with thin film oxide substrate layers on optical surface enhancement using a finite element method. Previous results have shown that as the nanowire spacing increases in the sub-100 nm range, enhancement decreases;
[...] Read more.
This work studies the effect of a plasmonic array structure coupled with thin film oxide substrate layers on optical surface enhancement using a finite element method. Previous results have shown that as the nanowire spacing increases in the sub-100 nm range, enhancement decreases; however, this work improves upon previous results by extending the range above 100 nm. It also averages optical enhancement across the entire device surface rather than localized regions, which gives a more practical estimate of the sensor response. A significant finding is that in higher ranges, optical enhancement does not always decrease but instead has additional plasmonic modes at greater nanowire and spacing dimensions resonant with the period of the structure and the incident light wavelength, making it possible to optimize enhancement in more accessibly fabricated nanowire array structures. This work also studies surface enhancement to optimize the geometries of plasmonic wires and oxide substrate thickness. Periodic oscillations of surface enhancement are observed at specific oxide thicknesses. These results will help improve future research by providing optimized geometries for SERS molecular sensors. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Open AccessFeature PaperArticle Plasmonic Nanowires for Wide Wavelength Range Molecular Sensing
Materials 2018, 11(5), 827; https://doi.org/10.3390/ma11050827
Received: 28 March 2018 / Revised: 6 May 2018 / Accepted: 14 May 2018 / Published: 17 May 2018
Cited by 1 | PDF Full-text (3611 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this paper, we propose the use of a standing nanowires array, constituted by plasmonic active gold wires grown on iron disks, and partially immersed in a supporting alumina matrix, for surface-enhanced Raman spectroscopy applications. The galvanic process was used to fabricate nanowires
[...] Read more.
In this paper, we propose the use of a standing nanowires array, constituted by plasmonic active gold wires grown on iron disks, and partially immersed in a supporting alumina matrix, for surface-enhanced Raman spectroscopy applications. The galvanic process was used to fabricate nanowires in pores of anodized alumina template, making this device cost-effective. This fabrication method allows for the selection of size, diameter, and spatial arrangement of nanowires. The proposed device, thanks to a detailed design analysis, demonstrates a broadband plasmonic enhancement effect useful for many standard excitation wavelengths in the visible and NIR. The trigonal pores arrangement gives an efficiency weakly dependent on polarization. The devices, tested with 633 and 830 nm laser lines, show a significant Raman enhancement factor, up to around 6 × 104, with respect to the flat gold surface, used as a reference for the measurements of the investigated molecules. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Open AccessArticle The Design and Optimization of Plasmonic Crystals for Surface Enhanced Raman Spectroscopy Using the Finite Difference Time Domain Method
Materials 2018, 11(5), 672; https://doi.org/10.3390/ma11050672
Received: 30 March 2018 / Revised: 19 April 2018 / Accepted: 24 April 2018 / Published: 26 April 2018
Cited by 1 | PDF Full-text (2639 KB) | HTML Full-text | XML Full-text
Abstract
We present computational studies of quasi three-dimensional nanowell (NW) and nanopost (NP) plasmonic crystals for applications in surface enhanced Raman spectroscopy (SERS). The NW and NP plasmonic crystals are metal coated arrays of cylindrical voids or posts, respectively, in a dielectric substrate characterized
[...] Read more.
We present computational studies of quasi three-dimensional nanowell (NW) and nanopost (NP) plasmonic crystals for applications in surface enhanced Raman spectroscopy (SERS). The NW and NP plasmonic crystals are metal coated arrays of cylindrical voids or posts, respectively, in a dielectric substrate characterized by a well/post diameter (D), relief depth (R D), periodicity (P), and metal thickness (M T). Each plasmonic crystal is modeled using the three-dimensional finite-difference time-domain (FDTD) method with periodic boundary conditions in the x- and y-directions applied to a computational unit cell to simulate the effect of a periodic array. Relative SERS responses are calculated from time-averaged electric field intensity enhancements at λ exc and λ scat or at λ mid via G SERS 4 = g 2 ( λ exc ) × g 2 ( λ scat ) or G mid 4 = g 4 ( λ mid ) , respectively, where g 2 = | E | 2 / | E 0 | 2 . Comparisons of G SERS 4 and G mid 4 are made to previously reported experimental SERS measurements for NW and NP geometries. Optimized NW and NP configurations based on variations of D, P, R D, and M T using G SERS 4 are presented, with 6× and 2× predicted increases in SERS, respectively. A novel plasmonic crystal based on square NP geometries are considered with an additional 3× increase over the optimized cylindrical NP geometry. NW geometries with imbedded spherical gold nanoparticles are considered, with 10× to 10 3 × increases in SERS responses over the NW geometry alone. The results promote the use of FDTD as a viable in silico route to the design and optimization of SERS active devices. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Open AccessFeature PaperArticle Optical Aggregation of Gold Nanoparticles for SERS Detection of Proteins and Toxins in Liquid Environment: Towards Ultrasensitive and Selective Detection
Materials 2018, 11(3), 440; https://doi.org/10.3390/ma11030440
Received: 19 January 2018 / Revised: 12 March 2018 / Accepted: 15 March 2018 / Published: 17 March 2018
Cited by 1 | PDF Full-text (5182 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Optical forces are used to aggregate plasmonic nanoparticles and create SERS–active hot spots in liquid. When biomolecules are added to the nanoparticles, high sensitivity SERS detection can be accomplished. Here, we pursue studies on Bovine Serum Albumin (BSA) detection, investigating the BSA–nanorod aggregations
[...] Read more.
Optical forces are used to aggregate plasmonic nanoparticles and create SERS–active hot spots in liquid. When biomolecules are added to the nanoparticles, high sensitivity SERS detection can be accomplished. Here, we pursue studies on Bovine Serum Albumin (BSA) detection, investigating the BSA–nanorod aggregations in a range from 100 µM to 50 nM by combining light scattering, plasmon resonance and SERS, and correlating the SERS signal with the concentration. Experimental data are fitted with a simple model describing the optical aggregation process. We show that BSA–nanorod complexes can be optically printed on non-functionalized glass surfaces, designing custom patterns stable with time. Furthermore, we demonstrate that this methodology can be used to detect catalase and hemoglobin, two Raman resonant biomolecules, at concentrations of 10 nM and 1 pM, respectively, i.e., well beyond the limit of detection of BSA. Finally, we show that nanorods functionalized with specific aptamers can be used to capture and detect Ochratoxin A, a fungal toxin found in food commodities and wine. This experiment represents the first step towards the addition of molecular specificity to this novel biosensor strategy. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Open AccessFeature PaperArticle TopUp SERS Substrates with Integrated Internal Standard
Materials 2018, 11(2), 325; https://doi.org/10.3390/ma11020325
Received: 11 December 2017 / Revised: 12 February 2018 / Accepted: 20 February 2018 / Published: 24 February 2018
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Abstract
Surface-enhanced Raman spectroscopy (SERS) is known as a molecular-specific and highly sensitive method. In order to enable the routine application of SERS, powerful SERS substrates are of great importance. Within this manuscript, a TopUp SERS substrate is introduced which is fabricated by a
[...] Read more.
Surface-enhanced Raman spectroscopy (SERS) is known as a molecular-specific and highly sensitive method. In order to enable the routine application of SERS, powerful SERS substrates are of great importance. Within this manuscript, a TopUp SERS substrate is introduced which is fabricated by a top-down process based on microstructuring as well as a bottom-up generation of silver nanostructures. The Raman signal of the support material acts as an internal standard in order to improve the quantification capabilities. The analyte molecule coverage of sulfamethoxazole on the surface of the nanostructures is characterized by the SERS signal evolution fitted by a Langmuir–Freundlich isotherm. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Open AccessFeature PaperArticle Optimization and Characterization of Paper-Made Surface Enhanced Raman Scattering (SERS) Substrates with Au and Ag NPs for Quantitative Analysis
Materials 2017, 10(12), 1365; https://doi.org/10.3390/ma10121365
Received: 20 October 2017 / Revised: 13 November 2017 / Accepted: 24 November 2017 / Published: 28 November 2017
Cited by 2 | PDF Full-text (4629 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, we present a systematic study on solid Surface Enhanced Raman Scattering (SERS) substrates consisting of Au and Ag nanoparticles (NPs) loaded on filter paper with the dip-coating method. The aim of this work is to explore how a series of
[...] Read more.
In this work, we present a systematic study on solid Surface Enhanced Raman Scattering (SERS) substrates consisting of Au and Ag nanoparticles (NPs) loaded on filter paper with the dip-coating method. The aim of this work is to explore how a series of parameters (e.g., concentration of colloidal solution, different porosity of filter paper, and the presence of an aggregating agent) affects the analytical performance of paper-based SERS substrates. All the substrates developed in this study have been analyzed with two non-resonant probe molecules, 4-mercaptobenzoic acid (4-MBA) and adenine, in terms of (i) inter-sample repeatability, (ii) intra-sample repeatability, (iii) sensitivity, and (iv) overall SERS performance in terms of analyte quantification. Moreover, the issue of how to evaluate the repeatability for a solid SERS substrate is carefully discussed. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Open AccessArticle 3D ZnO/Ag Surface-Enhanced Raman Scattering on Disposable and Flexible Cardboard Platforms
Materials 2017, 10(12), 1351; https://doi.org/10.3390/ma10121351
Received: 2 October 2017 / Revised: 20 November 2017 / Accepted: 21 November 2017 / Published: 24 November 2017
Cited by 1 | PDF Full-text (9309 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In the present study, zinc oxide (ZnO) nanorods (NRs) with a hexagonal structure have been synthesized via a hydrothermal method assisted by microwave radiation, using specialized cardboard materials as substrates. Cardboard-type substrates are cost-efficient and robust paper-based platforms that can be integrated into
[...] Read more.
In the present study, zinc oxide (ZnO) nanorods (NRs) with a hexagonal structure have been synthesized via a hydrothermal method assisted by microwave radiation, using specialized cardboard materials as substrates. Cardboard-type substrates are cost-efficient and robust paper-based platforms that can be integrated into several opto-electronic applications for medical diagnostics, analysis and/or quality control devices. This class of substrates also enables highly-sensitive Raman molecular detection, amiable to several different operational environments and target surfaces. The structural characterization of the ZnO NR arrays has been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical measurements. The effects of the synthesis time (5–30 min) and temperature (70–130 °C) of the ZnO NR arrays decorated with silver nanoparticles (AgNPs) have been investigated in view of their application for surface-enhanced Raman scattering (SERS) molecular detection. The size and density of the ZnO NRs, as well as those of the AgNPs, are shown to play a central role in the final SERS response. A Raman enhancement factor of 7 × 105 was obtained using rhodamine 6 G (R6G) as the test analyte; a ZnO NR array was produced for only 5 min at 70 °C. This condition presents higher ZnO NR and AgNP densities, thereby increasing the total number of plasmonic “hot-spots”, their volume coverage and the number of analyte molecules that are subject to enhanced sensing. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Review

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Open AccessReview Progress in the Development of SERS-Active Substrates Based on Metal-Coated Porous Silicon
Materials 2018, 11(5), 852; https://doi.org/10.3390/ma11050852
Received: 31 March 2018 / Revised: 7 May 2018 / Accepted: 14 May 2018 / Published: 21 May 2018
Cited by 1 | PDF Full-text (3085 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The present work gives an overview of the developments in surface-enhanced Raman scattering (SERS) with metal-coated porous silicon used as an active substrate. We focused this review on the research referenced to SERS-active materials based on porous silicon, beginning from the patent application
[...] Read more.
The present work gives an overview of the developments in surface-enhanced Raman scattering (SERS) with metal-coated porous silicon used as an active substrate. We focused this review on the research referenced to SERS-active materials based on porous silicon, beginning from the patent application in 2002 and enclosing the studies of this year. Porous silicon and metal deposition technologies are discussed. Since the earliest studies, a number of fundamentally different plasmonic nanostructures including metallic dendrites, quasi-ordered arrays of metallic nanoparticles (NPs), and metallic nanovoids have been grown on porous silicon, defined by the morphology of this host material. SERS-active substrates based on porous silicon have been found to combine a high and well-reproducible signal level, storage stability, cost-effective technology and handy use. They make it possible to identify and study many compounds including biomolecules with a detection limit varying from milli- to femtomolar concentrations. The progress reviewed here demonstrates the great prospects for the extensive use of the metal-coated porous silicon for bioanalysis by SERS-spectroscopy. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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