Ultrasensitive inkjet-printed based SERS sensor combining a high-performance gold nanosphere ink and hydrophobic paper

https://doi.org/10.1016/j.snb.2020.128412Get rights and content

Highlights

  • Fabrication of an inkjet-printed paper-based SERS platform.

  • An effective AuSph Ink was developed with high stability over 1 year of storage.

  • Improvement of SERS capabilities by a hydrophobic modification of the paper.

  • Ultrasensitive quantification of thiram at 10−11 M with low sample volume (2 μL).

  • Reliable, robust and ultralow-cost SERS substrates (less than $ 0.01 per spot).

Abstract

We report the fabrication of a low-cost paper-based SERS platform with enhanced sensing capabilities. The sensor consists of a highly concentrated glycerol/ethanol dispersion of ca. 77 nm Au nanospheres (AuSph) inkjet-printed on hydrophobic chromatographic paper forming circular sensing spots of 1 mm in diameter. The AuSph ink exhibits high stability for 1 year. Interestingly, we demonstrate that the modification of the paper surface with hydrophobic ligands improve the sensing capabilities by confining the analyte solution in the AuSph sensing platform. It contributes to both concentrate the analyte, as well as, to decrease the sample volume to just a few μl. We also analyze the effect of the amount of the nanoparticles, tunable by the number of printing cycles, in the SERS performance of the plasmonic spots. The results show that 5 printing cycles give rise to sensing platforms with great SERS response in terms of intensity and uniformity. The spot-to-spot reproducibility is also analyzed observing good results even for AuSph spots from different printed papers. The paper-based SERS platform was tested towards the detection of crystal violet (CV) and the fungicide thiram. Additionally, applying a digital protocol for SERS analysis, a good linear correlation between the digital counts (or positive events) and the analyte concentration was obtained at the single-molecule SERS regime. In both cases, the quantification region threshold was 10−11 M. The great sensitivity performance of the inkjet-printed SERS substrate is reflected by the low sample volume needed (only 2 μL). The inkjet-printed SERS substrate and the fabrication method demonstrated to be efficient, reliable, reproducible and robust, with a cost less than $ 0.01 per spot.

Introduction

Surface-Enhanced Raman Spectroscopy (SERS) is a versatile analytical technique widely used for qualitative and quantitative analysis due to its several advantages such as minimal sample preparation, simple measurement acquisition, shorter time for sample preparation and analysis among others. Additionally, Raman scattering exhibits sharply and discernible molecular fingerprint peaks with high multiplexing potential in biosensing and bioimaging applications [1]. One of the main advantages relies on the low limit of detection in the order of 10−9 – 10-12 M achieved by the technique, presenting a high potential to achieve ultralow detection limits as low as 10-13 and 10-20 M measured in small amounts of sample (few microliters) [[2], [3], [4], [5], [6]]. Owing to its high sensitivity, SERS is widely applied in several areas that require low detection limits, such as food safety [7,8], drug detection [9,10], detection of viruses [11] and investigation of bioactive metabolites in microbial communities [12].

In SERS, the inelastic light scattering by molecules is greatly enhanced when the molecules are adsorbed onto rough metal surfaces such as silver or gold nanoparticles. The main responsible factor for the high SERS intensity is the localized surface plasmon resonance (LSPR) of the metallic nanoparticles which leads to an enhancement of the electric field on their proximity [13]. Although the SERS effect can be obtained from the electric field enhancement at single nanoparticles (NP), a considerable higher enhancement can be reached by placing the molecules within nanometer-sized gaps between two metallic nanoparticles (so-called hot spots). The electric field enhancement at the hot spot effect is extremely important at low concentrations, particularly at the single-molecule SERS regime (SM-SERS regime), since a molecule adsorbed on a hot spot can lead to a SERS intensity 102 up to 105 higher than several molecules adsorbed on random nanoparticles [13,14].

The development of new SERS platforms has been widely explored because of the high demand for analysis with a low detection limit in several fields. The ideal SERS substrate should be highly stable and highly reproducible in terms of SERS activity and also cost-effective. In this way, extensive research is being carried out to improve the SERS efficiency by using versatile shape- and size-controlled plasmonic nanoparticles [[15], [16], [17], [18]]. From the point of view of the substrate and particularly the nanoparticle deposition, different methodologies have been explored such as electrospinning [19], self-assembly [16,20], and electro-deposition combined with lithography [21].

Alternatively, the use of paper as a platform for the fabrication of SERS-active surfaces has been exploring since the mid-1980 [[22], [23], [24], [25]] due to its many advantages over conventional SERS substrates, such as the low-cost, flexibility, high commercial availability, derived from renewable sources, and compatibility with biomolecules, making such substrates very attractive for its commercialization. The paper-based SERS substrate can be obtained by different methods, including in-situ growth of nanoparticles on paper [26], vacuum filtration method [27], immersion in nanoparticle colloid [28,29], screen printing [30], and drop-wise [31]. Lee et al. [32] used the dip-coating method to fabricate a paper-based SERS substrate with a common filter paper which presented higher efficiency on the detection of 1,4-benzenedithiol 10−3 M compared to the conventional silicon substrate. The flexibility of the paper-based substrate is responsible for the greater performance since it allows its friction against the surface of a sample for better adherence of the analyte. Polavarapu et al. [33] proposed a new deposition method for the production of a paper-based SERS substrate, where they used a fountain pen filled with plasmonic nanoparticles inks to directly draw SERS arrays on the paper substrate. The proposed substrates achieved low detection limits such as 10-12 M of rhodamine 6 G and 20 ppb of thiabendazole (approximately 10-7 M) with a sample volume of 10 μL. Additionally, hydrophobic paper-based SERS substrates have been demonstrated great performance in SERS experiments [31,34]. The hydrophobic modification of the paper surface is a key step in the production of the paper-based SERS substrates since it allows the local concentration of analyte on the plasmonic sensing region. Additionally, it can increase the number of hot spots by the same concentration effect.

The SERS-based sensors can be considered as a very promising platform in the application of point-of-care (PoC) devices since they could combine ultralow detection limit, minimal sample preparation, nondestructive analysis, and fingerprinting identification to the demand of rapid detection, real-time measurements, sensitive analysis, and portability of such devices. Among them, SERS-based microfluidic substrates are one class of platforms widely used as PoC devices. The preparation and application of microfluidic SERS substrates are described in a comprehensive review [35]. Among the SERS platforms used for the application of PoC devices [6,[36], [37], [38], [39]], paper-based SERS substrates gained attention due to the additional advantages of using paper as the substrate as mentioned before [27,[40], [41], [42]]. Moreover, many efforts have been made to miniaturize the portable Raman spectrometer to improve and innovate the technology of SERS-based PoC devices by reducing its size and making it simpler while maintaining its efficiency [27,41,43].

In 2008, the inkjet-printing method was first applied for the fabrication of SERS substrates by using metallic nanoparticle ink [44]. Thereafter, White and collaborators explored the inkjet-printing technique as a highlighted method in the production of paper-based SERS substrates [34,[45], [46], [47]]. Since then, the inkjet-printing technique has been explored in the fabrication of SERS-active substrates [42,[48], [49], [50]]. The deposition method has the advantages of low-cost and simplicity by employing a common office printer to print a nanoparticle ink directly on paper, and the substrate can be designed in a simple software. Additionally, piezoelectric inkjet printers present the advantage concerning the mechanism of dropping the ink out the nozzle in the response of an electrical current. In contrast to thermal inkjet printers, it allows low manufacturing temperature, preventing possible destabilization of the colloidal suspension.

In the present work, we report the fabrication of a hydrophobic paper-based SERS substrate with enhanced SERS capabilities by the inkjet-printing method. In order to achieve that, we combined an effective and highly stable gold nanospheres (AuSph) ink with a hydrophobic paper based on surface-modified chromatographic paper. The SERS substrates were designed as circular spots with a diameter of ca. 1 mm and the printing was carried out on a desktop inkjet printer. The SERS performance, using crystal violet as the probe molecule, demonstrated great reproducibility from spot-to-spot between different prints and high sensitivity of the substrate. Finally, the inkjet-printed SERS substrate was applied for the detection and quantification of thiram, which is a dithiocarbamate fungicide used for the protection of fruits such as apple, peach, and strawberries in the field and also during transport and storage [51]. The fungicide is a neurotoxicant regulated by the Environmental Protection Agency of USA (EPA) due to its neurotoxic effects such as lethargy and reduced motor activity [51]. Interestingly, a SERS analysis based on a recently developed digital protocol allowed the quantification at ultralow concentrations while working at the SM-SERS regime.

Section snippets

Reagents and solutions

For the synthesis of AuSph, hydrogen tetrachloroaurate(III) trihydrate (HAuCl4.3H2O, ≥99.9 %), cetyltrimethylammonium bromide (CTAB, ≥99 %), trisodium citrate dihydrate (≥98 %) and l-ascorbic acid (≥99 %) were purchased from Sigma-Aldrich. For the paper surface modification, cellulose chromatographic paper (Whatman™), (2-dodecen-1-yl)-succinic anhydride (DDSA, 95 %), and 1-hexanol (98 %) were purchased from Sigma-Aldrich. For the AuSph ink, glycerol (≥99.5 %) and absolute ethanol (99.5 %) were

AuSph ink synthesis

The production of the AuSph Ink involved a two-step approach. Firstly, an AuSph colloid was prepared through a seed-mediated approach [52]. Fig. 1a shows a representative TEM image of the Au nanoparticles showing a relatively high size and shape homogeneity with ca. 24 % of the nanoparticles being nonspherical. The AuSph nanoparticles presented an average diameter of 76.3 ± 3.5 nm (n = 250) as determined by TEM analysis (see Fig. S1 in the SI). Secondly, the particles were washed, concentrated,

Conclusions

In conclusion, we report the fabrication of a low-cost and facile inkjet-printed plasmonic paper-based SERS platform with high SERS efficiency. The great SERS performance of the substrates relies on the one hand the great stability of a highly concentrated AuSph ink (over 1 year of storage), and on the other hand, the surface modification of the paper to render it hydrophobic allowing the concentration of the analyte upon evaporation. The great reproducibility of the SERS intensity between

CRediT authorship contribution statement

N.V. Godoy: Methodology, Investigation, Writing - original draft, Formal analysis. D. García-Lojo: Methodology, Formal analysis. F.A. Sigoli: Supervision, Resources. J. Pérez-Juste: Supervision, Resources, Writing - review & editing. I. Pastoriza-Santos: Supervision, Resources, Writing - review & editing. I.O. Mazali: Conceptualization, Supervision, Writing - review & editing, Project administration, Resources, Funding acquisition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. The authors also would like to thank the FAPESP and CNPq for financial supports, CAPES for the doctoral scholarship, and International Mobility Santander Programme for a scholarship. J.P.-J. and I.P.-S. acknowledge the Ministerio de Economía y Competitividad (MINECO, Spain) grant: MAT2016-77809-R, Xunta de Galicia/FEDER (grant: GRC ED431C 2016-048) and the

Naiara V. Godoy obtained Bachelor degree in Chemistry in 2013 and Master degree in Chemistry at 2015 from the State University of Londrina. Currently is Ph.D. candidate in Chemistry at University of Campinas with scientific work acting in the development of surface-enhanced Raman scattering (SERS) platforms by the synthesis of metallic nanoparticles, surface modification of paper substrates and inkjet-printing technology.

References (78)

  • M. Sun et al.

    Performance enhancement of paper-based SERS chips by shell-isolated nanoparticle-enhanced Raman spectroscopy

    J. Mater. Sci. Technol.

    (2019)
  • A.G. Berger et al.

    Vertical-flow paper SERS system for therapeutic drug monitoring of flucytosine in serum

    Anal. Chim. Acta

    (2017)
  • E.P. Hoppmann et al.

    Highly sensitive and flexible inkjet printed SERS sensors on paper

    Methods

    (2013)
  • A. Eshkeiti et al.

    Detection of heavy metal compounds using a novel inkjet printed surface enhanced Raman spectroscopy (SERS) substrate

    Sens. Actuators B Chem.

    (2012)
  • B.O. Skadtchenko et al.

    Surface-enhanced Raman scattering of p-nitrothiophenol: molecular vibrations of its silver salt and the surface complex formed on silver islands and colloids

    Spectrochim. Acta Part A Mol. Biomol. Spectrosc.

    (2001)
  • A.L. Dendramis et al.

    A surface-enhanced Raman scattering study of CTAB adsorption on copper

    Surf. Sci.

    (1983)
  • S. Milliken et al.

    Self-assembled vertically aligned Au nanorod arrays for surface-enhanced Raman scattering (SERS) detection of Cannabinol

    Spectrochim. Acta Part A Mol. Biomol. Spectrosc.

    (2018)
  • G. Weng et al.

    Preparation and SERS performance of Au NP/paper strips based on inkjet printing and seed mediated growth: the effect of silver ions

    Solid State Commun.

    (2018)
  • J. Langer et al.

    Present and future of surface-enhanced raman scattering

    ACS Nano

    (2020)
  • J.-H. Lee et al.

    Plasmonic nanosnowmen with a conductive junction as highly tunable nanoantenna structures and sensitive, quantitative and multiplexable surface-enhanced raman scattering probes

    Nano Lett.

    (2014)
  • L. Qu et al.

    Silver nanoparticles on cotton swabs for improved surface-enhanced Raman scattering, and its application to the detection of carbaryl

    Microchim. Acta

    (2016)
  • J. Guo et al.

    A filter supported surface-enhanced raman scattering “nose” for point-of-care monitoring of gaseous metabolites of bacteria

    Anal. Chem.

    (2020)
  • A. Haddad et al.

    Detection and quantitation of trace fentanyl in heroin by surface-enhanced Raman spectroscopy

    Anal. Chem.

    (2018)
  • E.C. Le Ru et al.

    Quantifying SERS enhancements

    MRS Bull.

    (2013)
  • Y. Fang et al.

    Measurement of the distribution of site enhancements in surface-enhanced Raman scattering

    Science

    (2008)
  • A. Garcia-Leis et al.

    Silver nanostars with high SERS performance

    J. Phys. Chem. C

    (2013)
  • S. Lin et al.

    Self-assembly of faceted gold nanocrystals for surface-enhanced Raman scattering application

    J. Phys. Chem. C

    (2019)
  • C.-H. Zhang et al.

    Small and sharp triangular silver nanoplates synthesized utilizing tiny triangular nuclei and their excellent SERS activity for selective detection of thiram residue in soil

    ACS Appl. Mater. Interfaces

    (2017)
  • J.-M. Li et al.

    Hollow nanocubes made of Ag–Au alloys for SERS detection with sensitivity of 10 −8 M for melamine

    J. Mater. Chem. C

    (2014)
  • C.-L. Zhang et al.

    Controlled assemblies of gold nanorods in PVA nanofiber matrix as flexible free-standing SERS substrates by electrospinning

    Small

    (2012)
  • D. García-Lojo et al.

    Plasmonic supercrystals

    Accounts Chem. Al Res.

    (2019)
  • T. Lee et al.

    Macroscopic Ag nanostructure array patterns with high-density hotspots for reliable and ultra-sensitive SERS substrates

    Nano Res.

    (2019)
  • T. Vo-Dinh et al.

    Surface-enhanced Raman spectrometry for trace organic analysis

    Anal. Chem.

    (1984)
  • C.D. Tran

    Subnanogram detection of dyes on filter paper by surface-enhanced Raman scattering spectrometry

    Anal. Chem.

    (1984)
  • T. Vo-Dinh et al.

    Surface-enhanced Raman Analysis of Benzo[A]Pyrene-DNA adducts on silver-coated cellulose substrates

    Appl. Spectrosc.

    (1987)
  • D. Das et al.

    Rinse, repeat”: an efficient and reusable SERS and catalytic platform fabricated by controlled deposition of silver nanoparticles on cellulose paper

    ACS Sustain. Chem. Eng.

    (2019)
  • F. Zeng et al.

    Paper-based versatile surface-enhanced raman spectroscopy chip with smartphone-based raman analyzer for point-of-care application

    Anal. Chem.

    (2019)
  • G. Zheng et al.

    Gold nanoparticle-loaded filter paper: a recyclable dip-catalyst for real-time reaction monitoring by surface enhanced Raman scattering

    Chem. Commun.

    (2015)
  • L. Qu et al.

    Batch Fabrication of Disposable Screen Printed SERS Arrays

    (2012)
  • Cited by (34)

    • ZnO and TiO<inf>2</inf> nanostructures for surface-enhanced Raman scattering-based bio-sensing: A review

      2022, Sensing and Bio-Sensing Research
      Citation Excerpt :

      Traditionally, plasmonic materials, such as gold (Au) and silver (Ag), copper (Cu), are used as substrates due to their high electromagnetic enhancement originating from localized surface plasmon resonance (LSPR) [2]. These materials can be synthesized into different shapes and forms, such as colloids [3], nanospheres [4], nanowires [5], nanorods [6], and nanoplates [7] to optimize their efficiency and can reach enhancement levels of 1015. However, issues related to substrate uniformity, instability, and plasmonic blinking (all of which affect reproducibility), as well as manufacturing costs, limitations with respect to biocompatibility, and localized heating still arise in these systems.

    View all citing articles on Scopus

    Naiara V. Godoy obtained Bachelor degree in Chemistry in 2013 and Master degree in Chemistry at 2015 from the State University of Londrina. Currently is Ph.D. candidate in Chemistry at University of Campinas with scientific work acting in the development of surface-enhanced Raman scattering (SERS) platforms by the synthesis of metallic nanoparticles, surface modification of paper substrates and inkjet-printing technology.

    Daniel García-Lojo is a Ph.D. candidate under the supervision of Jorge Pérez-Juste and Isabel Pastoriza-Santos at the Biomedical Research Center at the University of Vigo. His research is focused on self-assembly of plasmonic nanoparticles.

    Fernando A. Sigoli is associate professor in the Department of Inorganic Chemistry of Institute of Chemistry at UNICAMP (Brazil). He received his Ph.D. in Inorganic Chemistry (2001) from UNESP and worked in a USA-based Optical Sensors Company (California) as a researcher, manager and finally as R&D director from 2001 to 2004. Dr. Sigoli was post-doctorate fellow from December 2004 to August 2006 at UNESP. He is member of the Laboratory of Functional Materials Group since 2006 and Laboratory for Advanced Optical Spectroscopy since 2011. Currently Dr. Sigoli is interested in photophysical properties of Lanthanide ions applied on gas and temperature optical probes and theranostic materials. ORCID: 0000-0003-1285-6765

    Jorge Pérez-Juste has a Ph.D. from the University of Vigo (1999). He is currently an Associate Professor at the Biomedical Research Center at University of Vigo. His research is focussed on the synthesis and characterizationof metal nanoparticles as well as the understanding of the mechanisms involved in nanoparticle growth, which determine the final size and shape. Besides, he is interested in the application of the nanoparticles for (photo)catalysis. ORCID: 0000-0002-4614-1699

    Isabel Pastoriza-Santos has a Ph.D. from the University of Vigo (2001). She is currently an Associate Professor at the Biomedical Research Center at the University of Vigo. Her research involves the synthesis, surface modification and assembly of the nanoparticle with size and shape control and therefore with desired optical properties. Furthermore, her research is also focused on the fabrication of plasmonic platforms for sensing based on LSPR and SERS. ORCID: 0000-0002-1091-1364

    Italo Odone Mazali is Associate Professor in the Department of Inorganic Chemistry of Institute of Chemistry at University of Campinas (UNICAMP, Brazil). He received the Ph.D. in Sciences (2001) at UNICAMP. He is member of the Laboratory of Functional Materials Group (since 2006) and Laboratory for Advanced Optical Spectroscopy (since 2011) and is currently interested in advanced functional nanostructured materials and highly-sensitive surface-enhanced Raman spectroscopy (SERS)-based chemical sensor using metallic nanoparticles as SERS substrate. ORCID: 0000-0001-5698-5273

    View full text