abstract
Hydrophobic substrates for surface-enhanced Raman scattering (SERS) of adsorbate species are of great interest in chemical analysis because they can concentrate the analyte molecules in a small area of the surface, thereby improving the SERS sensitivity. Here, we propose a general strategy to fabricate hydrophobic paper-based substrates for SERS applications. The paper substrates have been manufactured by inkjet printing of aqueous emulsions containing Ag and polystyrene (PS) colloidal nanoparticles. In a first stage, the SERS performance of the substrates was optimized by varying the relative amounts of polymer/metal colloidal nanoparticles, the number of printing layers, and the degree of hydrophobicity of the substrates, using crystal violet as a molecular probe, which is well known for its strong SERS activity. In these conditions, the strongest surface Raman enhancement was observed for the highest water contact angle (146 degrees) achieved. The selected Ag/PS-coated paper substrates showed wide applicability for several analytes, but in this study, a detailed analysis is provided for the pesticide thiram as a proof of concept. Several samples spiked with thiram have been analyzed by SERS, giving a detection limit of 0.024 ppm thiram in mineral water and apple juice, while in apple peel, the detection limit achieved for the same pesticide was 600 ng/cm(2). We suggest that this one-step fabrication method produces a hydrophobic coating whose nanoscale features improve the SERS performance of the paper substrates.
keywords
FILTER-PAPER; SILVER-NANOPARTICLES; SERS PLATFORM; PESTICIDES; NANOSTRUCTURES; SPECTROSCOPY; NANOSTARS; RESIDUES; SENSORS; FRUIT
subject category
Nanoscience & Nanotechnology; Materials Science, Multidisciplinary
authors
Martins, NCT; Fateixa, S; Fernandes, T; Nogueira, HIS; Trindade, T
our authors
Helena Isabel Seguro Nogueira
Assistant Professor with Aggregation
João Tiago Moniz Fernandes
PhD Student
Natércia da Conceição Tomé Martins
Junior Researcher
Sara Fateixa
Post-Doc Fellowship
Tito Trindade
Full professoracknowledgements
This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. N.C.T.M. and S.F. are funded by National funds (OE), through FCT-Fundacao para a Ciencia e Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by the law 57/2017, of July 19. T.F. thanks Fundacao para a Ciencia e Tecnologia (FCT) for the PhD grant SFRH/BD/130934/2017.