Peethan, Alina and Aravind, M and Unnikrishnan, VK and Chidangil, Santhosh and George, Sajan D (2022) Facile fabrication of plasmonic wettability contrast paper surface for droplet array-based SERS sensing. Applied Surface Science, 571. pp. 1-8. ISSN 0169-4332

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Abstract

A facile and cost-effective method was developed to create superhydrophobic surfaces onto a superhydrophilic commercial paper for the application of droplet splitting of microliter droplets into nano and sub-nano-liter droplets. The high wettability contrast of nearly 180◦ between the superhydrophobic region created via candle soot coated onto the patterned poly (dimethylsiloxane) and the paper causes the self-partitioning of a 1 µl droplet while sliding through the surface with a speed ranging from 0.001 to 7.3 mm/s. Additionally, the splitting of the droplet demonstrated for µl droplets of surface tension ranging from 72 mN/m to 38.5 mN/m. The plasmonic droplet assay for surface-enhanced Raman spectroscopy was fabricated via in-situ reduction of Ag nanoparticles onto the superhydrophilic region. The Raman scattering studies of methyl orange using the prepared substrates exhibit a limit of detection of 670 pM. Further, by using methyl orange as a probe molecule,selective detection of Hg2+ ions up to a concentration of 100 pM in nanoliter droplet volume is demonstrated. It is envisaged that these cost-effective plasmonic nanoliter droplet assays created via patterned superhydrophilicsuperhydrophobic can find applications in high throughput screening, microfluidic bioassays, medical diagnosis

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