The interparticle gap manipulation of Au-Ag nanoparticle arrays deposited on flexible and atmospheric plasma-treated PDMS substrate for SERS detection

Abstract

Au-Ag nanoparticle arrays were deposited on a flexible and surface-modified polydimethylsiloxane (PDMS) substrate for surface-enhanced Raman scattering (SERS). The surface of the PDMS substrate was modified to be a hydrophilic layer by nitrogen (N2) atmospheric plasma treatment. When compared to the non-plasma-treated PDMS substrate, the contact angle of the plasma-treated PDMS substrate decreased from 115.4° to 32° to form the hydrophilic surface of the PDMS substrate. The uniform Au-Ag nanoparticle arrays were further deposited by thermal evaporation on the plasma-treated PDMS substrate that was evaluated by scanning electron microscopy (SEM). The results indicate that the Au-Ag@PDMS-N2 substrate exhibited highly sensitive and reproducible SERS spectra of adenine (10−4 M) due to the homogeneous and narrow interparticle gap (~2 nm) between Au-Ag nanoparticles. Particularly, the SERS intensity of 2Au-6Ag@PDMS-N2 substrate increased ~4 times under a bending angle of 5°. This indicated that the flexible behaviors of the PDMS-based SERS substrate can effectively manipulate the interparticle gap between Au-Ag nanoparticles by bending the SERS substrate. Therefore, the flexible and ultrasensitive SERS substrate fabricated by Au-Ag nanoparticles deposited on plasma-treated PDMS substrate provides enormous potential for practical applications in detecting biomolecules and environmental pollutants.