Towards the reproducible fabrication of homogeneous SERS substrates by Langmuir-Schaefer technique: A low cost and scalable approach for practical SERS based sensing applications

The development of homogeneous, endurable and low cost SERS (Surface Enhancement Raman Spectroscopy) substrates is becoming of outmost importance due to growing interest in SERS technique for analytical applications. Here, we use the Langmuir-Schaefer technique to produce, as demonstrated by Atomic Force Microscopy and Scanning Electron Microscopy, homogeneous tightly-packed films of 27 nm in diameter octadecylthiolate capped gold nanoparticles in a reproducible and simple manner. The fabricated Au-based SERS substrates result in an analytical enhancement factor (AEF) of 4.3 × 108 and enable the detection of Rhodamine 6G in a 10−11 M aqueous solution, with remarkable spatial uniformity of the SERS response over a scanned area of 0.4 cm2. In addition, the developed procedure is highly reproducible from batch to batch with a standard deviation below 10% in the SERS signal. Finally, these substrates exhibit durable SERS properties, i.e. experimentally validated 16 months after its fabrication.
P.C. and S.R-R. are grateful for financial assistance from DGA/Fondos FEDER (construyendo Europa desde Aragón) for funding PLATON (E31_17R) research group. M.P.P., R.M. and M.L. are grateful for financial support from MICINN (CTQ2013-49068-C2-1-R and CTQ2016-79419-R).