Au Photonic Crystals for High-Sensitivity SERS Molecular Sensing

ROA DÍAZ, SIMÓN; REDONDO, CAROLINA; AKINOGLU, GOEKALP ENGIN; MORALES, RAFAEL; PEDANO, MARÍA LAURA; SIRENA, MARTÍN; MAGUREGUI, MAITE

Pucón

Congreso; VII Congreso Nacional de Nanotecnología; 2023

Universidad Austral de Chile

Noble metal-based Photonic Crystals (PCs) have emerged as outstanding candidates for precise light management, projecting applications in strategic areas for society like high-sensitivity and fast molecular (inorganic/organic/bio) sensing by Surface-Enhanced Raman Spectroscopy (SERS). In this work, we report a brief but exhaustive study on the gross potential of large-scale Au nanodisks-based 2D PCs fabricated by Interference Laser Lithography (ILL) for efficient SERS-based molecular sensing. This technique was used to fabricate periodic nanoarrays (period of 470 [nm]) of Au nanodisks with thicknesses from 50 up to 125 [nm]. The period was chosen following FDTD simulations that suggest the best electric-near field enhancement for this condition. Confocal Raman microscopy and methylene blue (as Raman marker) were used to assess the samples' performance for molecular sensing using 633 and 780 [nm] laser sources. SERS studies show the nanodisks' thicknesses are a relevant tunning factor for the Raman signal amplification, observing higher signal enhancements for higher thicknesses. Results show the best performance for 633 [nm]-laser, which enables measuring the characteristic Raman footprint with good spectral resolution using relatively low powers (0.04 – 1 [mW]) and acquisition times (1 – 30 [s]). The observed thickness and excitation wavelength effects on the Raman signal enhancement were consistent with FDTD simulations, which predict higher electric-near field amplifications for higher thickness and shorter wavelengths within the red/near-infrared range. This research demonstrates the potential of our PCs fabricated using an efficient large-scale and low-cost lithography technique, concerning ion or electron beam-based ones, for fast and high spectral resolution SERS-based molecular sensing.