Silver-coated nanostructured boehmite surfaces as substrates for Surface Enhanced Raman Spectroscopy

Silver-coated nanostructured boehmite surfaces as substrates for Surface Enhanced Raman Spectroscopy A. Dimitriou1, S. Richardson1, G. Geka2, A. Kanioura2, F. Kalogeropoulou2, M Angelopoulou2, D. Tsounidi3, I. Raptis3, S. Kakabakos2, P. Petrou2and N. Papanikolaou1 1Institute of Nanoscience & Nanotechnology, and 2Immunoassays/Immunosensors Lab, Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, NCSR “Demokritos”, Aghia Paraskevi, Greece 3ThetaMetrisis, S.A., 12132, Athens, Greece Acknowlegement This research has been financed from the European Union’s Horizon Europe programme under grant agreement No 101168416 (ARMADILLO). References 1. D. Cialla-May, A. Bonifacio, A. Markin, N. Markina, S. Fornasaro, A. Dwivedi, T. Dib, E. Farnesi, C. Liu, A. Ghosh, M. Schmitt, J. Popp, TrAC Trend Anal. Chem. 181 117990 (2024) 2. A. Dimitriou, A.S. Kastania, P. Sarkiris, V. Shvalya, N. Papanikolaou, U. Cvelbar, E. Gogolides, Micro Nano Eng. 24 100279 (2024) INTRODUCTION Metallic nanostructured surfaces significantly enhance the intensity of Raman signal arising from molecules immobilized on them [1]. This detection approach that is known as Surface Enhanced Raman Spectroscopy (SERS) has expanded the application areas of Raman spectroscopy to biosensing due to minimal interferences from the sample matrix. To take full advantage of SERS for biosensing, substrates offering high enhancement factor along with uniformity over a large area and facile and reproducible fabrication are required. In the current work, silicon surfaces were first covered with an aluminum layer and then subjected to thermal treatment at aqueous environment to partially oxidize the aluminum layer creating a boehmite nanostructures on top of which silver is deposited by sputtering to create the SERS substrates [2]. Preparation of SERS substrates SEM characterization of SERS substrates Evaluation of SERS substrates Rhodamine 6G Uric acid 600 800 1000 1200 1400 1600 0 1000 2000 3000 4000 5000 Intensity (a.u.) Raman shift (cm-1) 40 nm 60 nm 80 nm 100 nm 120 nm 020 40 60 80 100 120 0 1000 2000 3000 4000 5000 Intensity (a.u.) Ag Thickness (nm) 020 40 60 80 100 120 0 1000 2000 3000 4000 5000 6000 Intensity (a.u.) Ag Thickness (nm) CONCLUSIONS •Using boehmite substrates covered with 80-nm thick silver layer enhancement factors over 107were achieved for Rhodamine 6G, whereas for uric acid substrates with a 40-nm Ag layer provided the higher enhancement factor. •The achieved enhancement factors were significantly higher compared to those obtained by commercial substrates. Renishaw inVia Confocal Raman microscope ×20 objective lens Laser 785 nm, 10 mW 1 s acquisition time 30 measurements/sample 5-μL solution left to dry Raman spectra of 10-6 M Rhodamine 6G aqueous solution Peak intensity at 1650 cm-1 for Rhodamine 6G (left) and at 1130 cm-1 for uric acid (right) vs. Ag layer thickness. Boehmtie Silmeco_Ag Silmeco_Au Sersitive Metroohm 0E+00 1E+07 2E+07 3E+07 4E+07 5E+07 6E+07 Enhancement factor Rhodamine 6G Uric acid Raman signal enhancement vs. commercial substrates