Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 73: Poster Metal and Semiconductor Substrates: Adsorption and Reactions of Small Molecules

O 73.6: Poster

Wednesday, March 19, 2025, 18:00–20:00, P2

Surface Charge Modification of Silver Substrates for Enhanced SERS Selectivity — •Georgiana Ion, Stefania Dana Iancu, and Nicolae Leopold — Faculty of Physics, Babes-Bolyai University, 400084, Cluj-Napoca, Romania

Surface-enhanced Raman spectroscopy (SERS) uses the plasmonic properties of metallic nanoparticles for sensitive detection in complex matrices. A key challenge is controlling the detection of specific species. This study developed solid-state SERS substrates with optimized surface properties for selective detection of anionic and cationic analytes.

Citrate-capped silver nanoparticles (cit-AgNPs) were synthesized via the Lee-Meisel method, while hydroxylamine-reduced silver nanoparticles (hya-AgNPs) followed the Leopold-Lendl method. Concentrated nanoparticles were dried into 2 µL droplets on cover glass to create solid substrates. Raman spectra were obtained by immersing the substrates in 2 mL analyte solutions (Nile Blue, Crystal Violet, fumaric acid) using a 532 nm laser.

We found that adding Ca(NO₃)₂ only impacts selectivity when added to the colloidal form before drying, making it crucial for developing both substrate types. This optimized cit-AgNPs for anionic detection, while hya-AgNPs, covered with Cl⁻ ions, selectively detected cationic analytes. Cationic detection can also occur on cit-AgNPs by adding NaCl to the solution. This work highlights how surface modifications enhance SERS substrate selectivity and provide a pathway for tailored systems for specific analyte detection in complex environments.

Keywords: Silver nanoparticles; Surface-Enhanced Raman Spectroscopy (SERS); Selective substrate; Anionic and cationic detection; Surface chemistry tuning