Chemically reduced and laser-ablated gold nanoparticles immobilized to silanized glass plates: Preparation, characterization and SERS spectral testing

SERS-active surfaces based on gold colloidal nanoparticles attached to silanized glass plates were prepared and characterized by surface plasmon extinction (SPE) and atomic force microscopy (AFM). Aminopropyltrimethoxysilane (APTMS) was found to be more efficient in the silanization process than mercaptopropyltrimethoxysilane (MPTMS). Gold colloidal nanoparticles prepared by three different procedures, i.e. laser-ablation and chemical reduction of HAuCl4 by sodium borohydride or by sodium citrate, were immobilized to glass plates using APTMS. The laser-ablated colloids exhibited poor stability during deposition and could not be used for routine preparation of surfaces. Drying at 100 °C after immobilization of chemically reduced nanoparticles stabilizes morphological properties of the surface and thus significantly improves the preparation procedure. Reproducibility and stability of substrates were tested by measurement of SERRS spectra of 5,10,15,20-tetrakis(1-methyl-4-pyridyl)porphyrin (TMPyP). Spectra measured from different spots of a sample showed excellent reproducibility and proved high homogeneity of the Au surface. Measurement of several days aged samples revealed very good stability of the SERRS signal in time.