The phosphate glass with composition of 45P2O5-20Na2O-5K2O-10Ag2O-2Nb2O5-2B2O3-5ZnO-1ZrO2 and contains 10 mol% of Ag2O was synthesized in silica crucible at approximately 1,500°C. Island films were formed on the polished glass surface in the course of thermal processing in hydrogen atmosphere at 200°C. The hydrogen was produced by water electrolysis. The morphology of the manufactured MIF was characterized using Dimension 3100 (Veeco Instruments, Inc., Plainview, NY, USA) atomic force microscope (AFM) using probes with curvature radii below 10 nm.
In order to perform the SERS experiments, we deposited 10-μL drop of R6G aqueous solution on the substrate. After drying at room temperature, it formed a film spot with diameter of about 3 mm. The concentration of R6G in the solutions and surface concentration of the created R6G films are listed in Table . Note that the average surface concentration of R6G which is equal to 6 × 1012 cm−2 corresponds to 0.06 of the monolayer.
Samples for SERS experiments
Optical absorption spectra of the deposited R6G films were measured with UV–Vis Specord 50 spectrometer (Analytik Jena AG, Jena, Germany). Raman spectra at the excitation wavelength of 514.5 nm were obtained in backscattering geometry using Renishaw spectrometer (Renishaw PLC, Wotton-under-Edge, Gloucestershire, UK) with Raman microscope and charge coupled device detector. In the Raman measurements, the excitation power at the sample was equal to 700 μW, the diameter of the laser beam at the sample was approximately 10 μm, and the signal accumulation time was 10 s. Since the excitation wavelength coincides with the electron resonance transition in R6G molecule, hereafter, we will refer to this process as the surface enhanced resonant Raman spectroscopy (SERRS) [1
] to emphasize the resonant enhancement of the measured SERS signal. The measurements were performed at room temperature 6 days after the films deposition.