ATR-FTIR and SEIRA Measurements

Before SEIRA measurements, each peptide (30 μL of an aqueous peptide solution) was immobilized on colloidal suspension (10 μL). The mixture peptide/colloidal nanoparticles were then deposited on a diamond ATR adapter and allowed to dry. Unbound peptide molecules were removed through washing with deionized water and allowed to dry. The process was repeated three times.

The spectra were recorded on an FTIR Thermo Scientific Nicolet 6700 spectrometer equipped with a diamond ATR accessory. Measurement conditions were the following: a resolution of 4 cm^–1 and 128 scans. SEIRA spectra were recorded three times at three different locations on each substrate surface. The SEIRA spectra of a given adsorbate on a given substrate were almost identical except for small differences (up to 5%) in some band intensities. No spectral changes that could be associated with the decomposition of the sample were observed during these measurements.