In recent years, surface-enhanced Raman scattering (SERS) of a molecule/metal–semiconductor hybrid system has attracted considerable interest and regarded as the synergetic contribution of the electromagnetic and chemical enhancements from the incorporation of noble metal into semiconductor nanomaterials. However, the underlying mechanism is still to be revealed in detail. Herein, we report an irreversible accumulated SERS behavior induced by near-infrared (NIR) light irradiating on a 4-mercaptobenzoic acid linked with silver and silver-doped titanium dioxide (4MBA/Ag/Ag-doped TiO₂) hybrid system. With increasing irradiation time, the SERS intensity of 4MBA shows an irreversible exponential increase, and the Raman signal of the Ag/Ag-doped TiO₂ substrate displays an exponential decrease. A microscopic understanding of the time-dependent SERS behavior is derived based on the microanalysis of the Ag/Ag-doped TiO₂ nanostructure and the molecular dynamics, which is attributed to three factors: (1) higher crystallinity of Ag/Ag-doped TiO₂ substrate; (2) photo-induced charge transfer; (3) charge-induced molecular reorientation.

The determination of styrene-butadiene-styrene (SBS) content in SBS-modified asphalt (SBSMA) is crucial in road quality control. In this study, a polystyrene (PS)-based index, which is an alternative indicator for the current polybutadiene (PB)-based index of SBS content determination in specification based on the Fourier transform infrared spectroscopy test, was proposed to provide a more accurate measurement. The influences of the types of base asphalt/SBS modifiers/solvents, sulfur stabilizers, and aging on SBS content determination were investigated based on both of the two indices. The results show that the PS-based index has higher accuracy and is recommended as the indicator in the content determination. The selections of the types of the base asphalt/SBS when preparing the calibration samples should correspond to those of the testing samples to avoid the measurement deviation. Trichloroethylene solvent has an interference influence on the characteristic peak of PB in SBSMA. The sulfur and aging both have a double-sided effect on the SBS content determination. Furthermore, the fluorescence microscopy test and the four-component test were conducted to correlate the compatibility of asphalt with SBS and the stability of the asphalt colloidal structure. The gel permeation chromatography test was also used to verify the influence of aging on the SBS content determination.