Effects of hydrostatic pressure on the excitation-emission matrix (EEM) of a series of pure PAHs

The effects of hydrostatic pressure on the EEM of a series of pure PAHs (naphthalene, fluorene, phenanthrene, acenaphthene, fluoranthene, and anthracene) with three different concentrations (10-6 mol L-1, 10-5 mol L-1, and 10-4 mol L-1) were investigated in a pressure range from 0.1 MPa to 60 MPa at room temperature. According to the EEM, 2 (naphthalene) to 12 (anthracene) fluorescence peaks were observed and the variation of EEM under high pressure were revealed by analyzing the fluorescence peaks positions and intensities with the increased hydrostatic pressure. It is found that fluorescence peak shifts were not detected in the compression, however, both the enhancement of intensity (e.g. naphthalene, 10-6 mol L-1, peak of 225/330 nm, relative fluorescence intensity increased by 0.594) and reduction of intensity (e.g. fluorene, 10-6 mol L-1, peak of 275/309 nm, relative fluorescence intensity decreased by 0.0966) were observed. Otherwise, the pressure effects were magnified when the concentration was increased (e.g. the relative fluorescence intensity of anthracene (peak of 380/425 nm) increased by 0.0165 (10-6 mol L-1) and decreased by 0.479 (10-6 mol L-1) when the pressure was elevated from 0.1 MPa to 60 MPa).