Pyrene is a polycyclic aromatic hydrocarbon with fluorescence in the 370–400 nm range. The optical properties of pyrene deposited on different substrates were investigated from experimental and theoretical points of view. In contrast to prior studies of surface-enhanced fluorescence, in this work, all substrates were semiconductors or insulators. Experimentally, the intensities of photoluminescence (PL) and PL excitation (PLE) spectra were investigated. The PLE spectra of pyrene’s monomer emission show that the intensities of the two main absorption peaks vary according to the chosen substrate. Calculations for pyrene on zinc sulfide (ZnS) and surface-oxidized diamond suggest that this connection arises from the alignment of the pyrene electronic levels relative to the band edges of the substrate. The absorption peak at 272 nm (4.56 eV) is shown to depend on the HOMO-1→LUMO orbital contribution, whereas the 335 nm (3.70 eV) peak depends upon the HOMO→LUMO transition. When the HOMO-1 level falls inside the substrate valence band, as in the case of ZnS, there is significant hybridization of the molecular state with surface states that causes an enhancement of the 272 nm peak. For pyrene on diamond, however, the HOMO-1 level falls in the substrate bandgap, leading to negligible hybridization and thus no enhancement.

中文翻译：

---

P发光激发的表面效应

P是一种多环芳烃，其荧光范围在370-400 nm之间。从实验和理论的角度研究了deposited沉积在不同衬底上的光学性质。与先前对表面增强荧光的研究相反，在这项工作中，所有基板都是半导体或绝缘体。实验上，研究了光致发光（PL）和PL激发（PLE）光谱的强度。pyr单体发射的PLE光谱表明，两个主要吸收峰的强度根据所选底物而变化。对硫化锌（ZnS）和表面氧化的金刚石上的pyr的计算表明，这种连接是由于the电子能级相对于基底带边缘的对准而产生的。272 nm处的吸收峰（4。56 eV）取决于HOMO-1→LUMO轨道贡献，而335 nm（3.70 eV）峰取决于HOMO→LUMO跃迁。如ZnS那样，当HOMO-1水平落在底价带之内时，分子状态与表面状态之间就会发生明显的杂化，从而导致272 nm峰的增强。然而，对于金刚石上的pyr，HOMO-1水平在底物带隙中下降，导致杂交可忽略不计，因此没有增强。