We studied the picosecond time-resolved fluorescent spectroscopy of 1-anilino-8-naphthalene sulfonate (ANS), which binds to the staphylococcal nuclease (SNase) of the wild-type (WT) and the molten globule (MG) state. Three ANS emission bands at approximately 530nm, approximately 495nm, and approximately 475nm are resolved, corresponding to three ANS states: the free ANS in solution and associated form adsorbing to surface sites and binding to active sites. The surface hydrophobicity of the WT is moderate and different from the MG state, as shown both in the position of the bands and by the concentration dependent ANS fluorescent decay. For MG, the decay of two blue bands accelerated with the increment of the ANS concentration, whereas the WT did not show this dependency. However, when pdTp, an inhibitor, was attached to the active site of the MG state, band 2 decay was also independent of the ANS concentration. These results indicate that the protein hydrophobic sites have two types of interactions with ANS.

In high performance perovskite based solar cells, CH3NH3PbI3 is the key material. We carried out a study on charge diffusion in spin-coated CH3NH3PbI3 perovskite thin film by transient fluorescent spectroscopy. A thickness-dependent fluorescent lifetime was found. By coating the film with an electron or hole transfer layer, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) or 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) respectively, we observed the charge transfer directly through the fluorescence quenching. One-dimensional diffusion model was applied to obtain long charge diffusion distances in thick films, which is ~1.7 mum for electrons and up to ~6.3 mum for holes. Short diffusion distance of few hundreds of nanosecond was also observed in thin films. This thickness dependent charge diffusion explained the formerly reported short charge diffusion distance (~100 nm) in films and resolved its confliction to thick working layer (300-500 nm) in real devices. This study presents direct support to the high performance perovskite solar cells and will benefit the devices' design.