Fluorescence detected linear dichroism of small molecules oriented on polyethylene film.

We have previously reported a novel method for measuring the spectral properties and orientation of fluorescent probes in solution, which we denoted fluorescence-detected linear dichroism (FDLD). In this work, we expand the scope of the technique by recording the FDLD spectra of the small organic fluorophores: anthracene, 4',6-diamidino-2-phenylindole (DAPI), 1,6-diphenylhexatriene (DPH), and 4-methylphenyl benzoate (MPB), oriented on stretched oxidised polyethylene film. Much like what was observed in solution, we found that the FDLD produced a large signal enhancement compared with absorbance LD, which lowers the sample requirement for measurement. We also found that FDLD has an increased sensitivity towards the immediate environment of the chromophore, revealing oligomeric structures on the film. We believe that FDLD has the potential to reveal important properties of molecules that are obscured or unattainable when using other methods.