Photophysical studies of N-phenylanthranilic acid in polymer films

Photophysical properties of bifunctional N-phenylanthranilic acid (NPAA) have been studied as a dopant in polystyrene (PS) films. The PS fllms .:ontaining fluorescent NPAA were prepared from the solutions in non-polar and polar solvents. The fluorescence spectra of PS films prepared by using non-polar solvents depend on the concentration of NPAA in the film. The films containing lower concentration have exhibited sharp emission band at 412 nm corresponding to normal emission while the films containing higher concentration of NPAA have shown broad emission band peaking at 466 nm. The broad emission band is attributed to as arising due to formation of dimeric species by hydrogen bonding between two neighbouring NPAA molecules in the films. The modification observed in the fluorescence excitation and absorption spectra of the films with dopant concentration allows to consider the interaction between dopant molecules. In case of NPAA doped poly(vinyl acetate) fllms, there is an evidence for the destabilization of dimeric species as the fluorescence corresponds to the normal emission only. Thin film flu orescent systems parti cul arl y emitting in blue spectral region are of interes t fo r use in optoelectro nic devices, such as tunabl e lasers, optical fib ers, switches, organi c electroluminescent devices and in hi gh energy radi ation detectors 1 4 • Thin polymer films containing fluorescent materi als have many advantages fr om both technical and cost poin t of vi ew. There is a renewed interest in doped polymer matrices in curre nt years by using usual flu orescent pyrene and similar classes of dopant materi als forming excimers at hi gh concentrati on 5 - 8 . The organic bifuncti onal molecul es contatntng both hydrogen atom donor (e.g . -OH, -NH2, etc.) and acceptor (=N, >C=O, etc.) groups in close proximity, generall y form taut omers by intra and intermolecular hydrogen bonding when placed in hydrocarbon solve nts