Luminescence characteristics and room temperature phosphorescence of naphthoic acids in polymers

In the present work we have investigated the luminescence properties of 1-naphthoic acid (1NA) and 2-naphthoic acid (2NA) in three polymeric systems viz. poly methyl methacrylate (PMMA), poly vinyl alcohol (PVA) and cellulose acetate (CA). In case of PVA, strong room temperature phosphorescence (RTP) besides fluorescence is also noticed whereas in PMMA, weak phosphorescence is observed only after nitrogen purging and in CA it is practically not observed. Moreover, oxygen quenches the RTP in PVA significantly. Study reveals that in case of 1 NA in PVA, two types of species – strongly hydrogen bonded as well as weakly hydrogen bonded should exist. However, in PMMA and CA only weakly hydrogen bonded species appear to be present. On the other hand in case of 2NA we could not find such type of behaviour. The difference in the behaviour of these two probes is discussed. ► Luminescence properties of 1-naphthoic acid (1NA) and 2-naphthoic acid (2NA) in three polymeric systems are studied. ► In case of PVA, in 1NA strong room temperature phosphorescence (RTP) is also noticed. ► In case of 1 NA in PVA, two types of species – strongly hydrogen bonded as well as weakly hydrogen bonded should exist.