Non-invasive fluorescence switch in polymer films based on spiropyran-photoacid modified TPE

Abstract

Non-invasive fluorescent molecular switch is very challenging to achieve in solid state. Here, a new multi-stimulus-responsive fluorescent molecular switch of SPPATPE was prepared by linking spiropyran-photoacid (SPPA) with tetraphenylethene (TPE). The isomerization of SPPATPE can be triggered with either visible light/dark or acid/base in solution. Both ring-closed form (RCF) and ring-open form (ROF) of SPPATPE exhibit aggregation-induced emission (AIE). The RCF SPPATPE aggregates give out a cyan emission, which is assigned as the local excited emission of TPE moiety, while ROF SPPATPE have two forms of aggregation states, which give out two red emissions from intramolecular charge transfer. By selecting a suitable polymer of polyvinyl pyrrolidone (PVP) as the matrix, which gives the molecules a moderate alkaline environment, SPPATPE can exhibit non-invasive light/heat responsive emission switch in the polymer thin film with both good waterproofness and good processibility, which makes this kind of hybrid material potentially applicable in photo sensing, rewritable display, etc.