An internal reference fluorescent pH sensor with two pH-sensitive fluorophores carrier

This paper describes an internal reference fluorescent sensor for pH determination. The fluorescent carrier contained two pH-dependent fluorophores, 2-allyl-6-((2-aminoethyl)amino)-1H-benzo[de]isoquinoline-1,3(2H)-dione (AAEAN) and meso-5,10,15,20-tetra-(4-aminophenyl)porphyrin (TAPP), that were derived from naphthalimide derivatives and porphyrin derivatives respectively. The two fluorophores acted as reference fluorophores for each other. The fluorescent carrier was copolymerized with acrylamide, (2-hydroxyethyl)methacrylate and triethylene glycol dimethacrylate on the silanized glass surface for an internal reference pH sensor. The sensor showed satisfactory selectivity, reproducibility as well as sufficient stability and fast response time. It covered a broad dynamic range of pH value 1.00-9.50. The sensor provided an alternative concept to apply the fluorescence carrier with two fluorophores for the development of internal reference sensors covering a broad range of pH value. The synthesis of one fluorescent carrier, with two properly selected fluorophores paved the way to construct a series of internal reference sensors.