Study On The Fluorescence Sensors Based On Perylenetetracarboxylic Diimide

The development of luminescent devices is an active field of research in supramolecular chemistry. An important area within this field is the development of fluorescent molecular sensors. Such sensors have the advantage of possessing high sensitivity and selectivity, as well as providing on-line and real-time analysis that has revolutionized the field of chemical analysis, particularly in critical care analysis of blood and serum samples and quantitative analysis of the contamination in environment.A new fluorescent sensor PDICd was developed from perylenetetracarboxylic dianhydride with a high yield of 100%. It displayed high selectivity and sensitivity to Cd2+ and could effectively distinguish Cd2+ from Zn2+ and other mental ions with a detection limit of 2×10-8 M. The fluorescence intensity at 541 nm significantly enhanced by 33-fold after chelating with Cd2+. Gratifyingly, the fluorescence emission was extraordinarily pH-independent with pka as low as 1.9 which is hardly obtained in the chemosensors based on DPA. The structure of PDICd and other reported sensors were calculated in order to further explore the reason for low pKa of PDICd. It was concluded from the calculation that when the mulliken charge difference between amine nitrogen and pyridine nitrogen was negative, the sensor would display a higher pKa, or, it would display smaller pKa. This factor would provide an important basis for the design of fluorescent sensors with different pKa.A novel perylene dimerization-based molecular beacon PDIMB was developed. The cyanoethyl phosphoramidites of PDIs were obtained and the oligonucleotides were synthesized on an Applied Biosystems 394 DNA synthesizer. Obviously, this format provided an easier one-step synthesis/purification protocol compared to the tedious and costly synthesis of regular MBs using a fluorescent dye and quenching moiety, which requires a two-step conjugation process with purification at each step. Most importantly, PDIMB could narrow the distance between the two fluorophores and then reduce background fluorescence. Gratifyingly, fluorescence intensity enhanced significantly when this molecular beacon hybridized to its target template. Thus, a new method would be added to the synthesis of molecular beacons.