| Amino acids are small organic molecules that contain both amino and carboxyl groups,and are indispensable precursors for synthesis of neurotransmitters,providing the needed energy for human body and brain activities.Amino acids are the basic units of proteins.When the human body lacks some amino acids,the normal operation of the body metabolism will be affected,leading to diseases.For example,the deviation of cysteine contents from normal levels can lead to liver damage,alzheime,parkinson and breast cancer.Presesntly,many methods have been developed for detection of cysteine,such as high-performance liquid chromatography,atomic absorption spectrometry,surface-enhanced Raman spectroscopy,ultraviolet absorption spectroscopy and electrochemical methods.These methods have good detection results,but needing complexed sample preparation,complicated operation process,poor stability of the sensing platform,and sophisticated instruments.In recent years,the researchers focus on the photonic crystal films being used sensing platform to higly sensitively detect target analyte,in which the target molecules sensitive fluorescence probes are modified or infiltrated to the photonic crystal films and the slow photon effect of the photonic crystal has been utilized to enhance the fluorescence signals.In this dissertation,two kinds of solid films,including opal photonic crystals and inverse opal photonic crystals,have been prepared.The synthesized cysteine-sensitive biphenyl derivative and coumarin derivative fluorescence probes were modified or infiltrated to the photonic crystal films for fabrication of the photonic crystal fluorescence sensing films.The highly selectivitive,sensitive and fast detection of cysteine has been achieved and applied to detect of cysteine in real samples and bioimaing of living cells,providing a new strategy for constrcting cysteine sensors.The main contents are as follows:1.A biphenyl derivative fluorescent probe was designed and synthesized.The inverse opal photonic crystal（IOPC）films were prepared by sacrificial template method.The probe was grafted onto the inverse opal photonic crystal films by chemical modification,achieving a cysteine-sensitive IOPC sensing film.The probe can react with cysteine to generate a product that emits green fluorescence at 510 nm.The photonic crystals whose blue-band edge of the photonic stopband overlaps with the emission peak of the fluorescence product have been chosen.The slow photon effect derived from the photonic crystals can enhance the fluorescence signal to improve the detection sensitivity and the limit of detection（Lo D）was 1.86×10-7mol/L,which is two orders of magnitude lower than that obtained in the solution system(2.39×10-5mol/L).This film can be used as a novel sensing platform to detect cysteine in health products.2.The cysteine-sensitive photonic crystal fluorescence sensing films have been constructed by infiltrating a coumarin derivative fluorescence probe into the voids of opal photonic crystal films prepared by vertical depositon self-assembly.The coumarin derivative undergo ammonolysis with cysteine to produce a fluorescent product that emits green fluorescence at 535 nm.The suitable photonic crystal films were selected and the slow photon effect was used to amplify the fluorescence signal,improving the detection sensitivity.The Lo D of 8.90×10-8mol/L has been achieved,which is one order of magnitude lower than that obtained from the fluorescence sensing film prepared by chemical modification.It demonstrates that the infiltration of probes is more beneficial to obtainging the sensing films with more sensitive detection.3.The IOPC films were prepared by sacrificial template method and the coumarin derivative was infilrtated to obtain cysteine-sensitive IOPC fluorescence sensing films.The the coumarin derivative react with cystein by ammonolysis to form a fluorescence product whose emission peak occurs at～535 nm.The fluorescence can be observed in 30s when the film was exposed to the cysteine solution due to the high specific surface and reaction active sites from the interconnected three-dimensional microporous structure of the IOPC,which is conducive to the fast diffusion of cysteine molecules in the film.By selecting the sutiable photonic crystals to enhance the fluorescence by the slow photon effect of photonic crstals,the detection sensitivity has been improved.The Lo D of 3.23×10-9mol/L has been achieved and a wide linear detection range of 1×10-7-1×10-3mol/L has also been obtained.The Lo D is one and two orders of magnitude lower than that from the opal photonic crystal(8.90×10-8mol/L)and solution system(3.88×10-7mol/L),respectively.The results showed that the coumarin derivative-infiltrated IOPC films ccan be used to detect cysteine with high selectivity,sensitivity and fast response.The fluorescent sensing film has been successfully used to detect the cysteine in human serum and realize the bioimaging of living cells.In conclusion,in this dissertation,the photonic crystals were used as sensing platform.The response of cysteine toward the photonic crystals fluorescence sensing films prepared by chemical modification and physical infiltration was studied.The results showed that the constructed sensing films can realize accurate detection of cysteine,and have been successfully applied in the detection of actual samples and bioimaging of living cells. |
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