Electrochemiluminescence Sensor And Biological Compatibility Of Carbon Nitride

Graphite-phase polymeric carbon nitride (GPPCN) is an emerging organic semiconductor, and the applications based on its electrochemiluminescent (ECL) properties in the field of sensing has drawn many attentions such as detecting metals ions in recent years. However, when the concentrations of interfering metal-ions are several times higher than the target metal-ion, it is almost impossible to distinguish which metal-ion changes the ECL signals in real sample detection, making the reliable quantitative analysis a challenge. Therefore, to develop a novel multiple signal detection method to eliminate this false positive incidence is highly anticipated. Moreover, we explored the biocompatibility and antibacterial of GPPCN in order to expand its practical application.In this thesis, the dual-ECL signals sensor based on the ECL signal of GPPCN nanosheets was developed, e.g., for the detection of nickel ion at anodic and cathodic potentials, respectively. False positive results were largely avoided, thereby increasing the accuracy of experimental results. Simultaneously, the GPPCN biocompatibility and antibacterial research for its applications in environments and biosensors were also investigated. The detailed studies are listed as follows:Firstly, the bulk GPPCN was prepared by the condensation of dicyandiamide as the precursor in the high temperature. Then ultrasonic exfoliation of bulk GPPCN was performed in water. After that, the stable GPPCN Nanosheets was obtained by centrifuging. The successful preparing of GPPCN Nanosheets was proved by scanning transmission electron microscope, UV-visible absorption spectroscopy, fluorescence spectroscopy, and X-ray diffraction. The ECL mechanism of GPPCN Nanosheets was studied in different driven potentials, and it was found the ECL signal was of high stability and intensity in both cathode and anode potentials, which was favorable of the construction of the subsequent sensor.Secondly, the dual-ECL signals sensor was based on that GPPCN Nanosheets exhibited distinct quenching or enhancement of ECL signal at different driven potentials in the presence of the different metal-ions. As an example, for the detection of nickel ion, the assay linear range was of 10-120 nM with a detection limit of 1.13 nM. Furthermore, the proposed analytical method was successfully applied for detecting trace Ni2+ion in tap and lake water. Moreover, the mechanism of the ECL changes of GPPCN Nanosheets after adding the metal ions was explored. It was presumably ascribed to the diversity of energy level matches between metal ions and GPPCN nanosheets and catalytic interactions of the intermediate species in ECL reactions in anodic potential. Therefore, the proposed strategy of modulating multi-ECL signals of GPPCN would pave more reliable and promising applications of carbon-rich materials in sensing and other essential state-dependent responding without labelling and masking reagents.Finally, the biocompatibility of bulk-GPPCN-550℃ was evaluated in MTT assay with Hela cells as model cells, and it was found the biocompatibility was high. Furthermore, bulk-GPPCN-550℃ had strong antibacterial properties in Bacillus subtilis as model bacteria by plate count method under light conditions and the antibacterial mechanism was studied.