Synthesis And Application Of Ruthenium Bipyridine Functional Dyes For Photoelectrochemical Detection Of Mercury

Mercury is one of the most dangerous and ubiquitous heavy metal element in nature. Even a low concentration of mercury ion can hurt human health.So,it is necessary to develop highly sensitive and accurate detection method for it.Among the various analytical methods,photoelectrochemical?PEC?method is well known for its high sensitivity,low background,portable,and fast response,thus has shown great potential in the on-site detection of Hg²⁺.For Hg²⁺recognition,the mostly used receptor is T-T riched aptamer,which has good selectivity,but need additional signal labeling and strict operation condition.To solve this problem,this thesis designs and synthesizes a new Ru?II?complex based PEC probe,and realized the highly sensitive and selective detection of Hg²⁺.The detailed work is as follows.1.Synthesis and characterization of ruthenium bipyridyl Dyes and their nanocomposites with TiO₂ nanoparticlesA series of new ruthenium bipyridyl functional Dyes,including Ru-1,Ru-2 and Ru-3were synthesized and integrated with TiO₂ nanoparticles.The MLCT absorbance peaks of Ru-1,Ru-2,and Ru-3 are located at 530,530,and 450 nm,with the molar extinction coefficient of 0.87×10⁴,1.69×10⁴,and 1.12×10⁴ L·mol^-1·cm^-1,respectively,indicating these Dyes all have good visible light harvesting capacity.Under the irradiation of visible light,these Dyes could all emit and transfer photoelectron from their excited states to the conduction band of TiO₂,and improve the photo-to-current conversion efficiency of the Ru-TiO₂ nanocomposites.Among them,the efficiency of Ru-2 was relative lower due to its smaller driving force of less than 0.2 V.Ru-1,Ru-2,and Ru-3 anchored to the TiO₂ respectively with the phosphonic acid,phosphonic acid,and carboxylate group,and former two Ru?II?complexes showed better stability in aqueous systems due to the relatively stronger infinity of phosphonic acid to TiO₂.Besides,the introduction of–SCN group as ligand will delocalize the holes generated during the photo irradaition process and supress the recombination of hole⁺-e^-pairs,thus significantly improving the photo-to-current conversion efficiency of the Ru-1 complex.By comparison,the Ru-1 exhibits both good stability on TiO₂interface and strong PEC activity,thus could be applied for the construction of PEC sensors for bioanalysis.2.PEC detection of Hg²⁺in real samples using Ru-1/TiO₂/FTO.Ru-1 with high photo-to-electron conversion efficiency and good stability was employed for the recognition of Hg²⁺in a series of complex matrixes.The recognition of Hg²⁺by–SCN was proved by UV-vis spectra,CVs,and IR spectra,which changed the energy distribution of the Ru and made–SCN lose its ability to prohibit the recombination of electron and holes, thus decreasing the photocurrent response of the system.Based on the photocurrent decrease,the Ru-1/TiO₂/FTO shows high sensitivity and good selectivity for Hg²⁺.Under optimal conditions,two wide linear ranges from 10^-12 to 10^-7 g/mL 10^-7 to 10^-3 g/m L are obtained,with a low limit of detection of 6.3?10^-13g/m L.The PEC probe shows good reproducibility and selectivity,which can exclude the interferents from the possible co-existed metal ions and protein.Real sample analysis in urine sample,serum,and cell lysis solution indicates the probe possesses good accuracy.