Preparation And Characterization Of Fluorescent Chemosensors For Palladium And Mercury Ions Detection

Nowadays,heavy metal pollution has already become one of the most main reason for the problem of human living environment.The environmental pollution caused by heavy metal has easy mobility,persistence and a high biotoxicity due to its particular physico-chemical property,and then making irreversible fatal harm to human body health.The detection of various heavy metals is extremely urgent with increasingly ecological and environmental problems.Hence,the chemosensers technology is emerged due to its characteristic of high selectivity,high sensitivity and real-time detection,and this technology has been widely applied to the field of heavy metal detection.The combination of small molecule fluorescent chemosensor and supporting substrate greatly enhances the application value of traditional small molecule fluorescent sensors,and this is also a research hot spot in the field of chemical sensors in recent years.In this dissertation,fluorescent chemical sensors based on silica nanoparticles,borosilicate glass slides and polyurethane were designed and prepared on the basis of research group.The first method is to endow a recognition group（-C=N）and a fluorophore immobilized on the surface of silica nanoparticles and glass slides,and the fluorescent silica nanoparticles and glass surfaces are prepared.In the second experiment,a small molecule fluorescent chemosensor（BS）containing the boron-dipyrromethene（BODIPY）as a matrix is designed and synthesized at first,and then a fluorescent polyurethane film（PUS）is prepared by polycondensation of monomer BS and tolylene diisocyanate（TDI）.The two fluorescent chemosensors not only exhibit highly and quickly selective properties to divalent palladium ions(Pd²⁺)and divalent mercury ions(Hg²⁺),respectively,but separate and remove the metal ions.The experimental contents and research results of this thesis are mainly divided into the following four parts:（1）In the first experiment,silica nanoparticles is synthesized firstly,and then3-aminopropyl triethoxysilane（APTES）,4-amino-1,8-naphthalic anhydride（ANA）and salicylaldehyde（SA）are introduced onto the surface of SiO₂ nanoparticles successively to obtain the fluorescent SiO₂ nanoparticles（CS1）.Glass-based fluorescent chemosensors（CS2）can be prepared via the same chemical modification method.The structure and morphology of CS1 and CS2 are confirmed by Fourier transform infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）and scanning electron microscopy（SEM）.The recognition properties of CS1 and CS2 for metal ions are investigated by using fluorescence spectrophotometer（FL）and UV-Vis spectrophotometer（UV-Vis）.（2）Research results show that both CS1 and CS2 can selectively detect Pd²⁺in aqueous solution quickly.CS1 can stably exist in solution with pH value of 2.21-11.92.When 16 common metal ions are added into CS1 solution,CS1 generate color change from yellow to yellowish-brown only upon the addition of Pd²⁺ions by naked-eyes,and the fluorescence intensity of CS1 decreased,showing the phenomenon of fluorescence quenching.In addition,the control experiment manifested that the fluorescent sensor can selectively recognize Pd²⁺without interfering with other metal ions only when the ANA and SA are simultaneously introduced into the substrate,and the detection concentration of Pd²⁺reach to 10μM when the conc.of CS1 solution is2.0 mg/mL.CS1 can repeatedly recognize Pd²⁺for at least 5 times without significant degradation of detection performance.Similarly,CS2 has also the ability to selectively recognize Pd²⁺.CS1 and CS2 can adsorb and separate Pd²⁺as well,the adsorption capacities of CS1 and CS2 for Pd²⁺are 2.31μg mg^-11 and 3.67μg cm^-2,respectively.（3）In the second experiment,the BODIPY derivative B1 is first synthesized,and then the precursor B2 containing aldehyde group is synthesized via Wilsmeier-Haack reaction and then reacted with 3-amino-1,2-propanediol（AP）to obtain small molecule fluorescence chemosensor（BS）.Finally,the monomer BS is polymerized with polyethylene glycol（PEG）and toluene diisocyanate（TDI）to prepare a series of fluorescent polyurethane membranes（PUS）.The structures of BS and PUS are confirmed by ¹H nuclear magnetic resonance（¹H-NMR）,mass spectrometry（MS）and FTIR.The recognition of BS and PUS for heavy metal ions is also investigated.（4）Research results show that BS and PUS can selectively recognize Hg²⁺in buffer solution（pH 6.56）,and PUS can separate and remove Hg²⁺.BS can stably exist in buffer solution with pH≤8.Through the experiment of metal ion detection and interference experiment in BS solution,it is found that BS can selectively recognize Hg²⁺without interfering with other ions.The color of BS solution added Hg²⁺changed from pink to light yellow,and the fluorescence intensity of BS increased.Fluorescent polyurethane membrane PUS can also selectively recognize Hg²⁺by color change and fluorescence enhancement.The recognition ability of PUS for Hg²⁺enhanced compared to BS,and the detection limit is 0.5μM.In addition,fluorescent polyurethane film can adsorb Hg²⁺effectively,the adsorption efficiency and adsorption capacity of PUS for Hg²⁺are 82.42%and 17.76μg cm^-2.