Surface Functionalization Of High Efficient Fluorescent Carbon Dots And Their Application In Detection Of Cr(?)ions

Carbon dots(CDs)is a kind of fluorescence carbon nanomaterial with quasi spherical structure.Carbon dots is smaller than the traditional quantum dots(less than 10 nm),and exhibits special properties,such as good photostability,without cytotoxicity and wonderful biocompatibility,which different itself from macroscopic materials,shows an excellent application prospect in the field of biological imaging and labeling,recognition and detection metal ions,photoelectric conversion and drug carrier.In recent years,frequent accidents caused by heavy metal ions are occurred in our country,and have caused great security risks.Since heavy metal ions are non-biodegradable and can be accumulated in organisms,and causes harm to the human body via affect enzyme activity by food chain.Therefore,finding a sensitive and selective way to determinate heavy metal ions with a cost-effective and convenient procedure is an urgent problem.Among all the detection methods,the fluorescence detection method is distinguishes itself by simple operation,high sensitivity and timely response(relatively).The Carbon dots have high fluorescence efficiency,and can realize trace detection of metal ions.But,there are still some problems,such as time consuming;and suboptimal selectivity and specificity.In order to solve the above problems,this paper,we modifies the Carbon dots to improve its' selectivity,and then synthesizing a kind of polymer film which substrate with quartz plate to solve the problems of complicated operation.The specific contents are as follows:First of all,use non-toxic citric acid and ethylenediamine as carbon source,via hydrothermal method to obtain polymer carbon dots.Hydrothermal method is simply and speed.The surface of polymer carbon dots is rich in carboxyl and amino groups,this indicates it can be modified through chemical reaction.Secondly,the new fluorescent probe was prepared by grafting the polymer carbon dots and the 1,10-phenanthroline(Phen),Phen can coordinate with metal ions.So after grafting,the specificity and sensitivity are both improved.The polymer carbon dots and the new fluorescent probe are characterized by transmission electron microscopy(TEM),fourier transform infrared spectrometer(FT-IR),fluorescence spectroscopy and ultraviolet-visible spectrophotometer(UV-Vis).The fluorescence mechanism of the probes and metal ions are also investigated.It is found that the new probe had better detection of Cr(?),with a detection limit of 0.0041 ppm,lower than the GB3838-2002)?(0.01ppm)and GB/T 14848-93 ?(0.01ppm).Thirdly,the polymer carbon dots is grafted with 8-hydroxy quinoline derivatives,8-hydroxy quinoline can also coordinate with metal ions,so after the grafting,the polymer carbon dots' sensitivity and specificity are both improved.This new fluorescent probe is,the same as above,characterized by TEM,FT-IR,UV-Vis and fluorescence spectroscopy.The fluorescence mechanism of the probes and metal ions are also investigated.It is found that this probe had better detection of Cr(?)with a detection limit of 0.05 ppm,exactly equal to the GB3838-2002)?(0.05 ppm).But the linear range detection of the probe is relatively wide(0-50 ppm),so it has wide applicability.In the end,a kind of hydrophilic polymer membrane material is designed and synthesized,and then the fluorescent probe is grafted into the polymer material in order to realize the online real-time detection of metal ions.