Preparation Of Novel Graphitic Carbon Nitrides Nanocomposites And Appilication In Determinnation Of Environmental Hormone

Hundreds of chemicals have been provedted or suspected with endocrine disrupting effects,referred to as environmental hormone?EH?.EH has the characteristics of easy residue and hard degradation in multiple environmental mediums.A series of EH,especially bisphenol A?BPA?,pentachlorophenol?PCP?,paranitrophenol?PNP?and octylphenol?OP?may enter the body via air cycle and food chain.They are not biodegradation easily and tend to accumulate in living organisms,causing various diseases and disorders.Therefore,more and more people are committed to screen for and detect EH.However,now conventional analytical methods can not satisfy people's demands,and electrochemical sensors have received particular attention due to their simple operation,low cost,high sensitivity,good selectivity,and easy preprocess.In recent years,the polymer semiconductor catalyst,graphite carbon nitride?g-C₃N₄?,has drawn much attention for its good properties such as unique energy band structure,excellent chemical stability and controllable.In this dissertation,three kinds of novel graphite carbon nitride nanocomposites were synthesised and their modified electrodes were constructed for highly sensitive detection methods of BPA,PCP,PNP and OP.The main work and results are as follows:?1?The Co₃O₄/g-C₃N₄ heterojunctions with high electrochemical activity were prepared by a facile one-pot thermal decomposition technique.The good performances of crystal structures,Brunauer-Emmett-Teller?BET?surface area and electrochemical impedance spectroscopic Nynquist plots demonstrated that the doping amount of Co and the calcining temperature played a key role in the formation of the Co₃O₄/g-C₃N₄ heterojunctions.Compared with g-C₃N₄,it was found that the optimal heterojunctions obtained with 0.8 wt% Co doping at 500 oC possessed a larger BET surface area(91m2g^-1),a smaller electron-transfer resistance and a narrower band-gap?Eg = 2.36 eV?,which could increase the surface-adsorbed concentration of environmental hormone,and accelerate the electron-transfer rate.Moreover,the heterojunctions exhibited a lowering valence band?Vf =-1.38 V?,a higher donor density(Nd =3.76×10³¹ cm^-3)and ahigher concentration of pyridinic N,which were all beneficial to improve the oxygen reduction reaction?ORR?activity,ultimately making an enhancement electrochemical activity for environmental hormones.Furthermore,there was a wide linear range from 5.0 nmol L^-1 to 12 ?mol L^-1 and a lower average limit of detection of2 nmol L^-1for bisphenol A,pentachlorophenol,p-nitrophenol and octylphenol.On the basis of the Co₃O₄/g-C₃N₄ heterojunctions,a simple and sensitive electrochemical method was constructed for the determination of environmental hormones in water samples.Meanwhile,a conceivable mechanism of electrochemical enhancement at the Co₃O₄/g-C₃N₄ heterojunctions modified electrode was proposed.?2?We prepared ZnS nanosheets by a solvothermal method and The ZnS/g-C₃N₄ nanocomposites by a stir-mixing method.The nanocomposites and DNA were modified onto the surface of a glassy carbon electrode?GCE?by polymerization,and ZnS/g-C₃N₄/DNA/GCE modifier electrode was prepared.The experimental results showed that ZnS/g-C₃N₄/DNA/GCE modified electrode had a significant electrocatalytic activity for nonylphenol?NP?and pentachlorophenol?PCP?.Under the optimized experimental conditions,the oxidation peak current of NP and PCP increased linearly with the concentration of NP and PCP over the range of 10 nmol L^-1to 20 ?mol L^-1and10 nmol L^-1 to 10 ?mol L^-1 with a detection limit of 3.3 nmol L^-1.The sensorallows NP and PCP determination in real water samples with high repeatability and stability.?3?Nickel oxide and nickel co-doped graphitic carbon nitride?Ni O-Ni-g-C₃N₄?nanocomposites were successfully prepared by thermal treatment of melamine and NiCl₂·6H₂O.A detection method of OP in environmental water samples was developed based at NiO-Ni-g-C₃N₄ nanocomposites modified electrode under infrared light irradiation.Cyclic voltammetry?CV?and differential pulse voltammetry?DPV?were used as the analytic technique of OP,exhibiting stable and specific concentration dependent oxidation signal in the presence of OP in the range of 10 nmol L^-1to 1 ?mol L^-1 and 1 ?mol L^-1 to 50 ?mol L^-1,with a detection limit of 3.3 nmol L^-1?3S/N?.This method could use in real water samples.