Preparation Of Carbon Nitride Molecularly Imprinted Fluorescent Probe And Its Analytical Application In Food

Food is the first necessity of the people.Nowadays,an increasing number of food safety incidents have emerged,the quickly and effectively detection of food has attracted great attention.Graphitic carbon nitride(g-C3N4)exhibits superior performance due to their advantages of simple and cheap preparation process,good biochemical stability,environmentally friendly in many fields.But based on g-O3N4 sensors,selectivity is still a challenging issue.Molecularly imprinted polymer(MIP)has advantages of long service life,good stability and high selectivity.This selectivity problem is overcome by combining molecular imprinting techniques with g-C3N4.In this paper,a series of fluorescent probe have prepared by combining g-C3N4 with MIP for the detection of target analytes in food.The main contents are as follows:Firstly,the fluorescent probe with high selectivity was synthesized by sol-gel method using 3-aminopropyltriethoxysilane as a functional monomer,chlortetracycline(CTC)as a template molecule,tetraethyl orthosilicate as a crosslinking agent and g-O3N4 as a fluorescent component.This synthetic composite was characterized by transmission electron microscopy,Fourier transform infrared spectroscopy and so on.The material was used to detect CTC by the fluorescence quenching method.The fluorescence quenching was due to g-C3N4 and the benzene ring of CTC through n-n electron donor-acceptor interaction and electrostatic force.The probe strategy was successfully applied to milk analysis,and the recoveries ranged from 90.1%to 95.7%,with relative standard deviations of 1.8%-2.8%;the detection limit for CTC was 8 ng mL-1.The results indicate that this method combined the high sensitivity of fluorescence detection with the excellent selectivity of MIP.The new material can be widely used in the detection of CTC in dairy products.MIP fluorescent probe based on silica sphere coated g-C3N4(MIP@SiO2@g-C3N4)was synthesized by reverse microemulsion method for sensitive and selective detection of quercetin.The MIP@SiO2@g-C3N4 fluorescent probe was characterized by transmission electron microscopy,Fourier transform infrared spectroscopy,and X-ray powder diffraction.The optimal reaction time,pH value,and the fluorescence quenching mechanism were discussed.The fluorescence quenching mechanism between fluorescent probe and quercetin was static quenching and photoinduced electron transfer(PET),with existence of ?-? interaction and electrostatic force.The fluorescent probe was successfully used to analyze quercetin content in beverages and red wines.It showed a good linear relationship within a certain range of concentrations and the detection limit of quercetin was 2.5 ng mL-1.The recoveries were 90.7%-94.1%,and the relative standard deviations were 2.1%-5.5%.The protonation of g-C3N4 quantum dots with hydrochloric acid not only changes the surface charge but also increases the water solubility.The high selectivity MIP fluorescent probe was synthesized by using acrylamide as a functional monomer,chloramphenicol as a template molecule,and ethylene glycol dimethacrylate as a crosslinking agent.Hydrogen bonding is formed between acrylamide and chloramphenicol during the polymerization.The elution of template molecules leaves a large number of selectively recognized pores that can specifically recognize chloramphenicol.This material was characterized by transmission electron microscopy,X-ray powder diffraction and UV spectroscopy.The best pH,binding time,selectivity and fluorescence quenching mechanism were explored.The molecularly imprinted material was successfully used for the detection of chloramphenicol in honey samples.Under the optimal conditions,the complex showed a good linear relationship in the range of 40-1500 ng mL-1.The detection limit of chloramphenicol was 10,9 ng mL-1.The recoveries were 92.8%-96.3%,and the relative standard deviations were 2.9%-5.89%.