Preparation Of Fluorescent Nanomaterials And Their Application In The Detection Of Organophosphorus Pesticide

In recent years,organophosphorus pesticides(OPs)have been widely used in agricultural production and household pest control.However,these compounds,which are harmful to health and the environment,cannot be degraded spontaneously and remain in water resources,fruits,vegetables and processed foods,posing a serious threat to human health.Therefore,high sensitivity,high selectivity and simple and portable quantitative detection of these harmful substances are particularly important.Biosensing technologies such as electrochemical,thermal,optical(fluorescence,colorimetry)meet these requirements and have been used for detection on a large scale.Among them,the detection platform constructed with"turn on-off"fluorescence signal has rapidly become a promising quantitative detection method due to its advantages of high sensitivity and easy observation with the naked eye.Fluorescent nanomaterials have also attracted extensive attention of researchers due to their low toxicity and ease of modification.Among them,fluorescence detection methods based on the two test mechanisms of internal filter effect(IFE)and fluorescence resonance energy transfer(FRET)are widely used,but an excellent detection platform requires stable fluorescent signal probes to further obtain more accurate results.In this thesis,two stable fluorescent probes,conjugated polymer nanoparticles(CPNs)and carbon quantum dots(CQDs),were designed and synthesized.Based on the enzymatic reaction process of alkaline phosphatase(ALP),the above two quenching mechanisms were used to achieve sensitive and convenient rapid detection of OPs.The specific work contents are as follows:(1)CPNs were modified with carboxyl-functionalized polymer(styrene-maleic anhydride copolymer)by nanoprecipitation method.By adjusting different ratios and analyzing different preparation methods,a new synthesis method of nanoparticle was summarized and proposed;by hydrothermal,aspartic acid and phenylboronic acid were used as precursors to prepare boric acid-modified carbon quantum dots,the product that meets the experimental needs was obtained by adjusting proportion,reaction time and reaction temperature.The preparation of two fluorescent nanomaterials laid a solid foundation for further building a sensitive detection platform.(2)With the help of ALP catalyzed hydrolysis of 4-nitrophenyl sodium phosphate(NPP)to 4-nitrophenol(NTP),a detection platform was constructed based on the internal filter effect.Since the UV absorption of the hydrolyzed NTP is similar to the fluorescence excitation wavelength of the synthesized CPNs,the content of NTP directly affects the final fluorescence emission,and the high sensitivity of ALP to organophosphorus pesticides indirectly reflects the feasibility of this platform.The platform has a wide detection range(5-150μg/L),this detection width is not reached in the previous report.Similarly,the minimum detection limit of the sensing platform is also low(LOD:0.418μg/L),the actual sample test results also show that it has considerable repeatability and satisfactory results are obtained.(3)A highly sensitive fluorescence detection platform based on fluorescence resonance energy transfer was designed.ALP hydrolysis produces ascorbic acid,which reduces Ag~+to silver shell attached to CPNs,resulting in fluorescence quenching.The sensitivity of ALP to OPs and the specific experimental operation also demonstrated the feasibility of this platform for the detection of organophosphorus pesticides.It has a wide detection range(15-100μg/L)and a low minimum detection limit(LOD:0.960μg/L),which makes it possible to quantitatively analyze OPs without the aid of high-precision instruments.At the same time,the method can also accurately analyze ALP in the range of 10 U/L-80 U/L,and the minimum detection limit is 2.36 U/L.(4)The highly dispersed blue fluorescent carbon quantum dots were synthesized by a one-step hydrothermal method.The strongest fluorescence emission of CQDs is consistent with the UV absorption of NTP.The working principle of the fluorescence detection platform was similar to the previous chapter,and the detection effect was relatively better,The detection range is 1-6μg/L,and the lowest limit of detection(LOD)is 0.087μg/L.In addition,the surface of the carbon quantum dots is rich in boronic acid groups,which can directly act on the cis-diol on glucose to aggregate the carbon dots,and the solution fluorescence is greatly weakened.Glucose detection can be performed in the concentration range of 50-1000μM,with an LOD of 28.54μM,and the excellent biocompatibility of CQDs makes it possible to directly detect glucose components in serum or plasma.