Design And Application Of Quantum Dots Based Fluorescent Sensors For Environmental Pollutants Analysis

Nowadays,the toxic persistent pollutants like nitrophenols and heavy metal pollution cause deleterious effects to the biological systems due to their acute toxicity.Thus,it is important to develop simple,rapid,efficient approaches for the selective and sensitive determination of the environmental pollutants.Semiconductor nanocrystal quantum dots?QDs?,with their excellent photostability,size-tunability,a broad range of excitation wavelengths and narrow luminescence spectra and chemically functional surfaces,have been widely used as fluorescence labels.In this thesis,two QDs-based fluorescence nanoparticles are designed and applied in environmental samples.The detail contents and results are as follows:?1?Quantum dot-based molecular imprinting nanoparticles for fluorescence detection of 4-nitrophenol in environmental waters.A novel molecular imprinting fluorescence nanoparticle was constructed via a facile surface imprinting polymerization in a one-pot synthesis strategy.And highly selective and sensitive recognition and detection of 4-nitrophenol?4-NP?was reported.Firstly,surfactant of 2-aminoethyl methacrylate hydrochloride?AMA?was interacted with aqueous carboxyl-CdTe quantum dots?QDs?.The resultant AMA-modified QDs were used as a core support and a fluorescent signal source.Then,an ultrathin 4-NP imprinted shell?ca.4 nm?was formed on the QD surface?i.e.,QD@MIPs?by a simple facile free radical polymerization step.The electron transfer process between QDs and 4-NP results in a significant fluorescence quenching of the QD@MIPs nanoparticles,by which 4-NP could be sensed,and a detection limit of 0.05 ?mol/L was attained.Furthermore,QD@MIPs were successfully applied to determine 4-NP in seawater and lake water samples,presenting high recoveries in the range of 93–109% at three spiking levels with the relative standard deviation of 3.1–4.8%.The simple,rapid,reliable QD@MIPs-based method proved to be potentially applicable for the highly selective and sensitive fluorescence determination of trace 4-NP in complicated environmental water samples.?2?Functional ZnS:Mn²⁺ quantum dots?QDs?nanoparticles for the sensitive fluorescent detection of copper?II?ion in aqueous solution.We developed the novel ZnS:Mn²⁺ quantum dots-based nanoparticles for detection of Cu²⁺ on the basis of an electron-transfer induced fluorescence quenching mechanism.The semiconductor nanocrystals of manganese-doped ZnS QDs offer stable optical properties and show intrinsic dual-emission.The L-cysteine?L-cys?and 6-mercaptonicotinic acid?MNA?were modified on the surface of ZnS:Mn²⁺ QDs.They could prevent the aggregation of nanoparticles and make them available for the interaction with the target ion.Due to the strong chelating ability of L-cys and MNA to copper ion,the fluorescence intensity of 593 nm emission peak in the MNA-L-Cys-ZnS:Mn²⁺ nanoprobe is selectively quenched in the presence of Cu²⁺ while the fluorescence of 412 nm emission peak remains constant,resulting in an obviously orange red to purple distinguishable fluorescence color response as the amount of Cu²⁺ is increased.The MNA-L-Cys-ZnS:Mn²⁺ nanoprobe presents a satisfactory linearity in the range of 5-500 nmol/L and a detection limit of 1.2 nmol/L.The as-proposed nanoprobe shows high anti-interference for common coexistent ions,which provided an rapid,convenient and high-effective sensing strategy to Cu²⁺ detection.