Construction Of Novel Fluorescent Sensing Methods Based On Carbonized Polymer Dots

Carbonized polymer dots（CPDs）are an emerging class of carbon dots（CDs）,which are composed of organic polymer chains and carbon skeleton with unique polymer/carbon hybrid structures and properties.CPDs show excellent optical properties of traditional CDs,and retain the properties of the polymer.In recent years,CPDs have attracted much attention as fluorescent materials due to their simple preparation,excellent optical properties,and good biocompatibility.In this thesis,functionalized CPDs were synthesized by a one-step hydrothermal method by regulating the precursor.The applications of CPDs are focus on the detection of hydroquinone（HQ）,chlortetracycline hydrochloride（CTC）and acetaldehyde（AA）based on the interaction between CPDs and the analytes.There are three parts in this thesis.1.Construction of HQ sensing method based on CPDs fluorescent systemCPDs were developed for the quantitative detection of HQ,which were synthesized by a hydrothermal treatment at 150℃ for 12 h using proline and polyethyleneimine（PEI）.The fluorescence of CPDs was significantly quenched by HQ,which was attributed to the fact that HQ was easily oxidized to 1,4-benzoquinone under alkaline conditions,and 1,4-benzoquinone might form hydrogen bonds with amino groups on the surface of CPDs.The electrons of the excited CPDs can be transferred to 1,4-benzoquinone,which can quench effectively the fluorescence of CPDs.CPDs can be used to detect HQ in the concentration range of 0.1～120μM with a limit of detection（LOD）of 80 n M.More importantly,the fluorescent probe can eliminate effectively the interference of catechol（CC）and resorcinol（RS）.In addition,CPDs have been successfully applied to the determination of HQ in real water samples,indicating that CPDs have the reliability and potential application value in HQ monitoring.2.Construction of CTC sensing method based on CPDs fluorescent systemIn this study,fluorescent CPDs for determination of CTC were synthesized using PEI as the sole precursor.The CPDs exhibited blue fluorescence under UV light,with a quantum yield of 14.58%.The maximum excitation and emission wavelengths were 350nm and 465 nm,respectively.When CTC was added,the maximum emission wavelength of CPDs was blue-shifted from 465 nm to 430 nm.The fluorescence intensity of CPDs has a good linear response with CTC concentration in the range of 0.1～120μM,and the LOD is 40 n M.CTC can strongly interact with CPDs and restrict the movement of CTC molecules,reducing nonradiative transitions,resulting in aggregation induced emission（AIE）.Blue-shift of the emission peak and significant enhancement of fluorescence intensity were observed,thus providing a basis for quantifying CTC.The sensing system is simple,sensitive and low-cost,and has been successfully applied to the sensitive determination of CTC in food（such as pork and fish）.3.Construction of a turn-off-on fluorescent system based on aggregation induced emission of AA using CPDs and Tb³⁺CPDs were prepared by a one-step hydrothermal method,using milk and PEI as precursors.AA can aggregate on the surface of CPDs with the assistance of Tb³⁺inducing AIE.Based on the AIE of AA,a turn-off-on fluorescence method was established for AA detection using the porous CPDs-Tb³⁺system.In the presence of Tb³⁺,CPDs aggregated immediately,and the fluorescence intensity decreased obviously for the formation of precipitate.AA can effectively embed on the surface of CPDs-Tb³⁺due to the porous structure.In the CPDs-Tb³⁺solution,AA exhibits obvious fluorescence enhancement effect.AA can be determined by the turn-off-on system based on the linear relationship between fluorescence enhancement and the concentration of AA ranging from 0.04 m M to42.48 m M,and the LOD was 20μM.The turn-off-on system was successfully applied to determine AA in wine samples.The strategy may be exploited to monitor AA in more drinking or foodstuff samples.