| With the development of technology and the progress of people’s living standards,the impact of human production and life on environment has become increasingly complex.In this situation,how to get comprehensive and diverse environment related information through environmental detection,and provide data support for environmental protection and pollution treatment is a new challenge for environmental workers.Meanwhile,the concept of environmental detection has been further broadened,including not only the detection of traditional environmental pollutants,but also the detection of environmental conventional substances as well as environmental natural indicators.Therefore,it is essential to promote the development of new environmental detection methods that are simple and environmentally friendly.Among the existing methods,fluorescence method stands out due to its convenient operation and simplicity of equipment.Carbonized Polymer Dots(CPDs)are a type of nanomaterials with unique fluorescence response properties and low toxicity,which make them excellent promising for applications in environmental detection and an excellent choice as fluorescent nanoprobes.Therefore,based on the application requirements of environmental detection problem,this thesis designed and synthesized environmentally friendly fluorescence tunable multicolor biomass-based CPDs,and new methods for environmental detection based on the CPDs’ various fluorescence characteristics were established.The main research results are as follows:(1)A method for the hydrothermal preparation of color-tunable fluorescent CPDs using chlorophyll-rich biomass as raw material was established.This method was universally applicable to microalgae raw materials,and could realize the controllable synthesis of CPDs with target properties according to different functionalization requirements,providing a reference for the design and development of other types of biomass-based multicolor fluorescent CPDs.(2)Using the above-mentioned method,chlorella-derived blue-emitted CPDs were synthesized.This kind of CPDs with an excitation wavelength-dependent behavior have short optimal excitation/emission wavelengths.The fluorescence of these CPDs partly derived from the immobilization of potential fluorophores by the internal crosslinking polymerization structure,and partly from the surface state luminescence.Their absolute fluorescent quantum yield was about 10.60%,and had the advantages of good water solubility,stable fluorescence and low toxicity.These were beneficial for CPDs’ applications in a variety of fields,including the biological imaging and substance detection.Red-emitted CPDs(R-CPDs)were synthesized from chlorella through the abovementioned method.R-CPDs possessed two fluorescence centers and were dominated by the emission at 648 nm.Its red fluorescence was originated from the immobilization and protection for the chlorella-derived chlorophyll porphyrin groups by the crosslinking polymerization structure which formed with the participation of ethylenediamine.When exposed under UV light,the contained porphyrin structural groups in R-CPDs were destroyed,along with the emission intensity of longwavelength reduced,resulting in a change to the fluorescence color of R-CPDs from red to blue.While the ratio between chlorophyll content in microalgae and the dosage of ethylenediamine could affect the UV light sensitivity of the products,and had a crucial influence on the photobleaching resistance of the red emission in microalgaebased CPDs.The white-emitted CPDs(white-CPDs)were synthesized from chlorophyll through the above-mentioned method.The white-CPDs exhibited triple-emission characteristics,with the Commission International d’Eclairage(CIE)coordinate(0.34,0.32)very close to that of standard white light under optimal excitation,and could maintain a comparable fluorescence intensity in the presence of a variety of interfering substances.Characterization analysis showed that the chlorophyll-derived CPDs had typical structures of carbon core and polymer chain.During the reaction process,ethylenediamine participated in cross-linking polymerization,protecting and immobilizing the original or newly generated fluorophores,and the emission of the products was enhanced based on the Crosslink-enhanced emission effect(CEE).(3)A method for the determination of chlorella’s viability was established based on the excitation dependent property of chlorella-derived blue-emitted CPDs.Combined with cell imaging techniques,this method could achieve differentiation between living and dead chlorella through their distinct fluorescence characteristics after treated by CPDs.Therein,the retention of red fluorescence in living chlorella was achieved through the Forster resonance energy transfer(FRET)process between CPDs and the chlorophyll within chlorella.After preliminary validation,the viability detection of spherical algae in biofilms from natural water could be realized through this method.(4)A method for the determination of tetracycline antibiotics was established based on the short-wavelength excitation/emission characteristics of chlorella-derived blueemitted CPDs.Based on the inner filter effect between the CPDs and tetracycline,the detection process could be achieved.It exhibited a rapid response with the detection limit of 0.57 μM.Taken tetracycline hydrochloride as an example,the spiked recovery detection of tetracycline hydrochloride in actual water samples was achieved,showing comparable accuracy(recovery rate of 94.42-103.46%)and precision(RSD less than5.05%)to that of liquid chromatography as well as methods reported in other articles.Moreover,CPDs synthesized from different microalgae had comparable tetracycline hydrochloride detection ability to that of blue-emitted CPDs synthesized from chlorella,which broadened the access channel of fluorescence probes used in this method.(5)A method for the sensitive ratio fluorescence determination of hemin was established based on the multi-emission characteristics of white-CPDs.Hemin selectively reduced white-CPDs’ fluorescence intensity at 658 nm through inner filter effect,which made white-CPDs produced a change of fluorescence color from white to blue.Therefore,the visual detection of trace blood samples could be realized.As for quantitative detection,this method showed a good linear relationship in the range of0.10-0.95 μM with a detection limit of 0.043 μM.When used for the spiked recovery detection of hemin in serum,this method showed comparable accuracy(recovery rate of 93.50-99.98%)and precision(RSD less than 1.82%)to that of liquid chromatography as well as methods reported in other literature.According to different detection purposes and scenarios,this method can also be used for the determination of specific components or total amounts of porphyrin structures.In summary,this study could reduce the consumption of non-renewable resources during the synthesis of CPDs,showed no risk of secondary pollution during use,and concerned with environmental issues during application process,which was beneficial to environmental health and had certain environmental significance. |
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