Study On The Design And Properties Of New Fluorescent Nanoprobes Derived From Biomass

Carbon dots（CDs）represent a type of quasispherical fluorescent nanocarbons with sizes below 10 nm,which possess superior merits such as tunable emission wavelength,good florescence stability,free of photobleaching,low cytotoxicity and excellent biocompatibility.Therefore,CDs can be potentially applied in fluorescent nanoprobes,environmental detection,bioimaging,fluorescent sensing as well as photocatalysis,etc.In this thesis,a series of CDs were synthesized from various biomass waste,the optical performance was enhanced by optimization of synthesis conditions and heteroelement N content.Furthermore,the biological compatibility of CDs was examined,and their applications in the pharmaceutical analyses were focused by virtue of the intrinsic fluorescence activities.Main contents of this paper are as follows:1.GF1-CDs with high fluorescence quantum yield（QY）of 9.0%were synthesized through one-step hydrothermal carbonization treatment of biomass precursor（fish scales of grass carp）.The GF1-CDs exhibit good fluorescence nature,thus enables the application as a simple and rapid fluorescent nanoprobe for determination of lidocaine hydrochloride（LH）pharmaceutical through static quenching.The GF1-CDs based fluorescent LH probe demonstrated a wide linear range(0.18¹.3 mmol L^-1)and a low detection limit(0.054 mmol L^-1).Additionally,the GF1-CDs also demonstrate low cytotoxicity and good biocompatibility,showing the good pratical applicability.2.CF-CDs were prepared by one-step hydrotmermal treatment of through N,O containing fish scales of crucian carp precursor.The optimization of synthesis conditions has shown that the CF-CDs prepared at200℃for 20 h are highly fluorescent,water soluble with particle size of about 5.0～10 nm.The fluorescence intensities of CF-CDs can be effectively quenched by Fe³⁺,which enables the application as fluorescent nanoprobe for Fe³⁺with high selectivity and sensitivity.KG-1a cells were attempted as model to assess the feasibility of the CF-CDs for intracellular bioimaging.Blue fluorescence was observable in the intracellular region of the cells under irradiation of UV light,the adding Fe³⁺causes the obviously dimmed fluorescence,implying the applicability of the CF-CDs in biosensing.Bean sprouts were employed as the model organisms to investigate the influence of CF-CDs on the growth of live plants.The results have shown that CF-CDs at low concentration(below 0.50 mg mL^-1)does not cause obvious difference on the growth of sprouts relative to the control group.3.Fluorescent GF2-CDs was prepared through one-step pyrolysis of an easily available fish scales precursor without using of any passivant or elemental doping,the afforded GF2-CDs demonstrate a high QY of 27%.The emission spectrum shows a strong peak at 450 nm under excitation at 400 nm,and Ag⁺-GF2-CDs complex can be formed through electrons transfer between Ag⁺and GF2-CDs,so Ag⁺can efficiently quench the fluorescence of the GF2-CDs,upon addition of glutathione（GSH）,the fluorescence of GF2-CDs can be recovered owing to the preferred combination between Ag⁺and GSH via the formation of Ag⁺-S bond or Ag⁺-NH bond,which therefore causes the dissociation of Ag⁺-GF2-CDs complex and leads to the recovery of fluorescence to some extent.Hence,the GF2-CDs can serve as a simple and rapid fluorescent probe for determination of glutathione with a wide linear range(1.6³6μg mL^-1)and a detection limit as low as 0.77μg mL^-1 through fluorescent on-off internations.The biocompatibilities of GF2-CDs were investigated by the flow cytometry technology using PI dying.The results showed GF2-CDs cannot lead significant toxicity to the cells.4.Highly fluorescent carbon dots（PSE-CDs）were synthesized through one-step hydrothermal carbonization and ethylenediamine passivation of an easily available prawn shell precursor.The as-prepared PSE-CDs exhibit high water-solubility,wavelength-tunable fluorescence nature,high photostability and resistance against biomolecules.The QY of the PSE-CDs is calculated to be 69%,which is obviously higher than that of PS-CDs free of passivation（QY=8.0%）.The fluorescence of the PSE-CDs can be effectively quenched by clomifene citrate（CC）through static quenching,therefore can serve as efficient fluorescent nanoprobe for determination of CC.The PSE-CDs based fluorescent CC nanoprobe exhibit a wide linear range(0.25¹0μg mL^-1)and a low detection limit of 0.20μg mL^-1.Additionally,the PSE-CDs also showed low cytotoxicity.Zebrafish was also used as the model organisms to investigate the influence of PSE-CDs on the embryo hatching in live animals.The results have shown that PSE-CDs does not cause obvious difference on the embryo hatching relative to the control group.The investigated PSE-CDs show good biocompatibility in appropriate concentration range,which furnish significant foundation for further biomedicine applications of PSE-CDs.