Preparation Of Carbon Quantum Dots And The Application Of Detection Toward Mercury Ion And Glucose

The optical sensors continue to retain an important position in the development of analytical chemistry owing to the intrinsic merits including high sensitivity and selectivity,rapid response,ease of operation,visual observation and so on.In recent decades,the emergence and usage of nanomaterials play significant roles in promoting the development of detection technology.Compared with the traditional materials,novel nanomaterials possess unique features,such as quantum effect,small size effect and surface effect,thus endowing them with remarkable physical,chemical and optical properties,including high surface activity,large specific surface area,low toxicity,preferable biocompatibility and excellent photo stability.Nanomaterials can be used as excellent units of signal transmission in the design of optical detections,which makes great contributions to the development of optical detecting approaches.By taking advantage of the surface absorption properties of metal nanoparticles and the fluorescence properties of carbon quantum dots?CQDs?,combining the catalytic activity of metal ions-copper ions(Cu²⁺),the principle of fluorescence resonance energy transfer?FRET?,and the reaction of copper mirrors.This thesis was focused on the construction of some novel,simple,rapid and sensitive optical?colorimetric and fluorometric?sensors for Hg²⁺and glucose.The interaction mechanism between nanomaterials and these target analytes is preliminarily discussed,and the applications of these probes in real samples are also explored.The specific contents are as follows:?1?China grass carp scales?CGCS?were used as original materials to prepare carbon quantum dots?CQDs?by a microwave hydrothermal method,because of a large number of cysteines containing sulfhydryl group.S atoms display higher thermodynamic affinity and faster integrating process with Hg²⁺due to strongly sulphophile.Thus,the obtained CGCS-CQDs can be used as a specific fluorescence probe in detection of Hg²⁺.Subsequently,CGCS-CQDs were characterized by HR-TEM,XRD,FT-IR and XPS analyses.The optical properties of CGCS-CQDs were elucidated by fluorescence and UV-vis spectra.Additionally,the effects of pH values and salt concentrations on optical properties of CGCS-CQDs were also researched by means of fluorescence spectra.Under optimal conditions,the decrease of fluorescence intensity displays a good linear relationship in permitted detection concentration range of Hg²⁺from 0.05 to 30?mol/L and a detection limit of 0.1403?mol/L is acquired.Meanwhile,the effect of other metal ions on the detection of Hg²⁺by using CGCS-CQDs as fluorescence probe was studied,suggesting that the CGCS-CQDs could be an excellent fluorescence probe for the detection of Hg²⁺.Eventually,the CGCS-CQDs were applied for Hg²⁺detection in lake water,cosmetic and urine,demonstrating their potential towards diverse applications.?2?A new fluorescent strategy for detecting glucose based on copper ions supported N,O-doped carbon quantum dots?N,O-CQDs?forming N,O-CQDs/Cu²⁺nanocomplexes is presented.The obtained N,O-CQDs are characterized by HR-TEM,XRD,FT-IR and XPS analyses.Subsequently,the optical properties of N,O-CQDs are elucidated by UV-vis and fluorescence spectra.The proposed strategy refers to three steps:quenching of N,O-CQDs fluorescence by Cu²⁺ions,production of Cu₂O and gluconic acid from Cu-catalyzed oxidation of glucose and leaving of Cu²⁺ions from the N,O-CQDs surface causing the recovery of fluorescence intensity.In the N,O-CQDs/Cu²⁺nanocomplexes,Cu²⁺ions act as quencher to decrease the N,O-CQDs fluorescence by surface energy transfer.The Cu-catalyzed oxidation of glucose makes the Cu²⁺ions be reduced forming Cu₂O,which frees the Cu²⁺ions from the N,O-CQDs surfaces and restores the fluorescence of N,O-CQDs.Therefore,the change of fluorescence depends on the concentrations of Cu²⁺and glucose.Under optimal conditions,the quantitative analysis of glucose gives a detection limit of0.455?M.Particularly,as a non-enzymatic glucose probe,the method based on N,O-CQDs/Cu²⁺can be applied to detect low concentration of glucose.It also offers some advantages of facile preparation of nanomaterials and sensitive analysis and low experimental cost.