Design Of Biomass Carbon Dots Based Fluorescence Probe And Its Application In Drug Analysis

Fluorescent carbon dots?CDs?are a kind of nano materials which have been widely used.They not only have good biocompatibility and photostability,but also have the advantages of simple preparation process and easy functionalization.Since they were first discovered in 2004,CDs had good application prospects in the fields of drug loading,biological imaging and analytical detection.At present,more and more researchers pay attention to the strategy of using biomass materials as carbon sources to prepare CDs.Compared with other carbon sources,biomass materials have the advantages of low cost and large-scale synthesis.Nowadays,energy is becoming increasingly scarce,so it is a hot topic with great challenge and development potential for further study the biomass CDs.Therefore,it is very important to select suitable carbon precursors and synthesize multifunctional composite materials.In this paper,different biomass materials such as sweet potato peels,bones are used as carbon precursors,and then functional materials are reasonably prepared with different methods.Some novel fluorescence sensing systems are established,which can be used for the rapid,high selective and sensitive analytical detection of drugs in environment and food samples.In preface part,we firstly give a brief introduction to the properties,preparation,modification and quenching mechanism of biomass CDs,as well as their recent progress in fluorescent analysis.Then,we conduct the specific research from the following aspects:1.Bio-waste sweet potato peels were used as carbon precursors to prepare biomass CDs.A molecularly imprinted fluorescent probe based on biomass CDs was prepared by a sol-gel method using oxytetracycline as a template molecule.The morphology,structure and optical properties were characterized by transmission electron microscopy,Fourier transform infrared spectrophotometer,UV-vis absorption,X-ray photoelectron spectroscopy and fluorescence spectrophotometer.The mechanism of fluorescence quenching was also explored.The experimental results show that the prepared fluorescent molecularly imprinted polymers have good optical stability and specific recognition sites with stable structure,which can selectively detect the template molecule oxytetracycline.At the same time,the interference of autofluorescence in honey samples can be avoided by simple separation and redispersion process.Based on this,we constructed a highly selective and sensitive analytical method for the detection of oxytetracycline with satisfactory results.2.At present,biomass CDs are widely used in analytical detection,but there are still some limitations.For example,it takes too much time to prepare biomass CDs through hydrothermal reaction,and the biological macromolecules in practical samples may have some interference on the analytical detection of complex samples.In order to improve the reaction rate,the high-pressure microwave method was used to realize the efficient and rapid synthesis of biomass CDs.To improve the anti-interference ability of the materials,the restricted access materials were introduced and glycidyl methacrylate was used as the comonomer to increase the surface hydroxyl groups of the composite and avoid the interference of biomacromolecules.The obtained multifunctional composite materials can selectively recognize metronidazole and have good reusability.We have successfully applied the synthesized multifunctional composite materials to highly sensitive and selective detection of metronidazole in serum with the recoveries of 93.5%-102.7%3.The biomass CDs with self-doping characteristics were prepared by using bio-waste pig bones as carbon sources.Among them,calcium,sulfur and nitrogen exist in the structure of biomass CDs through self-doping effect.Generally speaking,the luminescent characteristics of fluorescent nanomaterials are easily affected by extreme conditions,leading to fluorescence quenching.However,the prepared biomass CDs in this experiment have the advantages of high fluorescence intensity and good stability,which can be used in strong alkali environment.In addition,we constructed a fluorescent"switch"platform and realized the selective detection of dimethoate pesticides by using the prepared biomass CDs.When the biomass CDs are mixed with dithizone,the blue fluorescence of biomass CDs is quenched due to the coordination reaction.With the addition of dimethoate,the dithizone ligands modified on the biomass CDs were replaced by the hydrolysate of dimethoate,thus the fluorescence of system was restored.Under the optimal experimental conditions,the linear detection range of dimethoate is 0.15-5.0?mol L^-1,and the detection limit is 0.064?mol L^-1.The method was applied to the rapid detection of dimethoate in environmental water samples with the recoveries of 93.4%-104.9%.4.The preparation of biomass CDs by high-temperature solid-phase pyrolysis has the advantages of using less solvents and large-scale synthesis.The biomass CDs were encapsulated in mesoporous silica by a one-step method and further combined with L-cysteine modified Mn-doped ZnS quantum dots to prepare a novel ratiometric fluorescent probe.Among them,the fluorescence intensity of biomass CDs at 459 nm was used as a reference signal,and the fluorescence intensity of Mn-doped ZnS quantum dots at599 nm was used as a response signal to detect nicosulfuron.The construction of ratiometric fluorescent probe in this paper can not only reduce environmental interference,but also increase the contact area between the fluorescent probe and nicosulfuron due to its unique mesoporous structure and high specific surface area.We applied the established method to detect nicosulfuron in environmental water samples with satisfactory results.