Synthesis Of Novel Quantum Dots For The Development Of Fluorescent Biosensors

Fluorescence quantum dots?QDs?,as a kind of OD nanomaterials owns distinct optical property due to the quantum confinement effect and edge effect.It has triggered much interest of researchers in different fields such as biosensors,cell imaging and biomedicine owing to the well photostability,long fluorescence lifetime,broad excitation spectra and narrow emission spectra.Among this,Graphene like structure nanomaterials WS2 quantum dots,black phosphorus quantum dots?BP QDs?and polydopamine dots possess outstanding fluorescence property which endow them potential value as biosensors.In this paper,we mainly focus on the synthesis of novel quantum dots WS2,BP,and polydopamine,then based on their fluorescence property to establish biosensors to achieve the detection of lipoic acid,evaluation of AChE activity and the determination fo Cu²⁺,respectively.Chapter 1 OverviewIn this chapter,we gave an outline about the feature of nanomaterials,development and application.Furthermore,we put emphasis on the construction of fluorescent biosensors in analytical and biological fields based on the novel quantum dots.At the last,the contents and significance of our research was proposed.Chapter 2 Facile Synthesis of Water-Soluble WS2 Quantum Dots for Turn-on Fluorescent Measurement of Lipoic AcidIn this chapter,a facile and eco-friendly approach for the synthesis of water-soluble WS2 quantum dots?QDs?was developed via ultrasonication and a hydrothermal process from bulk WS2.In this strategy,the dispersity of bulk WS2 in aqueous phase was improved with the aid of a surfactant CTAB,which could shorten the exfoliation time and improve the exfoliation efficiency to form layered WS2 nanosheets.Through hydrothermal treatment,the nanosheets were further scissored into QDs with high quality.The QDs show excellent features with narrow size distribution,good water solubility,and stable fluorescence.We find that the fluorescence of WS2 QDs can be quenched by Fe3+ through photoinduced electron transfer,and a wide detection linear range for Fe3+ is acquired.It indicates that WS2 QD can be used as a "turn-off" probe for Fe3+.In the presence of lipoic acid?LA?,the fluorescence was recovered due to the stronger interaction between LA and Fe3+ than WS2 QDs.A "turn-on" sensor for LA was developed with a linear range from 1 to 10 ?M and a detection limit of 0.59 ?M.The strategy might be suitable for the facile synthesis of other water-soluble transition metal dichalcogenide QDs.It is expected that the water-soluble QDs have great potential applications in biological system.Chapter 3 Ultrasmall Fluorescent Black Phosphorus Quantum Dots as Label-free Sensing probes for Evaluation of Acetylcholinesterase ActivityIn this chapter,a fast,sensitive and label-free fluorescence sensing platform for evaluation the acetylcholinesterase?AChE?activity and screening enzyme inhibitors has been developed based on the inner filter effect?IFE?between black phosphorus quantum dots?BP QDs?and 2-nitro-5-thiobenzoate anion?TNB?.BP QDs were successfully synthesized from bulk BP through a facile top-down route by sonication-assisted solvothermal method.5,5'-Dithiobis-?2-nitrobenzoic acid??DTNB?,as well-known Ellman's reagent,can react with thiol groups to form TNB.Based on the IFE between BP QDs and TNB,a sensitive and label-free sensing platform was developed for fluorescent measurement of thiols.As a proof-of-concept application,the platform was further applied in the evaluation of AChE activity and screening its inhibitors by using acethylthiocholine as substance.Chapter 4 Fluorescence Polydopamine Dots-based Sensor for the Detection of Copper Ions.In this chapter,a facile and novel strategy for the synthesis of fluorescent poly dopamine dots was developed utilizing coordination effect of Cu²⁺/H2O2,in which Cu²⁺ could act as an oxidant to oxidize the dopamine and Cu²⁺/H2O2 could produce the reactive oxygen species?ROS?to trigger the polymerization of dopamine.In addition,a highly sensitive and selective assay for the detection of Cu²⁺ was established with the linear range from 0.05-3 ?mol/L and the LOD is 0.00476 ?mol/L.