Preparation,Optical Properties And Applications In Detection Of β-Cyclodextrin-Derived Carbon Dots And Their Hybrid Assemblies

Among numerous nanomaterials,carbon dots（CDs）as a category of promising fluorescent nanomaterials have attracted tremendous attention increasingly since their identification by Xu and co-workers in 2004.In addition,CDs are considered to be fascinating and versatile for their diverse applications in fluorescence sensor,photocatalysis,nanomedicine,cellular imaging and printing ink,etc.The above facts are in view of exceptional features of CDs such as low toxicity,size-tunable emission,superior-photostability,easy preparation,biocompatibility,excellent water-solubility,and high sensitivity towards targets.Moreover,some stabilizing agents or functional molecules,which can decorate the surface of CDs,can protect the luminescence properties and enhance their dispersion stability of CDs in aqueous solution.But beyond that,certain of specific surface modifications of CDs further endow them with stronger affinity with target analytes.In this thesis,a kind ofβ-cyclodextrin derived carbon dots（β-CD-CDs）were developed as a simple and efficient sensor towards 2,4,6-trinitrophenol（TNP）with high selectivity and sensitivity.And based on theβ-cyclodextrin molecules on the surface ofβ-CD-CDs,theβ-CD-CDs were attached to the azobenzene-terminated block copolymer micelles encapsulated red-light CdSe/ZnS QDs via host-guest interaction,and the as-constructed hybrid assembly exhibited dual emission peaks centered at 450 and 620 nm upon the excitation at 360 nm,and can be utilized as a ratiometric fluorescent probe to realize a highly selective detection of Hg²⁺and Cu²⁺.The detailed content includes:（1）A novel carbon dots with a large number ofβ-CD molecules on their surface were synthesized usingβ-CD as a carbon source via a facile hydrothermol method.The obtainedβ-cyclodextrin derived carbon dots（β-CD-CDs）exhibited a blue-green emission centered at450 nm upon the excitation at 360 nm,and the emission peak position gradually red-shifted with increasing excitation wavelength,indicating an excitation-dependent fluorescence property.The fluorescence quantum yield of theβ-CD-CDs was determined as 16%.In the presence of trace TNP,the fluorescence ofβ-CD-CDs could be quenched substantially.Therefore,the CDs can be used as a fluorescent probe for the trace detection of TNP with a detection limit down to 1.9μM.（2）A novel ratiometric fluorescent probe is constructed by coupling blue-green emissionβ-cyclodextrin derived carbon dots（β-CD-CDs）to a polymeric micelle encapsulated red-emission CdSe/ZnS QDs through host-guest interaction.A novel amphiphilic diblock copolymer AZO-PNIPAM-b-P（St-co-MQ）containing azobenzene（AZO）-terminated hydrophilic poly（N-isopropylacrylamide）（AZO-PNIPAM）block and hydrophobic polystyrene（PS）block was synthesized by a typical RAFT polymerization.The5-（2-methacryloylethyloxymethyl）-8-quinolinol（MQ）units were also introduced into PS block,which can make CdSe/ZnS QDs to be embeded into the core of the diblock polymer micelles via strong coordination interaction of MQ units in the self-assembling process.The as-fabricatedβ-cyclodextrin derived CDs-coupled block copolymer hybrid micelles loaded with CdSe/ZnS QDs exhibited dual emission peaks of CDs centered at 450 nm and CdSe/ZnS QDs at 620 nm upon excitation at 360 nm.And the as-prepared hybrid micelles as a ratiometric fluorescence probe can be used for highly selective detection of Hg²⁺and Cu²⁺with the detection limits down to 1.6 and 2.74μM,respectively.