Construction Of A New Type Of Carbon Nanomaterial Fluorescence Sensor And Its Analytical Application

Nano-sized carbon materials have special physical and chemical properties compared with larger carbon materials.The new fluorescent sensor is different from the traditional detection method,which is characterized by its small size,easy operation and high sensitivity.With the continuous innovation and development of science and technology,new fluorescence sensors based on carbon nanomaterials have been widely used in clinical diagnosis,environmental detection and food safety field.In this thesis,we have developed three kinds of fluorescence sensors based on carbon nanomaterials,which have been used for the detection of melamine,tyrosinase and silver ion,respectively.The main contents of this thesis are as follows:Chapter one:The relevant contents of carbon nanomaterials and fluorescent sensors are summarized.Chapter two:A simple,fast and economical melamine sensing platform was developed with carbon dots（CDs）as fluorescence probe.It was reported that mercury ion(Hg²⁺)could quench the fluorescence of CDs,and melamine was prone to coordinate with Hg²⁺due to the presence of a multi-nitrogen heterocyclic ring.Thus,the presence of melamine could inhibit the quenching ability of Hg²⁺towards CDs through decreasing the interaction between Hg²⁺and CDs.By this method,a detection limit of 0.3μM is obtained.In addition,this method can also realize the determination of melamine in the actual sample.Chapter three:A biosensing platform for the detection of tyrosinase activity（TYR）and its inhibitors was developed based on graphene quantum dots（GQDs）.The excitation and emission wavelength of GQDs are located at 383 nm and 445 nm,respectively.TYR can oxidize dopamine（DA）into a dopaquinone.Thus,fluorescence resonance energy transfer（FRET）between GQDs and dopaquinone could occur due to the spectral overlap between the absorption spectra of dopaquinone and the emission spectra of GQDs.Therefore,the activity of TYR can be quantitatively detected according to the fluorescence quenching efficiency.The detection limit can reach 0.0015 U m L^-1.Moreover,this method can also be used to screen the inhibitors of tyrosinase.Chapter four:A ratiometric fluorescent nanosensor was developed for the analysis of silver ions（Ag⁺）by employing graphene quantum dots（GQDs）as the reference fluorophore and o-phenylenediamine（OPD）as the specific recognition probe.OPD could be oxidized to 2,3-diaminophenazine（DAP）by Ag⁺,which emits strong fluorescence at a wavelength of 557 nm.However,DAP can quench the fluorescence of GQDs by fluorescence resonance energy transfer（FRET）.The fluorescence intensity ratio of DAP and GQDs increases with the increase of Ag⁺concentration within the range of 0-115.2μM.The detection limit can reach 250 nM.In addition,the sensor can be used to detect Ag⁺in actual water samples.