Fabrication Of Novel Fluorescence Sensor System Of Nanoclusters And Its Application Of Detection Of Pollutant

Noble metal nanoclusters（NCs）are a new type of inorganic nano materials with particle size about 2 nm,which are composed of several to hundreds of metal atoms.The NCs mainly include gold nanoclusters（Au NCs）,silver nanoclusters（Ag NCs）and gold silver nanoclusters（AuAgNCs）.The free movement of electrons is restricted when the size of the material is close to the electron Fermi wavelength,which can lead to the division of energy level and the emission of fluorescence.Therefore,NCs are a new type of fluorescent materials.Compared with other typical quantum dots of lead and cadmium,NCs have some advantages,such as,low toxicity,stable optical properties and good biocompatibility.These advantages make NCs have been developed rapidly as fluorescent probes,such as the determination of small molecule pollutants mercury ions and organophosphorus pesticides（OP s）.At present,although NCs were widely used,there are some disadvantages of them,such as low luminous efficiency and weak stability.In this paper,in order to further improve the luminous efficiency of NCs and avoid the interference on the signal of single NCs probe from environmental fluctuation,a serious of highly sensitive and stable fluorescent biosensors based on NCs were prepared for the determination of ACh E and O Ps.In Chapter 2,AuAg nanoclusters（AuAgNCs）with high fluorescent were synthesized.The fluorescence of the AuAgNCs was quenched by thiocholine（TCh）,a product of the catalytic hydrolysis of acetylthiocholine（ATCh）by ACh E.In the presence of paraoxon of OPs（a ACh E inhibitor）,the catalytic hydrolysis of ATCh was blocked,which leads to the fluorescence of the AuAgNCs retained to some degree.Based on this mechanism,the AuAgNCs with high fluorescence was used to detect the ACh E and ACh E inhibitors.Under the optimal conditions,the linear range of this method for ACh E was 0.4-25 m U/m L with the limit of detection（LOD）of 0.15 m U/m L,which is better than the previously reported.For detection of paraoxon,the corresponding IC₅₀ was estimated to be1.9 ng/m L.This method was also utilized to detect the paraoxon in apple samples successfully.This study provides a new selective and sensitive fluorescent assay for determination of ACh E activity and ACh E inhibitor,and expands the application of AuAgNCs in biological analysis.Luminescent NCs have attracted much attention because of their good photostability and low toxicity,however,the low quantum y ield is still a deficiency,and many increasing efforts are being devoted to enhance the luminescence intensity of NCs.In Chapter 3,a method of enhancing the fluorescent signal of gold-silver nanoclusters（AuAgNCs）by photonic crystals（PhCs）was propose d.The fluorescent intensity of AuAgNCs on PhCs can be enhanced of 8.0-fold in comparison to the control sample without PhCs.Furthermore,a novel fluorescence sensor of AuAgNCs based on PhCs is used for the sensitive and selective detection of Hg²⁺ion in the aqueous solution.Due to the enhancement effect for the fluorescence which was caused by PhCs,the LOD is 0.35 nmol/L.This proposed method may not only develop a highly sensitive method for determination of Hg²⁺ion,but also expand the application of AuAgNCs in ultra-traceanalysis.Ratiometric fluorescent sensors are powerful tools for quantitative analysis.In Chapter 4,a ratiometric fluorescence sensor was fabricated by the combination of Au NCs and fluorescein（FL）,and the photonic crystal（PhCs）was used to selectively enhance the fluorescent intensity of Au NCs.This fluorescence sensor was used for the sensitive detection of ACh E and its inhibitor of paraoxon.ACh E can catalyze the hydrolysis of ATCh to form the TCh,which can induce the fluores cence quenching of Au NCs while having no obvious influence on the fluorescence intensity of FL.The ACh E can be determined in the ranges from 0.1 to 25 m U/m L with a LOD of 0.03m U/m L,and the paraoxon can be determined in the range of 0.06 to 60 ng/m L with a LOD 0.025 ng/m L.This method,as a new sight to selectively improve the fluorescence signal of one of the fluorephore in the ratiometric sensor,would be a great strategy for sensitive determination of the ACh E and its inhibitor.As a new type of quantum dots,tungsten disulfide quantum dots（WS ₂-QDs）have some advantages of simple synthesis and stable luminescence properties.In Chapter5,WS₂-QDs with blue fluorescence were synthesized by using reduced glutathione（GSH）as ligand,and the AuAgNCs were fabricated by 11-Mercaptoundecanoic acid（MUA）as reducing and protecting agents.The NCs/QDs ratiometric fluorescent sensor was constructed by mixing the two styles of fluorescent probe.This nano sensor can be used to detect the concentration of Cu²⁺ions,in which the fluorescence of QDs does not change significantly,while the fluorescence of NC s can be quenched by Cu²⁺ions.The sulfhydryl group of TCh has closely chelated ablity to Cu²⁺ions,which can hinder the quenching effect of NCs caused by Cu²⁺ions.By using the amplification effect of Cu²⁺,the sensor can indirectly measure the activity of ACh E and the concentration of paraoxon.It is expected to provide an effective reference for the development of methods to detect the AChE and OPs with highly sensitive and highly stable...