Preparation And Sensing Poperties Of Silver /Palladium/Gold Luminescent Nanoclusters

Metal nanoclusters?MNCs?are a new type of fluorescent nanomaterials.The size of MNCs is generally less than 2 nm.Due to its unique electronic structure and ultra-small size,it often displays unusual optical,electrical,and physics properties,and is widely used in the field of environmental pollutant monitoring,biochemical analysis,and medical analysis.MNCs synthesized with biomolecule amino acid as a ligand have low toxicity,are easily modified,and have good biocompatibility.So they have attracted much attention in the research field of MNCs in recent years.However,the simple and green method to synthesis MNCs must to be further developed to obtain nanocluters with small size,excellent properties and specific functions.To achieve this objective,we have developed a new method to synthesis water-soluble luminescent Ag NCs,Pd NCs and Au NCs by using methionine as ligand.And sensing properties of these nanoclusters were studied.1)Using AgNO₃ as metal precursor,methionine as a ligand,and ascorbic acid as reducing agent,water-soluble Ag NCs were synthesized.The Ag NCs emits blue fluorescence under a 365 nm UV lamp and the luminescence quantum yield is calculated about 10.06%.The average lifetime of Ag NCs is 3.02 ns.The average particle size of Ag NCs is about 1.74 nm.The experimental results indicate that the hemoglobin can selectively quench the fluorescence of Ag NCs.Based on this phenomenon,a new method for detecting hemoglobin has been established.The hemoglobin concentration in the range of 0.5?M-5?M shows a good linear relationship with the fluorescence intensity of Ag NCs.The detection limit is 65 nM.It has also been successfully applied to the analysis of actual blood samples with a satisfactory recovery.The results show that the method possess a high sensitivity,strong anti-interference ability,excellent selectivity,and good detection performance for hemoglobin in a relatively low and wide concentration range.2)Using?NH₄?₂PdCl₄ as metal precursor,methionine as a ligand,and ascorbic acid as reducing agent,water-soluble Pd NCs were synthesized.The Pd NCs emits blue-green fluorescence under a 365 nm UV lamp and luminescence quantum yield is calculated about 5.47%.The average lifetime of Pd NCs is 1.27 ns.The average particle size of Pd NCs is about 1.91 nm and the topographic height is less than 2.5 nm.It is found that the fluorescence of Pd NCs can be quenched selectively by the hemoglobin.Based on this phenomenon,a new method for detecting hemoglobin has been established.The response time of the Pd NCs to hemoglobin is rapid.Within approximately 0.6 s,the quenching of the Pd NCs by hemoglobin reached equilibrium.The hemoglobin concentration in the range of 0.25?M-3.5?M shows a good linear relationship with the fluorescence intensity of Pd NCs.The detection limit is 50 nM.It has also been successfully applied to the analysis of actual blood samples with a satisfactory recovery.The results show that the method has a merit of effectiveness and possesses a high sensitivity,strong anti-interference ability,excellent selectivity,and good detection performance for hemoglobin in a relatively low and wide concentration range.3)Using HAuCl₄·3H₂O as metal precursor,methionine as a ligand,and ascorbic acid as reducing agent,water-soluble Au NCs were synthesized.The Au NCs emits orange fluorescence under a 365 nm UV lamp and the luminescence quantum yield is about 1.46%.The average lifetime of Au NCs is 217.74 ns.The average particle size of Au NCs is about 1.80 nm.In addition,we have explored the application field of Au NCs.The fluorescence imaging of MCF-7 cells is achieved.Simultaneously,it is found that the Cd²⁺can selectively enhance the fluorescence of Au NCs.Based on this phenomenon,a new method for detecting Cd²⁺has been established.The response time only needs 1 min for the above method.Meanwhile,the method has strong anti-interference ability and good selectivity.The linear responses over the Cd²⁺concentration range from 0.05?M to 35?M and the limit of detection is determined to be 12.25 nM.Moreover,it is also applied to analysis actual water samples and milk powder samples with a satisfactory recovery.The test results are close to those obtained by ICP-OES,which indicates that Au NCs are expected to play a greater role in the practical application of sensing Cd²⁺.