Synthesis Of Histidine Protected Metal Nanoclusters And Chemical Sensing Application

Metal nanoclusters（MNCs）are emerging types of luminescent nanomaterials in recent years.Compared with traditional organic dyes and semiconductor quantum dots,MNCs have many advantages,such as easy preparation,good stability,excellent luminescence performance,ultra-small size and low toxicity.MNCs as a new optical sensing material that replaces organic dyes and quantum dots,it has been extensively researched in biochemical sensing and fluorescence imaging.In this thesis,a series of new luminescent MNCs were synthesized using biomolecular histidine as ligand,including Au NCs,Ag NCs,Cu NCs and Au Cu NCs.Based on the mechanism of fluorescence intensity change（quenching/ enhancement）,chemical sensors for the determination of tetracycline,p H and picric acid were constructed.Chapter 1:The preparation,spectral properties and analytical applications of MNCs were reviewed.With reference to literature analysis,the design ideas of this thesis were proposed.Chapter 2:Fluorescent Au NCs and Ag NCs were synthesized by one-pot method using biomolecular histidine as ligand and mixing histidine and HAu Cl₄/AgNO₃ solution at room temperature.A facile,simple,mild and environment friendly preparation method was proposed.The Au NCs and Ag NCs were characterized using UV-Vis,fluorescent,IR spectrometry and TEM,XPS.The fluorescence sensors for the detection of tetracycline with high sensitivity and selectivity was successfully constructed.The detection ranges using Au NCs and Ag NCs were 0.002-936 μmol·L^-1 and 0.0005-335 μmol·L^-1,respectively.And the detection limits were 1.35 nmol·L^-1 and 0.46 nmol·L^-1,respectively.In addition,the Au NCs and Ag NCs fluorescent probes have been applied in trace detection of tetracycline in milk.Chapter 3 : The green fluorescent copper nanoclusters（His@Cu NCs）were synthesized by microwave-assisted heating using Cu（NO₃）₂ and histidine as precursor.The as-prepared His@Cu NCs were spherical and uniformly dispersed with the particle size of1.6 ± 0.5 nm.Based on the sensitive response of His@Cu NCs to p H value,a reversible p H sensing system was successfully established.In different buffer solutions,the fluorescencesensing intensity of His@Cu NCs increases with the increase of p H value,and exhibited a good linear relationship in the range of p H 5-10.The new sensing method of p H has been applied to the detection of p H in practical water sample with the relative error between-0.65% and 0.39%.In addition,His@Cu NCs had a good response to picric acid（PA）.The fluorescence intensity of His@Cu NCs was linearly quenched with PA concentration in the range of 3.68×10^-8-4.01×10^-4 mol·L^-1,and the detection limit was 1.26 n M.Moreover,inorganic salts,phenol,nitrobenzene,2,4,6-trinitrotoluene and other substances did not interfere in the detection of PA.The His@Cu NCs have been used in determination of PA in tap water and lake water.And the recovery was satisfactory with the range98.4%-102.7%.Chapter 4 : Compared with single metal materials,alloy materials have many excellent properties,such as improved fluorescence intensity,catalytic activity,stability and anti-interference ability.Therefore,it is of great significance to study the application of alloy nanoparticles.In this chapter,Gold-copper alloy nanoclusters（His-Au Cu NCs）were prepared with histidine as the stabilizer at a certain Au/Cu molar ratio.The His-Au Cu NCs have simple preparation process and good stability,and the fluorescence performance was superior than both His-Au NCs and His-Cu NCs under the same conditions.The prepared His-Au Cu NCs by microwave heating method have high selective recognition for picric acid（PA）.Based on the internal filter effect between the PA and the Au Cu NCs,the highly sensitive detection method of PA by Au Cu NCs was achieved.The detection range is 2.1×10^-10-5.2×10^-4 mol·L^-1 with the detection limit 0.05nmol·L^-1,and the response time is 1 min.His-Au Cu NCs have been successfully applied to the determination of picric acid in water samples with satisfactory recovery.Chapter 5:In this chapter,the metal nanoclusters（MNCs）as fluorescence sensors in the detection of small molecules and p H sensors were summarized in terms of fluorescence analysis,and the future work is prospected.