The Synthesis Of Fluorescent Silver Nanoclusters And Application In Sensing Detection

In recent years,silver nanoclusters（Ag NCs）have attracted the attention of many researchers due to their good physical,chemical,optical and electrical properties.Especially the excellent luminescent stability,good water solubility,good biocompatibility,large Stokes shift and high emission efficiency,Ag NCs are a research hotspot in the analytical sensing field at present.In this thesis,the fluorescent silver nanoclusters（Ag NCs）were synthesized successfully by reflux method using different capped ligand,including N-acetyl-L-cysteine（NAC）,3,4-dihydroxy-L-phenylalanine（DOPA）,and Sodium 2-Mercapto-5-benzimidazolesulfonate Dihydrate（MBISA）.Based on different sensing mechanisms,the fluorescence sensing detection methods of tetracycline（TC）,pyrophosphate（PPi）and copper ion(Cu²⁺)were constructed respectively.The main task as follows:1.The silver nanoclusters（Ag NCs）with aggregation-induced emission property（AIE）were synthesized successfully by reflux method using silver nitrate（Ag NO₃）as raw material and N-acetyl-L-cysteine（NAC）as the reductant and capped ligand.The obtained Ag NCs possessed the special Ag（0）@Ag（I）–SR core-shell structure.The Ag NCs exhibited strong green luminescence with an optimal emission wavelength of 494 nm,high quantum yield of 44%and microsecond long life of 11.07μs.In addition,the obtained Ag NCs were used to detect the tetracycline（TC）with the range of linearity from 1.12 to 230μmol/L and the detection limit of 0.47μmol/L on account of the quenching mechanism of the internal filtration effect（IFE）and the static quenching effect between tetracycline and Ag NCs.This method had been applied to detect tetracycline concentration reliably and accurately in actual sample milk.2.The silver nanoclusters（Ag NCs）were synthesized successfully by reflux method using 3,4-dihydroxy-L-phenylalanine（DOPA）as the reductant and capped ligand.The single-factor controlled variable method was used to determine the optimal conditions for the synthesis of Ag NCs by fluorescence spectrometry.The molar ratio of DOPA to Ag NO₃ was 3:1,the reflux temperature was 80℃,and the reflux time was 24 h.The properties of the synthesized DOPA@Ag NCs were characterized by ultraviolet spectrum,fluorescence spectrum,infrared spectrum,transmission electron microscope and XPS spectrum.The prepared DOPA@Ag NCs had a quantum yield of3.5%.The Ag NCs had the advantages of good water solubility,strong photobleaching resistance and good stability.Based on the fluorescence static quenching mechanism of DOPA@Ag NCs by PPi,a highly selective and sensitive fluorescence method was established to detect PPi.The linear range was 0.08-0.94μmol/L,and the detection limit was 1.36 nmol/L which was much lower than other PPi detection methods.In addition,the DOPA@Ag NCs nanomaterials had been successfully applied to the detection of PPi in toothpaste samples.3.The silver nanoclusters（Ag NCs）were synthesized successfully by reflux method using Sodium 2-Mercapto-5-benzimidazolesulfonate Dihydrate（MBISA）as the capped ligand and ascorbic acid（AA）as the reducing agent.The optimal reaction conditions for the synthesis of MBISA@Ag NCs were investigated.The ratio of MBISA to Ag NO₃ was 8:1,the reflux temperature was 60℃,and the reflux time was 10 h.The optimal emission wavelength(λ_em)was 520 nm at a maximum excitation wavelength(λ_ex)of 340 nm.Based on the mechanism that the surface groups on MBISA were highly coordinated with Cu²⁺,the as-synthesized MBISA@Ag NCs can be used to construct sensing system for Cu²⁺detection.The linear range was0.04-30μmol/L,and the detection limit was 5.77 nmol/L.Besides,the constructed Cu²⁺sensing detection method was successfully used for the detection of Cu²⁺in tap water,lake water,and fish pond water samples.