Preparation Of Gold Nanomaterials And Their Analytical Applications

In the field of nanomaterials,the research on the preparation and properties of gold nanomaterials is prevalent,which is one of the most discussed topics.Fluorescent gold nanoclusters（Gold nanoclusters,AuNCs）are a novel nanomaterial with unique optical properties.AuNCs with ultral-small size less than 2nm and have group protection and precise number of atoms.However,gold nanoparticles（Gold nanoparticles,AuNPs）possess photoelectric properties,biological affinity and the surface plasmon resonance effect etc.,which show the potential application value of AuNPs in the research field of biochemical colorimetric analysis.But the structure of AuNCs and AuNPs is completely different.AuNPs adopt the face-centered cubic structure,while Au NCs do not.In this paper,we have synthesized three kinds of gold nanometer material and studyed the method of preparation and the application of detection and analysis.The main contents are as follows:1.Using the degradation product of cefotaxime sodium（DCTX）as a protectant and reducing agent to synthesize water-soluble gold nanoclusters（named as AuNCs@DCTX）,AuNCs@DCTX can emit blue fluorescence at the excitation wavelength of 321 nm.In this chapter,the properties of AuNCs@DCTX are studied,including particle size,stability and quantum yield etc.The results show that water-soluble AuNCs@DCTX has high selectivity and sensitivity to Cu²⁺ions.In addition,we further carried out a series of experiments to study the mechanism of AuNCs@DCTX for determination of Cu²⁺using some common techniques,such as fourier infrared spectrum（FTIR）,fluorescence spectra,UV-Vis absorption spectra（UV-Vis）,high resolution electron microscopy（HRTEM）and X ray diffraction（XRD）.The fluorescence intensity of AuNCs@DCTX is dramatically decreased when Cu²⁺ions are added.The possible reason is due to a complexation of Cu²⁺and DCTX on the surface of AuNCs.Based on this principle,the fluorescence sensing system was established to determine the Cu²⁺content in several herbal samples.2.A gold nanocluster（named as AuNCs@APAP）has been prepared using acetaminophen（APAP）as a protectant and reductant,which can emit yellow fluorescence at the excitation wavelength of 303 nm.In this chapter,the properties of AuNCs@APAP are studied,including particle size,stability and quantum yield etc.The results show that water-soluble AuNCs@APAP has high selectivity and sensitivity to Fe³⁺.In addition,we further carried out a series of experiments to study the mechanism of AuNCs@APAP for determination of Fe³⁺using some common techniques,such as FTIR,fluorescence spectra,UV-Vis,HRTEM and XRD.According to the study,adding suitable amount of Fe³⁺can result in the agglomeration of Au NCs@APAP and the fluorescence quenching,then adding the ppi,Fe³⁺-ppi composite was stable due to strong coordination reaction between Fe³⁺and ppi,so that the fluorescence has been restored to a certain extent.Therefore,Au NCs@APAP can also be used to determine ppi.Hence,AuNCs@APAP as fluorescence sensor can be used for successive detection of Fe³⁺and ppi simultaneously.In addition,the method has high accuracy and selectivity in detecting iron ions in the water and ppi in serum.3.The last part is the synthesis of Au NPs with 13 nm using sodium citrate method.A simple and sensitive AuNPs colorimetric method was established for detection of cefotaxime sodium（CTX）.CTX in alkaline medium can be degraded into the same molar mass of sulfhydryl compounds（DCTX）using boiling water bath.Due to the surface plasma resonance effect（SPR）,the sulfhydryl compounds can easily form Au-S with AuNPs and be modified on the surface of AuNPs,leading to the aggregation of AuNPs with color changes from red to purple or blue.In addition,the proposed method was used to determine CTX in actual sample milk,saliva and urine.