Preparation Of Carbon Quantum Dots Functionalized Gold Nanoparticles And Its Application In Visualization Analysis

The eye is the source of our knowledge and information,it is the window of the soul and can distinguish complex colors and different wavelengths of light.In analytical methods,we generally use mass spectrometry,atomic absorption spectrometry,fluorescence spectroscopy,inductively coupled plasma mass spectrometry,atomic emission spectrometry,and other analytical techniques to detect heavy metal ions.However,these analytical methods generally require intensive and complex analytical procedures.Therefore,how to establish simple,fast,sensitive,efficient and stable detection method becomes the focus of the scientists.Based on this,we have developed a series of methods for visual detection of metal ions by using the excellent optical,magnetic and catalytic properties of noble metal nanoparticles.Currently,the main detection methods of heavy metal ions visualization is divided into two kinds,one kind is based on visual sensor no enzyme or DNA enzyme,the application of functional metal nanoparticles?Gold nanoparticles?ligands on the surface of the real-time,fast detection of Cd²⁺and Cr³⁺ions.The other kind is based on the simulated activity of stimulating enzyme,which can oxidize and change the color of substrate?TMB?and realize quantitative analysis and detection of metal ions?Ag⁺?.This thesis is mainly introduced in the following aspects:?1?Using graphitic graphite-like carbon nitride quantum dots?g-CNQDs?as modifying functional groups,the stable and uniform Au@g-CNQDs nanoparticles synthesized by the aqueous phase method can be used for rapid and sensitive detection of Cd²⁺ions.In the experiment,g-CNQDs were used as probes to identify the groups,which can coordinate with Cd²⁺ions to form gold nanoclusters.The qualitative and quantitative analysis of Cd²⁺ions was achieved through solution color change and UV-visible absorption spectrum changes,respectively.The absorption peak of gold nanoparticles at 520 nm in the UV-vis absorption spectrum decreases,and a new absorption peak appears at 650 nm.At the same time,the color of the solution changed from burgundy to blue-gray,creating a new method for visual detection of Cd²⁺ions with a detection limit of 10 nM.In addition,Au@g-CNQDs nanoparticles were used to biologically stain mouse tissues and quantitatively analyze the distribution of Cd²⁺ions in mouse models.?2?The colorimetric detection of trivalent chromium was carried out using sulfur-doped graphite-like phase carbon nitride quantum dots?S-g-CNQDs?-modified gold nanoparticles.It was found that due to the metal coordination of the functional groups of S-g-CNQDs ligands modified on the gold nanoparticles surface,the trivalent chromium ions can induce the aggregation of the gold nanoparticles,causing the spectral changes and accompanied by the color change of the solution.The gold nanoparticles changes from purple to light gray,and finally realizes visual detection of Cr³⁺ions.There was a good linear relationship between the absorbance ratio of Au@S-g-CNQDs system(A₇₀₀/A₅₅₀)in the range of 0.05¹.8?M and the detection limit of this method was 78 nM.In addition,this method was successfully applied to the detection of trivalent chromium ions in tap water and campus lake water.?3?We have established a simple,fast,highly selective,ultra-sensitive method for visual detection of Ag⁺ions.In the citric acid-disodium hydrogen phosphate buffer system,Hg⁰ deposits on the surface of AgNPs to form silver amalgam.The newly formed silver amalgam can change the physical and chemical properties of the surface of nanoparticles and promote the decomposition of hydrogen peroxide molecules to form high activity efficiently hydroxyl radicals,hydroxyl radicals can oxidize TMB,losing one electron to dark blue,enabling visual detection of Ag⁺ions.The instrument's?UV-vis?detection limit was 1 nM and the naked eye detection limit was86 nM.