Preparation Of Silver Nanomaterials And Application For Visual Detection

With the vigorous development of metallurgy,electroplating,mechanical processing,heavy metal chemicals and other industries,the pollution problem of heavy metal elements has become increasingly serious.It is important to develop a rapid,convenient,highly selective and ultra-sensitive method for the detection of trace heavy metal ions.In recent years,more and more attention has been paid to the naked eye colorimetry,which can be detected quickly without any advanced instruments.Scientists have developed a number of naked-eye colorimetric methods based on precious metal?Au,Ag?nanoparticles for chemical analysis and promoted advances in nanotechnology.Due to its unique physical and chemical properties,functional precious metal NPs can enhance signal strength,facilitate signal readout,and greatly improve analytical performance.Scientists have found that precious metal nanostructures of the desired shape and size can be prepared,so that the properties of nanomaterials can be subtly customized and control the size and shape of nanomaterials,which can control the application of nanocrystals to some extent.Nanomaterials made of Ag are particularly attractive because they not only have variable properties,but also have stronger plasma properties and anisotropy than other materials.Therefore,the controlled synthesis of Ag nanocrystal structures is critical for the development of highly sensitive chemical sensing and biological detection.In view of this,based on the previous research work,this dissertation is devoted to the regulation of the morphology of silver nanomaterials.Based on this,a series of experiments based on silver nanomaterials for visual detection of heavy metal ions have been carried out.1.In this work,we found an effective domino effect-based detection mechanism for the rapidity,high selectivity and ultrasensitivity naked-eye colorimetric ratio assay of chromium???ion(Cr³⁺)in aqueous solutions.This naked-eye colorimetric ratio assay to Cr³⁺relies on changes in absorbance properties caused by the stimuli-responsive of Cr³⁺for morphology transformation of silver nano flakes.In the presence of Cr³⁺,large silver nano flakes can be stimulated to transform into small nanoparticles?NPs?,which promoted a color change of the solution from bright yellow to wine red.The proposed naked eye sensing strategy coupled with UV-spectroscopic chemosensor was used to detect trace Cr³⁺.It is expected to have great potential and wide application in drug analysis,clinical diagnosis and environmental monitoring.2.It was first discovered that metal ions can be used to induce self-assembly of disordered silver nanoparticles into silver nano-secondary structures.Citrate-coated Ag spherical nanoparticles were prepared,which were first grow into small Ag nanoparticles as a seed solutions.Adding trace amounts of metal ions to a solution of small Ag nanoparticle seeds can grow into large silver nanoscale secondary materials within minutes.In addition,the self-assembled Cr³⁺@Ag NPs silver nano-secondary material were used as mimetic peroxidase for selective and ultrasensitive detection of Hg²⁺in aqueous solutions.In the presence of mercury ions,it was found that the peroxidase-like activity of Cr³⁺@Ag NPs silver nano-secondary materials was significantly stimulated and enhanced,which promoted the effective oxidation and color change of 3,3?,5,5-tetramethylbenzidine?TMB?in solution.was the color change of dark blue can be detected by the naked-eye and the absorption spectroscopic,which is more stable than other morphological secondary materials and provides the best UV spectral signal,which is expected to have application prospects in biological detection and pharmaceutical analysis fields.3.A visual array sensor based on silver nanomaterials was constructed,which can detect seven heavy metal ions and correspond to seven color changes.Sensor arrays were constructed using three different concentrations of silver nanocolloids,which brought a unique chromaticity reflection patterns for seven heavy metal ions.A linear discriminant?LDA?analysis mode was used to identify seven metal ions(Ni²⁺,Mn²⁺,Co²⁺,Cd²⁺,Cu²⁺,Pb²⁺,Cr³⁺).This method enables simple,fast?within 30seconds?visual identification of metal ions,showing potential applications in environmental pollutants and heavy metal ion monitoring.