Synthesis Of Amino-Acid Modified Gold Nanoparticles And Detection Of Malachite Green By SERS Spectrum Method

With the increase of organic pollutants and contaminated food,environmental problems are receiving increasing attention.Malachite green（MG）,as a common organic pollutant in aquaculture,has been abused in aquatic products because of its high efficiency and low cost.Therefore,the development of rapid and highly sensitive methods for the analysis of malachite green is essential to prevent the illegal use of this chemical.At present,the analytical methods used for the detection of malachite green,such as high performance liquid chromatography（HPLC）,liquid-mass separation（LC-MS）,electrochemical method,etc.,have good precision and accuracy.But these methods have some disadvantages such as high cost,difficult operation and high energy consumption.And SERS spectral analysis method has the advantages of simple operation,low cost,instant detection and so on.So we have further investigated them.Surface-enhanced Raman spectroscopy（SERS）,an analytical technique with high surface sensitivity,can directly provide information of various target molecules at very low concentrations or even at the level of single molecules.Due to the high performance of probe molecules and non-label detection,SERS has great application prospect in biosensing,food safety,environmental monitoring and other fields.In addition,SERS technology also has the advantage of enhancing the intensity of Raman signal,which is mainly amplified by the interaction between the electromagnetic field generated by plasma nanoparticles and the vibration mode of analyte,which is in close contact with nanoparticles.As a result,the plasma coupling between very close nanoparticles generates large electric fields at interparticle junctions,known as“hot spots”.When the molecule is close to the hot spot,its Raman signal is significantly enhanced.Due to the advantages of structural stability and high biocompatibility of gold nanoparticles,good stability and strong affinity of amino acids,malachite green was analyzed and detected by SERS spectrum based on the aggregation response of gold nanoparticles modified by amino acids.Based on the above contents,this paper mainly carried out two parts of work:In the first part,amino acid modified gold nanoparticles（Au NPs）were prepared.Based on the aggregation response of Au NPs caused by the coordination of amino acids and metal ions,a SERS spectral method was established for quantitative analysis and detection of crystal violet using the controlled aggregation of His-Au NPs synthesized by Al³⁺.In this study,gold nanoparticles were successfully synthesized by sodium citrate reduction method and functionalized by histidine（His）ligand.Since our ligand His has a strong coordination effect on Al³⁺,after adding Al³⁺,the functionalized Au NPs get close to each other and form an aggregation state,resulting in a strong near-field interaction coupling single plasma oscillation,which affects the electric field distribution around the nanostructure and forms the so-called“hot spot”.Then we added Raman signaling molecules on the basis of amino acid modification of Au NPs.When molecules are close to regions with high electric field hot spots,their Raman signals are significantly enhanced.Therefore,we make use of Al³⁺concentration changes to enhance the Raman signal of molecules to different degrees.The corresponding relationship between the sensitivity and the linear range is shown,which indicates that the material has good analytical performance.In the second part,this paper constructs the SERS spectral quantitative analysis and detection method using His-Au NPs/Al³⁺for MG.The specific content is to first use the synthesized SERS base to conduct SERS detection on MG standard solution,and make its corresponding standard curve.After that,high,medium and low concentrations of Al³⁺were added into the synthesized functional nanomaterials to aggregate gold nanoparticles into different aggregation states,which led to the SERS signal of MG forming a difference between high,medium and low,and three standard curves were obtained.The results showed that His-Au NPs had high sensitivity to the detection of MG after adding high concentration of Al³⁺,but the linear range was narrow.After adding low concentration of Al³⁺,the sensitivity of His-Au NPs to the analysis and detection of MG was low but the linear range was relatively wide,which proved that the requirement for SERS detection of MG in different concentration ranges could be realized by controlling the concentration of Al³⁺.We also investigated the analytical performance of the synthesized SERS base.The experimental results showed that the functionalized nanomaterial had good reproducibility and anti-interference ability,which proved that a simple,sensitive,controllable and efficient sensor for the analysis and detection of veterinary drug MG was successfully constructed.We further conducted SERS detection on actual environmental samples.The experimental results show that the method has good sensitivity,reproducibility and selectivity,strong anti-interference ability and high practicability,and can be effectively applied to the detection requirements of various substances in different concentration ranges.In addition,the material and its aggregation response based on metal nanoparticles can play an important role in many fields,such as environmental monitoring,and have great application prospects.