Study On Detection Of Heavy Metal Ions Based On Surface Enhanced Raman Spectroscopy

Heavy metal ions pose a significant threat to human health and the ecological environment.Heavy metals such as mercury ions(Hg²⁺)in water can enter the food chain through absorption by plants,leading to the accumulation of Hg²⁺in the human body,causing Hg²⁺poisoning and damaging the human nervous,kidney,immune,heart,motor,reproductive,and genetic systems;Excessive absorption of copper ions(Cu²⁺)by the human body can also lead to various diseases,such as anemia and Alzheimer’s disease.Therefore,simple,rapid,and sensitive methods for detecting heavy metal ions have attracted widespread attention.This paper designs a surface enhanced Raman scattering（SERS）sensor based on precious metals for the detection of Hg²⁺and Cu²⁺in water systems through complexation and etching reactions.The sensor has the characteristics of fast analysis speed,short response time,simple preprocessing,high sensitivity,low sample size,and rich fingerprint information,and can be widely used in trace analysis and non-destructive testing.The specific content is as follows:（1）In this paper,an Hg²⁺SERS sensor based on dithizone（DTZ）modified silver nanoparticles（Ag NPs）was investigated.SERS technology for detecting Hg²⁺is a hot topic in the field of SERS detection.Due to its strong chelating ability in orbital arrangement,Hg²⁺can be detected using chelation reactions.This chapter takes the synthesis of Ag NPs as the substrate and modifies DTZ molecules on its surface to form an Ag NPs-DTZ detection system.When Hg²⁺is added to the system,due to the complexation between DTZ and Hg²⁺,and the binding ability of Hg²⁺and DTZ is stronger than that of Ag NPs,DTZ originally adsorbed on the surface of Ag NPs is desorbed,far away from the hot spot area,and the SERS signal at 1590 cm^-1 belonging to DTZ is reduced.Under the optimal detection conditions,this detection method exhibits good Hg²⁺detection anti-interference and reproducibility and RSD is 4.3%.After conducting quantitative analysis,it was concluded that the logarithm of Hg²⁺concentration showed a good linear relationship with the value of I₀-I between 10^–4 and 10^–8 mol/L,with a detection limit（LOD）of9.83×10^–9 mol/L,which proves that this method has the characteristics of wide linear range and low detection limit.This sensor can be used for rapid detection of Hg²⁺in water samples,with characteristics such as low detection cost,fast detection speed,and simple sample pretreatment.It provides a new idea for the detection of Hg²⁺in actual water systems.（2）A method for detecting Cu²⁺using SERS technology based on etching reaction has been proposed.Cu²⁺as a type of heavy metal ion,poses a threat to human health if consumed excessively.When using SERS technology to detect Cu²⁺,due to its lack of Raman response,indirect detection is required.This chapter focuses on the synthesis of Au@Ag NPs core-shell structure serves as the detection substrate,mixed with the Raman probe molecule p-mercaptobenzoic acid（4-MBA）,and then added with I^-to form Au@Ag NPs-4-MBA-I^-testing system.When the detection system reacts with Cu²⁺,the Cu²⁺and I^-reactions form substances that can undergo etching reactions with the Ag shell layer,and the Ag shell layer gradually becomes thinner.There is a linear relationship between the thickness of the Ag shell and the Raman signal intensity,so the SERS enhancement effect is reduced,and the Raman signal intensity attributed to4-MBA at 1586 cm^-1 is significantly reduced.Under the optimal testing conditions,this detection method exhibits good Cu²⁺detection anti-interference and reproducibility and RSD is 3.9%.After quantitative analysis,it was found that this method has a wide linear range of 10^–9 to 10^–4 mol/L and a LOD of 1.108×10^–9 mol/L.This method has fast detection speed,low detection cost,and is environmentally friendly.It can be applied to the detection of Cu²⁺in tap water,and also has application value in other water systems.