The Study Of Stripping Voltammetry Analysis Of Mercury Ions At Graphene-modified Electrodes

Inorganic mercury ions are well-known toxic heavy metal ions that are biodegradable.Once ingested with mercury ions,it will accumulate in the human body,causing poisoning,disease and even death.Therefore,the technical requirements for detecting Hg²⁺are precise and should reach trace levels.In addition to sensitive spectroscopy techniques,stripping voltammetry in electrochemistry is also a highly selective and sensitive method for detecting Hg²⁺.In the process for detecting Hg²⁺by stripping voltammetry,the most critical step is preconcentration,which need excellent electrode material to enhance its effect besides the appropriate deposition potential.Graphene oxide,a material that has been active in the electrochemistry for many years,can also be used as electrode material for detecting Hg²⁺by stripping voltammetry.In this work,we have achieved superior performance in the stripping voltammetric analysis of Hg²⁺by treating and doping graphene oxide.The main contents are as follows:?1?Graphene oxide?a-GO?prepared by the modified Hummers is composed of two components,namely a slightly oxidized graphene sheet and highly oxidized debris?OD?that can be removed by base washing to obtain bw-GO.Bw-GO can expose more active sites that deposit Hg²⁺,which can improve the stripping voltammetric analysis behaviour of Hg²⁺.The experimental results show that bw-GO/GC exhibits better performance than a-GO/GC for detecting Hg²⁺,such as higher sensitivity,wider linear range and lower detection limit.?2?To improve the performance of graphene oxide in stripping voltammetry for Hg²⁺,we adopted a method of chemical doping into graphene oxide.Among these heteroatoms,the N stands out due to its considerable size and five valence electrons which can be stably doped into graphene sheets.We obtained RGO and NRGO by calcining GO within N2 and NH3,which are applied as electrode materials for detecting Hg²⁺.Since the N of NRGO can complexate with Hg²⁺,NRGO/GCE will obtain better preconcentration effect.Results found that NRGO/GCE did have better response to Hg²⁺comparing with RGO/GCE,with higher sensitivity and lower detection limit.The applicability of NRGO/GCE has also been evaluated,including good selectivity,repeatability and reproducibility.The result of testing in lake water by NRGO/GCE is also satisfying.