Study On SERS Sensors For Trace Mercury Detection In Environmental Water

Mercury,a toxic heavy metal,itself and compounds can cause serious harm to natural environment and human health.Mercury ion remaining in environmental water is one of the main forms of mercury pollution,which is easily taken in by human.There is an urgent need to develop a highly sensitive and selective sensor for the detection of trace mercury ion in water.Surface enhanced Raman scattering(SERS)has been widely used in material identification and detection.SERS owns ultrahigh detection sensitivity and is an ideal tool for analysis of biological samples and chemical substances in water.The purpose of this thesis is to study and develop highly sensitive and selective SERS sensors for the detection of trace mercury ion in environmental water.First,a liquid phase SERS sensor for mercury ion is constructed based on SERS-active flower-like gold nanoparticles and oligonucleotide probes.Further,a SERS sensor chip for convenient and sensitive identification of mercury ion is also proposed.This thesis provides a reliable detection method for mercury ion in environmental water,promoting SERS practical applications of detection technology in the field of environmental water.The main research contents are as follows:(1)Construction and application of a SERS liquid phase sensor for detection of mercury ionA liquid phase SERS sensor is designed and proposed by assembling oligonucleotide probes onto flower-like gold nanoparticles.In this work,flower-like gold nanoparticles were synthesized first,and followed by modifying their surface with single stranded Raman dyes lablled thymine-riched oligonucleotides to construct the liquid phase SERS sensor.When dispersed in the liquid sample,SERS liquid phase sensors experienced a SERS signal decrease caused by exsied mercury ion.The experimental results indicate that the SERS liquid phase sensors can acheive sensitive detection of trace mercury ion with linear detection range of 1 nM-1000 nM.(2)Fabrication and application of SERS sensor chip for mercury ionA portable,ultrasensitive SERS sensorchip is proposed and utilized for detecting trace mercury ion in environmental water.The SERS sensor chip is prepared by immobilizing T-component oligonucleotide probes labeled with dye at the 3'-end and-SH at the 5'-end on an excellent sliver nanorods array SERS substrate.The oligonucleotide probes response to the specific chemical bonding between thymine and mercury ion,which causes the previous flexible single strand of oligonucleotide probe changing into rigid and upright double chain structure.Such change in oligonucleotide probes' structure drives the dyes far away from the SERS substrate and results in a SERS signal attenuation of the dyes.Therefore,by monitoring the decay of SERS signal of the dyes,mercury ion in water can be detected qualitatively and quantitatively.The experimental results indicate that the proposed optimal SERS sensor owns a linear response with wide detecting range from 1 pM to 1 ?M,and a detection limit of 0.16 pM was obtained.In addition,the SERS sensor chip demonstrates good specificity for Hg2+.The SERS sensor chip has been further executed to analyze the trace mercury ion in tap water and lake water respectively,and good detection recovery rates were obtained.With its high selectivity and good portability,the ultrasensitive SERS sensor chip is expected to be a promising candidate for discriminating mercury ion in the fields of environmental monitoring and food safety.