Study On Wireless Sensing And Resonance Light Scattering For The Determination Of Trace Lead And Cadmium In Water Environment And Application

Chapter 1:This chapter introduces the hygiene significance and the research status of the methods for the determination of trace lead and cadmium in water environment at home and abroad.The basic principles for the wireless magnetoelastic sensing method,the resonance light scattering technology and the basic concepts of the gold nanoparticle,functional nucleic acids?FNAs?were introduced.In addition,the basic principles and the quantitative analysis basis for the new wireless magnetoelastic methods and resonance light scattering method to detect trace lead and cadmium were also expounded.Chapter 2:A wireless magnetoelastic sensor?WMS?for lead detection has been developed using the specific recognition of FNAs and the sensitization effect of graphene oxide?GO?and the signal amplification effect of gold nanoparticles?Au NPs?.The magnetoelastic alloy material was made of Fe₄₀Ni₄₀P₁₄B₆ and covered a film of polyurethane?PU?modified with GO.In the presence of Pb²⁺,the substrate strand of FNAs was cleaved,the single-stranded DNA?ssDNA?was adsorbed onto the GO film of the WMS by?-?stacking interactions,resulting in a decrease of resonance frequency of the WMS.Then,in the presence of CTMAB,HAuCl₄ can be reduced by ascorbic acid?AA?to atom Au coated on AuNPs in big size on the surface of the sensor,leading to the second signal amplification.Under the best experimental conditions,the change value of resonance frequency correlated linearly with the concentration of Pb²⁺in the range of 4.8 to 95.2?×10^-99 mol/L?with a detection limit of 3.6×10^-99 mol/L.Chapter 3:The FNAs of cadmium(FNAs_Cd2+)could be adsorbed on the surface of the gold nanoparticles,which avoided the aggregation of gold nanoparticles under the high salt?NaCl?concentration,so,the resonance light scattering?RLS?intensity of the system was very weak without Cd²⁺.When Cd²⁺was added,the Cd²⁺would combine with FNAs_Cd2+to disengagement from the surface of gold nanoparticles,which would lose the protection for gold nanoparticles.Then,the gold nanoparticles would be aggregated under high salt concentration,which would result in the enhancement of resonance light scattering of the system.The main factors for the RLS enhancement could be the lardger-particle-size of AuNPs.The value of RLS(I_RLS)was proportional to the concentration of Cd²⁺(c_Cd²⁺).Accordingly,a new resonant light scattering method with good selectivity,high sensitivity and high accuracy has been established.There was a good linear relationship between the I_RLSat 543 nm and the c_Cd²⁺in the range of 16¹67 nmol/L.The linear regression equation was I_RLS=191.13c_Cd2++14153(×10^-9mol/L)with the correlation coefficent r=0.9982 and the detection limits of cadmium ion was 0.9×10^-99 mol/L.Chapter 4:The FNAs_Cd2+,could prevent the aggregation between AuNPs and rhodamine 6G?Rh6G?in a system without cadmium,so,the system resonant light scattering was very weak.In the presence of Cd²⁺,Cd²⁺can bind to FNAs_Cd2+specifically,resulting in FNAs_Cd2+breaking away from the surface of AuNPs.Under the action of Cd²⁺,FNAs_Cd2+could be cut at the RNA site and form nucleic acid fragments?snippet DNA?.Then,an collective of‘?AuNPs?_n-Rh6G-snippet DNA'in big size could formed by the electrostatic interactions,the hydrogen bond and the hydrophobic interaction or the?stacking interactions,which resulting the greatly increase of the RLS of system.In the optimizing condition,a linear correlation existed between I_RLSLS and the concentration of Cd²⁺in the range of 0.25-9.96×10^-88 mol/L,the limit of detection was 0.04×10^-8mol/L,the relative standard deviation was less than 5.0%,the recoveries were the range of 96.4%-101.4%.