Gold Nanoparticles Amplified QCM Detection Of Heavy Metal Ions

Undecomposebel, accumulateing in the organisms for a long time and having a high toxicity in a trace content, heavy metal is a harmful pollutant. Once it accumulate in human body through the food chain, it cause various diseases,even affect the next generation. Therefor, heavy metal detection is very important for medicine, food and environment. Traditional trance heavy metal detection methods which is based on expensive instrument, wasting of money and time , unsensitive or undetectable for some metal ions ,and need for specialist operator are not competent for these days. Thus new methods with simple instrument , speediness and high sensitivity is need for qualitatively and quantitatively detect heavy metals in samples.Herein, A new and novel detection method for heavy metal ions has been developed using quartz crystal microbalance(QCM) as a sensor and gold nanoparticles (GNPs) as a signal amplifier. Resonant frequency shift of QCM caused by the selfassembleing of heavy metal ions and nanoparticles on the electrode was detected for heavy metal determination.Metal ions were captured onto the binding reagent modified QCM surface, the same material modified gold nanoparticles are then introduced to bind the surface-captured metal ions. The metal ions, binding reagent modified gold substrate and GNPs formed sandwich nanostructures by binding effect between metal ions and binding reagent, and cause a remarkable QCM resonant frequency decrescence as a detection signal. The present thesis is composed of the following three parts:â‘ Gold nanoparticles were synthesized by reduction of HAuCl4 with trisodium citrate. TEM simage show that synthesized gold nanoparticles are spherical dispersive and equirotal with an average diameter of 10±0.8nm .The ultraviolet-visible spectrum of gold nanoparticles show a sharp and narrow absorption peak appears at 517.5nm.The stability of uncapped GNPs,MBA capped GNPs and oligonucleotide capped GNPs are detected in solutions with various pH values and salinitys. Acid distribution coefficient equation(ADCE) and electrical double layer theory(EDLT) were used to deduce the influence of pH and salinitys on the stability of gold nanoparticle. The study of gold nanoparticles'stability is useful for the following experiment.â‘¡QCM electrode and GNPs were modified with MBA to form a GNPs enhanced QCM system for heavy metal ions detection. Metal ions and MBA capped GNPs were selfassembled on the QCM electrode by complexation of metal ions with carboxyl groups of MBA, and cause a remarkable QCM resonant frequency decrescence. Using this system cadmium(II),copper(II), lead(II), cobalt (II) and mercury(II) ions in solution were determined.The effect of pH value and interference of other ions is also studied. This QCM system is more excellent than other QCM system in sensitivity and detection low limit,specially for the detection of Cd²⁺,Cu²⁺and Pb²⁺.â‘¢QCM electrode and GNPs were modified with oligonucleotide(SH-T5) riched in thymine to form a GNPs enhanced QCM system for the selective detection of mercury(II) ions .The Hg²⁺ ions and SH-T5 capped GNPs were selfassembled on the QCM electrode by the specific binding effect between Hg²⁺ ions and thymines ,and cause a remarkable QCM resonant frequency decrescence. Hg²⁺ ions at various concentrations in the solution were detected .The detection specifity for Hg²⁺ ions was also studied.With a high sensitivity and reproducibility this method can specificly detect Hg²⁺ ions in the solution interfered by other metal ions.