Application Research Of Piezoelectric Sensor Technology In Self-Assembly Of Alkanethiol And Gold Nanoparticles

This paper studied the self-assembly kinetics on Au electrode of QCM .The former work focused on testing and calibrating QCM oscillating circuit so that it can be used in liquid solvents, such as ethanol, methanol, benzene,heptane, etc.The work ranges from preparation of gold nanoparticles, Uv-vis characterization,to TEM characterization, which indicate that Au colloids disperse in uniform,the size of Au nanoparticles averages 20[nm] and has the spherical shape.The SEM images of Au surface on QCM have proved that it has a relative rough surface,and some defect on it. The Au surface 's roughness has drastically decreased and the defect has disappeared after self-assembly,which indicate that the properties of surface,such as wetness, stability and bioactivity can be greatly changed through self-assembly.The research of self-assembly mainly includes the following two aspects: self-assembly of alkanethiol on Au sueface of QCM and nanogold's self-assembly on the layer of 1,6-hexanedithiol on Au surface of QCM.The in situ techniques about the adsorption kinetics on Au surface has been demonstrated to have the capability of probing organic films at the solid/liquid interface,including, STM/AFM,second harmonic generation, ellipsometry, Ranman spectroscopy and QCM measurements.Regarding the adsorption kinetics of alkanethiols,we found the self-assembly kinetics included two stages in the adsorption kinetics:initially fast but disordered adsorption step followed by a slow packing step.The film formation kinetics depends on the following three factors:solvent,concentration of alkanethiol and alkane chain length.In different solvents,the higher the diaelectric constant is,the faster the alkanethiol adsorbs,which leads to more alkanethiol's adsorption on QCM ,consequently the more frequency changes are observed In the same solvent,the similar results described above can be found in the solution with higher concentration of the alkanethiol.We study adsorption kinetics of 1,6-hexanedithiol on Au surface using QCM.The adsorption kinetics during the initia stage can be described as a first-order Langmuir model.We studed the adsorption behavior of 1,6-hexanedithiol in several solvents,such as ethanol/water(v/v=2/1), methanol/water(v/v=2/1), ethanol, methanol, benzene, heptane with QCM in real time,the frequency datas were fitted with first-order Langmuir model,we discovered good linear relationship.Now we can work out association constant ka anddissociation constant kd according to the fitting slope,which represents the rate constant.Then we may figure out equilibrium constant and standard Gibbs free energy,△G0.Analyzing the rate constants at different temperature, we can gain the activation energy Ea。The adsorption kinetics of gold nanoparticles on the layer of 1,6-hexanedithiol may be described as "diffusion—collision—connection"model,the frequency shift(△f) of quartz crystal on QCM is linearly with square root of time(t)...