The Development Of Multifunction Ultrasensitive QCM And The Research Of Physisorption Of Macromolecular On Au Surface

Quartz Crystal Microbalance QCM is a kind of ultrasensitive sensor. QCM could measure the mass as small as a few nanogrames, and the mechanical parameter such as shear molecules and viscosity on nano-scales. Rescently, it was found that not only the resonance frequency of crystal related to the property of the mass adsorbed on the surface of crystal, but also the resistance and the dissipation factor of the crystal have definitely physical meaning. Nowadays QCM is widely used in the research of biosensors, the interaction on nano-scales and other fields. So the development of a multifunction QCM is significant. Because QCM is very sensitive and could be used in liquid qhase, it is suitable for the research of physisorption of macromolecular. Physisorption of macromolecules at interface is ubiquitous in physical, chemical and biological process and plays an important role in the polymeric syntheses and biomedical applications. So the research of physisorption of macrobalance is significant in academe and application. This thesis is mainly about the development of QCM and the research of physisorption of macromolecular. The main results are as follows:1 Derived the physical model of QCM under liquid phase, and give out the function ofΔf andΔD) under different condications.2 Give out the two methods to measure the D factor of crystal. And found out the way to eliminate the parallel capacitance from the conductance versus frequency curve, effectively improved the precision of the measurement. And we have not found the same way from other reference.3 Developed a novel quartz crystal oscillator. The oscillator works on the 3 overtone of the crystal, can drive the crystal under liquid phase, and can measure the series resonant frequency the resistance and dissipation of the crystal. In the design of the oscillator we eliminate the affect of the parallel capacitance by the capacitance compensation technology, so it can work in the high viscosity liquid. We use a band pass filter in the oscillator, so it can work on the 3 overtone of the crystal, and with same method it can also work on 5 overtone.4 Developed a liquid cell for our QCM. With the liquid cell we can chang the sample continusly in an experiment, and the use of each sample could as little as 5ml. We also developed a high precision temperature control system for the liquid cell, and the stability of temperature is±0.0015℃. We give out a new design for the liquid cell, which overcome the limitation of the current one, and it will be used in the future.5 Useing PNIPAM as model studied the physisorption macromolecular on Au surface in solution with QCM-D. We found that in 20℃the PNIPAM could form a monolayer on the Au surface, and the completion of the monolayer is via a densification process, and we can use Langmuir equation describe this process. When the temperature goes above 32℃the PNIPAM could form multilayer on the same substrate. All these different adsorption characteristics can be qualitatively explained in terms of the difference of the polymer in its swollen coil state and in its collapsed globule state and by the difference in the adsorbate-substrate and adsorbate-solvent molecule interactions for the polymer in two states.