Based On The Research And Applications Of The Plate Capacitor Model Of The Capacitive Sensor And The New Type Of Piezoelectric Sensor

Because of real-time monitoring, simple equipment, easy operation, and low cost, sensor has gained considerable interest in analytical science. Based on the principle of plate-capacitor capacitance, which depends on the thickness and dielectric behavior of its dielectric layer, applications of capacitive sensors have been reported in recent years. This scheme provides the sensor's expectation of analysis without additional reagents or labels. The research of normal piezoelectric quartz crystal (PQC) was carried out in earlier 1980's and has been widely applied in the fields of clinic immunology, hemorheology, biochemistry, and molecular biology. The new-style PQCs, such as PCSE and SPQC, expended the PQC application fields.Capacitive sensing method is a new technique, therefore only a few contributions have been made in this field. It is necessary to develop capacitance response theory, fabricating method, and application fields. In this thesis, novel capacitive sensors have been developed. A series of results were obtained. Also in this thesis, a new-style PQC, ringed-electrode piezoelectric sensor, has been designed. The main work of this thesis is summarized as follows.1. A capacitive sensing device has been designed by using electropolymerised o-phenylenediamine (PPD) film as isolating layer and has been successfully applied to study the adsorption of Tween-80 onto PPD film surface. The equilibrium constant of adsorption of Tween-80 onto PPD film was firstly reported.2. A capacitive response model for describing two stages series reaction model was derived. The capacitive sensing method was firstly applied to study the combination of DNA with small molecular compound. The results of quartz crystal impedance (QCI) and capacitive sensing method indicate that the combination of DNA with chloroquine can be described as two stages series reaction model. The rate constants of chloroquine phosphate with dsDNA and ssDNA were estimated by fitting the real-time experimental data of capacitive sensor.3. A novel capacitive sensor based on human serum albumin (HSA)-chelant?incomplex film as dielectric layer has been fabricated. The sensors with HSA-chelant complex films as sensing element provide affinity to heavy metal ions. The HSA-disodium ethylenediamine tetraacetate (EDTA) capacitive sensor exhibits considerable sensitivity for heavy metal ions, whereas the HSA-nitronaphthalenediazoaminobenzene -4'-azobenzene (Cadion 2p) capacitive sensor possesses selectivity for cadmium ion and has been successfully applied to the determination of trace cadmium.4. For the first time, ion-selective capacitive sensors has been constructed and applied to the determination of cinchonine and pentoxyverine. Ion-pair complex was embedded in electropolymerized o-phenylenediamine film as specific sensing element. The adsorption model of cinchonine onto its selective film has been studied and equilibrium constant was determined. The sensors exhibited good sensitivity, selectivity and long-time stability.5. A novel ring-electrode piezoelectric sensor (REPS) has been designed. Its resonance behavior in liquid phase has been studied. The results indicate that the REPS can be used to investigate solution's physico-chemical property and mass loading on the quartz surface under different conditions. This kind of sensor has been successfully applied to the study of the critical micellar concentration (CMC) of CTMAB, the adsorption process of CTMAB and BSA onto quartz surface.6. The combination of protein with heavy metal ions was monitored in-situ performed with quartz crystal impedance (QCI) technique. The study was based on the adsorption of BSA-Hg(II) complex onto electrode surface. The changes of equivalent circuit parameters were found to be directly related to the process of adherence of BSA-Hg(II) complex. The influences of pH and concentration of the electrolyte solution were also studied.