The electrochemical quartz crystal impedance system (EQCIS) has been used for the study of a partially immersed Au electrode in 0.2 mol/L NaClO4 aqueous solution. The influences of the immersed area and height of the ...The electrochemical quartz crystal impedance system (EQCIS) has been used for the study of a partially immersed Au electrode in 0.2 mol/L NaClO4 aqueous solution. The influences of the immersed area and height of the electrode on the EQCIS responses were evaluated, showing the highest response sensitivity to liquid loading at the center of the piezoelectric quartz crystal electrode. The increase in the immersed height of the Au electrode at oxygen reduction potentials during potential cycling was measured by this technique.展开更多
An electrochemical quartz crystal impedance system has been applied to monitorgeneration of precipitate and adsorption of the precipitate onto An electrode during electrochmicaloxidation and Fe(CN)_6,3-/Fe(CN),6 4- el...An electrochemical quartz crystal impedance system has been applied to monitorgeneration of precipitate and adsorption of the precipitate onto An electrode during electrochmicaloxidation and Fe(CN)_6,3-/Fe(CN),6 4- electrochemical catalytic oxidation of L-cysteine in phosphateaqueous buffer (pH 7.4). Significant decreases in the resonant frequency and increases in themotional resistance and the static capacitance were found during the precipitate adsorption, and thefrequency shift found in solution was ca. 2 times that in air. Similar responses of quartz crystalimpedance and a white precipitate were obtained during redox titration of L-cysteine solutionusing K_3Fe(CN)_6 solution. FT-IR analysis indicated that the white precipitate is cystine. Theelectrode collection efficiency of the electrogenerated cystine was estimated.展开更多
We report for the first time a cleavage phenomenon in the resonant peak of a piezoelectric quartz crystal(PQC) in liquid phase.In the presence of a strong longitudinal wave effect,an additional resonant peak appears i...We report for the first time a cleavage phenomenon in the resonant peak of a piezoelectric quartz crystal(PQC) in liquid phase.In the presence of a strong longitudinal wave effect,an additional resonant peak appears in the conductance-frequency curve.With gradually increasing liquid density,the additional peak moves from low to high frequency region then disappears.The frequency of the additional resonant peak is sensitive to the change in liquid density.The frequency shift of the additional peak is linear with the liquid density in a given range.For a 5 MHz PQC with a reflection distance of 16 mm for longitudinal wave,the sensitivity to liquid density is 2.61×10^6 Hz g^-1 cm^3.The overlap between the primary resonant peak and the additional resonant peak causes a decrease in the intensity of the former and an increase in the intensity of the latter.In a combined impedance analysis method,the changes in surface mass loading,density and viscosity of the liquid were monitored simultaneously by a PQC sensor.展开更多
A novel method for simultaneous impedance analyses of two resonating piezoelectric quartz crystals is proposed via the admittance measurements of two crystals in parallel and then nonlinear admittance fitting to an eq...A novel method for simultaneous impedance analyses of two resonating piezoelectric quartz crystals is proposed via the admittance measurements of two crystals in parallel and then nonlinear admittance fitting to an equivalent circuit of two Butterworth-Van Dyke circuits in parallel. Series of sucrose aqueous solutions and copper electro-deposition/stripping in a NH 3-(NH 4) 2SO 4 buffer were used to test this method, giving that the impedance parameters of each of the parallel crystals reflecting the solution density-viscosity effect or the mass effect were very close to those measured with each single crystal alone. Also, simultaneous impedance measurements at the working and counter electrodes were carried out and discussed.展开更多
The quartz crystal microbalance （QCM） was used to monitor the one-day incubation of human breast cancer cells （MCF-7） on the gold electrode. In combination with an optical microscope simulation experiment, the cel...The quartz crystal microbalance （QCM） was used to monitor the one-day incubation of human breast cancer cells （MCF-7） on the gold electrode. In combination with an optical microscope simulation experiment, the cell-population pictures at various stages, the QCM responses to the cells＇ adhesion, spreading and proliferation on the electrode surface were discussed. The △f0 and △R1 responses were found mainly from mixed effects of viscodensity and surface stress, and in proportion to the cell coverage, rather than to the number of cells at the electrode. The significant fore-and-aft changes in cyclic voltammetry and electrochemical impedance spectroscopy of the ferri-ferrocyanide redox couple also proved that the cells were adhesion to the gold surface.展开更多
基金This work was supported by the National Natural Science Foundation of China the Science and Technology Foundation of Hunan P
文摘The electrochemical quartz crystal impedance system (EQCIS) has been used for the study of a partially immersed Au electrode in 0.2 mol/L NaClO4 aqueous solution. The influences of the immersed area and height of the electrode on the EQCIS responses were evaluated, showing the highest response sensitivity to liquid loading at the center of the piezoelectric quartz crystal electrode. The increase in the immersed height of the Au electrode at oxygen reduction potentials during potential cycling was measured by this technique.
文摘An electrochemical quartz crystal impedance system has been applied to monitorgeneration of precipitate and adsorption of the precipitate onto An electrode during electrochmicaloxidation and Fe(CN)_6,3-/Fe(CN),6 4- electrochemical catalytic oxidation of L-cysteine in phosphateaqueous buffer (pH 7.4). Significant decreases in the resonant frequency and increases in themotional resistance and the static capacitance were found during the precipitate adsorption, and thefrequency shift found in solution was ca. 2 times that in air. Similar responses of quartz crystalimpedance and a white precipitate were obtained during redox titration of L-cysteine solutionusing K_3Fe(CN)_6 solution. FT-IR analysis indicated that the white precipitate is cystine. Theelectrode collection efficiency of the electrogenerated cystine was estimated.
基金supported by the National Natural Science Foundation of China(Nos.20775045,20975063)open foundation of the State Key Laboratory of Chemo/Biosensing and Chemometrics,Hunan University(No.2008012)
文摘We report for the first time a cleavage phenomenon in the resonant peak of a piezoelectric quartz crystal(PQC) in liquid phase.In the presence of a strong longitudinal wave effect,an additional resonant peak appears in the conductance-frequency curve.With gradually increasing liquid density,the additional peak moves from low to high frequency region then disappears.The frequency of the additional resonant peak is sensitive to the change in liquid density.The frequency shift of the additional peak is linear with the liquid density in a given range.For a 5 MHz PQC with a reflection distance of 16 mm for longitudinal wave,the sensitivity to liquid density is 2.61×10^6 Hz g^-1 cm^3.The overlap between the primary resonant peak and the additional resonant peak causes a decrease in the intensity of the former and an increase in the intensity of the latter.In a combined impedance analysis method,the changes in surface mass loading,density and viscosity of the liquid were monitored simultaneously by a PQC sensor.
文摘A novel method for simultaneous impedance analyses of two resonating piezoelectric quartz crystals is proposed via the admittance measurements of two crystals in parallel and then nonlinear admittance fitting to an equivalent circuit of two Butterworth-Van Dyke circuits in parallel. Series of sucrose aqueous solutions and copper electro-deposition/stripping in a NH 3-(NH 4) 2SO 4 buffer were used to test this method, giving that the impedance parameters of each of the parallel crystals reflecting the solution density-viscosity effect or the mass effect were very close to those measured with each single crystal alone. Also, simultaneous impedance measurements at the working and counter electrodes were carried out and discussed.
基金This work was supported by the National Natural Science Foundation of China(20275010,20335020)the Basic Research Special Program of the Ministry of Science and Technology of China(2003CCC00700)the Foundation of the Ministry of Education(M0E)of China(jiaorensi[2000]26,jiaojisi[2000]65).
文摘The quartz crystal microbalance （QCM） was used to monitor the one-day incubation of human breast cancer cells （MCF-7） on the gold electrode. In combination with an optical microscope simulation experiment, the cell-population pictures at various stages, the QCM responses to the cells＇ adhesion, spreading and proliferation on the electrode surface were discussed. The △f0 and △R1 responses were found mainly from mixed effects of viscodensity and surface stress, and in proportion to the cell coverage, rather than to the number of cells at the electrode. The significant fore-and-aft changes in cyclic voltammetry and electrochemical impedance spectroscopy of the ferri-ferrocyanide redox couple also proved that the cells were adhesion to the gold surface.
