Resonant Frequency Of Quartz Crystal Research Articles

Determination of Lactoferrin Using High-Frequency Piezoelectric Quartz Aptamer Biosensor Based on Molecular Bond Rupture

In this study, an aptamer biosensor for detecting lactoferrin (LF) was developed using piezoelectric quartz-induced bond rupture sensing technology. The thiol-modified aptamer I was immobilized on the gold electrode surface of the quartz crystal microbalance (QCM) through an Au-S bond to specifically bind LF. It was then combined with aptamer–magnetic beads to amplify the mass signal. The peak excitation voltage was 8 V at the resonance frequency for the 60 MHz gold-plated quartz crystal. When the molecular bond cracking process occurred, the aptamer–magnetic beads combined on the surface of the piezoelectric quartz were removed, which resulted in an increase in quartz crystal resonance frequency. Therefore, the specific detection of LF can be realized. Under optimized experimental conditions, the linear range for LF was 10–500 ng/mL, the detection limit (3σ) was 8.2 ng/mL, and the sample recoveries for actual milk powder samples ranged from 97.2% to 106.0%. Compared with conventional QCM sensing technology, the signal acquisition process of this sensing method is simple, fast, and easy to operate.

An FPGA-Accelerated Quartz Crystal Measurement System Based on a Negative Feedback Loop With Quadrature Demodulation

Rapid measurement of the resonant frequency of quartz crystal (QC) devices plays a key role in applying QC-based dynamic monitoring, such as respiration monitoring and kinetic process in electrochemical reactions. This work develops an FPGA-accelerated QC measurement system without software-based curve fitting. A negative feedback loop based on the susceptance response collected by the quadrature demodulation circuit is constructed. Moreover, a proportional-integral-differential control and tracking strategy is applied to improve the measurement speed significantly. The test results show that the implemented system can track a frequency shift of 5 kHz bandwidth within 50 ms. The standard deviation of the measured frequency of a QC device under test is only 0.17 Hz, which indicates that the proposed system is high stability and high precision. The frequency measurement results have a relative error of 0.8 ppm compared with the Agilent 4294A impedance analyzer. It is demonstrated that the proposed QC measurement system has great potential for QC-based dynamic detection.

Measurement of quartz crystal unit parameters based on the precise derivation of zero phase frequency

It is usually considered that the resonance frequency of quartz crystal resonator is only related to dynamic inductance L 1 and dynamic capacitance C 1, and load resonance frequency has connection with L 1, C 1 and static capacitance C 0. Hence, the dynamic resistance cannot be measured by frequency. The deduction show that all the frequencies relates to L 1, C 1, C 0 and dynamic resistance R 1. Then, a method for measuring the total equivalent parameters of quartz crystal resonator based on zero phase frequency is proposed in this Letter. The simulation results of advanced design system (ADS) verify the validity of this proposal in theory. After that, the phase-frequency-curves of a quartz crystal resonator with 10 and 5 MHz are measured, which can obtain equivalent parameters of through data processing. The results show that this method has calculated parameters essentially in agreement with nominal parameters. This method does not have reciprocating debugging process, and the test process is simple as well. In addition, the approximate calculation is not used in this method, and it could be widely extent to the field of sensors, such as quartz crystal microbalance sensors, temperature sensors and so on.

A method for nanoparticle characterization by laser induced detuning of quartz crystal microbalance (LID-QCM)

The effect of quartz crystal resonance frequency increase upon light irradiation is studied under various conditions, including vacuum. This effect is most probably of a thermal origin and can be attributed to inhomogeneous heating. The magnitude of this effect depends linearly on the amount of energy absorbed by the quartz crystal electrodes. It allows for additional in situ characterization of nanoparticles (NPs) formed in a flame. This type of characterization is demonstrated by the distinction between different flame-synthesized NPs deposited on the quartz crystal surface via molecular beam sampling.

Helium diffraction study of pentacene films on Au(1 1 1)

Here we present a helium atom diffraction study of pentacene films on Au(111) surface prepared by supersonic molecular beam deposition. Though investigated parameter space was limited no significant difference between the films prepared by different deposition energies was observed. Completion of monolayer coverage was confirmed by simultaneous helium scattering and quartz crystal resonance frequency shift measurements during pentacene film growth on the gold electrode of a quartz resonator. Monolayer films were found to adopt a (6×3) unit cell which was also observed for pentacene monolayers on Ag(111). However no ordered multilayer film structure could be observed which is in contrast with the previous Ag(111) studies.

DETECTION OF CADMIUM-RESISTANT RHIZOBACTERIA USING PIEZOELECTRIC NANOBIOSENSOR

Traditionally, enzyme-linked immunosorbent assay (ELISA) is used for the interaction study of antibody–antigen ( Ab – Ag ) along with Western blot, immunofluorescence and flow cytometry. These are the processes which give the result at the end on the basis of amount of bound label. Piezoelectric quartz crystal microbalance (QCM) has more advantages like elimination of the use of the enzyme or radioactive-labelled material, simple concept, rapid turn-around time, cost effectiveness and easy automation over traditional techniques. Efforts are being made to enhance the efficacy of QCM biosensor by employing appropriate nanomaterials. In the present piece of work silver nanoparticles were prepared, characterized and applied on AT-cut gold-coated quartz crystal to get more surface area and hence more Ag – Ab complex. The gold electrode of quartz crystal modified with silver nanoparticles was exposed to antibody (anti-Rhizobacteria) and finally to the corresponding antigen (Rhizobacteria). The change in the resonant frequency of quartz crystal of QCM was measured after each modification. The sharp decrease in resonant frequency reflects the interaction of Rhizobacteria with its corresponding antibody (anti-Rhizobacteria). The signals obtained from such a nanobiosensor were compared with ELISA. A similar selectivity and higher sensitivity along with less time was observed with the developed QCM nanobiosensor.

Immobilization of liposomes onto quartz crystal microbalance to detect interaction between liposomes and proteins

To study the interaction between liposomes and proteins, intact liposomes were immobilized on a metal planar support by chemical binding and/or bioaffinity using a quartz crystal microbalance (QCM). A large decrease in the resonance frequency of quartz crystal was observed when the QCM, modified by a self-assembled monolayer (SAM) of carboxythiol, was added to liposome solutions. The stable chemical immobilization of intact liposomes onto SAM was judged according to the degree with which adsorbed mass depended on the prepared size of liposomes, as well as on the activation time of SAMs when amino-coupling was introduced, where the liposome coverage of electrodes was 69 ± 8 % in optimal conditions. When avidin–biotin binding was used on amino-coupling liposome layers, liposome immobilization finally reached 168% coverage of the electrode surface. Denatured protein was also successfully detected according to the change in the frequency of the liposome-immobilized QCM. The adsorbed mass of denatured carbonic anhydrase from bovine onto immobilized liposomes showed a characteristic peak at a concentration of guanidine hydrochloride that corresponded to a molten globule-like state of the protein, although the mass adsorbed onto deactivated SAM increased monotonously.

Derivation of the shear compliance of thin films on quartz resonators from comparison of the frequency shifts on different harmonics: A perturbation analysis

Viscoelastic effects contribute to the shift in resonance frequency of quartz crystal resonators induced by deposition of thin films on the resonator surface. In turn, the mechanical stiffness of the film can be experimentally determined from a comparison of the resonance shifts on different harmonics. When the film is much thinner than the wavelength of shear sound, a series expansion of the viscoelastic effects to third order in film thickness leads to rather simple equations. When plotting the normalized frequency shift δf/f versus the square of the overtone order n2 one finds a linear relationship, where the slope is determined by the film’s elastic compliance. When the same analysis is carried out on the resonance bandwidths rather than the frequency shifts the viscous compliance is obtained. The effects of asymmetric coatings, electrodes, and liquid media are discussed.

Quartz crystal impedance and EQCM measurements applied to dithienothiophene-based polymers

Dithienothiophene polymers are promising materials for advanced electrochemical devices and the copolymerization from different dithienothiophene isomers represents a useful tool to tune the electronic and electrochemical properties of these conducting polymers. The present paper reports and discusses polymer quartz crystal (QC) impedance measurements carried out with a frequency response analyzer in the QC resonance frequency region as well as electrochemical quartz crystal microbalance (EQCM) data during the p-doping and undoping processes of poly(dithieno[3,4-b:3′,4′-d]thiophene) (pDTT1), poly(dithieno[3,4-b:2′,3′-d]thiophene) (pDTT3) and poly(dithieno[3,4-b:3′,4′-d]thiophene-co-dithieno[3,4-b:2′,3′-d]thiophene) 50/50 (p(DTT1-co-DTT3) 50/50). The QC impedance measurements were performed to determine whether the mechanical properties of these polymers change with thickness and in different states of charge, thereby to ensure a correct application of the EQCM technique to the dithienothiophene-based polymers. The EQCM measurements were carried out to investigate whether the different geometries of DTT1 and DTT3, which can lead to different enchainments in the resulting polymers, affect the mass transport phenomena during the p-doping and undoping processes of pDTT1, pDTT3 and p(DTT1-co-DTT3) 50/50.

Modeling of a short-term stability measuring system of quartz crystal resonators

A new numerical model of a short-term stability measuring system of quartz crystal resonators is presented. It is based on the phase bridge method using a pair of resonators driven by a low-noise source. The output signal, obtained with a phase detector, is proportional to the phase difference introduced by the resonators. The numerical transfer function of each bridge path is given by the model. The output spectral density of the phase fluctuations is computed from these transfer functions and the numerical approximation of the low-noise source. The model was applied to third overtone, SC-cut, 10 MHz BVA quartz crystal resonators. It enables the rejection of the source noise versus the resonant frequency of quartz crystal resonators to be quantified.

水晶マイクロバランス法を用いた走査型ずれ応力顕微鏡の開発

This paper describes a new scanning probe microscope which is able to measure the shearing stress generated by the interaction between the STM tip and the sample surface under STM controlled. The method of measurement is utilized the quartz crystal microbalance technique. The sample is deposited on the AT-cut quartz crystal resonator surface, and the shearing stress which is generated in the sample causes the resonance frequency shift of the quartz crystal resonator. By detecting this signal, we can obtain the shearing stress distribution. The gold thin films have been observed for the STM surface topography and the distribution of subsurface shearing stress simultaneously. In the experiment, the sensitivity of the shearing stress is as high as 0.12 N/m for a 0.05 Hz frequency shift of the quartz crystal resonance frequency.

Scanning shearing-stress microscope

A new scanning probe microscope based on a scanning tunneling microscope (STM) and a frequency shift of an AT cut quartz resonator has been developed. The quartz resonator coupled to a STM sample is oscillated at its resonance frequency. The shift of the resonance frequency corresponds to the strength of the shearing stress in the sample, and is caused by the shearing force interaction between the STM tip and the sample under the tip scanning. The preliminary images presented show simultaneously STM surface topographies and the changes of subsurface shearing stresses in gold thin films. The sensitivity of our microscope is 0.30 N/m for a 0.2-Hz frequency shift of the quartz crystal resonance frequency.

Resonant frequency of a piezoelectric quartz crystal in contact with solutions

The resonant frequency of a piezoelectric crystal was determined by transmission measurements. The simple principle of this resonance method is that a transmission is measured at varying frequencies with a two-port transmission line system containing parallel resistance. Previous workers formulated the resonant frequency of a quartz crystal and the equation derived indicated that the frequency is dependent on (ρη) 1 2 and F 3 2 b, where ρ, η and F b are the density and viscosity of the solution and the fundamental frequency of the quartz crystal, respectively. The resonance method was applied to solutions of varying (ρη) 1 2 , and it is concluded that the equation holds for a wide range of different solutions. The resonance method is advantageous in solutions over the widely used conventional oscillation method because the range of (ρη) 1 2 for possible measurements is much wider.

Résonateur à quartz pour environnement sévère

The effect of axial and radial accelerations on frequency of quartz crystal-resonator as a function of various holders are studied. The results lead to describe a particular structure showing a reduction of mechanical strains due to acceleration and external pressure variations. A prototype is manufactured. First results show a reduction of sensitivity coefficients in comparison to traditional resonators: a factor of ten for acceleration and a factor of ten to twenty for external pressure variations Influence d'accelerations axiale et radiale sur la frequence de resonance d'un cristal de quartz. On decrit une situation limitant l'influence de l'acceleration et des variations de la pression exterieure

Condensation Coefficients of Argon, Krypton, Xenon, and Carbon Dioxide Measured with a Quartz Crystal Microbalance

Condensation coefficients were measured by impinging a known flux of gas from a molecular beam onto the surface of a quartz crystal microbalance. The rate of change of the quartz crystal's resonance frequency was used to calculate the condensation rate. The condensation coefficient, which is the ratio of the condensation rate to the impingement rate, was found to be ≥0.95 for Ar, Kr, Xe, and CO2 when surface temperatures are less than 26, 37, 47, and 55 K, respectively, and the gas temperatures are ≤300 K for Ar, Kr, and Xe and ≤200 K for CO2. The condensation coefficients of Ar on Kr and Xe films, Kr on Ar, and Xe on Kr were also determined as a function of surface coverage from about 0.01 to 10 atomic layers.