Different experimental results for the influence of immersion angle on the resonant frequency of a quartz crystal microbalance in a liquid phase: with a comment

This paper presents different experimental results of the influence of an immersion angle (θ, the angle between the surface of a quartz crystal resonator and the horizon) on the resonant frequency of a quartz crystal microbalance (QCM) sensor exposed one side of its sensing surfaces to liquid. The experimental results show that the immersion angle is an added factor that may influence the frequency of the QCM sensor. This type of influence is caused by variation of the reflection conditions of the longitudinal wave between the QCM sensor and the walls of the detection cell. The frequency shifts, measured by varying θ, are related to the QCM sensor used. When a QCM sensor with a weak longitudinal wave is used, its resonant frequency is nearly independent of θ. But, if a QCM sensor with a strong longitudinal wave is employed, the immersion angle is a potential error source for the measurements performed on the QCM sensor. When the reflection conditions of the longitudinal wave are reduced, the influence of θ on the resonant frequency of the QCM sensor is negligible. The slope of the plot of frequency shifts (ΔF) versus (ρη)^1/2, the square root of the product of solution density (ρ) and viscosity (η), may be influenced by θ in a single experiment for the QCM sensor with a strong longitudinal wave in low viscous liquids, which can however, be effectively weakened by using the averaged values of reduplicated experiments. In solutions with a large (ρη)^1/2 region (0-55 wt% sucrose solution as an example, with ρ value from 1.00 to 1.26 g cm⁻³ and η value from 0.01 to 0.22 g cm⁻¹ s⁻¹, respectively), the slope of the plot of ΔF versus (ρη)^1/2 is independent of θ even for the QCM sensor with a strong longitudinal wave in a single experiment. The influence of θ on the resonant frequency of the QCM sensor should be taken into consideration in its applications in liquid phase.     

Dependence on the electric power of the immersion-angle dependence of the resonant-frequency shift of a quartz crystal microbalance in a liquid

We have investigated the immersion-angle dependence of the series resonant-frequency shift, ΔF, of the quartz crystal microbalance, QCM, in a Newtonian liquid from the point of view of the supplied electric power level. In the low electric power levels, the immersion-angle dependence and the transition phenomenon of the ΔF are observed. However, when the higher electric power levels are supplied to the QCM, the region of the transition phenomenon of the ΔF decreases rapidly with an increase in the electric power level and disappears above 1.5 dBm. That is, above 1.5 dBm, the ΔF values have only the values of 90° immersion angle in all immersion angles. We suggest that the electric power is very important factor for the ΔF in a liquid.     

Frequency response to liquid density of a piezoelectric quartz crystal sensor with longitudinal wave

Elimination of longitudinal wave effect is an important aspect in the detection cell design, although such consideration is ignored in most of references. Three detection cells were designed to investigate the influence of longitudinal wave effect on the frequency response of a piezoelectric quartz crystal (PQC) to liquid density. In the cell with horizontally mounted quartz crystal, the air/liquid interface acts the reflection surface for the longitudinal wave. The variation in liquid height by regent addition or solvent evaporation can result in fluctuation in the oscillating frequency of the PQC. The influence of the longitudinal wave is more obvious in a test liquid of lower density. In the cell with perpendicularly mounted quartz crystal, the longitudinal wave is mainly reflected back by the inner wall body. The fine structure of plotting of frequency shift (Δf) versus (ρη)^1/2 shows a wave shape, which is different from the well-known linear relationship between of Δf and (ρη)^1/2, where ρ and η are the density and viscosity of the liquid, respectively. And wave-shaped frequency-temperature curves were observed. The longitudinal wave was a kind of potential error source in the PQC measurements. The longitudinal wave effect can be efficiently eliminated by using a rough reflection surface. After eliminating the influence of reflected longitudinal wave, the stability of the sensor PQC was much improved.     

A quartz crystal microbalance study on a metallic nickel electrode

Electrochemical processes taking place on a Ni electrode have been investigated with the electrochemical quartz crystal microbalance. At potentials negative of ca. –500 mV vs. SCE, a closed frequency loop is observed without irreversible changes in the mass of the electrode. The phase transition - -Ni(OH)₂, taking place at potentials positive to –500 mV vs. SCE, is accompanied by an irreversible increase in the mass of the electrode. When Ni(OH)₂ is further oxidized, the frequency increase is followed by a decrease, indicating the transport of various species in both directions, i.e. from and into the electrode. During the Ni(OH)₂ oxidation reaction the transport of species responsible for the mass increase is slower than the charge transfer process.Contribution to the 3rd Baltic Conference on Electrochemistry, GDASK-SOBIESZEWO, 23–26 April 2003. Dedicated to the memory of Harry B. Mark, Jr. (February 28, 1934–March 3rd, 2003)     

New cut angle quartz crystal microbalance with low frequency-temperature coefficients in an aqueous phase

In a traditional quartz crystal microbalance (QCM), an AT-cut (cut angle φ = 35.25° in yxl orientation) quartz wafer is employed because it has low frequency–temperature coefficients (dF/dT) at room temperature region. But when a QCM is in contact with a liquid phase, its frequency is also related to the properties of the liquid, which are temperature dependent. The value of dF/dT is about 20 Hz/°C for a 9 MHz AT-cut QCM with one side facing water. In this work, a group of QCMs in new cut angles were prepared. The influence of the cut angle on the frequency–temperature characteristic, response sensitivities to surface mass loading and viscodensity of liquid were investigated. An intrinsically temperature-compensated QCM sensor that possesses low dF/dT values in aqueous solution was reported. When a 9 MHz QCM with φ = 35.65° was contacted with water with one side, its dF/dT value is close to zero at ca. 25 °C and its averaged value of |dF/dT| is only 0.6 Hz/°C in the temperature range of 23–27 °C. The frequency responses to surface mass loading and viscodensity of liquid phase are very close among the QCMs with the cut angles in the range of 35.15–35.7°. The intrinsically temperature-compensated QCM was applied to investigate the alternate adsorption processes of cationic polyelectrolyte and silica nanoparticle.     

Transition phenomenon of immersion-angle dependence of quartz crystal microbalance in Newtonian liquid

The present work reports the new effects of the immersion-angle dependence of the resonant-frequency shift (ΔF) of the one-face sealed quartz crystal microbalance (QCM) in a Newtonian liquid. The immersion-angle dependence of ΔF appears below the sucrose concentration of 12 wt.%. However, we found that the transition phenomenon of ΔF occurs between 12 and 20 wt.% and then the immersion-angle dependence of ΔF disappears above 20 wt.% (finally, the ΔF values above 20 wt.% are equal to those of 90° in all immersion angles). In order to obtain further insights into the transition phenomenon and the disappearance of the immersion-angle dependence of ΔF, we investigated the immersion-angle dependence of the electrolytic solution, i.e., NaCl solution. This investigation indicated that this monovalent electrolytic solution causes the immersion-angle dependence but not the transition phenomenon and the disappearance of the immersion-angle dependence of ΔF. On the basis of these results, we suggest that the non-charge of the molecule is the important element to generate the transition phenomenon and the disappearance of the immersion-angle dependence of ΔF.     

The quantification of sodium in mineral waters using a quartz crystal microbalance

A sensor for sodium based on a piezoelectric quartz crystal is proposed. The quartz crystal was coated with 5% of bis[(12-crown-4)methyl] dodecylmethylmalonate, 33% of PVC and 62% of NPOE to which KTpClPB in a 22% molar proportion to the ionophore was added. Coating amounts producing a frequency decrease around 18 kHz show optimum linear calibration ranges for the analysis of sodium in commercial mineral waters. Besides sensitivity, coating stability and selectivity of the sensor over other cations were adequate for those analyses. The results obtained analysing commercial mineral waters by the proposed method are not significantly different (α=0.05) from the ones obtained by atomic spectrometry.     

Improve the signal-to-noise ratio of a quartz crystal microbalance in an impedance analysis method

A new data treatment method for the improvement of the signal-to-noise ratio of a quartz crystal microbalance (QCM) was proposed, where an averaged resonant frequency was calculated according to its conductance peak in an impedance analysis method. The relationship between the averaged resonant frequency and the medians of the conductance peak at different sampling heights was derived. It was shown that the signal-to-noise ratio of the averaged resonant frequency was about eight times of that of the resonant frequency calculated directly from its equivalent circuit parameters. The averaged resonant frequency of the QCM was applied to monitor the self-assembled process of a 6-O-(2′-(α-thiohydroxyacetamide)-ethyl)-diethoxylsilyl-β-cyclodextrin (OTED-β-CD), on gold surface as well as the adsorption of nitrophenol isomers onto the OTED-β-CD self-assembled monolayer film.     

Properties of the overtone mode of the quartz crystal microbalance in a low-viscosity liquid

The effect of the immersion angle on the overtone mode of the quartz crystal ‘microbalance’ (QCM, piezoelectric quartz crystal) was investigated in a Newtonian liquid. The measurement using the impedance analyzer revealed that the resonant frequency shift of the Nth overtone mode of the QCM was depend on the immersion angle, and, at each immersion angle, was times larger than that of the fundamental mode. These tendencies were also observed in the resistance of the Butterworth-Van Dyke equivalent circuit. Furthermore, on the basis of these results, we have discussed the immersion angle dependence of the resonant frequency shift and the resistance.     

A new electrochemical cell adapted to quartz crystal microbalance measurements

As the resonance frequency of an oscillating quartz changes upon the deposition of a given mass to the crystal surface, it can be used as a very sensitive mass measuring device. Despite a growing interest in the use of electrochemical quartz crystal microbalance (EQCM), there is still no commercial available measurement cell which can satisfy all the conditions needed in electrochemical investigations. The design and characteristics of a new electrochemical cell adapted to EQCM measurements are presented. The sensitivity of the microbalance, which is determined by several calibration runs of silver electrodeposition is (183.2±2.9) Hz μg⁻¹ cm². This value, which is close to the theoretical one, confirms the validity of the system we have developed. The calibration procedure and the EQCM using range are then discussed.     

A study of glycoprotein-lectin interactions using quartz crystal microbalance

A study of biospecific interactions between lectins and glycoproteins using a quartz crystal microbalance biosensor with dissipation monitoring (QCM-D) was reported. Four lectins were covalently immobilised on the thiol-modified gold electrode of the QCM chips in order to obtain sensing surfaces. The frequency shift served as analytical signal and the dissipation shift provided additional information about the viscoelastic properties of the glycoprotein-lectin complex formed on the surface of the QCM chip. The working conditions of the assay were optimised. The interaction between different lectins and glycoproteins was characterised by specific frequency shifts and each glycoprotein displayed its own unique lectin-binding pattern. This lectin pattern can serve as a finger print for the discrimination between various glycoproteins. The biosensor enabled quantitative determination of glycoproteins in the concentration range of 50 μg mL⁻¹ to 1 mg mL⁻¹ with good linearity and R.S.D. of less than 6.0%. An additional advantage of the proposed biosensor was the possibility to re-use the same lectin surfaces during a long period of time (2 month) without changes in analytical response. This was experimentally achieved by the application of a proper regeneration solution (10 mM glycine-HCl, pH 2.5). The lectin-based quartz crystal microbalance technique is suitable both for rapid screening and for quantitative assay of serum glycoproteins.     

Immunosensor for okadaic acid using quartz crystal microbalance

An immunosensor for the determination of okadaic acid (OA) using a quartz crystal microbalance (QCM) was developed and optimised in standard solutions. Several coupling techniques, protein A, protein G and polyethylenimine (PEI) with glutaraldehyde (GA) cross-linking, were investigated for the determination of okadaic acid and a very good result was obtained with PEI coupling. With the PEI coupling method, the optimisation of incubation time for the activation of PEI on the crystal surface using GA, the effect of the dilution factor of OA-bovine serum albumin (BSA) conjugate and the amount of antibody on crystal frequency were studied. Different molar ratios (4:1, 14:1, 30:1) of OA to bovine serum albumin for the conjugation were examined and the results using ELISA and a QCM showed that a ratio of 14:1 was slightly better than the other two. The strong attachment of the cross-linked complex to the gold surface resulted in an excellent storage lifetime of 38 days. However, the detection limit (1.9 μg/ml) and the sensitivity of the sensor were not satisfactory. Significant improvement of the performance of the device was obtained by incorporating an antibody-BSA hydrogel. Initial results showed that the minimum amount of analyte detectable and the sensitivity of the device were improved by 524- and 80-fold, respectively.     

A quartz crystal microbalance sensor for the determination of nitroaromatics in landfill gas

A new sensor based on oxidative combustion of nitroaromatics to NO₂ and its detection with a quartz crystal microbalance (QCM) coated with copper phthalocyanine (CuPc) was developed for determination of nitroaromatics in landfill gas. An alternative method based on gas chromatography–mass spectrometry (GC–MS) was also used in order to assess the performance of the proposed method. The results show that the analytical apparatus based on the QCM is less expensive than the GC–MS, and that the analytical error is 0.8% for both methods.     

Application of the quartz crystal microbalance for the investigation of nanotribological processes

The electrochemical preparation of copper layers was investigated using a quartz crystal microbalance (QCM) with damping monitoring. The damping increase during the deposition could be separated into two contributions arising from an internal and an external friction process. External friction comes from the coupling of the shear motion of the rough metal surface to the viscous liquid. Internal friction occurred only in the coarse grained layers and can be explained by phonon excitations at the grain boundaries.Presented at the 3rd International Symposium on Electrochemical Processing of Tailored Materials held at the 53rd Annual Meeting of the International Society of Electrochemistry, 15–20 September 2002, Düsseldorf, Germany     

Application of a flow type quartz crystal microbalance immunosensor for real time determination of cattle bovine ephemeral fever virus in liquid

Bovine ephemeral fever (BEF) is a viral disease of cattle. A flow type quartz crystal microbalance (QCM) immunosensor was developed for the real time determination BEF virus (BEFV) that is suitable for clinical point-case diagnosis. Self-assembled monolayer (SAM) of thiols and sulphides by the cystamine–glutaraldehyde method was used for the immobilization of BEFV monoclonal antibody on the gold surface of a quartz crystal microbalance (QCM). A positive correlation was found between the virus concentration and frequency changes (R² = 0.9962) on this QCM system. The reproducible rates for the 50 and 10 μg/mL samples were 4 and 13.9%, respectively. There was no interference from non-specifically adsorbed phage. Using this flow type QCM immunosensor, BEFV could specifically be detected with sensitivity comparable to a conventional enzyme-linked immunosorbent assay (ELISA). The measurement could be obtained directly, within several minutes, rather than hours as required visualizing the results of ELISA. In addition, the observation of reproducible and constant changes after successive additions of BEFV suggests that a QCM immunosensor in a flow cell could be developed for automated or continuous real time operation.     

Study of electrochemical palladium behavior by the quartz crystal microbalance. I. Acidic Solutions

Sorption of hydrogen in a palladium electrode with a limited volume has been studied using the quartz crystal microbalance (QCM). During the hydrogen sorption process in the palladium electrode, strains are generated inside the metal which result in changes in the frequency of the crystal. These stresses change in a non-linear manner during electrode saturation, with α- and β-phases. This effect creates significant problems with the objective estimation of the amount of sorbed hydrogen inside the palladium electrode using the QCM method. This method is more accurate for the study of electrode surface processes, i.e. specific anion adsorption on the electrode surface or electrode dissolution. Received: 6 August 1998 / Accepted: 1 December 1998     

Characteristics of the series resonant-frequency shift of a quartz crystal microbalance in electrolyte solutions

We report the novel characteristics of the series resonant-frequency shift, DeltaF, of a one-face sealed quartz crystal microbalance (QCM) in solutions of monovalent electrolytes and divalent electrolytes. In the present study, we used NaCl, KCl, LiCl, NaNO3 and CH3COONa as monovalent electrolytes, and MgCl2, CaCl2, MgSO4 and Na2SO4 as divalent electrolytes. These experiments reveal that, in all the solutions, the DeltaF values vary linearly with an increase in the square root of the density-viscosity product of the solutions, and the immersion angle dependence of DeltaF appears. Moreover, we have found that the intercept values of DeltaF are dependent only on the cation species, and that the slope values of DeltaF with the viscosity and density of the solutions are related only to the valence of ions. We also suggest that the DeltaF values are independent of anion species, conductivity and permittivity of the solutions.     

基于分子印迹技术的丙溴磷压电石英晶体微天平研制

介绍了一种用于检测丙溴磷农药的分子印迹压电生物传感器的构建方法。采用沉淀聚合法合成了农药丙溴磷的分子印迹聚合物,将其固定于石英晶体微天平电极表面构建传感器;采用环境扫描电镜以及原子力显微镜对聚合物形貌、传感器电极表面形貌特征进行分析,并利用传感器对丙溴磷农药进行检测分析,其质量浓度在10~1000 ng/mL范围内,传感器频率改变与丙溴磷浓度之间的响应呈线性关系,线性方程为y=0.139ρ+2.26(r=0.9984)。结果表明,构建的分子印迹压电生物传感器能够对农药进行初步检测,具有较高的灵敏性和较好的特异识别能力。     

Biofouling of dextran-derivative layers investigated by quartz crystal microbalance

This study reports the fouling of carboxymethyl dextran (CMD) layers in cell culture medium, fibronectin, and serum solutions. CMD layers were covalently immobilized onto amine groups available either on an n-heptylamine plasma polymer (HApp) layer or onto a polyethylenimine (PEI) coating grafted to an acetaldehyde plasma polymer (AApp) layer. The successful immobilization of the graft layers was demonstrated by X-ray photoelectron spectroscopy (XPS). Primary amines on HApp and AApp + PEI surfaces were quantified using a colorimetric assay. Quartz crystal microbalance (QCM) was used to investigate in real-time the fouling of the graft layers upon incubation in cell culture medium (RPMI), fibronectin, and foetal bovine serum (FBS) solutions. HApp, AApp and AApp + PEI layers exhibited large fouling in fibronectin and FBS solutions, while fouling in RPMI cell culture medium was not significant. Protein repellent properties of CMD layers in FBS and fibronectin have been demonstrated compared to the other tested surfaces. QCM has shown that both CMD layers were fouled to a small extent in RPMI medium.     

Principles of quartz crystal microbalance/heat conduction calorimetry: Measurement of the sorption enthalpy of hydrogen in palladium

A sensitive new measurement technology is described which combines calorimetry, gravimetry, and rheology applied to chemical reactions in thin films: quartz crystal microbalance/heat conduction calorimetry (QCM/HCC). The quartz crystal microbalance/heat conduction calorimeters constructed so far simultaneously measure heat generation, mass uptake or release, and viscoelastic property changes in the same, sub-milligram solid film sample when gases interact with the film in an isothermal surrounding. It is possible to measure the energetics of formation of a single layer of adsorbed molecules on a gold surface with this technique. The principles of operation of both the mass and the heat flow sensor are described, and one implementation of the combined sensor and apparatus and its electronics is presented. Methods for calibration and the preparation of thin sample films are summarized. As an illustrative example, the determination of the sorption enthalpy of hydrogen in a 25 °C palladium film of 140 nm thickness is discussed in detail. Other examples of the operation of the QCM/HCC are tabulated.