共查询到20条相似文献,搜索用时 15 毫秒
1.
We investigated the effects of the longitudinal wave on the immersion angle dependence of the resonant-frequency shift, ΔF, of the quartz crystal microbalance, QCM. In order to study exactly the effects, we employed the three types of cells: normal cell, cell with the glass beads and cell with sponge. The longitudinal wave exists in the normal cell. On the other hand, both the cell with the glass beads and the cell with sponge eliminate the longitudinal wave. As results, we have found that the tendencies of ΔF are the same in the three types of cells. That is, we conclude that the longitudinal wave does not have effects on the immersion angle dependence of ΔF. 相似文献
2.
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. 相似文献
3.
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) 相似文献
4.
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. 相似文献
5.
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. 相似文献
6.
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. 相似文献
7.
Alice X.J Tang Miloslav PravdaGeorge G Guilbault Sergey PiletskyAnthony P.F Turner 《Analytica chimica acta》2002,471(1):33-40
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. 相似文献
8.
The deposition and dissolution processes of copper ad-atoms on a gold or a platinum electrode in sulfuric acid electrolyte solution were investigated by using the electrochemical quartz crystal microbalance. It was found that the weight loss in the removal of the Cu-adlayer from the Au substrate was considerably larger than that expected from Faraday's law whereas the deviation for the Pt substrate was very small. The adsorption of bisulfate or sulfate anions both on Cu ad-atoms and on the electrode substrates was discussed quantitatively. It was demonstrated that higher coverage with Cu ad-atoms and lower adsorbability with bisulfate or sulfate anions were obtained on the Pt electrode than on the Au, and these effects could be ascribed to the difference in electronegativity between Pt and Au substrates. 相似文献
9.
Vivian E. Cornelio Mariele M. Pedroso André S. Afonso João B. Fernandes M.Fátima G.F. da Silva Ronaldo C. Faria Paulo C. Vieira 《Analytica chimica acta》2015
The hemoglobin (Hb) released from erythrocytes is a primary nutritive component for many blood-feeding parasites. The aspartic protease cathepsin D is a hemoglobinase that is involved in the Hb degradation process and is considered an interesting target for chemotherapy intervention. However, traditional enzymatic assays for studying Hb degradation utilize spectrophotometric techniques, which do not allow real-time monitoring and can present serious interference problems. Herein, we describe a biosensor using simple approach for the real-time monitoring of Hb hydrolysis as well as an efficient screening method for natural products as enzymatic inhibitors using a quartz crystal microbalance (QCM) technique. Hemoglobin was anchored on the quartz crystal surface using mixed self-assembled monolayers. The addition of the enzyme caused a mass change (frequency shift) due to Hb hydrolysis, which was monitored in real time. From the frequency change patterns of the Hb-functionalized QCM, we evaluated the enzymatic reaction by determining the kinetic parameters of product formation (kcat). The QCM enzymatic assay using immobilized human Hb was shown to be an excellent approach for screening possible inhibitors in complex mixtures, opening up a new avenue for the discovery of novel inhibitors. 相似文献
10.
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. 相似文献
11.
Five probes including four that contained isoprenoid chain were synthesized. These probes were assembled onto the gold-coated quartz crystal chips for analysis of their interactions with four yeast proteins by using the quartz crystal microbalance technology. Results showed that 3-phosphoglycerate phosphokinase and triosephosphate isomerase had clear interactions with certain probes, while glutathione reductase and phosphoglucose isomerase gave much lower interaction signals. It also suggested that 3-phosphoglycerate phosphokinase had two sites interacting with the probe attached with a geranyl moiety. Further molecule simulation experiments provided supportive information on these intermolecular interactions. Together, our data suggested that there are hydrophobic interactions, with relatively good selectivity, between isoprenoid chain and proteins. 相似文献
12.
This report compares the performance of polymer and carbon nanotube-polymer composite membranes on a quartz crystal microbalance (QCM) sensor for the detection of aromatic hydrocarbons (benzene, toluene, ethylbenzene, p-xylene and naphthalene) in aqueous solutions. Several different polymers (polystyrene, polystyrene-co-butadiene, polyisobutylene and polybutadiene) and types of functionalized carbon nanotubes (multi-walled and single-walled carbon nanotubes) were investigated at varying carbon nanotube (CNT) loading levels and film thicknesses. In a majority of instances, the difference in response between membranes comprising pure polymer and membranes containing 10% (w/w) carbon nanotubes were not statistically significant. However, a notable exception is the decreasing sensitivity towards p-xylene with increasing carbon nanotube content in a polybutadiene film. This variation in sensitivity can be attributed to a change in the sorption mechanism from absorption into the polymer phase to adsorption onto the carbon nanotube sidewalls. With much thicker coatings of 10% (w/w) carbon nanotube in polybutadiene, the sensitivity towards toluene was higher compared to the pure polymer. The increased toluene sensitivity may be partially attributed to an increase in the sorption capacity of a carbon nanotube polymer composite film relative to its corresponding pure polymer film. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) measurements were performed to understand the mechanism of sorption and these studies showed that the addition of functionalized CNT to the polymer increases the absorption of certain types of hydrocarbons. This study demonstrates that carbon nanotubes can be incorporated into a polymer-coated QCM sensor and that composite films may be used to modify the QCM response and selectivity during the analysis of complex hydrocarbon mixtures. 相似文献
13.
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. 相似文献
14.
Hydrazide group has a potential of immobilizing an antibody on a sensor surface in a way that ensures an optimal orientation and efficiency of the antibody. However, a multi-step chemical process, required for the preparation of a hydrazide group, is a barrier to its extensive application. This paper describes a new method to introduce a hydrazide group to a sensor surface by a one-step process using dodecanoic hydrazide. The method is based on an ability of the dodecanoic hydrazide to be incorporated into a hybrid bilayer membrane (HBM) layer, thereby presenting its hydrazide group to the surface. Liposome containing dodecanoic hydrazide was added to a hydrophobic self-assembled monolayer surface of a quartz crystal microbalance for the formation of a HBM. Then, the hydrazide group, presented in the surface of the HBM layer, was utilized for the oriented immobilization of an antibody via its carbohydrate moiety which was partially oxidized prior to the conjugation reaction. Activity and stable status of the incorporated dodecanoic hydrazide was revealed by the efficiency and reproducibility of the resulting immunosensor chip. 相似文献
15.
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. 相似文献
16.
An alternative screening method for haloacetic acids (HAAs) disinfection by-products in drinking water is described. The method is based on the use of piezoelectric quartz crystal microbalance (QCM) transducing system, where the electrode is coated with a trichloacetic acid-molecularly imprinted polymer (TCAA-MIP). This MIP comprises a crosslinked poly(ethyleneglycoldimethacrylate-co-4-vinylpyridine). The coated QCM is able to specifically detect the analytes in water samples in terms of the mass change in relation to acid-base interactions of the analytes with the MIP. The TCAA-MIP coated QCM showed high specificity for the determination of TCAA in aqueous solutions containing inorganic anions, but its sensitivity reduced in water samples containing hydrochloric acid due to a mass loss at the sensor surface. Cross-reactivity studies with HAA analogs (dichloro-, monochloro-, tribromo-, dibromo-, and monobromo-acetic acids) and non-structurally related TCAA molecules (acetic acid and malonic acid) indicated that recognition of the structurally related TCAA compounds by the TCAA-MIP-based QCM is due to a carboxylic acid functional group, and probably involves a combination of both size and shape selectivity. The total response time of sensor is in the order of 10 min. The achieved limits of detection for HAAs (20-50 μg l−1) are at present higher than the actual concentrations found in real-life samples, but below the guidelines for the maximum permissible levels (60 μg l−1 for mixed HAAs). Recovery studies with drinking water samples spiked with TCAA or spiked with mixtures of HAAs revealed the reproducibility and precision of the method. The present work has demonstrated that the proposed assay can be a fast, reliable and inexpensive screening method for HAA contaminants in water samples, but further refinement is required to improve the limits of detection. 相似文献
17.
A novel ceramic nanowires of TiO2 and poly(2-acrylamido-2-methylpropane sulfonate) (TiO2 NWs/PAMPS) composite material films coated on quartz crystal microbalance (QCM) was prepared as a low humidity sensor. The 50 wt.% of TiO2 NWs/PAMPS composite material films showed excellent sensitivity (2.63 −ΔHz/Δppmv) at 31.5 ppmv), linearity (R2 = 0.9959) and acceptable response time (64 s at 34.6 ppmv). The low humidity sensing mechanism was discussed in terms of surface texture and nanostructured morphology of the composite materials. Moreover, the adsorption dynamic analysis, molecular mechanics calculation (association constant), was used to elucidate the effect of adding 50 wt.% TiO2 NWs into PAMPS in the increased sensitivity of low humidity sensing. 相似文献
18.
19.
A new method for the quantitative determination of palladium(II) by the electrochemical quartz crystal microbalance (EQCM) technique has been developed. Using a bare carbon-coated quartz crystal, Pd(II) ions are directly deposited from aqueous solution as palladium metal onto the crystal surface, and the Pd(II) concentration is determined with a detection limit of 0.0156 mM, or 1.66 ppm. No complexing agent or preconcentration of palladium is required for the analysis. The palladium is stripped from the crystal through its electrochemical oxidation, regenerating the crystal for subsequent multi-cycle palladium analyses. A conventional gold-coated quartz crystal was incapable of carrying out the same measurements. The EQCM technique presented is simple, sensitive, and reproducible for the detection of this widely used precious metal. 相似文献
20.
Chengjun Sun 《Surface and interface analysis : SIA》2013,45(11-12):1799-1804
The preparation of a nonporous solid surface for native chemical ligation is described. A cysteine residue is covalently attached to the surface by means of a series of reactions. In a reaction analogous to that used for native chemical ligation, the surface‐attached cysteine residue reacts with a thioester to form an amide linkage. All of the reaction steps except the derivatization of the nonporous solid surface with amino‐ended silane are conducted within the flow cell of a quartz crystal microbalance with dissipation monitoring. This sensitive instrument allows each reaction step to be followed in real time, with simultaneous quantification of the mass added and removed in different steps. The number of protected cysteine residues attached per square nanometer is consistent with the number of protecting groups removed in each deprotection step and also with the number of thioesters reacting with the deprotected cysteine. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献