Electrode-separated Piezoelectric Sensor Research Articles

An electrode-separated piezoelectric immunosensor array with signal enhancement based on enzyme catalytic deposition of palladium nanoparticles and electroless deposition nickel-phosphorus

A differential piezoelectric immunosensor array was reported with signal enhancement based on the biometallization of palladium nanoparticles (Pd NPs) and successive electroless deposition Ni-P layer. In this strategy, the primary antibody probes were immobilized on the aminated quartz surface in an electrode-separated piezoelectric sensor (ESPS). After bounding with the corresponding antigen and alkaline phosphatase (ALP) conjugated second antibody, the ALP in the sandwich-type immunocomplex can catalyze the substrate of p-aminophenyl phosphate to generate p-aminophenol, which reduces Pd(II) in solution to Pd NPs onto the quartz surface. A successive signal amplification was performed by Pd NPs- promoted catalytic electroless deposition of Ni-P layer. A differential measurement mode was employed to eliminate the influence of non-mass effects, including the changes in conductivity, viscosity, density and temperature of the solution, as well as the baselines draft of piezoelectric sensors. The responses of the differential ESPS in fundamental frequency, third and fifth overtones were compared. The proposed method was applied to the determination of human IgG with a detection limit of 1pg/mL. Compared with biometallization of Pd NPs, the sensitivity is enhanced further by three orders of magnitude due to high activation energy in Ni-P deposition reaction and low baseline draft in differential measurement mode.

Real time monitor electroless plating of Ni–P film on quartz surface by an electrode-separated piezoelectric sensor

The kinetics related to an electroless Ni–P deposition on quartz surface was monitored by an electrode-separated piezoelectric sensor (ESPS). It was shown that the mass changes during the initial grease removing and quartz coarsening processes follow the exponential decay and linear decrease models, respectively. The initial Ni–P plating process consists of four stages: an induction period, an acceleration period, a deceleration period and a stationary period. In the corrosion process of the Ni–P film in 1 mol/L HCl, the dissolving rate decreases with contact time in the initial 10 min and then approaches to a stable level of 0.12 nm/min. The wearing rate of the Ni–P film in Al 2O 3 polishing powder is much larger than the dissolving rate in 1 mol/L HCl and decreases slightly with time. The ESPS technique is an effective tool for in situ monitoring of the mass changes in electroless plating on quartz material.

Effect of inorganic positive ions on the adsorption of surfactant Triton X-100 at quartz/solution interface

The electrode-separated piezoelectric sensor (ESPS), an improved setup of quartz crystal microbalance (QCM), has been employed to investigate the adsorption behavior of nonionic surfactant Triton X-100 at the hydrophilic quartz-solution interface in mineralized water medium in situ, which contained CaCl2 0.01 mol·L−1, MgCl2 0.01 mol·L−1, NaCl 0.35 mol·L−1. In a large scale of surfactant concentration, t effects of Ca2+, Mg2+ and Na+ on the adsorption isotherm and kinetics are obviously different. In aqueous solution containing NaCl only, adsorption of Triton X-100 on quartz-solution interface is promoted, both adsorption rate and adsorption amount increase. While in mineralized water medium, multivalent positive ions Ca2+ and Mg2+ are firmly adsorbed on quartz-solution interface, result in the increasing of adsorption rate and adsorption amount at low concentration of surfactant and the peculiar desorption of surfactant at high concentration of Triton X-100. The results got by solution depletion method are in good agreement with which obtained by ESPS. The “bridge” and “separate” effect of inorganic positive ions on the adsorption and desorption mechanism of Triton X-100 at the quartz-solution interface is discussed with molecular dynamics simulations (MD), flame atomic absorption spectrometry (FAAS) and atomic force microscopy (AFM) methods.

Impedance analysis of an electrode-separated piezoelectric sensor as a surface-monitoring technique for gelatin adsorption on quartz surface

The early events pertaining to gelatin adsorption and desorption onto quartz surfaces were studied, employing an electrode-separated piezoelectric sensor (ESPS). The adsorption of gelatin on a quartz crystal surface corresponds to a mass increase, which can be monitored in real time by the changes in the impedance parameters of the ESPS. It was shown that the adsorption of gelatin on a quartz surface is partly irreversible with respect to the dilution of the bulk phase. The observed adsorption kinetics is compatible with a mechanism that involves adsorption, desorption, and transformation from a reversible adsorption state to irreversible one. A progressive approach method was established to simulate the adsorption process. The adsorption densities and kinetic parameters in the early adsorption process were obtained from the responses of the ESPS in the adsorption process. The influence of pH and ionic strength was tested. A comparison with the Langmuir adsorption model was made.

Estimation the kinetics parameters for non-specific adsorption of fibrinogen on quartz surface from the response of an electrode-separated piezoelectric sensor

In the configuration of an electrode-separated piezoelectric sensor (ESPS), the quartz crystal surface is in a direct contact with the liquid phase. The adsorption of fibrinogen (FN) on quartz crystal surface corresponds to a mass increase, which can be monitored in situ by the decreases in the oscillating frequency of the ESPS. The adsorption densities and kinetics parameters were obtained from the responses of the ESPS in adsorption process. It was shown that the adsorption of FN on quartz surface is partly irreversible with respect to the dilution of bulk phase. The observed adsorption kinetics is compatible with a mechanism that involves an adsorption, desorption and transform from reversible adsorption state to irreversible one. A progressive approach method was established to simulate the adsorption process. The rate constants for adsorption, k a=(8.03±0.92)×10 3×10 4 mol −1 l s −1, desorption, k d=(6.76±0.76)×10 −3 s −1, and transform, k f=(5.32±0.21)×10 −4 s −1 were obtained under the experimental conditions. A comparison with Langmuir model was made.

Impedance analysis of an electrode-separated piezoelectric sensor as a surface monitoring technique for surfactant adsorption on quartz surface.

This paper describes the measurement of the kinetics of adsorption of sodium dodecyl sulfate (SDS), an anionic surfactant, onto a quartz surface with a pre-adsorbed layer of Ca2+ as an ion bridge, using an electrode-separated piezoelectric sensor (ESPS). An impedance analysis method was employed to characterize the responses of the ESPS. The impedance and frequency parameters of the ESPS were examined as functions of the conductivity, permittivity, viscosity and density of the liquid. The adsorption process of SDS onto the quartz surface resulted in an increase in both the mass and energy dissipation of the oscillating quartz crystal. The adsorption densities could be estimated by the ESPS method after taking into consideration the effects of surface viscosity and roughness. The adsorption and desorption rate constants of SDS onto the quartz surface were calculated as ka = (88.1 +/- 0.26) mol(-1) L s(-1) and kd = (4.92 +/- 0.53) x 10(-3) s(-1), respectively, based on the Langmuir model. ESPS was shown to be a powerful means of examining anionic surfactant adsorption to the solid/liquid interface.

An Electrode-Separated Piezoelectric Sensor as a Surface Monitoring Technique for Anionic Surfactant Adsorption on Quartz Surface

In the configuration of an electrode-separated piezoelectric sensor (ESPS), the quartz crystal surface is in a direct contact with the liquid phase. With the pre-adsorption of Ca2+ as the ionic bridge, anionic surfactant can adsorb on the negatively charged quartz surface (pH > 2.0). The adsorption process of sodium dodecyl benzenesulfonate (SDBS) was monitored in real time with the ESPS method. It was shown that the adsorption of SDBS on quartz surface by Ca2+ inducement was reversible with respective to the dilution of solution phase. The adsorption behavior can be analyzed using Langmuir model. The adsorption and desorption rate constants were estimated to be ka = (108.4 ± 6.4) mol−1L s−1 and kd = (2.57 ± 0.32) × 10−3 s−1, respectively. The observed adsorption densities in the ESPS method were significantly greater than the true ones. The influence on surface roughness of the quartz disc on adsorption densities should be corrected by adding a calibration coefficient in the Sauerbrey equation. The saturation adsorption density is 0.223 µg/cm2 for SDBS on quartz surface. Double layer occurs for the adsorption of SDBS on quartz surface.

Adsorption studies of cationic starch onto quartz surface through an electrode-separated piezoelectric sensor

In the construction of an electrode-separated piezoelectric sensor (ESPS), the quartz surface is in direct contact with the liquid phase. The negatively charged quartz crystal surface can adsorb cationic starch. This adsorption process was in situ monitored from the frequency shift of the ESPS. It was shown that the adsorption of cationic starch onto the quartz surface is reversible with respect the dilution of the bulk phase. The adsorption behavior can be described by Langmuir model. The adsorption density and kinetics parameters were estimated from the frequency responses of the ESPS. The influence of pH and ionic strength on adsorption parameters was investigated. It was shown that the influence of pH on the adsorption rate was slight. With increasing ionic strength, the rate constants for adsorption and desorption increase, but the adsorption equilibrium constant and saturation adsorption density decrease. The adsorption equilibrium constant and adsorption density reach a maximum in buffer of pH 10.

Study of cationic polyelectrolyte adsorption onto quartz surface using an electrode-separated piezoelectric sensor

The adsorption of a cationic polyelectrolyte onto quartz surface from aqueous solution has been studied using an electrode-separated piezoelectric sensor (ESPS). The adsorption process has been monitored in situ in Britton-Robinson buffer at different concentrations of polyelectrolyte. The adsorption mechanism is described. The adsorption density is influenced by pH and electrolyte concentration.

Effects of longitudinal wave on the resonance behavior of an electrode-separated piezoelectric sensor in liquids

An electrode-separated piezoelectric sensor (ESPS) was constructed and its operation in the liquid phase was characterized. When the surface of the separated-electrode reflects the weak longitudinal wave (LW) back to the surface of the quartz disc where it was generated, the interaction of the reflected LW with the main thickness-shear wave of the quartz disc is a potential error source. In this study, the influence of the LW effect on the response of the ESPS was investigated by an impedance analysis method. It was shown that all the impedance response parameters shift periodically as a function of the distance between the separated-electrode and the quartz crystal. The LW effect depends markedly on the surface conditions, including the shape, area, position, angle and roughness, of the separated-electrode. When a rough, non-parallel or ball electrode was used, the influence of the LW could be decreased greatly. The influence of the air/liquid interface on the reflection of the LW was efficiently screened in the ESPS.

Gravimetric monitoring of adsorption behavior of tetrakis(methylpyrdiniumyl)porphyrin onto quartz crystal surface using an electrode-separated piezoelectric sensor

The adsorption behavior of 5,10,15,20-tetrakis (4-N-methylpyridiniumyl)-porphyrin (H2TMPyP) from aqueous solutions onto a quartz crystal interface was investigated in situ using an electrode-separated piezoelectric sensor (ESPS). With H2TMPyP adsorbed onto quartz crystal surface of the ESPS, its oscillating frequency decreases linearly with increasing adsorption amount. The adsorption densities obtained in the ESPS method were greater than those determined in a solution depletion method. The influence of surface roughness of quartz crystal and bulk solution properties on the measurement of adsorption density in the ESPS method was discussed.

In SituMonitoring of Adsorption of Lysozyme onto Quartz Using an Electrode-Separated Piezoelectric Sensor

The adsorption of lysozyme from phosphate-buffered saline (pH 7.0) onto a quartz crystal interface was investigatedin situusing an electrode-separated piezoelectric sensor (ESPS). Increasing amounts of lysozyme adsorbed onto a quartz crystal surface resulted in linearly decreasing oscillating frequencies of the ESPS. The lysozyme adsorbed is partially desorbed after rinsing with the phosphate-buffered saline. The amounts adsorbed reversibly and irreversibly were estimated. The influence of the surface roughness of the quartz crystal on the adsorption density measurement is discussed.

Adsorption studies of dodecylamine at the quartz interface using an electrode-separated piezoelectric sensor

The adsorption process of dodecylammonium chloride (DAC) from aqueous solutions onto a quartz crystal interface was investigated in situ using an electrode-separated piezoelectric sensor (ESPS). Increasing amounts of DAC adsorbed onto a quartz crystal surface resulted in linearly decreasing oscillating frequencies of the ESPS. The adsorption density can be monitored by the frequency decrease. The adsorption density obtained by calculation using the Sauerbrey equation in the ESPS method is greater than that in solution depletion method. A calibration coefficient is added into the Sauerbrey equation to correct the influence of surface roughness of the quartz crystal on the adsorption density. The influence of solution properties on the adsorption density measurement was discussed. A dependence of the adsorption density on pH was reported.

Oscillation frequency characteristic of an electrode-separated piezoelectric sensor and application to the determination of the adsorption of a surfactant on a quartz surface

The oscillation frequency equation for an electrode-separated piezoelectric sensor (ESPS) in a liquid phase was derived theoretically and verified experimentally. The dependences of the frequency shifts on conductivity, permittivity, density and viscosity of the liquid were investigated. The ESPS was applied to determine in situ the adsorption amount of hexadecetyltrimethylammonium bromide on a quartz surface.

Determination of Surfactant Adsorbed on a Quartz Surface by an Electrode-separated Piezoelectric Sensor

S. Dazhong, K. Qi, Z. Xiaoli, W. Lizeng and M. Chengsong, Anal. Commun., 1997, 34, 97 DOI: 10.1039/A700507E

Influence of oscillator phase on oscillation frequency and sensitivity of an electrode‐separated piezoelectric Sensor

AbstractTheoretical consideration was proposed for the influences of the oscillator phase on the response nature of an electrode‐separated piezoelectric sensor (ESPS) to liquid properties and verified experimentally. For the oscillators with different phases, the oscillation frequency of the ESPS may increase, maintain nearly constant or decrease with increasing conductivity in low conductivity solutions. The sensitivity of response to density and viscosity increases slightly with increasing oscillator phase. The response to permittivity depends hardly on the oscillator phase. In addition, the dependence of the oscillation frequency of the ESPS on the supply voltage of the oscillator was explained. The ESPS was used to determine atropine sulfate with a detection limit of 1.6·10–7 mol/L.

Frequency-temperature coefficient of an electrode-separated piezoelectric sensor in the liquid phase

Abstract The frequency-temperature coefficient of an electrode-separated piezoclectric sensor (ESPS) was derived theoretically and verified experimentally over the temperature range 10–50°C. The frequency-temperature coefficient of an ESPS in an electrolyte solution is strongly dependent on the conductivity of the solution. A near-zero frequency-temperature coefficient can be obtained under certain solution conditions. In a non-electrolyte solution, the frequency-temperature coefficient of the ESPS is similar to that of a normal quartz crystal microbalance.

Frequency characteristics of an electrode-separated piezoelectric crystal sensor in contact with a liquid

The equations characterizing the frequency response of an electrode-separated piezoelectric crystal (ESPC) sensor, with one side in contact with a liquid, to the properties of the liquid were derived from an electric equivalent circuit model and supported by experiments. The frequency shift of the ESPC can provide information on the permittivity, conductivity, density and viscosity of the liquid.