An electronic-nose is developed based on eight quartz-crystal-microbalance (QCM) gas sensors in a sensor box, and is used to detect Chinese liquors at room temperature. Each sensor is a highly-accurate and highly-sens...An electronic-nose is developed based on eight quartz-crystal-microbalance (QCM) gas sensors in a sensor box, and is used to detect Chinese liquors at room temperature. Each sensor is a highly-accurate and highly-sensitive oscillator that has experienced airflow disturbances under the condition of varying room temperatures due to unstable flow-induced forces on the sensors surfaces. The three-dimensional (3D) nature of the airflow inside the sensor box and the interactions of the airflow on the sensors surfaces at different temperatures are studied by computational fluid dynamics (CFD) tools. Higher simulation accuracy is achieved by optimizing meshes, meshing the computational domain using a fine unstructural tetrahedron mesh. An optimum temperature, 30 ℃, is obtained by analyzing the distributions of velocity streamlines and the static pressure, as well as the flow-induced forces over time, all of which may be used to improve the identification accuracy of the electronic-nose for achieving stable and repeatable signals by removing the influence of temperature.展开更多
Nanoparticles are playing an increasingly important role in the development of biosensors. The sensitivity and performance of biosensors are being improved by using Nanoparticles for their construction. The use of the...Nanoparticles are playing an increasingly important role in the development of biosensors. The sensitivity and performance of biosensors are being improved by using Nanoparticles for their construction. The use of these Nanoparticles has allowed the introduction of many new signal transduction technologies in biosensors. In this report, a comprehensive review of application of nanoparticles in Quartz Crystal Microbalance biosensors is presented. The main advantages of QCM in sensing fields include high sensitivity, high stability, fast response and low cost. In addition, it provides label-free detection capability for bio-sensing applications. Firstly, basic QCM’s design and characterization are described. Next, QCM biosensors based on modification of quartz substrate structure and their applications are digested. Nanoparticles and their utilizationin analysis are then illustrated. These include Nanoparticles in bio applications that cover Nanoparticles in Quartz Crystal Microbalance biosensors.展开更多
We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle ...We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance(QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fspof 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fspwas found and subsequently became one of the most important parameters in the new sensor design.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
An unexpected frequency response for a piezoelectric quartz crystal (PQC) sensor to liquid density and viscosity was reported. For a PQC oscillating in a liquid phase, the frequency shifts (?f ) show a wave-shape re...An unexpected frequency response for a piezoelectric quartz crystal (PQC) sensor to liquid density and viscosity was reported. For a PQC oscillating in a liquid phase, the frequency shifts (?f ) show a wave-shape response to liquid density (ρ) and viscosity (η) in fine structure, if the longitudinal wave effect was not eliminated. This result is different from the well-known linear relationship between of ?f and (ρη)1/2. An oscillating frequency-temperature curve of the sensor was observed and explained.展开更多
We have investigated the interactions between phospholipid monolayers and volatile anest-hatics. Two monolayers (dihexadecyl phosphate (DHP) and dipalmitoyl phosphatidyl choline (DPPC) and two anesthetics (halothane a...We have investigated the interactions between phospholipid monolayers and volatile anest-hatics. Two monolayers (dihexadecyl phosphate (DHP) and dipalmitoyl phosphatidyl choline (DPPC) and two anesthetics (halothane and enflurane) were used to observe these interac-tions using a highly sensitive quartz crystal microbalance (HS-QCM). The concentration of each anesthetic in aqueous solution was kept at 4 mM. The frequency of QCM showed no change when halothane was added to the DHP monolayer, however, it responded and de-creased when interaction occurred with DPPC monolayer. In case of enflurane addition the frequency decreased in both the monolayers of DHP and DPPC. The frequency change followed the following order of monolayer-anesthetic interactions: DHP-halothane <DPPC-halothane <DHP-enflurane <DPPC-enflurane. These re-sults showed that the response of anesthetics to the monolayers i.e. the physisorption not only depends on the anesthetic structure, the type of anesthetic hydrate formed, but also the hydrophilic polar group structure of the monolayer or the monolayer/water interface had an important role in physisorption.展开更多
To address the challenge of achieving both high sensitivity and a high quality factor in quartz crystal microbalance(QCM)humidity sensors,a nanodiamond(ND)/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor was fab...To address the challenge of achieving both high sensitivity and a high quality factor in quartz crystal microbalance(QCM)humidity sensors,a nanodiamond(ND)/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor was fabricated.The material characteristics of ND,Ti_(3)C_(2)MXene,and ND/Ti_(3)C_(2)MXene composite were analyzed by transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The experimental results demonstrated that the hydrophilic ND nanoparticles coated on Ti_(3)C_(2) MXene nanosheet prevented the self-stacking of Ti_(3)C_(2)MXene and enhanced the sensitivity of Ti_(3)C_(2) MXene-based QCM humidity sensor.Moreover,the high mechanical modulus of Ti_(3)C_(2) MXene material helped ND/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor to achieve a high quality factor(>20,000).ND/Ti_(3)C_(2)MXene compositecoated QCM humidity sensor exhibited a sensitivity of 82.45 Hz/%RH,a humidity hysteresis of 1.1%RH,fast response/recovery times,acceptable repeatability,and good stability from 11.3%RH to 97.3%RH.The response mechanism of ND/Ti_(3)C_(2) MXene composite-coated QCM humidity sensor was analyzed in combination with a bi-exponential kinetic adsorption model.Finally,the potential application of ND/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor was demonstrated through its frequency response to wooden blocks with different moisture contents.展开更多
We are developing methods to quantify antibody interactions that include a quartz crystal microbalance (QCM) system to measure, on a molecular basis, the interaction of p53 and anti-p53 antibodies. Previously, as a mo...We are developing methods to quantify antibody interactions that include a quartz crystal microbalance (QCM) system to measure, on a molecular basis, the interaction of p53 and anti-p53 antibodies. Previously, as a model system, we developed a measurement device consisting of p53 protein (human wild type), characterized by mass spectroscopy and immobilized at various concentrations on a glass slide. The device is designed as a control to be used with immunohistochemical (IHC) assays that incorporate commercially available anti-p53 antibodies and probes. In the current study, p53 protein is covalently immobilized on a silicon dioxide-coated quartz crystal and the resonance frequency shift is followed in-situ. The functionalized sensor is then incubated with the anti-p53 antibody, which provides a direct gravimetric measure of the antibody-antigen binding. This previously described method allows the comparison of the surface immobilized protein concentrations with estimates obtained by fluorescence measurement. The p53 functionalized QCM system offers an independent measure of surface immobilized protein concentration and is essential in development of our IHC calibration prototypes. These results provide a benchmark for comparing antibody systems that may be used in developing other molecular diagnostic assays such as immunocytochemical analysis and the detection of biomarker proteins in blood and urine.展开更多
A multimode-quartz-crystal oscillator was developed to excite stable dual-mode resonance at different frequencies: The oscillation of the 3rd harmonic resonance of the principle C-mode and an additional resonance B-mo...A multimode-quartz-crystal oscillator was developed to excite stable dual-mode resonance at different frequencies: The oscillation of the 3rd harmonic resonance of the principle C-mode and an additional resonance B-mode of SC-cut crystal. Harmonic combinations of the 3rd and fundamental mode of B-mode with the 3rd harmonics of C-mode are demonstrated. The measurement of the temperature dependence of the oscillation frequency is demonstrated along with the stability determined by root Allan variance. Dependence on the open conductance of the active circuit and the dependence on the coupling capacitors are discussed.展开更多
Based on the needs of the oscillation equation and frequency stability, three oscillation conditions are proposed and have been experimentally verified for an electrode-separated piezoelectric sensor (ESPS ) in electr...Based on the needs of the oscillation equation and frequency stability, three oscillation conditions are proposed and have been experimentally verified for an electrode-separated piezoelectric sensor (ESPS ) in electrolyte solutions. The present paper covers the dependence of the minimum cell constant needed for the ESPS on solution conductivity. The oscillation conditions of the classical liquid piezoelectric sensor are discussed. The 'cease-to-oscillate' frequencies of the ESPS were measured.展开更多
Acetylcholinesterase (AChE) was immobilized on multilayer films assembled by poly diallyldimethylammonium chloride (PDDA) and ι-carrageenan (IC) on silver-coated crystal electrode surfaces to detect the chlorpyrifos ...Acetylcholinesterase (AChE) was immobilized on multilayer films assembled by poly diallyldimethylammonium chloride (PDDA) and ι-carrageenan (IC) on silver-coated crystal electrode surfaces to detect the chlorpyrifos belonging to the organophosphates pesticide.Mass sensitive quartz crystal microbalance (QCM) was used to study the effect of AChE concentration and pH of phosphate buffer solution on immobilized acetylcholinesterase.The optimized conditions were as follows: pH was 6.0 which was near isoelectric ...展开更多
n oscillation condition was proposed and experimentally verified for an elec-troderaeparated piezoelectric sensor (ESPS) in non-electrolyte liquid, it was ex-pressed as , where C_s is the solution capaci-tance , R_q, ...n oscillation condition was proposed and experimentally verified for an elec-troderaeparated piezoelectric sensor (ESPS) in non-electrolyte liquid, it was ex-pressed as , where C_s is the solution capaci-tance , R_q, C_o and w are the motional resistance , static capacitance and resonant an-gle frequency of the crystal , respectively. And Y-tgθ, where θ is the phase shift inthe oscillator. The relationships between the minimum cell constant needed for ES-PS to oscillate and each of the following parameters, permittivity, density and vis-cosity of the liquid as well as the oscillator phase shift were discussed. The″ cease-to-oscillate″ frequency of ESPS was measured. The oscillation ability of ESPS in-creases with increasing permittivity or decreasing density and viscosity of the liq-uid. An oscillator with a larger Y value is helpful to drive ESPS.展开更多
As humidity is one of the most widely demanded environmental parameters,the precision of its detection is significant.An advanced humidity sensor will improve the validity of the humidity monitoring system.In this stu...As humidity is one of the most widely demanded environmental parameters,the precision of its detection is significant.An advanced humidity sensor will improve the validity of the humidity monitoring system.In this study,a facile chemical layer-by-layer self-assembly(CLS)method was developed for fabricating graphene oxide(GO)/polyethyleneimine(PEI)multilayer films.Owing to the chemical bonding between the PEI and GO,and the intrinsic stickiness of the PEI,layered films with different numbers of layers were successfully prepared using the CLS method and confirmed through ultraviolet-visible(UV-Vis)spectroscopy and the mass loading of quartz crystal microbalance(QCM).Morphological measurements revealed that the roughness and thickness of the films increased exponentially with the number of bilayers.The GO/PEI films were deposited on QCM electrodes using the CLS method to produce the humidity sensors.The humidity measurement results showed a high sensitivity(37.84 Hz/%RH)and rapid response/recovery(<5 s/8 s)of the optimal sensor,which was superior to that of recently developed QCM sensors.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.61876059 and U1501251)
文摘An electronic-nose is developed based on eight quartz-crystal-microbalance (QCM) gas sensors in a sensor box, and is used to detect Chinese liquors at room temperature. Each sensor is a highly-accurate and highly-sensitive oscillator that has experienced airflow disturbances under the condition of varying room temperatures due to unstable flow-induced forces on the sensors surfaces. The three-dimensional (3D) nature of the airflow inside the sensor box and the interactions of the airflow on the sensors surfaces at different temperatures are studied by computational fluid dynamics (CFD) tools. Higher simulation accuracy is achieved by optimizing meshes, meshing the computational domain using a fine unstructural tetrahedron mesh. An optimum temperature, 30 ℃, is obtained by analyzing the distributions of velocity streamlines and the static pressure, as well as the flow-induced forces over time, all of which may be used to improve the identification accuracy of the electronic-nose for achieving stable and repeatable signals by removing the influence of temperature.
文摘Nanoparticles are playing an increasingly important role in the development of biosensors. The sensitivity and performance of biosensors are being improved by using Nanoparticles for their construction. The use of these Nanoparticles has allowed the introduction of many new signal transduction technologies in biosensors. In this report, a comprehensive review of application of nanoparticles in Quartz Crystal Microbalance biosensors is presented. The main advantages of QCM in sensing fields include high sensitivity, high stability, fast response and low cost. In addition, it provides label-free detection capability for bio-sensing applications. Firstly, basic QCM’s design and characterization are described. Next, QCM biosensors based on modification of quartz substrate structure and their applications are digested. Nanoparticles and their utilizationin analysis are then illustrated. These include Nanoparticles in bio applications that cover Nanoparticles in Quartz Crystal Microbalance biosensors.
基金Project supported by the National High Technology Research and Developmem Program of China ~Grant No. 2013AA030901）.
文摘We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance(QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fspof 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fspwas found and subsequently became one of the most important parameters in the new sensor design.
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.
基金supported by the National Natural Science Foundation of China(No.20275021)
文摘An unexpected frequency response for a piezoelectric quartz crystal (PQC) sensor to liquid density and viscosity was reported. For a PQC oscillating in a liquid phase, the frequency shifts (?f ) show a wave-shape response to liquid density (ρ) and viscosity (η) in fine structure, if the longitudinal wave effect was not eliminated. This result is different from the well-known linear relationship between of ?f and (ρη)1/2. An oscillating frequency-temperature curve of the sensor was observed and explained.
文摘We have investigated the interactions between phospholipid monolayers and volatile anest-hatics. Two monolayers (dihexadecyl phosphate (DHP) and dipalmitoyl phosphatidyl choline (DPPC) and two anesthetics (halothane and enflurane) were used to observe these interac-tions using a highly sensitive quartz crystal microbalance (HS-QCM). The concentration of each anesthetic in aqueous solution was kept at 4 mM. The frequency of QCM showed no change when halothane was added to the DHP monolayer, however, it responded and de-creased when interaction occurred with DPPC monolayer. In case of enflurane addition the frequency decreased in both the monolayers of DHP and DPPC. The frequency change followed the following order of monolayer-anesthetic interactions: DHP-halothane <DPPC-halothane <DHP-enflurane <DPPC-enflurane. These re-sults showed that the response of anesthetics to the monolayers i.e. the physisorption not only depends on the anesthetic structure, the type of anesthetic hydrate formed, but also the hydrophilic polar group structure of the monolayer or the monolayer/water interface had an important role in physisorption.
基金financially supported by the Project funded by the National Natural Science Foundation of China(No.61401047)the China Postdoctoral Science Foundation(No.2018M633349)+1 种基金the Oversea Students Funding Project of the Department of Human Resources and Social Security of Sichuanthe Scientific Research Foundation of CUIT(No.KYQN202210)。
文摘To address the challenge of achieving both high sensitivity and a high quality factor in quartz crystal microbalance(QCM)humidity sensors,a nanodiamond(ND)/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor was fabricated.The material characteristics of ND,Ti_(3)C_(2)MXene,and ND/Ti_(3)C_(2)MXene composite were analyzed by transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The experimental results demonstrated that the hydrophilic ND nanoparticles coated on Ti_(3)C_(2) MXene nanosheet prevented the self-stacking of Ti_(3)C_(2)MXene and enhanced the sensitivity of Ti_(3)C_(2) MXene-based QCM humidity sensor.Moreover,the high mechanical modulus of Ti_(3)C_(2) MXene material helped ND/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor to achieve a high quality factor(>20,000).ND/Ti_(3)C_(2)MXene compositecoated QCM humidity sensor exhibited a sensitivity of 82.45 Hz/%RH,a humidity hysteresis of 1.1%RH,fast response/recovery times,acceptable repeatability,and good stability from 11.3%RH to 97.3%RH.The response mechanism of ND/Ti_(3)C_(2) MXene composite-coated QCM humidity sensor was analyzed in combination with a bi-exponential kinetic adsorption model.Finally,the potential application of ND/Ti_(3)C_(2)MXene composite-coated QCM humidity sensor was demonstrated through its frequency response to wooden blocks with different moisture contents.
文摘We are developing methods to quantify antibody interactions that include a quartz crystal microbalance (QCM) system to measure, on a molecular basis, the interaction of p53 and anti-p53 antibodies. Previously, as a model system, we developed a measurement device consisting of p53 protein (human wild type), characterized by mass spectroscopy and immobilized at various concentrations on a glass slide. The device is designed as a control to be used with immunohistochemical (IHC) assays that incorporate commercially available anti-p53 antibodies and probes. In the current study, p53 protein is covalently immobilized on a silicon dioxide-coated quartz crystal and the resonance frequency shift is followed in-situ. The functionalized sensor is then incubated with the anti-p53 antibody, which provides a direct gravimetric measure of the antibody-antigen binding. This previously described method allows the comparison of the surface immobilized protein concentrations with estimates obtained by fluorescence measurement. The p53 functionalized QCM system offers an independent measure of surface immobilized protein concentration and is essential in development of our IHC calibration prototypes. These results provide a benchmark for comparing antibody systems that may be used in developing other molecular diagnostic assays such as immunocytochemical analysis and the detection of biomarker proteins in blood and urine.
文摘A multimode-quartz-crystal oscillator was developed to excite stable dual-mode resonance at different frequencies: The oscillation of the 3rd harmonic resonance of the principle C-mode and an additional resonance B-mode of SC-cut crystal. Harmonic combinations of the 3rd and fundamental mode of B-mode with the 3rd harmonics of C-mode are demonstrated. The measurement of the temperature dependence of the oscillation frequency is demonstrated along with the stability determined by root Allan variance. Dependence on the open conductance of the active circuit and the dependence on the coupling capacitors are discussed.
文摘Based on the needs of the oscillation equation and frequency stability, three oscillation conditions are proposed and have been experimentally verified for an electrode-separated piezoelectric sensor (ESPS ) in electrolyte solutions. The present paper covers the dependence of the minimum cell constant needed for the ESPS on solution conductivity. The oscillation conditions of the classical liquid piezoelectric sensor are discussed. The 'cease-to-oscillate' frequencies of the ESPS were measured.
基金Supported by the State Key Lab of Polymer Physics and Chemistry,Changchun Institute of Applied Chemistry Chinese Academy of Sciences
文摘Acetylcholinesterase (AChE) was immobilized on multilayer films assembled by poly diallyldimethylammonium chloride (PDDA) and ι-carrageenan (IC) on silver-coated crystal electrode surfaces to detect the chlorpyrifos belonging to the organophosphates pesticide.Mass sensitive quartz crystal microbalance (QCM) was used to study the effect of AChE concentration and pH of phosphate buffer solution on immobilized acetylcholinesterase.The optimized conditions were as follows: pH was 6.0 which was near isoelectric ...
文摘n oscillation condition was proposed and experimentally verified for an elec-troderaeparated piezoelectric sensor (ESPS) in non-electrolyte liquid, it was ex-pressed as , where C_s is the solution capaci-tance , R_q, C_o and w are the motional resistance , static capacitance and resonant an-gle frequency of the crystal , respectively. And Y-tgθ, where θ is the phase shift inthe oscillator. The relationships between the minimum cell constant needed for ES-PS to oscillate and each of the following parameters, permittivity, density and vis-cosity of the liquid as well as the oscillator phase shift were discussed. The″ cease-to-oscillate″ frequency of ESPS was measured. The oscillation ability of ESPS in-creases with increasing permittivity or decreasing density and viscosity of the liq-uid. An oscillator with a larger Y value is helpful to drive ESPS.
基金financially supported by the National Natural Science Foundation of China(No.U19A2070)the National Science Funds for Excellent Young Scholars of China(No.61822106)the National Science Funds for Creative Research Groups of China(No.61421002)。
文摘As humidity is one of the most widely demanded environmental parameters,the precision of its detection is significant.An advanced humidity sensor will improve the validity of the humidity monitoring system.In this study,a facile chemical layer-by-layer self-assembly(CLS)method was developed for fabricating graphene oxide(GO)/polyethyleneimine(PEI)multilayer films.Owing to the chemical bonding between the PEI and GO,and the intrinsic stickiness of the PEI,layered films with different numbers of layers were successfully prepared using the CLS method and confirmed through ultraviolet-visible(UV-Vis)spectroscopy and the mass loading of quartz crystal microbalance(QCM).Morphological measurements revealed that the roughness and thickness of the films increased exponentially with the number of bilayers.The GO/PEI films were deposited on QCM electrodes using the CLS method to produce the humidity sensors.The humidity measurement results showed a high sensitivity(37.84 Hz/%RH)and rapid response/recovery(<5 s/8 s)of the optimal sensor,which was superior to that of recently developed QCM sensors.
