采用聚吡咯修饰的QCM型三甲胺气体传感器

三甲胺是评估肉类食品新鲜度的重要指标之一,并且临床上也比较值得关注,因而三甲胺的检测具有十分重要的意义,为此,我们采用乳聚法制备了聚吡咯材料,并将其涂敷在晶振电极表面后制得敏感石英晶体微天平(QCM).根据敏感QCM和参比QCM间的频率差变化来实现气体的检测.在室温条件下,该气体传感器对三甲胺气体具有较明显的响应.实验从灵敏度、重现性、选择性和稳定性等方面出发,对该传感器的的性能进行了评价.结果表明,虽然传感器的制备方法简单,但它的性能优异.     

ZnO纳米棒修饰的QCM气体传感器检测NH_3研究

主要介绍了ZnO纳米棒修饰的石英晶体微天平(QCM)气体传感器的制备与测试。采用两步法在石英晶振片表面制备直径为100 nm的ZnO纳米棒敏感膜,构成QCM NH3传感器。检测系统为自主研发的基于LabVIEW平台的QCM气体传感器频率测试软件。检测NH3的体积分数为5×10-6~50×10-6,响应时间均在10 s以内,最大频差值为10.9 Hz,响应最大频差值与NH3体积分数呈现良好的线性关系。室温条件下,ZnO纳米棒敏感膜可以完全实现吸附解吸过程,具有可逆性。该传感器性能稳定,响应灵敏,具有重复性。     

涂敷脲醛树脂的石英晶体微天平湿度传感器

在碱性条件下预先合成脲醛树脂单体,然后在酸性条件下于石英晶体的电极上原位合成脲醛树脂高分子薄膜,制备了石英晶体微天平湿度传感器。同时考察敏感膜厚度对检测灵敏度的影响以及传感器的响应特性、重复性和稳定性。试验结果表明:涂敷脲醛树脂薄膜的传感器频率随测试的相对湿度变化明显,传感器具有良好的重复性和稳定性。制作的湿度传感器可应用于实际的生产、生活中。     

Gas sensing properties at room temperature of a quartz crystal microbalance coated with ZnO nanorods

Gas sensors based on a quartz crystal microbalance (QCM) coated with ZnO nanorods were developed for detection of NH₃ at room temperature. Vertically well-aligned ZnO nanorods were synthesized by a novel wet chemical route at a low temperature of 90 °C, which was used to grow the ZnO nanorods directly on the QCM for the gas sensor application. The morphology of the ZnO nanorods was examined by field-emission scanning electron microscopy (FE-SEM). The diameter and length of the nanorods were 100 nm and 3 μm, respectively. The QCM coated with the ZnO nanorods gas sensor showed excellent performance to NH₃ gas. The frequency shift (Δf) to 50 ppm NH₃ at room temperature was about 9.1 Hz. It was found that the response and recovery times were varied with the ammonia concentration. The fabricated gas sensors showed good reproducibility and high stability. Moreover, the sensor showed a high selectivity to ammoniac gas over liquefied petroleum gas (LPG), nitrous oxide (N₂O), carbon monoxide (CO), nitrogen dioxide (NO₂), and carbon dioxide (CO₂).     

Formaldehyde sensors based on nanofibrous polyethyleneimine/bacterial cellulose membranes coated quartz crystal microbalance

A novel formaldehyde sensor based on nanofibrous polyethyleneimine (PEI)/bacterial cellulose (BC) membranes coated quartz crystal microbalance (QCM) has been successfully fabricated. The nanoporous three-dimensional PEI/BC membranes are composed of nanofibers with diameter of 30-60 nm. The sensor showed high sensitivity with good linearity and exhibited a good reversibility and repeatability towards formaldehyde in the concentration range of 1-100 ppm at room temperature. Moreover, the results showed that the sensing properties were mainly affected by the content of PEI component in nanofibrous membranes, concentration of formaldehyde and relative humidity. Additionally, the nanofibrous PEI/BC membrane coated QCM sensors exhibited a good selectivity to formaldehyde when tested with competing vapors. The simple and feasible method to prepare and coat the PEI/BC sensing membranes on QCM makes it promising for mass production at a low cost.     

基于QCM的湿度传感器等效电路模型研究

基于石英晶体微天平(QCM)的湿度传感器是一种以石英晶体为核心元件的新型高灵敏度传感器.根据气相中晶体振荡电路的起振和稳定条件,对晶体表面敏感薄膜吸附水分时等效电路参数的变化进行建模,得到了一种新型的基于QCM的湿度传感器等效电路模型.通过电路仿真软件PSPICE对模型进行仿真,并搭建QCM湿度传感器实验测量平台,结果验证了基于QCM的湿度传感器等效电路模型的有效性和正确性,对QCM湿度传感器的振荡电路的进一步设计和优化具有指导意义.     

基于PVDF膜的QCM对DMMP的气敏特性研究

神经性毒剂是化学战剂的重要分支.为了检测神经性毒剂模拟剂甲基膦酸二甲酯(DMMP),使用毛细管在压电石英晶体(QCM)的电极上滴涂上不同质量的聚偏氟乙烯(PVDF)溶液,干燥后作为敏感膜.室温下测试QCM对不同浓度的DMMP的响应情况,发现QCM的频率变化与气体浓度有着良好的线性关系.该实验结果表明,PVDF可以作为检测DMMP的很好的敏感材料.     

Designing of MIP-based QCM sensor for the determination of Cu(II) ions in solution

A novel quartz crystal microbalance (QCM) sensor with a high selectivity and sensitivity has been developed for the determination of Cu(II) ions, based on the modification of Cu(II) ion-imprinted polymer (Cu(II)-IIP) film onto a quartz crystal. The performance of the developed MIP-QCM sensor was evaluated and the results indicated that a sensitive MIP-QCM sensor could be fabricated. The obtained MIP-QCM sensor presents high-selectivity monitoring of Cu(II) ions, better reproducibility, shorter response time (6 min), wider linear range (0.001–50 μM) and lower detection limit (8 × 10⁻⁴ μM). The practical analysis of the MIP-QCM sensor confirms the feasibility of Cu(II) determination in wastewater.     

一种新型石英晶振微天平水果气体传感器研究

为监测水果在仓储、运输等过程中的新鲜程度,研制了一种石英晶振微天平（QCM）气体传感器。以基频6 MHz的石英晶体为基片,运用一步原位聚合法在其上沉积了对甲苯磺酸（TSA）掺杂聚苯胺气敏薄膜,制作出QCM水果气体传感器。搭建了测试平台,设计了相应的起振、整形、差频、频压转换及数据采集电路。在室温下,测试了该传感器对放置不同天数的苹果释放气体的敏感特性。实验结果表明,在一定范围内,TSA掺杂浓度增加会改善传感器的气敏性能。传感器对放置不同天数的苹果释放气具有不同的响应特性,且具有灵敏度高、线性度好、响应速度快、重复性好等优点,有望在水果仓储运输方面得以应用。     

基于LiCl湿敏涂层的QCM湿度传感特性的研究

对0.2%质量比LiCl薄膜涂层的QCM湿度传感单元湿敏特性进行了系统性的研究。研究结果表明:0.2%质量比LiCl—QCM的湿度传感单元的线性测量范围为13%～94%RH,克服了常规LiCl湿敏材料传感单元量程窄的缺点。另外,此湿度传感单元还具有重复性好、灵敏度高、湿滞小(小于10 Hz)、数字频率化输出等优点,因而,具有较好的潜在应用前景。     

Characterization and analytical validation of a microcantilever-based sensor for the determination of total carbonate in soil samples

A microcantilever device has been used as a miniaturized sensor for the determination of total carbonate in soil samples. The method is based on the selective generation of CO₂ (g) from samples and the measure of the pressure effect on the microcantilever sensor located in a closed system. The experimental set-up uses a manifold including the sample reaction minichamber and a dedicated flow-cell designed and built for housing the microcantilever. The response of this sensor was electronically and analytically characterized by using conductance signals. The analytical performance of the sensor was compared to that provided by the conventional quartz crystal microbalance (QCM), demonstrating advantages in terms of sensitivity, linear range of response and resolution. After the optimization of the method, it was validated for its use for direct determination of carbonate in soil samples. The method allowed the determination of carbonate in the 3–75 mg range, with a precision of 1.7%, expressed as relative standard deviation. It was applied to the analysis of different soil samples, obtaining results in agreement with those produced by the official method.     

测定DMMP的PMPS-QCM传感器的研究

研究了新型敏感材料PMPS对神经性毒剂模拟剂甲基膦酸二甲酯(DMMP)的响应特性.在石英晶体微天平(QCM)的电极上滴涂上PMPS溶液得到敏感膜,发现QCM当响应、恢复时间为30-60 s时,可以产生大约11.83 Hz/ppm(ppm i.e.×10-6)的频率响应,理论上LOD为0.25 ppm(ppm i.e.×10-6),并具有较好的重复性和选择性.该实验结果表明,与PVDF相比,PMPS是一种更适宜检测DMMP的敏感材料.     

Optical parameters of calix[4]arene films and their response to volatile organic vapors

The Langmuir-Blodgett (LB) technique was employed to produce thin LB films using an amphiphilic calix-4-resorcinarene onto different substrates such as quartz, gold coated glass and quartz crystals. The characteristics of the calix LB films are assessed by UV-visible, quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) measurements. UV-vis and QCM measurements indicated that this material deposited very well onto the solid substrates with a transfer ratio of >0.95. Using SPR data, the thickness and refractive index of this LB film are determined to be 1.14 nm/deposited layer and 1.6 respectively. The sensing application of calixarene LB films towards volatile organic vapors such as chloroform, benzene, toluene and ethanol vapors is studied by the SPR technique. The response of this LB film to saturated chloroform vapor is much larger than for the other vapors. The response is fast and fully recoverable. It can be proposed that this sensing material deposited onto gold coated glass substrates has a good sensitivity and selectivity for chloroform vapor. This material may also find potential applications in the development of room temperature organic vapor sensing devices.     

Solid-state potentiometric SO2 sensor combining NASICON with V2O5-doped TiO2 electrode

A compact tubular sensor based on NASICON (sodium super ionic conductor) and V₂O₅-doped TiO₂ sensing electrode was designed for the detection of SO₂. In order to reduce the size of the sensor, a thick-film of NASICON was formed on the outer surface of a small Al₂O₃ tube; furthermore, a thin layer of V₂O₅-doped TiO₂ with nanometer size was attached on the NASICON as a sensing electrode. This paper investigated the influence of V₂O₅ doping and sintering temperature on the characteristics of the sensor. The sensor attached with 5 wt% V₂O₅-doped TiO₂ sintered at 600 °C exhibited excellent sensing properties to 1–50 ppm SO₂ in air at 200–400 °C. The EMF value of the sensor was almost proportional to the logarithm of SO₂ concentration and the sensitivity (slope) was −78 mV/decade at 300 °C. It was also seen that the sensor showed a good selectivity to SO₂ against NO, NO₂, CH₄, CO, NH₃ and CO₂. Moreover, the sensor had speedy response kinetics to SO₂ too, the 90% response time to 50 ppm SO₂ was 10 s, and the recovery time was 35 s. On the basis of XPS analysis for the SO₂-adsorbed sensing electrode, a sensing mechanism involving the mixed potential at the sensing electrode was proposed.     

Utilizing a high fundamental frequency quartz crystal resonator as a biosensor in a digital microfluidic platform

We demonstrate the operation of a digital microfluidic lab-on-a-chip system utilizing Electro Wetting on Dielectrics (EWOD) as the actuation principle and a High Fundamental Frequency (HFF; 50?MHz) quartz crystal microbalance (QCM) resonator as a mass-sensitive sensor. In a first experiment we have tested the reversible formation of a phosphor-lipid monolayer of phospholipid vesicles out of an aqueous buffer suspension onto a bio-functionalized integrated QCM sensor. A binding of bio-molecules results in an altered mass load of the resonant sensor and a shift of the resonance frequency can be measured. In the second part of the experiment, the formation of a protein multilayer composed of the biomolecule streptavidin and biotinylated immunoglobulin G was monitored. Additionally, the macroscopic contact angle was optically measured in order to verify the bio-specific binding and to test the implications onto the balance of the surface tensions. Using these sample applications, we were able to demonstrate and to verify the feasibility of integrating a mass-sensitive QCM sensor into a digital microfluidic chip.     

Enhancing the sensitivity of ionic liquid sensors for methane detection with polyaniline template

Flammable gas sensors are essential in occupational health and safety to prevent fire or explosion in gas facilities and underground mining. Our early study demonstrated that ionic liquid (IL)/quartz crystal microbalance (QCM) gas sensors and sensor arrays were excellent for the detection of various organic vapors at both room temperature and elevated temperatures. In this paper, we developed a general method that significantly enhanced the sensitivity of the IL/QCM sensors for flammable gases detection by immobilizing IL on a conductive polymer polyaniline (PAn) template. Studies were performed to optimize the PAn oxidation states, thickness, and IL concentrations. Results showed that the sensitivity increased with increasing the PAn film thickness and the amount of IL immobilized within the PAn film. The sensitivity depended also on the oxidation state and doping state of PAn. With doped and partially oxidized PAn (emeraldine salt) the IL/QCM sensor showed the best performance. The current detection limit for methane was as low as about 115 ppm at room temperature. The sensitivity also depended on the structure of the IL used. Among the four ILs tested, two of them showed excellent sensitivities after being immobilized in the PAn film.     

A Micromachined Quartz Resonator Array for Biosensing Applications

An 8-pixel micromachined quartz crystal resonator array with a fundamental resonance frequency of 66 MHz has been designed, fabricated, and tested. A compact impedance-spectrum-analyzer electronic interface has been developed and combined with the quartz resonator array to form the biosensing system. The sensor array was calibrated using water–glycerol solutions, and the performance was found to be exactly as expected. Measurement of the crosstalk between the sensor pixels showed an isolation of $sim$ 30 dB. Selective functionalization of the pixels was achieved through the use of aqueous 3, 3 $^{prime}$-Dithiobis (sulfosuccinimidylpropionate) (DTSSP) molecules. The adsorption of avidin on DTSSP gave a frequency signal of 60 kHz in comparison to unfunctionalized pixels. The specific adsorption of avidin on functionalized pixels was confirmed through fluorescence microscopy. Comparing the performance of the micromachined quartz crystal microbalance (QCM) with a commercial 5-MHz device, we found that the micromachined QCM has a 4.25 times higher signal-to-noise ratio. Based on the measurement of the noise and using three times the frequency noise as the limit for the detection of avidin molecules, we expect to resolve a minimum of $sim$1/960 of a monolayer of avidin corresponding to an aerial mass density resolution of 0.7 $hbox{ng/cm}^{2}$ .$hfill$[2008-0196]      

Detection of heavy metal ions in aqueous solution by P(MBTVBC-co-VIM)-coated QCM sensor

A novel copolymer P(MBTVBC-co-VIM) was designed and successfully synthesized for the fabrication of copolymer-coated QCM sensors to detect the heavy metal ions in aqueous solution. The copolymer P(MBTVBC-co-VIM) contains many nitrogen (N) and sulfur (S) atoms in the side groups as electron donors, which can easily form complexes with heavy metal ions. The strong interaction between the S atom and Au electrode of quartz crystal further assures the stability of copolymer thin films on the quartz crystal surface in aqueous media. The QCM results indicated that the P(MBTVBC-co-VIM)-coated sensor exhibited high sensitivity, stability and selectivity for the detection of Cu²⁺ in aqueous solution. The lowest detection limit can reach 10 ppm Cu²⁺ in aqueous solution, which resulted in the frequency shift of 3.0 Hz (ΔF₃/3). The P(MBTVBC-co-VIM)-coated QCM sensors had porous surface morphologies as revealed by AFM investigation. Such porous structures enhanced the surface areas of the copolymer thin films, which increased the contacting probability of N and S atoms with heavy metal ions in solution and improved the detection sensitivity of the copolymer-coated QCM sensors.     

聚苯胺/TiO2修饰的QCM气敏传感器及湿度影响研究

用气敏传感器检测三甲胺在食品检验和环境监测等领域具有广泛意义,而湿度影响在这些实际应用中通常无法避免,如何补偿和校正湿度干扰是传感器设计和使用中的重要课题.考察了一种以聚苯胺/TiO2复合材料为敏感膜的QCM气敏传感器在干燥和不同湿度气氛中对三甲胺气体的响应特性,结果表明均呈现出良好的线性敏感性.发现了在湿度干扰下的传...     

Highly stable and sensitive humidity sensors based on quartz crystal microbalance coated with bacterial cellulose membrane

A novel highly stable and sensitive humidity sensor based on bacterial cellulose (BC) coated quartz crystal microbalance (QCM) has been successfully fabricated. The results showed that the sensors possessed good sensing characteristics by increasing more than two orders of magnitude with increasing relative humidity (RH) from 5 to 97%, and the Log(Δf) showed good linearity (20-97% RH). The sensitivity of sensors coated with BC membranes was four times higher than that of the corresponding cellulose membranes at 97% RH. In addition, the sensor sensitivity is greatly enhanced by increasing the coating load of the BC membranes with more absorption sites in the sensing membranes. Moreover, the experimental results prove that the resultant sensors exhibited a good reversible behavior and good long term stability. Herein, not only a novel and low-cost humidity sensor material was exploited, but also a new application area for BC nanofibrous membranes was opened up.