Surface imprinted macroporous film for high performance protein recognition in combination with quartz crystal microbalance

Macroporous protein imprinted films (porous-MIP) have been fabricated on the surface of quartz crystal microbalance (QCM) using methyl methacrylate (MMA) as main monomer and trimethylolpropane trimethacrylate (TRIM) as a cross-linker. Macropores were generated by employing calcium carbonate nanoparticles as porogen. The imprinted special surface area and the quantity of the imprinted sites were increased by the formation of macropores on the films. Since the macropores were interconnected in structure, the mass transport and accessibility of protein to the active sites through the material were not affected. In comparison with the nonporous imprinted (nonporous-MIP) films, the porous-MIP films exhibited better affinity and selectivity to template, the binding capacity and mass sensitivity of the biosensor were enhanced. The rigid skeleton structure made the films durable in the recycled tests. The strategy proposed here is generally applicable for constructing high performance biosensor devices.     

Plastic antibodies as chemical sensor material for atrazine detection

Self-organization of monomers around template molecules, in bulk MIP generation, leads to selective molecular imprints with high sensitivity. Employing the host–guest chemistry, novel artificial receptors were fabricated via in situ MIP synthesis directly on gold electrodes of piezoelectric transducers (quartz crystal microbalance, QCM). The resultant label-free and robust biomimetic sensing material shows reversible as well as selective sensor responses for chlorotriazines moieties with minor structural differences. A detection limit of 20 ppb for atrazine was attained while showing selectivity up to 9 times higher than its metabolites des-ethyl-atrazine (DEA), des-isopropyl-atrazine (DIA), des-ethyl-des-isopropyl-atrazine (DEDIA) and structural analogues like simazine (SIM) and propazine (PRO). Furthermore, imprinted nanoparticles give linear characteristics over the wide range and show no saturation effects in comparison to bulk materials.     

基于纳米沸石分子筛薄膜的新型气体传感器

研究了一种基于纳米沸石分子筛Ag+ZSM 5的新型气体传感器。该传感器利用纳米沸石分子筛Ag+ZSM 5对丙酮分子有较好的选择性和石英晶体振荡器对微小质量改变的高度灵敏性的特性设计并制作了对丙酮敏感的气体传感器。研究结果发现,采用ZSM 5型分子筛并用Ag+对该分子筛进行修饰可以提高对丙酮气体的响应,而对乙醇的响应较小。对不同浓度的丙酮气体的测试表明:在较低的丙酮气体浓度(0.67μmol/L)下,传感器表现出良好的响应,检测灵敏度较高,可达到44.8Hz/(μmol·L-1)。同时,该传感器具有良好的可逆性、重复性。     

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.     

A piezoelectric micro-cantilever bio-sensor using the mass-micro-balancing technique with self-excitation

A biosensor was developed for using in a Lab-On-a-Chip (LOC). The sensor detects the change in the resonance frequency of a micro-cantilever with a piezoelectric film. This is the mass micro-balancing technique, which has been successfully used for detecting bio-materials in the quartz crystal microbalance (QCM). The PZT film, a piezoelectric film, is designed to act as both sensor and actuator. The geometry of the micro cantilever is optimized to maximize the sensitivity and minimize the environmental effects such as viscous damping and added mass effect in liquid. The fabricated sensor is composed of a 100 μm long, 30 μm wide, and 5 μm thick cantilever with a 2.5 μm thick piezoelectric (PZT) layer on it. The ratio of thickness to length of the micro cantilever is very high compared to others in micro cantilever-based studies. This high aspect ratio is the key to maximize the sensitivity and minimize the environmental effects. The fabricated micro sensor was tested by detecting the mussel gluing protein, the insulin-anti insulin binding protein and the poly T-sequence DNA.     

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。     

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.     

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.     

Micromachined Acoustic Resonant Mass Sensor

This paper describes a highly sensitive, film bulk acoustic resonator (FBAR) mass sensor (built on a micromachined silicon-nitride diaphragm with a piezoelectric thin film and Al electrodes) that can operate in vapor and liquid. The sensitivity of the device to mass change on its surface has been investigated by having various thicknesses of silicon-nitride support layer and also of Al layer. The sensor is measured to have a mass sensitivity of 726 cm$^2$/g, which is about 50 times that of a typical quartz crystal microbalance (QCM). In vapor, the sensor (operating at around 1 GHz and having a relatively high quality (Q) factor of 200–300) shows a minimum detectable frequency shift of about 400 Hz, which corresponds to a mass change of$10^-9$g/cm$^2$on the sensor surface, comparable with that detectable by a QCM. In liquid, though the Q usually drops more than an order of magnitude, we obtain a Q of 40 at 2 GHz by using a second harmonic resonance of the resonator. And with the Q, a minimum 5 ppm resonant frequency shift can be detected, which corresponds to$10^- 8$g/cm$^2$change on the sensor surface.hfillhbox[1374]     

Molecularly imprinted ligand-exchange recognition assay of DNA by SPR system using guanosine and guanine recognition sites of DNA

Molecular imprinting polymer (MIP) as a recognition element for sensors are increasingly of interest and MIP-SPR have started to appear in the literature. In this study, we have proposed a novel surface imprinting method for DNA recognition and determination by methacryl-amidohistidine-platinum(II) [MAH-Pt(II)] as a new metal-chelating monomer via metal coordination–chelation interactions and guanosine/guanine templates of DNA. The study includes the measurement of binding interaction of molecular imprinted surface plasmon resonance (SPR) sensor via ligand interaction and recognition selectivity studies of guanosine and guanine imprinted polymers with respect to guanine and dsDNA. Adsorption isotherms of adenosine, guanosine, guanine, adenine, ssDNA and dsDNA were plotted and affinity constants for guanosine and guanine imprinted films were also calculated.     

硬脂酸复合薄膜光波导传感器检测苯乙烯

利用旋转甩涂法将亚甲基蓝(MB)掺杂的硬脂酸复合薄膜固定在钾离子(K+)交换玻璃光波导表面,研制了MB-硬脂酸复合薄膜/K+交换玻璃光波导传感器,并对挥发性有机物蒸气进行检测。实验结果表明,在室温下该传感器对低浓度的苯乙烯蒸气具有较好的重复性和选择性响应,能够检测到1×10-7(体积分数)的苯乙烯蒸气,其响应和恢复时间分别为12s和28s。该传感器具有灵敏度高、响应-恢复速度快、可逆性好、成本低、容易制作等特点。     

Nanolayer treatment to realize suitable configuration for electrochemical allopurinol sensor based on molecular imprinting recognition sites on multiwall carbon nanotube surface

In this work, nanolayer MIP (molecularly imprinted polymer) is used to achieve suitable conformation for catalyzing AP (allopurinol) redox reaction. Also, a sensitive electrochemical sensor was fabricated for AP based on MIP immobilized on multiwall carbon nanotube (MWCNT) surface. Thin film of MIP immobilized on MWCNT surface (MIPCNT) with specific recognition sites for AP was cast on glassy carbon electrode (GCE). The morphology and features of the film were characterized by field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometric measurements (I–t) in detail. The near equilibrium time to adsorb AP on the surface of electrode is about 9 min. The modified electrode was used to detect the concentration of AP with a linear range and detection limit (S/N = 3) of 0.01–1.0 μM and 6.88 nM, respectively. The MIPCNT film displayed an excellent selectivity toward AP. Finally, the modified electrode was successfully applied to determine AP in the human serum sample and two brand tablets.     

硬脂酸复合薄膜光波导元件的气敏性研究

利用旋转-甩涂法将聚乙烯吡咯烷酮(PVP)-硬脂酸复合薄膜固定在钾离子(K+)交换玻璃光波导表面,研制了PVP-硬脂酸复合薄膜/K+交换玻璃光波导元件,用于对挥发性有机物蒸汽进行检测。实验结果表明,在室温下该元件对低浓度的二甲苯蒸汽仍有较好的重复性和选择性响应,能够检测到1×10-6(体积分数)的二甲苯,其响应和恢复时间分别为9 s和35 s,相对标准偏差为±4.17%。该元件具有灵敏度高、响应-恢复速度快、可逆性好、成本低、容易制作等特点。     

The quartz crystal microbalance: mass sensitivity, viscoelasticity and acoustic amplification

Quartz crystal resonators (QCR) respond to surface mass and material properties of a film coated on their surface. The acoustic load acting at the surface of the resonator is a more general parameter to describe this dependence. It can be represented by a mass factor and an acoustic factor. The quotient of resistance increase and frequency shift can be used for the determination of the acoustic factor, if the loss tangent of the coating is known. Viscoelastic properties of sensitive coatings can enhance the mass sensitivity of quartz crystal microbalance (QCM) sensors. Acoustic factor and acoustic amplification effective during chemical sensing are not the same.

We further suggest a sensor concept, which is based on a bilayer arrangement. Acoustic amplification with a viscoelastic film and chemical sensitivity is separated. With a proper selection of materials, the first layer realizes acoustic amplification while the (chemical) sensitive layer acts as a pure mass detector. Major sensor design parameters are the shear modulus and the thickness of the first layer; major challenge is the preparation of a homogeneous and uniform first film.     

沸石分子筛修饰的QCM类神经毒气传感器

研究了Cu2 -Beta型纳米分子筛对类神经毒剂DMMP有机气体的敏感特性,并结合高灵敏的石英谐振微天平(QCM)研制了DMMP气体的传感器.研究结果表明,选择Cu2 -Beta纳米分子筛作为敏感膜对DMMP气体的检测灵敏度大大提高,达到14.481 1 Hz/lg(C/ppm).在0.2 ppm DMMP气体浓度下,传感器的响应时间和恢复时间分别为40 s和100 s,响应达到103Hz.同时经过高温和水汽吹扫脱附处理,该传感器表现了较好的重复性.     

Multiple conducting polymer microwire sensors

In this work, conducting polymer microwires of three commonly used conducting polymers were fabricated simultaneously on a common substrate using an intermediate-layer lithography (ILL) method. The three conducting polymers under consideration were polypyrrole (PPy), sulphonated polyaniline (SPANI) and poly(3,4-ethylenedioxythiophen)-poly(4-styrenesulphonate) (PEDOT-PSS). The fabricated microwires were implemented as sensing elements in detecting humidity and two organic vapors (i.e., methanol and acetone). The sensitivity of a single PPy microwire was compared with a rectangular PPy film after both were exposed to 45–85% humidity. The microwire sensor, due to its higher surface-to-volume ratio, was found to be more sensitive than the film sensor at low levels of humidity (between 45 and 58%). Beyond 58% humidity, the responses of the film and microwire sensors were similar. Three different sets of conducting polymer microwires (of PPy, SPANI and PEDOT) were then fabricated and employed as sensors to detect methanol, acetone and their mixtures. These microwires exhibited wave-like responses when they were exposed to these targets. The PPy and PEDOT microwires showed higher sensitivities in detecting methanol and acetone, respectively. The SPANI microwires exhibited similar responses in detecting methanol and acetone. The results demonstrate that microwire sensors were more effective than film sensors in detecting little quantities of target molecules. A sensor platform which integrates multiple microwire detectors is promising to detect multiple targets, and it also provides more information in detecting and distinguishing targets.     

烟酸分子印迹聚邻氨基酚敏感膜传感器的研制

研制了电化学聚合制备烟酸分子印迹聚邻氨基酚敏感膜传感器,并对分子印迹膜的结构和性能进行了探讨与研究.在弱酸性条件下,以邻氨基酚为单体,烟酸为模板分子,用循环伏安法电聚合成膜制备传感器.该传感器对烟酸具有良好选择性和敏感度,用恒电位计时安培法,烟酸浓度在2.0～5.0 mmol/L范围内与电流增量成线性关系,加标回收率在92%～104%之间.     

QCM 气体传感器的优化设计及应用研究

本文主要介绍了一种新型的石英谐振气体传感器 QCM(Quartz Crystal Microbalance) .它具有灵敏度高、稳定性好、抗干扰能力强等特点 ,可用于多种领域 ,本文主要根据计算化学方法 ,研究其对呼吸气体的响应特性 .此外 ,采用电化学方法制备传感器敏感膜 ,设计了相应的测量系统 .从实验结果可看出这一传感器对呼吸气体的响应结果是令人满意的 ,具有实际应用前景     

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.