压电晶体传感器的研究进展

本文简要介绍了压电晶体传感器的基本原理,以及基于质量、粘度、电导率变化的溶液分析法。重点介绍了电化学石英晶体微天平（EQCM）、压电生物传感器;对具有很大发展潜力和重要应用价值的串联式压电传感器（SPQC）、串联式表面声波电导传感器（SAW）、液隔电极式压电传感器（ESPS）等也作了简要说明。     

频移滴定的理论与应用

压电传感元件的特点是检测灵敏度高,但到80年代才成功用于液相,本文讨论压电晶振用于溶液中微量分析——频移滴定的理论及其在酸碱、沉淀、络合和氧化还原各类滴定中的应用,所提出的新型微量分析体系与经典的电导滴定等相比,具有优点.     

基于压电陶瓷的A型分子筛膜合成与吸附性能

无铅压电陶瓷0.8Na0.5Bi0.5TiO3-0.2K0.5Bi0.5TiO3表面采用化学改性预涂晶种作为基底,分别以微乳和澄清溶液法在基底上水热晶化合成了A型分子筛膜。通过XRD、SEM和FTIR对晶种及分子筛膜进行了表征,通过压电谐振法测量甲烷吸附性能。结果表明:微乳和澄清溶液法均合成单一A型分子筛相,1次合成分子筛膜的时间分别为6、9h,通过不同镀膜次数生成A型分子筛膜的形貌、膜厚不同。经A型分子筛膜修饰压电振子后,其对甲烷气体的灵敏度可分别达到59Hz/1%CH4、68Hz/1%CH4。     

酶催化压电-电导频移法测定血清中甘油三酯

根据甘油三酯天脂肪酶作用下水解和压电传感器能够响应溶液电导率的性质,建立了酶催化压电－电导频移法测定血清中甘油三酯的新方法。甘油三酯的浓度在７．４×１０＾－６－４．９×１０＾－３ｍｏｌ／Ｌ范围内与传感器的频移值具有线性关系,线性回归方程ΔＦ＝－４４．３－１３２０ｃ（ｍｍｏｌ／Ｌ）,相关系数ｒ＝０．９９８９。     

电化学石英晶体微天平研究普鲁士蓝修饰电极

石英晶体徽天平(Quartz Crystal Microbalance,简称QCM)是一种非常灵敏的质量传感器,其检测能力可达ng级。QCM在化学中的早期应用是检测大气中的徽量成分,目前仍较活跃。由于石英压电晶体浸入溶液后在晶体/溶液界面存在较大的能量损失而不能够稳定振荡,致使QCM的应用较长时间局限于气相。八十年代初石英压电晶体在液相中的振荡终获成功,开辟了QCM应用的一个全新领域。液相中振荡成功后,QCM很快应用于电化学研究。目前已发展成为一种全新的电化学传感器——电化学石英晶体微天平(EQCM),并已用于金属电沉积、电化学腐蚀、电分析等方面的研究。     

光声量热法测定辅酶B12的光解量子产率

时间可分辨的光声最热法（Time－resolvedphotoacousticcalorimetry；简称PAC）是研究脉冲激光诱发的快速光化学和光生物化学反应过程动力学和热力学信息的一种有效方法[1－5]。本文采用压电陶瓷圆管同时作为样品油和换能器组成的PAC探测系统[6]，以波长λ＝355nm的脉冲激光（脉冲宽度8ns，脉冲重复频率10Hz）为光源激发辅酶B12甲醇溶液；研究其解量子产率，获得了满意的结果．1实验被测溶液注入两端用石英玻璃封口的压电陶瓷圆管内腔，激光束透过石英窗照射溶液（如图］所示）为标定被测样品的非辐射放热量，利用能在极短的时间内（＜l…     

基于压电陶瓷的A型分子筛膜合成与吸附性能

无铅压电陶瓷0.8Na_0.5Bi_0.5TiO₃-0.2K_0.5Bi_0.5TiO₃表面采用化学改性预涂晶种作为基底,分别以微乳和澄清溶液法在基底上水热晶化合成了A型分子筛膜.通过XRD、SEM和FTIR对晶种及分子筛膜进行了表征,通过压电谐振法测量甲烷吸附性能.结果表明:微乳和澄清溶液法均合成单一A型分子筛相,1次合成分子筛膜的时间分别为6、9 h,通过不同镀膜次数生成A型分子筛膜的形貌、膜厚不同.经A型分子筛膜修饰压电振子后,其对甲烷气体的灵敏度可分别达到59 Hz/1%CH₄、68 Hz/1%CH₄.     

压电石英晶体在电解质水溶液中的振荡性能研究(Ⅱ)——频率、频移特性

根据两面电极浸入液体中的压电晶体等效电路模型和Pierce振荡器振荡方程的解,得到晶体在电解质溶液中的振荡频率(F_1)与溶液电导率(x)的关系式:F_1=(1/2π)(1/C_1+1/C_2)(1/X_e)[(R_e~2+X_e~2)x~2+2R_ex+1]。以自行设计的Pierce晶体振荡器。研究了晶体和主振电路参数、输入电压及检测池外壳屏蔽接地对AT切9MHz石英晶体在KCl、Na_2SO_4水溶液中的频率、相对于纯水频移随溶液电导率变化的影响规律,结果与上式相符。     

聚合物压电智能材料研究新进展

聚合物压电材料已经有近 4 0的历史 ,近年来由于被用于智能材料而引起更多研究工作者的关注。本文介绍了聚合物产生压电性能的机制、分类 ,判断、评价聚合物压电性能的基本参数和指标 ,分析了不同形态聚合物压电材料的结构要求及微观机理 ,介绍了材料取向、极化机制与方法。讨论了其主要表征和基本模拟方法 ,并对压电聚合物材料的优良性能、应用与发展前景作出了简要说明     

水合高氯酸盐+有机溶剂体系中氢氧化物电沉积的EQCM研究

采用电化学石英晶体微天平(EQCM)定量研究了含水合高氯酸盐的丙酮、DMF、DMSO、C2H5OH或CH3OH有机溶液中LiOH(或NaOH)的电沉积过程. 这种电沉积现象可归因于有机溶液中的溶解氧和共存水在负电位下电还原产生OH−, OH−与溶液中金属阳离子结合生成在非水溶剂中溶解度很小的氢氧化物而沉淀在电极表面, 从而引起压电参数的响应, 而使用四丁基溴化铵为支持电解质时这种现象不明显. 讨论了不同支持电解质、不同溶剂、支持电解质浓度和外加水浓度对氢氧化物电沉积的影响, 估算了氢氧化物沉淀的电极收集效率.     

STUDIES ON TEXTILE DETERGENCY AT LOW TEMPERATURE

Detergent efficiency of nonionic surfactant solutions with and without electrolyte as a function of temperature has been determined. In these experiments hexadecane was chosen as a model oily soil and polyester/cotton fabrics as solid substrate. It was found that the evolution of detergent efficiency with temperature in systems containing electrolyte followed the same trends as those of systems without electrolyte: As the temperature increases detergent efficiency also increases and an optimum is reached, then a pronounced decrease is observed. However there is a shift in the temperature at which the optimum is obtained toward lower temperatures as electrolyte concentration increases. This shift has been attributed to the effect of salting-out electrolytes on the HLB-temperature of ternary water/nonionic surfactant/oil systems.     

Ionic strength-dependent pK shift in the helix-coil transition of grafted poly(L-glutamic acid) layers analyzed by electrokinetic and ellipsometric measurements

Surface-bound layers of poly(L-glutamic acid) prepared by a recently described "grafting-from" method were analyzed with respect to electrical charging and structural alterations upon variation of pH and concentration of the background electrolyte in aqueous solutions. The microslit electrokinetic setup (MES) was utilized for the combined determination of zeta potential and surface conductivity on the basis of streaming potential and streaming current measurements at polypeptide layers in contact with aqueous electrolyte solutions of varied composition. In situ ellipsometry was applied at similar samples immersed in identical aqueous solutions to investigate the influence of the solution pH on the structure of the polypeptide layers. Zeta potential and Dukhin number versus pH plots revealed the dissociation behavior of the surface-bound polypeptides indicating a significant shift of the pK of their acidic side chains correlating with the concentration of the background electrolyte potassium chloride and the related variation of the Debye screening length. Surface conductivity data pointed at a more expanded structure of the polypeptide layer in the fully dissociated state as an increased ion conductance in this part of the interface was determined. The occurrence of a strong increase of the thickness and a corresponding decrease of the refractive index for the coil state of the layer strongly supports the findings of the electrokinetic measurements. This fully reversible "switching" of the layer structure was attributed to helix-coil transitions within the grafted polypeptides induced by the dissociation of carboxylic acid functions of the polypeptide side chains. The shift of the "switching pH" of the surface-bound poly(L-glutamic acid) layers at varied concentrations of the background electrolyte was interpreted as a result of the pK shift of the carboxylic acid groups of the polypeptide side chains. The observed patterns prove that the electrostatic interactions causing this shift occur within but not between the grafted chains.     

High ionic strength electrokinetics of melamine-formaldehyde latex

The electrokinetic potential of melamine-formaldehyde latex at high ionic strengths was measured by means of two different instruments. The present study confirms that the zeta potentials in 1 M 1-1 electrolyte solutions can be as high as +/-20 mV. The IEP of latex at low ionic strengths was at pH 11. The increase in the electrolyte concentration induced a shift in the IEP to low pH for all studied salts, and this indicates specific adsorption of the anions. The magnitude of the shift depends chiefly on the nature of the anion and increases in the series Cl < NO(3) = Br < I, and the nature of the cation (Li, Na, K, Cs) plays a rather insignificant role.     

Transient natural convection induced by electrodeposition of Li+ ions onto a lithium metal vertical cathode in propylene carbonate

Transient natural convection caused by Li⁺ electrodeposition at constant current along a vertical Li metal cathode immersed in a 0.5 M LiClO₄–PC (propylene carbonate) electrolyte was compared with that by Cu²⁺ ion electrodeposition in aqueous CuSO₄ solution. The concentration profile of the Li⁺ ions was measured in situ by holographic interferometry. The interference fringes start to shift with time at a higher current density. The concentration boundary layer thickness for Li⁺ ions was successfully determined. With the progress of electrodeposition, the density difference between the electrolyte at the cathode surface and the bulk electrolyte increased to induce upward natural convection of the electrolyte. The electrolyte velocity was measured by monitoring the movement of tracer particles. The measured transient behavior of the ionic mass and momentum transfer rates normalized with respect to the steady-state value was numerically analyzed. Transient natural convection along a vertical cathode due to Li metal electrodeposition can be reasonably explained by boundary layer theory, similar to the case of Cu electrodeposition in aqueous CuSO₄ solution.     

Quantification of the effect of 4-tert-butylpyridine addition to I-/I3- redox electrolytes in dye-sensitized nanostructured TiO2 solar cells

Addition of 4-tert-butylpyridine (4TBP) to redox electrolytes used in dye-sensitized TiO2 solar cells has a large effect on their performance. In an electrolyte containing 0.7 M LiI and 0.05 M I2 in 3-methoxypropionitrile, addition of 0.5 M 4TBP gave an increase of the open-circuit potential of 260 mV. Using charge extraction and electron lifetime measurements, this increases could be attributed to a shift of the TiO2 band edge toward negative potentials (responsible for 60% of the voltage increase) and to an increase of the electron lifetime (40%). At a lower 4TBP concentration the shift of the band edge was similar, but the effect on the electron lifetime was less pronounced. The working mechanism of 4TBP can be summarized as follows: (1) 4TBP affects the surface charge of TiO2 by decreasing the amount of adsorbed protons and/or Li+ ions. (2) It decreases the recombination of electrons in TiO2 with triiodide in the electrolyte by preventing triiodide access to the TiO2 surface and/or by complexation with iodine in the electrolyte.     

Frequency properties of a piezoelectric quartz crystal in solutions and application to total salt determination

For an integrated circuit oscillator, the slope of the linear portion of the frequency shift/electrolyte concentration plot for a AT-cut quartz piezoelectric crystal immersed in a solution is dependent on the circuit capacitance, decreasing from positive to negative values with increasing capacitance. The slope does not vary significantly with the kind of salt. A method based on the frequency measurement is suggested for the rapid determination of the total salt content of natural waters.     

Particle Nucleation and Growth in the Emulsion Polymerization of Styrene: Effect of Monomer/Water Ratio and Electrolyte Concentration

This work is an extension of previous research results reported by our team (Colloid and Polymer Science 2013, 291: 2385-2398), where large scale and high solid content latexes of poly(n-butyl acrylate) were obtained with the particle coagulation method induced by the electrolyte. However, how to prepare controlled particle size distribution polymer latex has not been studied. Thus, in this study, the effect of the monomer/water ratios and electrolyte concentrations on particle formation and growth methods were studied by following the tracks of the evolutions of particle size, number and distribution as a function of reaction time or conversion. Experimental results showed that the length of time that particle nucleation occurred increased with increasing monomer charged for the systems without electrolyte. A point worthy of attention here is that homogeneous nucleation may occur at high monomer concentrations (30/70, 40/60). However, electrolyte added could be made the nucleation mechanism shift from micellar/homogeneous nucleation to micelle /coagulation nucleation. As a result, the final particle size distribution can be controlled by adding an appropriate electrolyte to regulate the nucleation mechanism. Spherical and uniformly sized particles could be obtained when electrolyte concentration is between 0.2 wt% and 0.4 wt% for water at the high monomer/water ratio (40/60). The effects of electrolyte concentration on nucleation mechanism mainly were expressed by decreasing the solubility of the monomer and interparticle potential, and then preventing homogeneous nucleation and enhancing particle coagulation.     

Titrations with piezoelectric monitoring : Part 1. Fundamental theory and titration of acids and bases

The use of a piezoelectric quartz crystal detector is proposed for monitoring the course of a titration reaction by observation of the frequency shift of the oscillating crystal. Satisfactory titrations can often be obtained using the acid-base technique, which is much more sensitive than the classical conductimetric titration and oscillometric titrration, with a lowest titratable concentration that is much lower but which can still be applied in the presence of a large amount of unreacting electrolyte.     

Electrochemistry Investigation on the Graphene/Electrolyte Interface

In this study, the graphene/electrolyte interface was investigated in detail by the electrochemical method. The total interface capacitance was calculated from the electrochemical impedance spectroscopy (EIS) results, and its responses to different concentrations and pHs were also investigated. The minimum point of the capacitance was found to shift to right (vs. Ag/AgCl) as the concentration increased, and to left with increasing pH. As a comparison, gold/electrolyte interface was investigated in the same way, but didn’t show the similar behavior. To further explore the interface capacitance, proper models were proposed to fit the EIS results. Two constant‐phase elements (CPE) were used in the graphene‐electrolyte interface model to represent the double‐layer capacitance (CPE_dl) and the quantum capacitance (CPE_q), respectively. The CPE_q exhibited its sensitivity to concentration and pH, while CPE_dl did not. This study gives a new aspect to detect concentration and pH, and may provide a reference for the graphene‐based supercapacitor research.     

The effect of pH,chloride ion and background electrolyte concentration on the SERS of acidified pyridine solutions

Surface enhanced Raman spectra of pyridine are reported as a function of pH, halide concentration and background electrolyte concentration. The assignments of pyridinium bands are given in the range 100–4000 cm^?1, and the low frequency band around 235 cm^?1 is discussed. It is found that to obtain a pyridinium spectrum, the presence of halide is necessary. Background electrolyte concentration does not affect the intensity of the pyridine spectrum but greatly affects that of pyridinium. On the basis of the dependence of the intensity of pyridinium on chloride and background electrolyte concentrations, pyridinium is considered not be directly adsorbed on the electrode surface but rather located in the diffuse double layer and associated with specifically adsorbed chloride to form an ion pair.The in-situ measurement of pH and the SERS of pyridine and pyridinium during a pH titration reveal a linear relation between surface pH and bulk pH. Specifically adsorbed chloride causes a decrease in the surface pH. This decrease is explained by a shift of the electrostatic potential at the outer Helmholtz plane caused by specific adsorption of chloride.