Chemical preparation of conductive elastomeric blends: Polypyrrole/EPDM. I. Oxidant particle-size effect

This work describes the preparation of polypyrrole and EPDM rubber blends, PPy/EPDM, by the sorption of pyrrole (vapor phase) in an EPDM matrix containing CuCl₂. We investigated the effect of the oxidant particle-size on the sorption and polymerization equilibrium, electrical conductivity, and mechanical properties of the blends. Independently of the CuCl₂ concentration and polymerization time, the polypyrrole weight fraction in the blend, X_ppy, increases when the oxidant particle-size in changed from 150–250 μm to smaller than 106 μm. For blends containing 50 phr of CuCl₂, obtained following 72 h of exposure to pyrrole, an increase in the Young's Modulus (from 2.2 ± 0.2 to 3.9 ± 0.6 MPa) and an increase in the electrical conductivity (from 10^?9 to 10^?7 S cm^?1) was observed when the oxidant particle-size was decreased. Infrared spectroscopy, thermogravimetric analysis, scanning differential calorimetry, and scanning electron microscopy were used in sample characterization. © 1994 John Wiley & Sons, Inc.     

Long-range magnetic ordering of quasi-one-dimensional S=1/2 Heisenberg antiferromagnet Sr2Cu(PO4)2

Magnetic properties of quasi-one-dimensional S=1/2 Heisenberg antiferromagnet Sr₂Cu(PO₄)₂ were investigated by temperature and field dependence of AC susceptibility down to 0.03 K. A sharp peak was observed at on the temperature dependence of AC susceptibility indicating long-range magnetic ordering. Taking into account the exchange constant, (Hamiltonian =J∑S_iS_i+1), the ratio k_BT_N/J is 0.06%. Sr₂Cu(PO₄)₂ is, therefore, one of the best one-dimensional Heisenberg antiferromagnet known so far.     

Flow system to gas capture from a nebulized solution

The use of aerosol produced in a nebulization chamber is proposed as an alternative to gas sample capture in flow systems. This paper describes the coupling of a sampling interface with a flow system, for in situ gas monitoring. Aspects related with the behavior of aerosol formation and gas solubilization in liquid drops are discussed. The method is applied to the determination of residual lime in acidic soils. Aliquots of 5.0 ml of 1.0 mol l⁻¹ HCl were mixed with soil samples (1 g). The CO₂ released from these samples was captured by a nebulized aerosol and determined conductivity. The analytical curve from 1.0×10⁻² to 5.0×10⁻² mol kg⁻¹ CaCO₃ was ploted applying the matrix matching approach. This proposition, allowed an increase in the sensibility with detection limit of 6.0×10⁻³ mol kg⁻¹. The precision was good (R.S.D. <3%) for an analytical frequency of 22 determinations per hour. A fair agreement, at 95% confidence level, was found between the results from the proposed method and certified values of the investigated samples.     

Methods for research on immune complement activation on modified sensor surfaces

We have developed a methodological system consisting of a new surface sensitive quartz crystal microbalance with dissipation monitoring (QCM-D) sensor surfaces together with different surface modification methods for the investigation of surface associated complement activation in human sera. The QCM-D surface, 10 mm in diameter, was modified by spin-coating of poly(urethane urea) (PUUR) and polystyrene (PS). Some sensor surfaces were also sputtered with titanium (Ti) or modified by hydrophobic self-assembled monolayer (SAM) of an 18-carbon alkane thiol with a ---CH₃ end group. The amount of surface deposited complement protein was investigated by incubation of the modified sensor surfaces in human sera, followed by incubation with antibodies directed against complement factor 3c (C3c). The amounts of bound anti-C3c were then used as an arbitrary measure of surface induced complement activation. The order of complement activation of the different surfaces, as judged by three separate measurements per surface modification, was PUUR>PS=SAM>Ti. The Ti surface had a similar low degree of anti-C3c binding as the negative controls (heat inactivated sera). The novel QCM-D methodology was found to be very simple, accurate, sensitive and well suited as a screening method for complement activation and protein adsorption on different materials. We also compared the sensitivity of QCM-D method with surface plasmon resonance (SPR) for the quantification of protein adsorption and complement activation on gold sensor surfaces. The QCM-D method was equally sensitive as the SPR for the detection of protein adsorption from a solution independently if low flow rate (5 μl/min) was used. A slight increase in sensitivity was found at higher flow rate (30 μl/min). However, we found it difficult to use the SPR method on the Ti, PS and PUUR surfaces due to decreased light penetration of the modified SPR sensor chip.     

水／AOT／正庚烷微乳体系中磺酸根水化作用的FT—IR研究

运用傅立叶变换红外光谱（FT－IR）对水／琥珀酸（乙基已基）磺酸钠（AOT）／正庚烷微乳体系中磺酸根的水化作用进行了研究．由于微乳体系中水分子与表面活性剂分子的相互作用，S＝O对称伸缩振动的红外吸收峰向低频方向移动．体系中的加水量W0（水与AOT的摩尔比）由0.5增大至25时，磺酸根对称伸缩振动的红外吸收峰由1051．39cm－1向低频移动至1046．15cm－1．同时，由于Na 的不对称作用，AOT分子中磺酸根反对称伸缩振动分裂成两个吸收峰，分别位于正215cm-1及1245cm－1附近，两个劈裂峰的距离及各自的峰面积均随体系中加水量的变化而变化，应用二阶导数、傅立叶退卷积及曲线拟会等分辨率增强技术可更清楚地反映出这个二重峰的变化情况．固体AOT分子中碳酸根反对称伸缩振动分裂的两个峰之间频率的差值约为42cm－1，形成微乳液以后，这两个峰的差值变小，W0为20时，这两个峰频率的差值逐渐减小到29cm-1，这些变化与磺酸根的水化程度直接相关     

Electrical Double Layer on Liquid Sn–Ga Alloy in Aqueous Solutions

Double-layer parameters of a liquid Sn–Ga electrode in aqueous electrolyte solutions are studied. It is shown that Sn in the alloy with Ga is a surface-active component and is forced out onto a surface layer of the electrode. The double-layer parameters of an Sn–Ga electrode (8 at. % Sn), which are measured in the experimentally accessible range of charges, differ radically from the parameters of Ga electrodes and are close to those of Sn electrode. Hence, an Sn–Ga electrode containing 8 at. % Sn simulates electrochemical properties of a liquid Sn electrode. The difference between reciprocal electronic capacitances of Hg and Sn and a corrected electrochemical work function of Sn are determined. It is shown that the chemisorption interaction of an Sn–Ga electrode with water molecules is virtually absent at charges more negative than –7 C/cm². A potential drop on uncharged Sn, which is associated with water chemisorption, is –20 mV. Thus, the hydrophilicity of Sn is slightly higher than that of Hg, Bi–Ga, Pb–Ga, and Tl–Ga and significantly lower than that of In–Ga, Cd–Ga, and Ga.     

超临界萃取装置的研制及其应用

超临界流体萃取是近的上来兴起的一种新的分离技术，报道了将超临界萃取原理与回流技术相结合研制的二氧化碳回流中低压超临界流体萃取设备，解决了关键实验手段，通过应用证明设备可靠，费用低廉，有实用价值。     

Quantitative volatilization of tin as mixed halides and its application in metal analysis

Proposed in this paper is an improved method for removal of tin as the matrix element by volatilization in an anhydrous medium as mixed halides of different composition. Any one of them boils at a lower temperature than SnBr₄. This ternary system enhances the eventual recombination of temporarily dissociated species to volatile ones, thus making the process quicker and more efficient. The presence of 2 mg of Pb(II) suffices to prevent Bi(III) from loss due to volatilization.     

Preparation and Superconductivity of a Series of Bi2CaSr2-XBaxCu2O8+δ

By means of the addition of Ba into the Bi-Ca-Sr-Cu-O 2122 system, a series of Bi₂CaSr_2-xBa_xCu₂O_8+δ (0 ≤ × ≤ 2) quinary metal oxides were prepared by the citrate route and by the conventional powder reaction method. The samples prepared by the former method have better properties than the latter. It was found that 5 was not equal to zero for all of them and that it increased with decreasing Tc. Two phases were indentified in the oxides containing all five metal elements. One is the Bi-Ca-Sr-Cu-O 2122 phase, the other is a new insulating phase which probably contains Bi-Ca-Ba-Cu-O with undetermined stoichiometry. Superconductivity was found in those samples for which × ≤ 1.50 with their Tc onsets between 93–78 K by resistivity measurements. Superconductivity decreased monotonically with increasing x. However, residual resistance was found in those samples for which 1.00 ≤ × ≤ 1.50, The Meissner effect appears in the samples where × ≤ 1.00 with Tc onsets between 88–80 K. For x = 1.75 and 2.00, the samples were semiconductors with resistivities of 6.66 × 10² and 6.96 × 10³ Ω cm at 290 K, and activation energies of 0.109, and 0.298 eV, respectively.     

Screen-printed multienzyme arrays for use in amperometric batch and flow systems

Screen-printing technology for electrode fabrication enables construction of amperometric devices suitable for combination of several enzyme electrodes. To develop a biosensor array for characterisation of wastewaters, tyrosinase and horseradish peroxidase (HRP) or cholinesterase-modified electrodes were combined on the same array. The behaviour of the tyrosinase-modified electrode in the presence of hydrogen peroxide (required co-substrate for the HRP-modified electrode) and acetylthiocholine chloride (required co-substrate for cholinesterase) was studied. Performance of bi-enzyme biosensor arrays in the batch mode and in the flow-injection system are discussed.