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Determination of surface ζ‐potential and isoelectric point of carbon surfaces using tracer particle suspensions 下载免费PDF全文
Joana M. Vasconcelos Federico Zen James A. Behan Paula E. Colavita 《Surface and interface analysis : SIA》2017,49(8):781-787
Carbon materials are widely used in a range of applications from biomaterials to sensing and electronics. Many of these applications rely on the ability to control carbon/water interfacial properties, in particular, surface charge density. This work reports a study of the electrokinetic properties of amorphous carbon thin films as a function of pH and surface chemistry. Surface ζ‐potential (SZP) and isoelectric point were determined using the tracer particle method. Initially, the use of sulfonated and amine‐terminated latex bead suspensions as tracer particles for the determination of SZP of reference polymer surfaces was validated. The tracer particle method was then applied to the determination of SZP and isoelectric point of macroscopic carbon surfaces with different surface chemistry. Highly graphitic and sp3‐rich hydrogenated carbon surfaces were found to display negative SZP, as expected for hydrophobic surfaces. The isoelectric point of the most highly graphitic surface was found to be pHiso = 3.7. Surface oxidation of these films resulted in a decrease of SZP at all pH values and in a downshift of pHiso to values lower than 1.5, consistently with the presence of surface acidic groups arising from oxidation. Results indicate that the specific choice of acid/base chemistry for the tracer particles does not significantly affect either SZP or pHiso determinations. These results show that the tracer particle method in combination with widely available latex beads as tracers can be applied for the determination of carbon SZP as a function of pH. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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磁粒子成像是基于功能和断层影像技术检测磁性纳米粒子空间分布的示踪方法, 具有正向的对比信号、 较低的组织背景、 无限的组织穿透深度、 非侵入性成像以及无电离辐射等优点, 是近年来一种很有前途的生物医学成像技术. 磁粒子成像信号是通过在无场点切换磁性纳米粒子的磁自旋矢量来产生的. 磁粒子成像的灵敏度和空间分辨率都高度依赖于作为磁粒子成像示踪剂的磁性纳米粒子本身的磁性能, 因此目前的研究主要集中在磁性纳米粒子的设计和合成上. 本文重点介绍了磁粒子成像示踪剂的最新研究进展, 总结了可作为磁粒子成像示踪剂的磁性纳米粒子的种类、 合成方法、 性能以及生物医学应用, 以期为磁粒子成像的未来研究提供参考. 相似文献
4.
Ranjan Maitra 《Journal of computational and graphical statistics》2013,22(1):132-142
Abstract Functional imaging of biologic parameters like in vivo tissue metabolism is made possible by Positron Emission Tomography (PET). Many techniques have been suggested for extracting such images from dynamic time-course sequences of reconstructed PET scans. Quantitating the precision of these estimates is important for drawing inferences on the biologic parameters. Analytic variance formulas are not immediate owing to the nonlinear methods used in extraction. The usual resampling approach is infeasible because each image reconstruction in PET is a computationally demanding solution to a high-dimensional linear inverse problem. We suggest an alternative simulation approach that approximates the distribution of reconstructed PET scans and performs a parametric bootstrap in the imaging domain. Results on a simplified model chosen to match the characteristics of PET reconstruction are very encouraging. Mixture analysis is used to estimate functional images; however, the suggested approach is general enough to extend to other techniques or imaging methods. 相似文献
5.
R. Otto P. Hecht H.-G. Könnecke H. Koch H. J. Naumann W. Winzer 《Isotopes in environmental and health studies》2013,49(12):425-429
This paper reviews ways in which radioactive tracer techniques can he used to improve the efficiency of a caprolactam production plant, Residence time spectra and material distributions in different parts of the plant were measured by application of sodium 24, bromine 82 and technetium 99m. The investigations led to improved cumeneoxidators and gave useful informations on the catalytic decomposition of the phenolic tar and the hydrogenation process of phenol. It could he shown that the construction of the lactam extractor must he varied and the results of the tracerexperiments made in the distillation unit contributed to a higher quality of the final product. 相似文献
6.
Nitrous oxide is a potential environmental hazard responsible for the green house effect and the destruction of the ozone layer in the lower stratosphere. Biological denitrification under anaerobic conditions in soils results in the formation of both N2O and N2, whereby highly nitrogen-fertilized agricultural soils contribute to a considerable extent of the N2O emission. Latest results in the literature indicate that nitrous oxide can also be formed as a byproduct of the microbial nitrification. This is of importance for soils in central Germany because of the non-existence of typical denitrification conditions in a semiaride climate. This study was conducted to measure the path of N2O formation in Haplic Phaeozen: using [15N] ammonium and [15N] nitrat and a GC-MS aided incubation system. The kinetic isotope method was used to evaluate the experimental data. The results are: - Under anaerobic conditions (~ 90% of the water holding capacity = WHC) N2O originates mainly from the nitrate pool by denitrification. - As expected, the N2O formation is low under aerobic conditions (~ 80% WHC) but the gas originates directly from the ammonium and not from the nitrate pool, probably as a byproduct of the nitrification process. 相似文献
7.
M. F. Abdel-Wahab 《Isotopes in environmental and health studies》2013,49(4):149-151
Separation of Black Mamba (Dendroaspis polylepis) venom into three fractions was achieved by the use of Sephadex G-100 filtration method. The first and highest peak of the three separated bands proved to be the lethally toxic. Labelling the venom with nascent131 I prior to fractionating facilitated the detection and the evaluation of three well resoluted fractions. Comparative separation of non-labelled venom was also carried out side by side with the labelled one to study the advantage of radioactivity on extinction measurements. 相似文献
8.
B. Johannsen 《Isotopes in environmental and health studies》2013,49(9):293-300
1. Einleitung 2. Tracerdarstellung 3. Geuinnung von Antiseren 4. Methoden zur Trennung von freier und antikörpergebundener Radioaktivität 5. Analysengang 6. Spezifität 7. Empfindlichkeit 8. Anwendungsbeispiele 9. Literatur 相似文献
9.
H. A. Das 《Isotopes in environmental and health studies》2013,49(5):241-244
The leaching of microconstituents from granular solid wastes is often studied by column experiments. The underlying assumption is that the flow is of the one-compartment or “backmix” type. The influence of small deviations from this ideal situation on the outcome of the leaching experiment depends slightly on the specific mass-transfer function of the trace involved. The deviation itself may be measured by a simple separate radiotracer experiment. 相似文献
10.
The theoretical concept of the computer program is based on the compartment theory for the 3-pool model using single pulse administration of the tracer. The code estimates the model parameters by means of the non-linear method of least squares fit under steady state conditions. Furthermore the parameters of the protein metabolism are calculated. The program works interactively and allows reading and modifying the experimental 15N tracer data via terminal and controlling the program. 相似文献