Three novel electropolymerizable thiophene-based ionic liquids (ILs) were synthesized and characterized as potential candidates for developing selective extraction media for chemical analysis. ...Electropolymerization of the bis(trifluoromethyl)sulfonylimide (NTf2-) analogs successfully produced uniform polymeric thin-films on macro- and microelectrode substrates from both vinyl and methylimidazolium IL monomer derivatives. The resultant conducting polymer IL (CPIL) films were characterized by electrochemical methods and found to exhibit attractive behavior towards anionic species while simultaneously providing an exclusion barrier toward cationic species. Thermogravimetric analysis of the thiophene-based IL monomers established a high thermal stability, particularly for the methylimidazolium IL, which was stable until temperatures above 350 °C. Subsequently, the methylimidazolium IL was polymerized on 125 μm platinum wires and utilized for the first time as a sorbent coating for headspace solid-phase microextraction (HS-SPME). The sorbent coating was easily prepared in a reproducible manner, provided high thermal stability, and allowed for the gas chromatographic analysis of polar analytes. The normalized response of the polythioph-C6MImNTf2-based sorbent coating exhibited higher extraction efficiency compared to an 85 μm polyacrylate fiber and excellent fiber-to-fiber reproducibility. Therefore, the electropolymerizable thiophene-based ILs were found to be viable new materials for the preparation of sorbent coatings for HS-SPME.
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•Synthesis, characterization, and electropolymerization of thiophene-based ionic liquids on electrode surfaces.•Application of conductive polymer ionic liquids for electroanalysis and solid-phase microextraction.•Selective extraction of polar analytes by solid-phase microextraction.
Heat shock proteins (HSPs) are well known for their ability to "protect" the structure and function of native macromolecules, particularly as they traffic across membranes. Considering the role of ...key mitochondrial proteins in apoptosis and the known antiapoptotic effects of HSP27 and HSP72, we postulated that HSP60, primarily a mitochondrial protein, also exerts an antiapoptotic effect. Methods and Results- To test this hypothesis, we used an antisense phosphorothioate oligonucleotide to effect a 50% reduction in the levels of HSP60 in cardiac myocytes, a cell type that has abundant mitochondria. The induced decrease in HSP60 precipitated apoptosis, as manifested by the release of cytochrome c, activation of caspase 3, and induction of DNA fragmentation. Antisense treatment was associated with an increase in bax and a decrease in bcl-2 secondary to increased synthesis of bax and degradation of bcl-2. A control oligonucleotide had no effect on these measurements. We further demonstrated that cytosolic HSP60 forms a macromolecular complex with bax and bak in vitro suggesting that complex formation with HSP60 may block the ability of bax and bak to effect apoptosis in vivo. Lastly, we show that as cytosolic (nonmitochondrial) HSP60 decreases, a small unbound fraction of bax appears and that the amount of bax associated with the mitochondria and cell membranes increases.
These results support a key antiapoptotic role for cytosolic HSP60. To our knowledge, this is the first report suggesting that interactions of HSP60 with bax and/or bak regulate apoptosis.
A modified electrode sensor for the detection of thiols is described. The sensor was constructed by incorporation of the coenzyme pyrroloquinoline quinone (PQQ) into a polypyrrole (PPy) film on a ...glassy carbon electrode substrate by the electropolymerization of pyrrole in the presence of PQQ. The electrochemical properties of entrapped PQQ in the PPy film were influenced by the applied potential during electropolymerization and by film thickness, both of which were optimized to yield a stable and reproducible response for entrapped PQQ. The PQQ/PPy sensor was utilized for the amperometric detection of cysteine, homocysteine, penicillamine, N-acetylcysteine, and glutathione. The response for each thiol in pH 8.42 borate buffer was found to be linear with detection limits (S/N = 3) ranging from 13.2 μM for glutathione to 63.7 nM for cysteine with sensitivities of 0.023 nA/μM and 4.71 nA/μM, respectively. The response and detection limits were found to be sensitive to the nature of the thiol and the solution pH. Furthermore, in the presence of dopamine, ascorbic acid, or uric acid, the pH-dependent redox potential of the PQQ catalyst allows tuning of the detection potential to enhance the selectivity for thiols over these potential electroactive interferences.
Precision interferometry is the leading method for extremely sensitive measurements in gravitational wave astronomy. Thermal noise of dielectric coatings poses a limitation to the sensitivity of ...these interferometers. To decrease coating thermal noise, new crystalline GaAs/AlGaAs multilayer mirrors have been developed. To date, the surface figure and thickness uniformity of these alternative low-loss coatings has not been investigated. Surface figure errors, for example, cause small angle scattering and thereby limit the sensitivity of an interferometer. Here we measure the surface figure of highly reflective, substrate-transferred, crystalline GaAs/AlGaAs coatings with a custom scanning reflectance system. We exploit the fact that the reflectivity varies with the thickness of the coating. To increase penetration into the coating, we used a 1550 nm laser on a highly reflective coating designed for a center wavelength of 1064 nm. The RMS thickness variation of a two inch optic was measured to be 0.41 ± 0.05 nm. This result is within 10% of the thickness uniformity, of 0.37 nm RMS, achieved with ion-beam sputtered coatings for the aLIGO detector. We additionally measured a lower limit of the laser induced damage threshold of 64 MW/cm
for GaAs/AlGaAs coatings at a wavelength of 1064 nm.
Abstract
High precision interferometers such as gravitational-wave detectors require complex seismic isolation systems in order to decouple the experiment from unwanted ground motion. Improved ...inertial sensors for active isolation potentially enhance the sensitivity of existing and future gravitational-wave detectors, especially below 30 Hz, and thereby increase the range of detectable astrophysical signals. This paper presents a vertical inertial sensor which senses the relative motion between an inertial test mass suspended by a blade spring and a seismically isolated platform. An interferometric readout was used which introduces low sensing noise, and preserves a large dynamic range due to fringe-counting. The expected sensitivity is comparable to other state-of-the-art interferometric inertial sensors and reaches values of
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at 1 Hz. The potential sensitivity improvement compared to commercial L-4C geophones is shown to be about two orders of magnitude at 10 mHz and 100 mHz and one order of magnitude at 1 Hz. The noise performance is expected to be limited by thermal noise of the inertial test mass suspension below 10 Hz. Further performance limitations of the sensor, such as tilt-to-vertical coupling from a non-perfect levelling of the test mass and nonlinearities in the interferometric readout, are also quantified and discussed.
High precision measurements in various applications rely on active seismic isolation to decouple the experiment from seismic motion; therefore, closed feed-back control techniques such as sensor ...blending and sensor correction are commonly implemented. This paper reviews the active isolation techniques of the Albert Einstein Institute seismic attenuation system (AEI-SAS). Two approaches to improve the well known techniques are presented. First, the influence of the sensor basis for the signal-to-noise ratio in the chosen coordinate system is calculated and second, a procedural optimization of blending filters to minimize the optical table velocity is performed. Active isolation techniques are adapted to the mechanical properties and the available sensors and actuators of the AEI-SAS. The performance of the final isolation is presented and limitations to the isolation are analyzed in comparison to a noise model. The optical table motion reaches approximately 8 × 1 0 − 10 m / H z at 1 Hz, reducing the ground motion by a factor of approximately 100.
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•Pyrrole-1-carboxylic acid (Py-CO2) was synthesized and applied for modification of pencil graphite electrodes (PGE).•Electropolymerization of Py-CO2 created a sensing film for ...selective metal extraction and determination.•The modified electrode, PPy-CO2@PGE, provided excellent sensitivity and selectivity for detection of Pb2+ and Cd2+.•Accurate analysis of Pb2+ and Cd2+ in several natural water sources was demonstrated and independently verified.
A pencil graphite electrode (PGE) was modified by the electropolymerization of pyrrole-1-carboxylic acid (Py-CO2) to form a sensing film of poly(pyrrole-1-carboxylic acid) (PPy-CO2) for the sensitive determination of Pb2+ and Cd2+ by differential pulse anodic stripping voltammetry (DPASV). The porous structure of the PPy-CO2 film uniformly distributes a carboxylate group throughout the coating to selectively coordinate and preconcentrate metal ions. The polymer film was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), and energy dispersive X-ray (EDS) and Fourier transform infrared (FTIR) spectroscopy. Under the optimized conditions (analyte solution pH: 6.0, extraction time: 15 min, reduction potential: −1.1 V and reduction time: 160 s), a linear relationship between peak current and metal concentration was obtained from 0.1 to 1 nM for Pb2+ and Cd2+ with detection limits of 0.018 and 0.023 nM, respectively. Simultaneous analysis of Pb2+ and Cd2+ was performed in the presence of the possible interfering ions Cr3+, Bi3+, Cu2+, Fe2+, Zn2+ and Co2+ and in complex matrices. The performance of the PPy-CO2@PGE demonstrated excellent intra-day repeatability, long-term reproducibility over a seven-week period and was utilized for the determination of Pb2+ and Cd2+ in a variety of natural water samples with the results independently verified by inductively coupled plasma-mass spectrometry.
A simple and sensitive method for simultaneous microextraction and determination of heavy metals using a new direct immersion solid-phase microextraction (DI–SPME) sorbent material combined with ...inductively coupled plasma mass spectrometry (ICP–MS) was investigated. In this method, sorbent coating composites were prepared by simultaneous electropolymerization of pyrrole on pencil lead in the presence of carbon nanotubes (CNTs) and different metal chelating ligands. Among the coatings evaluated, a polypyrrole coating with entrapped CNTs and the chelator 1, 10 phenanthroline allowed the determination of silver, cadmium, cobalt, iron, nickel, lead, and zinc. Parameters influencing microextraction efficiency including pH, extraction time, and desorption time were optimized. The linear dynamic ranges were 1–1000 μg L−1 for Ag, 1–750 μg L−1 for Cd, Pb, and Zn, and 1–500 μg L−1 for Co, Fe, and Ni with limits of detection of 0.012–0.163 μg L−1 and limits of quantification of 0.039–0.542 μg L−1. The relative standard deviations (RSDs, n = 5) ranged from 1.85% to 5.01%. The effect of inorganic interferences on the determination of the heavy metals also was examined and finally, the method was successfully applied for the determination of heavy metals in real water samples.
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•Low cost selective microextraction fibers easily prepared by electropolymerization.•Simultaneous trace analysis of seven heavy metals was demonstrated.•Entrapped chelating agent determines selectivity for different metals.•Accurate analysis for metals in real water samples using ICP-MS.
The demand for the recovery of valuable metals and the need to understand the impact of heavy metals in the environment on human and aquatic life has led to the development of new methods for the ...extraction, recovery, and analysis of metal ions. With special emphasis on environmentally friendly approaches, efforts have been made to consider strategies that minimize the use of organic solvents, apply micromethodology, limit waste, reduce costs, are safe, and utilize benign or reusable materials. This review discusses recent developments in liquid- and solid-phase extraction techniques. Liquid-based methods include advances in the application of aqueous two- and three-phase systems, liquid membranes, and cloud point extraction. Recent progress in exploiting new sorbent materials for solid-phase extraction (SPE), solid-phase microextraction (SPME), and bulk extractions will also be discussed.
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